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Brugada syndrome (BrS) is one of the major causes of sudden cardiac death in young people, while the underlying mechanisms are not completely understood. Here, we investigated the pathophysiological phenotypes and mechanisms using induced pluripotent stem cell-derived cardiomyocytes from two BrS patients (BrS-CMs) carrying a heterozygous SCN5A mutation p.S1812X. Compared to cardiomyocytes derived from healthy controls (Ctrl-CMs), BrS-CMs displayed a 50% reduction of INa density, a 69.5% reduction of NaV1.5 expression, and the impaired localization of NaV1.5 and connexin 43 at the cell surface. BrS-CMs exhibited reduced action potential upstroke velocity and conduction slowing. The Ito in BrS-CMs was significantly augmented, and the ICaL window current probability was increased. Our data indicate that the electrophysiological mechanisms underlying arrhythmia in BrS-CMs may involve both depolarization and repolarization disorders. Cilostazol and milrinone showed dramatic inhibitions of Ito in BrS-CMs and alleviated the arrhythmic activity, suggesting their therapeutic potential for BrS patients.

Spermatogonial stem cells (SSCs) constitute one of the most important stem cell systems in the adult body. SSCs are unipotent and respond for spermatogenesis in the male as they can only differentiate into sperms within the testicular niche. The long-term culture of SSCs without loss of their properties provides the opportunity to develop therapeutic strategies and re-initiate spermatogenesis for the patients who become infertile after cancer therapy. Moreover, SSCs can be spontaneously reprogrammed into pluripotent germline stem cells (GSCs) similar to embryonic stem cells (ESCs) when they are removed from their in vivo niche and cultured in vitro under specific conditions. The advantage of pluripotent GSCs over induced pluripotent stem cells is that conversion of SSCs into pluripotent GSCs does not require addition of genes using the virus system, which may avoid unpredictable genetic dysfunction. In addition, this may also circumvent ethical problems associated with human ESCs. The ability to generate patient-specific pluripotent GSCs for autologous transplantation provides the opportunity for cell replacement therapy without the need for immunosuppressant. In this review, we discuss the origin, properties and regenerative potential of SSCs. We summarize recent research findings regarding the mechanisms that regulate the self-renewal of SSCs. We believe that studying the biology of SSCs provides us important information to better understand male fertility. Furthermore, we address the contribution of SSCs and pluripotent GSCs to stem cell-based therapy for infertility treatment as well as for organ regeneration in the future.

Aims Induced pluripotent stem cells (iPSCs) provide a unique opportunity for the generation of patient-specific cells for use in disease modelling, drug screening, and regenerative medicine. The aim of this study was to compare human-induced pluripotent stem cells (hiPSCs) derived from different somatic cell sources regarding their generation efficiency and cardiac differentiation potential, and functionalities of cardiomyocytes. Methods and results We generated hiPSCs from hair keratinocytes, bone marrow mesenchymal stem cells (MSCs), and skin fibroblasts by using two different virus systems. We show that MSCs and fibroblasts are more easily reprogrammed than keratinocytes. This corresponds to higher methylation levels of minimal promoter regions of the OCT4 and NANOG genes in keratinocytes than in MSCs and fibroblasts. The success rate and reprogramming efficiency was significantly higher by using the STEMCCA system than the OSNL system. All analysed hiPSCs are pluripotent and show phenotypical characteristics similar to human embryonic stem cells. We studied the cardiac differentiation efficiency of generated hiPSC lines ( n = 24) and found that MSC-derived hiPSCs exhibited a significantly higher efficiency to spontaneously differentiate into beating cardiomyocytes when compared with keratinocyte-, and fibroblast-derived hiPSCs. There was no significant difference in the functionalities of the cardiomyocytes derived from hiPSCs with different origins, showing the presence of pacemaker-, atrial-, ventricular- and Purkinje-like cardiomyocytes, and exhibiting rhythmic Ca2+ transients and Ca2+ sparks in hiPSC-derived cardiomyocytes. Furthermore, spontaneously and synchronously beating and force-developing engineered heart tissues were generated. Conclusions Human-induced pluripotent stem cells can be reprogrammed from all three somatic cell types, but with different efficiency. All analysed iPSCs can differentiate into cardiomyocytes, and the functionalities of cardiomyocytes derived from different cell origins are similar. However, MSC-derived hiPSCs revealed a higher cardiac differentiation efficiency than keratinocyte- and fibroblast-derived hiPSCs.