Involvement of Rictor/mTORC2 in cardiomyocyte differentiation of mouse embryonic stem cells in vitro

Rictor is a key regulatory/structural subunit of the mammalian target of rapamycin complex 2 (mTORC2) and is required for phosphorylation of Akt at serine 473. It plays an important role in cell survival, actin cytoskeleton organization and other processes in embryogenesis. However, the role of Rictor/mTORC2 in the embryonic cardiac differentiation has been uncovered. In the present study, we examined a possible link between Rictor expression and cardiomyocyte differentiation of the mouse embryonic stem (mES) cells. Knockdown of Rictor by shRNA significantly reduced the phosphorylation of Akt at serine 473 followed by a decrease in cardiomyocyte differentiation detected by beating embryoid bodies. The protein levels of brachyury (mesoderm protein), Nkx2.5 (cardiac progenitor cell protein) and α-Actinin (cardiomyocyte biomarker) decreased in Rictor knockdown group during cardiogenesis. Furthermore, knockdown of Rictor specifically inhibited the ventricular-like cells differentiation of mES cells with reduced level of ventricular-specific protein, MLC-2v. Meanwhile, patch-clamp analysis revealed that shRNA-Rictor significantly increased the number of cardiomyocytes with abnormal electrophysiology. In addition, the expressions and distribution patterns of cell-cell junction proteins (Cx43/Desmoplakin/N-cadherin) were also affected in shRNA-Rictor cardiomyocytes. Taken together, the results demonstrated that Rictor/mTORC2 might play an important role in the cardiomyocyte differentiation of mES cells. Knockdown of Rictor resulted in inhibiting ventricular-like myocytes differentiation and induced arrhythmias symptom, which was accompanied by interfering the expression and distribution patterns of cell-cell junction proteins. Rictor/mTORC2 might become a new target for regulating cardiomyocyte differentiation and a useful reference for application of the induced pluripotent stem cells.

Peroxiredoxin-2 nitrosylation facilitates cardiomyogenesis of mouse embryonic stem cells via XBP-1s/PI3K pathway

Protein nitrosylation is a ubiquitous post-translational modification in almost all biological systems. However, its function on stem cell biology is so far incompletely understood. Here, we demonstrated that peroxiredoxin 2 (Prdx-2) nitrosylation was involved in cardiomyocyte differentiation of mouse embryonic stem (ES) cells induced by S-nitrosoglutathione (GSNO). We found that temporary GSNO exposure could promote ES cell-derived cardiomyogenesis. Using a stable isotope labeling by amino acids in cell culture (SILAC)-based proteomics approach, coupled with biotin switch technique, a total of 104 nitrosylated proteins were identified. Specifically, one of the antioxidant enzymes, Prdx-2, was abundantly nitrosylated and temporarily reduced in antioxidant activity, causing transient endogenous hydrogen peroxide (H2O2) accumulation and subsequent X-box binding protein-1s/phosphatidylinositol 3-kinase pathway activation. The present study reveals the mechanism in which GSNO favors cardiomyocyte differentiation. Prdx-2 nitrosylation could be a potent strategy to affect the pluripotent stem cell-derived cardiomyogenesis.

Alpha-lipoic acid enhances DMSO-induced cardiomyogenic differentiation of P19 cells

Alpha-lipoic acid (α-LA) is a potent antioxidant that acts as an essential cofactor in mitochondrial dehydrogenase reactions. α-LA has been shown to possess anti-inflammatory and cytoprotective properties, and is used to improve symptoms of diabetic neuropathy. However, the role of α-LA in stem cell differentiation and the underlying molecular mechanisms remain unknown. In the present study, we showed that α-LA significantly promoted dimethyl sulfoxide (DMSO)-induced cardiomyogenic differentiation of mouse embryonic carcinoma P19 cells. α-LA dose dependently increased beating embryonic body (EB) percentages of DMSO-differentiated P19 cells. The expressions of cardiac specific genes TNNT2, Nkx2.5, GATA4, MEF2C, and MLC2V and cardiac isoform of troponin T (cTnT)-positively stained cell population were significantly up-regulated by the addition of α-LA. We also demonstrated that the differentiation time after EB formation was critical for α-LA to take effect. Interestingly, without DMSO treatment, α-LA did not stimulate the cardiomyogenic differentiation of P19 cells. Further investigation indicated that collagen synthesis-enhancing activity, instead of the antioxidative property, plays a significant role in the cardiomyogenic differentiation-promoting function of α-LA. These findings highlight the potential use of α-LA for regenerative therapies in heart diseases.

Conjugated polyelectrolyte materials for promoting progenitor cell growth without serum

The discovery of new active biomaterials for promoting progenitor cell growth and differentiation in serum-free medium is still proving more challenging for the clinical treatments of degenerative diseases. In this work, a conjugated polyelectrolyte, polythiophene derivative (PMNT), was discovered to significantly drive the cell cycle progression from G₁ to S and G₂ phases and thus efficiently promote the cell growth without the need of serum. Furthermore, the fluorescent characteristic of PMNT makes it simultaneously able to trace its cellular uptake and localization by cell imaging. cDNA microarray study shows that PMNT can greatly regulate genes related to cell growth or differentiation. To the best of our knowledge, this is the first example of cell growth or differentiation promotion by polyelectrolyte material without the need of serum, thereby providing an important demonstration of degenerative biomaterial discovery through polymer design.

VUT-MK142 : a new cardiomyogenic small molecule promoting the differentiation of pre-cardiac mesoderm into cardiomyocytes

Intra-cardiac cell transplantation is a new therapy after myocardial infarction. Its success, however, is impeded by the limited capacity of donor cells to differentiate into functional cardiomyocytes in the heart. A strategy to overcome this problem is the induction of cardiomyogenic function in cells prior to transplantation. Among other approaches, recently, synthetic small molecules were identified, which promote differentiation of stem cells of various origins into cardiac-like cells or cardiomyocytes. The aim of this study was to develop and characterise new promising cardiomyogenic synthetic low-molecular weight compounds. Therefore, the structure of the known cardiomyogenic molecule cardiogenol C was selectively modified, and the effects of the resulting compounds were tested on various cell types. From this study, VUT-MK142 was identified as the most promising candidate with respect to cardiomyogenic activity. Treatment using this novel agent induced the strongest up-regulation of expression of the cardiac marker ANF in both P19 embryonic carcinoma cells and C2C12 skeletal myoblasts. The activity of VUT-MK142 on this marker superseded CgC; moreover, the novel compound significantly up-regulated the expression of other cardiac markers, and promoted the development of beating cardiomyocytes from cardiovascular progenitor cells. We conclude that VUT-MK142 is a potent new cardiomyogenic synthetic agent promoting the differentiation of pre-cardiac mesoderm into cardiomyocytes, which may be useful to differentiate stem cells into cardiomyocytes for cardiac repair. Additionally, an efficient synthesis of VUT-MK142 is reported taking advantage of continuous flow techniques superior to classical batch reactions both in yield and reaction time.

The pharmacology of regenerative medicine

Regenerative medicine is a rapidly evolving multidisciplinary, translational research enterprise whose explicit purpose is to advance technologies for the repair and replacement of damaged cells, tissues, and organs. Scientific progress in the field has been steady and expectations for its robust clinical application continue to rise. The major thesis of this review is that the pharmacological sciences will contribute critically to the accelerated translational progress and clinical utility of regenerative medicine technologies. In 2007, we coined the phrase "regenerative pharmacology" to describe the enormous possibilities that could occur at the interface between pharmacology, regenerative medicine, and tissue engineering. The operational definition of regenerative pharmacology is "the application of pharmacological sciences to accelerate, optimize, and characterize (either in vitro or in vivo) the development, maturation, and function of bioengineered and regenerating tissues." As such, regenerative pharmacology seeks to cure disease through restoration of tissue/organ function. This strategy is distinct from standard pharmacotherapy, which is often limited to the amelioration of symptoms. Our goal here is to get pharmacologists more involved in this field of research by exposing them to the tools, opportunities, challenges, and interdisciplinary expertise that will be required to ensure awareness and galvanize involvement. To this end, we illustrate ways in which the pharmacological sciences can drive future innovations in regenerative medicine and tissue engineering and thus help to revolutionize the discovery of curative therapeutics. Hopefully, the broad foundational knowledge provided herein will spark sustained conversations among experts in diverse fields of scientific research to the benefit of all.