rAAV-mediated overexpression of FGF-2 promotes cell proliferation, survival, and α-SMA expression in human meniscal lesions

Abstract

Meniscal tears are a common problem in sports medicine. Direct application of therapeutic vectors derived from the adeno-associated virus might be beneficial to enhance meniscal repair. We tested the hypothesis that overexpression of fibroblast growth factor 2 (FGF-2) through recombinant adeno-associated virus (rAAV) vectors leads to detectable metabolic changes in human meniscal fibrochondrocytes and in human meniscal defects. rAAV-mediated gene transfer was investigated for its ability to promote FGF-2 secretion in human meniscal fibrochondrocytes in vitro, in intact human meniscal explants in situ, and in experimentally created human meniscal lesions. Effects of the treatment on cell proliferation and survival, extracellular matrix synthesis, and expression of the α-smooth muscle actin (α-SMA) contractile marker were monitored using biochemical, immunohistochemical, histological, and histomorphometric analyses. Efficient production of FGF-2 through rAAV could be achieved in vitro and in situ, both in the intact and injured meniscus. Application of the candidate FGF-2 vector allowed for enhanced cell proliferation and survival compared with control transduction, in particular in areas with poor healing capacity and in sites of injury, consistent with the mitogenic activities of the growth factor. Remarkably, a significant reduction of the amplitude of meniscal tears was noted after FGF-2 treatment, with increased levels of α-SMA expression. In contrast, there was no significant stimulation of synthesis of the major extracellular matrix components when the candidate vector was applied and instead, a decrease in the matrix/DNA contents was reported, in good agreement with the properties of FGF-2. Such a direct gene-based approach may have value in options aiming at treating human meniscal defects.