Cell-to-Cell Communication and Expression of Gap Junctional Proteins in Human Diabetic and Nondiabetic Skin Fibroblasts: Effects of Basic Fibroblast Growth Factor

Abstract

Wound healing involves the interactions of many cell types, and is controlled in part by growth factors. Intercellular communication mediated by gap junctions is considered to play an important role in the coordination of cellular metabolism duringthe growth and development of tissues and organs. Basic fibroblast growth factor (bFGF), known to be important in wound healing, has been found to increase Cx43 expression and intercellular communication in endothelial cells and cardiac fibroblasts. It has been proposed that an increased coupling is necessary for the coordination of these cells in wound healing and angiogenesis, and that one of the actions of bFGF is to modulate intercellular communication. The aim of our study was to evaluate the effects of bFGF on gap junctional intercellular communication (GJIC) in vitro, and the presence of gap junctional proteins connexin (Cx) 26, Cx32, and Cx43 in fibroblasts of diabetic and nondiabetic individuals. Fibroblast cell lines (n = 10) were cultured for 3 d in serum-free media with or without bFGF (3 ng/mL). Cells were evaluated for the rate of GJIC by using laser cytometry, and for the presence of Cx26, Cx32, and Cx43 by immunohistochemical and Western analyses. All cell types communicated via contact-dependent mechanisms. The rate of GJIC was greater (p < 0.01) for diabetic than for nondiabetic fibroblasts (4.1 +/- 0.01 vs 3.3 +/- 0.01%/min). bFGF increased (p < 0.01) the rate of GJIC for diabetic (4.9 +/- 0.01 vs 4.1 +/- 0.01%) and nondiabetic (4.1 +/- 0.01 vs 3.3 +/- 0.01%) fibroblasts. Immunohistochemistry identified Cx26 in the cytoplasm, Cx32 was not detected, and Cx43 was present on the cellular borders in all cultures. Image analysis of immunofluorescent staining demonstrated that bFGF increased (p < 0.05) Cx43 expression in diabetic and nondiabetic fibroblasts. Western immunoblot analysis revealed bands at 43-46 kD that were similar in volume for diabetic and nondiabetic fibroblasts. Thus, gap junctions involving Cx43 and GJIC among fibroblasts appear to be targets for bFGF. Fibroblasts of diabetic individuals appear to have an increased rate of cell-cell coupling, correlating with a decreased rate of proliferation.

Abnormal Connexin Expression Underlies Delayed Wound Healing in Diabetic Skin

“…These observations suggest that dye spread occurred through gap junctions rather than by diffusion through the extracellular space. Also, consistent with these findings, elevated expression of Cx43 protein and increased communication have been reported in human diabetic fibroblasts (19), and mixed responses of different Cxs to diabetes have been noted in the renal system (20) and bladder (21). Effects of diabetes on dynamic responses of Cx expression to injury.…”

Glycated Albumin Modulates Endothelial Cell Thrombogenic and Inflammatory Responses

“…31 Others have shown an enhancement of gap junction expression under their particular conditions. 32,33 Our data would suggest that the expression of connexin-43 is highly regulated under these conditions and is a function of glycation extent and exposure duration. Most of the caveolin-1 literature is in agreement with our data in that there is an overall upregulation of caveolin-1 in response to glycated albumin.…”

Downstream Exposure to Growth Factors Causes Elevated Velocity and Dilation in Arteriolar Networks

“…While chronic exposure (days) alters gap junction expression and microvascular responses [54,55,56], exposures of only minutes will diminish cell-to-cell communication for VEGF [57] or FGF [58]. We show that within seconds, FGF2 initiates a remote vasodilation that can be blocked by 18αGA.…”