Three-dimensional cartilage formation by bone marrow-derived cells seeded ion polylactide/alginate amalgam

Bone marrow-derived cells are considered as candidate cells for cartilage t issue engineering by virtue of their ability to undergo chondrogenesis in v itro when cultured in high density or when embedded within a three-dimensio nal matrix in the presence of growth factors. This study evaluated the pote ntial of human bone marrow-derived cells for cartilage tissue engineering b y examining their chondrogenic properties within a three-dimensional amalga m scaffold consisting of the biodegradable polymer, poly-L-lactic acid (PLA ) alone, and with the polysaccharide gel, alginate. Cells were suspended ei ther in alginate or medium and loaded into porous PLA blocks. Alginate was used to improve cell loading and retention within the construct, whereas th e PLA polymeric scaffold provided appropriate mechanical support and stabil ity to the composite culture. Cells seeded in the PLA/alginate amalgams and the plain PLA constructs were treated with different concentrations of rec ombinant human transforming growth factor-beta1 (TGF-beta1) either continuo usly (10 ng/mL) or only for the initial 3 days of culture (50 ng/mL). Chond rogenesis was assessed at weekly intervals with cultures maintained for up to 3 weeks. Histological and immunohistochemical analysis of the TGF-beta1- treated PLA/alginate amalgam and PLA constructs showed development of a car tilaginous phenotype from day 7 to day 21 as demonstrated by colocalization of Alcian blue staining with collagen type II and cartilage proteoglycan l ink protein. Expression of cartilage specific genes, including collagen typ es II and IX, and aggrecan, was detected in TGF-beta1-treated cultures by r everse transcription-polymerase chain reaction analysis. The initiation and progression of chondrogenic differentiation within the polymeric macrostru cture occurred with both continuous and the initial 3-day TGF-beta1 treatme nt regimens, suggesting that key regulatory events of chondrogenesis take p lace during the early period of cell growth and proliferation. Scanning ele ctron microscopy revealed abundant cells with a rounded morphology in the P LA/alginate amalgam. These findings suggest that the three-dimensional PLA/ alginate amalgam is a potential candidate bioactive scaffold for cartilage tissue engineering applications. (C) 2001 John Wiley & Sons, Inc.