Sequential Expression of Transforming Growth Factors α and β1 by Eosinophils During Cutaneous Wound Healing in the Hamster

Transforming growth factor-α (TGF-α) and TGF-β₁ have been proposed as important regulators of processes critical to successful wound healing. Although various cells present in wounds represent potential sources of either TGF-α and/or TGF-β, including macrophages, neutrophils, keratinocytes, fibroblasts, and endothelial cells, we recently identified eosinophils as an additional potential source of these cytokines. We therefore used in situ hybridization and immunohistochemistry to determine whether eosinophils represent significant sources of TGF-α and/or TGF-β₁ in skin wounds in the hamster. We found that these wounds developed a prominent infiltration of eosinophils, and that eosinophils were a cellular source of both TGF-α and TGF-β₁, mRNAs. TGF-α and TGF-β₁ proteins were detectable both within eosinophils and extracellularly. Moreover, there was a sequential pattern of TGF-α and TGF-β₁ expression by infiltrating eosinophils, with the onset of eosinophil-associated TGF-α expression preceding that of TGF-β₁. This sequential pattern of TGF expression suggests that eosinophils may help to regulate critical biological processes during wound healing.