Up-regulation of semaphorin 3A in human corneal fibroblasts by epidermal growth factor released from cocultured human corneal epithelial cells

Morphological analysis of cell distribution and network structure via gap junctions in swine corneal stroma

Because of corneal transplantation limitations, there is a need for cornea-specific regenerative medicine. The development of such regenerative medicine has been delayed because of the complex and unique structure of the corneal stroma. Few studies have explored the corneal stroma cell distribution and cell types in vivo. This study investigated regional differences in morphological characteristics and distributions of corneal keratocytes and immunocompetent cells in the corneal stroma to clarify their functions and structural characteristics. The porcine eyeballs were subjected to light microscopy, transmission electron microscopy, scanning electron microscopy, and immunofluorescence staining analyses. Corneal cells were primarily located in the limbus, rather than the center of the cornea; the long keratocyte diameter was largest on the epithelial side of the corneal limbus, while the short diameter was largest on the endothelial side of the central cornea. Moreover, there were significantly more corneal cells on the epithelial side than on the endothelial side in both the central and limbus areas. Gap junctions between cells in the corneal stroma were present on the surfaces of cytoplasmic processes. Many cytoplasmic processes were scattered throughout the corneal stroma; they were connected both vertically and horizontally, forming an intercellular network. Additionally, immunocompetent cells on the epithelial side suggested to participate in this network via gap junctions. The morphology of keratocytes and immunocompetent cells on the epithelial side suggests that they play important roles in corneal homeostasis.

The Impact of Different Oxygen Delivery Methods on Corneal Epithelial Repair after Injury

The hyperbaric oxygen therapy is often used in the management of acid and base burns of the eyes. However, oxygen is rarely supplied locally through goggles or face mask in ophthalmology. Therefore, in this study, we aim to investigate how oxygen delivery affects eye recovery after injury. We used a rabbit model with corneal epithelial injury to examine the effects of local oxygen supply via goggles or face mask on the recovery of cornea. A total of 75 healthy New Zealand white rabbits were randomly divided into three groups, A, B, and C, with 25 rabbits in each group. Then, on each rabbit eye (150 eyes in total), a circle of corneal epithelium with 5 mm in diameter was scraped off from the center of the cornea with a corneal epithelial scraper. Group A was given oxygen goggles every day (the oxygen flow rate was 3 L/min, once a day, 2 hours each time); group B was given nasal inhalation of oxygen every day (the oxygen flow rate was 3 L/min, once a day, 2 hours each time); and group C did not receive any treatment and was healed naturally. We found that the group A, which received oxygen supply via goggles, showed the best eye recovery. Transmission electron microscopy showed that the cornea with local oxygen supply via goggles or face mask exhibited intact capillary structure and obvious desmosome/hemidesmosome connections between cells. Moreover, the protein and RNA levels of hypoxia-related genes were lower in group A and B, suggesting that the hypoxia factor is a sensitive and early regulator in the low oxygen environment.

Semaphorin 3A potentiates the profibrotic effects of transforming growth factor-β1 in the cornea

Corneal scarring is a major cause of blindness worldwide with few effective therapeutic options. Finding a treatment would be of tremendous public health benefit, but requires a thorough understanding of the complex interactions that underlie this phenomenon. Here, we tested the hypothesis that the large increase in expression of Semaphorin 3A (SEMA3A) in corneal wounds contributes to the development of stromal fibrosis. We first verified this increased expression in vivo, in a cat model of photorefractive keratectomy-induced corneal wounding. We then examined the impact of adding exogenous SEMA3A to cultured corneal fibroblasts, and assessed how this affected the ability of transforming growth factor-beta1 (TGF-β1) to induce their differentiation into myofibroblasts. Finally, we examined how siRNA knockdown of endogenous SEMA3A affected these same phenomena. We found exogenous SEMA3A to significantly potentiate TGF-β1's profibrotic effects, with only a minimal contribution from cell-intrinsic SEMA3A. Our results suggest a previously unrecognized interaction between SEMA3A and TGF-β1 in the wounded cornea, and a possible contribution of SEMA3A to the regulation of tissue fibrosis and remodeling in this transparent organ.

Peptide therapies for ocular surface disturbances based on fibronectin-integrin interactions

The condition of the corneal epithelium is a critical determinant of corneal transparency and clear vision. The corneal epithelium serves as a barrier to protect the eye from external insults, with its smooth surface being essential for its optical properties. Disorders of the corneal epithelium include superficial punctate keratopathy, corneal erosion, and persistent epithelial defects (PEDs). The prompt resolution of these disorders is important for minimization of further damage to the cornea. Currently available treatment modalities for corneal epithelial disorders are based on protection of the ocular surface in order to allow natural healing to proceed. PEDs remain among the most difficult corneal conditions to treat, however. On the basis of characterization of the pathobiology of PEDs at the cell and molecular biological levels, we have strived to develop new modes of treatment for these defects. These treatments rely on two key concepts: provision of a substrate, such as the adhesive glycoprotein fibronectin, for the attachment and migration of corneal epithelial cells, and activation of these cells by biological agents such as the combination of substance P and insulin-like growth factor-1 (IGF-1). Central to both approaches is the role of the fibronectin-integrin system in corneal epithelial wound healing. Determination of the minimum amino acid sequences required for the promotion of corneal epithelial wound closure by fibronectin (PHSRN) and by substance P (FGLM-amide) plus IGF-1 (SSSR) has led to the development of peptide eyedrops for the treatment of PEDs that are free of adverse effects of the parent molecules.

Up-regulation of semaphorin 4A expression in human retinal pigment epithelial cells by PACAP released from cocultured neural cells

Development and homeostasis of multicellular organisms require interactions between neighbouring cells. We recently established an in vitro model of cell-cell interaction based on a collagen vitrigel membrane. We have now examined the role of neural cells in retinal homeostasis by coculture of human retinal pigment epithelial (RPE) cells and neural cells on opposite sides of such a membrane. The neural cells (differentiated PC12 cells) induced up-regulation of semaphorin 4A (Sema4A), a member of the semaphorin family of neural guidance proteins, in RPE (ARPE19) cells. This effect of the neural cells was mimicked by the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and was abolished by the PACAP antagonist PACAP(6-38). Coculture with neural cells or stimulation with PACAP also induced the phosphorylation of extracellular-signal-regulated kinase in ARPE19 cells, and this effect of the neural cells was inhibited by PACAP(6-38). Finally, among various cytokines examined, only the amount of interleukin-6 released by cocultures of ARPE19 and neural cells differed from that released by ARPE19 cells cultured alone. Interleukin-6 was not detected in culture supernatants of neural cells, and the reduction in the amount of interleukin-6 released by the cocultures compared with that released by ARPE19 cells alone was prevented by PACAP(6-38). Our findings suggest that PACAP released from retinal neural cells (photoreceptors or optic nerve cells) may regulate Sema4A expression in RPE cells and thereby contribute to the maintenance of retinal structure and function. Development and homeostasis of multicellular organisms require interactions between neighbouring cells. With the use of a coculture system based on a collagen vitrigel membrane, we have now shown that neural cells induce up-regulation of the neural guidance protein Sema4A in RPE cells. This effect of neural cells appears to be mediated by the neuropeptide PACAP. PACAP released from retinal neural cells (photoreceptors or optic nerve cells) may thus regulate Sema4A expression in RPE cells and thereby contribute to the maintenance of retinal structure and function.

The semaphorin 3A inhibitor SM-345431 accelerates peripheral nerve regeneration and sensitivity in a murine corneal transplantation model

Background

Peripheral nerve damage of the cornea is a complication following surgery or infection which may lead to decreased visual function. We examined the efficacy of the semaphorin 3A inhibitor, SM-345431, in promoting regeneration of peripheral nerves in a mouse corneal transplantation model.

Methodology/Principal Findings

P0-Cre/Floxed-EGFP mice which express EGFP in peripheral nerves cells were used as recipients of corneal transplantation with syngeneic wild-type mouse cornea donors. SM-345431 was administered subconjunctivally every 2 days while control mice received vehicle only. Mice were followed for 3 weeks and the length of regenerating nerves was measured by EGFP fluorescence and immunohistochemistry against βIII tubulin. Cornea sensitivity was also measured by the Cochet-Bonnet esthesiometer. CD31 staining was used to determine corneal neovascularization as a possible side effect of SM-345431. Regeneration of βIII tubulin positive peripheral nerves was significantly higher in SM-345431 treated mice compared to control. Furthermore, corneal sensitivity significantly improved in the SM-345431 group by 3 weeks after transplantation. Neovascularization was limited to the peripheral cornea with no difference between SM-345431 group and control.

Conclusions/Significance

Subconjunctival injections of SM-345431 promoted a robust network of regenerating nerves as well as functional recovery of corneal sensation in a mouse keratoplasty model, suggesting a novel therapeutic strategy for treating neurotrophic corneal disease.

EGFR signaling modulates synaptic connectivity via Gurken

Synaptic target selection is critical for establishing functional neuronal circuits. The mechanisms regulating target selection remain incompletely understood. We describe a role for the EGF receptor and its ligand Gurken in target selection of octopaminergic Type II neurons in the Drosophila neuromuscular system. Mutants in happyhour, a regulator of EGFR signaling, form ectopic Type II neuromuscular junctions. These ectopic innervations are due to inappropriate target selection. We demonstrate that EGFR signaling is necessary and sufficient to inhibit synaptic target selection by these octopaminergic Type II neurons, and that the EGFR ligand Gurken is the postsynaptic, muscle-derived repulsive cue. These results identify a new pathway mediating cell-type and branch-specific synaptic repulsion, a novel role for EGFR signaling in synaptic target selection, and an unexpected role for Gurken as a muscle-secreted repulsive ligand.

Differential expression of semaphorin 3A and its receptors during mouse retinal development

Semaphorins not only function in axon guidance during development but also contribute to various other biological processes. We have now examined the expression of semaphorin 3A (Sema3A) and its receptor components neuropilin 1 (Npn1) and plexin A (PlxA) during development of the mouse retina. Immunohistofluorescence analysis revealed that the expression patterns of Sema3A and Npn1 were similar during embryonic and postnatal development. The expression pattern of PlxA was also similar to those of Sema3A and Npn1 during embryonic and early postnatal (before eye opening) developments. However, the pattern of PlxA expression changed markedly after eye opening, with the expression disappearing from the optic nerve and increasing in intensity in the retinal pigment epithelium. Immunoprecipitation analysis showed that Sema3A interacted with PlxA in the retinal pigment epithelial cell line ARPE19 but not in the retinal ganglion cell line RGC5, whereas the opposite pattern of association was apparent for Sema3A and Npn1. Given that atmospheric oxygen is thought to play a role in the differentiation and maintenance of various ocular cell types, our results suggest that Sema3A-PlxA signalling activated by an effect of ambient oxygen on PlxA expression may contribute to differentiation of the retinal pigment epithelium.

Estrogen up-regulation of semaphorin 3F correlates with sympathetic denervation of the rat uterus

Current evidence indicates that rises in systemic levels of estrogen create in the uterus an inhibitory environment for sympathetic nerves. However, molecular insights of these changes are far from complete. We evaluated if semaphorin 3F mRNA, a sympathetic nerve repellent, was produced by the rat uterus and if its expression was modulated by estrogen. We also analyzed whether uterine nerves express the semaphorin 3F binding receptor, neuropilin-2. Uterine levels of semaphorin 3F mRNA were measured using real time reverse transcriptase-polymerase chain reaction in prepubertal rat controls and following chronic estrogen treatment. Localization of semaphorin 3F transcripts was determined by in situ hybridization and the expression of neuropilin-2 was assessed by immunohistochemistry. These studies showed that: (1) chronic estrogen treatment led to a 5-fold induction of semaphorin 3F mRNA in the immature uterus; (2) estrogen provoked a tissue-specific induction of semaphorin 3F which was particularly localized in the connective tissue that borders muscle bundles and surrounds intrauterine blood vessels; (3) two major cell-types were recognized in the areas where transcripts were concentrated, fibroblast-like cells and infiltrating eosinophil leukocytes; and (4) some delicate nerve terminal profiles present in the estrogenized uterus were immunoreactive for neuropilin-2. Temporal and spatial expression patterns of semaphorin 3F/neuropilin-2 are consistent with a possible role of this guidance cue in the remodeling of uterine sympathetic innervation by estrogen. Though correlative in its nature, these data support a model whereby semaphorin 3F, in combination with other inhibitory molecules, converts the estrogenized myometrium to an inhospitable environment for sympathetic nerves.

Regulation of soluble interleukin-6 (IL-6) receptor release from corneal epithelial cells and its role in the ocular surface

PURPOSE

Interleukin (IL)-6 signaling through its soluble receptor (sIL-6R) (IL-6 trans-signaling) plays an important role in various inflammatory states. We investigated production of sIL-6R in the corneal epithelium and examined the role of IL-6 trans-signaling in the cornea.

METHODS

In-vitro experiments were performed using SV40-transformed human corneal epithelial cells (HCEC) and primary human corneal fibroblasts (HCF, keratocytes). Ectodomain shedding in HCEC was stimulated by adding phorbol myristate acetate (PMA, 3 μM: ) both with and without ectodomain shedding inhibition using TNF-α processing inhibitor-1 (TAPI-1, 250 ng/mL), and the concentration of sIL-6R in the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). Expression of differential sIL-6R mRNA splicing (DS-sIL-6R) in HCEC was examined by using reverse transcription (RT)-PCR. The recombinant IL-6 or combination of recombinant IL-6/sIL-6R was added to HCF culture medium and phosphorylation of STAT3 was analyzed by Luminex assay. Tear fluid from patients with Sjögren syndrome was collected and analyzed by ELISA for sIL-6R concentration.

RESULTS

In HCEC culture medium, sIL-6R release was increased significantly (P < 0.01) by adding PMA and this increased release of sIL-6R was inhibited significantly by adding TAPI-1, indicating the participation of ectodomain shedding in sIL-6R production. In RT-PCR, DS-sIL-6R expression was noted in HCEC. IL-6/sIL-6R-induced STAT3 phosphorylation was recognized in cultured HCF, suggesting IL-6 trans-signaling induced inflammatory cellular signaling in HCF. In the tear fluid of the patients with Sjögren syndrome, sIL-6R expression was up-regulated (Sjögren syndrome; 2.38 ± 0.98 ng/mL, normal control; 0.16 ± 0.34 ng/mL).

CONCLUSIONS

Production of sIL-6R was induced by both ectodomain shedding and mRNA splicing in the corneal epithelium. IL-6 trans-signaling can induce an inflammatory response in corneal fibroblasts. The up-regulation of sIL-6R in inflamed ocular surfaces suggests a pivotal role of sIL-6R at the ocular surface.

Inhibitory effects of UV-based therapy on dry skin-inducible nerve growth in acetone-treated mice

BACKGROUND

UV-based therapy has anti-pruritic effects in inflammatory skin diseases, such as atopic dermatitis and psoriasis. These anti-pruritic effects may be partly due to inhibition of intraepidermal nerve growth, but they have not been fully characterized.

OBJECTIVE

This study was performed to characterize the anti-nerve growth effects of UV-based therapies in acetone-treated mice as an acute dry skin model.

METHODS

Nerve fibers penetrate into the epidermis 24h after acetone treatment in mice, and nerve growth peaks 48h after acetone treatment. To investigate the effects of UV-based therapies on the epidermal nerve fibers, including combination treatment with corticosteroid ointment, the mice were treated with psoralen ultraviolet A (PUVA), PUVA and betamethasone valerate ointment (PUVA+BV), narrowband ultraviolet B (NB-UVB), or an excimer lamp. Each therapy was provided 24h after acetone treatment, and skin samples were taken 48h later. Nerve fiber densities and expression levels of nerve growth factor (NGF) and semaphorin 3A (Sema3A) in the epidermis were examined by immunohistochemistry.

RESULTS

Penetration of nerve fibers into the epidermis was observed in the acetone-treated mice, concomitant with increased NGF and decreased Sema3A levels in the epidermis. The acetone-induced intraepidermal nerve growth was significantly decreased by PUVA, PUVA+BV, NB-UVB, and excimer lamp treatments compared with controls. In addition, PUVA+BV and NB-UVB normalized the abnormal expression of NGF and Sema3A in the epidermis, but no such normalization was observed with excimer lamp treatment.

CONCLUSION

UV-based therapies, especially NB-UVB and excimer lamp treatments, may be effective therapeutic methods for pruritus involving epidermal hyperinnervation.

Genome wide screen identifies microsatellite markers associated with acute adverse effects following radiotherapy in cancer patients

Background

The response of normal tissues in cancer patients undergoing radiotherapy varies, possibly due to genetic differences underlying variation in radiosensitivity.

Methods

Cancer patients (n = 360) were selected retrospectively from the RadGenomics project. Adverse effects within 3 months of radiotherapy completion were graded using the National Cancer Institute Common Toxicity Criteria; high grade group were grade 3 or more (n = 180), low grade group were grade 1 or less (n = 180). Pooled genomic DNA (gDNA) (n = 90 from each group) was screened using 23,244 microsatellites. Markers with different inter-group frequencies (Fisher exact test P < 0.05) were analyzed using the remaining pooled gDNA. Silencing RNA treatment was performed in cultured normal human skin fibroblasts.

Results

Forty-seven markers had positive association values; including one in the SEMA3A promoter region (P = 1.24 × 10^-5). SEMA3A knockdown enhanced radiation resistance.

Conclusions

This study identified 47 putative radiosensitivity markers, and suggested a role for SEMA3A in radiosensitivity.

Effects of semaphorin 3A overexpression in corneal fibroblasts on the expression of adherens-junction proteins in corneal epithelial cells

Interactions between epithelial cells and fibroblasts play important roles in tissue homeostasis. Semaphorins are a family of glycoproteins that contribute to axon guidance during development. With the use of a coculture system in which human corneal fibroblasts and epithelial cells are cultured on opposite sides of a collagen membrane, we have examined the effects of overexpression of semaphorin 3A in corneal fibroblasts on the expression of junctional proteins in corneal epithelial cells. Reverse transcription-polymerase chain reaction as well as immunoblot and immunofluorescence analyses revealed that the overexpression of semaphorin 3A in corneal fibroblasts increased the expression of E-cadherin and N-cadherin in corneal epithelial cells at both the mRNA and protein levels. These effects of semaphorin 3A were dependent on the presence of extracellular Ca(2+). Our findings indicate that semaphorin 3A released from corneal fibroblasts may play an important role in the regulation of intercellular communication between corneal epithelial cells as well as in the maintenance of corneal structure and function.

Dynamic expression of axon guidance cues required for optic tract development is controlled by fibroblast growth factor signaling

Axons are guided to their targets by molecular cues expressed in their environment. How is the presence of these cues regulated? Although some evidence indicates that morphogens establish guidance cue expression as part of their role in patterning tissues, an important question is whether morphogens are then required to maintain guidance signals. We found that fibroblast growth factor (FGF) signaling sustains the expression of two guidance cues, semaphorin3A (xsema3A) and slit1 (xslit1), throughout the period of Xenopus optic tract development. With FGF receptor inhibition, xsema3A and xslit1 levels were rapidly diminished, and retinal ganglion cell axons arrested in the mid-diencephalon, before reaching their target. Importantly, direct downregulation of XSema3A and XSlit1 mostly phenocopied this axon guidance defect. Thus, FGFs promote continued presence of specific guidance cues critical for normal optic tract development, suggesting a second later role for morphogens, independent of tissue patterning, in maintaining select cues by acting to regulate their transcription.

IGF-1 released by corneal epithelial cells induces up-regulation of N-cadherin in corneal fibroblasts

Interactions between epithelial cells and fibroblasts play important roles in tissue homeostasis. With the use of a coculture system in which human corneal fibroblasts and epithelial cells are cultured on opposite sides of a collagen (vitrigel) membrane, we have examined the effects of epithelial cells on expression of the adherens-junction protein N-cadherin in fibroblasts. Reverse transcription-polymerase chain reaction and immunoblot analyses showed that the presence of epithelial cells increased the expression of N-cadherin in fibroblasts at the mRNA and protein levels. This effect of epithelial cells was mimicked by insulin-like growth factor-1 (IGF-1) but not by epidermal growth factor or fibroblast growth factor. Depletion of IGF-1 in epithelial cells by RNA interference abolished the effect of these cells on N-cadherin expression in fibroblasts. The presence of epithelial cells activated the IGF-1 receptor as well as up-regulated expression of the transcriptional regulator ZEB1 in fibroblasts. RNA interference-mediated depletion of IGF-1 in epithelial cells prevented the effect of these cells on ZEB1 expression in fibroblasts. These results suggest that IGF-1 released from corneal epithelial cells up-regulates the expression of N-cadherin in corneal fibroblasts.