The Effect of Extracellular Matrix Stiffness on Inducing Adipogenic Differentiation of ADSCs

Extracellular matrix (ECM) is a critical biophysical factor in adipose-derived stem cells differentiation. However, the specific regulatory mechanisms and signaling pathways of Yes-associated protein (YAP) are unknown, though it plays a critically important role in ECM-induced differentiation. Here, we embedded ADSCs in collagen hydrogels with varying stiffness, elastic moduli, to be exact, of 61Pa, 217Pa, and 321Pa. The expression of adipogenic-specific genes was highly correlated with stiffness of ECM, in addition, our study has found that the levels of YAP phosphorylation were significantly altered on the 9th day after stimulation with ECM stiffness. Staining of lipid droplets with BODIPY indicates that accumulation of lipid droplets depended on hydrogel stiffness; the most pronounced accumulation was registered in 321Pa hydrogels. By inhibiting the YAP signaling pathway, we found that lipid droplet accumulation increased; thus, inhibition of YAP signaling increased YAP phosphorylation in the cytoplasm, thereby promoting accumulation of lipid droplets. In conclusion, YAP played a crucial role in regulating ECM stiffness-induced adipogenic differentiation. Adipose stem cells are differentiated in a microenvironment that offers new insights into their differentiation process.