Cornea

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Bron AJ, de Paiva CS, Chauhan SK, Bonini S, Gabison EE, Jain S, Knop E, Markoulli M, Ogawa Y, Perez V, Uchino Y, Yokoi N, Zoukhri D, Sullivan DA. TFOS DEWS II pathophysiology report. Ocul Surf 2017;15(3):438-510.Abstract
The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.
Bron AJ, Argüeso P, Irkec M, Bright FV. Clinical staining of the ocular surface: mechanisms and interpretations. Prog Retin Eye Res 2015;44:36-61.Abstract

In this article we review the mechanism of ocular surface staining. Water-soluble dyes are excluded from the normal epithelium by tight junctions, the plasma membranes and the surface glycocalyx. Shed cells can take up dye. A proportion of normal corneas show sparse, scattered time-dependent, punctate fluorescein uptake, which, we hypothesise, is due to a graded loss of the glycocalyx barrier, permitting transcellular entry into pre-shed cells. In pathological staining, there is little evidence of 'micropooling' at sites of shedding and the term 'punctate erosion' may be a misnomer. It is more likely that the initial event involves transcellular dye entry and, in addition, diffusion across defective tight junctions. Different dye-staining characteristics probably reflect differences in molecular size and other physical properties of each dye, coupled with differences in visibility under the conditions of illumination used. This is most relevant to the rapid epithelial spread of fluorescein from sites of punctate staining, compared to the apparent confinement of dyes to staining cells with dyes such as lissamine green and rose bengal. We assume that fluorescein, with its lower molecular weight, spreads initially by a paracellular route and then by transcellular diffusion. Solution-Induced Corneal Staining (SICS), related to the use of certain contact lens care solutions, may have a different basis, involving the non-pathological uptake of cationic preservatives, such as biguanides, into epithelial membranes and secondary binding of the fluorescein anion. It is transient and may not imply corneal toxicity. Understanding the mechanism of staining is relevant to the standardisation of grading, to monitoring disease and to the conduct of clinical trials.

Brown L, Foulsham W, Pronin S, Tatham AJ. The Influence of Corneal Biomechanical Properties on Intraocular Pressure Measurements Using a Rebound Self-tonometer. J Glaucoma 2018;27(6):511-518.Abstract
PURPOSE: The purpose of this study was to examine the effect of corneal biomechanical properties on intraocular pressure (IOP) measurements obtained using a rebound self-tonometer (Icare HOME) compared with Goldmann applanation tonometry (GAT). METHODS: An observational study of 100 patients with glaucoma or ocular hypertension. All had a comprehensive ophthalmic examination and standard automated perimetry. IOP was assessed by GAT, Icare HOME and Ocular Response Analyzer, which was also used to assess corneal hysteresis (CH) and corneal resistance factor (CRF). Central corneal thickness (CCT) was recorded. RESULTS: Mean (±SD) IOP measurements were 14.3±3.9 and 11.7±4.7 mm Hg using GAT and Icare HOME, respectively. Average CCT, CRF, and CH were 534.5±37.3 μm, 9.0±1.7 mm Hg, and 9.4±1.5 mm Hg, respectively. The mean difference between Icare HOME and GAT was -2.66±3.13 mm Hg, with 95% limits of agreement of -8.80 to 3.48 mm Hg, however, there was evidence of proportional bias. There was negative correlation between IOP and CH [5.17 mm Hg higher Icare HOME IOP (P=0.041, R=0.029) and 7.23 mm Hg higher GAT IOP (P=0.008, R=0.080) for each 10 mm Hg lower CH], whereas thinner CCT was significantly associated with lower IOP (P<0.001, R=0.14 for Icare HOME and P<0.001, R=0.08 for GAT). In multivariable analysis, although CRF and CH remained associated with IOP measured using either GAT or Icare HOME, CCT was no longer significant. CONCLUSION: IOP measurements obtained using a self-tonometer, similar to GAT, were more influenced by overall corneal biomechanics than CCT.
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Cade F, Paschalis EI, Regatieri CV, Vavvas DG, Dana R, Dohlman CH. Alkali burn to the eye: protection using TNF-α inhibition. Cornea 2014;33(4):382-9.Abstract
PURPOSE: The aim of this study was to evaluate early retinal damage after induction of ocular surface alkali burns and the protective effects of tumor necrosis factor alpha (TNF-α) blockade. METHODS: Alkali injury was induced in mouse corneas by using 1 N NaOH. Retinal damage was assessed using a terminal deoxynucleotidyl transferase 2'-deoxyuridine 5-triphosphate nick end labeling (TUNEL) assay, 15 minutes to 14 days postburn. Immune cell infiltration was assessed by CD45 immunolocalization. Retinal cytokines were quantified using the enzyme-linked immunosorbent assay for interleukin (IL)1β, IL2, IL6, TNF-α, CCL5, and macrophage inflammatory protein-1α. Protection against retinal damage was attempted with a single dose of either anti-TNF-α antibody (infliximab, 6.25 mg/kg) or control immunoglobulin G (IgG), administered intraperitoneally 15 minutes after the burn was inflicted. Corneal injury was evaluated by using TUNEL and CD45 immunolocalization and by quantifying corneal neovascularization. RESULTS: There was significant damage to the retina within 24 hours of the corneal burn being inflicted. TUNEL+ labeling was present in 80% of the retinal ganglion cells, including a few CD45+ cells. There was a 10-fold increase in the retinal inflammatory cytokines in the study groups compared with that in controls. A single intraperitoneal dose of anti-TNF-α antibody, administered 15 minutes after the burn, markedly reduced retinal TUNEL+, CD45+ labeling, and inflammatory cytokine expression, compared with that in the controls. Additionally, TNF-α blockade caused a marked reduction in corneal neovascularization, and in cornea TUNEL and CD45 labeling, 5 days after the burn. CONCLUSIONS: This study shows that alkali corneal burns can induce significant retinal damage within 24 hours. A single dose of anti-TNF-α antibody, administered 15 minutes after inflicting the burn, provides significant retinal and corneal protection. This could lead to the discovery of novel therapies for patients with alkali injuries.
Carreno-Galeano JT, Dohlman TH, Yin J, Dana R. Limbal Stem Cell Deficiency Associated With Herpes Keratitis. Cornea 2021;40(8):967-971.Abstract
PURPOSE: To describe the demographic features and clinical characteristics of patients with herpes keratitis (HK) and limbal stem cell deficiency (LSCD) and identify possible factors associated with development of LSCD after HK. METHODS: In this retrospective case-series study, records of patients with a clinical diagnosis of HK seen at Massachusetts Eye and Ear over a 5-year period were reviewed for evidence of LSCD. Patient demographics, medical history, treatment, and best-corrected visual acuities (BCVAs) were recorded. RESULTS: We identified 626 patients with HK. Fifty-seven had been diagnosed with LSCD (9.3%). Thirteen percent of patients with herpes zoster keratitis (N= 25) and 7% of patients with herpes simplex keratitis (N= 32) had LSCD (P = 0.01). Keratitis caused by herpes zoster virus [odds ratios (OR), 1.77; 95% confidence interval (CI), 0.97-3.19; P = 0.01], stromal involvement (OR, 2.28; 95% CI, 1.27-4.18; P = 0.02), and the use of topical antihypertensives (OR, 2.28; 95% CI, 1.27-4.18; P = 0.02) were found to be associated with a higher likelihood of developing LSCD. The final logarithm of the minimum angle of resolution (LogMAR) BCVA was significantly lower in patients with LSCD compared with those without LSCD with a mean BCVA of 1.34 ± 1.52 LogMar (∼20/200) as compared to 0.18 ± 0.54 LogMar (∼20/30 ± 20/60) in those patients without LSCD (P = 0.005). CONCLUSIONS: Our data suggest that HK may be a risk factor for development of LSCD. Patients with HK should be monitored for the development of LSCD to reduce the risk of chronic ocular surface morbidity.
Carreno-Galeano JT, Dohlman TH, Kim S, Yin J, Dana R. A Review of Ocular Graft-versus-Host Disease: Pathophysiology, Clinical Presentation and Management. Ocul Immunol Inflamm 2021;:1-10.Abstract
Graft-versus-host disease is a common complication following allogeneic hematopoetic stem cell transplantation that can affect multiple organ systems, including the eyes. Ocular GVHD (oGVHD) is characterized by a T cell-mediated immune response that leads to immune cell infiltration and inflammation of ocular structures, including the lacrimal glands, eyelids, cornea and conjunctiva. oGVHD has a significant negative impact on visual function and quality of life and successful management requires a multi-disciplinary approach with frequent monitoring. Here, we review the pathophysiology and clinical presentation of oGVHD, along with current therapeutic strategies based on our clinical experience and the reported literature.
Català P, Thuret G, Skottman H, Mehta JS, Parekh M, Ní Dhubhghaill S, Collin RWJ, Nuijts RMMA, Ferrari S, LaPointe VLS, Dickman MM. Approaches for corneal endothelium regenerative medicine. Prog Retin Eye Res 2021;:100987.Abstract
The state of the art therapy for treating corneal endothelial disease is transplantation. Advances in the reproducibility and accessibility of surgical techniques are increasing the number of corneal transplants, thereby causing a global deficit of donor corneas and leaving 12.7 million patients with addressable visual impairment. Approaches to regenerate the corneal endothelium offer a solution to the current tissue scarcity and a treatment to those in need. Methods for generating corneal endothelial cells into numbers that could address the current tissue shortage and the possible strategies used to deliver them have now become a therapeutic reality with clinical trials taking place in Japan, Singapore and Mexico. Nevertheless, there is still a long way before such therapies are approved by regulatory bodies and become clinical practice. Moreover, acellular corneal endothelial graft equivalents and certain drugs could provide a treatment option for specific disease conditions without the need of donor tissue or cells. Finally, with the emergence of gene modulation therapies to treat corneal endothelial disease, it would be possible to treat presymptomatic patients or those presenting early symptoms, drastically reducing the need for donor tissue. It is necessary to understand the most recent developments in this rapidly evolving field to know which conditions could be treated with which approach. This article provides an overview of the current and developing regenerative medicine therapies to treat corneal endothelial disease and provides the necessary guidance and understanding towards the treatment of corneal endothelial disease.
Cavalcanti BM, Cruzat A, Sahin A, Pavan-Langston D, Samayoa E, Hamrah P. In vivo confocal microscopy detects bilateral changes of corneal immune cells and nerves in unilateral herpes zoster ophthalmicus. Ocul Surf 2018;16(1):101-111.Abstract
PURPOSE: To analyze bilateral corneal immune cell and nerve alterations in patients with unilateral herpes zoster ophthalmicus (HZO) by laser in vivo confocal microscopy (IVCM) and their correlation with corneal sensation and clinical findings. MATERIALS AND METHODS: This is a prospective, cross-sectional, controlled, single-center study. Twenty-four eyes of 24 HZO patients and their contralateral clinically unaffected eyes and normal controls (n = 24) were included. Laser IVCM (Heidelberg Retina Tomograph/Rostock Cornea Module), corneal esthesiometry (Cochet-Bonnet) were performed. Changes in corneal dendritiform cell (DC) density and morphology, number and length of subbasal nerve fibers and their correlation to corneal sensation, pain, lesion location, disease duration, and number of episodes were analyzed. RESULTS: HZO-affected and contralateral eyes showed a significant increase in DC influx of the central cornea as compared to controls (147.4 ± 33.9, 120.1 ± 21.2, and 23.0 ± 3.6 cells/mm2; p < 0.0001). In HZO eyes DCs were larger in area (319.4 ± 59.8 μm2; p < 0.001) and number of dendrites (3.5 ± 0.4 n/cell; p = 0.01) as compared to controls (52.2 ± 11.7, and 2.3 ± 0.5). DC density and size showed moderate negative correlation with total nerve length (R = -0.43 and R = -0.57, respectively; all p < 0.001). A higher frequency of nerve beading and activated DCs close to nerve fibers were detected specifically in pain patients. CONCLUSIONS: Chronic unilateral HZO causes significant bilateral increase in corneal DC density and decrease of the corneal subbasal nerves as compared to controls. Negative correlation was observed for DC density and size to nerve parameters, suggesting interplay between the immune and nervous systems. Patients with chronic pain also showed increased nerve beading and activated DCs.
Chang W-C, Abe R, Anderson P, Anderson W, Ardern-Jones MR, Beachkofsky TM, Bellón T, Biala AK, Bouchard C, Cavalleri GL, Chapman N, Chodosh J, Choi HK, Cibotti RR, Divito SJ, Dewar K, Dehaeck U, Etminan M, Forbes D, Fuchs E, Goldman JL, Holmes JH, Hope EA, Hung S-I, Hsieh C-L, Iovieno A, Jagdeo J, Kim MK, Koelle DM, Lacouture ME, Le Pallec S, Lehloenya RJ, Lim R, Lowe A, McCawley J, McCawley J, Micheletti RG, Mockenhaupt M, Niemeyer K, Norcross MA, Oboh D, Olteanu C, Pasieka HB, Peter J, Pirmohamed M, Rieder M, Saeed HN, Shear NH, Shieh C, Straus S, Sukasem C, Sung C, Trubiano JA, Tsou S-Y, Ueta M, Volpi S, Wan C, Wang H, Wang Z-Q, Weintraub J, Whale C, Wheatley LM, Whyte-Croasdaile S, Williams KB, Wright G, Yeung SN, Zhou L, Chung W-H, Phillips EJ, Carleton BC. SJS/TEN 2019: From science to translation. J Dermatol Sci 2020;Abstract
Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are potentially life-threatening, immune-mediated adverse reactions characterized by widespread erythema, epidermal necrosis, and detachment of skin and mucosa. Efforts to grow and develop functional international collaborations and a multidisciplinary interactive network focusing on SJS/TEN as an uncommon but high burden disease will be necessary to improve efforts in prevention, early diagnosis and improved acute and long-term management. SJS/TEN 2019: From Science to Translation was a 1.5-day scientific program held April 26-27, 2019, in Vancouver, Canada. The meeting successfully engaged clinicians, researchers, and patients and conducted many productive discussions on research and patient care needs.
Chao W, Belmonte C, Benitez Del Castillo J, Bron A, Dua H, Nichols K, Novack G, Schrader S, Willcox M, Wolffsohn J, Sullivan DA. Report of the Inaugural Meeting of the TFOS i2 = initiating innovation Series: Targeting the Unmet Need for Dry Eye Treatment (London, United Kingdom, March 21, 2015). Ocul Surf 2016;Abstract

In March 2015, a meeting was held in London, United Kingdom, to address the progress in targeting the unmet need for dry eye disease (DED) treatment. The meeting, which launched the i(2) = initiating innovation series, was sponsored by the Tear Film & Ocular Surface Society (TFOS; www.TearFilm.org) and supported by Dompé. The TFOS i(2) meeting was designed to review advances in the understanding of DED since publication of the 2007 TFOS International Dry Eye WorkShop (DEWS) report, and to help launch the highly anticipated sequel, DEWS II. The meeting was structured to discuss the scope of the DED problem, to review the clinical challenges of DED, and to consider the treatment challenges of DED. This article provides a synopsis of the presentations of this TFOS i(2) meeting.

Chauhan SK, Jurkunas U, Funaki T, Dastjerdi M, Dana R. Quantification of allospecific and nonspecific corneal endothelial cell damage after corneal transplantation. Eye (Lond) 2015;29(1):136-44.Abstract

PURPOSE: To investigate the effect of host immunity (allospecific) and surgical manipulation (non-allospecific) on corneal endothelial cells (CECs) in corneal transplantation. METHODS: Draining lymph nodes and grafted C57BL/6 corneas were harvested from syngeneic recipients, allograft acceptors, and allograft rejectors (BALB/c) 1, 3, and 8 weeks after transplantation. We analyzed CEC apoptosis using an ex vivo cornea-in-the-cup assay, and visualized cell-to-cell junctions using immunohistochemical staining (ZO-1). Automatic cell analysis using Confoscan software was used to measure CEC density as well as changes in CEC morphology by quantifying the coefficient of variation in cell size (polymegethism) and shape (pleomorphism). RESULTS: The cornea-in-the-cup assay showed that allogeneic acceptor T cells and to an even greater extent rejector T cells (but not syngeneic T cells) induced CEC apoptosis. CEC density after corneal transplantation was significantly reduced in allogeneic acceptors compared with syngeneic grafts (P<0.001), and CEC density was even further reduced in the allo-rejector group compared with the allo-acceptor group. Allogeneic grafts showed a greater increase in the coefficient of variation in cell size (polymegethism) when compared with syngeneic grafts 1 week after transplantation (P=P<0.001). However, pleomorphism was not significantly different between syngeneic and allo-acceptor grafts, indicating that polymegethism (but not pleomorphism or cell density) is a sensitive indicator of the effect of alloimmunity on CECs. CONCLUSIONS: Our data demonstrate that host alloimmunity rather than surgical manipulation alone is the major cause of CEC damage in corneal transplantation, and such morphologic changes of CECs can be detected before the clinically visible onset of allograft rejection.

Chauhan SK, Lee HK, Lee HS, Park EY, Jeong E, Dana R. PTK7+ Mononuclear Cells Express VEGFR2 and Contribute to Vascular Stabilization by Upregulating Angiopoietin-1. Arterioscler Thromb Vasc Biol 2015;35(7):1606-15.Abstract

OBJECTIVE: In angiogenesis, circulating mononuclear cells are recruited to vascular lesions; however, the underlying mechanisms are poorly understood. APPROACH AND RESULTS: Here, we characterize the functional role of protein tyrosine kinase 7 (PTK7)-expressing CD11b(+) mononuclear cells in vitro and in vivo using a mouse model of angiogenesis. Although the frequencies of PTK7(+)CD11b(+) cells in the bone marrow remained similar after vascular endothelial growth factor-A-induced neovascularization, we observed an 11-fold increase in the cornea. Importantly, vascular endothelial growth factor-A-induced chemotaxis of PTK7(+) cells was mediated by vascular endothelial growth factor receptor 2. In a coculture with endothelial cells, PTK7(+)CD11b(+) cells stabilized the vascular network for 2 weeks by expressing high levels of angiopoietin-1. The enhanced vascular stability was abolished by knockdown of angiopoietin-1 in PTK7(+)CD11b(+) cells and could be restored by angiopoietin-1 treatment. CONCLUSIONS: We conclude that PTK7 expression in perivascular mononuclear cells induces vascular endothelial growth factor receptor 2 and angiopoietin-1 expression and thus contributes to vascular stabilization in angiogenesis.

Chen Y, Chauhan SK, Tan X, Dana R. Interleukin-7 and -15 maintain pathogenic memory Th17 cells in autoimmunity. J Autoimmun 2017;77:96-103.Abstract

Th17 cells are principal mediators of many autoimmune conditions. Recently, memory Th17 cells have been revealed as crucial in mediating the chronicity of various refractory autoimmune disorders; however, the underlying mechanisms maintaining memory Th17 cells have remained elusive. Here, using a preclinical model of ocular autoimmune disease we show that both IL-7 and IL-15 are critical for maintaining pathogenic memory Th17 cells. Neutralization of these cytokines leads to substantial reduction of memory Th17 cells; both IL-7 and IL-15 provide survival signals via activating STAT5, and IL-15 provides additional proliferation signals via activating both STAT5 and Akt. Topical neutralization of ocular IL-7 or IL-15 effectively reduces memory Th17 cells at the inflammatory site and draining lymphoid tissues, while topical neutralization of IL-17 alone, the major pathogenic cytokine secreted by Th17 cells, does not diminish memory Th17 cells at the draining lymphoid tissues. Our results suggest that the effective removal of pathogenic memory Th17 cells via abolishing environmental IL-7 or IL-15 is likely to be a novel strategy in the treatment of autoimmune diseases.

Chen Y, Chauhan SK, Shao C, Omoto M, Inomata T, Dana R. IFN-γ-Expressing Th17 Cells Are Required for Development of Severe Ocular Surface Autoimmunity. J Immunol 2017;199(3):1163-1169.Abstract
Th17 cells are critical effectors mediating the ocular surface autoimmunity in dry eye disease (DED). Increased IFN-γ has also been implicated in DED; however, it remains unclear to what extent Th1 cells contribute to DED pathogenesis. In this study, we investigated the cellular source of IFN-γ and assessed its contribution to corneal epitheliopathy in DED mice. We discovered a significant IL-17A(+)IFN-γ(+) (Th17/1) population and determined that these cells are derived from Th17 precursors. Adoptive transfer of Th17/1, but not Th1, cells confers the disease to naive recipients as effectively as do Th17 cells alone. DED-induced IL-12 and IL-23 are required for in vivo transition of pathogenic Th17 cells to IFN-γ producers. Furthermore, using IFN-γ-deficient Th17 cells, we demonstrate the disease-amplifying role of Th17-derived IFN-γ in DED pathogenesis. These results clearly demonstrate that Th17 cells mediate ocular surface autoimmunity through both IL-17A and IFN-γ.
Chen D, Sahin A, Kam WR, Liu Y, Rahimi Darabad R, Sullivan DA. Influence of lipopolysaccharide on proinflammatory gene expression in human corneal, conjunctival and meibomian gland epithelial cells. Ocul Surf 2018;16(3):382-389.Abstract
PURPOSE: Lipopolysaccharide (LPS), a bacterial endotoxin, is known to stimulate leuokotriene B4 (LTB4) secretion by human corneal (HCECs), conjunctival (HConjECs) and meibomian gland (HMGECs) epithelial cells. We hypothesize that this LTB4 effect represents an overall induction of proinflammatory gene expression in these cells. Our objective was to test this hypothesis. METHODS: Immortalized HCECs, HConjECs and HMGECs were cultured in the presence or absence of LPS (15 μg/ml) and ligand binding protein (LBP; 150 ng/ml). Cells were then processed for RNA isolation and the analysis of gene expression by using Illumina BeadChips, background subtraction, cubic spline normalization and GeneSifter software. RESULTS: Our findings show that LPS induces a striking increase in proinflammatory gene expression in HCECs and HConjECs. These cellular reactions are associated with a significant up-regulation of genes associated with inflammatory and immune responses (e.g. IL-1β, IL-8, and tumor necrosis factor), including those related to chemokine and Toll-like receptor signaling pathways, cytokine-cytokine receptor interactions, and chemotaxis. In contrast, with the exception of Toll-like signaling and associated innate immunity pathways, almost no proinflammatory ontologies were upregulated by LPS in HMGECs. CONCLUSIONS: Our results support our hypothesis that LPS stimulates proinflammatory gene expression in HCECs and HConjECs. However, our findings also show that LPS does not elicit such proinflammatory responses in HMGECs.
Chen D, Wang J, Sullivan DA, Kam WR, Liu Y. Effects of Terpinen-4-ol on Meibomian Gland Epithelial Cells In Vitro. Cornea 2020;39(12):1541-1546.Abstract
PURPOSE: Infestation with demodex mites has been linked to the development of chalazion, meibomian gland dysfunction, and blepharitis. An effective treatment is the eyelid application of terpinen-4-ol (T4O), a tea tree oil component. However, T4O is also known to be toxic to nonocular epithelial cells. We hypothesize that T4O toxicity also extends to human meibomian gland epithelial cells (HMGECs). METHODS: Immortalized (I) HMGECs were cultured with varying concentrations (1.0%-0.001%) of T4O under proliferating or differentiating conditions up to 5 days. Experimental procedures included analyses of cell appearance, survival, P-Akt signaling, lysosome accumulation, and neutral lipid content. RESULTS: Our findings show that T4O causes a dose- and time-dependent decrease in the cell survival of IHMGECs. After 15 minutes of exposure to 1% T4O, IHMGECs exhibited rounding, atrophy, and poor adherence. Within 90 minutes of such treatment, almost all cells died. Reducing the T4O concentration to 0.1% also led to a marked decrease in P-Akt signaling and cell survival of IHMGECs. Decreasing the T4O amount to 0.01% caused a slight, but significant, reduction in the IHMGEC number after 5 days of culture and did not influence the ability of these cells to differentiate. CONCLUSIONS: T4O, even at levels 10-fold to 100-fold lower than demodicidal concentrations, is toxic to HMGECs in vitro.
Chen X, Sullivan BD, Rahimi Darabad R, Liu S, Kam WR, Sullivan DA. Are BALB/c Mice Relevant Models for Understanding Sex-Related Differences in Gene Expression in the Human Meibomian Gland?. Cornea 2019;38(12):1554-1562.Abstract
BACKGROUND: A compelling feature of dry eye disease is that it occurs predominantly in women. We hypothesize that this female prevalence is linked to sex-related differences in the meibomian gland (MG). This gland plays a critical role in maintaining the tear film, and its dysfunction is a major cause of dry eye disease. To understand the factors that underlie MG sexual dimorphism and promote dry eye in women, we seek to identify an optimal model for the human MG. Our goal was to determine whether a murine MG is such a model. Toward that end, we examined whether sex differences in MG gene expression are the same in BALB/c mice and humans. METHODS: Eyelid tissues were collected from humans (n = 5-7/sex) and BALB/c mice (n = 9/sex). MGs were isolated and processed for the evaluation of gene expression by using microarrays and bioinformatics software. RESULTS: Our analysis of the 500 most highly expressed genes from human and mouse MGs showed that only 24.4% were the same. Our comparison of 100 genes with the greatest sex-associated differences in human and mouse MGs demonstrated that none were the same. Sex also exerted a significant impact on numerous ontologies, Kyoto Encyclopedia of Genes and Genomes pathways, and chromosomes, but these effects were primarily species-specific. CONCLUSIONS: Our results indicate that BALB/c mice are not optimal models for understanding sex-related differences in gene expression of the human MG.
Chen D, Liu Y, Shu G, Chen C, Sullivan DA, Kam WR, Hann S, Fowler M, Warman ML. Ocular Manifestations of Chordin-like 1 Knockout Mice. Cornea 2020;39(9):1145-1150.Abstract
PURPOSE: In humans, loss-of-function mutations in the gene encoding Chordin-like 1 (CHRDL1) cause X-linked megalocornea (MGC1), characterized by bilateral corneal enlargement, decreased corneal thickness, and increased anterior chamber depth (ACD). We sought to determine whether Chrdl1 knockout (KO) mice would recapitulate the ocular findings found in patients with MGC1. METHODS: We generated mice with a Chrdl1 KO allele and confirmed that male Chrdl1 hemizygous KO mice do not express Chrdl1 mRNA. We examined the eyes of male mice that were hemizygous for either the wild-type (WT) or KO allele and measured corneal diameter, corneal area, corneal thickness, endothelial cell density, ACD, tear volume, and intraocular pressure. We also harvested retinas and counted retinal ganglion cell numbers. Eye segregation pattern in the dorsal lateral geniculate nucleus were also compared between male Chrdl1 KO and WT mice. RESULTS: Male Chrdl1 KO mice do not have larger cornea diameters than WT mice. KO mice have significantly thicker central corneas (116.5 ± 3.9 vs. 100.9 ± 4.2 μm, P = 0.013) and smaller ACD (325.7 ± 5.7 vs. 405.6 ± 6.3 μm, P < 0.001) than WT mice, which is the converse of what occurs in patients who lack CHRDL1. Retinal-thalamic projections and other ocular measurements did not significantly differ between KO and WT mice. CONCLUSIONS: Male Chrdl1 KO mice do not have the same anterior chamber abnormalities seen in humans with CHRDL1 mutations. Therefore, Chrdl1 KO mice do not recapitulate the human MGC1 phenotype. Nevertheless, Chrdl1 plays a role during mouse ocular development because corneas in KO mice differ from those in WT mice.
Chen X, Sullivan DA, Sullivan AG, Kam WR, Liu Y. Toxicity of cosmetic preservatives on human ocular surface and adnexal cells. Exp Eye Res 2018;Abstract
Cosmetic products, such as mascara, eye shadow, eyeliner and eye makeup remover are used extensively to highlight the eyes or clean the eyelids, and typically contain preservatives to prevent microbial growth. These preservatives include benzalkonium chloride (BAK) and formaldehyde (FA)-releasing preservatives. We hypothesize that these preservatives, at concentrations (BAK = 1 mg/ml; FA = 0.74 mg/ml) approved for consumer use, are toxic to human ocular surface and adnexal cells. Accordingly, we tested the influence of BAK and FA on the morphology, survival, and proliferation and signaling ability of immortalized human meibomian gland (iHMGECs), corneal (iHCECs) and conjunctival (iHConjECs) epithelial cells. iHMGECs, iHCECs and iHConjECs were cultured with different concentrations of BAK (5 μg/ml to 0.005 μg/ml) or FA (1 mg/ml to 1 μg/ml) under basal, proliferating or differentiating conditions up to 7 days. We used low BAK levels, because we found that 0.5 mg/ml and 50 μg/ml BAK killed iHMGECs within 1 day after a 15 min exposure. Experimental procedures included analyses of cell appearance, cell number, and neutral lipid content (LipidTox), lysosome accumulation (LysoTracker) and AKT signaling in all 3 cell types. Our results demonstrate that BAK and FA cause dose-dependent changes in the morphology, survival, proliferation and AKT signaling of iHMGECs, iHCECs and iHConjECs. Many of the concentrations tested induced cell atrophy, poor adherence, decreased proliferation and death, after 5 days of exposure. Cellular signaling, as indicated by AKT phosphorylation after 15 (FA) or 30 (BAK) minutes of treatment, was also reduced in a dose-dependent fashion in all 3 cell types, irrespective of whether cells had been cultured under proliferating or differentiating conditions. Our results support our hypothesis and demonstrate that the cosmetic preservatives, BAK and FA, exert many toxic effects on cells of the ocular surface and adnexa.
Chen Y, Shao C, Fan N-W, Nakao T, Amouzegar A, Chauhan SK, Dana R. The functions of IL-23 and IL-2 on driving autoimmune effector T-helper 17 cells into the memory pool in dry eye disease. Mucosal Immunol 2021;14(1):177-186.Abstract
Long-lived memory T-helper 17 (Th17) cells actively mediate the chronic inflammation in autoimmune disorders, including dry eye disease (DED). The mechanisms responsible for the maintenance and reactivation of these cells in autoimmunity have been subject of investigation. However, the process through which memory Th17 are generated from their effector precursors remains to be elucidated. Herein, using our murine model of DED, we detect a linear transition from effector-to-memory Th17 cells during the abatement phase of acute inflammation, which is accompanied by persistently high levels of IL-23 and diminished levels of IL-2. In addition, in vitro culture of effector Th17 cells derived from the DED animals with IL-23, but not IL-2, leads to significant generation of memory Th17 cells, along with upregulated expression levels of IL-7R and IL-15R by these cells. Furthermore, supplementation of IL-2 abolishes and blockade of IL-2 enhances IL-23-induced generation of memory Th17 cells in vitro. Finally, in vivo blockade of IL-23 signaling during the contraction phase of primary response inhibits the generation of memory Th17 cells from their effector precursors. Together, our data demonstrate a new dichotomy between IL-23 and IL-2 in driving effector Th17 cells into the memory pool in autoimmune-mediated ocular surface inflammation.

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