Human Corneal Endothelial Research Articles

In Vitro Profiling of the Extracellular Matrix and Integrins Expressed by Human Corneal Endothelial Cells Cultured on Silk Fibroin-Based Matrices.

Developing a scaffold for culturing human corneal endothelial (HCE) cells is crucial as an alternative cell therapeutic approach to bridge the growing gap between the demand and availability of healthy donor corneas for transplantation. Silk films are promising substrates for the culture of these cells; however, their tensile strength is several-fold greater than the native basement membrane which can possibly influence the dynamics of cell-matrix interaction and the extracellular matrix (ECM) secreted by the cells in long-term culture. In our current study, we assessed the secretion of ECM and the expression of integrins by the HCE cells on Philosamia ricini (PR) and Antheraea assamensis (AA) silk films and fibronectin-collagen (FNC)-coated plastic dishes to understand the cell-ECM interaction in long-term culture. The expression of ECM proteins (collagens 1, 4, 8, and 12, laminin, and fibronectin) on silk was comparable to that on the native tissue. The thicknesses of collagen 8 and laminin at 30 days on both PR (4.78 ± 0.55 and 5.53 ± 0.51 μm, respectively) and AA (4.66 ± 0.72 and 5.71 ± 0.61 μm, respectively) were comparable with those of the native tissue (4.4 ± 0.63 and 5.28 ± 0.72 μm, respectively). The integrin expression by the cells on the silk films was also comparable to that on the native tissue, except for α3 whose fluorescence intensity was significantly higher on PR (p ≤ 0.01) and AA (p ≤ 0.001), compared to that on the native tissue. This study shows that the higher tensile strength of the silk films does not alter the ECM secretion or cell phenotype in long-term culture, confirming the suitability of using this material for engineering the HCE cells for transplantation.

Construction of tissue-engineered human corneal endothelium for corneal endothelial regeneration using a crosslinked amniotic membrane scaffold

Descemet's membrane endothelial keratoplasty (DMEK) may provide fast visual rehabilitation in the therapy of corneal endothelial disorders. However, due to shortage of donated corneas, how to construct a corneal endothelial substitute with powerful functions that can be used for DMEK is still unsolved. Herein, we introduced the method of corneal crosslinking (CXL) and conjugated the components of native Descemet's membrane (DM) to improve the mechanical properties and the biocompatibility of denuded amniotic membrane (dAM), further assessed their effects on cell adhesion, proliferation, YAP translocation, and metabolic activity in human corneal endothelial (HCE) cells. Using modified crosslinked dAM (mcdAM) and non-transfected HCE cells, we constructed a tissue-engineered HCE (TE-HCE) and evaluated its functions in cat and monkey models as well. Our results showed that the mechanical properties of mcdAM were improved effectively by CXL, and the adhesion, proliferation, and YAP translocation of HCE cells were dose-dependently improved after ECM modification. The combination of 0.01 mg/mL laminin with 0.1 mg/mL fibronectin showed the highest efficacy. Then, the TE-HCE was constructed in vitro, with a high density of 3612 ± 243 cells/mm2. Results of DMEK in animal models showed that corneal transparency was maintained, accompanied with normal morphology and histological structure of the regenerated corneal endothelium. Therefore, CXL combined with DM-mimic-coating methods could effectively improve the mechanical properties of dAM and enhance the biocompatibility with HCE cells. The constructed TE-HCE had normal histological structure and functioned well in animal models via DMEK, which could be used as a promising powerful equivalent of HCE. Statement of significanceUsing high-quality corneal endothelium and an appropriate endothelial keratoplasty is the most effective way for the treatment of corneal endotheliopathy. Descemet's membrane endothelial keratoplasty (DMEK) which can provide better visual acuity, lower immunological rejection rates, and improved graft survival is an ideal surgery at present. However, due to the shortage of donated corneas, it is urgent to find an equivalent substitute of corneal endothelial donor which is suitable for the DMEK surgery to solve the problem of corneal endothelial regeneration. Herein, we introduced the clinical cornea-crosslinking and Descemet's membrane-mimic-coating methods to build the modified crosslinked denuded amniotic membrane scaffold and further constructed a high-quality corneal endothelial functional substitute that can be used in DMEK surgery.

Feasibility Study of Human Corneal Endothelial Cell Transplantation Using an In Vitro Human Corneal Model.

To test the feasibility of a cell therapy approach to treat corneal endothelial (CE) disorders using an in vitro model of human corneal decompensation. A CE decompensation model was established by removal of the Descemet membrane/endothelium complex from cadaveric human corneas in an air interface organ culture system (group 2) and compared with normal corneas (group 1). The posterior stroma of decompensated corneas was seeded with immortalized human corneal endothelial cells (HCEC-12) in group 3 and passage 0 primary human CE cells in group 4 corneas. Functional effects on stromal thickness were determined with histological analysis 3 to 10 days after cell therapy treatment. Removal of the Descemet membrane/endothelium complex in group 2 corneas resulted in a stromal thickness of 903 ± 86 μm at 12 hours compared with 557 ± 72 μm in group 1 corneas. Stromal thickness reduced from 1218 ± 153 μm to 458 ± 90 μm (63% ± 6%, P = 0.001) after cell transplantation in group 3 and from 1100 ± 86 μm to 489 ± 94 μm (55% ± 7%, P = 0.00004) in group 4. Posttransplantation histology demonstrated formation of a monolayer of corneal endothelium attached to the posterior stromal surface. Direct transplantation of cultured human CE cells and immortalized HCEC-12 to bare posterior corneal stroma resulted in formation of an endothelial monolayer and restoration of stromal hydration to physiological thickness, demonstrating the feasibility of cell therapy in treatment of CE decompensation in a human in vitro model.

Corneal endothelial cells activate innate and acquired arm of anti-viral responses after cytomegalovirus infection

Infection of the corneal endothelial cells by human cytomegalovirus (CMV) is an important cause of corneal endotheliitis. CMV endotheliitis is difficult to completely cure and relapses are frequent. This can cause blinding corneal bullous keratopathy. However, the pathogenesis of CMV endotheliitis remains undetermined. To understand the immunopathology of endotheliitis, we examined how corneal endothelial cells prime the anti-viral immunity after CMV infection based on global transcriptional responses. To accomplish this, human corneal endothelial (HCEn) cells were infected with CMV, and the global transcriptional responses were determined by microarray analyses for primary anti-viral responses using network analysis. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and protein array analyses were used to examine whether anti-viral cytokines were induced, i.e., to determine whether innate immune responses were activated. To examine whether priming of acquired immune response was activated, CMV-infected HCEn cells were co-cultured with allogeneic CD8+ T cells from CMV seropositive donors and tested for priming activity for the CD8+ effector T cells by measuring interferon-γ secretion. The CMV-induced responses of HCEn cells were characterized by type I interferon and pattern recognition receptor pathways which represent innate immune priming. The global transcriptional activation was specifically associated with antigen presentation with the antimicrobial response functions. Protein array analyses indicated a significant increase in the secretion of anti-viral inflammatory cytokines including CXCL10 as innate immune responses. When HCEn cells were examined to determine whether CMV infection activated anti-viral acquired immunity, CMV-infected HCEn cells directly stimulated the proliferation of CD8+ T cells from CMV-seropositive donors, and pp65 viral epitope induced interferon-γ secretion from the CD8+ T cells. We conclude that CMV-infected HCEn cells induce innate immune priming along with provisions of acquired immune priming of CD8+ effector T cells. This information should help in the development of useful diagnostic procedures and efficacious therapeutic strategy to treat refractory corneal endotheliitis.

Net Fluorescein Flux Across Corneal Endothelium Strongly Suggests Fluid Transport is due to Electro-osmosis.

We have presented prior evidence suggesting that fluid transport results from electro-osmosis at the intercellular junctions of the corneal endothelium. Such phenomenon ought to drag other extracellular solutes. We have investigated this using fluorescein-Na2 as an extracellular marker. We measured unidirectional fluxes across layers of cultured human corneal endothelial (HCE) cells. SV-40-transformed HCE layers were grown to confluence on permeable membrane inserts. The medium was DMEM with high glucose and no phenol red. Fluorescein-labeled medium was placed either on the basolateral or the apical side of the inserts; the other side carried unlabeled medium. The inserts were held in a CO2 incubator for 1 h (at 37 °C), after which the entire volume of the unlabeled side was collected. After that, label was placed on the opposite side, and the corresponding paired sample was collected after another hour. Fluorescein counts were determined with a (Photon Technology) DeltaScan fluorometer (excitation 380 nm; emission 550 nm; 2 nm bwth). Samples were read for 60 s. The cells utilized are known to transport fluid from the basolateral to the apical side, just as they do in vivo in several species. We used 4 inserts for influx and efflux (total: 20 1-h periods). We found a net flux of fluorescein from the basolateral to the apical side. The flux ratio was 1.104 ± 0.056. That difference was statistically significant (p = 0.00006, t test, paired samples). The endothelium has a definite restriction at the junctions. Hence, an asymmetry in unidirectional fluxes cannot arise from osmosis, and can only point instead to paracellular solvent drag. We suggest, once more, that such drag is due to electro-osmotic coupling at the paracellular junctions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00232-016-9887-0) contains supplementary material, which is available to authorized users.

Cytotoxicity of proparacaine to human corneal endothelial cells <i>in vitro </i>

Proparacaine is a widely used topical anesthetic in ophthalmic optometry and surgery, and has been reported to have cytotoxic effects on rabbit corneal endothelial cells after prolonged and repeated usage. Since rabbit is an exceptive mammal whose corneal endothelial cells still maintaining proliferation abilities even in adulthood, whether proparacaine has cytotoxic effects on human corneal endothelial (HCE) cells need to be further verified. Our objectives in the present study were to investigate the cytotoxicity to HCE cells of proparacaine and its underlying mechanisms in vitro and verify the cytotoxicity using cat corneal endothelial (CCE) cells in an in vivo model of cat corneas. Cytotoxic evaluation results indicated that a dose- and time-dependent toxic response of HCE cells to proparacaine over 0.03125% was rated based on morphology and viability, and a toxic response of CCE cells to 0.5% (clinical applied dosage) proparacaine was also rated based on cell density and histology. Importantly, treatment with proparacaine resulted in significant elevation of plasma membrane permeability, cell cycle arrest at S phase, fragmentation of genomic DNA, formation of apoptotic bodies, and externalization of phosphatidylserine (PS) of HCE cells. Moreover, proparacaine demonstrated disrupting effects on mitochondrial transmembrane potential (MTP) of HCE cells and activating effects on caspase-3, -8 and -9. This study demonstrates that proparacaine has notable cytotoxicity to both HCE cells in vitro and CCE cells in vivo, and its dose- and time-dependent cytotoxicity to HCE cells is achieved by inducing apoptosis via a mitochondrion-mediated caspase-dependent pathway. These findings provide new insights into the cytotoxicity and apoptosis-inducing effect of local anesthetics which should be used with great caution in the eye clinic.

Dose dependent cytotoxicity of pranoprofen in cultured human corneal endothelial cells by inducing apoptosis

Pranoprofen (PPF), a non-steroidal anti-inflammatory drugs (NSAIDs), is often used in keratitis treatment in clinic. Several studies have assessed in vitro the cytotoxicity of topical NSAIDs to corneal epithelial cells due to its importance for predicting human corneal toxicity. Damage by cytotoxic drugs can result in excessive loss of human corneal endothelial (HCE) cells which lead to decompensation of the endothelium and eventual loss of visual acuity. However, the endothelial cytotoxicity of PPF has not yet been reported using an in vitro model of HCE cells. This study assessed the cytotoxicity of PPF to HCE cells and its underlying mechanism. Cellular viability was determined using inverted phase contrast light microscopy, and plasma membrane permeability, genomic DNA fragmentation, and ultrastructure were detected by acridine orange/ethidium bromide staining, DNA agarose gel electrophoresis, and transmission electron microscopy (TEM), respectively. The results on cellular viability showed that PPF at concentrations ranging from 0.0625 to 1.0 g/l had poignant cytotoxicity to HCE cells, and the extent of its cytotoxicity was dose- and time-dependent. Further characterization indicated that PPF induced plasma membrane permeability elevation, DNA fragmentation, and apoptotic body formation, proving its apoptosis inducing effect on HCE cells. In conclusion, PPF above 0.0625 g/l has poignant cytotoxicity on HCE cells in vitro by inducing cell apoptosis, and should be carefully employed in eye clinic.

Cytotoxicity of Lidocaine to Human Corneal Endothelial Cells In Vitro

Lidocaine has been reported to induce apoptosis on rabbit corneal endothelial cells. However, the apoptotic effect and exact mechanism involved in cytotoxicity of lidocaine are not well-established in human corneal endothelial (HCE) cells. In this study, we investigated the apoptosis-inducing effect of lidocaine on HCE cells in vitro. After HCE cells were treated with lidocaine at concentrations of 0.15625-10.0g/l, the morphology and ultrastructure of the cells were observed by inverted light microscope and transmission electron microscope (TEM). Cell viability was measured by MTT assay, and the apoptotic ratio was evaluated with flow cytometry and fluorescent microscopic counting after FITC-Annexin V/PI and AO/EB staining. DNA fragmentation was detected by electrophoresis, and the activation of caspases was evaluated by ELISA. In addition, changes in mitochondrial membrane potential were determined by JC-1 staining.Results suggest that lidocaine above 1.25g/l reduced cellular viability and triggered apoptosis in HCE cells in a time- and dose-dependent manner. Diminishment of ΔΨm and the activation of caspases indicate that lidocaine-induced apoptosis was caspase dependent and may be related to mitochondrial pathway.

Roles Played by Toll-like Receptor-9 in Corneal Endothelial Cells after Herpes Simplex Virus Type 1 Infection

To determine the roles played by toll-like receptor 9 (TLR9) in cultured human corneal endothelial (HCEn) cells after herpes simplex virus type 1 (HSV-1) infection and to characterize the TLR9-mediated antiviral responses. Immortalized HCEn cells were examined for TLR expression. The upregulation of inflammatory cytokines after HSV-1 infection was determined by real-time RT-PCR or protein array analyses. The TLR9-mediated HSV-1 replication was determined by real-time PCR and plaque assay. To determine whether there was an activation of the signal transduction pathway, HCEn cells that were transfected with pathway-focused transcription factor reporters were examined for promoter activity. TLR9 was abundantly expressed intracellularly in HCEn cells. The CpG oligonucleotide, a TLR9 ligand, stimulated the NF-κB activity in HCEn cells. HSV-1 infection also stimulated NF-κB and induced NF-κB -related inflammatory cytokines, including RANTES, IP-10, MCP-2, MIF, MCP-4, MDC, MIP-3α, IL-5, TARC, MCP-1, and IL-6. The induction of these cytokines was significantly reduced by blocking the activity of TLR9. In addition, viral replication in HCEn cells was significantly reduced by the inhibition of TLR9, but was preserved by a concomitant activation of the NF-κB cascade. Of the different HSV-1-induced inflammatory cascade-related transcription factors, TLR9 was found to activate NF-κB, cyclic AMP response element (CRE), and the CCAAT-enhancer-binding proteins (C/EBP) the most. Corneal endothelial cells transcriptionally initiate inflammatory programs in response to HSV-1 infection related to NF-κB, CRE, and C/EBP and express arrays of inflammatory cytokine induction by TLR9. On the other hand, HSV-1 exploits TLR9-mediated NF-κB activation for its own replication.

Herpes Simplex Virus Type 1–Induced Transcriptional Networks of Corneal Endothelial Cells Indicate Antigen Presentation Function

To determine the transcriptional response of cultured human corneal endothelial (HCEn) cells after herpes simplex virus type (HSV-1) infection and to characterize the primary functional elements and antiviral responses. Immortalized HCEn cells were infected with HSV-1, and the global transcriptional profile was determined. The transcriptional networks of HCEn cells were constructed, and the inflammatory network nodes were evaluated for induction of candidate inflammatory mediators by protein array analyses. HSV-1-specific allogeneic T cells isolated from HSV-1-infected donors were co-cultured with HSV-1-pulsed HCEn cells, and T cell activation was assessed for antigen-specific proliferation. HSV-1 infection induced a global transcriptional activation with 331 genes significantly up- or downregulated compared with mock-infected HCEn cells (P < 0.01; 4< or 0.25> threshold). Network analysis showed that the HSV-1-induced transcriptome was specifically associated with antigen presentation, interferon-related responses, and cellular development, and was characterized by NF-κB and extracellular signal-regulated kinase signaling pathways. The primary associated function in the transcriptome was antigen presentation. Protein array analysis identified significant elevation of genes related to antigen presentation: IL-6, IP-10, HVEML, and interferon-γ. In addition, inflammatory cytokines including IL-8, MCP-1, TIMP-1, RANTES, I-309, MIF, MCP-2, IL-10, and SDF-1, in descending order, were significantly elevated. Mixed lymphocyte reaction assays showed that HSV-1-pulsed HCEn cells stimulated antigen-specific proliferation of allogeneic T lymphocytes. HCEn cells respond to HSV-1 infection by initiating antigen presentation-related inflammatory responses, and they may serve as antigen-presenting cells.

Aspirin-Triggered Lipoxin A4 (15-epi-LXA4) Increases the Endothelial Viability of Human Corneas Storage in Optisol-GS

The human corneal endothelium has a very low mitotic rate, and with aging there is a decrease in the number of cells. 15-epi-LXA4 is an anti-inflammatory, bioactive lipid formed when aspirin acetylates cyclooxygenease-2 and redirects cyclooxygenease-2 catalytic activity away from prostaglandins. The purpose of the current study was to evaluate the action of 15-epi-LXA4 in the endothelium viability of human corneas stored in Optisol-GS. Human corneal endothelial (HCE) cells along with the Descemet's membrane were isolated from fresh human eyes obtained from National Disease Research Interchange. Cell phenotype was identified by using the tight junctions cell marker ZO-1. LXA4 receptor (FPR2/ALX) was detected by immunostaining of HCE cells and human corneal tissue using a polyclonal antibody. Cell proliferation was evaluated with Ki-67 antibody. To measure cell migration, confluent HCE cells were wounded by a linear scraping with a sterile pipette tip in the center of the well and incubated for 24 h with or without 15-epi-LXA4. To evaluate the reparative capacity of 15-epi-LXA4, 7 pairs of human corneas were incubated in Dulbecco's modified Eagle's medium/F12 media at 37°C with or without 100 nM 15-epi-LXA4 for 24 h and then stored at 4°C in Optisol-GS for 12 days. Endothelial viability was assessed by 2 staining techniques: a viability/cytotoxicity kit and trypan blue combined with alizarin red S. HCE cells and the endothelium of human corneal sections strongly expressed the LXA4 receptor. There was a 3-fold increase in cell proliferation when HCE cells were incubated with 100 nM 15-epi-LXA4 for 24 h. No significant migration was observed after 24 h incubation with 15-epi-LXA4. Corneas incubated for 24 h in Dulbecco's modified Eagle's medium/F12 media in the presence of 15-epi-LXA4 and then stored for 12 days in Optisol-GS had a 36% to 56% increase in viability compared with controls without 15-epi-LXA4. 15-epi-LXA4 is an important mediator that protects the integrity of the human endothelium during corneal preservation in Optisol-GS.

Physiologie des humanen Hornhautendothels – neue Erkenntnisse durch elektrophysiologische Untersuchungen

Currently, the identification of apoptotic or damaged human corneal endothelial (HCE) cells is limited to a morphological assessment and vital staining. Specific electrophysiological investigations may prospectively help to identify damaged HCE cells at an earlier stage. Besides calcium imaging, the so-called patch-clamp technique is an important test method enabling one to assay the effect of various substances on ion channels and receptors of the cell membrane. First electrophysiological pilot experiments with cultivated and freshly isolated HCE cells have revealed promising results. In this way, the expression of certain transient receptor potential channels (TRPs) could be demonstrated. However, the function of these channels is still not fully elucidated. In humans, TRPs play a crucial role in the sense of taste, pheromones, temperature and pain and are involved in osmolarity. This review summarises the current literature on the electrophysiology of the human corneal endothelium and deduces potential approaches to a sensitive vitality and function test under utilisation of the electrophysiological properties of HCE cells.

Mechanisms of Immune Suppression for CD8+T Cells by Human Corneal Endothelial Cells via Membrane-Bound TGFβ

To determine whether CD8(+) T cells in vitro are suppressed or converted into regulators (Treg cells) by human corneal endothelial (HCE) cells. HCE cell lines were established from primary HCE cells, and allogeneic CD8(+) T cells were isolated from peripheral blood mononuclear cells of healthy donors. T-cell activation was assessed for proliferation by [(3)H]-thymidine incorporation. Expression of TGFbeta on HCE cells was evaluated by flow cytometry, RT-PCR, and immunohistochemistry. Anti-TGFbeta-neutralizing antibodies or TGFbeta siRNA was used to abolish the HCE-mediated inhibitory function. CD8(+) T cells exposed to HCE cells were used as Treg cells, to induce Treg cells in vitro by exposure to HCE cells. Expression of CD25 or Foxp3 on Treg cells was evaluated by flow cytometry. Cultured HCE cells produced the membrane-bound active TGFbeta isoform 2. HCE surface TGFbeta2 was necessary, to inhibit CD8(+) T-cell activation via direct cell contact. In addition, although HCE cells were found to constitutively express costimulatory molecules, such as programmed death-ligand 1 (PD-L1) and PD-L2, and secreted thrombosponsin-1, only membrane-bound TGFbeta2 was actually delivered to the CD8(+) T cells. HCE cells were also found to convert some CD8(+) T-cell populations into Treg cells via their membrane-bound TGFbeta. These HCE-induced Treg cells produced soluble forms of TGFbeta1, but not of TGFbeta2, and they also acquired a regulatory phenotype that expressed CD25(high) and Foxp3. Ocular resident tissue-exposed T cells can be suppressed or induced to become regulators within the human peripheral microenvironment.

Human Corneal Endothelial Cells Expressing Programmed Death-Ligand 1 (PD-L1) Suppress PD-1+T Helper 1 Cells by a Contact-Dependent Mechanism

This study was designed to determine whether human corneal endothelial (HCE) cells could regulate the activation of bystander T cells in vitro. HCE cell lines were established from primary HCE cells. Target-activated T cells were used allogeneic T cells and Jurkat T-cell lines. As an additional target, T-cell clones from uveitis patients were established from aqueous humor via a limiting dilution. T-cell activation was assessed for proliferation by [(3)H]-thymidine incorporation, carboxyfluorescein succinimidyl ester incorporation, or IFNgamma production. Expression of co-stimulatory molecules on IFNgamma-treated corneal endothelial and non-treated cells was evaluated by flow cytometry, RT-PCR, or immunohistochemistry. Expression of co-stimulatory receptors on target T cells was evaluated by flow cytometry. Blocking antibodies was used to abolish the HCE-inhibitory function. HCE cells suppressed both in vitro proliferation and IFNgamma production by CD4(+) T cells via a cell contact-dependent mechanism. HCE constitutively expressed co-stimulatory molecules programmed death-ligand 1 (PD-L1) and PD-L2, and their expression was enhanced by IFNgamma. HCE efficiently inhibited the proliferation of Th1 cells that overexpressed PD-1 among various activated T-cell lines and clones established from patients with uveitis or corneal endotheliitis. A neutralizing mAb for PD-L1, but not PD-L2, blocked the suppressive effect of HCE on Th1 cells. HCE can impair the effector functions and activation of Th1 infiltrating CD4(+) T cells via the PD-1/PD-L1 interaction. The data support the hypothesis that corneal endothelium may contribute to maintenance of the privileged immune status of the anterior chamber of the eye by inducing peripheral immune tolerance.

VIP and VIP Gene Silencing Modulation of Differentiation Marker N-Cadherin and Cell Shape of Corneal Endothelium in Human Corneas Ex Vivo

Vasoactive intestinal peptide (VIP) is expressed by corneal endothelial (CE) cells and is present in the aqueous humor, which bathes CE cells in vivo. This study demonstrated the role of CE cell VIP in maintaining the expression level of a CE differentiation marker, N-cadherin, and the hexagonal cell shape. To determine the most effective VIP concentration, bovine corneoscleral explants were treated with 0 (control) and 10(-12) to 10(-6) M VIP. Paired human corneas (nine donors) from an eye bank were used as control; the other corneas were treated with VIP. To silence endogenous VIP, paired fresh human donor corneas (from seven cadavers) were transduced with VIP shRNA or the control lentiviral particles and then bisected/quartered for quantitative analysis by semiquantitative RT-PCR (for mRNA) and Western blot analysis/immunocytochemistry (for protein), whereas alizarin red S staining revealed CE cell shape. VIP concentration dependently increased bovine CE cell N-cadherin mRNA levels, with the maximal effect observed between 10(-10) (1.47 +/- 0.06-fold; P = 0.002) and 10(-8) M VIP (1.48 +/- 0.18-fold; P = 0.012). VIP (10(-8) M) treatment increased N-cadherin protein levels in bovine and human CE cells to 1.98 +/- 0.28-fold (P = 0.005) and 1.17 +/- 0.10 (range, 0.91-1.87)-fold (P = 0.050) of their respective controls. VIP antagonist (SN)VIPhyb diminished the VIP effect. VIP silencing resulted in deterioration of the hexagonal cell shape and decreased levels of VIP protein and mRNA, N-cadherin (but not connexin-43) mRNA and protein, and the antiapoptotic Bcl-2 protein. Through its autocrine VIP, CE cells play an active role in maintaining the differentiated state and suppressing apoptosis in the corneal endothelium in situ.

Vasoactive intestinal peptide induction by ciliary neurotrophic factor in donor human corneal endothelium in situ

After peripheral nerve axotomy, vasoactive intestinal peptide (VIP) gene expression is upregulated in neurons, whereas ciliary neurotrophic factor (CNTF) accumulates extracellularly at the lesion site. Although CNTF-induced VIP gene expression has been reported in cultured sympathetic neurons and neuroblastoma cells, it still remains to be determined if CNTF and VIP play interrelated roles in nerve injury. The corneal endothelium, like sympathetic neurons, derives from the neural crest. Previously, we demonstrated that a sublethal-level of oxidative stress induces CNTF release from corneal endothelial (CE) cells in situ. Here, we show that human CE cells express the 53 kDa ligand-binding alpha subunit of the CNTF receptor (CNTFRalpha). We further demonstrate that CNTF induces VIP immunoreactivity in human donor corneas. To determine if the increase in VIP immunoreactivity was reflected by an increase in gene expression, donor human corneas were bisected and treated with CNTF or vehicle, and analyzed by real-time RT-qPCR. Two experiments using different sets of bisected corneas indicated that CNTF induced increases in VIP mRNA levels of 6.5+/-2.2-fold (N=7 corneas) and 2.3+/-0.6-fold (N=10 corneas) (mean+/-S.E.M.), respectively. Whereas VIP is produced as a CE autocrine factor against oxidative stress, the present study suggested that oxidative stress-released CNTF plays a role in protecting CE cells against oxidative stress injury by upregulating VIP expression.

Distribution of Precursors in Human Corneal Stromal Cells and Endothelial Cells

We identified original tissue-committed precursors with limited self-renewal capacity from human corneal stromal (HCS) cells and human corneal endothelial (HCE) cells, then tried to determine the distribution and proliferative capacity of the precursors. Experimental study. Eighteen human corneas from donors 56 to 68 years old. Human corneal stromal cells were divided into groups based on distance from the center of the cornea: <6 mm (central), 6 to 8 mm (paracentral), and 8 to 10 mm (peripheral). Human corneal endothelial cells were separated into 2 groups: <7.5 mm (central) and 7.5 to 10 mm (peripheral) from the center. Each group was subjected to the sphere-forming assay using serum-free medium containing growth factors in floating culture. Sphere numbers and the proliferative capacity of spheres in adherent culture were compared among the groups. Density and proliferative capacity of precursors from each area of HCS and HCE cells. Primary spheres were isolated from all groups of HCS and HCE cells. The rate of primary sphere formation from peripheral HCS cells was higher than those of the other 2 groups, being 1.5-fold greater than in the paracentral cornea and 4-fold greater than in the central cornea. The rate of primary sphere formation by peripheral HCE cells was significantly higher than that by central HCE cells, being 4-fold greater than in the central cornea. There were no differences in the proliferative capacity of HCS and HCE cell spheres from the different areas after adherent culture. All HCS and HCE cells contain a significant number of precursors, but the peripheral cells have a density of precursors higher than that of the central cells. Precursors from each area do not show differences of proliferative capacity. Our findings may in part explain changes after excimer laser treatment and may have implications for corneal transplantation procedures.