Overexpression of TGF-β via rAAV-Mediated Gene Transfer Promotes the Healing of Human Meniscal Lesions Ex Vivo on Explanted Menisci

Abstract

Background: Direct application of therapeutic gene vectors derived from the adeno-associated virus (AAV) might be beneficial to improve the healing of meniscal tears. Purpose: To test the ability of recombinant AAV (rAAV) to overexpress the potent transforming growth factor–β (TGF-β) in primary cultures of human meniscal fibrochondrocytes, in human meniscal explants, and in experimental human meniscal lesions as a new tool to enhance meniscal repair. Study Design: Controlled laboratory study. Methods: The effects of the candidate treatment on the proliferative and metabolic activities of meniscal cells were monitored in vitro for up to 21 days and in situ in intact and injured human menisci for up to 15 days using biochemical, immunohistochemical, histological, and histomorphometric analyses. Results: Efficient production of TGF-β via rAAV was achieved in vitro and in situ, both in the intact and injured meniscus. Application of the rAAV TGF-β vector stimulated the levels of cell proliferation and matrix synthesis (type I collagen) compared with control gene transfer in all systems tested, especially in situ in regions of poor healing capacity and in sites of meniscal injury. No adverse effects of the candidate treatment were observed at the level of osseous differentiation, as tested by immunodetection of type X collagen. Most remarkably, a significant reduction of the amplitude of meniscal tears was noted after TGF-β treatment, an effect that was associated with increased expression levels of the α–smooth muscle actin contractile marker. Conclusion: Overexpression of TGF-β via rAAV gene transfer is capable of modulating the reparative activities of human meniscal cells, allowing for the healing of meniscal lesions by convenient injection in sites of injury. Clinical Relevance: Direct gene-based approaches using rAAV have strong potential to develop new therapeutic options that aim at treating human meniscal defects.