Honors & Awards
Postdoctoral Fellowship Award, AHA (2018-2020)
Bachelor of Engineering, Huazhong University Of Science & Technology (2007)
Bachelor of Science, Wuhan University, Biological Science (2007)
Master of Science, Fudan University, Macromolecular Science (2010)
Doctor of Philosophy, Clemson University (2015)
Joseph Wu, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
Cardiac tissue engineering with iPSC derived cardiovascular cells
An in Vivo miRNA Delivery System for Restoring Infarcted Myocardium.
A major challenge in myocardial infarction (MI)-related heart failure treatment using microRNA is the efficient and sustainable delivery of miRNAs into myocardium to achieve functional improvement through stimulation of intrinsic myocardial restoration. In this study, we established an in vivo delivery system using polymeric nanoparticles to carry miRNA (miNPs) for localized delivery within a shear-thinning injectable hydrogel. The miNPs triggered proliferation of human embryonic stem cell-derived cardiomyocytes and endothelial cells (hESC-CMs and hESC-ECs) and promoted angiogenesis in hypoxic conditions, showing significantly lower cytotoxicity than Lipofectamine. Furthermore, one injected dose of hydrogel/miNP in MI rats demonstrated significantly improved cardiac functions: increased ejection fraction from 45% to 64%, reduced scar size from 20% to 10%, and doubled capillary density in the border zone compared to the control group at 4 weeks. As such, our results indicate that this injectable hydrogel/miNP composite can deliver miRNA to restore injured myocardium efficiently and safely.
View details for DOI 10.1021/acsnano.9b03343
View details for PubMedID 31149806
Modelling diastolic dysfunction in induced pluripotent stem cell-derived cardiomyocytes from hypertrophic cardiomyopathy patients.
European heart journal
Diastolic dysfunction (DD) is common among hypertrophic cardiomyopathy (HCM) patients, causing major morbidity and mortality. However, its cellular mechanisms are not fully understood, and presently there is no effective treatment. Patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold great potential for investigating the mechanisms underlying DD in HCM and as a platform for drug discovery.In the present study, beating iPSC-CMs were generated from healthy controls and HCM patients with DD. Micropatterned iPSC-CMs from HCM patients showed impaired diastolic function, as evidenced by prolonged relaxation time, decreased relaxation rate, and shortened diastolic sarcomere length. Ratiometric Ca2+ imaging indicated elevated diastolic [Ca2+]i and abnormal Ca2+ handling in HCM iPSC-CMs, which were exacerbated by β-adrenergic challenge. Combining Ca2+ imaging and traction force microscopy, we observed enhanced myofilament Ca2+ sensitivity (measured as dF/Δ[Ca2+]i) in HCM iPSC-CMs. These results were confirmed with genome-edited isogenic iPSC lines that carry HCM mutations, indicating that cytosolic diastolic Ca2+ overload, slowed [Ca2+]i recycling, and increased myofilament Ca2+ sensitivity, collectively impairing the relaxation of HCM iPSC-CMs. Treatment with partial blockade of Ca2+ or late Na+ current reset diastolic Ca2+ homeostasis, restored diastolic function, and improved long-term survival, suggesting that disturbed Ca2+ signalling is an important cellular pathological mechanism of DD. Further investigation showed increased expression of L-type Ca2+channel (LTCC) and transient receptor potential cation channels (TRPC) in HCM iPSC-CMs compared with control iPSC-CMs, which likely contributed to diastolic [Ca2+]i overload.In summary, this study recapitulated DD in HCM at the single-cell level, and revealed novel cellular mechanisms and potential therapeutic targets of DD using iPSC-CMs.
View details for DOI 10.1093/eurheartj/ehz326
View details for PubMedID 31219556
A Premature Termination Codon Mutation in MYBPC3 Causes Hypertrophic Cardiomyopathy via Chronic Activation of Nonsense-Mediated Decay.
BACKGROUND: Hypertrophic cardiomyopathy (HCM) is frequently caused by mutations in myosin binding protein C3 ( MYBPC3) resulting in a premature termination codon (PTC). The underlying mechanisms of how PTC mutations in MYBPC3 lead to the onset and progression of HCM are poorly understood. This study's aim was to investigate the molecular mechanisms underlying the pathogenesis of HCM associated with MYBPC3 PTC mutations by utilizing human isogenic induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).METHODS: Isogenic iPSC lines were generated from patients harboring MYBPC3 PTC mutations (p.R943x; p.R1073P_Fsx4) using genome editing and then differentiated into cardiomyocytes. Comprehensive phenotypical and transcriptome analyses were performed.RESULTS: We observed aberrant calcium handling properties with prolonged decay kinetics and elevated diastolic calcium levels in HCM iPSC-CMs compared to isogenic controls without structural abnormalities or contractile dysfunction. The mRNA expression levels of MYBPC3 were significantly reduced in mutant iPSC-CMs, but the protein levels were comparable among isogenic iPSC-CMs, suggesting that haploinsufficiency of MYBPC3 does not contribute to the pathogenesis of HCM in vitro. Furthermore, truncated MYBPC3 peptides were not detected. At the molecular level, the nonsense-mediated decay (NMD) pathway was activated, and a set of genes involved in major cardiac signaling pathways was dysregulated in HCM iPSC-CMs, indicating an HCM gene signature in vitro. Specific inhibition of the NMD pathway in mutant iPSC-CMs resulted in reversal of the molecular phenotype and normalization of calcium handling abnormalities.CONCLUSIONS: iPSC-CMs carrying MYBPC3 PTC mutations displayed aberrant calcium signaling and molecular dysregulations in the absence of significant haploinsufficiency of MYBPC3 protein. Here we provided the first evidence of the direct connection between the chronically activated NMD pathway and HCM disease development.
View details for PubMedID 30586709
Progress, obstacles, and limitations in the use of stem cells in organ-on-a-chip models.
Advanced drug delivery reviews
In recent years, drug development costs have soared, primarily due to the failure of preclinical animal and cell culture models, which do not directly translate to human physiology. Organ-on-a-chip (OOC) is a burgeoning technology with the potential to revolutionize disease modeling, drug discovery, and toxicology research by strengthening the relevance of culture-based models while reducing costly animal studies. Although OOC models can incorporate a variety of tissue sources, the most robust and relevant OOC models going forward will include stem cells. In this review, we will highlight the benefits of stem cells as a tissue source while considering current limitations to their complete and effective implementation into OOC models.
View details for PubMedID 29885330
Ferumoxytol-based Dual-modality Imaging Probe for Detection of Stem Cell Transplant Rejection.
2018; 2 (4): 306–19
Purpose: Stem cell transplants are an effective approach to repair large bone defects. However, comprehensive techniques to monitor the fate of transplanted stem cells in vivo are lacking. Such strategies would enable corrective interventions at an early stage and greatly benefit the development of more successful tissue regeneration approaches. In this study, we designed and synthesized a dual-modality imaging probe (Feru-AFC) that can simultaneously localize transplanted stem cells and diagnose immune rejection-induced apoptosis at an early stage in vivo. Methods: We used a customized caspase-3 cleavable peptide-dye conjugate to modify the surface of clinically approved ferumoxytol nanoparticles (NPs) to generate the dual-modality imaging probe with fluorescence "light-up" feature. We labeled both mouse mesenchymal stem cells (mMSCs, matched) and pig mesenchymal stem cells (pMSCs, mismatched) with the probe and transplanted the labeled cells with biocompatible scaffold at the calvarial defects in mice. We then employed intravital microscopy (IVM) and magnetic resonance imaging (MRI) to investigate the localization, engraftment, and viability of matched and mismatched stem cells, followed by histological analyses to evaluate the results obtained from in vivo studies. Results: The Feru-AFC NPs showed good cellular uptake efficiency in the presence of lipofectin without cytotoxicity to mMSCs and pMSCs. The fluorescence of Feru-AFC NPs was turned on inside apoptotic cells due to the cleavage of peptide by activated caspase-3 and subsequent release of fluorescence dye molecules. Upon transplantation at the calvarial defects in mice, the intense fluorescence from the cleaved Feru-AFC NPs in apoptotic pMSCs was observed with a concomitant decrease in the overall cell number from days 1 to 6. In contrast, the Feru-AFC NP-treated mMSCs exhibited minimum fluorescence and the cell number also remained similar. Furthermore, in vivo MRI of the Feru-AFC NP-treated mMSC and pMSCs transplants could clearly indicate the localization of matched and mismatched cells, respectively. Conclusions: We successfully developed a dual-modality imaging probe for evaluation of the localization and viability of transplanted stem cells in mouse calvarial defects. Using ferumoxytol NPs as the platform, our Feru-AFC NPs are superparamagnetic and display a fluorescence "light-up" signature upon exposure to activated caspase-3. The results show that the probe is a promising tool for long-term stem cell tracking through MRI and early diagnosis of immune rejection-induced apoptosis through longitudinal fluorescence imaging.
View details for DOI 10.7150/ntno.26389
View details for PubMedID 29977742
View details for PubMedCentralID PMC6030766
Comparison of Non-human Primate versus Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Treatment of Myocardial Infarction.
Stem cell reports
2018; 10 (2): 422–35
Non-human primates (NHPs) can serve as a human-like model to study cell therapy using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). However, whether the efficacy of NHP and human iPSC-CMs is mechanistically similar remains unknown. To examine this, RNU rats received intramyocardial injection of 1 × 107NHP or human iPSC-CMs or the same number of respective fibroblasts or PBS control (n = 9-14/group) at 4 days after 60-min coronary artery occlusion-reperfusion. Cardiac function and left ventricular remodeling were similarly improved in both iPSC-CM-treated groups. To mimic the ischemic environment in the infarcted heart, both cultured NHP and human iPSC-CMs underwent 24-hr hypoxia in vitro. Both cells and media were collected, and similarities in transcriptomic as well as metabolomic profiles were noted between both groups. In conclusion, both NHP and human iPSC-CMs confer similar cardioprotection in a rodent myocardial infarction model through relatively similar mechanisms via promotion of cell survival, angiogenesis, and inhibition of hypertrophy and fibrosis.
View details for PubMedID 29398480
View details for PubMedCentralID PMC5830958
Photoacoustic Imaging of Embryonic Stem Cell-Derived Cardiomyocytes in Living Hearts with Ultrasensitive Semiconducting Polymer Nanoparticles
Advanced Functional Materials
View details for DOI 10.1002/adfm.201704939
Passive Stretch Induces Structural and Functional Maturation of Engineered Heart Muscle as Predicted by Computational Modeling.
Stem cells (Dayton, Ohio)
The ability to differentiate human pluripotent stem cells (hPSCs) into cardiomyocytes (CMs) makes them an attractive source for repairing injured myocardium, disease modeling, and drug testing. Although current differentiation protocols yield hPSC-CMs to >90% efficiency, hPSC-CMs exhibit immature characteristics. With the goal of overcoming this limitation, we tested the effects of varying passive stretch on engineered heart muscle (EHM) structural and functional maturation, guided by computational modeling.Human embryonic stem cells (hESCs, H7 line) or human induced pluripotent stem cells (hiPSCs, IMR-90 line) were differentiated to human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) in vitro using a small molecule based protocol. hPSC-CMs were characterized by troponin(+) flow cytometry as well as electrophysiological measurements. Afterwards, 1.2 x 10(6) hPSC-CMs were mixed with 0.4 x 10(6) human fibroblasts (IMR-90 line) (3:1 ratio) and Type-I collagen. The blend was cast into custom-made 12-mm long polydimethylsiloxane (PDMS) reservoirs to vary nominal passive stretch of EHMs to 5, 7, or 9 mm. EHM characteristics were monitored for up to 50 days, with EHMs having a passive stretch of 7 mm giving the most consistent formation. Based on our initial macroscopic observations of EHM formation, we created a computational model that predicts the stress distribution throughout EHMs, which is a function of cellular composition, cellular ratio, and geometry. Based on this predictive modeling, we show cell alignment by immunohistochemistry and coordinated calcium waves by calcium imaging. Furthermore, coordinated calcium waves and mechanical contractions were apparent throughout entire EHMs. The stiffness and active forces of hPSC-derived EHMs are comparable to rat neonatal cardiomyocyte-derived EHMs. Three-dimensional EHMs display increased expression of mature cardiomyocyte genes including sarcomeric protein troponin-T, calcium and potassium ion channels, β-adrenergic receptors, and t-tubule protein caveolin-3.Passive stretch affects the structural and functional maturation of EHMs. Based on our predictive computational modeling, we show how to optimize cell alignment and calcium dynamics within EHMs. These findings provide a basis for the rational design of EHMs, which enables future scale-up productions for clinical use in cardiovascular tissue engineering. This article is protected by copyright. All rights reserved.
View details for PubMedID 29086457
Molecular and functional resemblance of differentiated cells derived from isogenic human iPSCs and SCNT-derived ESCs.
Proceedings of the National Academy of Sciences of the United States of America
Patient-specific pluripotent stem cells (PSCs) can be generated via nuclear reprogramming by transcription factors (i.e., induced pluripotent stem cells, iPSCs) or by somatic cell nuclear transfer (SCNT). However, abnormalities and preclinical application of differentiated cells generated by different reprogramming mechanisms have yet to be evaluated. Here we investigated the molecular and functional features, and drug response of cardiomyocytes (PSC-CMs) and endothelial cells (PSC-ECs) derived from genetically relevant sets of human iPSCs, SCNT-derived embryonic stem cells (nt-ESCs), as well as in vitro fertilization embryo-derived ESCs (IVF-ESCs). We found that differentiated cells derived from isogenic iPSCs and nt-ESCs showed comparable lineage gene expression, cellular heterogeneity, physiological properties, and metabolic functions. Genome-wide transcriptome and DNA methylome analysis indicated that iPSC derivatives (iPSC-CMs and iPSC-ECs) were more similar to isogenic nt-ESC counterparts than those derived from IVF-ESCs. Although iPSCs and nt-ESCs shared the same nuclear DNA and yet carried different sources of mitochondrial DNA, CMs derived from iPSC and nt-ESCs could both recapitulate doxorubicin-induced cardiotoxicity and exhibited insignificant differences on reactive oxygen species generation in response to stress condition. We conclude that molecular and functional characteristics of differentiated cells from human PSCs are primarily attributed to the genetic compositions rather than the reprogramming mechanisms (SCNT vs. iPSCs). Therefore, human iPSCs can replace nt-ESCs as alternatives for generating patient-specific differentiated cells for disease modeling and preclinical drug testing.
View details for PubMedID 29203658
Biochip-based study of unidirectional mitochondrial transfer from stem cells to myocytes via tunneling nanotubes
2016; 8 (1)
Tunneling nanotubes (TNTs) are small membranous tubes of 50-1000 nm diameter observed to connect cells in culture. Transfer of subcellular organelles through TNTs was observed in vitro and in vivo, but the formation and significance of these structures is not well understood. A polydimethylsiloxane biochip-based coculture model was devised to constrain TNT orientation and explore both TNT-formation and TNT-mediated mitochondrial transfer. Two parallel microfluidic channels connected by an array of smaller microchannels enabled localization of stem cell and cardiomyocyte populations while allowing connections to form between them. Stem cells and cardiomyocytes were deposited in their respective microfluidic channels, and stem cell-cardiomyocyte pairs were formed via the microchannels. Formation of TNTs and transfer of stained mitochondria through TNTs was observed by 24 h real-time video recording. The data show that stem cells are 7.7 times more likely to initiate contact by initial extension of filopodia. By 24 h, 67% of nanotube connections through the microchannels are composed of cardiomyocyte membrane. Filopodial extension and retraction by stem cells draws an extension of TNTs from cardiomyocytes. MitoTracker staining shows that unidirectional transfer of mitochondria between stem cell-cardiomyocyte pairs invariably originates from stem cells. Control experiments with cardiac fibroblasts and cardiomyocytes show little nanotube formation between homotypic or mixed cell pairs and no mitochondrial transfer. These data identify a novel biological process, unidirectional mitochondrial transfer, mediated by heterotypic TNT connections. This suggests that the enhancement of cardiomyocyte function seen after stem-cell injection may be due to a bioenergetic stimulus provided by mitochondrial transfer.
View details for DOI 10.1088/1758-5090/8/1/015012
View details for Web of Science ID 000373289000016
Dynamic Myofibrillar Remodeling in Live Cardiomyocytes under Static Stretch
An increase in mechanical load in the heart causes cardiac hypertrophy, either physiologically (heart development, exercise and pregnancy) or pathologically (high blood pressure and heart-valve regurgitation). Understanding cardiac hypertrophy is critical to comprehending the mechanisms of heart development and treatment of heart disease. However, the major molecular event that occurs during physiological or pathological hypertrophy is the dynamic process of sarcomeric addition, and it has not been observed. In this study, a custom-built second harmonic generation (SHG) confocal microscope was used to study dynamic sarcomeric addition in single neonatal CMs in a 3D culture system under acute, uniaxial, static, sustained stretch. Here we report, for the first time, live-cell observations of various modes of dynamic sarcomeric addition (and how these real-time images compare to static images from hypertrophic hearts reported in the literature): 1) Insertion in the mid-region or addition at the end of a myofibril; 2) Sequential addition with an existing myofibril as a template; and 3) Longitudinal splitting of an existing myofibril. The 3D cell culture system developed on a deformable substrate affixed to a stretcher and the SHG live-cell imaging technique are unique tools for real-time analysis of cultured models of hypertrophy.
View details for DOI 10.1038/srep20674
View details for Web of Science ID 000369743600002
View details for PubMedID 26861590
View details for PubMedCentralID PMC4748238
Interactive relationship between basement-membrane development and sarcomerogenesis in single cardiomyocytes
EXPERIMENTAL CELL RESEARCH
2015; 330 (1): 222-232
The cardiac basement membrane (BM), the highly organized layer of the extracellular matrix (ECM) on the external side of the sarcolemma, is mainly composed of laminin and collagen IV, which assemble a dense, well-organized network to surround the surface of each adult cardiomyocyte. The development of the cardiac BM plays a key role in organogenesis of the myocardium through interactions between sarcomeres and integrins. Because of the complicated structure of cardiac muscle fibers and lack of a proper investigation method, the detailed interactions among BM development, sarcomeric growth, and integrin expression remain unclear. In this study, freshly isolated 3-day neonatal cardiomyocytes (CMs) were cultured on aligned collagen, which mimics the in vivo ECM structure and induces neonatal CMs to grow into rod-like shapes. Then double fluorescence-immunostained laminin and α-actinin or integrin β1 on neonatal CMs cultured 4-72 h were imaged using a confocal microscope, and the spatial relationship between laminin deposition and α-actinin expression was evaluated by colocalization analysis. At 4h, laminin was deposited around Z-bodies (dot-shaped α-actinin) and integrins; from 18-to-72 h, its gradual colocalization with Z-lines (line-shaped α-actinin) and integrins increased Pearson׳s coefficient; this indicates that development of the BM network from the neonatal stage to adulthood is closely related to sarcomeric formation via integrin-mediated interactions.
View details for DOI 10.1016/j.yexcr.2014.08.020
View details for Web of Science ID 000348411500019
View details for PubMedID 25151177
View details for PubMedCentralID PMC4268256
Laser cell-micropatterned pair of cardiomyocytes: the relationship between basement membrane development and gap junction maturation
2014; 6 (4)
The basement membrane (BM), a network of laminin and collagen IV, mechanically supports individual cells and directly mediates cell-cell and cell-extracellular matrix (ECM) interactions. For example, the BM network that tightly encloses each cardiomyocyte (CM) mediates the alignment of CMs with collagen I in the ECM. Additionally, the BM-laminin is involved in the formation of gap junctions (GJs), which regulate electrical coupling between two CMs in the myocardium. The role of BM in GJ maturation remains unclear because of the complicated in vivo structures and lack of an ideal in vitro culturing mode. In this study, our laser cell-micropatterning system was used to place two neonatal CMs (NCMs) in contact on an aligned collagen gel (ACG) to study the relationship between GJ maturation and BM development. The results of double immunofluorescence staining and confocal imaging showed that BM-laminin was deposited earlier than the formation of GJs in the intercellular space and that newly expressed connexin 43 clusters were preferentially assembled near the deposited BM structures. Eventually the BM network surrounded the GJs.
View details for DOI 10.1088/1758-5082/6/4/045003
View details for Web of Science ID 000348353700004
View details for PubMedID 25215627
Role of the Basement Membrane in Regulation of Cardiac Electrical Properties
ANNALS OF BIOMEDICAL ENGINEERING
2014; 42 (6): 1148-1157
In the heart muscle, each adult cardiomyocyte is enclosed by a basement membrane (BM). This innermost extracellular matrix is a layered assembly of laminin, collagen IV, glycoproteins, and proteoglycans. In this study, the role of the BM network in regulation of the electrical properties of neonatal cardiomyocytes (NCMs) cultured on an aligned collagen I gel was investigated using a multielectrode array (MEA). A laminin antibody was added to the culture medium for 48-120 h to conjugate newly secreted laminin. Then, morphology of the NCMs on an MEA was monitored using a phase contrast microscope, and the BM network that was immunocytostained for laminin was imaged using a fluorescence microscope. When the BM laminin was absent in this culture model, dramatic changes in NCM morphology were observed. Simultaneously, the MEA-recorded cardiac field potential showed changes compared to that from the control groups: The period of contraction shortened to 1/2 of that from the control groups, and the waveform of the calcium influx shifted from a flat plateau to a peak-like waveform, indicating that the electrical properties of the NCMs were closely related to the components and distribution of the BM network.
View details for DOI 10.1007/s10439-014-0992-x
View details for Web of Science ID 000335653000003
View details for PubMedID 24577875
View details for PubMedCentralID PMC4011989
Enzyme-etching technique to fabricate micropatterns of aligned collagen fibrils
2014; 36 (6): 1245–52
A technique to tailor-make pre-coated, pre-aligned bovine collagen fibrils, derived from neonatal cardiomyocytes, on the surface of a glass slide into a designated pattern is reported. The unwanted collagen-coated area was erased by a collagenase solution and the tailored area was retained by attaching a microfabricated polydimethylsiloxane stamp directly to the collagen-coated surface. Using this technique, collagen patterns with designated orientations and with clear pattern boundaries and defined shapes were fabricated.
View details for DOI 10.1007/s10529-014-1469-6
View details for Web of Science ID 000335145800015
View details for PubMedID 24562408
View details for PubMedCentralID PMC4075121
- Laser patterning for the study of MSC cardiogenic differentiation at the single-cell level LIGHT-SCIENCE & APPLICATIONS 2013; 2
Mesenchymal Stem Cell-Cardiomyocyte Interactions under Defined Contact Modes on Laser-Patterned Biochips
2013; 8 (2)
Understanding how stem cells interact with cardiomyocytes is crucial for cell-based therapies to restore the cardiomyocyte loss that occurs during myocardial infarction and other cardiac diseases. It has been thought that functional myocardial repair and regeneration could be regulated by stem cell-cardiomyocyte contact. However, because various contact modes (junction formation, cell fusion, partial cell fusion, and tunneling nanotube formation) occur randomly in a conventional coculture system, the particular regulation corresponding to a specific contact mode could not be analyzed. In this study, we used laser-patterned biochips to define cell-cell contact modes for systematic study of contact-mediated cellular interactions at the single-cell level. The results showed that the biochip design allows defined stem cell-cardiomyocyte contact-mode formation, which can be used to determine specific cellular interactions, including electrical coupling, mechanical coupling, and mitochondria transfer. The biochips will help us gain knowledge of contact-mediated interactions between stem cells and cardiomyocytes, which are fundamental for formulating a strategy to achieve stem cell-based cardiac tissue regeneration.
View details for DOI 10.1371/journal.pone.0056554
View details for Web of Science ID 000315970300176
View details for PubMedID 23418583
View details for PubMedCentralID PMC3572044
- Disassembly of Myofibrils in Adult Cardiomyocytes during Dedifferentiation SPIE-INT SOC OPTICAL ENGINEERING. 2013
- Microsystem for Stem Cell-Based Cardiovascular Research BIONANOSCIENCE 2012; 2 (4): 305–15
Cardiogenic Regulation of Stem-Cell Electrical Properties in a Laser-Patterned Biochip
CELLULAR AND MOLECULAR BIOENGINEERING
2012; 5 (3): 327–36
Normal cardiomyocytes are highly dependent on the functional expression of ion channels to form action potentials and electrical coupling with other cells. To fully determine the scientific and therapeutic potential of stem cells for cardiovascular-disease treatment, it is necessary to assess comprehensively the regulation of stem-cell electrical properties during stem cell-cardiomyocyte interaction. It has been reported in the literature that contact with native cardiomyocytes induced and regulated stem-cell cardiogenic differentiation. However, in conventional cell-culture models, the importance of cell-cell contact for stem-cell functional coupling with cardiomyocytes has not been elucidated due to insufficient control of the cell-contact mode of individual cells. Using microfabrication and laser-guided cell micropatterning techniques, we created two biochips with contact-promotive and -preventive microenvironments to systematically study the effect of contact on cardiogenic regulation of stem-cell electrical properties. In contact-promotive biochips, connexin 43 expression was upregulated and relocated to the junction area between one stem cell and one cardiomyocyte. Only stem cells in contact with cardiomyocytes were induced by adjacent cardiomyocytes to acquire electrophysiological properties for action-potential formation similar to that of a cardiomyocyte.
View details for DOI 10.1007/s12195-012-0240-0
View details for Web of Science ID 000308246000009
View details for PubMedID 23139730
View details for PubMedCentralID PMC3489499
Laser-patterned stem-cell bridges in a cardiac muscle model for on-chip electrical conductivity analyses
LAB ON A CHIP
2012; 12 (3): 566-573
Following myocardial infarction there is an irreversible loss of cardiomyocytes that results in the alteration of electrical propagation in the heart. Restoration of functional electrical properties of the damaged heart muscle is essential to recover from the infarction. While there are a few reports that demonstrate that fibroblasts can form junctions that transmit electrical signals, a potential alternative using the injection of stem cells has emerged as a promising cellular therapy; however, stem-cell electrical conductivity within the cardiac muscle fiber is unknown. In this study, an in vitro cardiac muscle model was established on an MEA-based biochip with multiple cardiomyocytes that mimic cardiac tissue structure. Using a laser beam, stem cells were inserted adjacent to each muscle fiber (cell bridge model) and allowed to form cell-cell contact as determined by the formation of gap junctions. The electrical conductivity of stem cells was assessed and compared with the electrical conductivities of cardiomyocytes and fibroblasts. Results showed that stem cell-myocyte contacts exhibited higher and more stable conduction velocities than myocyte-fibroblast contacts, which indicated that stem cells have higher electrical compatibility with native cardiac muscle fibers than cardiac fibroblasts.
View details for DOI 10.1039/c2lc20699d
View details for Web of Science ID 000298964300017
View details for PubMedID 22170399
View details for PubMedCentralID PMC3342821
Enhanced cell affinity of the silk fibroin- modified PHBHHx material
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE
2009; 20 (8): 1743–51
Cell affinity is one of the important issues required for developing tissue engineering materials. Although the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has been attractive for its controllable mechanical properties recent years, its cell affinity is still necessary to be improved for the requirements. For this purpose, the regenerated silk fibroin (SF) was coated on the PHBHHx films and its porous scaffolds. The mechanical test showed that SF-modified PHBHHx (SF/PHBHHx) film has a maximum tensile strength of 11.5 +/- 0.5 MPa and elongation at break of 175 +/- 5%. ATR-FTIR spectroscopy demonstrated that SF firmly attached on the scaffold by the hydrogen bonding interaction between SF and PHBHHx even flushed for 21 days in the phosphate-buffer saline (PBS) solution (pH = 7.4). In order to characterize the cell affinity of the SF-modified material, endothelial-like cell line ECV304 cells were seeded on the SF/PHBHHx films and its porous scaffolds. The histochemical analyses of cells stained by the hematoxylin and eosin (HE) as well as cell nuclei stained by the 4',6-diamindine-2'-phenylindole (DAPI) demonstrated that cell attached and reached nearly 100% confluence on the SF/PHBHHx films when cultured for 4 days, which was much faster than that on the pure PHBHHx film. Moreover, the assay of cell activity by the 3-(4, 5-dimethyl thiazol -2-yl)-2, 5-diphenyl terazolium bromide (MTT) showed quantitatively that the number of cells on the SF/PHBHHx porous scaffolds was significant more than that on the unmodified ones after 4, 8, and 14 days culture, respectively. Scanning electron microscopy (SEM) revealed the similar results. Therefore, the SF-modified PHBHHx material is maybe a potential material applicable in the cardiovascular tissue engineering.
View details for DOI 10.1007/s10856-009-3739-8
View details for Web of Science ID 000268103300018
View details for PubMedID 19333570
- Investigation of water diffusion in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by generalized two-dimensional correlation ATR-FTIR spectroscopy POLYMER 2009; 50 (6): 1533-1540