Cardiomyogenic induction of human mesenchymal stem cells by altered Rho family GTPase expression on dendrimer-immobilized surface with D-glucose display

The effect of shear stress on cardiac differentiation of mesenchymal stem cells

BACKGROUND

Stem cell therapy is developing as a valuable therapeutic trend for heart diseases. Most recent studies are aimed to find the most appropriate types of stem cells for the treatment of myocardial infarction (MI). The animal models have shown that bone marrow-derived mesenchymal stem cells (BMSCs) are a possible, safe, and efficient type of stem cell used in MI. The previous study demonstrated that 5-Azacytidine (5-Aza) could promote cardiac differentiation in stem cells.

METHODS

This study used 5-Aza to induce cardiomyocyte differentiation in BMSCs both in static and microfluidic cell culture systems. For this purpose, we investigated the differentiation by using real-time PCR and Immunocytochemistry (ICC) Analysis.

RESULTS

Our results showed that 5-Aza could cause to express cardiac markers in BMSCs as indicated by real-time PCR and immunocytochemistry (ICC). However, BMSCs are exposed to both 5-Aza and shear stress, and their synergistic effects could significantly induce cardiac gene expressions in BMSCs. This level of gene expression was observed neither in 5-Aza nor in shear stress groups only.

CONCLUSIONS

These results demonstrate that when BMSCs expose to 5-Aza as well as mechanical cues such as shear stress, the cardiac gene expression can be increased dramatically.

Novel approach to enhance aggregate migration-driven epigenetic memory which induces cardiomyogenic differentiation on a dendrimer-immobilized surface

The dynamic migratory behavior of human mesenchymal stem cells (hMSCs) has a significant impact on the epigenetic profiles that determine fate choice and lineage commitment during differentiation. Here we report a novel approach to enhance repeated migration-driven epigenetic memory which induces cardiomyogenic differentiation on a dendrimer surface with fifth generation (G5). Cells exhibited the formation of cell aggregates on the G5 surface through active migration with morphological changes, and these aggregates showed strong expression of the cardiac-specific marker cardiac troponin T (cTnT) at 10 days. When cell aggregates were passaged onto a fresh G5 surface over three passages of 40 days, the expression levels of the multiple cardiac-specific markers including GATA4, NKX2.5, MYH7, and TNNT2 were higher compared to those passaged as single cells. To investigate whether cardiomyogenic differentiation of hMSCs was enhanced by repeated aggregate migration-driven epigenetic memory, cells on the G5 surface were reseeded onto a fresh G5 surface during three passages using aggregate-based and single cell-based passage methods. Analyses of global changes in H3 histone modifications exhibited pattern of increased H3K9ac and H3K27me3, and decreased H3K9me3 in aggregate-based passage cultures during three passages. However, the pattern of their histone modification on the PS surface was repeated after the initialization and reformation during three passages in single cell-based passage cultures. Thus, repetitive aggregate migratory behavior during aggregate-based passage led to a greater degree of histone modification, as well as gene expression changes suggestive of cardiomyogenic differentiation.

Muscle lineage switching by migratory behaviour-driven epigenetic modifications of human mesenchymal stem cells on a dendrimer-immobilized surface

Understanding of the fundamental mechanisms of epigenetic modification in the migration of human mesenchymal stem cells (hMSCs) provides surface design strategies for controlling self-renewal and lineage commitment. We investigated the mechanism underlying muscle lineage switching of hMSCs by cellular and nuclear deformation during cell migration on polyamidoamine dendrimer surfaces. With an increase in the dendrimer generation number, cells exhibited increased nuclear deformation and decreased lamin A/C and lamin B1 expression. Analysis of two repressive modifications (H3K9me3 and H3K27me3) and one activating modification (H3K9ac) revealed that H3K9me3 was suppressed, and H3K9ac and H3K27me3 were upregulated in the cultures on a higher-generation dendrimer surface. This induced significant hMSC lineage switching to smooth, skeletal, and cardiac muscle lineages. Thus, reorganizations of the nuclear lamina and cytoskeleton related to migration changes on dendrimer surfaces are responsible for the integrated regulation of histone modifications in hMSCs, thereby shifting the cells from the multipotent state to muscle lineages. These findings improve our understanding of the role of epigenetic modification in cell migration and provide new insights into how designed surfaces can be applied as cell-instructive materials in the field of biomaterial-guided differentiation of hMSCs to different cell types. STATEMENT OF SIGNIFICANCE: Stem cell engineering strategies currently applied the mechanical cues that emerge from cellular microenvironment to regulate stem cell behaviour. This study significantly improved our understanding of the mechanotransduction mechanism involving cell-ECM and cytoskeleton-nucleoskeleton interactions, and of nuclear genome regulation based on cellular responses to biomaterial modifications. The new insights into how the physical environment on a culture surface influences cell behaviour improve our understanding of mechanical control mechanisms of the interactions of cells with the extracellular environment. Our findings are also expected to contribute to and play an essential role in the development of future material strategies for creating artificial cell-instructive niches.

Alterations in Nuclear Lamina and the Cytoskeleton of Bone Marrow-Derived Human Mesenchymal Stem Cells Cultured Under Simulated Microgravity Conditions

Cells sense and respond to environmental changes induced by gravity. Although reactions to conventional culture have been intensively studied, little is known about the cellular reaction to simulated microgravity conditions. Thus, in this study, we investigated the effects of simulated microgravity on human mesenchymal stem cells using a three-dimensional clinostat (Gravite^®), a recently developed device used to generate simulated microgravity condition in vitro. Our time-lapse analysis shows that cells cultured under conventional culture conditions have a stretched morphology and undergo unidirectional migration, whereas cells cultured under simulated microgravity conditions undergo multidirectional migration with directional changes of cell movement. Furthermore, cells cultured under conventional culture conditions maintained their spindle shape through fibronectin fibril formation in their bodies and focal adhesion stabilization with enriched stress fibers. However, cells cultured under simulated microgravity conditions were partially contracted and the fibril structures were degraded in the cell bodies. Additionally, paxillin phosphorylation in the cells cultured under simulated microgravity conditions was more intense at the cell periphery in regions near the leading and trailing edges, but was less expressed in the cell bodies compared with that observed in cells cultured under conventional culture conditions. Furthermore, lamin A/C, a major component of the nuclear lamina, was mainly located on the apical side in cells cultured under conventional culture conditions, indicating basal-to-apical polarization. However, cells cultured under simulated microgravity conditions showed lamin A/C localization on both the apical and basal sides. Taken together, these results demonstrate that simulated microgravity-driven fibronectin assembly affects nuclear lamina organization through the spatial reorganization of the cytoskeleton.

Maintenance of an undifferentiated state of human-induced pluripotent stem cells through botulinum hemagglutinin-mediated regulation of cell behavior

Applications of human induced pluripotent stem cell (hiPSC) culture are impaired by problems with long term maintenance of pluripotency. In this study, we report that exposure to botulinum hemagglutinin (HA), an E-cadherin function-blocking agent, suppressed deviation from an undifferentiated state in hiPSC colonies. Time-lapse imaging of live cells revealed that cells in central regions of colonies moved slowly and underwent a morphological change to a cobblestone-like shape via interaction between contacting cells, forming dense, multiple layers. Staining and migration analysis showed that actin stress fibers and paxillin spots were diminished in colony central regions, and this was associated with alteration of cellular morphology and migratory behavior. However, in culture with HA exposure, cells in the central and peripheral regions of hiPSC colonies were migratory and arranged in loose monolayers, resulting in relatively uniform dispersion of cells in colonies. We also found that a well-organized network of actin stress fibers was of significance in the central and peripheral regions of a colony, resulting in activation of paxillin and E-cadherin expression in hiPSCs. After routine application of HA for serial passages, hiPSCs remained pluripotent and capable of differentiating into all three germ layers. These observations indicate that relaxation of cell-cell junctions by HA induced rearrangements of the cytoskeleton and cell adhesion in hiPSC colonies by promoting migratory behaviors. These results suggest that this simple and readily reproducible culture strategy is a potentially useful tool for improving the robust and scalable maintenance of undifferentiated hiPSC cultures.

Surface-modified polymers for cardiac tissue engineering

Cardiovascular disease (CVD), leading to myocardial infarction and heart failure, is one of the major causes of death worldwide. The physiological system cannot significantly regenerate the capabilities of a damaged heart. The current treatment involves pharmacological and surgical interventions; however, less invasive and more cost-effective approaches are sought. Such new approaches are developed to induce tissue regeneration following injury. Hence, regenerative medicine plays a key role in treating CVD. Recently, the extrinsic stimulation of cardiac regeneration has involved the use of potential polymers to stimulate stem cells toward the differentiation of cardiomyocytes as a new therapeutic intervention in cardiac tissue engineering (CTE). The therapeutic potentiality of natural or synthetic polymers and cell surface interactive factors/polymer surface modifications for cardiac repair has been demonstrated in vitro and in vivo. This review will discuss the recent advances in CTE using polymers and cell surface interactive factors that interact strongly with stem cells to trigger the molecular aspects of the differentiation or formulation of cardiomyocytes for the functional repair of heart injuries or cardiac defects.

Maintenance of human chondrogenic phenotype on a dendrimer-immobilized surface for an application of cell sheet engineering

BACKGROUND

Dedifferentiation of chondrocytes during cell expansion is one of the barriers in tissue construction for cartilage repair. To understand chondrocyte behavior and improve cell expansion in monolayer culture, this study investigated the effects of morphological changes and cellular aggregation on the maintenance of chondrogenic capacity by observing the expression patterns of chondrogenic (collagen type II and aggrecan) and dedifferentiation (collagen type I) markers. Primary human chondrocytes were cultured on either a polystyrene surface (PS) or a polyamidoamine dendrimer surface with a fifth-generation (G5) dendron structure to create a one-step process of cell expansion and the maintenance of chondrogenic activities prior to the construction of cell sheets.

RESULTS

During the first two passages (P0 - P2), the relative mRNA level of collagen type II decreased in all cultures, while that of collagen type I increased. Remarkably, the level of collagen type II was higher and aggrecan was retained in the chondrocytes, forming cell aggregates and showing some round-shaped cells with less production of stress fibers on the G5 surface compared to fibroblast-like chondrocytes with abundant stress fibers on the PS surface. The numbers of P2 chondrocytes on the G5 and PS surfaces were nearly the same and sufficient for construction of chondrocyte sheets using a temperature-responsive plate. Without a supporting material during cell sheet manipulation, chondrocyte sheets spontaneously detached and exhibited a honeycomb-like structure of stress fibers. Unlike the chondrocyte sheets constructed from cells on the PS surface, the chondrocyte sheets from cells on the G5 surface had higher chondrogenic activities, as evidenced by the high expression of chondrogenic markers and the low expression of dedifferentiation markers.

CONCLUSIONS

The one-step process of cell expansion and maintenance of chondrogenic activity could be obtained using the G5 surface. Human chondrocyte sheets were successfully constructed with high chondrogenic activity. These findings may lead to an alternative cultivation technique for human chondrocytes that offers high clinical potential in autologous chondrocyte implantation.

Botulinum hemagglutinin-mediated selective removal of cells deviating from the undifferentiated state in hiPSC colonies

The undifferentiated state of human induced pluripotent stem cells (hiPSCs) depends on their cell–cell and cell–substrate adhesions. In this study, we report that exposure to botulinum hemagglutinin (HA), an E-cadherin function-blocking agent, selectively removed cells that deviated from the undifferentiated state in hiPSC colonies. After HA treatment, cell–cell adhesion was disrupted, deviated cells detached from colony centers, and dividing cells filled these spaces. Because E-cadherin-mediated adhesion was disrupted in undifferentiated cells, stress-fiber formation and focal adhesions were diminished; however, these were subsequently restored, and the cells retained expression of undifferentiated stem cell markers and their differentiation potential. In contrast, actin structures and focal adhesions were lost from deviated cells, and they subsequently died. In undifferentiated and deviated cells, the cadherin/integrin-regulator Rap1 was localized at cell–cell adhesions and in the cytoplasm, respectively. Concurrent HA and Rap1-inhibitor treatment accelerated the deviated-cell detachment and delayed the recovery of hiPSC morphology, but this effect was significantly attenuated by co-treatment with Rap1 activator. Thus, Rap1 regulated E-cadherin–integrin interplay in hiPSC colonies exhibiting deviation, while HA-mediated selective removal of these deviated cells helped maintain the undifferentiated state in the remaining hiPSCs.

Dynamic polyrotaxane-coated surface for effective differentiation of mouse induced pluripotent stem cells into cardiomyocytes

Increasing molecular mobility of hydrated polyrotaxane (PRX)-coated surfaces was effective to promote the differentiation of mouse induced pluripotent stem cells (iPS cells) into cardiomyocytes.

RhoGTPases as key players in mammalian cell adaptation to microgravity

A growing number of studies are revealing that cells reorganize their cytoskeleton when exposed to conditions of microgravity. Most, if not all, of the structural changes observed on flown cells can be explained by modulation of RhoGTPases, which are mechanosensitive switches responsible for cytoskeletal dynamics control. This review identifies general principles defining cell sensitivity to gravitational stresses. We discuss what is known about changes in cell shape, nucleus, and focal adhesions and try to establish the relationship with specific RhoGTPase activities. We conclude by considering the potential relevance of live imaging of RhoGTPase activity or cytoskeletal structures in order to enhance our understanding of cell adaptation to microgravity-related conditions.

hMSCs bridging across micro-patterned grooves

hMSCs spanned across a groove with 100 μm width.

Maintenance of undifferentiated state of human induced pluripotent stem cells through cytoskeleton-driven force acting to secreted fibronectin on a dendrimer-immobilized surface

Understanding of the fundamental mechanisms that govern adhesive properties of human induced pluripotent stem cells (hiPSCs) to culture environments provides surface design strategies for maintaining their undifferentiated state during cell expansion. Polyamidoamine dendrimer surface with first-generation (G1) with dendron structure was used for co-cultures of hiPSCs and SNL feeder cells that formed tightly packed compact hiPSC colonies, similar to those on a conventional gelatin-coated surface. hiPSCs passaged up to 10 times on the G1 surface maintained their undifferentiated state. Immunostaining and reverse transcriptase PCR analysis of fibronectin showed that the secreted fibronectin matrix from feeder cells on the G1 surface contributed to hiPSC attachment. Compared with cells on the gelatin-coated surface, F-actin and paxillin immunostaining revealed a well-organized network of actin stress fibers and focal adhesion formation at cell-substrate sites in hiPSC colonies on the G1 surface. E-cadherin expression levels on these surfaces were almost same, but paxillin and Rac1 expression levels on the G1 surface were significantly higher than those on the gelatin-coated surface. Zyxin showed prominent expression on the G1 surface at sites of focal adhesion and cell-cell contact in colonies, whereas zyxin expression on the gelatin-coated surface was not observed in regions of cell-cell contact. These findings indicate that transduction of mechanical stimuli through actin polymerization at sites of focal adhesion and cell-cell contact results in maintenance of undifferentiated hiPSC colonies on G1 surface. The G1 surface enables a substrate design based on the mechanical cues in the microenvironment from feeder cells to expand undifferentiated hiPSCs in long-term culture.

Induction of myogenic differentiation of human mesenchymal stem cells cultured on Notch agonist (Jagged-1) modified biodegradable scaffold surface

Engineered scaffold surface provides stem cells with vital cues that could determine the eventual fate of stem cells. In this work, biodegradable poly(L-lactide-co-ε-caprolactone) (PLCL) scaffold conjugated with Notch agonist-Jagged-1(JAG) peptide (2.1 kDa) was prepared to initiate myogenic differentiation of human mesenchymal stem cells (hMSCs). The scaffold surface was activated with oxygen plasma and acrylic acid was engrafted via UV polymerization to form a surface bearing carboxylic groups. JAG peptide was subsequently immobilized onto the carboxylated scaffold surface. Surface chemistry and topography were examined using attenuated total reflection Fourier transform infrared, X-ray photoelectron spectroscopy, and atomic force microscopy. Quantitative real time polymerase chain reaction analysis revealed activation of the Notch pathway; furthermore, several specific markers associated with myogenic but not osteogenic differentiation were shown to be up-regulated in hMSCs cultured on the engineered surface. The pro-myocardial effect of surface bound JAG peptide was further affirmed via immunodetection of the distinct myocardial marker, cardiac troponin T. Collectively, our results suggest that PLCL conjugated JAG peptide is a viable strategy to enhance the functional potential of scaffolds to be used as a bioengineered cardiac patch in myocardial infarction repair.

Graphene-regulated cardiomyogenic differentiation process of mesenchymal stem cells by enhancing the expression of extracellular matrix proteins and cell signaling molecules

The potential of graphene as a mesenchymal stem cell (MSC) culture substrate to promote cardiomyogenic differentiation is demonstrated. Graphene exhibits no sign of cytotoxicity for stem cell culture. MSCs are committed toward cardiomyogenic lineage by simply culturing them on graphene. This may be attributed, at least partially, to the regulation of expression levels of extracellular matrix and signaling molecules.

The calcium-dependent regulation of spheroid formation and cardiomyogenic differentiation for MSCs on chitosan membranes

Mesenchymal stem cells (MSCs) were recently found to form three-dimensional (3D) multicellular spheroids on chitosan membranes. The exact mechanism of spheroid formation, however, remains unclear. In this study, the regulation of spheroid formation for adipose derived adult stem cells (ADAS) grown on chitosan membranes was examined. By varying the membrane thickness, calcium concentration in culture medium, and acetylation extent of chitosan, the physico-chemical characteristics of chitosan that modulated spheroid formation was elucidated. The capacity of cardiomyogenic differentiation was further evaluated. Results suggested that the calcium binding capacity of chitosan may affect the cell-substrate and cell-cell interactions and critically influence the dynamics of spheroid formation. The intracellular calcium level was elevated for ADAS spheroids on chitosan. Chitosan-bound calcium was observed to enter the cells. The expression of N-cadherin was upregulated for ADAS spheroids on chitosan, evidenced by quantitative RT-PCR and Western blot. After the induction by 5-aza, the expression levels of cardiac marker genes (Gata4, Nkx2.5, Tnnt2, and Myh6) were remarkably enhanced (about four-fold) for ADAS on chitosan vs. tissue culture polystyrene or polyvinyl alcohol. Immunofluorescence staining confirmed the expression of cardiac-associated tight junction protein ZO-1 for ADAS grown on chitosan membranes. The gene expression of Wnt11 was significantly upregulated for ADAS spheroids on chitosan at 3 days and 12 days. We suggested that Wnt11 may be involved in the spheroid formation and cardiomyogenic differentiation of MSCs on chitosan membranes. Spheroids formed on the acetylated chitosan or polyvinyl alcohol membranes failed to show such behavior. The properties of MSC spheroids were therefore determined by the culture substrate.

Bone marrow-derived human mesenchymal stem cells express cardiomyogenic proteins but do not exhibit functional cardiomyogenic differentiation potential

Despite their paracrine activites, cardiomyogenic differentiation of bone marrow (BM)-derived mesenchymal stem cells (MSCs) is thought to contribute to cardiac regeneration. To systematically evaluate the role of differentiation in MSC-mediated cardiac regeneration, the cardiomyogenic differentiation potential of human MSCs (hMSCs) and murine MSCs (mMSCs) was investigated in vitro and in vivo by inducing cardiomyogenic and noncardiomyogenic differentiation. Untreated hMSCs showed upregulation of cardiac tropopin I, cardiac actin, and myosin light chain mRNA and protein, and treatment of hMSCs with various cardiomyogenic differentiation media led to an enhanced expression of cardiomyogenic genes and proteins; however, no functional cardiomyogenic differentiation of hMSCs was observed. Moreover, co-culturing of hMSCs with cardiomyocytes derived from murine pluripotent cells (mcP19) or with murine fetal cardiomyocytes (mfCMCs) did not result in functional cardiomyogenic differentiation of hMSCs. Despite direct contact to beating mfCMCs, hMSCs could be effectively differentiated into cells of only the adipogenic and osteogenic lineage. After intramyocardial transplantation into a mouse model of myocardial infarction, Sca-1(+) mMSCs migrated to the infarcted area and survived at least 14 days but showed inconsistent evidence of functional cardiomyogenic differentiation. Neither in vitro treatment nor intramyocardial transplantation of MSCs reliably generated MSC-derived cardiomyocytes, indicating that functional cardiomyogenic differentiation of BM-derived MSCs is a rare event and, therefore, may not be the main contributor to cardiac regeneration.

The roles of RGD and grooved topography in the adhesion, morphology, and differentiation of C2C12 skeletal myoblasts

Both chemical and topographic cues are crucial for the development of skeletal muscle. In this study, the relative roles of both signals in regard to cell adhesion, morphology, and differentiation of C2C12 skeletal myoblasts were investigated. Grooved polystyrene substrates containing grooves with approximately 900 nm in width with 600 nm ridge spans and 665 nm in depth were conjugated with the cell adhesion peptide arginine-glycine-aspartic acid (RGD). RGD conjugation significantly enhanced the adhesion, growth and differentiation of C2C12 cells. On the other hand, anisotropic topography primarily directed the direction and alignment of myoblasts and myotubes. The results in this study provide information regarding the relative roles of chemical and topographic cues in musculoskeletal myogenesis, and are of interest to applications in muscle tissue engineering.