Molecular characterization of adult stem cells' adaptations to mechanical signals during adipogenic commitment

Abstract

Prevalence of obesity have increased across the years based on technological developments that supported nutritional availability and sedentary lifestyles. Restoring mechanical activity with physical exercise suppresses obesity, and mechanical loading can also be delivered passively with whole body vibrations with high frequency and low magnitude. Anabolic effects of high frequency low magnitude mechanical vibrations on adult stem cells are well identified whereas sensing mechanism of cells and their response to mechanical stimuli is largely unknown. Here, we hypothesed that daily bouts of low intensity vibrations will affect molecular, physical and ultrastructural profile of the cells and the effect will interact with the adipogenic induction. To test this hypothesis mouse bone marrow stem cell line D1 ORL UVA were subjected to mechanical vibrations (0.15g, 90 Hz, 15min/d) for 7 days to both during quiescence and adipogenic commitment. Ultrastructural changes were identified on cellular and molecular levels. Atomic force microscopy was used to characterize the changes on cell surface and significant increase was observed in cell surface height. Moreover, in order to identify the changes in cytoskeleton structure and physical properties, actin were stained with phalloidin and imaged with inverted microscope. To quantify phalloidin amount, signal intensities and physical features of the cells were measured. It was observed that mechanical stimulation and adipogenic induction affect actin content and the physical structure of the cells significantly. Molecular level analysis of cytoskeleton elements and adipogenic markers were performed with Real time PCR. Dramatic increases in adipogenic markers were detected with adipogenic induction. These results indicate that mesenchymal stem cells responds to mechanical vibrations by altering their molecular and ultrastructure during both quiescence and adipogenesis.