Human adipose-derived adult stem cells upregulate palladin during osteogenesis and in response to cyclic tensile strain.

Cell morphology may be an important stimulus during differentiation of human adipose-derived adult stem (hADAS) cells, but there are limited studies that have investigated the role of the cytoskeleton or associated proteins in hADAS cells undergoing differentiation. Palladin is an actin-associated protein that plays an integral role in focal adhesion and cytoskeleton organization. In this study we show that palladin was expressed by hADAS cells and was modulated during osteogenic differentiation and in response to cyclic tensile strain. Human ADAS cells expressed the 90- and 140-kDa palladin isoforms and upregulated expression of both isoforms after culture in conditions that promoted osteogenesis. Palladin mRNA expression levels were also increased in hADAS cells subjected to cyclic tensile strain. Knockdown of the palladin gene during osteogenesis resulted in decreased actin stress fibers and decreased protein levels of Eps8, an epidermal growth factor receptor tyrosine kinase that colocalizes with actin. Silencing the palladin gene, however, did not affect hADAS cells' commitment down the osteogenic lineage.