Correlation of CDC42 Activity with Cell Proliferation and Palmitate-Mediated Cell Death in Human Umbilical Cord Wharton's Jelly Derived Mesenchymal Stromal Cells.

RHO GTPases regulate cell migration, cell-cycle progression, and cell survival in response to extracellular stimuli. However, the regulatory effects of RHO GTPases in mesenchymal stromal cells (MSCs) are unclear. Herein, we show that CDC42 acts as an essential factor in regulating cell proliferation and also takes part in lipotoxic effects of palmitate in human umbilical cord Wharton's jelly derived MSCs (hWJ-MSCs). Cultured human bone marrow, adipose tissue, and hWJ-MSC derived cells had varying pro-inflammatory cytokine secretion levels and cell death rates when treated by palmitate. Strikingly, the proliferation rate of these types of MSCs correlated with their sensitivity to palmitate. A glutathione-S-transferase pull-down assay demonstrated that hWJ-MSCs had the highest activation of CDC42, which was increased by palmitate treatment in a time-dependent manner. We demonstrated that palmitate-induced synthesis of pro-inflammatory cytokines and cell death was attenuated by shRNA against CDC42. In CDC42 depleted hWJ-MSCs, population-doubling levels were notably decreased, and phosphorylation of ERK1/2 and p38 MAPK was reduced. Our data therefore suggest a mechanistic role for CDC42 activity in hWJ-MSC proliferation and identified CDC42 activity as a promising pharmacological target for ameliorating lipotoxic cell dysfunction and death.