Abstract
A phenotype switch from contractile type to proliferative type of arterial smooth muscle cells is known as dedifferentiation, but to the best of our knowledge, little is known about redifferentiation of coronary artery smooth muscle cells. The purpose of the present study was to determine in vitro culture conditions for inducing redifferentiation of coronary artery smooth muscle cells. In addition, the present study aimed to determine protein markers for detection of redifferentiated arterial smooth muscle cells. Human coronary artery smooth muscle cells (HCASMCs) were cultured in the presence or absence of growth factors, including epidermal growth factor, fibroblast growth factor-B and insulin. Protein expression and migration activity of HCASMCs were evaluated using western blotting and migration assay, respectively. In HCASMCs 5 days after 100% confluency, expression levels of α-smooth muscle actin (α-SMA), calponin, caldesmon and SM22α were significantly increased, while expression levels of proliferation cell nuclear antigen (PCNA) and S100A4 and migration activity were significantly decreased, compared with the corresponding levels just after reaching 100% confluency, indicating that redifferentiation occurred. Redifferentiation was also induced in a low-density culture of HCASMCs in the medium without growth factors. When the culture medium for confluent cells was replaced daily with fresh medium, the expression levels of α-SMA, caldesmon, SM22α, PCNA and S100A4 and migration activity were not significantly different but the calponin expression was significantly increased compared with the levels in dedifferentiated cells just after reaching 100% confluency. Thus, redifferentiation was induced in HCASMCs by deprivation of growth factors from culture medium. The results suggested that α-SMA, caldesmon and SM22α, but not calponin, are markers of redifferentiation of HCASMCs.