In this study, the hypothesis that extracts of cementum contain substances that stimulate human gingival fibroblasts to divide and grow. Freshly extracted teeth were used that showed no signs of inflammation. The teeth were thoroughly cleaned for removal of adhering periodontal ligament, and other connective tissue and cementum was scraped with curettes in a solution containing proteinase inhibitors. Each extract was assayed for protein content. These extracts were concentrated and analyzed for mitogenic activity to human gingival fibroblasts. DNA synthesis was assayed by measurement of H3- thymidine incorporation by quiescent fibroblasts activated to divide, and cell growth determined by counting of cells over a 10 day period. Results indicate that extracts of cementum contain substances which stimulate quiescent and synchronized gingival fibroblasts to synthesize DNA and grow. 77% of the stimulatory activity resided in the acid extract whereas very little activity was present in collagenase extract. The active substance was heat stable and destroyed by trypsin. Neither platelet derived growth factor nor epidermal growth factor was detectable in the cementum extract, and extracts of human dentin and skin contained very little mitogenic activity. It is concluded that cementum contains substances capable of regulating the growth of gingival fibroblasts, and that these substances may play an important role in gingival connective tissue formation and regeneration.
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