Ovine fetal mesenchymal stem cell differentiation to cardiomyocytes, effects of co-culture, role of small molecules; reversine and 5-azacytidine.

The aim of the present study was to investigate the effect of small molecules: Reversine and 5-azacytidine (5-AC), in an indirect co-culture condition with the cardiac fibroblasts as well as non co-culture condition, in order to explore the effect of such molecules in the process of differentiation of the ovine bone-marrow mesenchymal stem cells (BM-MSCs) towards cardiomyocytes. Surface antigens of the isolated cells were analysed using flow-cytometry. In addition, following to three passages cells were examined for their differentiation capacity into osteocytes and adipose cells, in order to ensure the mesenchymal origin of the stem cells. Six types of treatments were carried out in the present investigation, such that, in the first treatment BM-MSCs were cultured for 28 days as control group; the second treatment was composed of culturing ovine fetal cardiac fibroblasts on inserts, aiming to use these inserts for culturing plates which were seeded with BM-MSCs (Chamber group). As the third treatment, BM-MSCs were supplemented with 10-μM 5-AC and incubated for 48 h. The fourth treatment was composed of supplementing BM-MSCs with the 600-nM reversine, incubated for 48 h, and subsequently the incubation was further extended for another 48 h in the presence of 5-AC. The fifth treatment was composed of supplementing the chamber group with 10-μM 5-AC and incubation for 48 h, and the last or the sixth treatment was such that chamber group was supplemented with 600-nM reversine and an incubation period of 48 h. Following to the incubation, medium was replaced with 10-μM 5-AC and further incubated for another round of 48 h. In all treatments, following to addition of the small molecules incubations were carried out for 28 days; same as controls. Expression of cardiac alpha-actinin was analysed by immunocytochemistry. BM-MSCs have shown to express CD44 and CD166 along with a weak expression of the CD90, CD34, in addition to CD45. Multilineage differentiation has indicated that BM-MSCs could differentiate into adipose and osteocytes cells as well. In the treatment 4 it was observed that FGF signalling involved genes and all cardiac-related genes (ANP, MYH6 and Troponin I) were significantly expressed, except connexin 43 compared to other treatments. All treatments received small molecules, either alone or as a co-culture were seen to express sarcomeric alpha-actinin. This finding was partially supported by immunocytochemistry. These results validate that reversine and 5-AC have an effect on ovine BM-MSC differentiation into cardiomyocytes.