Ischemic heart disease, also known as coronary artery disease (CAD), poses a challenge for regenerative medicine. iPSC technology might lead to a breakthrough due to the possibility of directed cell differentiation delivering a new powerful source of human autologous cardiomyocytes. One of the factors supporting proper cell maturation is in vitro culture duration. In this study, primary human skeletal muscle myoblasts were selected as a myogenic cell type reservoir for genetic iPSC reprogramming. Skeletal muscle myoblasts have similar ontogeny embryogenetic pathways (myoblasts vs. cardiomyocytes), and thus, a greater chance of myocardial development might be expected, with maintenance of acquired myogenic cardiac cell characteristics, from the differentiation process when iPSCs of myoblastoid origin are obtained. Analyses of cell morphological and structural changes, gene expression (cardiac markers), and functional tests (intracellular calcium transients) performed at two in vitro culture time points spanning the early stages of cardiac development (day 20 versus 40 of cell in vitro culture) confirmed the ability of the obtained myogenic cells to acquire adult features of differentiated cardiomyocytes. Prolonged 40-day iPSC-derived cardiomyocytes (iPSC-CMs) revealed progressive cellular hypertrophy; a better-developed contractile apparatus; expression of marker genes similar to human myocardial ventricular cells, including a statistically significant CX43 increase, an MHC isoform switch, and a troponin I isoform transition; more efficient intercellular calcium handling; and a stronger response to β-adrenergic stimulation.

Recent studies revealed that in vivo the inner blood vessel surface is lined with an endothelial surface layer at least 0.5 μm thick, which serves as an aegis, protecting the vessel wall from arteriosclerosis. Hyaluronan seems to be a constitutive component in regard to the atheroprotective properties of this surface structure. It has been shown that arterial pulsatile laminar blood flow increases the thickness of this surface layer in vivo, while it is significantly reduced at atheroprone regions with disturbed flow. This study was undertaken to reveal whether endothelial hyaluronan synthesis via hyaluronan synthase 2 (HAS2) can be changed by different shear stress conditions in vitro, especially in regard to an undisturbed, arteriallike pulsatile flow profile. Human umbilical vein endothelial cells, exposed to constant or pulsatile shear stress in a cone-and-plate system, were analysed for HAS2 expression by realtime RT-PCR and immunoblotting, and for hyaluronan by ELISA. Hyaluronan synthase 2 mRNA and protein were found to be transiently increased in a shear stress-dependent manner via the phosphatidylinositol 3-kinase-Akt pathway. Especially pulsatile, arterial-like shear stress conditions induced enzyme and hyaluronan effectively, while lower shear stress that continuously changed its direction did not induce any differences in comparison with control cultures not exposed to shear stress. These experiments provide a link between the production of a constitutive component of the endothelial surface layer by endothelial cells and blood flow.

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The concept that bone marrow (BM)-derived cells may participate in neural regeneration remains controversial, and the identity of the specific cell type(s) involved remains unknown. We recently reported that the adult murine BM contains a highly mobile population of Sca-1+Lin−CD45− cells known as very small embryonic/epiblast-like stem cells (VSELs) that express several markers of pluripotency such as Oct-4. In the BM microenvironment, these cells are kept quiescent because of epigenetic modification of certain paternally imprinted genes. However, as reported, these cells can be mobilized in mice in an experimental model of stroke and express several genes involved in neurogenesis while circulating in peripheral blood (PB). In the current work, we employed a model of toxic brain damage, which is induced by administration of kainic acid, to see not only whether VSELs can be mobilized into PB in response to this neurotoxin, but, more importantly, whether they proliferate and expand in BM tissue. We report here for the first time that brain damage leads to activation and expansion of the BM pool of quiescent VSELs, which precedes their subsequent egress into PB. Harnessing these cells in neural tissue regeneration is currently one of the challenges in regenerative medicine.