Cornea

PURPOSE: To investigate morphological changes of the corneal epithelium and subbasal nerves in patients with corneal allodynia using in vivo confocal microscopy (IVCM). DESIGN: Case-control study of patients with corneal allodynia and healthy controls. METHODS: Ten eyes of six patients were diagnosed with corneal allodynia at a single center and compared to fifteen healthy eyes. IVCM of the central cornea was performed on all subjects and controls. Images were retrospectively analyzed numbers of total corneal subbasal nerves, main trunks and branches, total nerve length and density, nerve branching, and tortuosity, superficial and basal epithelial cell densities, and superficial epithelial cell size. RESULTS: Corneal allodynia was seen in patients with dry eye disease, recurrent corneal erosion syndrome, exposure to ultraviolet radiation, and Accutane use. Compared to controls, patients with corneal allodynia had a significant decrease in the total numbers of subbasal nerves (P=.014), nerve branches (P=.006), total nerve length (P=.0029), total nerve density (P=.0029) and superficial and basal epithelial cell densities (P=.0004, P=.0036) with an increase in superficial epithelial cell size (P=.016). There were no statistically significant differences in the number of subbasal nerve main trunks (P=.09), nerve branching (P=.21), and nerve tortuosity (P=.05). CONCLUSIONS: Corneal IVCM enables near-histological visualization and quantification of the cellular and neural changes in corneal allodynia. Regardless of etiology, corneal allodynia is associated with decreased corneal epithelial cell densities, increased epithelial cell size, and decreased numbers and lengths of subbasal nerves despite an unremarkable slit-lamp examination. Therefore, IVCM may be useful in the management of patients with corneal allodynia.

PURPOSE: To analyze the density and morphology of corneal epithelial cells and keratocytes by in vivo confocal microscopy (IVCM) in patients with herpes zoster ophthalmicus (HZO) as associated with corneal innervation. DESIGN: Prospective, controlled and masked cross-sectional study. METHODS: setting: Single-center study. PATIENTS: Thirty eyes with the diagnosis HZO and their contralateral clinically unaffected eyes, 15 eyes of 15 normal controls. intervention procedures: In vivo confocal microscopy and corneal esthesiometry of the central cornea. MAIN OUTCOME MEASURES: Changes in morphology and density of the superficial and basal epithelial cells and stromal keratocytes, and correlation with corneal sensation. RESULTS: The density of superficial epithelial cells in HZO eyes with severe sensation loss (766.5 ± 25.2 cells/mm(2)) was significantly lower than both healthy control eyes (1450.23 ± 150.83 cells/mm(2)) and contralateral unaffected eyes (1974.13 ± 298.24 cells/mm(2)) (P = .003). Superficial epithelial cell size (1162.5 μm(2)) was significantly larger in HZO eyes with severe loss of sensation, as compared to contralateral (441.46 ± 298.14) or healthy eyes (407.4 ± 47.2μm(2); all P < .05). The density of basal epithelial cells, anterior keratocytes, and posterior keratocytes did not show statistical significance between patients, controls, and contralateral unaffected eyes. Changes in superficial epithelial cell density and morphology correlated strongly with corneal sensation. CONCLUSIONS: In vivo confocal microscopy reveals profound HZO-induced changes in the superficial epithelium, as demonstrated by increase in cell size, decrease in cell density, and squamous metaplasia. We demonstrate that these changes strongly correlate with changes in corneal innervation in eyes affected by HZO.

Specific factors from the corneal epithelium underlying the stimulation of stromal fibrosis and myofibroblast formation in corneal wound healing have not been fully elucidated. Given that exosomes are known to transfer bioactive molecules among cells and play crucial roles in wound healing, angiogenesis, and cancer, we hypothesized that corneal epithelial cell-derived exosomes may gain access to the underlying stromal fibroblasts upon disruption of the epithelial basement membrane and that they induce signaling events essential for corneal wound healing. In the present study, exosome-like vesicles were observed between corneal epithelial cells and the stroma during wound healing after corneal epithelial debridement. These vesicles were also found in the stroma following anterior stromal keratectomy, in which surgical removal of the epithelium, basement membrane, and anterior stroma was performed. Exosomes secreted by mouse corneal epithelial cells were found to fuse to keratocytes in vitro and to induce myofibroblast transformation. In addition, epithelial cell-derived exosomes induced endothelial cell proliferation and ex vivo aortic ring sprouting. Our results indicate that epithelial cell-derived exosomes mediate communication between corneal epithelial cells and corneal keratocytes as well as vascular endothelial cells. These findings demonstrate that epithelial-derived exosomes may be involved in corneal wound healing and neovascularization, and thus, may serve as targets for potential therapeutic interventions.

Dendritic cells (DCs) are antigen-presenting cells that normally play a critical role in stimulating T-cell-dependent immune responses. However, tolerogenic DCs (CD11cMHC-IICD80CD86) induce immune tolerance by stimulating regulatory T cells (Tregs: CD4CD25Foxp3). Although tolerogenic DCs are used to treat autoimmune diseases and to prevent transplantation rejection, the mechanisms by which they regulate alloimmunity are poorly understood. Here, we review our previous studies aiming to elucidate the mechanisms involved in immune rejection of corneal allografts using a corneal transplant model. We found that donor-derived tolerogenic DCs significantly prolonged corneal allograft survival by suppressing indirect allosensitization. We also reported the precise distribution of intraepithelial corneal DCs, termed Langerhans cells (LCs: CD11cLangerinMHC-II) in the cornea, which we maintain play a critical role in regulating corneal immunity. By confocal microscopy, we constructed 3-dimensional images of corneal LCs, which demonstrated that their cell bodies are present in the basal cell layer of the corneal epithelium. Furthermore, LC dendrites extend toward the ocular surface, but do not connect to epithelial tight junctions, indicating that they cannot directly interact with ocular surface antigens. We confirm the potential of DC therapy for corneal graft rejection and report the function of intraepithelial DCs (LCs) in the normal cornea.

Purpose: We fabricated and investigated polymeric scaffolds that can substitute for the conjunctival extracellular matrix to provide a substrate for autologous expansion of human conjunctival goblet cells in culture. Methods: We fabricated two hydrogels and two silk films: (1) recombinant human collagen (RHC) hydrogel, (2) recombinant human collagen 2-methacryloylxyethyl phosphorylcholine (RHC-MPC) hydrogel, (3) arginine-glycine-aspartic acid (RGD) modified silk, and (4) poly-D-lysine (PDL) coated silk, and four electrospun scaffolds: (1) collagen, (2) poly(acrylic acid) (PAA), (3) poly(caprolactone) (PCL), and (4) poly(vinyl alcohol) (PVA). Coverslips and polyethylene terephthalate (PET) were used for comparison. Human conjunctival explants were cultured on scaffolds for 9 to 15 days. Cell viability, outgrowth area, and the percentage of cells expressing markers for stratified squamous epithelial cells (cytokeratin 4) and goblet cells (cytokeratin 7) were determined. Results: Most of cells grown on all scaffolds were viable except for PCL in which only 3.6 ± 2.2% of the cells were viable. No cells attached to PVA scaffold. The outgrowth was greatest on PDL-silk and PET. Outgrowth was smallest on PCL. All cells were CK7-positive on RHC-MPC while 84.7 ± 6.9% of cells expressed CK7 on PDL-silk. For PCL, 87.10 ± 3.17% of cells were CK7-positive compared to PET where 67.10 ± 12.08% of cells were CK7-positive cells. Conclusions: Biopolymer substrates in the form of hydrogels and silk films provided for better adherence, proliferation, and differentiation than the electrospun scaffolds and could be used for conjunctival goblet cell expansion for eventual transplantation once undifferentiated and stratified squamous cells are included. Useful polymer scaffold design characteristics have emerged from this study.

PURPOSE: Purinergic receptors play a key role in the function of the lacrimal gland (LG) as P1 purinergic receptors A1, A2A, and A2B, P2X1-7 receptors, and many of the P2Y receptors are expressed. METHODS: This review examines the current knowledge of purinergic receptors in the LG as well as the signaling pathways activated by these receptors. RESULTS: These receptors are expressed on the acinar, ductal, and myoepithelial cells. Considerable crosstalk exists between the pathways activated by P2X7 receptors with those activated by M3 muscarinic or α1D adrenergic receptors. The mechanism of the crosstalk between P2X7 and M3 muscarinic receptors differs from that of the crosstalk between P2X7 and α1D adrenergic receptors. CONCLUSIONS: Understanding purinergic receptors and how they modulate protein secretion could play a key role in normal and pathological responses of the LG.

Conjunctival goblet cells synthesize and secrete mucins which play an important role in protecting the ocular surface. Pro-resolution mediators, such as lipoxin A4 (LXA4), are produced during inflammation returning the tissue to homeostasis and are also produced in non-inflamed tissues. The purpose of this study was to determine the actions of LXA4 on cultured human conjunctival goblet cell mucin secretion and increase in intracellular [Ca(2+)] ([Ca(2+)]i) and on histamine-stimulated responses. LXA4 increased mucin secretion and [Ca(2+)]i, and activated ERK1/2 in human goblet cells. Addition of LXA4 before resolvin D1 (RvD1) decreased RvD1 responses though RvD1 did not block LXA4 responses. LXA4 inhibited histamine-stimulated increases in mucin secretion, [Ca(2+)]i, and ERK1/2 activation through activation of β-adrenergic receptor kinase 1. We conclude that conjunctival goblet cells respond to LXA4 through the ALX/FPR2 receptor to maintain homeostasis of the ocular surface and regulate histamine responses and could provide a new therapeutic approach for allergic conjunctivitis and dry eye diseases.

PURPOSE: To compare the postoperative measurements of intraocular pressure (IOP) using the Corvis ST Tonometer (CST), ocular response analyzer (ORA), and Goldmann applanation tonometry (GAT) in eyes undergoing laser in situ keratomileusis (LASIK), as well as to analyze the relationship between the corneal biomechanical parameters of the CST and the ORA. METHODS: Fifty participants who had undergone LASIK to treat myopia in the previous 3 months were enrolled. Postoperative IOP measurements of these participants were obtained using the CST, ORA (corneal-compensated IOP [IOPcc], Goldmann-correlated IOP [IOPg]), and GAT. Device agreement was calculated by Bland-Altman analysis. The metrics of corneal biomechanical properties were recorded using the ORA and the CST. Corneal biomechanical parameters were compared. RESULTS: The Bland-Altman analysis revealed a significant bias between CST and GAT, between CST and IOPcc, and between CST and IOPg of 3.4, 1.0, and 3.8, mm Hg, respectively, with 95% limits of agreement of -0.7 to 7.5 mm Hg, -2.1 to 4.2 mm Hg, and -0.4 to 8.0 mm Hg. The ORA-derived IOP measurements, CST-derived IOP, and GAT IOP values showed good correlation with each other. The CST IOP and IOPcc were higher than the GAT IOP (all p < 0.05), whereas IOPg did not differ from the GAT IOP readings. Ocular response analyzer-derived corneal biomechanical parameters (corneal hysteresis and the corneal resistance factor) showed significant correlations with CST-derived parameters, including the maximum deformation amplitude at the corneal apex and the time from start until the first applanation. CONCLUSIONS: The CST offers an alternative method for measuring postoperative IOP in LASIK patients, and it appears to obtain higher IOP values than other tonometry techniques. The technique may facilitate the investigation of corneal biomechanical property changes in LASIK-treated eyes.

PURPOSE: Each year, over 8,000 corneal transplantation surgeries are performed in China. Unlike developed countries, which have established standard requirements for operative experience for corneal specialists, little information exists on surgical training for keratoplasty in China. The aim of this study was to assess the keratoplasty experience of Chinese corneal specialists and to characterize their surgical patterns. METHODS: One hundred and twenty-one corneal specialists in 16 provinces (65 cities) in China were invited to complete an anonymous survey at the 2014 Chinese Corneal Society annual meeting, which consisted of questions with single or multiple-choice answers. Demographics, the number and type of keratoplasties performed, and the perceived limiting factors for performing keratoplasties were analyzed. RESULTS: An overwhelming 89% response rate was achieved. Of the 108 respondents, 76% worked in tertiary centers, and only 23% held a medical doctorate degree. Furthermore, 69% of the participants had received corneal fellowship training of less than one year. Only 71% were capable of keratoplasties. Among those doing keratoplasty, 68% performed less than 50 keratoplasties each year. Of the same group of keratoplasty surgeons, 88% of corneal specialists capable of keratoplasties had performed penetrating keratoplasties, 87% had performed lamellar keratoplasties, 12% had performed deep anterior lamellar keratoplasties, and 5% had performed Descemet's stripping endothelial keratoplasties. When questioned on the reasons for the low number of keratoplasties performed in China, the respondents deemed the following factors most important: lack of surgical training (71%), a shortage of donor supply (52%), and a lack of curricula (42%). A multivariate logistic regression analysis showed that corneal transplantation capabilities are significantly associated with responders' education levels and training time. CONCLUSION: Keratoplasty surgery experience is suboptimal for Chinese corneal specialists. Penetrating and lamellar keratoplasties are the preferred surgical patterns. Our findings raise concerns about the adequacy of keratoplasty training in China.