Submitted on February 16, 2007
Accepted on August 6, 2007
Human Adipose-Derived Adult Stem Cells Upregulate Palladin During Osteogenesis and in Response to Cyclic Tensile Strain
Michelle E. Wall1, Andrew Rachlin2, Carol Otey3, and Elizabeth G. Loboa1*
1 Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Raleigh, North Carolina, United States
2 Cell and Molecular Physiology, UNC-Chapel Hill, Chapel Hill, North Carolina, United States
3 Univ. North Carolina, Chapel Hill, United States
* To whom correspondence should be addressed. E-mail: egloboa{at}ncsu.edu.
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. Here 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 kD 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 EGF receptor tyrosine kinase that co-localizes with actin. Silencing the palladin gene, however, did not affect hADAS cells commitment down the osteogenic lineage.
