Assistant Professor (Research), Pediatrics - Pulmonary Medicine
Member, Cardiovascular Institute
Honors & Awards
The Esther Ehrman Lazard Faculty Scholar, Stanford University (2023)
Independent Studies (5)
- Directed Reading in Pediatrics
PEDS 299 (Aut)
- Graduate Research
PEDS 399 (Aut)
HUMBIO 194 (Spr)
- Research in Human Biology
HUMBIO 193 (Aut, Win)
- Undergraduate Directed Reading/Research
PEDS 199 (Aut, Spr)
- Directed Reading in Pediatrics
von Willebrand Factor Is Produced Exclusively by Endothelium, Not Neointima, in Occlusive Vascular Lesions in Both Pulmonary Hypertension and Atherosclerosis.
2022; 146 (5): 429-431
View details for DOI 10.1161/CIRCULATIONAHA.121.058427
View details for PubMedID 35914017
The Tabula Sapiens: A multiple-organ, single-cell transcriptomic atlas of humans.
Science (New York, N.Y.)
2022; 376 (6594): eabl4896
Molecular characterization of cell types using single-cell transcriptome sequencing is revolutionizing cell biology and enabling new insights into the physiology of human organs. We created a human reference atlas comprising nearly 500,000 cells from 24 different tissues and organs, many from the same donor. This atlas enabled molecular characterization of more than 400 cell types, their distribution across tissues, and tissue-specific variation in gene expression. Using multiple tissues from a single donor enabled identification of the clonal distribution of T cells between tissues, identification of the tissue-specific mutation rate in B cells, and analysis of the cell cycle state and proliferative potential of shared cell types across tissues. Cell type-specific RNA splicing was discovered and analyzed across tissues within an individual.
View details for DOI 10.1126/science.abl4896
View details for PubMedID 35549404
Shunt-type plexiform lesions identified in the Sugen5416/Hypoxia rat model of pulmonary arterial hypertension using SPCT.
The European respiratory journal
View details for DOI 10.1183/13993003.02802-2021
View details for PubMedID 35332070
Molecular hallmarks of heterochronic parabiosis at single-cell resolution.
The ability to slow or reverse biological ageing would have major implications for mitigating disease risk and maintaining vitality1. Although an increasing number of interventions show promise for rejuvenation2, their effectiveness on disparate cell types across the body and the molecular pathways susceptible to rejuvenation remain largely unexplored. Here we performed single-cell RNA sequencing on 20 organs to reveal cell-type-specific responses to young and aged blood in heterochronic parabiosis. Adipose mesenchymal stromal cells, haematopoietic stem cells and hepatocytes are among those cell types that are especially responsive. On the pathway level, young blood invokes new gene sets in addition to reversing established ageing patterns, with the global rescue of genes encoding electron transport chain subunits pinpointing a prominent role of mitochondrial function in parabiosis-mediated rejuvenation. We observed an almost universal loss of gene expression with age that is largely mimicked by parabiosis: aged blood reduces global gene expression, and young blood restores it in select cell types. Together, these data lay the groundwork for a systemic understanding of the interplay between blood-borne factors and cellular integrity.
View details for DOI 10.1038/s41586-022-04461-2
View details for PubMedID 35236985
Cell types of origin of the cell-free transcriptome.
Cell-free RNA from liquid biopsies can be analyzed to determine disease tissue of origin. We extend this concept to identify cell types of origin using the Tabula Sapiens transcriptomic cell atlas as well as individual tissue transcriptomic cell atlases in combination with the Human Protein Atlas RNA consensus dataset. We define cell type signature scores, which allow the inference of cell types that contribute to cell-free RNA for a variety of diseases.
View details for DOI 10.1038/s41587-021-01188-9
View details for PubMedID 35132263
Chronic Daily House Dust Mite Exposure in Mice is an Effective Model to Quantify the Effect of Pharmacologic Agents on Discrete Stages of Artery Remodeling in Pulmonary Hypertension.
2022; 12 (1): e4273
Pulmonary hypertension (PH) is a heterogenous and incurable disease marked by varying degrees of pulmonary vascular remodeling. This vascular remodeling, which includes thickening of the smooth muscle layer (an early finding) and formation of occlusive neointimal lesions (a late finding) in the pulmonary arteries, is a major driver of morbidity and mortality in PH. Available PH therapies consist of vasodilators that do not specifically target lesion formation or expansion and neither prevent progression nor reverse disease. This paucity of curative treatments highlights the need for new drug discovery targeting crucial steps of artery remodeling in PH. The cell dynamics and molecular signals driving neointimal lesion formation have been difficult to elucidate as classic mouse models of PH do not develop neointima. Here, we detail the methods to generate a robust and non-genetic mouse model of PH with medial thickening and neointimal lesion formation in the pulmonary arteries, through chronic exposure to an inflammatory stimulus-house dust mite (HDM). This model rapidly generates human-like pulmonary arterial lesions following a reproducible time course, allowing scrutiny of the cellular and molecular mechanisms controlling each stage of artery remodeling. Further, we outline optimal tissue handling, sectioning, and staining methodologies for detailed quantitative analysis of artery medial thickening and neointimal lesion formation and expansion. Finally, we present a method for staged pharmacologic intervention to identify molecules and pathways required at each step of the pulmonary arterial remodeling process. The advantages of this mouse model of PH over currently available animal models are five-fold. (i) It allows the use of the full range of genetic and single cell tools available in mice to manipulate and study the process of vascular remodeling seen in human disease, including the formation of neointimal lesions in a controlled and cell specific manner. (ii) The vascular lesions develop in a stereotyped manner with predictable timing, allowing for pharmacologic manipulation at discrete stages of vessel remodeling. (iii) It is rapid, with development of PH and vascular remodeling in a timeframe of two to eight weeks. (iv) It uses simple techniques and requires neither surgery, unusual equipment, or extensive personnel training. (v) The staining and quantitation methodologies we present are a significant improvement over those currently in use in the field. We hope that dissemination of this model and the associated detailed methods will speed up the development of novel and more effective PH therapeutics. Graphic abstract: Chronic perivascular inflammation induces medial thickening and neointima formation in pulmonary arteries, following a stereotyped time course, and allowing staged pharmacologic intervention during specific remodeling events, as well as quantitative assessment of vascular changes.
View details for DOI 10.21769/BioProtoc.4273
View details for PubMedID 35118166
View details for PubMedCentralID PMC8769763
RNA splicing programs define tissue compartments and cell types at single-cell resolution
View details for DOI 10.7554/eLife.70692.sa2
View details for Web of Science ID 000715795700001
Ageing hallmarks exhibit organ-specific temporal signatures.
Ageing is the single greatest cause of disease and death worldwide, and understanding the associated processes could vastly improve quality of life. Although major categories of ageing damage have been identified-such as altered intercellular communication, loss of proteostasis and eroded mitochondrial function1-these deleterious processes interact with extraordinary complexity within and between organs, and a comprehensive, whole-organism analysis of ageing dynamics has been lacking. Here we performed bulk RNA sequencing of 17 organs and plasma proteomics at 10 ages across the lifespan of Mus musculus, and integrated these findings with data from the accompanying Tabula Muris Senis2-or 'Mouse Ageing Cell Atlas'-which follows on from the original Tabula Muris3. We reveal linear and nonlinear shifts in gene expression during ageing, with the associated genes clustered in consistent trajectory groups with coherent biological functions-including extracellular matrix regulation, unfolded protein binding, mitochondrial function, and inflammatory and immune response. Notably, these gene sets show similar expression across tissues, differing only in the amplitude and the age of onset of expression. Widespread activation of immune cells is especially pronounced, and is first detectable in white adipose depots during middle age. Single-cell RNA sequencing confirms the accumulation of T cells and B cells in adipose tissue-including plasma cells that express immunoglobulin J-which also accrue concurrently across diverse organs. Finally, we show how gene expression shifts in distinct tissues are highly correlated with corresponding protein levels in plasma, thus potentially contributing to the ageing of the systemic circulation. Together, these data demonstrate a similar yet asynchronous inter- and intra-organ progression of ageing, providing a foundation from which to track systemic sources of declining health at old age.
View details for DOI 10.1038/s41586-020-2499-y
View details for PubMedID 32669715
A Notch3-Marked Subpopulation of Vascular Smooth Muscle Cells is the Cell of Origin for Occlusive Pulmonary Vascular Lesions.
Background: Pulmonary arterial hypertension (PAH) is a fatal disease characterized by profound vascular remodeling in which pulmonary arteries narrow due to medial thickening and occlusion by neointimal lesions, resulting in elevated pulmonary vascular resistance and right heart failure. Therapies targeting the neointima would represent a significant advance in PAH treatment, however our understanding of the cellular events driving neointima formation, and the molecular pathways that control them, remains limited. Methods: We comprehensively map the stepwise remodeling of pulmonary arteries in a robust, chronic inflammatory mouse model of pulmonary hypertension. This model demonstrates pathologic features of the human disease, including increased right ventricular pressures, medial thickening, neointimal lesion formation, elastin breakdown, increased anastomosis within the bronchial circulation, and perivascular inflammation. Using genetic lineage tracing, clonal analysis, multiplexed in situ hybridization, immunostaining, deep confocal imaging and staged pharmacologic inhibition we define the cell behaviors underlying each stage of vascular remodeling and identify a pathway required for neointima formation. Results: Neointima arises from smooth muscle cells (SMCs) and not endothelium. Medial SMCs proliferate broadly to thicken the media, after which a small number of SMCs are selected to establish the neointima. These neointimal founder cells subsequently undergoing massive clonal expansion to form occlusive neointimal lesions. The normal pulmonary artery SMC population is heterogeneous and we identify a Notch3-marked minority subset of SMCs as the major neointimal cell of origin. Notch signaling is specifically required for the selection of neointimal founder cells, and Notch inhibition significantly improves pulmonary artery pressure in animals with pulmonary hypertension. Conclusions: This work describes the first nongenetically driven murine model of PH that generates robust and diffuse occlusive neointimal lesions across the pulmonary vascular bed and does so in a stereotyped timeframe. We uncover distinct cellular and molecular mechanisms underlying medial thickening and neointima formation and highlight novel transcriptional, behavioral and pathogenic heterogeneity within pulmonary artery SMCs. In this model, inflammation is sufficient to generate characteristic vascular pathologies and physiologic measures of human PAH. We hope that identifying the molecular cues regulating each stage of vascular remodeling will open new avenues for therapeutic advancements in the treatment of PAH.
View details for DOI 10.1161/CIRCULATIONAHA.120.045750
View details for PubMedID 32794408
A single-cell transcriptomic atlas characterizes ageing tissues in the mouse.
Ageing is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death1. Despite rapid advances over recent years, many of the molecular and cellular processes that underlie the progressive loss of healthy physiology are poorly understood2. To gain a better insight into these processes, here we generate a single-cell transcriptomic atlas across the lifespan of Mus musculus that includes data from 23 tissues and organs. We found cell-specific changes occurring across multiple cell types and organs, as well as age-related changes in the cellular composition of different organs. Using single-cell transcriptomic data, we assessed cell-type-specific manifestations of different hallmarks of ageing-such as senescence3, genomic instability4 and changes in the immune system2. This transcriptomic atlas-which we denote Tabula Muris Senis, or 'Mouse Ageing Cell Atlas'-provides molecular information about how the most important hallmarks of ageing are reflected in a broad range of tissues and cell types.
View details for DOI 10.1038/s41586-020-2496-1
View details for PubMedID 32669714
Single-cell transcriptomics of 20 mouse organs creates a Tabula Muris.
2018; 562 (7727): 367–72
Here we present a compendium of single-cell transcriptomic data from the model organism Mus musculus that comprises more than 100,000 cells from 20 organs and tissues. These data represent a new resource for cell biology, reveal gene expression in poorly characterized cell populations and enable the direct and controlled comparison of gene expression in cell types that are shared between tissues, such as T lymphocytes and endothelial cells from different anatomical locations. Two distinct technical approaches were used for most organs: one approach, microfluidic droplet-based 3'-end counting, enabled the survey of thousands of cells at relatively low coverage, whereas the other, full-length transcript analysis based on fluorescence-activated cell sorting, enabled the characterization of cell types with high sensitivity and coverage. The cumulative data provide the foundation for an atlas of transcriptomic cell biology.
View details for DOI 10.1038/s41586-018-0590-4
View details for PubMedID 30283141
Transcription factor TBX4 regulates myofibroblast accumulation and lung fibrosis
JOURNAL OF CLINICAL INVESTIGATION
2016; 126 (8): 3063-3079
Progressive tissue fibrosis is a major cause of the morbidity and mortality associated with repeated epithelial injuries and accumulation of myofibroblasts. Successful treatment options are limited by an incomplete understanding of the molecular mechanisms that regulate myofibroblast accumulation. Here, we employed in vivo lineage tracing and real-time gene expression transgenic reporting methods to analyze the early embryonic transcription factor T-box gene 4 (TBX4), and determined that TBX4-lineage mesenchymal progenitors are the predominant source of myofibroblasts in injured adult lung. In a murine model, ablation of TBX4-expressing cells or disruption of TBX4 signaling attenuated lung fibrosis after bleomycin-induced injury. Furthermore, TBX4 regulated hyaluronan synthase 2 production to enable fibroblast invasion of matrix both in murine models and in fibroblasts from patients with severe pulmonary fibrosis. These data identify TBX4 as a mesenchymal transcription factor that drives accumulation of myofibroblasts and the development of lung fibrosis. Targeting TBX4 and downstream factors that regulate fibroblast invasiveness could lead to therapeutic approaches in lung fibrosis.
View details for DOI 10.1172/JCI85328
View details for Web of Science ID 000381943000027
View details for PubMedID 27400124
View details for PubMedCentralID PMC4966327
Defining a mesenchymal progenitor niche at single-cell resolution
2014; 346 (6211): 827-?
Most vertebrate organs are composed of epithelium surrounded by support and stromal tissues formed from mesenchyme cells, which are not generally thought to form organized progenitor pools. Here, we use clonal cell labeling with multicolor reporters to characterize individual mesenchymal progenitors in the developing mouse lung. We observe a diversity of mesenchymal progenitor populations with different locations, movements, and lineage boundaries. Airway smooth muscle (ASM) progenitors map exclusively to mesenchyme ahead of budding airways. Progenitors recruited from these tip pools differentiate into ASM around airway stalks; flanking stalk mesenchyme can be induced to form an ASM niche by a lateral bud or by an airway tip plus focal Wnt signal. Thus, mesenchymal progenitors can be organized into localized and carefully controlled domains that rival epithelial progenitor niches in regulatory sophistication.
View details for DOI 10.1126/science.1258810
View details for Web of Science ID 000349771600003
View details for PubMedCentralID PMC4269943
miR-142-3p balances proliferation and differentiation of mesenchymal cells during lung development
2014; 141 (6): 1272–U180
The regulation of the balance between proliferation and differentiation in the mesenchymal compartment of the lung is largely uncharacterized, unlike its epithelial counterpart. In this study, we determined that miR-142-3p contributes to the proper proliferation of mesenchymal progenitors by controlling the level of WNT signaling. miR-142-3p can physically bind to adenomatous polyposis coli mRNA, functioning to regulate its expression level. In miR-142-3p loss-of-function experiments, proliferation of parabronchial smooth muscle cell progenitors is significantly impaired, leading to premature differentiation. Activation of WNT signaling in the mesenchyme, or Apc loss of function, can both rescue miR-142-3p knockdown. These findings show that in the embryonic lung mesenchyme, the microRNA machinery modulates the level of WNT signaling, adding an extra layer of control in the feedback loop between FGFR2C and β-catenin-mediated WNT signaling.
View details for DOI 10.1242/dev.105908
View details for Web of Science ID 000332535400011
View details for PubMedID 24553287
View details for PubMedCentralID PMC3943182
Molecular determinants of lung development.
Annals of the American Thoracic Society
2013; 10 (2): S12-6
Development of the pulmonary system is essential for terrestrial life. The molecular pathways that regulate this complex process are beginning to be defined, and such knowledge is critical to our understanding of congenital and acquired lung diseases. A recent workshop was convened by the National Heart, Lung, and Blood Institute to discuss the developmental principles that regulate the formation of the pulmonary system. Emerging evidence suggests that key developmental pathways not only regulate proper formation of the pulmonary system but are also reactivated upon postnatal injury and repair and in the pathogenesis of human lung diseases. Molecular understanding of early lung development has also led to new advances in areas such as generation of lung epithelium from pluripotent stem cells. The workshop was organized into four different topics, including early lung cell fate and morphogenesis, mechanisms of lung cell differentiation, tissue interactions in lung development, and environmental impact on early lung development. Critical points were raised, including the importance of epigenetic regulation of lung gene expression, the dearth of knowledge on important mesenchymal lineages within the lung, and the interaction between the developing pulmonary and cardiovascular system. This manuscript describes the summary of the discussion along with general recommendations to overcome the gaps in knowledge in lung developmental biology.
View details for DOI 10.1513/AnnalsATS.201207-036OT
View details for PubMedID 23607856
Radial Construction of an Arterial Wall
2012; 23 (3): 482-493
Some of the most serious diseases involve altered size and structure of the arterial wall. Elucidating how arterial walls are built could aid understanding of these diseases, but little is known about how concentric layers of muscle cells and the outer adventitial layer are assembled and patterned around endothelial tubes. Using histochemical, clonal, and genetic analysis in mice, here we show that the pulmonary artery wall is constructed radially, from the inside out, by two separate but coordinated processes. One is sequential induction of successive cell layers from surrounding mesenchyme. The other is controlled invasion of outer layers by inner layer cells through developmentally regulated cell reorientation and radial migration. We propose that a radial signal gradient controls these processes and provide evidence that PDGF-B and at least one other signal contribute. Modulation of such radial signaling pathways may underlie vessel-specific differences and pathological changes in arterial wall size and structure.
View details for DOI 10.1016/j.devcel.2012.07.009
View details for Web of Science ID 000308776400007
View details for PubMedID 22975322
View details for PubMedCentralID PMC3500096