Inhibition of non-muscle myosin II leads to G0/G1 arrest of Wharton's jelly-derived mesenchymal stromal cells.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have remarkable clinical potential for cell-based therapy. Wharton's jelly-derived mesenchymal stromal cells (WJ-MSCs) from umbilical cord share unique properties with both embryonic and adult stem cells. MSCs are found at low frequency in vivo, and their successful therapeutic application depends on rapid and efficient large-scale expansion in vitro. Non-muscle myosin II (NMII) has pivotal roles in different cellular activities, such as cell division, migration and differentiation. We performed this study to understand the role of NMII in proliferation and cell cycle progression in WJ-MSCs. METHODS: WJ-MSCs were cultured in the presence of blebbistatin, and cell cycle analysis was performed using flow cytometry, proliferation kinetics, senescence assay and gene expression profile using polymerase chain reaction array. RESULTS: When cultured in the presence of blebbistatin, an inhibitor of NMII adenosine triphosphatase activity, WJ-MSCs exhibited dose-dependent reduction in proliferative potential along with increase in cell size and induction of early senescence. Inhibition of NMII activity also affected cell cycle progression in WJ-MSCs and led to an increase in the percentage of cells in G0/G1 phase with a corresponding reduction in the percentage of cells in G2/M phase. Blebbistatin-induced G0/G1 arrest of WJ-MSCs was further associated with up-regulation of cell cycle inhibitory genes CDKN1A, CDKN2A and CDKN2B and down-regulation of numerous genes related to progression through S and M phases of the cell cycle. CONCLUSIONS: Our study demonstrates that inhibition of NMII activity in WJ-MSCs leads to G0/G1 arrest and alteration in the expression levels of certain key cell cycle-related genes.