Localization and Regulation of Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) in Human Meibomian Glands

Abstract

Purpose: : Increased levels of matrix metalloproteinases (MMPs) have been found in the tear fluid of patients with meibomian gland dysfunction. The purpose of this study was to determine the presence and regulation of EMMPRIN, a prominent upstream regulator of MMP activity, in human meibocytes in vitro and in vivo.

Methods: : The expression and distribution of EMMPRIN in meibomian glands was evaluated by laser capture microdissection and immunofluorescence microscopy in upper eyelids of human donors. Immortalized human meibomian gland epithelial (SLHMG) cells were grown at different stages of differentiation, representing nondifferentiated (no serum) and differentiated (serum) epithelial cultures. RNA and cell protein lysates were harvested and analyzed by RT-PCR and western blot, respectively.

Results: : By immunofluorescence, EMMPRIN localized to basal cells at the peripheral margin of secretory acini, with decreasing levels towards differentiating and mature meibocytes, and to the multilayered squamous epithelium of the ductule. The presence of EMMPRIN in acinar structures was confirmed by laser capture microdissection followed by RT-PCR. Confluent cultures of SLHMG grown under nondifferentiated conditions expressed EMMPRIN protein. Induction of differentiation with serum containing media resulted in a marked decrease of EMMPRIN biosynthesis.

Conclusions: : Our results indicate that EMMPRIN is present in basal-acinar and ductal epithelial cells of the human meibomian gland. The differentiation of human meibocytes correlates with decreased EMMPRIN biosynthesis.

Keywords: eyelid • anatomy • cornea: tears/tear film/dry eye