ABSTRACT
OBJECTIVE: To investigate the role of the insulin-like growth factors (IGF) system during the differentiation of human pulp-derived fibroblasts (HPF). METHODS: Primary HPF were cultured for 24 days in DMEM medium with IGF-I or IGF-II (50 ng/ml each). Cell growth and morphology, alkaline phosphatase (ALP) activity, the concentration of free deoxypyridinoline (DPD), IGF-I, -II, IGFBP-2 and -3 were studied. The number of (125)I-IGF-I binding sites was estimated by Scatchard analysis. RESULTS: Light-microscopically visible nodules emerged during differentiation. Simultaneously, the ALP activity increased steadily between days 8 and 24, while the DPD concentration decreased by about 50%. The HPF produced high concentrations of IGF-II (2.00-1.30 microg/10(6) cells) but low IGF-I, IGFBP-2. IGFBP-2 was not changed, IGFBP-3 increased by 65% during differentiation. The number of IGF binding sites increased from 8,500 +/- 55 per cell (day 8) up to 22,000 +/- 570 (day 24). CONCLUSION: The increasing number of IGF-binding sites accompanied by alterations in the biochemical bone markers during the differentiation of HPF suggests an autocrine/paracrine role for the IGFs in the formation of dentinal hard tissue.
