Flow perfusion culture induces the osteoblastic differentiation of marrow stromal cell-scaffold constructs in the absence of dexamethasone

Flow perfusion culture of scaffold/cell constructs has been shown to enhance the osteoblastic differentiation of rat bone marrow stromal cells (MSCs) over static culture in the presence of osteogenic supplements including dexamethasone. Although dexamethasone is known to be a powerful induction agent of osteoblast differentiation in MSCs, we hypothesized that the mechanical shear force caused by fluid flow in a flow perfusion bioreactor would be sufficient to induce osteoblast differentiation in the absence of dexamethasone. In this study, we examined the ability of MSCs seeded on titanium fiber mesh scaffolds to differentiate into osteoblasts in a flow perfusion bioreactor in both the presence and absence of dexamethasone. Scaffold/cell constructs were cultured for 8 or 16 days and osteoblastic differentiation was determined by analyzing the constructs for cellularity, alkaline phosphatase activity, and calcium content as well as media samples for osteopontin. For scaffold/cell constructs cultured under flow perfusion, there was greater scaffold cellularity, alkaline phosphatase activity, osteopontin secretion, and calcium deposition compared with static controls, even in the absence of dexamethasone. When dexamethasone was present in the cell culture medium under flow perfusion conditions, there was further enhancement of osteogenic differentiation as evidenced by lower scaffold cellularity, greater osteopontin secretion, and greater calcium deposition. These results suggest that flow perfusion culture alone induces osteogenic differentiation of rat MSCs and that there is a synergistic effect of enhanced osteogenic differentiation when both dexamethasone and flow perfusion culture are used. (C) 2005 Wiley Periodicals, Inc.