Abstract
The α-chemokines have been implicated as regulators of proliferation and differentiation of normal keratinocytes and as mediators of keratinocyte maturation and migration in inflammatory processes that involve the skin. Using the cutaneous wound repair model, we examined the sites and temporal sequence of the appearance of melanoma growth stimulatory activity or growth, regulated gene (MGSA/GRO; ligand) and the type B interleukin (IL)-8 receptor (IL-8RB) to which MGSA/GRO binds. Human burn tissues (n = 44) representing days 2 to 12 after injury were obtained during surgical debridement, fixed in 4% paraformaldehyde, and embedded in paraffin. Immunolocalizations were performed with polyclonal antisera for both ligand and receptor, as well as a monoclonal antibody for the IL-8 RB. Western blot analysis confirmed the presence of the IL-8 RB in immunoprecipitates of epidermal keratinocyte lysates. In normal skin, MGSA/GRO protein was restricted to sites populated by differentiated keratinocytes (suprabasal compartments, inner root sheath cells, and dermal sweat ducts). MGSA/GRO protein was barely detectable within epithelial margins and islands of burn wounds where the migrating/proliferating keratinocyte populations reside, but staining intensities increased as cells matured into the outer layers. Weak diffuse staining was detected in areas of neutrophilic infiltration (granulation tissue and overlying exudates). By contrast, in normal skin the IL-8 RB was detected in specific locations within epidermal and dermal compartments of healing wounds. In the dermis, polyvalent antibodies detected receptor immunoreactivity most prominently in dermal sweat ducts and endothelium of capillaries, whereas this immunoreactivity was inconspicuous in sections stained with the monoclonal antibody. Receptor immunostaining was noted in migrating/proliferating keratinocytes in epithelial margins and islands but was in the outer layers or in hypertrophic epidermis adjacent to wounds. This same pattern was observed in epidermal appendages such as hair follicles and eccrine sweat ducts. In granulation tissues, IL-8 RB was noted in numerous fibroblasts and in subpopulations of macrophages and smooth muscle. The presence of both MGSA/GRO and its receptor in human burn wounds implicate this cytokine as an autocrine or paracrine mediator of epidermal regeneration in both the inflammatory and proliferative phases of cutaneous wound repair.