Substrate elasticity regulates vascular endothelial growth factor A (VEGFA) expression in adipose-derived stromal cells: Implications for potential angiogenesis

Adipose-derived stromal cells (ASCs) have potential in bioengineering angiogenesis due to their paracrine role in supporting endothelial tubulogenesis and vascular network formation. However, the precise mechanism of the inner angiogenic capacity of ASCs determined by the biophysical properties of the extracellular matrix needs to be further elucidated. In the current study, we fabricated two silicon-based elastomer polydimethylsiloxane (PDMS) substrates with different stiffnesses (stiff substrate, E = 195 kPa and soft substrate, E = 15 kPa) and found there were cytoskeletal changes in ASCs in response to different substrate stiffnesses. We then showed the expression of vinculin in focal adhesion plaques was enhanced and the nuclear translocation of β-catenin signaling was increased in ASCs on the stiff substrate relative to those on the soft substrate. We next used bioinformatics and found the downstream proteins of β-catenin signaling had binding sites in the promoter of vascular endothelial growth factor A (VEGFA), which is responsible for angiogenesis; then, we further confirmed the enhanced endogenous VEGFA expression in ASCs on the stiff substrate relative to that on the soft substrate. Finally, by using ectogenic VEGFA, we showed the stiff substrate could promote angiogenesis of ASCs in the form of more ring-like formations in 2D and vessel-like structure formations in 3D under VEGFA induction compared to that of the soft substrate. This study not only indicates the inner angiogenic capacity of ASCs but also elucidates the influence of substrate elasticity on ASC differentiation in bioengineering angiogenesis.