Major histocompatibility class II expression in the normal canine cornea and in canine chronic superficial keratitis

Molecular mechanisms regulating wound repair: Evidence for paracrine signaling from corneal epithelial cells to fibroblasts and immune cells following transient epithelial cell treatment with Mitomycin C

In this paper, we use RNAseq to identify senescence and phagocytosis as key factors to understanding how mitomyin C (MMC) stimulates regenerative wound repair. We use conditioned media (CM) from untreated (CMC) and MMC treated (CMM) human and mouse corneal epithelial cells to show that corneal epithelial cells indirectly exposed to MMC secrete elevated levels of immunomodulatory proteins including IL-1α and TGFβ1 compared to cells exposed to CMC. These factors increase epithelial and macrophage phagocytosis and promote ECM turnover. IL-1α supplementation can increase phagocytosis in control epithelial cells and attenuate TGFβ1 induced αSMA expression by corneal fibroblasts. Yet, we show that epithelial cell CM contains factors besides IL-1α that regulate phagocytosis and αSMA expression by fibroblasts. Exposure to CMM also impacts the activation of bone marrow derived dendritic cells and their ability to present antigen. These in vitro studies show how a brief exposure to MMC induces corneal epithelial cells to release proteins and other factors that function in a paracrine way to enhance debris removal and enlist resident epithelial and immune cells as well as stromal fibroblasts to support regenerative and not fibrotic wound healing.

Genome-Wide Association Analysis for Chronic Superficial Keratitis in the Australian Racing Greyhound

Chronic superficial keratitis (CSK) is a progressive inflammatory condition of the eye (cornea) that can cause discomfort and blindness. Differential disease risk across dog breeds strongly suggests that CSK has a genetic basis. In addition to genetic risk, the occurrence of CSK is exacerbated by exposure to ultraviolet light. Genome-wide association analysis considered 109 greyhounds, 70 with CSK and the remainder with normal phenotype at an age over four years. Three co-located variants on CFA18 near the 5' region of the Epidermal Growth Factor Receptor (EGFR) gene were associated with genome-wide significance after multiple-test correction (BICF2P579527, CFA18: 6,068,508, p_raw = 1.77 × 10^-7, p_genome = 0.017; BICF2P1310662, CFA18: 6,077,388, p_raw = 4.09 × 10^-7, p_genome = 0.040; BICF2P160719, CFA18: 6,087,347, p_raw = 4.09 × 10^-7, p_genome = 0.040) (canFam4)). Of the top 10 associated markers, eight were co-located with the significantly associated markers on CFA18. The associated haplotype on CFA18 is protective for the CSK condition. EGFR is known to play a role in corneal healing, where it initiates differentiation and proliferation of epithelial cells that in turn signal the involvement of stromal keratocytes to commence apoptosis. Further validation of the putative functional variants is required prior to their use in genetic testing for breeding programs.

Heat Shock Proteins 70kDa, Eosinophil Cationic Protein, and Nitric Oxide During Chronic Superficial Keratitis in Dogs

The objective of the study is to determine the levels of eosinophil cationic protein (ECP), heat shock proteins 70, and nitric oxide ions measured as nitrite ions (Griess reaction) in dogs with chronic superficial keratitis (CSK). The study was conducted on 24 dogs with CSK. Blood sera from the animals were tested for concentrations of heat shock proteins 70, ECP, and nitrite ions before treatment and again 5 weeks and 6 months after treatment. Dogs with CSK were treated for 6 months with various regimes involving the use of ophthalmic drops containing dexamethasone, dimethyl sulfoxide, and cyclosporine. The control group consisted of 16 clinically healthy German Shepherds. The results obtained indicated a significant (P ≤ 0.05) elevation in the concentrations of heat shock proteins 70 and nitrite ions in dogs with CSK in comparison to healthy dogs and dogs after 5 weeks of therapy. After 6 months of treatment, concentrations of heat shock proteins 70, ECP, and nitrite ions had fallen below pretreatment values. Significant correlations were found between concentrations of heat shock proteins 70, ECP, and nitrite ions in healthy animals and animals with CSK. The elevated concentrations of heat shock proteins 70, ECP, and nitrite ions in dogs with CSK may indicate that the disease was both localized and systemic. The significant correlation between levels of heat shock proteins 70 and nitrite ions suggests that these parameters may be used as indirect indicators of CSK.

A study of the association between chronic superficial keratitis and polymorphisms in the upstream regulatory regions of DLA-DRB1, DLA-DQB1 and DLA-DQA1

Canine chronic superficial keratitis (CSK) is an inflammatory corneal disease that primarily occurs in German shepherd dogs (GSDs). Several studies support the hypothesis that CSK is an immune-mediated disease. To investigate the genetic factors associated with CSK development, the upstream regulatory regions (URRs) of the DLA-DRB, -DQA and -DQB genes were genotyped in 60 dogs, including 32 CSK animals. LD analysis identified two blocks (r(2)≤45), with two DLA-DRB1 and five DLA-DQB1 haplotypes. Analysis of DLA-URR alleles/haplotypes showed a significant association between DQB1*-154 [C/T] (p=0.016) and CSK, suggesting that the T variant may increase the risk for developing CSK disease (OR=3, 95% CI=1.25-7.68). When haplotype associations were performed, the URR-DQB*CATT haplotype was significantly associated with CSK (p=0.016), increasing the risk of develop this disease over two-fold (OR=3, 95%, CI=1.25-7.68). These results showed that dogs homozygous at DRB1*69 [C/T] had a risk for developing CSK disease that was over four times the risk for heterozygotes. This genetic association supports the previous clinical, histological and pharmacological studies that suggest that CSK is an immune-mediated disease, and this association could potentially be used to identify susceptible animals.

Concise review: immunological properties of ocular surface and importance of limbal stem cells for transplantation

Cornea transplantation has been considered to be different from other solid organ transplantation because of the assumed immune-privileged state of the anterior chamber of the eye. Three major lines of thought regarding the molecular mechanisms of immune privilege in the eye are as follows: (a) anatomical, cellular, and molecular barriers in the eye; (b) anterior chamber-associated immune deviation; and (c) immunosuppressive microenvironment in the eye. However, cornea transplants suffer allograft rejection when breached by vascularization. In recent developments, cellular corneal transplantation from cultivated limbal epithelial cells has shown impressive advances as a future therapy. The limbal stem cell niche contains stem cells that promote proliferation and migration and have immunosuppressive mechanisms to protect them from immunological reactions. Limbal stem cells are also noted to display an enhanced expression of genes for the antiapoptotic proteins, a property that is imperative for the survival of transplanted tissues. Further investigation of the molecular mechanisms regulating the immune regulation of limbal stem cells is relevant in the clinical setting to promote the survival of whole corneal and limbal stem cell transplantation.

MHC class II risk haplotype associated with canine chronic superficial keratitis in German Shepherd dogs

Canine chronic superficial keratitis (CSK) is an inflammatory ocular disease of an autoimmune origin leading to blindness if untreated. The main symptoms of CSK are progressive, bilateral vascularisation, fibrous tissue formation and pigmentation of the anterior corneal stroma. Although CSK is found in many breeds it is most prevalent in German Shepherd dogs (GSDs). Since Major Histocompatibility Complex (MHC) class II is associated with several autoimmune diseases in dogs we investigated the possible role of DLA-DRB1, -DQA1 and -DQB1 in GSDs affected with CSK. Our study population included 25 healthy controls and 30 CSK dogs. Most of the affected dogs were females suggesting a female predisposition. We identified 11 unevenly distributed haplotypes of which DLA-DRB1*01501/DQA1*00601/DQB1*00301 was significantly associated with the CSK dogs (OR=2.67, CI=1.17-6.44, p=0.02). We also found that overall homozygosity of MHC class II increases risk for CSK (OR=4.37, CI=1.27-18.46, p=0.02) and homozygosity of the risk haplotype by over eight-fold (OR=8.5, 95% CI=1.4-224, p=0.017). This study identifies a MHC class II risk haplotype for CSK in GSD and further supports the autoimmune origin of the disease.

Immune-mediated canine and feline keratitis

Although the normal cornea is devoid of vasculature and lymphatics, there are still several immune-mediated corneal conditions that can occur in dogs and cats. An overview of corneal immunology is presented. Diseases of dogs, including chronic superficial keratitis, superficial punctate keratitis, and canine adenovirus endotheliitis, as well as feline diseases, including eosinophilic keratitis and herpesvirus-related conditions, are discussed.

Canine normal corneal epithelium bears a large population of CD45-positive cells

This investigation sought to identify the presence of immune cells in normal canine corneal epithelium. A whole-mount immunofluorescence study of normal canine epithelium using monoclonal antibodies against CD45, CD11c, CD1c and MHC class II was performed. CD45-positive cells were located in all epithelial layers throughout the cornea, occurring in greater numbers (51.98+/-4.1/mm(2)) at the periphery and decreasing towards the central region (11.8+/-3.1/mm(2)). CD11c-positive cells were also observed, but were fewer in number. The findings show that the normal canine cornea carries a significant number of cells of immune origin; these cells seem to be of an inactive phenotype as they do not express MHC class II. Further studies are needed to determine whether these cells can express co-stimulatory molecules and act as antigen presenting cells if stimulated.

Effect of the ocular microenvironment in regulating corneal dendritic cell maturation

OBJECTIVE

To determine whether the ocular anterior segment (aqueous humor and cornea) actively inhibits dendritic cell (DC) maturation.

METHODS

Dendritic cells were injected into syngeneic corneas or conjunctivae, and their surface major histocompatibility complex class II expression in response to the local milieu was assessed using confocal microscopy. Immature DCs were cocultured with corneal supernatant or with aqueous humor to evaluate their regulation of DC phenotypic and functional maturity.

RESULTS

In contrast to conjunctivally injected DCs, DCs injected into the cornea resisted up-regulation in expression of surface major histocompatibility complex class II. Corneal supernatant-treated and aqueous humor-treated DCs retained their immaturity, as reflected by high antigen uptake but low costimulatory molecule (CD80 and CD86) expression and poor T-cell stimulation. Anti-transforming growth factor beta(2) treatment of aqueous humor and of corneal supernatant led to complete and partial blockade of their inhibition of DC maturation, respectively. However, alpha-melanocyte-stimulating hormone and calcitonin gene-related peptide had no demonstrable effect on DC maturation.

CONCLUSION

Cornea and aqueous humor, principally through transforming growth factor beta(2,) promote generation of phenotypically and functionally immature DCs. Clinical Relevance Our results indicate that relative immune quiescence in the cornea and in the anterior segment is actively maintained in part by the inhibitory effect of transforming growth factor beta(2) on resident DCs and by their suppression of T-cell-mediated immune and inflammatory responses.