Effect of convection on osteoblastic cell growth and function in biodegradable polymer foam scaffolds

Culture of seeded osteoblastic cells in three-dimensional osteoconductive s caffolds in vitro is a promising approach to produce an osteoinductive mate rial for repair of bone defects, However, culture of cells in scaffolds suf ficiently large to bridge critical-sized defects is a challenge for tissue engineers. Diffusion may not be sufficient to supply nutrients into large s caffolds and consequently cells may grow preferentially at the periphery un der static culture conditions. Three alternative culturing schemes that con vect media were considered: a spinner flask, a rotary vessel, and a perfusi on flow system. Poly(DF-lactic-co-glycolic acid) (PLGA) foam discs (12.7 mm diameter, 6.0 mm thick, 78.8% porous) were seeded with osteoblastic marrow stromal cells and cultured in the presence of dexamethasone and L-ascorbic acid for 7 and 14 days. Cell numbers per foam were found to be similar wit h all culturing schemes indicating that cell growth could not be enhanced b y convection, but histological analysis indicated that the rotary vessel an d Row system produced a more uniform distribution of cells throughout the F oams. Alkaline phosphatase (ALP) activity per cell was higher with culture in the flow system and spinner flask after 7 days, while no differences in osteocalcin (OC) activity per cell were observed among culturing methods af ter 14 days in culture. Based on the higher ALP activity and better cell un iformity throughout the cultured foams, the flow system appears to be the s uperior culturing method, although equally important is the fact that in no ne of the tests did any of the alternative culturing techniques underperfor m the static controls. Thus, this study demonstrates that culturing techniq ues that utilize fluid Row, and in particular the flow perfusion system, im prove the properties of the seeded cells over those maintained in static cu lture, (C) 2001 Elsevier Science Ltd. All rights Reserved.