Fibronectin provides a conduit for fibroblast transmigration from collagenous stroma into fibrin clot provisional matrix

Abstract

After injury, the wound space is filled with a fibrin/fibronectin clot containing growth factors released by platelets and monocytes. In response to these factors, fibroblasts migrate into the fibrin clot and contribute to the formation of granulation tissue. The functional mechanisms allowing fibroblasts to leave the collagenous matrix of normal connective tissue and invade the provisional matrix of the fibrin clot have not been fully defined. To investigate these mechanisms we established a new in vitro model which simulates specific aspects of early wound healing, that is, the migration of fibroblasts from a three-dimensional collagen matrix into a fibrin clot. This transmigration could be induced by physiological concentrations of platelet releasate or platelet-derived growth factor BB (PDGF-BB) in a concentration-dependent manner. At 24 hours irradiated fibroblasts invaded the fibrin gel almost as well as non-irradiated cells, indicating that transmigration was independent of proliferation. Plasminogen and its activators appear to be necessary for invasion of the fibrin clot since protease inhibitors decreased the amount of migration. These serine proteases, however, were not necessary for exit from the collagen gel as fibroblasts migrated out of the collagen gel onto a surface coated with fibrin fibrils even in the presence of inhibitors. Removal of fibronectin (FN) from either the collagen gel or the fibrin gel markedly decreased the number of migrating cells, suggesting that FN provides a conduit for transmigration. Cell movement in the in vitro model was inhibited by RGD peptide, and by monoclonal antibodies against the subunits of the alpha5 beta1 and alpha v beta3 integrin receptor. Thus, the functional requirements for fibroblast transmigration from collagen-rich to fibrin-rich matrices, such as occurs in early wound healing, have been partially defined using an in vitro paradigm of this important biologic process.

The conditioned medium from mesenchymal stromal cells pretreated with proinflammatory cytokines promote fibroblasts migration and activation

“…It has been demonstrated that PDGF-BB serves as both a chemoattractant and in establishing a haptotactic gradient for HDF transmigration from peripheral tissues to the wound surface and promotes the vitality and function of HDFs [ 19 , 20 ]. We detected the content of PDGF-BB in IT MSC-CM by ELISA.…”

Angiogenic Properties of Concentrated Growth Factors (CGFs): The Role of Soluble Factors and Cellular Components

“…It is known that platelet concentrates could provide a supportive matrix for circulating stem/progenitor cells [68,69], which are recruited from blood to injured tissue by a variety of signaling molecules [5,70], including VEGF, MMP, PDGF-B, and Ang-2 [16,[71][72][73]. Growing evidence points to the role of circulating CD34 positive cells, such as EPCs, in vascular maintenance, neovascularization, and angiogenesis [3][4][5][6]74].…”

Hydrogel scaffolds asin vitromodels to study fibroblast activation in wound healing and disease

“…Fibronectin and PDGF play a role in fibroblast migration to fibrin clots in collagen hydrogels. 48 Further, plasminogen expression aids in fibroblast invasion of fibrin, but may not be essential. Evidence suggests that the expression of other proteinases can overcome plasminogen deficiency.…”