Modulation of the Actin Filament Reorganization Alters Cellular Calcium and Surface Adhesion in Wharton's Jelly Cells

Abstract

Wharton's jelly cells (WJCs), the mesenchymal stem cells derived from umbilical cord, require extensive remodeling of actin filaments by the action of a multitude of actin-binding proteins for their biological functions of self-renewal and differentiation. In this study, molecular approaches by specific siRNAs for caldesmon (CaD), and profilin (Pro) and by gelsolin (GSN) overexpression were used to alter those gene expressions and their subsequent controls of actin polymerization in WJCs and to investigate the effects of modulation of the actin filament reorganization on cellular Ca2+ levels and surface adhesion force in the cell. Ca2+ levels were measured as the fura-2 F340/F380 fluorescence ratio in the cells. Silencing of CaD and Pro by siRNAs raised intracellular Ca2+ and rendered the resistance of decreasing Ca2+ levels by a protein kinase inhibitor, genistein. The similar change in cellular Ca2+ was also found in GSN-overexpressed cells. To determine whether changes in cellular Ca2+ associated with modulation of the actin filament reorganization will affect surface adhesion of the cell, atomic force microscopy (AFM) force-distance measurements were applied to measure the stiffness and the adhesion force in si-control, si-CaD, si-Pro, and GSN overexpressed cells. Results obtained indicate that disturbing actin filament polymerization significantly increase in cell adhesion force but do not alter the stiffness in the cells. Apparently, modulation of the actin filament polymerization might alter cellular Ca2+ and cell adhesion that is important for determining the capacity of cell differentiation in WJCs.