Collagen matrices attenuate the collagen-synthetic response of cultured fibroblasts to TGF-β

TLDR

Transforming growth factor‑β normally stimulates fibroblast collagen synthesis, but in collagen‑rich granulation tissue its effect is diminished despite persistent TGF‑β expression. The study aimed to determine whether a collagen matrix attenuates fibroblast collagen synthesis in response to TGF‑β. Human dermal fibroblasts were cultured in attached collagen gels or plastic, with and without TGF‑β, and collagen production was quantified, using fibrin gels as a control. Collagen matrices suppressed the TGF‑β–induced collagen response, yielding lower collagen production than plastic, an effect not due to TGF‑β binding and not seen in fibrin gels, suggesting matrix‑dependent attenuation of the TGF‑β–driven collagen synthesis.

Abstract

ABSTRACT Transforming growth factor-β, a potent modulator of cell function, induces fibroblasts cultured on plastic to increase collagen synthesis. In 5- and 7-day porcine skin wounds, which have minimal to moderate collagen matrix, respectively, transforming growth factor-β and type I procollagen were coordinately expressed throughout the granulation tissue. However, in 10-day collagen-rich granulation tissue type I procollagen expression diminished despite persistence of transforming growth factor-β. To investigate whether collagen matrix attenuates the collagen-synthetic response of fibroblasts to transforming growth factor-β, we cultured human dermal fibroblasts in conditions that simulate collagen-rich granulation tissue. Therefore, human dermal fibroblasts were suspended in attached collagen gels and collagen and noncollagen production was assayed in the absence and presence of transforming growth factor-β. Although transforming growth factor-β stimulated collagen synthesis by fibroblasts cultured in the collagen gels, these fibroblasts consistently produced less collagen than similarly treated fibroblasts cultured on plastic. This phenomenon was not secondary to nonspecific binding of transforming growth factor-β to the collagen matrix. Fibroblasts cultured in a fibrin gel responded to transforming growth factor-β similarly to fibroblasts cultured on plastic. Using immunofluorescence probes to type I procollagen, we observed that transforming growth factor-β increased type I procollagen expression in most fibroblasts cultured on plastic, but only in occasional fibroblasts cultured in collagen gels. From these data we conclude that collagen matrices attenuate the collagen synthetic response of fibroblast to transforming growth factor-β in vitro and possibly in vivo.