Dynamic compression regulates cell-matrix adhesions and intra cellular signaling proteins of human mesenchymal stem cells In 3d collagen environment

Abstract

BACKGROUND: Mechanical signal is an important factor influencing stem cell behaviour. However, little effort is made in understanding how cells sense and convert these mechanical signals into particular biochemical responses. Cell-matrix adhesions, which are the linkages between cells and their extracellular matrix (ECM), serve as the major “mechansensors” of the cells. Our objective is to test the hypothesis that dynamic compression of human mesenchymal stem cells (hMSCs) embedded in 3D collagen environment lead to changes in cell-matrix adhesions and intracellular signaling proteins. METHODS: We embedded hMSCs in 3D collagen environment using collagen encapsulation technique. We developed a micromanipulator-based loading system and imposed dynamic compression to the hMSCs embedded in collagen at 1Hz and 10% peak-to-peak cyclic deformation. We then stained tissue sections for integrin α5 and fibronectin and viewed them using confocal microscope. RESULTS: We observed that hMSCs recycled integrin α5 from intracellular pool to cell surface after 9-hour dynamic compression. We also found colocalization of integrin α5 and fibronectin in these loaded constructs. Interestingly, cells formed elongated α5 integrin–containing adhesions after daily 5-hour compression for 7 days. CONCLUSION: Our results suggested that hMSCs in 3D collagen gels adapt to dynamic loading by increasing integrin α5 surface expression which leads to subsequent formation of α5 integrin–containing adhesions. We will do flow cytometry to test whether increase of α5 surface expression correlates with loading duration and magnitude. We will also test whether focal adhesion kinase (FAK) involves in this adaptation process.