Hepatocyte growth factor/scatter factor modulates cell motility, proliferation, and proteoglycan synthesis of chondrocytes.

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor that promotes proliferation, motility, and morphogenesis in epithelial cells. Recently the HGF receptor, c-met protooncogene product, has been shown to be expressed in developing limb buds (Sonnenberg, E., D. Meyer, M. Weidner, and C. Birchmeiyer, 1993. J. Cell Biol. 123: 223-235), suggesting that some populations of mesenchymal cells in limb buds respond to HGF/SF. To test the possibility that HGF/SF is involved in regulation of cartilage development, we isolated chondrocytes from knee joints and costal cartilages of 23-d embryonic and 4-wk-old rabbits, and analyzed the effects of HGF/SF on migration and proliferation of these cells. We found that HGF/SF stimulated migration of cultured articular chondrocytes but did not scatter limb mesenchymal fibroblasts or synovial fibroblasts in culture. HGF/SF also stimulated proliferation of chondrocytes; a maximum three-fold stimulation in DNA synthesis was observed at the concentration of 3 ng/ml of HGF/SF. Moreover, HGF/SF had the ability to enhance proteoglycan synthesis in chondrocytes. The responsiveness of chondrocytes to HGF/SF was also supported by the observation that they expressed the HGF/SF receptor. Addition of the neutralizing antibody to rat HGF/SF affected neither DNA synthesis nor proteoglycan synthesis in rat chondrocytes, suggesting a paracine mechanism of action of HGF/SF on these cells. In situ hybridization analysis showed that HGF/SF mRNA was restrictively expressed in the areas of future joint regions in developing limb buds and in the intercostal spaces of developing costal cartilages. These findings suggest that HGF/SF plays important roles in cartilage development through its multiple activities.

Assessment of interleukin-6 in the pathogenesis of periodontal disease.

This study was performed to investigate the aspects of interleukin-6 (IL-6) production in both the gingival tissue and the peripheral blood of patients with periodontal disease and of periodontally healthy subjects. In addition, IL-6 expression in human gingival tissues was studied by reverse transcription-polymerase chain reaction analysis and by immunoperoxidase staining with anti-IL-6 monoclonal antibody. The levels of IL-6 in the culture supernatants from peripheral blood mononuclear cells (PBMC) stimulated with lipopolysaccharide and in serum were examined by bioassay. We detected IL-6 mRNA expression in all inflamed gingival tissues (17/17) examined and in 2/4 in healthy gingival tissues. IL-6 protein was detected mainly in endothelial cells, fibroblasts, and macrophages but not in the area containing T or B cells in the inflamed gingival tissues, and was not detected at all in healthy gingival tissues. There was no significant difference between the subjects with periodontal disease and those with healthy gingival tissues either in serum IL-6 levels or in the amount of IL-6 produced by PBMC. These results suggest that non-lymphoid cells in inflamed gingival tissue may contribute to the pathogenesis of periodontal disease via IL-6 production, and that the IL-6 produced in gingival tissue may not reflect the IL-6 levels in peripheral blood.