Genetic enhancement of matrix synthesis by articular chondrocytes - Comparison of different growth factor genes in the presence and absence of interleukin-1

Objective, To determine whether articular chondrocytes express growth facto r genes delivered by adenoviral vectors and whether expression of these gen es influences matrix synthesis in the presence and absence of interleukin-l (IL-1), Methods. Monolayer cultures of rabbit articular chondrocytes were infected with recombinant adenovirus carrying genes encoding the following growth fa ctors: insulin-like growth factor 1 (IGF-1), transforming growth factor bet a 1 (TGF beta 1), and bone morphogenetic protein 2 (BMP-2), As a control, c ells were transduced with the lac Z gene. Cultures were also treated with e ach growth factor supplied as a protein. Levels of gene expression were not ed, and the synthesis of proteoglycan, collagen, and noncollagenous protein s was measured by radiolabeling, Collagen was typed by sodium dodecyl sulfa te-polyacrylamide gel electrophoresis and autoradiography, The effects of g rowth factor gene transfer on proteoglycan synthesis in the presence of IL- 1 were also measured. Results. The expression of all transgenes was high following adenoviral tra nsduction, Proteoglycan synthesis was stimulated similar to 8-fold by the B MP-2 gene and 2-3-fold by the IGF-1 gene. The effects of BMP-2 and IGF-1 ge nes were additive upon cotransduction, Synthesis of collagen and noncollage nous proteins, in contrast, was most strongly stimulated by the IGF-1 gene. In each case, collagen typing confirmed the synthesis of type II collagen. IL-1 suppressed proteoglycan synthesis by 50-60%, IGF-1 and TGF beta genes restored proteoglycan synthesis to control levels in the presence of IL-1, The BMP-2 gene, in contrast, elevated proteoglycan synthesis beyond contro l levels in the presence of IL-1. Conclusion, Transfer of growth factor genes to articular chondrocytes can g reatly increase matrix synthesis in vitro, even in the presence of the infl ammatory cytokine IL-1. This result encourages the further development of g ene therapy for the repair of damaged cartilage.