| One goal of regenerative medicine is to harness the body's natural healing process by helping stem cells to proliferate, migrate and differentiate. Characterization of the microenvironmental niche has led to a better understanding of the stimuli important to control stem cell function. Stem cells are regulated not only by soluble stimuli, but also the less well-studied physical microenvironment. The hypothesis that local cues from topography and stiffness regulate stem cells was tested in 3D culture. The effect of growth factors from the insulin-like growth factor (IGF) family on stem cells was also assessed. The cells used were neonatal rat ventricular fibroblasts, mouse bone marrow mesenchymal stem cells (mBMSCs), human mesenchymal stem cells (hMSCs) and mouse cardiac resident progenitor cells (RPCs). Several systems were developed using commercially available assays to determine functions such as stem cell morphology, proliferation, differentiation and migration.;The inclusion of stiff microstructures in three dimensions caused significant changes in hMSCs. Differences in cell morphology and increases in both hMSC number and cluster size result from interaction with microstructures. It is likely that the large differences in gene expression observed are due to the microstructures. Additionally, functional gene clustering analysis indicates that bone and muscle development may be delayed.;Growth factors regulate stem cells by providing chemical cues. The response of hMSCs and mouse RPCs was assessed. Insulin-like growth factor had minimal effect and the E-domain of mechano growth factor (MGF-E) no effect on proliferation of both cell types. However, migration of hMSCs was increased with both the native form of MGF-E as well as a stabilized form. Interestingly, the chemotactic effect of MGF-E was completely ameliorated due to the substitution of one serine with alanine or random scrambling of the amino acids comprising MGF-E.;Altogether, the data suggests that modifying both the physical and chemical characteristics of the microenvironment controls stem cell function. |
