Specific RGTA increases collagen V expression by cultured aortic smooth muscle cells via activation and protection of transforming growth factor-beta1.

Regenerating agents (RGTA) are defined as heparan sulfate mimics, which in vivo stimulate tissue repair. RGTA are obtained by controlled grafting of carboxymethyl and sulfate groups on dextran polymers. RGTA are selected in vitro, on their ability to protect heparin binding growth factors such as TGF-beta1 for example, as well as to alter extracellular matrix biosynthesis. We had reported that RGTA were able to modulate smooth muscle cell (SMC) collagen biosynthesis. Here, we demonstrated that a specific RGTA (RG-1503), altered differentially collagen type expression by post-confluent SMC and that this action involves TGF-beta1. RG-1503 decreased, by 50%, collagen I and III biosynthesis and stimulated specifically, by twofold, collagen V biosynthesis. TGF-beta1 stimulated collagen I and V by 1.5- and threefold, respectively. A synergic action for RGTA in association with TGF-beta1 was observed specifically for collagen V expression (eightfold increase). The stimulation of collagen V biosynthesis by RGTA was abolished by TGF-beta1 neutralizing antibodies. These modulations occurred at protein and mRNA levels. RG-1503 did not alter TGF-beta1 mRNA steady state level or total TGF-beta1 protein content (latent+active forms). However, RG-1503 significantly induced an elevated proportion of active TGF-beta1 form, which could result from the selective protection from proteolytic degradation of TGF-beta1 by RG-1503. These data open a rationale for understanding the stimulation of tissue repair induced by RGTA, and also, a new insight for developing drugs adapted to inhibit excess collagen deposition in smooth muscle cells associated vascular disorder, and in fibrotic diseases.