Metabolic Activities and Chondrogenic Differentiation of Human Mesenchymal Stem Cells Following Recombinant Adeno-Associated Virus-Mediated Gene Transfer and Overexpression of Fibroblast Growth Factor 2

The genetic manipulation of bone marrow-derived mesenchymal stem cells (MSCs) is an attractive approach to produce therapeutic platforms for settings that aim at restoring articular cartilage defects. Here, we examined the effects of recombinant adeno-associated virus (rAAV)-mediated overexpression of human fibroblast growth factor 2 (hFGF-2), a mitogenic factor also known to influence MSC differentiation, upon the proliferative and chondrogenic activities of human MSCs (hMSCs) in a three-dimensional environment that supports chondrogenesis in vitro. Prolonged, significant FGF-2 synthesis was noted in rAAV-hFGF-2-transduced monolayer and aggregate cultures of hMSCs, leading to enhanced, dose-dependent cell proliferation compared with control treatments (rAAV-lacZ transduction and absence of vector administration). Chondrogenic differentiation (proteoglycans, type-II collagen, and SOX9 expression) was successfully achieved in all types of aggregates, without significant difference between conditions. Most remarkably, application of rAAV-hFGF-2 reduced the expression of type-I and type-X collagen, possibly due to increased levels of matrix metalloproteinase-13, a key matrix-degrading enzyme. FGF-2 overexpression also decreased mineralization and the expression of osteogenic markers such as alkaline phosphatase, with diminished levels of RUNX-2, a transcription factor for osteoblast-related genes. Altogether, the present findings show the ability of rAAV-mediated FGF-2 gene transfer to expand hMSCs with an advantageous differentiation potential for future, indirect therapeutic approaches that aim at treating articular cartilage defects in vivo.