Expression Pattern of Cyclooxygenase-2 in Normal Rat Epidermis and Pilosebaceous Unit During Hair Cycle

The study investigated the expression pattern of cyclooxygenase-2 (COX-2) in normal rat skin during the hair cycle using RT-PCR and immunochemistry. It was found that COX-2 mRNA levels increased significantly during the catagen and telogen phases of the hair cycle. COX-2 protein was primarily located in the epidermis and pilosebaceous unit, with strong expression in the suprabasal layers of the epidermis during anagen, which declined in catagen and telogen. In hair follicles, COX-2 was prominently expressed in the outer root sheath during anagen and was barely detectable in catagen and telogen. In sebaceous glands, COX-2 expression intensified during catagen and telogen, correlating with an increase in gland size. These findings suggested that COX-2 played a role in normal skin physiology, including epidermal differentiation, hair follicle morphogenesis, hair cycle stage transformation, and sebaceous gland lipid production.