Objective The diagnosis of Sjögren's Syndrome (SS) in routine practice is largely a clinical one and requires a high index of suspicion by the treating physician. This great dependence upon clinical judgment frequently leads to delayed diagnosis or misdiagnosis. Tear protein profiles have been proposed as simple and reliable biomarkers for SS diagnosis. Given that cathepsin S activity is increased in the lacrimal glands and tears of NOD mice (a murine model of SS), we explored the clinical utility of using tear cathepsin S (CTSS) activity as a biomarker for SS. Methods A method to measure CTSS activity in tears eluted from Schirmer's strips was developed and validated. Schirmer's tests and CTSS activity measurements were performed on 278 female subjects, including patients with SS (n=73), rheumatoid arthritis (n=79), systemic lupus erythematosus (n=40), blepharitis (n=10), non-specific dry eye (n=31), or other autoimmune diseases (n=12), along with 33 healthy controls. Results Median tear CTSS activity in SS patients was 4.1-fold higher than in patients with non-SS autoimmune diseases, 2.1-fold higher than in patients with non-specific dry eye, and 41.1-fold higher than in healthy controls. Tear CTSS levels were equally elevated in primary and secondary SS independent of the Schirmer's strip values or of circulating anti-SSA or anti-SSB autoantibodies. Conclusion Markedly high levels of tear CTSS activity are suggestive of SS. CTSS activity in tears can be measured in a simple, quick, economical, and non-invasive fashion and may serve as a novel biomarker and indicator of autoimmune dacryoadenitis during the workup for SS.

Lysosomal acid lipase (LAL) is the critical enzyme for the hydrolysis of the triglycerides (TG) and cholesteryl esters (CE) delivered to lysosomes. Its deficiency produces two human phenotypes, Wolman disease (WD) and cholesteryl ester storage disease (CESD). A targeted disruption of the LAL locus produced a null (lal( -/-)) mouse model that mimics human WD/CESD. The potential for enzyme therapy was tested using mannose terminated human LAL expressed in Pichia pastoris (phLAL), purified, and administered by tail vein injections to lal( -/-) mice. Mannose receptor (MR)-dependent uptake and lysosomal targeting of phLAL were evidenced ex vivo using competitive assays with MR-positive J774E cells, a murine monocyte/macrophage line, immunofluorescence and western blots. Following (bolus) IV injection, phLAL was detected in Kupffer cells, lung macrophages and intestinal macrophages in lal( -/-) mice. Two-month-old lal( -/-) mice received phLAL (1.5 U/dose) or saline injections once every 3 days for 30 days (10 doses). The treated lal( -/-) mice showed nearly complete resolution of hepatic yellow coloration; hepatic weight decreased by approximately 36% compared to PBS-treated lal( -/-) mice. Histologic analyses of numerous tissues from phLAL-treated mice showed reductions in macrophage lipid storage. TG and cholesterol levels decreased by approximately 50% in liver, 69% in spleen and 50% in small intestine. These studies provide feasibility for LAL enzyme therapy in human WD and CESD.

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Investigating stimulation of endogenous wound healing in corneal endothelial cells (CECs) may help address the global shortage of donor corneas by decreasing the number of transplants performed for blindness due to endothelial dysfunction. We previously reported that IL-1β stimulation leads to fibroblast growth factor (FGF2) expression, enhancing migration and proliferation of mammalian CECs. However, FGF2 also promotes the endothelial-mesenchymal transition, which can lead to retrocorneal membrane formation and blindness. This prompted us to investigate downstream FGF2 signaling targets that could be manipulated to prevent retrocorneal membrane formation. FGF2 stimulation altered cell morphology and induced expression of mesenchymal transition marker genes such as snail family transcriptional repressor 1 (SNAI1), SNAI2, zinc finger E-boxbinding homeobox 1 (ZEB1), and ZEB2. This, in turn, induced expression of fibronectin, vimentin and, type I collagen and suppressed E-cadherin in CECs in vitro and ex vivo. siRNA-mediated SNAI1 knockdown revealed that SNAI1 induces ZEB1 expression, in turn inducing expression of type I collagen, the major component of retrocorneal membranes, and of cyclin-dependent kinase 2 (CDK2) and cyclin E1, promoting cell proliferation. siRNA-mediated knockdown of SNAI1 or ZEB1, but not of CDK2, inhibited FGF2-dependent expression of fibronectin, vimentin, and type I collagen and of suppression of E-cadherin expression. We conclude that SNAI1 is a key regulator of FGF2-dependent mesenchymal transition in human ex vivo corneal endothelium, with ZEB1 regulating type I collagen expression and CDK2 regulating cell proliferation. These results suggest that SNAI1 promotes fibrosis and cell proliferation in human corneal endothelium through ZEB1 and CDK2.The cornea is the anterior, transparent tissue of the human eye and consists of epithelium, stroma and endothelium. The corneal endothelium is composed of a monolayer of cells and plays a critical role in maintaining corneal transparency that is critical for sharp vision through its pump function (1,2). Adult human corneal endothelial cells (CEC) are usually mitotically inactive and arrested at the G 1 phase of the cell cycle (3,4). Because of the cell cycle arrest, there is a progressive decline in CEC density that can be further accelerated by injury, such as intraocular surgery or infection. When the density decreases below a critical threshold, corneal edema ensues, leading to loss of transparency and vision. Vision loss secondary to endothelial dysfunction is a common indication for corneal transplantation in developed nations.There have been many attempts to overcome the cell cycle arrest using various approaches including the use of growth factors such as FGF, EGF, and TGF-β, the use of endothelial cell growth supplements (5-9), and disruption of contact inhibition using EDTA (10). Moreover, severely injured CEC can undergo mesenchymal transition through which they lose their polarity and assume a fibroblastic phenotype. These CEC a...

The avascular corneal epithelium plays an important role in maintaining normal vision and protecting the corneal interior from environmental infections. Delayed recovery of ocular wounds caused by trauma or refractive surgery strengthens the need to accelerate corneal wound healing and better restore the ocular surface. To address this need, we fused elastin-like polypeptide (ELP) based nanoparticles SI with a model mitogenic protein called lacritin. Lacritin fused at the N-terminus of the SI diblock copolymer is called LSI. This LSI fusion protein undergoes thermo-responsive assembly of nanoparticles at physiologically relevant temperatures. In comparison to ELP nanoparticles without lacritin, LSI showed potent signs of lacritin specific effects on a human corneal epithelial cell line (HCE-T), which included enhancement of cellular uptake, calcium-mediated signaling, and closure of a scratch. In vivo, the corneas of non-obese diabetic mice (NOD) were found to be highly responsive to LSI. Fluorescein imaging and corneal histology suggested that topical administration of LSI onto the ocular surface significantly promoted corneal wound healing and epithelial integrity compared to mice treated with or without plain ELP. Most interestingly, it appears that ELP-mediated assembly of LSI is essential to produce this potent activity. This was confirmed by comparison to a control lacritin ELP fusion called LS96, which does not undergo thermally-mediated assembly at relevant temperatures. In summary, fusion of a mitogenic protein to ELP nanoparticles appears to be a promising new strategy to bioengineer more potent biopharmaceuticals with potential applications in corneal wound healing.

Cathepsin S (CTSS) activity is elevated in Sjögren’s Syndrome (SS) patient tears. Here we tested whether protease inhibition and cystatin C (Cys C) levels are reduced in SS tears, which could lead to enhanced CTSS-driven degradation of tear proteins. CTSS activity against Cys C, LF and sIgA was tested in SS or healthy control tears. Tears from 156 female subjects (33, SS; 33, rheumatoid arthritis; 31, other autoimmune diseases; 35, non-autoimmune dry eye (DE); 24, healthy controls) were analyzed for CTSS activity and Cys C, LF, and sIgA levels. Cys C and LF showed enhanced degradation in SS tears supplemented with recombinant CTSS, but not supplemented healthy control tears. CTSS activity was significantly increased, while Cys C, LF and sIgA levels were significantly decreased, in SS tears compared to other groups. While tear CTSS activity remained the strongest discriminator of SS in autoimmune populations, combining LF and CTSS improved discrimination of SS beyond CTSS in DE patients. Reductions in Cys C and other endogenous proteases may enhance CTSS activity in SS tears. Tear CTSS activity is reconfirmed as a putative biomarker of SS in an independent patient cohort while combined LF and CTSS measurements may distinguish SS from DE patients.

Dry eye is a common disorder caused by inadequate hydration of the ocular surface that results in disruption of barrier function. The homeostatic protein clusterin (CLU) is prominent at fluid-tissue interfaces throughout the body. CLU levels are reduced at the ocular surface in human inflammatory disorders that manifest as severe dry eye, as well as in a preclinical mouse model for desiccating stress that mimics dry eye. Using this mouse model, we show here that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. These findings define a fundamentally new mechanism for ocular surface protection and suggest CLU as a biotherapeutic for dry eye.