Cardiac myofibroblast differentiation, as one of the most important cellular responses to heart injury, plays a critical role in cardiac remodeling and failure. While biochemical cues for this have been extensively investigated, the role of mechanical cues, e.g., extracellular matrix stiffness and mechanical strain, has also been found to mediate cardiac myofibroblast differentiation. Cardiac fibroblasts in vivo are typically subjected to a specific spatiotemporally changed mechanical microenvironment. When exposed to abnormal mechanical conditions (e.g., increased extracellular matrix stiffness or strain), cardiac fibroblasts can undergo myofibroblast differentiation. To date, the impact of mechanical cues on cardiac myofibroblast differentiation has been studied both in vitro and in vivo. Most of the related in vitro research into this has been mainly undertaken in two-dimensional cell culture systems, although a few three-dimensional studies that exist revealed an important role of dimensionality. However, despite remarkable advances, the comprehensive mechanisms for mechanoregulation of cardiac myofibroblast differentiation remain elusive. In this review, we introduce important parameters for evaluating cardiac myofibroblast differentiation and then discuss the development of both in vitro (two and three dimensional) and in vivo studies on mechanoregulation of cardiac myofibroblast differentiation. An understanding of the development of cardiac myofibroblast differentiation in response to changing mechanical microenvironment will underlie potential targets for future therapy of cardiac fibrosis and failure.
Cardiac c-kit cells show promise in regenerating an injured heart. While heart disease commonly affects elderly patients, it is unclear if autologous cardiac c-kit cells are functionally competent and applicable to these patients. This study characterised cardiac c-kit cells (CCs) from aged mice and studied the effects of human Wharton's Jelly-derived mesenchymal stem cells (MSCs) on the growth kinetics and cardiac differentiation of aged CCs in vitro. CCs were isolated from 4-week- and 18-month-old C57/BL6N mice and were directly co-cultured with MSCs or separated by transwell insert. Clonogenically expanded aged CCs showed comparable telomere length to young CCs. However, these cells showed lower Gata4, Nkx2.5, and Sox2 gene expressions, with changes of 2.4, 3767.0, and 4.9 folds, respectively. Direct co-culture of both cells increased aged CC migration, which repopulated 54.6 ± 4.4% of the gap area as compared to aged CCs with MSCs in transwell (42.9 ± 2.6%) and CCs without MSCs (44.7 ± 2.5%). Both direct and transwell co-culture improved proliferation in aged CCs by 15.0% and 16.4%, respectively, as traced using carboxyfluorescein succinimidyl ester (CFSE) for three days. These data suggest that MSCs can improve the growth kinetics of aged CCs. CCs retaining intact telomere are present in old hearts and could be obtained based on their self-renewing capability. Although these aged CCs with reduced growth kinetics are improved by MSCs via cell-cell contact, the effect is minimal.
Dental tissues contains stem cells or progenitors that have high proliferative capacity, are clonogenic in vitro and demonstrate the ability to differentiate to multiple type cells involving neurons, bone, cartilage, fat and smooth muscle. Numerous experiments have demonstrated that the multipotent stem cells are not rejected by immune system and therefore it may be possible to use these cells in allogeneic settings. In addition, these remarkable cells are easily abundantly available couple with less invasive procedure in isolating comparing to bone marrow aspiration. Here we proposed dental stem cells as candidate for cardiac regeneration based on its immature characteristic and propensity towards cardiac lineage via PI3-Kinase/Aktsignalling pathway.
The coronavirus disease 2019 (COVID-19) pandemic with high infectivity and mortality has caused severe social and economic impacts worldwide. Growing reports of COVID-19 patients with multi-organ damage indicated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) may also disturb the cardiovascular system. Herein, we used human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iCMs) as the in vitro platform to examine the consequence of SARS-CoV2 infection on iCMs. Differentiated iCMs expressed the primary SARS-CoV2 receptor angiotensin-converting enzyme-II (ACE2) and the transmembrane protease serine type 2 (TMPRSS2) receptor suggesting the susceptibility of iCMs to SARS-CoV2. Following the infection of iCMs with SARS-CoV2, the viral nucleocapsid (N) protein was detected in the host cells, demonstrating the successful infection. Bioinformatics analysis revealed that the SARS-CoV2 infection upregulates several inflammation-related genes, including the proinflammatory cytokine tumor necrosis factor-α (TNF-α). The pretreatment of iCMs with TNF-α for 24 h, significantly increased the expression of ACE2 and TMPRSS2, SASR-CoV2 entry receptors. The TNF-α pretreatment enhanced the entry of GFP-expressing SARS-CoV2 pseudovirus into iCMs, and the neutralization of TNF-α ameliorated the TNF-α-enhanced viral entry. Collectively, SARS-CoV2 elevated TNF-α expression, which in turn enhanced the SARS-CoV2 viral entry. Our findings suggest that, TNF-α may participate in the cytokine storm and aggravate the myocardial damage in COVID-19 patients.
Mesenchymal stem cells (MSCs) are known to secrete cardioprotective paracrine factors that can potentially activate endogenous cardiac c-kit cells (CCs). This study aims to optimise MSC growth conditions and medium formulation for generating the conditioned medium (CdM) to facilitate CC growth and expansion in vitro. The quality of MSC-CdM after optimisation of seeding density during MSC stabilisation and medium formulation used during MSC stimulation including glucose, ascorbic acid, serum and oxygen levels and the effects of treatment concentration and repeated CdM harvesting were assessed based on CC viability in vitro under growth factor- and serum-deprived condition. Our data showed that functional CdM can be produced from MSCs with a density of 20,000 cells/cm2, which were stimulated using high glucose (25 mM), ascorbic acid supplemented, serum-free medium under normoxic condition. The generated CdM, when applied to growth factor- and serum-deprived medium at 1:1 ratio, improved CC viability, migration and proliferation in vitro. Such an effect could further be augmented by generating CdM concentrates without compromising CC gene and protein expressions, while retaining its capability to undergo differentiation to form endothelial, smooth muscle and cardiomyocytes. Nevertheless, CdM could not be repeatedly harvested from the same MSC culture, as the protein content and its effect on CC viability deteriorated after the first harvest. In conclusion, this study provides a proof-of-concept strategy to standardise the production of CdM from MSCs based on rapid, stepwise assessment of CC viability, thus enabling production of CdM favourable to CC growth for in vitro or clinical applications.