Synthetic integrin-binding peptides promote adhesion and proliferation of human periodontal ligament cells in vitro.

Periodontal ligament (PDL) cells have been shown to express several integrins (alphav, alpha5, beta1, beta3) that use RGD (arginine-glycine-aspartic Acid)-dependent mechanisms for the recognition and binding of their ligands. The objective of this study was to evaluate the effects of certain integrin-binding cyclic and linear synthetic RGD-containing peptides on PDL cells' adhesion, proliferation, and de novo protein synthesis in vitro. Fifth passages of normal human PDL cells established from teeth extracted from patients (ages 12 to 14) for orthodontic reasons were used for all experiments. Synthetic peptides containing the EPRGDNYR sequence in two different spatial conformations (linear and cyclic) were covalently attached to bovine serum albumin (BSA). Type I collagen, EPRGDNYR-BSA conjugates, 1:1 mixtures of type I collagen and conjugates, as well as BSA (a negative control) were coated on bacteriological plastic and evaluated for their attachment-promoting activities. In addition, the effects of these substrates on cell proliferation were evaluated by [3H]thymidine incorporation by the PDL cells. For attachment and spreading, the cyclic forms of EPRGDNYR-BSA conjugate and type I collagen were most potent, followed by linear EPRGDNYR-BSA conjugate. The effects of all collagen/conjugate mixtures were equivalent to that of type I collagen except for the collagen/linear EPRGDNYR-BSA mixture, which was less potent. The cyclic EPRGDNYR-BSA conjugate was the most effective substrate to stimulate cell proliferation, and it was followed in potency by the linear peptide-BSA conjugate. Collagen alone did not stimulate [3H]thymidine incorporation above the control level. Mixtures of collagen with all of the conjugates showed stimulatory effects similar to that of the cyclic peptide-BSA conjugate. No significant differences in de novo protein synthesis were detected. These results suggest that the synthetic RGD-containing peptides attached to a carrier are potent ligands for the human PDL cells, and that they could provide a basis for the development of new strategies aimed at the regeneration of the periodontium.