Alteration of expression pattern of transient receptor potential vanilloid 2 and transient receptor potential vanilloid 3 in ocular surface neoplasm.

PURPOSE: We determined if the immunohistochemical expression pattern of transient receptor potential vanilloid (TRPV) family members and TRP ankyrin 1 (TRPA1) differs among a healthy conjunctival epithelium and diseased epithelia. MATERIALS AND METHODS: Subjects include a normal conjunctival epithelium, pterygium epithelium, epithelial dysplasia or carcinoma in situ. RESULTS: TRPV1, TRPV4 or TRPA1 was detected in both the cytoplasm and nuclei, or in either the nuclei or cytoplasm, of these different epithelial layers, respectively. There was no difference in the expression pattern of these three TRP isoforms. On the other hand, the expression patterns of TRPV2 and TRPV3 differed dramatically among these different subjects. TRPV2 was observed in the basal layer epithelium of a normal conjunctiva and pterygium. Its pattern was scattered in this region, although TRPV2 was absent throughout most of the dysplastic epithelium. TRPV2 was detected only in some of the suprabasal epithelial cells of a carcinoma in situ. TRPV3 was faintly detected in the cytoplasm of all the cell layers and also in the nuclei of some of the basal cells in a normal conjunctiva and in the pterygia epithelium, while in situ it was uniformly expressed in all of the dysplasia and carcinoma nuclei in all epithelial cell layers. CONCLUSION: These results suggest that TRPV2 and TRPV3 expression pattern analysis might be potential diagnostic markers of ocular surface epithelial disorders.

A Case of Solitary Nonvascularized Corneal Epithelial Dysplasia.

Background. Epithelial dysplasia is categorized as conjunctival/corneal intraepithelial neoplasia which is a precancerous lesion. The lesion is usually developed at the limbal region and grows towards central cornea in association with neovascularization into the lesion. Here, we report a case of isolated nonvascularized corneal epithelial dysplasia surrounded by normal corneal epithelium with immune histochemical finding of ocular surface tissues cytokeratins, for example, keratin 13 and keratin 12. Case Presentation. A 76-year-old man consulted us for visual disturbance with localized opacification of the corneal epithelium in his left eye. His visual acuity was 20/20 and 20/200 in his right and left eye, respectively. Slit lamp examination showed a whitish plaque-like lesion at the center of his left corneal epithelium. No vascular invasion to the lesion was found. The lesion was surgically removed and subjected to histopathological examination and diagnosed as epithelial dysplasia. Amyloidosis was excluded by direct fast scarlet 4BS (DFS) staining. Immunohistochemistry showed that the dysplastic epithelial cells express keratin 13 and vimentin, but not keratin 12, indicating that the neoplastic epithelial cells lacked corneal-type epithelium differentiation. Conclusions. The lesion was diagnosed as nonvascularized epithelial dysplasia of ocular surface. Etiology of the lesion is not known.

Wakayama symposium: modulation of wound healing response in the corneal stroma by osteopontin and tenascin-C.

The extracellular matrix components osteopontin and tenascin-C are ligands of α9 integrin, and both play roles in corneal wound fibrosis and neovascularization. It has been shown that loss of osteopontin impairs closure of incisional wounds in the mouse cornea. Detailed analyses suggest that the loss of osteopontin reduces macrophage invasion and myofibroblast differentiation in the healing stroma in association with suppression of fibrogenic gene expression in response to injury. Cultured ocular fibroblasts derived from knockout mice showed an impairment of activation of p38 MAPK and Smad3 upon exposure to transforming growth factor ß1. The loss of tenascin-C delays stromal healing in association with suppression of fibrogenic gene expression and macrophage invasion. With regard to neovascularization, the loss of either osteopontin or tenascin-C suppressed the growth of new blood vessels from the limbal region toward the central cornea in response to corneal cauterization in mice. Gene expression analysis further showed that lack of osteopontin or tenascin-C resulted in inhibition of angiogenic and proinflammatory gene expression. In conclusion, osteopontin or tenascin-C, α9 integrin ligands, play an important role in stromal healing (or fibrosis) and neovascularization in mouse cornea.

Impaired cornea wound healing in a tenascin C-deficient mouse model.

We investigated the effects of loss of tenascin C on the healing of the stroma using incision-injured mice corneas. Tenascin C was upregulated in the stroma following incision injury to the cornea. Wild-type (WT) and tenascin C-null (knockout (KO)) mice on a C57BL/6 background were used. Cell culture experiments were also conducted to determine the effects of the lack of tenascin C on fibrogenic gene expression in ocular fibroblasts. Histology, immunohistochemistry and real-time reverse transcription PCR were employed to evaluate the healing process in the stroma. The difference in the incidence of wound closure was statistically analyzed in hematoxylin and eosin-stained samples between WT and KO mice in addition to qualitative observation. Healing of incision injury in corneal stroma was delayed, with less appearance of myofibroblasts, less invasion of macrophages and reduction in expression of collagen Iα1, fibronectin and transforming growth factor ß1 (TGFß1) in KO mice compared with WT mice. In vitro experiments showed that the loss of tenascin C counteracted TGFß1 acceleration of mRNA expression of TGFß1, and of collagen Iα1 and of myofibroblast conversion in ocular fibroblasts. These results indicate that tenascin C modulates wound healing-related fibrogenic gene expression in ocular fibroblasts and is required for primary healing of the corneal stroma.

TRPV1 involvement in inflammatory tissue fibrosis in mice.

We examined whether absence or blocking of transient receptor potential vanilloid subtype 1 (TRPV1) affects the level of inflammation and fibrosis/scarring during healing of injured tissue using an alkali burn model of cornea in mice. A cornea burn was produced with 1 N NaOH instilled into one eye of TRPV1-/- (KO) (n = 88) or TRPV1+/+ (n = 94) mice. Examinations of the corneal surface and eye globe size suggested that the loss of TRPV1 suppressed inflammation and fibrosis/scarring after alkali burn, and this was confirmed by histology, IHC, and gene expression analysis. The loss of TRPV1 inhibited inflammatory cell invasion and myofibroblast generation in association with reduction of expression of proinflammatory and profibrogenic components. Experiments of bone marrow transplantation between either genotype of mice showed that KO corneal tissue resident cells, but not KO bone marrow-derived cells, are responsible for KO-type wound healing with reduced inflammation and fibrosis. The absence of TRPV1 attenuated expression of transforming growth factor ß 1 (TGFß1) and other proinflammatory gene expression in cultured ocular fibroblasts, but did not affect TGFß1 expression in macrophages. Loss of TRPV1 inhibited myofibroblast transdifferentiation in cultured fibroblasts. Systemic TRPV1 antagonists reproduced the KO type of healing. In conclusion, absence or blocking of TRPV1 suppressed inflammation and fibrosis/scarring during healing of alkali-burned mouse cornea. TRPV1 is a potential drug target for improving the outcome of inflammatory/fibrogenic wound healing.

Two cases of congenital retrobulbar cyst or peripapillary staphyloma with an alcoholic mother.

The authors report two cases of congenital retrobulbar cyst or large peripapillary staphyloma with alcoholic mothers. In the first case, a 53-day-old newborn was referred for evaluation of microphthalmia in her left eye. Ophthalmic examination showed microcornea, microphthalmia, and an abnormally enlarged optic disc with an excavation in her left eye. Imaging revealed the presence of a cystic lesion in her left orbit that seemed to be communicated with the vitreous cavity. She did not have chromosomal abnormality. In the second case, a large peripapillary staphyloma was detected in the right eye of a 7-month-old newborn. The mother of each patient was an alcoholic. Retrobulbar cystic lesion or peripapillary staphyloma could be considered to be a series of abnormalities caused by the degree of the failure of the optic cup. Effects of each mother's alcohol intake on the development of the eye, especially the closure of the optic cup, is to be further investigated.

Impaired angiogenic response in the cornea of mice lacking tenascin C.

PURPOSE: This study investigated the effects of loss of tenascin C (TNC) in the development of neovascularization in a corneal stroma in mice. Cell culture study was also conducted to clarify the roles of TNC in the expression of vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)ß1 in fibroblasts and macrophages. METHODS: Ocular fibroblasts and macrophages from wild-type (WT) and TNC-null (KO) mice were used to study the role of TNC in the expression of VEGF and TGFß1. The effects of the absence of TNC on angiogenic gene expression, inflammatory cell invasion, and cornea neovascularization in the corneal stroma were then evaluated after cauterization of the center of the cornea in mice. Histologic, immunohistochemical, and mRNA expression analyses were performed. RESULTS: Absence of TNC suppressed expression of VEGF and counteracted upregulation of TGFß1 by exogenous TGFß1 in ocular fibroblast culture. Such effects of the absence of TNC were not observed in cultured macrophages. Absence of TNC attenuated expression of both VEGF and TGFß1 mRNA as well as neovascularization into the stroma after cauterization at the center of the cornea in mice. Absence of TNC suppressed macrophages, but not neutrophils, invading the cauterized cornea. CONCLUSIONS: TNC is involved in angiogenic gene expression in ocular fibroblasts in vitro and in vivo and is required for macrophage invasion and neovascularization of injured corneal stroma.

Transforming growth factor beta signal transduction: a potential target for maintenance/restoration of transparency of the cornea.

Maintenance of the transparency and regular shape of the cornea are essential to the normal vision, whereas opacification of the tissue impairs vision. Fibrogenic reaction leading to scarring in an injured cornea is characterized by appearance of myofibroblasts, the key player of the fibrogenic reaction, and excess accumulation of fibrous extracellular matrix. Inflammatory/fibrogenic growth factors/cytokines produced by inflammatory cells play a pivotal role in fibrogenic response. Signaling systems involved in myofibroblast formation and fibrogenesis are activated by various growth factors, i.e., transforming growth factor beta or others. Modulation of transforming growth factor beta signal transduction molecules, e.g., Smad and mitogen-activated protein kinases, by gene transfer and other technology provides a new concept of prevention/treatment of unfavorable fibrogenesis in the cornea.

Suppression of injury-induced epithelial-mesenchymal transition in a mouse lens epithelium lacking tenascin-C.

PURPOSE: To investigate the role of tenascin-C in epithelial-mesenchymal transition (EMT) of the lens epithelium during wound healing in mice. Tenascin-C is a component of the extracellular matrix in patients having post-operative capsular opacification. METHODS: The crystalline lens was injured by needle puncture in tenascin-C null (KO, n=56) and wild-type (WT, n=56) mice in a C57BL/6 background. The animals were killed at day 2, 5, or 10 post-injury. Immunohistochemistry was employed to detect alpha-smooth muscle actin (alphaSMA), a marker of EMT, collagen type I, transforming growth factor beta1 (TGFbeta1), phospho-Smad2, phospho-adducin, and phospho-myosin light chain 9 (MLC9). The expression levels of phospho-adducin and phospho-MLC9 were used as markers for the activation of protein kinase C and Rho kinase, respectively. RESULTS: The expression of tenascin-C was upregulated in WT lens epithelial cells adjacent to the capsular break at day 5. The results showed that injury-induced EMT of the mouse lens epithelium, as evaluated by histology and the expression patterns of alphaSMA and fibronectin, was attenuated in the absence of tenascin-C. Upregulation of TGFbeta1 expression in the epithelium was also inhibited, and loss of tenascin-C attenuated the phosphorylation of Smad2 and adducin in epithelial cells adjacent to the capsular break. The expression of phospho-adducin was suppressed, while the expression level of phospho-MLC9 was unchanged, in the healing epithelium in the absence of tenascin C. CONCLUSIONS: Tenascin-C is required for injury-induced EMT in the mouse lens epithelium. The mechanism behind this might involve impaired activation of cytoplasmic signaling cascades; i.e., TGFbeta/Smad and protein kinase C-adducing signaling, in the absence of tenascin-C.

Neurotrophic keratopathy; its pathophysiology and treatment.

Neurotropic keratopathy is one of the major refractory corneal disorders, which was first recognized in 1824. This category of diseases is caused by damage to the trigeminal nerve and the consequent loss of corneal sensation. It leads to various types of corneal disorder, including superficial keratopathy, persistent epithelial defects and corneal ulcers. In the present article, we review the pathobiology and prevention/treatment of neurotrophic corneal diseases. The goals of treatment of neurotrophic keratopathy are to prevent the progression of corneal damage to promote epithelial healing in case that the original damage in the trigeminal nerve or its braches is difficult. The therapy should be prompt and based on the clinical stage of the disease. Although at present, there are no accurate treatment methods for neurotrophic keratopathy, several effective treatments have been reported. Signals derived from TRP channels are involved in homeostasis of tissues by controlling cell behaviors, i. e., gene expression for inflammation, cell migration, or cell survival/cell death. Targeting TRP channel in the cornea is expected to contribute to the development of a new treatment method for neurotrophic keratopathy. Further study and clinical trial are need to establish this new treatment strategy.

Therapeutic potential of trichostatin A to control inflammatory and fibrogenic disorders of the ocular surface.

PURPOSE: To examine the effects of a histone deacetylase inhibitor, Trichostatin A (TSA), on the behavior of macrophages and subconjunctival fibroblasts in vitro and on ocular surface inflammation and scarring in vivo using an alkali burn wound healing model. METHODS: Effects of TSA on expression of inflammation-related growth factors or collagen I were examined by real-time RT-PCR or immunoassay in mouse macrophages or human subconjunctival fibroblasts. Effects of TSA on trans forming growth factor ß (TGFß)/Smad signaling were evaluated with western blotting and/or immunocytochemistry. Alkali-burn injuries on the eyes of mice were performed with three µl of 0.5 N NaOH under general and topical anesthesia. TSA (600 µg/Kg daily) or vehicle was administered to animals via intraperitoneal (i.p.) injection. Histology and real-time RT-PCR investigations evaluated the effects of TSA on the healing process of the cornea. RESULTS: TSA inhibited TGFß 1 and vascular endothelial growth factor (VEGF) expression in macrophages, and TGFß1 and collagen I in ocular fibroblasts. It elevated the expression of 5'-TG-3'-interacting factor (TGIF) and Smad7 in fibroblasts and blocked nuclear translocation of phospho-Smad2. Real-time PCR and immunocytochemistry studies showed that systemic administration of TSA suppressed the inflammation and fibrotic response in the stroma and accelerated epithelial healing in the alkali-burned mouse cornea. CONCLUSIONS: Systemic administration of TSA reduces inflammatory and fibrotic responses in the alkali-burned mouse ocular surface in vivo. The mechanisms of action involve attenuation of Smad signal in mesenchymal cells and reduction in the activation and recruitment of macrophages. TSA has the potential to treat corneal scarring in vivo.

Impaired angiogenic response in the corneas of mice lacking osteopontin.

PURPOSE: To investigate the effects of loss of osteopontin (OPN) in the development of neovascularization in corneal stroma in mice. Cell culture study was also conducted to clarify the effects of OPN in transforming growth factor (TGF) beta1-driven cell signaling and expression of vascular endothelial growth factor (VEGF). METHODS: Ocular fibroblasts from wild-type and OPN-null mice were used to study the role of OPN in TGFbeta1 signal and VEGF expression. The effect of the absence of OPN on corneal neovascularization was evaluated in mice. RESULTS: In ocular fibroblast culture, loss of OPN attenuated TGFbeta1 signals (Smad3 and p38) and reduced expression of VEGF. Loss of OPN attenuated neovascularization in corneal stroma in mice. CONCLUSIONS: OPN is involved in VEGF expression in cultured fibroblasts and is required for neovascularization in corneal stroma in vivo.

JNK MAPK signaling contributes in vivo to injury-induced corneal epithelial migration.

PURPOSE: Injury-mediated corneal epithelial wound healing in vivo is mediated through different cell signaling pathways depending on whether or not the basement membrane is removed. Given this dependence, we ascertained if c-jun N-terminal kinase (JNK/SAPK) mitogen-activated protein kinase (MAPK) cell signaling mediates this response in vivo and in vitro, irrespective of the presence or absence of the basement membrane. Furthermore, in vitro the relative contribution was determined by the JNK/SAPK pathway to that of its p38 and ERK MAPK counterparts in mediating injury-induced increases in cell migration. METHODS: Corneal epithelial debridement was performed in C57BL/6 mice and their organ-cultured eyes without removal of the basement membrane. In rabbits, following basement membrane removal by keratectomy, fluorescein-staining monitored reepithelialization was performed as in the mice. Immunohistochemistry evaluated changes in JNK phosphorylation status and localization. JNK inhibitor I and its inactive analogue determined if JNK signaling activation contributes to wound healing. BrdU staining assessed cell proliferation. A scratch wound assay of healing rates in SV40-immortalized human corneal epithelial cell line (HCEC) evaluated the relative contributions by p38 and ERK and JNK MAPK signaling activation to wound healing. A TUNEL assay probed for apoptosis after wound closure of HCEC. MTT assay evaluated corneal epithelial viability. RESULTS: Two hours following mice corneal epithelial debridement, phospho-JNK was transiently upregulated in the nucleus, whereas total JNK was constitutively expressed. JNK inhibitor I suppressed epithelial spreading in organ-cultured mouse eyes and rabbit corneal blocks, irrespective of the presence or absence of basement membrane. No proliferation was detected at the wound edges. In HCEC, a p38 (SB203580) and a JNK pathway inhibitor (JNK inhibitor I) inhibited migration rates more than U0126-induced ERK, whereas the JNK inhibitor I inactive analogue had no effect. JNK pathway inhibition wound closure in this region was not associated with either any TUNEL or BrdU-positive cells. Cell viability was unaffected by any of these MAPK inhibitors. CONCLUSION: JNK/SAPK pathway activation stimulates wound healing in vitro and in vivo, irrespective of the presence or absence of the basement membrane. Therefore, studies on how wound closure is elicited in HCEC are relevant for identifying how MAPK signaling mediates this response in vivo and in organ-cultured eyes. This realization suggests that the JNK signaling system has a role in vivo that is intermediate to those of ERK and p38 in mediating increases in cell migration.

TGF beta in fibroproliferative diseases in the eye.

Transforming growth factor b (TGF beta) is believed to be the most important ligand in the pathogenesis of fibrotic diseases in the eye. Such ocular fibrotic diseases include scarring in the cornea and conjunctiva, fibrosis in the corneal endothelium, post-cataract surgery fibrosis of the lens capsule, excess scarring the tissue around the extraocular muscles in the strabismus surgery and proliferative vitreoretinopathy. In the proliferative stage of diabetic retinopathy, fibrogenic reaction causes tractional retinal detachment in association with contraction of the tissue. A myofibroblast, the major cellular component in the fibrotic lesions, is derived from both mesenchymal cells (in cornea and conjunctiva) and epithelial cell types (lens or retinal pigment epithelium or corneal endothelium) through epithelial-mesenchymal transition (EMT). The myofibroblasts cause excess accumulation of fibrogenic extracellular matrix with resultant tissue contraction and impaired functions. Although various cytokine signaling pathways are involved in the fibrogenic reaction in tissues, TGF beta/Smad signal is the critical one. Blocking Smad signal by chemical or natural inhibitors or anti-Smad gene introduction effectively suppress fibrogenic reaction; inhibition of both fibroblast-myofibroblast conversion or EMT. Such strategies can be clinically tested.

Impaired cutaneous wound healing with excess granulation tissue formation in TNFalpha-null mice.

We examined the effects of lacking tumor necrosis factor alpha (TNFalpha) on the healing process of a cutaneous wound in mice using TNFalpha-deficient mice. A full-thickness circular cutaneous wound 5.0 mm in diameter was produced in the dorsal skin of wild-type (WT) or TNFalpha-null (KO) mice. After specific intervals of healing, the healing pattern was evaluated by macroscopic observation, histology, immunohistochemistry, or real-time reverse transcription-polymerase chain reaction. Effect of Smad7 gene transfer on the healing phenotype of KO mice was also examined. The results showed that loss of TNFalpha promotes granulation tissue formation and retards reepithelialization in a circular wound in mouse dorsal skin. Immunohistochemistry showed that distribution of macrophages and myofibroblasts in newly generated granulation tissue seemed similar between WT and KO mice. However, lacking TNFalpha enhanced mRNA expression of TGFbeta1 and collagen Ialpha2 in such tissue. Smad7 gene transfer counteracted excess granulation tissue formation in KO mice. In conclusion, lacking TNFalpha potentiates Smad-mediated fibrogenic reaction in healing dermis and retards reepithelialization in a healing mouse cutaneous wound.

Suppression of injury-induced conjunctiva scarring by peroxisome proliferator-activated receptor gamma gene transfer in mice.

PURPOSE: To examine the effects of introduction of the adenoviral peroxisome proliferator-activated receptor (PPAR)-gamma gene on postinjury conjunctival scarring in mice. Its effects on fibrogenic reaction of cultured human subconjunctival fibroblasts (hSCFs) were also evaluated. METHODS: The effects of PPARgamma gene introduction on expression of type I collagen, fibronectin, and connective tissue growth factor (CTGF) in hSCFs were examined. A circumferential incision was made in the equatorial conjunctiva of the right eye of generally anesthetized adult C57BL/6 mice (n = 72). PPARgamma cDNA-expressing adenoviral vector was topically applied; the control eye received nonfunctioning adenoviral vector. At 2, 5, 7, and 14 days (each, n = 18), the eyes were processed for histologic or immunohistochemical examination to evaluate tissue scarring. Expression of type I collagen and growth factors was evaluated by real-time reverse transcription-polymerase chain reaction in 32 eyes from control and treatment groups. RESULTS: PPARgamma overexpression suppressed type I collagen, fibronectin, and CTGF in cultured hSCFs at the mRNA or protein level. In vivo experiments showed that PPARgamma gene introduction suppressed monocyte/macrophage invasion, generation of myofibroblasts, and mRNA upregulation of cytokines/growth factors and collagen Ialpha2 chain (Col 1A2) in healing conjunctiva. CONCLUSIONS: PPARgamma gene transfer suppresses the fibrogenic reaction in hSCFs as well as the injury-induced scarring of conjunctival tissue in mice, suggesting the effectiveness of this strategy in preventing excess scarring after filtration surgery. The mechanism may include suppression of activation of fibroblasts and reduction of macrophage invasion.

Inhibitory effect of blocking TGF-beta/Smad signal on injury-induced fibrosis of corneal endothelium.

PURPOSE: To understand the role of TGF-beta related signals in the repair of a corneal endothelium defect and also to evaluate the therapeutic effect of Smad7 gene transfer on injury induced fibrosis of the corneal endothelium in rats. METHODS: (1) Japanese albino rabbits (n=108) were used. Blocks of central cornea (4 x 4 mm) were prepared. After partially scraping the endothelium to produce a defect, the blocks were organ cultured for 24 h in the presence of either exogenous growth factors, transforming growth factor beta (TGF-beta)-neutralizing antibody, or inhibitors of each TGF-beta related signal. Endothelium repair was assayed under light microscopy. (2) Adult Wistar rats (n=62) were then used. Smad7 expressing adenoviral vector (Smad7-Ad) or non-functioning control vector (Cre-Ad) was administered to the anterior chamber of an eye. The cornea was burned with topical 1 N NaOH (10 microl) three days later. After specific intervals, the eye was histologically observed. RESULTS: (1) The endothelial layer that elongated toward the defect lacked proliferation after 24 h in organ culture. Endogenous TGF-beta was required for endothelium defect repair. Inhibition of p38 and Erk but not c-Jun NH(2)-terminal kinase (JNK) and ALK5 signal (Smad) retarded such cell spreading. (2) Adenoviral Smad7 overexpression suppressed fibrogenic reaction of the endothelium of an alkali-burned cornea as evaluated by immunohistochemistry for phospho-Smad2, collagen I, and alpha-smooth muscle actin, a marker for endothelial-mesenchymal transition (EnMT), and by electron microscopy. CONCLUSIONS: Inhibition of Smad and JNK signals do not affect corneal endothelium defect repair. Inhibition of Smad suppresses fibrogenic reaction via EnMT of corneal endothelium in vivo.

Tetrandrine suppresses activation of human subconjunctival fibroblasts in vitro.

PURPOSE: To investigate the effect of tetrandrine on activation of human subconjunctival fibroblasts (SCFs) in vitro. METHODS: Effects of tetrandrine on proliferation, matrix expression, myofibroblast generation, and cell migration of SCF were examined in SCF cultures. Tetrandrine effect on TGFbeta 1/Smad2 signal and Smad7 expression was examined. Migration was evaluated by in vitro defect closure in a monolayer cell culture. Western blotting and immunocytochemistry were used. RESULTS: Tetrandrine suppressed wound-induced cell migration (defect closure) and myofibroblast generation, but not cell proliferation in SCF cultures. It also decreased expression of fibronectin, collagen I, and alpha SMA. Adding tetrandrine increased protein level of Smad7 and suppressed Smad2 signal. CONCLUSION: Tetrandrine suppresses Smad2 signal and fibrogenic responses in SCFs in association with Smad7 up-regulation, suggesting its potential therapeutic value to prevent excess scarring/fibrosis in conjunctiva following trabeculectomy or in patients with severe conjunctival inflammation.

Corneal wound healing in an osteopontin-deficient mouse.

PURPOSE: To investigate the effects of loss of osteopontin (OPN) in the healing of the injured cornea in mice. Cell culture study was also conducted to clarify the effects of OPN in fibroblast behaviors. METHODS: Ocular fibroblasts from wild-type (WT) and OPN-null (KO) mice were used to study the role of OPN on cell behavior. The effect of the lack of OPN on corneal wound healing was evaluated in mice. RESULTS: In cell culture, OPN is involved in cell adhesion and in the migration of ocular fibroblasts. Adhesion of the corneal epithelial cell line was not affected by exogenous OPN. OPN was upregulated in a healing, injured mouse cornea. Loss of OPN did not affect epithelial healing after simple epithelial debridement. Healing of an incision injury in cornea was delayed, with less appearance of myofibroblasts and transforming growth factor beta1 expression in a KO mouse than in a WT mouse. The absence of OPN promoted tissue destruction after an alkali burn, resulting in a higher incidence of corneal perforation in KO mice than in WT mice. CONCLUSIONS: OPN modulates wound healing-related fibroblast behavior and is required to restore the physiological structure of the cornea after wound healing.

Epithelial-mesenchymal transition as a therapeutic target for prevention of ocular tissue fibrosis.

Fibrotic diseases are characterized by the appearance of myofibroblasts, the key cell type involved in the fibrogenic reaction, and by excess accumulation of extracellular matrix with resultant tissue contraction and impaired function. Myofiborblasts are generated by fibroblast-myofibrobalst conversion, and in certain tissues through epithelial-mesenchymal transition (EMT), a process through which an epithelial cell changes its phenotype to become more like a mesenchymal cell. Although inflammatory/fibrogenic growth factors/cytokines produced by injured tissues orchestrate the process of EMT, transforming growth factor beta (TGFbeta) is believed to play a central role in the process. Unlike fibrotic lesions in kidney or other tissues where myofibroblasts are generated from both fibroblasts and epithelial cells, fibrotic lesions in the eye crystalline lens are derived only from lens epithelial cells without contamination of fibroblast-derived myofibroblasts. Thus, this tissue is suitable to investigate detailed mechanisms of EMT and subsequent tissue fibrosis. EMT in retinal pigment epithelium is involved in the development of another ocular fibrotic disease, proliferative vitreoretinopathy, a fibrosis in the retina. EMT-related signal transduction cascades, i. e., TGFbeta/Smad, are a target to prevent or treat unfavorable ocular tissue fibrosis, e. g., fibrotic diseases in the crystalline lens or retina, as well as possibly in other organs.