Introduction: Mesenchymal stem cells (MSCs), when housed within an appropriate scaffold and stimulated by specific chondrogenic signals have been considered for potential application in tissue reconstruction. Tissue engineering principles are currently being applied to cell-based efforts to restore damaged or diseased tissues. The basic requirements for these efforts are cells capable of producing a functional matrix, an appropriate scaffold for transplantation and support of the cell-laden graft, with iatrogenic or autogenous bioactive molecules to drive the processes of cellular differentiation and maturation. Methods: MSCs were seeded in experimental groups consisting of poly-L-lactic acid (PLA) constructs and PLA/alginate amalgam constructs with and without recombinant human transforming growth factor-b1 (TGF-b1). Chondrogenesis of the PLA and the PLA/alginate amalgam cultures was assessed at weekly intervals by histology, immunohistochemistry, scanning electron microscopy, sulfate incorporation and RT-PCR to characterize the in vitro chondrogenic differentiation profile and the generation of fibrous tissue production within the matrix. Results/Discussion: Cartilage formation was apparent in the TGF-b1 treated groups, on the basis of chondrocyte specific gene expression assessed by (RT-PCR), as well as histological and immunohistochemical analysis in both the plain PLA and the PLA/alginate amalgam. Cellular proliferation, localized by staining for proliferating cell nuclear antigen (PCNA) and 5-bromo-2’deoxyuridine (BrdU), was found restricted to the perimeter regions of the three-dimensional constructs. In the plain PLA constructs, immunohistochemistry revealed this region of cellular proliferation to be associated, by immunohistochemistry, with a collagen type I- rich fibrous layer. This represents a potential barrier between the host tissue and the engineered neo-cartilage. In contrast, the three-dimensional construct fabricated using the PLA/alginate amalgam showed no signs of fibrous tissue deposition, and thus represents the first step towards the design of specific implants to direct cellular proliferation, promote differentiation and prevent inappropriate matrix deposition to reconstruct tissues lost to disease and/or trauma.
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