SEQUENTIAL EXPRESSION OF TRANSFORMING GROWTH-FACTOR-ALPHA AND FACTOR-BETA(1) BY EOSINOPHILS DURING CUTANEOUS WOUND-HEALING IN THE HAMSTER

Transforming growth factor-alpha (TGF-alpha) and TGF-beta1, have been proposed as important regulators of processes critical to successful w ound heating. Although various cells present in wounds represent poten tial sources of either TGF-alpha and/or TGF-beta, including macrophage s, neutrophils, keratinocytes, fibroblasts, and endothelial cells, we recently identified eosinophils as an additional potential source of t hese cytokines. We therefore used in situ hybridization and immunohist ochemistry to determine whether eosinophils represent significant sour ces of TGF-alpha and/or TGF-beta1 in skin wounds in the hamster. We fo und that these wounds developed a prominent infiltration of eosinophil s, and that eosinophils were a cellular source of both TGF-alpha and T GF-beta1 mRNAs. TGF-alpha and TGF-beta1 proteins were detectable both within eosinophils and extracellularly. Moreover, there was a sequenti al pattern of TGF-alpha and TGF-beta1 expression by infiltrating eosin ophils, with the onset of eosinophil-associated TGF-alpha expression p receding that of TGF-beta1. This sequential pattern of TGF expression suggests that eosinophils may help to regulate critical biological pro cesses during wound healing.