Recombinant connective tissue growth factor modulates porcine skin fibroblast gene expression

Connective tissue growth factor (CTGF) is a 38 Kda cysteine-rich, heparin-binding peptide that has been implicated in several normal and abnormal physiological processes. CTGF has been shown to be induced by transforming growth factor-beta. Previous studies in our pig model of skin wound healing showed a coordinate expression of transforming growth factor-beta and CTGF during the healing process. To better understand the function of CTGF during wound healing, normal porcine fibroblasts were isolated from skin samples from SPF Yorkshire pigs. At fourth passage the cells were cultured in Dulbecco's modified Eagle's medium supplemented with fetal calf serum and at 80% confluence the medium was replaced with supplemented serum-free medium. After a further 24 hours, cells were treated with 0, 10, 25, 50, 100, and 500 ng/ml of 38 Kda or 16-20 Kda (C-terminal truncated form) recombinant expressed human CTGF for 24 hours or treated with 100 ng/ml for 0, 12, 24, and 48 hours. Subsequently, CTGF effects on cell DNA synthesis and mRNA levels for a subset of relevant molecules were assessed. The results showed that in cells treated with 38 Kda rhCTGF, mRNA levels for types I and III collagen, fibromodulin, and basic fibroblast growth factor were significantly up-regulated, but mRNA levels for HSP47, decorin, biglycan, and versican were not significantly altered. mRNA levels for CTGF were also significantly increased, indicating autoregulation of expression. However, mRNA levels for transforming growth factor-beta, inteleukins 1 and 6, tumor necrosis factor-alpha, and nerve growth factor did not change. Interestingly, mRNA levels for the tissue inhibitors of metalloproteinase-1, -2, -3 and -4 were observed to significantly increase, but in contrast, mRNA levels for matrix metalloproteinases-1, -2, -9 were not significantly altered by exposure of the cells to the 38 Kda form of CTGF. In addition, DNA synthesis was augmented in the presence of 38 Kda rhCTGF. However, the truncated 16-20 Kda form of rhCTGF appeared to have none of these effects on porcine fibroblasts. These results indicate that in order to induce changes in porcine fibroblasts a molecule with an intact C-terminal domain is required, and that CTGF regulates porcine fibroblast extracellular matrix molecule, growth factor, and proteinase inhibitor gene expression without apparently affecting matrix metalloproteinase mRNA levels. These findings suggest that CTGF contributes to the anabolic environment during skin wound healing via selective modulation of fibroblast proliferation and changes to gene expression.