Abstract
Purpose: :
To investigate the differentiation profile of the epithelium of the eyelid margin in the non–human primate.
Methods: :
Eyelid tissues obtained from adult m. fasicularis sacrificed for other purposes were frozen and stored at –80°C. Expression of cytokeratins K4, K14, K5/8, K19, involucrin, connexin 43, muscarinic receptor subtypes (m1–m5) were determined to characterize the cells along either aspect of the lid margin, the eyelid stroma, and the tarsal conjunctiva.
Results: :
Cytokeratin 4 was positive in the superficial layers of the palpebral conjunctiva, the mucocutaneous junction (MCJ), and was seen throughout the conjunctiva epithelium at the fornix. Basal layers of conjunctival epithelium at the MCJ failed to express K4. K19 was not expressed at the MCJ; however, positive staining was seen in palpebral conjunctiva about 2 mm posterior to the MCJ and throughout the full thickness of the epithelium toward the fornix. Skin epithelium anterior to the MCJ was not positive for K19. From the MCJ to the fornical conjunctiva, K14 expression decreased from the basal 2–3 layers to the bottom layer becoming sparse. Ductal epithelial cells of the Meibomian gland and basal skin epidermis were also positive for K14. K5/8 was positive in all layers of palpebral conjunctiva beginning just posterior to the MCJ, while in skin, staining was primarily in the basal epithelial layer. Involucrin was positive in the superficial epithelial layers at the MCJ as well as in the superficial layers of the conjunctiva and skin epithelium. Connexin 43, a marker for epithelial cell membrane junctions was expressed in the suprabasal epithelial cells of the skin near MCJ. Basal cells at the MCJ did not express Cx43. Palpebral conjunctiva had little expression of connexin 43. The m2 was expressed throughout the layers of the conjunctiva, but skin epidermis was not seen to support this receptor protein. The m3 staining was more specific for the basal layer of the palpebral conjunctival and alveolar epithelial cells of Meibomian glands. The m4 subtype showed strong staining in suprabasal layers of skin epithelium; however, only occasionally on goblet cells of palpebral conjunctival. m1 and m5 staining was not found in either skin epidermis or the conjunctiva.
Conclusions: :
The eyelid margin supports two types of epithelial cells that have specific distributions and different phenotypes. The distributions of positive cells suggest that the lid margin may be a source of progenitor cells.