GAP JUNCTIONAL COMMUNICATIONS IN WOUND REPAIR

Pennsylvania State Univ Hershey Med Ctr, Hershey PA

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Abstract

An essential requirement for species survival is the repair of damaged or lost tissues. In mammals lost dermis is replaced with scar; where fibroblasts migrate, synthesize and deposit collagen, then organize a new connective tissue matrix. The transport of nutrients to fibroblasts engaged in the repair process is assumed to be by passive diffusion. We propose that transport is through intercellular channels, gap junctions which allow the direct passage of small molecules between cells. Gap junction channels have been neither identified nor studied in dermal wound repair. Our working hypothesis is gap junctional communications optimize the repair process. The gap junction channel is composed of the connexon, a complex of six connexin (CX) proteins incorporated into the plasma membrane. Neighboring cell connexons form channels which can be rapidly and reversibly opened (coupled) or closed (uncoupled). There is a family of CX proteins where CX43 is the major gap junctional protein of fibroblasts. We have preliminary data showing CX43 in fetal skin and adult granulation tissue. Our hypothesis, that CX43 and gap junctional communication play a role in repair, will be tested using in vitro, ex vivo and in vivo wound repair models. The effect of gap junctional communications upon cell migration, collagen synthesis and the contraction of fibroblast populated collagen lattices will be compared with fibroblasts derived from 1) normal human dermis, 2) hypertrophic scar, 3) CX43 antisense human fibroblast transfections, 4) wild type fetal mouse dermis, 5) CX43 transgenic knockout mouse dermis, 6) adult mouse dermis and 7) adult mouse granulation tissue. Experiments are designed to demonstrate gap junctions by the passage of microinjected dye between fibroblasts within granulation tissue of rabbit ear chamber implants and incisional wounds of organ cultured fetal mouse limbs. The character and quantity of granulation tissue in the presence of gap junction uncouplers will be measured. The proposal will demonstrate the clinical relevance of gap junctional communications in repair and that its down regulation leads to suboptimal repair and its upregulation leads to excess scarring.