Both biochemical and mechanical cues
could regulate the
function
of stem cells, but the interaction mechanism of their signaling pathway
remains unclear, especially in the three-dimensional (3D) culture
mode. Higher matrix stiffness promotes osteogenic differentiation
of stem cells, and bone morphogenic protein-2 (BMP-2) has been clinically
applied to promote bone regeneration. Here, the crosstalk of extracellular
mechanical signals on BMP-2 signaling was investigated in rat bone
marrow stromal cells (rMSCs) cultured inside cryogels with interconnective
pores. Stiff cryogel independently promoted osteogenic differentiation
and enhanced the autocrine secretion of BMP-2, thus stimulating increased
phosphorylation levels of the Smad1/5/8 complex. BMP-2 mimetic peptide
(BMMP) and high cryogel stiffness jointly guided the osteogenic differentiation
of rMSCs. Inhibition of rho-associated kinase (ROCK) by Y-27632 or
inhibition of nonmuscle myosin II (NM II) by blebbistatin showed that
osteogenesis induction by BMP-2 signaling, as well as autocrine secretion
of BMP-2 and phosphorylation of the Smad complex, requires the involvement
of cytoskeletal tension and ROCK pathway signaling. An interconnective
microporous cryogel scaffold promoted rMSC osteogenic differentiation
by combining matrix stiffness and BMMP, and it accelerated critical
cranial defect repair in the rat model.