Porous ceramic vehicles for rat-marrow-derived (Rattus norvegicus) osteogenic cell delivery: effects of pre-treatment with fibronectin or laminin.

Cultured marrow-derived rat (Rattus norvegicus) mesenchymal cells can differentiate into osteoblasts when combined with an appropriate delivery vehicle and implanted in vivo. Porous ceramics have been successfully utilized for this purpose; however, the cellular interactions with these ceramics have not been delineated, and the optimal conditions for cell loading have not been determined. We have investigated the effects of ceramic pre-treatment with fibronectin and laminin on culture-expanded marrow mesenchymal cells. Scanning electron microscopic imaging was used for assessment of the interaction of these osteogenic cells with treated and untreated ceramic surfaces. The capability of pre-treated and untreated ceramics to retain an inoculum of these cells was determined by quantitation of [3H]thymidine-labeled cells added to ceramics and implanted subcutaneously into syngeneic rat hosts. Finally, the rate of bone formation in ceramic-cell composites, at harvest times ranging from 1 to 5+ wk, was determined histologically. Scanning electron microscopic images indicate that ceramics pre-treated with either laminin or fibronectin provide a surface on which marrow mesenchymal cells spread. Fibronectin and laminin increase cell retention within coated ceramics compared with uncoated controls. Furthermore, morphological evidence of osteogenesis is observed earlier in coated than in untreated ceramics. These observations indicate that cell attachment proteins, such as fibronectin, may augment bone formation in cell-ceramic composites by promoting the attachment and retention of osteoprogenitor cells within ceramic pores.