Stimulation of chondrocytes in vitro by gene transfer with plasmids coding for epidermal growth factor (hEGF) and basic fibroblast growth factor (bFGF).

Human epidermal growth factor (hEGF) and basic fibroblast growth factor (bFGF) influence critical characteristics of chondrocytes. The effects on metabolism and differentiation were evaluated following transfection using specific plasmids coding for both cytokines. Chondrocytes were isolated from femoral head cartilage of patients undergoing a hip arthroplasty for femoral neck fracture. Following collagenase-digestion, cells were cultured in monolayers, and cell proliferation, glucosaminoglycan-production and collagen type II expression were monitored 10 days after isolation. Addition of recombinant hEGF and bFGF resulted in a significant increase in cell proliferation and glucosaminoglycan production. Chondrocytes were transfected with vectors coding for either hEGF or bFGF and the production of these proteins was measured in supernatants by ELISA. Expression kinetics showed different patterns: hEGF was detectable 2.5 days following transfection and peaked at day 5.5, whereas bFGF-production reached its maximum 1.5 days after transfection, declining thereafter. Chondrocytes endogenously produced significant amounts of bFGF within 5 days following isolation. Proliferation of hEGF-transfected cells increased up to 81%; bFGF-transfection caused an increase up to 76%. Similarly, glucosaminoglycan-production was enhanced up to 120% by hEGF-transfection and 37% by bFGF transfection, respectively. Collagen type II production decreased following transfection with both plasmids. Temporary in vitro gene transfer of the growth factors hEGF and bFGF provides a method to stimulate chondrocyte proliferation and induces signs of dedifferentiation, which would limit a reasonable clinical application.