The bioactivity of transforming growth factor-β1 can be regulated via binding to dermal collagens in mink lung epithelial cells

SummaryBackgroundThe bioactivity of transforming growth factor-β1 (TGF-β1) is known to be regulated by some components of the extracellular matrix (ECM), but the possibility that it might be regulated by collagen, the richest ECM component, has never been previously reported.ObjectiveThis study was designed to investigate the possible role that different types of collagens might play on the bioactivity of TGF-β1.MethodsThe interaction of 125I–TGF-β1 and various types of collagen was examined by a solid-phase assay and by a co-precipitation assay. The bioactivity of TGF-β1 was assessed by a proliferation assay in which mink lung epithelial cells were examined in the presence and absence of collagens.ResultsActivated native dimeric TGF-β1 bound to type I collagen in a dose-dependent manner, while monomeric TGF-β1 bound poorly to the collagen. Type III collagen, and type I gelatin, a heat-denatured type I collagen, also showed a similar interaction with TGF-β1, however, type IV collagen showed a weak interaction. In the presence of types I and III collagens, the inhibitory effect of TGF-β1 on the proliferation of mink lung epithelial cells was sustained, thus suggesting that the bioactivity of TGF-β1 had been enhanced. Type I gelatin also enhanced the inhibition of cell growth, but its effect was weak in comparison with that of type I collagen. The amount of TGF-β1 which remained intact in the conditioned medium after incubation with MLEC in the presence of types I and III collagens was more than that incubated without collagen.ConclusionsOur results suggest that types I and III collagens, the two most abundant components of the interstitial collagens, can potentially bind to activated TGF-β1 and regulate the bioactivity of this growth factor, thereby possibly maintaining the biologically available TGF-β1 level.