Selective differentiation of mammalian bone marrow stromal cells cultured on three-dimensional polymer foams

Bone marrow stromal cells (BMSC) are pluripotent progenitor cells that can regenerate different skeletal tissues in response to environmental signals. In this study, we used highly porous, structurally stable three-dimensiona l polymer foams in conjunction with specific regulatory molecules to select ively differentiate mammalian BMSC into either cartilaginous or bone-like t issues. Bovine BMSC were expanded in monolayers and cultured on 5-mm-diamet er, 2-mm-thick foams made of poly(lactic-co-glycolic acid) and poly(ethylen e glycol). Constructs maintained their original size and shape for up to 4 weeks of culture and supported BMSC growth and production of extracellular matrix (ECM). By proper use of chondrogenic (dexamethasone, insulin, transf orming growth factor-pi) or osteogenic (dexamethasone, p-glycerophosphate) medium supplements, we could control whether the generated ECM was cartilag inous (containing collagen type II and sulfated glycosaminoglycans) or bone -like (containing osteocalcin, osteonectin, and mineralized foci). After 4 weeks of cultivation, cartilaginous and bone-like ECM were uniformly distri buted throughout the construct volume and respectively represented 34.2 +/- 9.3% and 12.6 +/- 3.2% of the total available area. BMSC culture on poly(l actic-co-glycolic acid)/ poly(ethylene glycol) foams provides a three-dimen sional model system to study the development of mesenchymal tissues in vitr o and has potential applications in engineering autologous grafts for skele tal tissue repair. (C) 2001 John Wiley & Sons, Inc.