Expression of Platelet-derived growth factor-A and its receptor in the skin of the dog

Introduction: Platelet-derived growth factor A (PDGF-A) is produced by keratinocytes and expressed by the epidermis in humans. It is implicated in hair follicle (HF) morphogenesis and is supposed to be a positive regulator of hair growth (Tomita et al., J Dermatol Sci 2006; 43 (2):105-153). PDGF-A also acts as a mitogen in cutaneous wound healing. In this study, PDGF-A and its receptor (PDGFR-A) were investigated in the skin of the dog by immunohistochemistry. Materials and Methods: A mouse monoclonal anti PDGFA antibody and a rabbit polyclonal anti PDGFR-A antibody (SCBT) were used. Skin specimens were collected from three dog fetuses, obtained from abortions, and five adult animals subjected to necropsy for pathologies not involving the integumentary system. Fetuses were at 25, 28 and 50 days of gestation respectively. The immunological reaction was visualized with the ABC kit (Vector Laboratories) and diaminobenzidine. Results: PDGF-A and PDGFR-A were both identified in the developing skin of the fetuses as well as in the adults. In the fetuses, immunostaining was localized in the epithelium llining the body surface and in the epithelial buds growing into the dermis. In the adults, PDGF-A was observed in some structures of the skin including the epidermis, HFs, blood vessels, arrector pili muscles and adipose tissue. In particular, positive cells were localized in the basal layer of the epidermis and the outer root sheath of the HFs. Likewise, PDGFR-A was observed in the epidermis and HFs; in both cases, staining was mainly localized in the suprabasal layers of epithelium. The receptor was also identified in the dermal sheath and in the dermal papilla of the HFs. Conclusion: PDGF-A and its receptor were identified in close apposition both in the epidermis and in HFs, suggesting a paracrine and/or autocrine action of this molecule during skin morphogenesis and during the hair cycle.