Objective: To investigate the differentiation profile of the epithelium of the eyelid margin in the primate. Methods: The expression of cytokeratins (CKs) CK1/ 10, CK4, CK14, CK5/8, and CK19; involucrin; connexin 43; filaggrin; and muscarinic receptor subtypes (m1-m5) on eyelid tissues from adult Macaca fascicularis (n = 3) was studied by immunohistochemistry. Results: Cytokeratin 1/10, CK4, CK19, filaggrin, and connexin 43 expression varied across the epithelium of the mucocutaneous junction (MCJ). At the MCJ, CK4-positive cells overlapped basal CK14-expressing cells. The meibomian gland duct and the MCJ revealed layers of CK14-positive cells. Cytokeratin 5/8 was expressed in the basal layer of the epidermis and conjunctiva, while involucrin-positive cells were superficial. The m2 was expressed throughout the conjunctiva; m3 was found in the basal cells of the skin, conjunctiva, and alveolar epithelial cells of the meibomian glands; and m4 was expressed in the suprabasal layers of the skin. Conclusions: The eyelid margin epithelium is formed from 2 different epithelial cell subpopulations with specific but overlapping distributions. The meibomian gland duct or MCJ may be a site of conjunctival progenitor cells. Clinical Relevance: This study provides a basis for understanding eyelid pathological conditions and eventually for developing methods for cellular reconstruction of the eyelid margin using expanded progenitor cells.
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