Lymphocytic infiltration and goblet cell marker alteration in the conjunctiva of the MRL/MpJ-Faslprmouse model of Sjögren's syndrome

Sjögren's syndrome is an autoimmune disorder characterized by a progressive, immune-mediated destruction of mucosal tissues such as the lacrimal and salivary glands, leading to ocular and oral dryness. The MRL/MpJ-Faslpr mouse is one of the animal models used to study this disease. However, little is known about the potential alterations in the conjunctiva in this murine model. The purpose of this study was to determine: (1) whether the conjunctiva is infiltrated by T lymphocytes, (2) characterize the type, amount and temporal sequence of the inflammatory infiltrates, and (3) investigate whether the amount of conjunctival goblet cells is altered in this murine model of Sjögren's syndrome. Female 4-, 9-, 13-, 16-, and 18-/20-wk-old MRL/MpJ-Faslpr (lpr, diseased) and congenic MRL/MpJ (+/+, control) mice were used. Right eyes were either fixed, frozen, cryosectioned, and studied by immunofluorescence microscopy or the conjunctiva was removed, homogenized and analyzed by electrophoresis and Western blot analysis. The following antibodies were used: anti-CD3 (specific T lymphocyte marker), anti-cytokeratin 7 (CK-7), anti-PKD (formerly known as PKCμ, both markers of goblet cell bodies), anti-PGP 9.5 (pan-neuronal marker), anti-VIP and TH (markers for parasympathetic and sympathetic nerves, respectively), anti-adrenergic (α1 and β1–3) and muscarinic (M1–M3) receptor subtypes (markers for neurotransmitter receptors of the sympathetic and parasympathetic pathways, respectively). Left eyes were fixed, embedded, sectioned, and stained. Hematoxylin/eosin, Giemsa, or alcian blue/periodic acid Schiff's reagent were used to study lymphocyte infiltration; to determine the presence of eosinophils, neutrophils, and mast cells; and to count the number of goblet cells, respectively. By immunofluorescence microscopy, lymphocytes were detected in the conjunctiva of 9-wk-old lpr, but not +/+, mice. The lymphocytic infiltration became more extensive as the animals aged, with 16- and 18-/20-wk lpr mice appearing to have a greater lymphocytic infiltration than +/+ mice at the same age. By Western blot analysis, the amount of CD3 was enhanced in lpr compared to +/+ mice by the 16th wk, but not by the 9th wk. No major differences in the presence of eosinophils, neutrophils and degranulated mast cells between lpr and +/+ mice were observed. By light microscopy, a significant increase in goblet cell number was found in lpr mice compared to +/+ mice at 16 wks on. By Western blotting, the amount of CK-7 was significantly increased at 9 wks on and the amount of PKD was significantly increased at 16 wks. By immunofluorescence microscopy, there were no major differences in distribution of sympathetic and parasympathetic nerves present in the lpr conjunctiva compared to that of +/+ mice at any ages, although slight differences were observed with increased age. Muscarinic receptor expression was decreased, as less M3 receptor subtype-associated immunofluorescence was detected in older lpr mice compared to +/+ mice and confirmed by Western blot analysis. No differences in the localization or the amount of α1- or β1–3-adrenergic receptor immunodetection were observed between lpr and +/+ mice. We conclude that the conjunctiva is a target tissue in Sjögren's syndrome-related inflammation in this murine model.