Apelin, a new adipokine acting on hair follicle: an immunohistochemical study on ovine skin.

Apelin (AP) is a novel peptide belonging to the family of adipokines (1). Adipose tissue is a source of plasma AP and the secretion by this tissue is regulated by several factors including fasting and refeeding. Apelin specific receptor (APJ) shows a widespread tissue distribution and accordingly many physiological roles were described for AP. In this work, the expression of AP and APJ were investigated in the ovine skin by immunohistochemical technique in order to point out the presence of structures that might be locally responsive to the action of AP. The analyses performed evidenced a clear and intense immunostaining for APJ in the ovine skin, while AP expression cannot be observed. The receptor was localized in the hair follicles (HFs), while other structures of the skin appeared to be negative. APJ expression involved the outer root sheath and extended throughout follicular wall, from the infundibulum to the bulb. AP is a recently discovered molecule and, at present, there are not surveys describing it in the skin of any animal species including humans. The strong expression of APJ in the HF, suggests an important role of AP that probably acts on this organ through an endocrine mechanism. The identification of APJ in ovine skin is a preliminary study that introduces the study of AP in the skin and represents the beginning of a comparative survey that could contribute to the improvement of fiber quality. 1) Pitkin S.L., Maguire J.J., Bonner T.I., Davenpor A.P. (2010) Pharmacological Review 62:331–342.