Yue Xu

All Publications

• Relationship Between Coronary Atheroma, Epicardial Adipose Tissue Inflammation, and Adipocyte Differentiation Across the Human Myocardial Bridge. Journal of the American Heart Association McLaughlin, T., Schnittger, I., Nagy, A., Zanley, E., Xu, Y., Song, Y., Nieman, K., Tremmel, J. A., Dey, D., Boyd, J., Sacks, H. 2021: e021003

  Abstract

  Background Inflammation in epicardial adipose tissue (EAT) may contribute to coronary atherosclerosis. Myocardial bridge is a congenital anomaly in which the left anterior descending coronary artery takes a "tunneled" course under a bridge of myocardium: while atherosclerosis develops in the proximal left anterior descending coronary artery, the bridged portion is spared, highlighting the possibility that geographic separation from inflamed EAT is protective. We tested the hypothesis that inflammation in EAT was related to atherosclerosis by comparing EAT from proximal and bridge depots in individuals with myocardial bridge and varying degrees of atherosclerotic plaque. Methods and Results Maximal plaque burden was quantified by intravascular ultrasound, and inflammation was quantified by pericoronary EAT signal attenuation (pericoronary adipose tissue attenuation) from cardiac computed tomography scans. EAT overlying the proximal left anterior descending coronary artery and myocardial bridge was harvested for measurement of mRNA and microRNA (miRNA) using custom chips by Nanostring; inflammatory cytokines were measured in tissue culture supernatants. Pericoronary adipose tissue attenuation was increased, indicating inflammation, in proximal versus bridge EAT, in proportion to atherosclerotic plaque. Individuals with moderate-high versus low plaque burden exhibited greater expression of inflammation and hypoxia genes, and lower expression of adipogenesis genes. Comparison of gene expression in proximal versus bridge depots revealed differences only in participants with moderate-high plaque: inflammation was higher in proximal and adipogenesis lower in bridge EAT. Secreted inflammatory cytokines tended to be higher in proximal EAT. Hypoxia-inducible factor 1a was highly associated with inflammatory gene expression. Seven miRNAs were differentially expressed by depot: 3192-5P, 518D-3P, and 532-5P were upregulated in proximal EAT, whereas miR 630, 575, 16-5P, and 320E were upregulated in bridge EAT. miR 630 correlated directly with plaque burden and inversely with adipogenesis genes. miR 3192-5P, 518D-3P, and 532-5P correlated inversely with hypoxia/oxidative stress, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG1a), adipogenesis, and angiogenesis genes. Conclusions Inflammation is specifically elevated in EAT overlying atherosclerotic plaque, suggesting that EAT inflammation is caused by atherogenic molecular signals, including hypoxia-inducible factor 1a and/or miRNAs in an "inside-to-out" relationship. Adipogenesis was suppressed in the bridge EAT, but only in the presence of atherosclerotic plaque, supporting cross talk between the vasculature and EAT. miR 630 in EAT, expressed differentially according to burden of atherosclerotic plaque, and 3 other miRNAs appear to inhibit key genes related to adipogenesis, angiogenesis, hypoxia/oxidative stress, and thermogenesis in EAT, highlighting a role for miRNA in mediating cross talk between the coronary vasculature and EAT.

  View details for DOI 10.1161/JAHA.121.021003

  View details for PubMedID 34726081

• Risk factors and possible mechanisms of saphenous vein graft failure after coronary artery bypass surgery. Chinese medical journal Song, Y., Xu, Y., Guo, Z. 2020

  View details for DOI 10.1097/CM9.0000000000000872

  View details for PubMedID 32568878

• A human lung tumor microenvironment interactome identifies clinically relevant cell-type cross-talk. Genome biology Gentles, A. J., Hui, A. B., Feng, W. n., Azizi, A. n., Nair, R. V., Bouchard, G. n., Knowles, D. A., Yu, A. n., Jeong, Y. n., Bejnood, A. n., Forgó, E. n., Varma, S. n., Xu, Y. n., Kuong, A. n., Nair, V. S., West, R. n., van de Rijn, M. n., Hoang, C. D., Diehn, M. n., Plevritis, S. K. 2020; 21 (1): 107

  Abstract

  Tumors comprise a complex microenvironment of interacting malignant and stromal cell types. Much of our understanding of the tumor microenvironment comes from in vitro studies isolating the interactions between malignant cells and a single stromal cell type, often along a single pathway.To develop a deeper understanding of the interactions between cells within human lung tumors, we perform RNA-seq profiling of flow-sorted malignant cells, endothelial cells, immune cells, fibroblasts, and bulk cells from freshly resected human primary non-small-cell lung tumors. We map the cell-specific differential expression of prognostically associated secreted factors and cell surface genes, and computationally reconstruct cross-talk between these cell types to generate a novel resource called the Lung Tumor Microenvironment Interactome (LTMI). Using this resource, we identify and validate a prognostically unfavorable influence of Gremlin-1 production by fibroblasts on proliferation of malignant lung adenocarcinoma cells. We also find a prognostically favorable association between infiltration of mast cells and less aggressive tumor cell behavior.These results illustrate the utility of the LTMI as a resource for generating hypotheses concerning tumor-microenvironment interactions that may have prognostic and therapeutic relevance.

  View details for DOI 10.1186/s13059-020-02019-x

  View details for PubMedID 32381040

• Overexpression of micro ribonucleic acid-591 inhibits cell proliferation and invasion of malignant pleural mesothelioma cells THORACIC CANCER Cheng, S., Xu, Y., Shi, Z., Lin, Y., Hoang, C. D., Zhang, X. 2016; 7 (3): 340-347

  Abstract

  Malignant pleural mesothelioma (MPM) is an aggressive cancer refractory to current therapies. Reduced expression of micro ribonucleic acid (miR)-591 in a range of cancer types has suggested it is a potent tumor suppressor, and overexpression has been shown to inhibit tumor cell growth. The role of miR-591 in MPM is largely unknown.miR-591 was over-expressed in vitro using micro RNA mimics in three MPM cell lines (H513, H2052, H2373), and effects on tumor cell growth, proliferation, invasion, and target gene expression were assessed.miR-591 mimic was introduced into MPM cell lines to overexpress this microRNA. The cellular growth, proliferation, and invasive capability was significantly inhibited after overexpression of miR-591. Growth inhibition caused by miR-591 correlated with upregulation of p21 and Bax. Reduced invasive capability correlated with downregulation of matrix metalloproteinase-2 and transforming growth factor-β1.miR-591 is a potent tumor suppressor in MPM. Overexpression of miR-591 may represent a novel therapeutic approach for MPM.

  View details for DOI 10.1111/1759-7714.12336

  View details for Web of Science ID 000375234500010

  View details for PubMedID 27148420

  View details for PubMedCentralID PMC4846623

• The prognostic landscape of genes and infiltrating immune cells across human cancers NATURE MEDICINE Gentles, A. J., Newman, A. M., Liu, C. L., Bratman, S. V., Feng, W., Kim, D., Nair, V. S., Xu, Y., Khuong, A., Hoang, C. D., Diehn, M., West, R. B., Plevritis, S. K., Alizadeh, A. A. 2015; 21 (8): 938-945

  Abstract

  Molecular profiles of tumors and tumor-associated cells hold great promise as biomarkers of clinical outcomes. However, existing data sets are fragmented and difficult to analyze systematically. Here we present a pan-cancer resource and meta-analysis of expression signatures from ∼18,000 human tumors with overall survival outcomes across 39 malignancies. By using this resource, we identified a forkhead box MI (FOXM1) regulatory network as a major predictor of adverse outcomes, and we found that expression of favorably prognostic genes, including KLRB1 (encoding CD161), largely reflect tumor-associated leukocytes. By applying CIBERSORT, a computational approach for inferring leukocyte representation in bulk tumor transcriptomes, we identified complex associations between 22 distinct leukocyte subsets and cancer survival. For example, tumor-associated neutrophil and plasma cell signatures emerged as significant but opposite predictors of survival for diverse solid tumors, including breast and lung adenocarcinomas. This resource and associated analytical tools (http://precog.stanford.edu) may help delineate prognostic genes and leukocyte subsets within and across cancers, shed light on the impact of tumor heterogeneity on cancer outcomes, and facilitate the discovery of biomarkers and therapeutic targets.

  View details for DOI 10.1038/nm.3909

  View details for PubMedID 26193342

• Robust enumeration of cell subsets from tissue expression profiles NATURE METHODS Newman, A. M., Liu, C. L., Green, M. R., Gentles, A. J., Feng, W., Xu, Y., Hoang, C. D., Diehn, M., Alizadeh, A. A. 2015; 12 (5): 453-?

  Abstract

  We introduce CIBERSORT, a method for characterizing cell composition of complex tissues from their gene expression profiles. When applied to enumeration of hematopoietic subsets in RNA mixtures from fresh, frozen and fixed tissues, including solid tumors, CIBERSORT outperformed other methods with respect to noise, unknown mixture content and closely related cell types. CIBERSORT should enable large-scale analysis of RNA mixtures for cellular biomarkers and therapeutic targets (http://cibersort.stanford.edu/).

  View details for DOI 10.1038/NMETH.3337

  View details for Web of Science ID 000353645800019

  View details for PubMedID 25822800

• Robust enumeration of cell subsets from tissue expression profiles. Nature methods Newman, A. M., Liu, C. L., Green, M. R., Gentles, A. J., Feng, W., Xu, Y., Hoang, C. D., Diehn, M., Alizadeh, A. A. 2015; 12 (5): 453-457

  Abstract

  We introduce CIBERSORT, a method for characterizing cell composition of complex tissues from their gene expression profiles. When applied to enumeration of hematopoietic subsets in RNA mixtures from fresh, frozen and fixed tissues, including solid tumors, CIBERSORT outperformed other methods with respect to noise, unknown mixture content and closely related cell types. CIBERSORT should enable large-scale analysis of RNA mixtures for cellular biomarkers and therapeutic targets (http://cibersort.stanford.edu/).

  View details for DOI 10.1038/nmeth.3337

  View details for PubMedID 25822800

• A Meta-analysis of Lung Cancer Gene Expression Identifies PTK7 as a Survival Gene in Lung Adenocarcinoma. Cancer research Chen, R., Khatri, P., Mazur, P. K., Polin, M., Zheng, Y., Vaka, D., Hoang, C. D., Shrager, J., Xu, Y., Vicent, S., Butte, A. J., Sweet-Cordero, E. A. 2014; 74 (10): 2892-2902

  Abstract

  Lung cancer remains the most common cause of cancer-related death worldwide and it continues to lack effective treatment. The increasingly large and diverse public databases of lung cancer gene expression constitute a rich source of candidate oncogenic drivers and therapeutic targets. To define novel targets for lung adenocarcinoma, we conducted a large-scale meta-analysis of genes specifically overexpressed in adenocarcinoma. We identified an 11-gene signature that was overexpressed consistently in adenocarcinoma specimens relative to normal lung tissue. Six genes in this signature were specifically overexpressed in adenocarcinoma relative to other subtypes of non-small cell lung cancer (NSCLC). Among these genes was the little studied protein tyrosine kinase PTK7. Immunohistochemical analysis confirmed that PTK7 is highly expressed in primary adenocarcinoma patient samples. RNA interference-mediated attenuation of PTK7 decreased cell viability and increased apoptosis in a subset of adenocarcinoma cell lines. Further, loss of PTK7 activated the MKK7-JNK stress response pathway and impaired tumor growth in xenotransplantation assays. Our work defines PTK7 as a highly and specifically expressed gene in adenocarcinoma and a potential therapeutic target in this subset of NSCLC. Cancer Res; 74(10); 2892-902. ©2014 AACR.

  View details for DOI 10.1158/0008-5472.CAN-13-2775

  View details for PubMedID 24654231

• Response. Chest Xu, Y., Zheng, M., Khuong, A., Merritt, R. E., Shrager, J. B., Wakelee, H. A., Kratzke, R. A., Hoang, C. D. 2013; 144 (6): 1971-1972

  View details for DOI 10.1378/chest.13-1931

  View details for PubMedID 24297135

• miR-1 Induces Growth Arrest and Apoptosis in Malignant Mesothelioma CHEST Xu, Y., Zheng, M., Merritt, R. E., Shrager, J. B., Wakelee, H. A., Kratzke, R. A., Hoang, C. D. 2013; 144 (5): 1632-1643

  Abstract

  We investigated microRNA expression profiles of malignant pleural mesothelioma (MPM) specimens to identify novel microRNA that are potentially involved in the oncogenic transformation of human pleural cells.microRNA microarray transcriptional profiling studies of 25 MPM primary tumors were performed. We used normal pleural from an unmatched patient cohort as normal comparators. To confirm microarray data, we used real-time quantitative PCR. Representative cell lines H513 and H2052 were used in functional analyses of microRNA-1.In addition to several novel MPM-associated microRNAs, we observed that the expression level of microRNA-1 was significantly lower in tumors as compared to normal pleural specimens. Subsequently, pre-mir of microRNA-1 was introduced into MPM cell lines to overexpress this microRNA. Phenotypic changes of these altered cells were assayed. The cellular proliferation rate was significantly inhibited after overexpression of microRNA-1. Early and late apoptosis was increased markedly in microRNA-1-transfected cell lines. Taken together, these data suggested that overexpression of microRNA-1 induced apoptosis in these MPM cell lines, acting as a tumor suppressor. We confirmed our observations by assessing in the transduced MPM cells cell cycle-related genes, pro-apoptotic and anti-apoptotic genes, which all showed coordinated, significant changes characteristic of the apoptotic phenotype.Thus, further investigation and validation of our microRNA database of MPM may elucidate previously unrecognized molecular pathways and/ or mechanisms by identifying novel microRNAs that are involved in malignant transformation. Our study has now found microRNA-1 to be one of these MPM-associated microRNAs, with potential pathogenic and therapeutic significance.

  View details for DOI 10.1378/chest.12-2770

  View details for PubMedID 23828229

• ENERGY METABOLISM IN LUNG ADENOCARCINOMA Hoang, C., Xu, Y., Shi, Z., Lin, Y., Merritt, R. E., Shrager, J., Das, M., Neal, J. W., Wakelee, H. A. LIPPINCOTT WILLIAMS & WILKINS. 2013: S1036–S1037

  View details for Web of Science ID 000339624905063

• Liquid chromatography/mass spectrometry methods for measuring dipeptide abundance in non-small-cell lung cancer. Rapid communications in mass spectrometry : RCM Wu, M., Xu, Y., Fitch, W. L., Zheng, M., Merritt, R. E., Shrager, J. B., Zhang, W., Dill, D. L., Peltz, G., Hoang, C. D. 2013; 27 (18): 2091-2098

  Abstract

  Metabolomic profiling is a promising methodology of identifying candidate biomarkers for disease detection and monitoring. Although lung cancer is among the leading causes of cancer-related mortality worldwide, the lung tumor metabolome has not been fully characterized.We utilized a targeted metabolomic approach to analyze discrete groups of related metabolites. We adopted a dansyl [5-(dimethylamino)-1-naphthalene sulfonamide] derivatization with liquid chromatography/mass spectrometry (LC/MS) to analyze changes of metabolites from paired tumor and normal lung tissues. Identification of dansylated dipeptides was confirmed with synthetic standards. A systematic analysis of retention times was required to reliably identify isobaric dipeptides. We validated our findings in a separate sample cohort.We produced a database of the LC retention times and MS/MS spectra of 361 dansyl dipeptides. Interpretation of the spectra is presented. Using this standard data, we identified a total of 279 dipeptides in lung tumor tissue. The abundance of 90 dipeptides was selectively increased in lung tumor tissue compared to normal tissue. In a second set of validation tissues, 12 dipeptides were selectively increased.A systematic evaluation of certain metabolite classes in lung tumors may identify promising disease-specific metabolites. Our database of all possible dipeptides will facilitate ongoing translational applications of metabolomic profiling as it relates to lung cancer. Copyright © 2013 John Wiley & Sons, Ltd.

  View details for DOI 10.1002/rcm.6656

  View details for PubMedID 23943330

• A Rare Population of CD24(+)ITGB4(+)Notch(hi) Cells Drives Tumor Propagation in NSCLC and Requires Notch3 for Self-Renewal CANCER CELL Zheng, Y., de la Cruz, C. C., Sayles, L. C., Alleyne-Chin, C., Vaka, D., Knaak, T. D., Bigos, M., Xu, Y., Hoang, C. D., Shrager, J. B., Fehling, H. J., French, D., Forrest, W., Jiang, Z., Carano, R. A., Barck, K. H., Jackson, E. L., Sweet-Cordero, E. A. 2013; 24 (1): 59-74

  Abstract

  Sustained tumor progression has been attributed to a distinct population of tumor-propagating cells (TPCs). To identify TPCs relevant to lung cancer pathogenesis, we investigated functional heterogeneity in tumor cells isolated from Kras-driven mouse models of non-small-cell lung cancer (NSCLC). CD24(+)ITGB4(+)Notch(hi) cells are capable of propagating tumor growth in both a clonogenic and an orthotopic serial transplantation assay. While all four Notch receptors mark TPCs, Notch3 plays a nonredundant role in tumor cell propagation in two mouse models and in human NSCLC. The TPC population is enriched after chemotherapy, and the gene signature of mouse TPCs correlates with poor prognosis in human NSCLC. The role of Notch3 in tumor propagation may provide a therapeutic target for NSCLC.

  View details for DOI 10.1016/j.ccr.2013.05.021

  View details for PubMedID 23845442

• Cross-Species Functional Analysis of Cancer-Associated Fibroblasts Identifies a Critical Role for CLCF1 and IL-6 in Non-Small Cell Lung Cancer In Vivo CANCER RESEARCH Vicent, S., Sayles, L. C., Vaka, D., Khatri, P., Gevaert, O., Chen, R., Zheng, Y., Gillespie, A. K., Clarke, N., Xu, Y., Shrager, J., Hoang, C. D., Plevritis, S., Butte, A. J., Sweet-Cordero, E. A. 2012; 72 (22): 5744-5756

  Abstract

  Cancer-associated fibroblasts (CAF) have been reported to support tumor progression by a variety of mechanisms. However, their role in the progression of non-small cell lung cancer (NSCLC) remains poorly defined. In addition, the extent to which specific proteins secreted by CAFs contribute directly to tumor growth is unclear. To study the role of CAFs in NSCLCs, a cross-species functional characterization of mouse and human lung CAFs was conducted. CAFs supported the growth of lung cancer cells in vivo by secretion of soluble factors that directly stimulate the growth of tumor cells. Gene expression analysis comparing normal mouse lung fibroblasts and mouse lung CAFs identified multiple genes that correlate with the CAF phenotype. A gene signature of secreted genes upregulated in CAFs was an independent marker of poor survival in patients with NSCLC. This secreted gene signature was upregulated in normal lung fibroblasts after long-term exposure to tumor cells, showing that lung fibroblasts are "educated" by tumor cells to acquire a CAF-like phenotype. Functional studies identified important roles for CLCF1-CNTFR and interleukin (IL)-6-IL-6R signaling in promoting growth of NSCLCs. This study identifies novel soluble factors contributing to the CAF protumorigenic phenotype in NSCLCs and suggests new avenues for the development of therapeutic strategies.

  View details for DOI 10.1158/0008-5472.CAN-12-1097

  View details for PubMedID 22962265

• Non-Small Cell Lung Cancer: Identifying Prognostic Imaging Biomarkers by Leveraging Public Gene Expression Microarray Data-Methods and Preliminary Results RADIOLOGY Gevaert, O., Xu, J., Hoang, C. D., Leung, A. N., Xu, Y., Quon, A., Rubin, D. L., Napel, S., Plevritis, S. K. 2012; 264 (2): 387-396

  Abstract

  To identify prognostic imaging biomarkers in non-small cell lung cancer (NSCLC) by means of a radiogenomics strategy that integrates gene expression and medical images in patients for whom survival outcomes are not available by leveraging survival data in public gene expression data sets.A radiogenomics strategy for associating image features with clusters of coexpressed genes (metagenes) was defined. First, a radiogenomics correlation map is created for a pairwise association between image features and metagenes. Next, predictive models of metagenes are built in terms of image features by using sparse linear regression. Similarly, predictive models of image features are built in terms of metagenes. Finally, the prognostic significance of the predicted image features are evaluated in a public gene expression data set with survival outcomes. This radiogenomics strategy was applied to a cohort of 26 patients with NSCLC for whom gene expression and 180 image features from computed tomography (CT) and positron emission tomography (PET)/CT were available.There were 243 statistically significant pairwise correlations between image features and metagenes of NSCLC. Metagenes were predicted in terms of image features with an accuracy of 59%-83%. One hundred fourteen of 180 CT image features and the PET standardized uptake value were predicted in terms of metagenes with an accuracy of 65%-86%. When the predicted image features were mapped to a public gene expression data set with survival outcomes, tumor size, edge shape, and sharpness ranked highest for prognostic significance.This radiogenomics strategy for identifying imaging biomarkers may enable a more rapid evaluation of novel imaging modalities, thereby accelerating their translation to personalized medicine.

  View details for DOI 10.1148/radiol.12111607

  View details for PubMedID 22723499

• INTEGRATED ANALYSIS OF MICRO-RNAS AND GENES IN MALIGNANT MESOTHELIOMA Hoang, C. D., Gentles, A., Xu, Y., Plevritis, S., Merritt, R. E., Whyte, R. I., Shrager, J. B., Kratzke, R. A. LIPPINCOTT WILLIAMS & WILKINS. 2011: S483–S484

  View details for Web of Science ID 000208855802216

• Clinically relevant interactions between micro-RNAs and genes in malignant mesothelioma characterized by an integrated analysis Hoang, C. D., Gentles, A., Xu, Y., Plevritis, S. K., Merritt, R., Whyte, R., Shrager, J., Kratzke, R. A. AMER ASSOC CANCER RESEARCH. 2011

  View details for DOI 10.1158/1538-7445.AM2011-1149

  View details for Web of Science ID 000209701404109

• Sonic Hedgehog Influences the Balance of Osteogenesis and Adipogenesis in Mouse Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A James, A. W., Leucht, P., Levi, B., Carre, A. L., Xu, Y., Helms, J. A., Longaker, M. T. 2010; 16 (8): 2605-2616

  Abstract

  Adipose-derived stromal cells (ASCs) present a great potential for tissue engineering, as they are capable of differentiating into osteogenic and adipogenic cell types, among others. In this study, we examined the role of Hedgehog signaling in the balance of osteogenic and adipogenic differentiation in mouse ASCs. Results showed that Hedgehog signaling increased during early osteogenic differentiation (Shh, Ptc1, and Gli1), but decreased during adipogenic differentiation. N-terminal Sonic Hedgehog (Shh-N) significantly increased in vitro osteogenic differentiation in mouse ASCs, by all markers examined (*p < 0.01). Concomitantly, Shh-N abrogated adipogenic differentiation, by all markers examined (*p < 0.01). Conversely, blockade of endogenous Hedgehog signaling, with the Hedgehog antagonist cyclopamine, enhanced adipogenesis at the expense of osteogenesis. We next translated these results to a mouse model of appendicular skeletal regeneration. Using quantitative real-time polymerase chain reaction and in situ hybridization, we found that skeletal injury (a monocortical 1 mm defect in the tibia) results in a localized increase in Hedgehog signaling. Moreover, grafting of ASCs treated with Shh-N resulted in significantly increased bone regeneration within the defect site. In conclusion, Hedgehog signaling enhances the osteogenic differentiation of mouse ASCs, at the expense of adipogenesis. These data suggest that Hedgehog signaling directs the lineage differentiation of mesodermal stem cells and represents a promising strategy for skeletal tissue regeneration.

  View details for DOI 10.1089/ten.tea.2010.0048

  View details for Web of Science ID 000280648700018

  View details for PubMedID 20367246

  View details for PubMedCentralID PMC2947454

• Divergent Modulation of Adipose-Derived Stromal Cell Differentiation by TGF-beta 1 Based on Species of Derivation PLASTIC AND RECONSTRUCTIVE SURGERY Levi, B., James, A. W., Xu, Y., Commons, G. W., Longaker, M. T. 2010; 126 (2): 412-425

  Abstract

  Adipose-derived stromal cells hold promise for skeletal tissue engineering. However, various studies have observed that adipose-derived stromal cells differ significantly in their biology depending on species of derivation. In the following study, the authors sought to determine the species-specific response of adipose-derived stromal cells to recombinant TGF-beta1 (rTGF-beta1).Adipose-derived stromal cells were derived from mouse and human sources. Recombinant TGF-beta1 was added to culture medium (2.5 to 10 ng/ml); proliferation and osteogenic and adipogenic differentiation were assessed by standardized parameters, including cell counting, alkaline phosphatase, alizarin red, oil red O staining, and quantitative real-time polymerase chain reaction.Recombinant TGF-beta1 was found to significantly repress cellular proliferation in both mouse and human adipose-derived stromal cells (p < 0.01). Recombinant TGF-beta1 was found to significantly repress osteogenic differentiation in mouse adipose-derived stromal cells. In contrast, osteogenic differentiation of human adipose-derived stromal cells proceeded unimpeded in either the presence or the absence of rTGF-beta1. Interestingly, rTGF-beta1 induced expression of a number of osteogenic genes in human adipose-derived stromal cells, including BMP2 and BMP4.The authors' results further detail an important facet in which mouse and human adipose-derived stromal cells differ. Mouse adipose-derived stromal cell osteogenesis is completely inhibited by rTGF-beta1, whereas human adipose-derived stromal cell osteogenesis progresses in the presence of rTGF-beta1. These data highlight the importance of species of derivation in basic adipose-derived stromal cell biology. Future studies will examine in more detail the species-specific differences among adipose-derived stromal cell populations.

  View details for DOI 10.1097/PRS.0b013e3181df64dc

  View details for Web of Science ID 000280143800009

  View details for PubMedID 20679827

• Connective Tissue Growth Factor in Regulation of RhoA Mediated Cytoskeletal Tension Associated Osteogenesis of Mouse Adipose-Derived Stromal Cells PLOS ONE Xu, Y., Wagner, D. R., Bekerman, E., Chiou, M., James, A. W., Carter, D., Longaker, M. T. 2010; 5 (6)

  Abstract

  Cytoskeletal tension is an intracellular mechanism through which cells convert a mechanical signal into a biochemical response, including production of cytokines and activation of various signaling pathways.Adipose-derived stromal cells (ASCs) were allowed to spread into large cells by seeding them at a low-density (1,250 cells/cm(2)), which was observed to induce osteogenesis. Conversely, ASCs seeded at a high-density (25,000 cells/cm(2)) featured small cells that promoted adipogenesis. RhoA and actin filaments were altered by changes in cell size. Blocking actin polymerization by Cytochalasin D influenced cytoskeletal tension and differentiation of ASCs. To understand the potential regulatory mechanisms leading to actin cytoskeletal tension, cDNA microarray was performed on large and small ASCs. Connective tissue growth factor (CTGF) was identified as a major regulator of osteogenesis associated with RhoA mediated cytoskeletal tension. Subsequently, knock-down of CTGF by siRNA in ASCs inhibited this osteogenesis.We conclude that CTGF is important in the regulation of cytoskeletal tension mediated ASC osteogenic differentiation.

  View details for DOI 10.1371/journal.pone.0011279

  View details for Web of Science ID 000279135400023

  View details for PubMedID 20585662

  View details for PubMedCentralID PMC2890586

• Retinoic Acid Enhances Osteogenesis in Cranial Suture-Derived Mesenchymal Cells: Potential Mechanisms of Retinoid-Induced Craniosynostosis PLASTIC AND RECONSTRUCTIVE SURGERY James, A. W., Levi, B., Xu, Y., Carre, A. L., Longaker, M. T. 2010; 125 (5): 1352-1361

  Abstract

  In utero retinoid exposure results in numerous craniofacial malformations, including craniosynostosis. Although many malformations associated with retinoic acid syndrome are associated with neural crest defects, the specific mechanisms of retinoid-induced craniosynostosis remain unclear. The authors used the culture of mouse cranial suture-derived mesenchymal cells to probe the potential cellular mechanisms of this teratogen to better elucidate mechanisms of retinoid-induced suture fusion.Genes associated with retinoid signaling were assayed in fusing (posterofrontal) and patent (sagittal, coronal) sutures by quantitative real-time polymerase chain reaction. Cultures of mouse suture-derived mesenchymal cells from the posterofrontal suture were established from 4-day-old mice. Cells were cultured with all-trans retinoic acid (1 and 5 muM). Proliferation, osteogenic differentiation, and specific gene expression were assessed.Mouse sutures were found to express genes necessary for retinoic acid synthesis, binding, and signal transduction, demonstrated by quantitative real-time polymerase chain reaction (Raldh1, Raldh2, Raldh3, and Rbp4). These genes were not found to be differentially expressed in fusing as compared with patent cranial sutures in vivo. Addition of retinoic acid enhanced the osteogenic differentiation of suture-derived mesenchymal cells in vitro, including up-regulation of alkaline phosphatase activity and Runx2 expression. Contemporaneously, cellular proliferation was repressed, as shown by proliferative cell nuclear antigen expression. The pro-osteogenic effect of retinoic acid was accompanied by increased gene expression of several hedgehog and bone morphogenetic protein ligands.Retinoic acid represses proliferation and enhances osteogenic differentiation of suture-derived mesenchymal cells. These in vitro data suggest that retinoid exposure may lead to premature cranial suture fusion by means of enhanced osteogenesis and hedgehog and bone morphogenetic protein signaling.

  View details for DOI 10.1097/PRS.0b013e3181d62980

  View details for Web of Science ID 000276886600007

  View details for PubMedID 20134361

  View details for PubMedCentralID PMC2909493

• Inhibition of Histone Deacetylase Activity in Reduced Oxygen Environment Enhances the Osteogenesis of Mouse Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A Xu, Y., Hammerick, K. E., James, A. W., Carre, A. L., Leucht, P., Giaccia, A. J., Longaker, M. T. 2009; 15 (12): 3697-3707

  Abstract

  Recent studies suggest that oxygen tension has a great impact on the osteogenic differentiation capacity of mesenchymal cells derived from adipose tissue: reduced oxygen impedes osteogenesis. We have found that expansion of mouse adipose-derived stromal cells (mASCs) in reduced oxygen tension (10%) results in increased cell proliferation along with induction of histone deacetylase (HDAC) activity. In this study, we utilized two HDAC inhibitors (HDACi), sodium butyrate (NaB) and valproic acid (VPA), and studied their effects on mASCs expanded in various oxygen tensions (21%, 10%, and 1% O(2)). Significant growth inhibition was observed with NaB or VPA treatment in each oxygen tension. Osteogenesis was enhanced by treatment with NaB or VPA, particularly in reduced oxygen tensions (10% and 1% O(2)). Conversely, adipogenesis was decreased with treatments of NaB or VPA at all oxygen tensions. Finally, NaB- or VPA-treated, reduced oxygen tension-exposed (1% O(2)) ASCs were grafted into surgically created mouse tibial defects and resulted in significantly increased bone regeneration. In conclusion, HDACi significantly promote the osteogenic differentiation of mASCs exposed to reduced oxygen tension; HDACi may hold promise for future clinical applications of ASCs for skeletal regeneration.

  View details for DOI 10.1089/ten.tea.2009.0213

  View details for Web of Science ID 000272528400003

  View details for PubMedID 19505250

  View details for PubMedCentralID PMC2792078

• Estrogen/Estrogen Receptor Alpha Signaling in Mouse Posterofrontal Cranial Suture Fusion PLOS ONE James, A. W., Theologis, A. A., Brugmann, S. A., Xu, Y., Carre, A. L., Leucht, P., Hamilton, K., Korach, K. S., Longaker, M. T. 2009; 4 (9)

  Abstract

  While premature suture fusion, or craniosynostosis, is a relatively common condition, the cause is often unknown. Estrogens are associated with growth plate fusion of endochondral bones. In the following study, we explore the previously unknown significance of estrogen/estrogen receptor signaling in cranial suture biology.Firstly, estrogen receptor (ER) expression was examined in physiologically fusing (posterofrontal) and patent (sagittal) mouse cranial sutures by quantitative RT-PCR. Next, the cranial suture phenotype of ER alpha and ER beta knockout (alphaERKO, betaERKO) mice was studied. Subsequently, mouse suture-derived mesenchymal cells (SMCs) were isolated; the effects of 17-beta estradiol or the estrogen antagonist Fulvestrant on gene expression, osteogenic and chondrogenic differentiation were examined in vitro. Finally, in vivo experiments were performed in which Fulvestrant was administered subcutaneously to the mouse calvaria. Results showed that increased ERalpha but not ERbeta transcript abundance temporally coincided with posterofrontal suture fusion. The alphaERKO but not betaERKO mouse exhibited delayed posterofrontal suture fusion. In vitro, addition of 17-beta estradiol enhanced both osteogenic and chondrogenic differentiation in suture-derived mesenchymal cells, effects reversible by Fulvestrant. Finally, in vivo application of Fulvestrant significantly diminished calvarial osteogenesis, inhibiting suture fusion.Estrogen signaling through ERalpha but not ERbeta is associated with and necessary for normal mouse posterofrontal suture fusion. In vitro studies suggest that estrogens may play a role in osteoblast and/or chondrocyte differentiation within the cranial suture complex.

  View details for DOI 10.1371/journal.pone.0007120

  View details for Web of Science ID 000270154400013

  View details for PubMedID 19771170

  View details for PubMedCentralID PMC2743190

• Differential Effects of TGF-beta 1 and TGF-beta 3 on Chondrogenesis in Posterofrontal Cranial Suture-Derived Mesenchymal Cells In Vitro PLASTIC AND RECONSTRUCTIVE SURGERY James, A. W., Xu, Y., Lee, J. K., Wang, R., Longaker, M. T. 2009; 123 (1): 31-43

  Abstract

  Transforming growth factor (TGF)-beta1 has been associated with cranial suture fusion, whereas TGF-beta3 has been associated with suture patency. The mouse posterofrontal suture, analogous to the human metopic suture, fuses through endochondral ossification.TGF-beta1 and TGF-beta3 expression in the posterofrontal suture was examined by immunohistochemistry. Next, the authors established cultures of suture-derived mesenchymal cells from the posterofrontal suture and examined the cellular responses to TGF-beta1 and TGF-beta3. Proliferation in response to TGF-beta isoforms was examined by bromodeoxyuridine incorporation. High-density micromass culture of posterofrontal mesenchymal cells was used to study the effect of TGF-beta1 and TGF-beta3 on chondrogenic differentiation.TGF-beta1 but not TGF-beta3 protein was highly expressed in chondrocytes within the posterofrontal suture. Significant increases in posterofrontal cell proliferation were observed with TGF-beta3 but not TGF-beta1. TGF-beta1 led to significant increases in chondrogenic-specific gene expression (including Sox9, Col II, Aggrecan, and Col X) as compared with moderate effects of TGF-beta3. TGF-beta1 increased cellular adhesion molecule expression (N-cadherin and fibronectin) and promoted cellular condensation, whereas TGF-beta3 increased cellular proliferation (PCNA expression). Finally, TGF-beta1 and, to a lesser extent, TGF-beta3 induced the expression of fibroblast growth factors (FGF-2 and FGF-18).TGF-beta1 and TGF-beta3 exhibit marked differences in their effects on chondrogenesis in posterfrontal suture-derived mesenchymal cells, influencing different stages of chondrogenic differentiation. TGF-beta3 significantly increased cellular proliferation, whereas TGF-beta1 induced precartilage condensation, promoting chondrocyte differentiation.

  View details for DOI 10.1097/PRS.0b013e3181904c19

  View details for Web of Science ID 000262317700006

  View details for PubMedID 19116522

  View details for PubMedCentralID PMC2748922

• Transforming Growth Factor-beta 1 Stimulates Chondrogenic Differentiation of Posterofrontal Suture-Derived Mesenchymal Cells In Vitro PLASTIC AND RECONSTRUCTIVE SURGERY Xu, Y., James, A. W., Longaker, M. T. 2008; 122 (6): 1649-1659

  Abstract

  Evidence from animal studies has associated transforming growth factor (TGF)-beta signaling with both normal and premature cranial suture fusion. However, the mechanisms whereby this pleiotropic cytokine mediates suture fusion remain uncertain. The authors established cultures of suture-derived mesenchymal cells from normally fusing (posterofrontal) and patent (sagittal) sutures and examined the in vitro effects of TGF-beta1 on these distinct cell populations.Skulls were harvested from 80 5-day-old mice. Posterofrontal and sagittal sutures were dissected, and cultures of suture-derived mesenchymal cells were established. The mitogenic, osteogenic, and chondrogenic effects of recombinant TGF-beta1 were then assessed on posterofrontal and sagittal suture-derived mesenchymal cells (1 to 10 ng/ml). Quantitative real-time polymerase chain reaction was used to examine the effects of TGF-beta1 on gene expression.TGF-beta1 significantly decreased proliferation of both posterofrontal and sagittal suture-derived mesenchymal cells, by bromodeoxyuridine incorporation assays (n = 6). TGF-beta1 also inhibited osteogenesis in both suture-derived mesenchymal cells determined by alkaline phosphatase activity and mineralization (n = 3 for all assays). During chondrogenic differentiation, TGF-beta1 markedly increased expression of chondrocyte-specific gene markers in posterofrontal suture-derived mesenchymal cells (Sox9, Col II, Aggrecan, and Col X) (p

  View details for DOI 10.1097/PRS.0b013e31818cbf44

  View details for Web of Science ID 000263721500006

  View details for PubMedID 19050517

• Proliferation, osteogenic differentiation, and FGF-2 modulation of posterofrontal/sagittal suture-derived mesenchymal cells in vitro PLASTIC AND RECONSTRUCTIVE SURGERY James, A. W., Xu, Y., Wang, R., Longaker, M. T. 2008; 122 (1): 53-63

  Abstract

  Fibroblast growth factor (FGF) signaling is of central importance in premature cranial suture fusion. In the murine skull, the posterofrontal suture normally fuses in early postnatal life, whereas the adjacent sagittal suture remains patent. The authors used a recently developed isolation technique for in vitro culture of suture-derived mesenchymal cells to examine the effects of FGF-2 on proliferation and differentiation of posterofrontal and sagittal suture-derived mesenchymal cells.Skulls were harvested from 40 mice (5-day-old). Posterofrontal and sagittal sutures were dissected, separating sutural mesenchymal tissue from dura mater and pericranium, and cultured. After cell migration from the explant and subculture, differences in proliferation and osteogenic differentiation of these distinct populations were studied. The mitogenic and osteogenic effects of recombinant FGF-2 were then assessed. FGF-2 regulation of gene expression was evaluated.Suture-derived mesenchymal cells isolated from the posterofrontal suture demonstrated significantly higher proliferation rates and a robust mitogenic response to FGF-2 as compared with suture-derived mesenchymal cells isolated from the sagittal suture. Interestingly, posterofrontal suture-derived mesenchymal cells retained a higher in vitro osteogenic potential, as shown by alkaline phosphatase activity and bone nodule formation. FGF-2 significantly diminished osteogenesis in both suture-derived mesenchymal cell populations. Subsequently, Ob-cadherin and Sox9 were found to be differentially expressed in posterofrontal versus sagittal suture-derived mesenchymal cells and dynamically regulated by FGF-2.In vitro osteogenesis of suture-derived mesenchymal cells recapitulates in vivo posterofrontal and sagittal sutural fates. Posterofrontal rather than sagittal suture-derived mesenchymal cells are more responsive to FGF-2 in vitro, in terms of both mitogenesis and osteogenesis.

  View details for DOI 10.1097/PRS.0b013e31817747b5

  View details for Web of Science ID 000257104300006

  View details for PubMedID 18594386

• Molecular and cellular characterization of mouse calvarial osteoblasts derived from neural crest and paraxial mesoderm PLASTIC AND RECONSTRUCTIVE SURGERY Xu, Y., Malladi, P., Zhou, D., Longaker, M. T. 2007; 120 (7): 1783-1795

  Abstract

  Cranial skeletogenic mesenchyme is derived from two distinct embryonic sources: mesoderm and cranial neural crest. Previous studies have focused on molecular and cellular differences of juvenile and adult osteoblasts.To further understand the features of mouse-derived juvenile osteoblasts, the authors separated calvarial osteoblasts by their developmental origins: frontal bone-derived osteoblasts from cranial neural crest, and parietal bone-derived osteoblasts from paraxial mesoderm. Cells were harvested from a total of 120 mice.Interestingly, the authors observed distinct morphologies and proliferation potential of the two populations of osteoblasts. Osteogenic genes such as alkaline phosphatase, osteopontin, collagen I, and Wnt5a, which was recently identified as playing a role in skeletogenesis, were abundantly expressed in parietal bone-derived osteoblasts versus frontal bone-derived osteoblasts. In addition, fibroblast growth factor (FGF) receptor 2, and FGF-18 were more highly expressed in the parietal bone-derived osteoblasts, suggesting a more differentiated phenotype. In contrast, FGF-2, and adhesion molecules osteoblast cadherins and bone morphogenetic protein receptor IB, the bone tissue-specific type receptor were overexpressed in frontal bone-derived osteoblasts compared with parietal bone-derived osteoblasts.The authors observed that although neural crest-derived osteoblasts represented a population of less differentiated, faster growing cells, they formed bone nodules more rapidly than parietal bone-derived osteoblasts. This in vitro study suggests that embryonic tissue derivations influence postnatal in vitro calvarial osteoblast cell biology.

  View details for DOI 10.1097/01.prs.0000279491.48283.51

  View details for Web of Science ID 000251668400005

  View details for PubMedID 18090740

• In vitro expansion of adipose-derived adult stromal cells in hypoxia enhances early chondrogenesis TISSUE ENGINEERING Xu, Y., Malladi, P., Chiou, M., Bekerman, E., Giaccia, A. J., Longaker, M. T. 2007; 13 (12): 2981-2993

  Abstract

  Cartilage is an avascular tissue, and chondrocytes in vivo experience a severely hypoxic environment. Using a defined in vitro model of early chondrogenesis, we attempted to enrich for cells with an enhanced ability for chondrogenic differentiation by pre-exposure of mouse adipose-derived adult stromal cells (ADASs) to a hypoxic (2% oxygen) environment. ADASs were subsequently expanded in 2% or 21% oxygen environments, resulting in 2 groups of cells, and then early chondrogenic differentiation was induced at 21% oxygen tension using a 3-dimensional micromass culture system. ADAS chondrogenesis was assessed using Alcian Blue staining for proteoglycans and quantification of sulfated glycosaminoglycans. Osteogenesis of the 2 cell groups was also studied. Two percent oxygen tension profoundly increased the proliferation of ADASs. ADASs expanded in 2% oxygen tension exhibited enhanced early chondrogenic differentiation and diminished osteogenesis, suggesting that the reduced oxygen environment may favor chondroprogenitors. Gene expression analysis suggested that matrix metalloproteinase synthesis was inhibited in cells expanded in 2% oxygen. Furthermore, re-oxygenation of the 2% oxygen-expanded ADASs before differentiation did not significantly affect early chondrogenesis. Thus, priming ADASs with 2% oxygen may have selected for chondrogenic progenitors with an enhanced ability to survive and differentiate. This study is relevant for the future application of cell-based therapies involving cartilage tissue regeneration.

  View details for DOI 10.1089/ten.2007.0050

  View details for Web of Science ID 000251788400018

  View details for PubMedID 17916040

• Analysis of the material properties of early chondrogenic differentiated adipose-derived stromal cells (ASC) using an in vitro three-dimensional micromass culture system BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Xu, Y., Balooch, G., Chiou, M., Bekerman, E., Ritchie, R. O., Longaker, M. T. 2007; 359 (2): 311-316

  Abstract

  Cartilage is an avascular tissue with only a limited potential to heal and chondrocytes in vitro have poor proliferative capacity. Recently, adipose-derived stromal cells (ASC) have demonstrated a great potential for application to tissue engineering due to their ability to differentiate into cartilage, bone, and fat. In this study, we have utilized a high density three-dimensional (3D) micromass model system of early chondrogenesis with ASC. The material properties of these micromasses showed a significant increase in dynamic and static elastic modulus during the early chondrogenic differentiation process. These data suggest that the 3D micromass culture system represents an in vitro model of early chondrogenesis with dynamic cell signaling interactions associated with the mechanical properties of chondrocyte differentiation.

  View details for DOI 10.1016/j.bbrc.2007.05.098

  View details for Web of Science ID 000247494400020

  View details for PubMedID 17543281

  View details for PubMedCentralID PMC2677915

• Hypoxia inducible factor-1 alpha deficiency affects chondrogenesis of adipose-derived adult stromal cells TISSUE ENGINEERING Malladi, P., Xu, Y., Chiou, M., Giaccia, A. J., Longaker, M. T. 2007; 13 (6): 1159-1171

  Abstract

  Increased cartilage-related disease, poor regeneration of cartilage tissue, and limited treatment options have led to intense research in tissue engineering of cartilage. Adipose-derived adult stromal cells (ADAS) are a promising cell source for skeletal tissue engineering; understanding ADAS cellular signaling and chondrogenesis will advance cell-based therapies in cartilage repair. Chondrocytes are unique-they are continuously challenged by a hypoxic microenvironment. Hypoxia inducible factor-1-alpha (HIF-1alpha), a critical mediator of a cell's response to hypoxia, plays a significant role in chondrocyte survival, growth arrest, and differentiation. By using an established in vitro 3-dimensional micromass system, we investigated the role of HIF-1alpha in chondrogenesis. Targeted deletion of HIF-1alpha in ADAS substantially inhibited the chondrogenic pathway specifically. In marked contrast, deletion of HIF-1alpha did not affect osteogenic differentiation but enhanced adipogenic differentiation. This study demonstrates the critical and specific interplay between HIF-1alpha and chondrogenesis in vitro.

  View details for DOI 10.1089/ten.2006.0265

  View details for Web of Science ID 000247237600003

  View details for PubMedID 17518738

• Isolation and characterization of posterofrontal/sagittal suture mesenchymal cells in vitro PLASTIC AND RECONSTRUCTIVE SURGERY Xu, Y., Malladi, P., Chiou, M., Longaker, M. T. 2007; 119 (3): 819-829

  Abstract

  Craniosynostosis, the premature fusion of cranial sutures, affects one in 2500 children. In the mouse, the posterofrontal suture is programed to fuse postnatally, but the adjacent sagittal suture remains patent throughout life. To study the cellular process of suture fusion, the authors isolated and studied suture-derived mesenchymal cells.Skulls were harvested from 80 mice (2 to 5 days old), and posterofrontal and sagittal sutures were dissected meticulously. Suture mesenchymal tissue was separated from the underlying dura mater and overlying pericranium and cultured in growth media. After the cells migrated from the explant tissues, the morphologies of the two cell populations were studied carefully, and quantitative real-time polymerase chain reaction was performed to evaluate gene expression.Both posterofrontal and sagittal cells exhibited highly heterogeneous morphologies, and the posterofrontal cells migrated faster than the sagittal cells. Accordingly, growth factors such as transforming growth factor-beta1 and fibroblast growth factor (FGF)-2 were expressed significantly more highly in posterofrontal compared with sagittal suture mesenchymal cells. In contrast, FGF receptor 2 and FGF-18 were expressed significantly more in sagittal than in posterofrontal suture cells. Importantly, bone morphogenic protein-3, the only osteogenic inhibitor in the bone morphogenic protein family, and noggin, a bone morphogenic protein antagonist, were expressed significantly more in sagittal than in posterofrontal suture cells, suggesting a possible mechanism of suture patency.To the authors' knowledge, this is the first analysis of mouse suture-derived mesenchymal cells. The authors conclude that isolation of suture-derived mesenchymal cells will provide a useful in vitro system with which to study the mechanisms underlying suture biology.

  View details for DOI 10.1097/01.prs.0000255540.91987.a0

  View details for Web of Science ID 000244438700007

  View details for PubMedID 17312483

• Functions of vitamin D, retinoic acid, and dexamethasone in mouse adipose-derived mesenchymal cells TISSUE ENGINEERING Malladi, P., Xu, Y., Yang, G. P., Longaker, M. T. 2006; 12 (7): 2031-2040

  Abstract

  Adipose-derived mesenchymal cells (AMCs) offer great promise for tissue engineering of bone. Previously, 1,25-dihydroxyvitamin D3, retinoic acid (RA), and dexamethasone had been shown to promote osteogenesis in bone marrow-derived mesenchymal cells (BMSCs). To study the osteogenic characteristics of mouse AMCs, we applied these 3 hormones alone and in combination to the AMCs and examined markers of osteogenic differentiation. Interestingly, vitamin D and RA demonstrated a consistent, dose-dependent enhancement of osteogenesis and upregulated osteoblast specific markers including osteopontin and osteocalcin. However, in AMCs, dexamethasone clearly inhibited osteogenic differentiation in a dose dependent fashion and greatly increased the adipogenic marker peroxisome proliferator activated receptor gamma (PPAgamma). In summary, we show in vitro that vitamin D and RA are potential candidates to serve as enhancers of osteogenesis of AMCs and may be incorporated into future cell-based strategies for bone tissue engineering.

  View details for Web of Science ID 000239571800029

  View details for PubMedID 16889531

• Tissue engineering cartilage with aged articular chondrocytes in vivo PLASTIC AND RECONSTRUCTIVE SURGERY Malladi, P., Xu, Y., Longaker, M. T. 2006; 118 (1): 50-53

  View details for DOI 10.1097/01.prs.0000231940.88501.83

  View details for Web of Science ID 000239048700008

• Mitogenic and chondrogenic effects of fibroblast growth factor-2 in adipose-derived mesenchymal cells BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Chiou, M., Xu, Y., Longaker, M. T. 2006; 343 (2): 644-652

  Abstract

  Adipose-derived mesenchymal cells (AMCs) have demonstrated a great capacity for differentiating into bone, cartilage, and fat. Studies using bone marrow-derived mesenchymal cells (BMSCs) have shown that fibroblast growth factor (FGF)-2, a potent mitogenic factor, plays an important role in tissue engineering due to its effects in proliferation and differentiation for mesenchymal cells. The aim of this study was to investigate the function of FGF-2 in AMC chondrogenic differentiation and its possible contributions to cell-based therapeutics in skeletal tissue regeneration. Data demonstrated that FGF-2 significantly promoted the proliferation of AMCs and enhanced chondrogenesis in three-dimensional micromass culture. Moreover, priming AMCs with treatment of FGF-2 at 10 ng/ml demonstrated that cells underwent chondrogenic phenotypic differentiation, possibly by inducing N-Cadherin, FGF-receptor 2, and transcription factor Sox9. Our results indicated that FGF-2 potentiates chondrogenesis in AMCs, similar to its functions in BMSCs, suggesting the versatile potential applications of FGF-2 in skeletal regeneration and cartilage repair.

  View details for DOI 10.1016/j.bbrc.2006.02.171

  View details for PubMedID 16554022

• Effect of reduced oxygen tension on chondrogenesis and osteogenesis in adipose-derived mesenchymal cells AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Malladi, P., Xu, Y., Chiou, M., Giaccia, A. J., Longaker, M. T. 2006; 290 (4): C1139-C1145

  Abstract

  Recent studies have demonstrated that adipose-derived mesenchymal cells (AMCs) offer great promise for cell-based therapies because of their ability to differentiate toward bone, cartilage, and fat. Given that cartilage is an avascular tissue and that mesenchymal cells experience hypoxia during prechondrogenic condensation in endochondral ossification, the goal of this study was to understand the influence of oxygen tension on AMC differentiation into bone and cartilage. In vitro chondrogenesis was induced using a three-dimensional micromass culture model supplemented with TGF-beta1. Collagen II production and extracellular matrix proteoglycans were assessed with immunohistochemistry and Alcian blue staining, respectively. Strikingly, micromasses differentiated in reduced oxygen tension (2% O(2)) showed markedly decreased chondrogenesis. Osteogenesis was induced using osteogenic medium supplemented with retinoic acid or vitamin D and was assessed with alkaline phosphatase activity and mineralization. AMCs differentiated in both 21 and 2% O(2) environments. However, osteogenesis was severely diminished in a low-oxygen environment. These data demonstrated that hypoxia strongly inhibits in vitro chondrogenesis and osteogenesis in AMCs.

  View details for DOI 10.1152/ajpcell.00415.2005

  View details for PubMedID 16291817

• Adipose-derived mesenchymal cells (AMCs): a promising future for skeletal tissue engineering. Biotechnology & genetic engineering reviews Xu, Y., Malladi, P., Wagner, D. R., Tataria, M., Chiou, M., Sylvester, K. G., Longaker, M. T. 2006; 23: 291-308

  View details for PubMedID 22530513

• Comparative gene and protein expression in primary cultures of epithelial cells from benign prostatic hyperplasia and prostate cancer CANCER LETTERS Rose, A., Xu, Y., Chen, Z. X., Fan, Z. B., Stamey, T. A., McNeal, J. E., Caldwell, M., Peehl, D. M. 2005; 227 (2): 213-222

  Abstract

  Primary cultures are widely used to investigate the disease-specific biology of prostate cancer and benign prostatic hyperplasia (BPH). To identify genes differentially expressed between epithelial cells cultured from adenocarcinomas versus BPH tissues, we used probe array technology. Gene expression profiles were evaluated on Affymetrix Human Cancer G110 Array Chips containing approximately 1900 cancer-related genes. After defined statistical analysis, genes that were over-expressed in cancer cultures were identified. Protein expression of four of the differentially expressed genes was measured in immunoblots, and the expression of two other genes was measured by real-time reverse transcription-polymerase chain reaction (RT-PCR). While no gene or protein was consistently over-expressed in all cancer versus BPH cell cultures, cytokeratin 16 protein was highly elevated in several of the cancer cultures, suggesting that a hyperproliferative phenotype may be characteristic of prostate cancer cells.

  View details for DOI 10.1016/j.canlet.2005.01.037

  View details for PubMedID 16112424

• Adipose-derived mesenchymal cells as a potential cell source for skeletal regeneration CURRENT OPINION IN MOLECULAR THERAPEUTICS Xu, Y., Malladi, P., Wagner, D. R., Longaker, M. T. 2005; 7 (4): 300-305

  Abstract

  Recent studies suggest that adipose tissue contains pluripotent cells that are similar to those derived from other tissues, such as bone marrow. Mesenchymal cells isolated from adipose tissue are capable of differentiating along osteogenic, chondrogenic, myogenic, adipogenic and possibly neuronal lineages. Current knowledge of adipose-derived mesenchymal cells is reviewed, with a particular focus on efforts to direct these cells towards bone formation. Cell-based therapies using adipose tissue are anticipated to be of great clinical interest for skeletal tissue repair and regeneration.

  View details for PubMedID 16121695

• Altered SMRT levels disrupt vitamin D-3 receptor signalling in prostate cancer cells ONCOGENE Khanim, F. L., Gommersall, L. M., Wood, V. H., Smith, K. L., Montalvo, L., O'Neill, L. P., Xu, Y., Peehl, D. M., Stewart, P. M., Turner, B. M., Campbell, M. J. 2004; 23 (40): 6712-6725

  Abstract

  We hypothesized that key antiproliferative target genes for the vitamin D receptor (VDR) were repressed by an epigenetic mechanism in prostate cancer cells resulting in apparent hormonal insensitivity. To explore this possibility, we examined nuclear receptor corepressor expression in a panel of nonmalignant and malignant cell lines and primary cultures, and found frequently elevated SMRT corepressor mRNA expression often associated with reduced sensitivity to 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)2D3). For example, PC-3 and DU-145 prostate cancer cell lines had 1.8-fold and twofold increases in SMRT mRNA relative to normal PrEC cells (P<0.05). Similarly, 10/15 primary tumour cultures (including three matched to normal cells from the same donors) had elevated SMRT mRNA levels; generally NCoR1 and Alien were not as commonly elevated. Corepressor proteins often have associated histone deacetylases (HDAC) and reflectively the antiproliferative action of 1alpha,25(OH)2D3 can be 'restored' by cotreatment with low doses of HDAC inhibitors such as trichostatin A (TSA, 15 nM) to induce apoptosis in prostate cancer cell lines. To decipher the transcriptional events that lead to these cellular responses, we undertook gene expression studies in PC-3 cells after cotreatment of 1alpha,25(OH)2D3 plus TSA after 6 h. Examination of known VDR target genes and cDNA microarray analyses revealed cotreatment of 1alpha,25(OH)2D3 plus TSA cooperatively upregulated eight (out of 1176) genes, including MAPK-APK2 and GADD45alpha. MRNA and protein time courses and inhibitor studies confirmed these patterns of regulation. Subsequently, we knocked down SMRT levels in PC-3 cells using a small interfering RNA (siRNA) approach and found that GADD45alpha induction by 1alpha,25(OH)2D3 alone became very significantly enhanced. The same distortion of gene responsiveness, with repressed induction of GADD45alpha was found in primary tumour cultures compared and to matched peripheral zone (normal) cultures from the same donor. These data demonstrate that elevated SMRT levels are common in prostate cancer cells, resulting in suppression of target genes associated with antiproliferative action and apparent 1alpha,25(OH)2D3-insensitivity. This can be targeted therapeutically by combination treatments with HDAC inhibitors.

  View details for DOI 10.1038/sj.onc.1207772

  View details for Web of Science ID 000223653600003

  View details for PubMedID 15300237

• Primary culture model of peroxisome proliferator-activated receptor gamma activity in prostate cancer cells JOURNAL OF CELLULAR PHYSIOLOGY Xu, Y., Iyengar, S., Roberts, R. L., Shappell, S. B., Peehl, D. M. 2003; 196 (1): 131-143

  Abstract

  BRL 49653 (rosiglitazone) is a thiazolidinedione anti-diabetic drug that activates the nuclear receptor, peroxisome proliferator-activated receptor gamma (PPARgamma). Pilot clinical trials have shown evidence of therapeutic activity of PPARgamma agonists against prostate cancer. To more effectively use PPARgamma ligands to treat this common and generally chemo-resistant type of cancer, it will be necessary to better understand the nature of PPARgamma activity in prostate cancer cells. Tumor suppressor effects of activation of PPARgamma may include suppression of growth and/or induction of differentiation or apoptosis. We investigated responses of primary cultures of human prostatic cancer cells to BRL 49653. PPARgamma was expressed in all of the cell strains examined. BRL 49653 caused dose- and time-dependent growth inhibition that was associated with increased expression of the transcription repressor, transforming growth factor beta-stimulated clone 22 (TSC-22), and markedly increased expression of the secretory differentiation-associated gene adipophilin. Adipocyte-type fatty acid binding protein (aFABP), neutrophil gelatinase-associated lipocalin (NGAL), glycerol kinase (GyK), and beta-catenin, which are regulated by PPARgamma ligands in certain other types of cells, were not regulated by BRL 49653 in prostate cells. Upregulation of adipophilin coincided with morphological changes and the appearance of cytoplasmic vacuoles with ultrastructural features of secondary lysosomes. These results extend previous studies with established cancer cell lines and show that PPARgamma agonists can inhibit proliferation and modulate expression of secretory-associated genes in primary cultures of prostate cancer cells, further warranting consideration of these agents as pro-differentiating chemotherapeutic or chemoprevention agents for the treatment of prostate cancer.

  View details for DOI 10.1002/jcp.10281

  View details for PubMedID 12767049

• Vitamin D receptor start codon polymorphism (FokI) and prostate cancer progression CANCER EPIDEMIOLOGY BIOMARKERS & PREVENTION Xu, Y., Shibata, A., McNeal, J. E., Stamey, T. A., Feldman, D., Peehl, D. M. 2003; 12 (1): 23-27

  Abstract

  Vitamin D plays an important role in cell growth and differentiation and is proposed to protect against cancer initiation and/or progression. The vitamin D receptor (VDR) has a thymine/cytosine (T/C) polymorphism located in the first of two potential start (ATG) codons that can be detected by a RFLP using the endonuclease FokI. The C variant, which lacks the first ATG, results in a shorter VDR and is referred to as the F allele. The T variant (f allele) initiates at the first ATG. We examined the association of the VDR FokI genotype with histopathological characteristics and prognosis of prostate cancer among 191 mostly Caucasian subjects who had undergone radical prostatectomy between 1984 and 1992. The frequencies of the FF, Ff, and ff genotypes were 41%, 38%, and 21%, respectively. Subjects with the ff genotype had a lower mean percentage of Gleason grade 4/5 cancer (30.3%) than subjects with the FF or Ff genotypes (42.8% and 43.8%, respectively; P = 0.015 by t test for ff versus FF + Ff). The data suggest that the presence of an F allele increased the risk of being diagnosed with more aggressive cancer because higher percentage of Gleason grade 4/5 is associated with worse prognosis. The age-adjusted risk of prostate-specific antigen failure was lower for the ff genotype than for the FF genotype by Cox proportional hazards analysis but did not achieve statistical significance (hazard ratio = 0.76; 95% confidence interval, 0.44-1.32). This risk reduction disappeared after further adjustment for percentage of Gleason grade 4/5, cancer volume, and preoperative serum prostate-specific antigen level (hazard ratio = 1.03; 95% confidence interval, 0.58-1.85). In conclusion, the ff genotype was associated with less aggressive histopathological findings than Ff or FF genotypes. Additional studies with a larger sample size and investigation of the functional significance of the FokI polymorphism in prostate cancer cells are warranted.

  View details for PubMedID 12540499

• Rapid and selective selenium-mediated autoligation of DNA strands JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Xu, Y. Z., Kool, E. T. 2000; 122 (37): 9040-9041

  View details for Web of Science ID 000089453800033

• OBSERVATION OF COULOMB CORRELATIONS OF RESONANT TUNNELING AND INELASTIC HOPPING PHYSICAL REVIEW LETTERS EPHRON, D., Xu, Y., Beasley, M. R. 1992; 69 (21): 3112-3115

  View details for Web of Science ID A1992JY87900029