Restoration of the extracellular matrix in human osteoarthritic articular cartilage by overexpression of the transcription factor SOX9

Objective. Human osteoarthritis (OA) is characterized by a pathologic shift in articular cartilage homeostasis toward the progressive loss of extracellular matrix (ECM). The purpose of this study was to investigate the ability of rAAV-mediated SOX9 overexpression to restore major ECM components in human OA articular cartilage. Methods. We monitored the synthesis and content of proteoglycans and type II collagen in 3-dimensional cultures of human normal and OA articular chondrocytes and in explant cultures of human normal and OA articular cartilage following direct application of a recombinant adeno-associated virus (rAAV) SOX9 vector in vitro and in situ. We also analyzed the effects of this treatment on cell proliferation in these systems. Results. Following SOX9 gene transfer, expression levels of proteoglycans and type II collagen increased over time in normal and OA articular chondrocytes in vitro. In situ, overexpression of SOX9 in normal and OA articular cartilage stimulated proteoglycan and type II collagen synthesis in a dose-dependent manner. These effects were not associated with changes in chondrocyte proliferation. Notably, expression of the 2 principal matrix components could be restored in OA articular cartilage to levels similar to those in normal cartilage. Conclusion. These data support the concept of using direct, rAAV-mediated transfer of chondrogenic genes to articular cartilage for the treatment of OA in humans

Improved Tissue Repair in Articular Cartilage Defects in Vivo by rAAV-Mediated Overexpression of Human Fibroblast Growth Factor 2

Therapeutic gene transfer into articular cartilage is a potential means to stimulate reparative activities in tissue lesions. We previously demonstrated that direct application of recombinant adeno-associated virus (rAAV) vectors to articular chondrocytes in their native matrix in situ as well as sites of tissue damage allowed for efficient and sustained reporter gene expression. Here we test the hypothesis that rAAV-mediated overexpression of fibroblast growth factor 2 (FGF-2), one candidate for enhancing the repair of cartilage lesions, would lead to the production of a biologically active factor that would facilitate the healing of articular cartilage defects. In vitro, FGF-2 production from an rAAV-delivered transgene was sufficient to stimulate chondrocyte proliferation over a prolonged period of time. In vivo, application of the therapeutic vector significantly improved the overall repair, filling, architecture, and cell morphology of osteochondral defects in rabbit knee joints. Differences in matrix synthesis were also observed, although not to the point of statistical significance. This process may further benefit from cosupplementation with other factors. These results provide a basis for rAAV application to sites of articular cartilage damage to deliver agents that promote tissue repair