Pathologic keratinization

Abstract: Severe ocular surface diseases, such as Stevens-Johnson syndrome (SJS), ocular cicatricial pemphigoid (OCP), and Sjogren’s syndrome (SS) present some of the most challenging clinical cases facing eye care providers today.1,2 These patients experience numerous problems, including symblepharon formation, corneal vascularization, and squamous metaplasia. Squamous metaplasia is a serious clinical problem in that it causes pathologic keratinization of the ocular surface in response to disease processes that are autoimmune mediated (e.g., SS, SJS, OCP, rheumatoid arthritis, lupus, and scleroderma), infectious (e.g., trachoma), allergic (e.g., atopic dermatitis), and injury related (e.g., alkali burns). Very little is known about the molecular mechanisms mediating squamous metaplasia and efforts to inhibit it locally are markedly unsuccessful. Of interest, the presence of squamous metaplasia has been extensively correlated with proinflammatory activity of the ocular surface,3–6 yet the possibility that proinflammatory cytokines released from infiltrating cells actually contribute to squamous metaplasia has just recently begun to be examined.7 Squamous metaplasia, by definition, is a phenotypic change whereby epithelial cells initiate synthesis of specialized, squamous cell-specific proteins, including small proline-rich proteins (SPRRs), loricrin, involucrin, envoplakin, elafin, filaggrin, keratins, and the enzyme transglutaminase-1. These proteins form the cornified envelope (keratinization) typical of squamous cells.8–12 An outcome of the synthesis of these proteins is a change in the appearance of the cells, which convert from a nonkeratinized, stratified epithelium to a nonsecretory, keratinized epithelium.13 In the human eye, this process is accompanied by the loss of conjunctival goblet cells, an increase in epithelial stratification, and an enlargement of the superficial epithelial cells.6,14–17 Clinically, these patients experience destabilization of the cornea–tear interface, which can ultimately lead to decreased vision from loss of corneal transparency. Since squamous metaplasia is a histologic phenomenon, to understand it at a molecular level and to identify potential targets for therapeutic intervention requires the availability of a surrogate biomarker to be used in analytical studies. SPRR proteins are such a biomarker, having been shown to be expressed early in the squamous differentiation process.18 SPRR1B belongs to an SPRR multigene family consisting of two SPRR1 genes (1A and 1B), approximately seven SPRR2 genes, one SPRR3 gene, and one SPRR4 gene.19–22 SPRRs are cross-linked either to themselves and/or to other cornified envelope precursor proteins and thereby participate in barrier formation.11 Although SPRR expression is a normal feature of external squamous tissues (i.e., skin, scalp, footpad, and vaginal epithelia), it is a sign of disease when present in mucosal tissues such as the bladder, lung, or ocular surface.18,23 Recent studies have shown that SPRR1B mRNA is expressed at very low levels in cultured human corneal cells and this expression decreases with confluence and differentiation of the cultures.24 We hypothesized that SPRR1B is increased in response to biological processes that favor pathologic keratinization and thereby serves as an important endpoint for determining which molecular events favor the development of squamous metaplasia in human eyes. In this study, we examined SPRR1B in two different mouse models of dry eye disease. We defined a specific role for autoreactive T cells as inducers of squamous metaplasia and identified the cytokines IL1β and IFNγ as potential participants in this process. SPRR1B, IL1β, and IFNγ gene expression are increased in ocular surface tissues of mice and patients with autoimmune-mediated dry eye disease, and a direct link between the presence of these cytokines and induction of SPRR1B has been verified in vitro. This work provides an important connection between inflammation and autoimmune-mediated keratinizing ocular surface disease while introducing model systems that will help to define therapeutic approaches to prevent pathologic keratinization and vision loss.

Abstract: Detailed acute and chronic toxicity studies^' 2 of Vitamin A acid suggest that repeated daily doses of 20 to 30 mg may be tolerated. The toxic dosages obtained in animals^ were also confirmed in our investigations with humans, where daily oral doses of 50 to 100 and 200 mg Vitamin A acid caused side effects. Common side effects include headache, anorexia, dryness of lips and skin, and fatigue. Other less common findings include nausea, polydipsia, changes in pruritus, dizziness, hyperventilation and petechia. Side effects encountered with oral Vitamin A acid at doses of 100 mg corresponded to those observed at high doses of Vitamin A palmitate. One mg of Vitamin A acid is equivalent to 2,500 IU Vitamin A palmitate or 3,300 IU of Vitamin A alcohol; 100 mg Vitamin A acid corresponds to 3,000,000 IU of Vitamin A.

Abstract: PURPOSE Sjogren's syndrome (SS) is a common autoimmune disease that can cause aqueous-deficient dry eye and the aberrant differentiation of ocular mucosal epithelial cells toward a lineage that is pathologically keratinized and skin-like. PAX6 is the master regulator of corneal lineage commitment. Recently, we showed a functional role for PAX6 in preventing ocular surface damage induced by the proinflammatory cytokine, IL-1β, in a mouse model of SS. Here, we examine PAX6's potential as a clinical biomarker that predicts ocular surface disease in SS patients. METHODS Impression cytology specimens isolated from the bulbar conjunctiva of control (n = 43) and SS patients (n = 43) were used to evaluate the relative abundance of PAX6, IL-1β, and pathologic keratinization marker, small proline-rich protein (SPRR1B) by TaqMan qPCR. Transcript expression was examined relative to clinical data, including the ocular staining score (OSS), tear breakup time (TBUT), Schirmer tear test, serum autoantibody results, and the labial salivary gland focus score. RESULTS PAX6 expression was significantly reduced in SS patients (P = 0.010, Wilcoxon rank sum test), and highly correlated with OSS (Spearman ρ = 0.239, 95% CI 0.02-0.43; P = 0.027). The extent to which PAX6 predicted SPRR1B was largely dependent on IL-1β expression (R(2) = 0.28, P < 0.01) and elevated IL-1β predicted reduced TBUT (R(2) = 0.24, P = 0.035), low tear secretion (R(2) = 0.30, P = 0.011), and focus score (R(2) = 0.21, P = 0.002). CONCLUSIONS Downregulation of PAX6 in SS patients was highly associated with ocular surface damage and largely dependent on the level of inflammation. Restoration of PAX6 may provide a clinical approach to manage dry eye in SS patients.