Studies in Vitro on the Role of αv and β1 Integrins in the Adhesion of Human Dermal Fibroblasts to Provisional Matrix Proteins Fibronectin, Vitronectin, and Fibrinogen

Abstract

Fibroblasts that migrate into a wound during the early stages of repair use cell surface integrins to interact with extracellular molecules as they move away from the interstitial matrix of normal tissue and into the provisional matrix of the wound. Therefore, to understand a critical phase of wound healing, it is necessary to understand the details of integrin involvement. Normal adult human dermal fibroblasts in culture express many receptors for the provisional matrix proteins fibronectin, vitronectin, and fibrinogen, including the integrins alpha 3 beta 1, alpha 4 beta 1, alpha 5 beta 1, alpha v beta 1, alpha v beta 3, and alpha v beta 5. We used quantitative flow cytometry to estimate the relative numbers of these receptors and immunoprecipitation to confirm the expression of alpha v beta 1. Adult human dermal fibroblasts primarily use beta 1 integrins, alpha 4 beta 1, alpha 5 beta 1, and possibly alpha v beta 1, for attachment to fibronectin. alpha v beta 3 and perhaps other integrins containing the alpha v subunit serve fibroblasts as secondary or auxiliary receptors for fibronectin. In contrast, these cells use alpha v integrins but probably not beta 1 integrins for attachment to vitronectin. alpha v beta 3 and alpha v beta 5 apparently act in concert to mediate attachment to vitronectin, and these two integrins may perform different functions during wound repair. Fibroblast adhesion to certain preparations of fibrinogen occurs, at least partially, through the small amount of fibronectin present in the preparations. Fibroblast attachment to fibrinogen purified free of fibronectin also occurs, and that was demonstrated with a sensitive new assay called electrical cell-substrate impedance sensing. Fibroblast attachment to pure fibrinogen can be inhibited by RGD peptide, suggesting that integrins are involved.

CAR-dependent and CAR-independent pathways of adenovirus vector–mediated gene transfer and expression in human fibroblasts

“…Gene therapy by Ad-mediated gene transfer requires that the target cells bind and take up the Ad vector efficiently (15,(20)(21)(22). In this study, we have demonstrated that CAR is rate limiting for infection by standard Ad5 vectors in primary α V integrin-positive cells and that the upregulation of CAR in such cells leads to increased binding of Ad, as well as more efficient expression of Ad transgene, both of which depend on a subgroup-specific fiber-CAR interaction.…”

Fibrin-Induced Skin Fibrosis in Mice Deficient in Tissue Plasminogen Activator

“…44 -46 It is possible that fibrin-mediated integrin ligation on the surface of fibroblasts causes a downstream intracellular signaling response via MAPK/ERK pathways that could potentially lead to an increase in collagen synthesis. 46,47 A similar process has been proposed to regulate the down-regulation of collagen synthesis by fibroblasts grown in collagen gels. 48 A persistence of fibrin due to reduced fibrinolysis may result in prolonged or enhanced cell-matrix interactions resulting in a further stimulation of procollagen gene expression.…”

Cooperation of C1q Receptors and Integrins in C1q-Mediated Endothelial Cell Adhesion and Spreading

“…The assay used in this study for measuring endothelial cell adhesion and spreading was modified from a previously described standard assay (21). Immulon 4 microtiter plates (Dynatech, Chantilly, VA) were coated with 50 l/well C1q (10 -50 g/ml) or other purified proteins diluted in 50 mM Tris (pH 7.4), 150 mM NaCl, and 0.1% NaN 3 .…”