SMAD4-Dependent Signaling Pathway Involves in the Pathogenesis of TGFBR2-Related CE-like Phenotype.

(1) Background: Our previous data indicated that disturbance of the Transforming Growth Factor beta (TGFB) signaling pathway via its Type-2 Receptor (TGFBR2) can cause a Corneal Ectasia (CE)-like phenotype. The purpose of this study is to elucidate whether the SMAD4-dependent signaling pathway is involved in the TGFBR2-related CE-like pathogenesis. (2) Methods: Smad4 was designed to be conditionally knocked out from keratocytes. Novel triple transgenic mice, KerartTA; Tet-O-Cre; Smad4flox/flox (Smad4kera-cko), were administered with doxycycline (Dox). Optical Coherence Tomography (OCT) was performed to examine Central Corneal Thickness (CCT), Corneal Radius, Anterior Chamber and CE-like phenotype and compared to the littermate Control group (Smad4Ctrl). (3) Results: The OCT revealed normal cornea in the Smad4Ctrl and a CE-like phenotype in the Smad4kera-cko cornea, in which the overall CCT in Smad4kera-cko was thinner than that of Smad4Ctrl at P42 (n = 6, p < 0.0001) and showed no significant difference when compared to that in Tgfbr2kera-cko. Furthermore, the measurements of the Anterior Chamber and Corneal Radius indicated a substantial ectatic cornea in the Smad4kera-cko compared to Smad4Ctrl. The H&E staining of Smad4kera-cko mimics the finding in the Tgfbr2kera-cko. The positive immunostaining of cornea-specific marker K12 indicating the cell fate of cornea epithelium remained unchanged in Smad4kera-cko and the Proliferating Cell Nuclear Antigen (PCNA) immunostaining further indicated an enhanced proliferation in the Smad4kera-cko. Both immunostainings recapitulated the finding in Tgfbr2kera-cko. The Masson's Trichrome staining revealed decreased collagen formation in the corneal stroma from both Smad4kera-cko and Tgfbr2kera-cko. The collagen type 1 (Col1a1) immunostaining further confirmed the reduction in collagen type 1 formation in Smad4kera-cko. (4) Conclusions: The aforementioned phenotypes in the Smad4kera-cko strain indicated that the SMAD4-dependent signaling pathway is involved in the pathogenesis of the CE-like phenotype observed in Tgfbr2kera-cko.

Impaired healing in an incision wound in corneal stroma in a lumican-null mouse.

PURPOSE: We investigated healing pattern of an incisional wound in corneal stroma of lumican-null (KO) mice. METHODS: C57BL/6 mice (wild-type, WT) and lumican-null (knockout, KO) mice were used. A linear full-thickness incision was produced in one cornea of each mouse. After intervals of healing, the corneas were processed for the following analyses. Histology was employed to measure the distance between each edge of the disrupted Descemet's membrane at the center of the cornea. Immunohistochemistry and real-time RT-PCR were employed to evaluate the expression of wound healing-related components in the tissue. Cultured ocular fibroblasts were obtained from cornea and sclera of WT and KO postnatal day 1 pups. The cells were subjected to examination for cell proliferation and expression of wound healing-related gene products. In vitro gel contraction assay was used to asses cell contractile activity of WT and KO cells. RESULTS: At day 5 of incision, the distance between the disrupted Descemet's membrane was larger in a KO mouse as compared with a WT mouse. Myofibroblast appearance in the wound was suppressed by the loss of lumican. The loss of lumican downregulated TGFß1's effects on mRNA expression of α-smooth muscle actin and collagen Ia1 in cultured ocular fibroblasts. Cell proliferation rate increased in injured stroma, which was further supported by in vitro datum of cell proliferation augmentation by the loss of lumican. Loss of lumican suppressed cell-mediated gel contraction. CONCLUSION: Loss of lumican perturbs the healing of penetrating incision in mouse corneal stroma in association with suppression of myofibroblast generation.

Topical Spironolactone in the Treatment of Ocular Graft-Versus-Host Disease.

INTRODUCTION: This two-part study aimed to investigate the therapeutic potential of topical spironolactone in ocular graft-versus-host disease (oGVHD). While off-label use of topical spironolactone has been described in dry eye, its efficacy in managing signs and symptoms of oGVHD remains unstudied. Preclinically, we tested the hypothesis that spironolactone induces corneal lipid synthesis in a mouse model. Clinically, we assessed patient response to spironolactone with a retrospective observational design. METHODS: Both immortalized and primary human corneal epithelial cells were stained with oil red O after 9 days of treatment with spironolactone. C57BL/6 mice were dosed thrice daily with one drop in each eye for 18 days. Corneal tissue was stained with oil red O and BODIPY™. Twenty eyes with oGVHD, as defined by the International Chronic oGVHD Consensus Group, were studied. Corneal fluorescein staining, lid margin vascularity, meibomian gland obstruction, meibum turbidity, zone A posterior lid margin vascularity, and oGVHD diagnostic criteria severity grading were compared in a pre-post study. Follow-up times ranged from 7 to 21 weeks, with a median time of 12 weeks. Statistical analysis was done with STATA 17 by fitting data to a non-parametric model. RESULTS:  In vitro results showed an increased number and density of oil red O staining granules in the treatment group versus control in both primary and immortalized human corneal epithelium. In vivo, results showed translation to the mouse model with increased corneal epithelial BODIPY™ signal compared to untreated control. oGVHD patients had improved lid margin vascularity (p = 0.046), corneal fluorescein staining (p = 0.021), and International oGVHD Consensus Group severity scores (p = 0.011) after treatment with topical spironolactone. Minimal adverse effects were noted, the most common being mild stinging lasting less than a minute after instillation. CONCLUSION: The improved severity scores, lid margin inflammation, and corneal fluorescein staining after weeks of treatment support the rationale that topical spironolactone may benefit oGVHD. The observed lipid production by the corneal epithelium is thought to contribute to this protective effect against ocular surface erosive disease in oGVHD. A mineralocorticoid receptor antagonist, spironolactone may offer therapeutic benefits in oGVHD while avoiding undesirable side effects of topical or systemic glucocorticoids.

Transforming growth factor beta receptor 2 (Tgfbr2) deficiency in keratocytes results in corneal ectasia.

PURPOSE: We hypothesized that Transforming growth factor beta receptor 2 (Tgfbr2) deletion in keratocyte (Tgfbr2kera-cko), the corneal stroma cell, can result in corneal thinning and generate a potential model for Cornea Ectasia (CE). METHODS: Corneal thickness of Tgfbr2kera-cko and Tgfbr2Ctrl was examined with Optical Coherence Tomography (OCT) at post-natal (P) days 42 and 70, respectively. Histological H&E staining, transmission electron micrograph (TEM), and immunofluorescence staining (IFS) were harnessed to examine corneal cell morphology, proliferation, differentiation, and collagen fibrils. RESULTS: Slit-Lamp revealed that corneas were transparent in both Tgfbr2kera-cko and Tgfbr2Ctrl, however, Tgfbr2kera-cko cornea was 33.5% and 42.9% thinner as compared with those of Tgfbr2Ctrl at P42 and P70, respectively. H&E and semithin section staining with toluidine blue-O confirmed that Tgfbr2kera-cko cornea has a thinner stroma. In contrast, the epithelium in Tgfbr2kera-cko was substantially thicker. The cell proliferation marker Ki67 expression level increased ∼9% in Tgfbr2kera-cko corneal epithelium as compared with that in Tgfbr2Ctrl, however, the Krt14 and Krt12 expression pattern was not obviously changed in Tgfbr2kera-cko corneal epithelium. It was noticed that Col1a1 expression was substantially reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl. TEM showed that keratocytes were unhealthy and stromal collagen fibril density was significantly reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl cornea. Moreover, mechanical eye-rubbing on Tgfbr2kera-cko resulted in corneal hydrops and edema. CONCLUSION: Tgfbr2 in keratocytes is indispensable for the corneal stroma at postnatal homeostasis. The cornea phenotype manifested in these Tgfbr2kera-cko mice resembles corneal ectasia disease in humans.

Anomaly of cornea and ocular adnexa in spinster homolog 2 (Spns2) knockout mice.

Spinster 2 (Spns2) is a transporter that pumps sphingosine-1-phosphate (S1P), a bioactive lipid mediator synthesized in the cytoplasm, out of cells into the inter cellular space. S1P is a signal that modulates cellular behavior during embryonic development, inflammation and tissue repair, etc. A Spns2-null (KO) mouse is born with failure of eyelid closure (eyelid-open-at birth; EOB) and develop corneal fibrosis in adulthood. It remains elusive whether corneal lesion is caused by exposure to keratitis (lagophthalmos) of EOB phenotype or the loss of Spns2 directly perturbs the corneal tissue morphogenesis and intra-eyelid structures. Therefore, we investigated differences between the cornea and ocular adnexa morphogenesis in KO and wild-type (WT) embryos and adults as well. The loss of Spns2 perturbs cornea morphogenesis during embryonic development as early as E16.5 besides EOB phenotype. Histology showed that the corneal stroma was thinner with less extracellular matrix accumulation, e.g., collagen and keratocan in the KO mouse. Epithelial stratification, expression of keratin 12 and formation of desmosomes and hemidesmosomes were also perturbed in these KO corneas. Lacking Spns2 impaired morphogenesis of the Meibomian glands and of orbicularis oculi muscles. KO glands were labeled for ELOVL4 and PPARγ and were Oil-Red O-positive, suggesting KO acinar cells possessed functionality as the glands. This is the first report on the roles of Spns2 in corneal and Meibomian gland morphogenesis. Corneal tissue destruction in an adult KO mouse might be due to not only lagophthalmos but also to an impaired morphogenesis of cornea, Meibomian glands, and orbicularis oculi muscle.

Inducible Slc4a11 Knockout Triggers Corneal Edema Through Perturbation of Corneal Endothelial Pump.

Purpose: The conventional Slc4a11 knockout (KO) shows significant corneal edema at eye opening, a fact that complicates the study of the initial events leading to edema. An inducible KO would provide opportunities to examine early events following loss of Slc4a11 activity. Methods: Slc4a11 Flox (SF) mice were crossed with mice expressing the estrogen receptor Cre Recombinase fusion protein and fed tamoxifen (Tm) for two weeks. Corneal thickness (CT) was measured by OCT. At eight weeks endpoint, oxidative damage, tight junction integrity, stromal lactate concentration, endothelial permeability, differentially expressed transporters, and junction proteins were determined. Separately, a keratocyte only inducible Slc4a11 KO was also examined. Results: At four weeks post-Tm induction Slc4a11 transcript levels were 2% of control. Corneal thickness increased gradually and was 50% greater than Wild Type (WT) after eight weeks with significantly altered endothelial morphology, increased nitrotyrosine staining, significantly higher stromal lactate, decreased expression of lactate transporters and Na-K ATPase activity, higher ATP, altered expression of tight and adherens junctions, and increased fluorescein permeability. No significant differences in CT were found between WT and keratocyte only Slc4a11 KO. Conclusions: The Slc4a11 inducible KO shows development of a similar phenotype as the conventional KO, thereby validating the model and providing a tool for further use in examining the sequence of cellular events by use of noninvasive in vivo physiological probes.

Excess Transforming Growth Factor-α Changed the Cell Properties of Corneal Epithelium and Stroma.

Purpose: This study is to investigate the corneal anomaly caused by excess transforming growth factor-α (TGF-α) during mouse development. Methods: Bitransgenic KeraRT/TGF-α mice, generated via cross-mating tetO-TGF-α and KeraRT mice, were induced to overexpress TGF-α by doxycycline commencing at embryonic day 0 or postnatal day 0 to different developmental stages. Bitransgenic mice with doxycycline induction were defined as TGF-αECK mice (TGF-α excess expression by corneal keratocytes). Mouse eyes were examined by hematoxylin and eosin staining, immunofluorescent staining and transmission electron microscopy. Protein and RNA from mouse cornea were subjected to western blotting and real-time quantitative polymerase chain reaction. Results: In TGF-αECK mice, TGF-α overexpression resulted in corneal opacity. Excess TGF-α initially caused corneal epithelial hyperplasia and subsequent epithelium degeneration as the mouse developed, which was accompanied by gradually diminished K12 expression from the periphery of corneal epithelium and increased K13 expression toward the corneal center. Interestingly, K14 was detected in all layers of corneal epithelium of TGF-αECK mice, whereas it was limited at basal layer of controls. Transmission electron microscopy showed desmosome loss between corneal epithelial cells of TGF-αECK mice. In TGF-αECK mice, keratocan expression was abolished; α-SMA expression was increased while expression of Col1a1, Col1a2, and Col5a1 was diminished. Cell proliferation increased in the corneal epithelium and stroma, but not in the endothelium of TGF-αECK mice. Conclusions: Excess TGF-α had detrimental effects on corneal morphogenesis during mouse development in that it changed the cell fate of corneal epithelial cells to assume conjunctival phenotypic expression of K13, and keratocytes to myofibroblast phenotype.

Shp2-mediated MAPK pathway regulates ΔNp63 in epithelium to promote corneal innervation and homeostasis.

Corneal nerve fibers serving sensory, reflex, and neurotrophic functions sustain corneal homeostasis and transparency to promote normal visual function. It is not known whether corneal epithelium is also important for the corneal innervation. Herein, we generated a compound transgenic mouse strain, K14rtTA;tetO-Cre (TC);Shp2flox/flox, in which Shp2 was conditionally knocked out from K14-positive cells including corneal epithelium (Shp2K14ce-cko) upon doxycycline (dox) administration. Our data reveal that Shp2K14ce-cko caused corneal denervation. More specifically, corneal epithelium thickness and corneal sensitivity reduced dramatically in Shp2K14ce-cko mice. In addition, corneal epithelial wound healing after debridement was delayed substantially in the mutant mice. These defects manifested in Shp2K14ce-cko mice resemble the symptoms of human neurotrophic keratopathy. Our in vitro study shows that neurite outgrowth of the mouse primary trigeminal ganglion cells (TGCs) was inhibited when as cocultured with mouse corneal epithelial cells (TKE2) transfected by Shp2-, Mek1/2-, or ∆Np63-targeted siRNA but not by Akt1/2-targeted siRNA. Furthermore, ∆Np63 RNA interference downregulated Ngf expression in TKE2 cells. Cotransfection experiments reveal that Shp2 tightly monitored ΔNp63 protein levels in HEK293 and TKE2 cells. Taken together, our data suggest that the Shp2-mediated MAPK pathway regulated ΔNp63, which in turn positively regulated Ngf in epithelium to promote corneal innervation and epithelial homeostasis.

Repressed Wnt Signaling Accelerates the Aging Process in Mouse Eyes.

PURPOSE: Ocular aging is a natural process of functional decline in vision. When the process reaches a point that compromised vision affects normal daily activity, it manifests as age-related ocular diseases, such as age-related macular degeneration, cataracts, glaucoma, and pseudoexfoliation syndrome. We previously reported that repressed Wnt signaling accelerated the maturation of corneal epithelium during tissue development. Here, we explore the hypothesis that repressed Wnt signaling is associated with accelerated aging in mouse eyes. METHODS: Wnt ligand antagonist secreted frizzled-related protein 1 (sFRP1) was expressed in the corneal stroma by a tissue-specific, inducible, bitransgenic system. Tissue structure was analyzed for signs of aging. Signal transduction analysis was performed to determine the cellular response to sFRP1. RESULTS: Mouse eyes with sFRP1 expression showed signs of accelerated aging, resembling those found in pseudoexfoliation (PEX) syndrome, a known age-related disease. Specific findings include granular deposition on the surface of the anterior lens capsule, pigment loss from the anterior surface of the iris, the presence of fibrillary material in the anterior chamber, and changes in cell size (polymegethism) and shape (pleomorphism) of the corneal endothelial cells. In vitro studies demonstrated that sFRP1 did not inhibit Wnt5a function and that cells responded to sFRP1 and Wnt5a in a very similar manner. CONCLUSION: The expression of sFRP1 accelerates the aging process in mouse eyes and future studies are warranted to elucidate the underlying mechanisms.

Aberrant expression of a stabilized ß-catenin mutant in keratocytes inhibits mouse corneal epithelial stratification.

We previously reported that genetic deletion of ß-catenin in mouse corneal keratocytes resulted in precocious corneal epithelial stratification. In this study, to strengthen the notion that corneal keratocyte-derived Wnt/ß-catenin signaling regulates corneal epithelial stratification during mouse development, we examined the consequence of conditional overexpression of a stabilized ß-catenin mutant (Ctnnb1ΔE3) in corneal keratocytes via a doxycycline (Dox)-inducible compound transgenic mouse strain. Histological analysis showed that conditional overexpression of Ctnnb1ΔE3 in keratocytes inhibited corneal epithelial stratification during postnatal development. Unlike the corneal epithelium of the littermate controls, which consisted of 5-6 cell layers at postnatal day 21 (P21), the mutant corneal epithelium contained 1-2 or 2-3 cell layers after Dox induction from embryonic day 0 (E0) to P21 and from E9 to P21, respectively. X-gal staining revealed that Wnt/ß-catenin signaling activity was significantly elevated in the corneal keratocytes of the Dox-induced mutant mice, compared to the littermate controls. Furthermore, RT-qPCR and immunostaining data indicated that the expression of Bmp4 and ΔNp63 was downregulated in the mutant corneas, which was associated with reduced corneal epithelial proliferation in mutant epithelium, as revealed by immunofluorescent staining. However, the expression of Krt12, Krt14 and Pax6 in the mutant corneas was not altered after overexpression of Ctnnb1ΔE3 mutant protein in corneal keratocytes. Overall, mutant ß-catenin accumulation in the corneal keratocytes inhibited corneal epithelial stratification probably through downregulation of Bmp4 and ΔNp63 in the corneal epithelium.

Suppression of neovascularization in corneal stroma in a TRPA1-null mouse.

Corneal neovascularization and inflammatory fibrosis induced by severe injury or infection leads to tissue opacification and even blindness. Transient receptor potential (TRP) channel subtypes contribute to mediating these maladaptive responses through their interactions with other receptors. TRPV1 is one of the contributing channel isoforms inducing neovascularization in an alkali burn mouse wound healing model. VEGF-A upregulation contributes to neovascularization through interaction with its cognate receptors (VEGFR). Since the TRP isoform in this tissue, TRPA1, is also involved, we determined here if one of the pathways mediating neovascularization and immune cell infiltration involve an interaction between VEGFR and TRPA1 in a cauterization corneal mouse wound healing model. Localization of TRPA1 and endothelial cell (EC) CD31 immunostaining pattern intensity determined if TRPA1 expression was EC delimited during cauterization induced angiogenesis. Quantitative RT-PCR evaluated the effects of the absence of TRPA1 function on VEGF-A and TGF-ß1 mRNA expression during this process. Macrophage infiltration increased based on rises in F4/80 antigen immunoreactivity. TRPA1 immunostaining was absent on CD31-immunostained EC cells undergoing neovascularization, but it was present on other cell type(s) adhering to EC in vivo. Absence of TRPA1 expression suppressed both stromal neovascularization and inhibited macrophage infiltration. Similarly, the increases occurring in both VEGF-A and TGF-ß1 mRNA expression levels in WT tissue were blunted in the TRPA1-/- counterpart. On the other hand, in the macrophages their levels were invariant and their infiltration was inhibited. To determine if promotion by TRPA1 of angiogenesis was dependent on its expression on other unidentified cell types, the effects were compared of pharmacological manipulation of TRPA1 activity on EC proliferation tube formation and migration. In the presence and absence of a fibroblast containing feeder layer. Neither VEGF-induced increases in human vascular endothelial cell (HUVEC) proliferation nor migration were changed by a TRPA1 antagonist HC-030031 in the absence of a feeder layer. However, on a fibroblast feeder layer this antagonist suppressed HUVEC tube formation. In conclusion, during corneal wound healing transactivation by VEGFR of TRPA1 contributes to mediating neovascularization and macrophage infiltration. Such crosstalk is possible because of close proximity between VEGFR delimited expression on EC and TRPA1 expression restricted to cell types adhering to EC.

Sensory nerve supports epithelial stem cell function in healing of corneal epithelium in mice: the role of trigeminal nerve transient receptor potential vanilloid 4.

In order to understand the pathobiology of neurotrophic keratopathy, we established a mouse model by coagulating the first branch of the trigeminal nerve (V1 nerve). In our model, the sensory nerve in the central cornea disappeared and remaining fibers were sparse in the peripheral limbal region. Impaired corneal epithelial healing in the mouse model was associated with suppression of both cell proliferation and expression of stem cell markers in peripheral/limbal epithelium as well as a reduction of transient receptor potential vanilloid 4 (TRPV4) expression in tissue. TRPV4 gene knockout also suppressed epithelial repair in mouse cornea, although it did not seem to directly modulate migration of epithelium. In a co-culture experiment, TRPV4-introduced KO trigeminal ganglion upregulated nerve growth factor (NGF) in cultured corneal epithelial cells, but ganglion with a control vector did not. TRPV4 gene introduction into a damaged V1 nerve rescues the impairment of epithelial healing in association with partial recovery of the stem/progenitor cell markers and upregulation of cell proliferation and of NGF expression in the peripheral/limbal epithelium. Gene transfer of TRPV4 did not accelerate the regeneration of nerve fibers. Sensory nerve TRPV4 is critical to maintain stemness of peripheral/limbal basal cells, and is one of the major mechanisms of homeostasis maintenance of corneal epithelium.

Impaired healing of cornea incision injury in a TRPV1-deficient mouse.

The present study attempts to elucidate the role of TRPV1 cation channel receptor on primary repair in an incision-wounded mouse cornea in vivo. Previous study revealed that blocking TRPV1 suppressed myofibroblast formation and expression of transforming growth factor ß1 (TGFß1) in cultured keratocytes or ocular fibroblasts. Male C57BL/6 (wild-type; WT) mice and male C57BL/6 Trpv1-null (KO) mice incurred a full-thickness incision injury (1.8 mm in length, limbus to limbus) in the central cornea of one eye with a surgical blade under general and topical anesthesia. The injury was not sutured. On days 0, 5, and 10, the eyes were enucleated, processed for histology, immunohistochemistry, and real-time RT-PCR gene expression analysis to evaluate the effects of the loss of TRPV1 on primary healing. Electron microscopy observation was also performed to know the effect of the loss of TRPV1 on ultrastructure of keratocytes. The results showed that the loss of Trpv1 gene delayed closure of corneal stromal incision with hindered myofibroblast transdifferentiation along with declines in the expression of collagen Ia1 and TGFß1. Inflammatory cell infiltration was not affected by the loss of TRPV1. Ultrastructurally endoplasmic reticulum of TRPV1-null keratocytes was more extensively dilated as compared with WT keratocytes, suggesting an impairment of protein secretion by TRPV1-gene knockout. These results indicate that injury-related TRPV1 signal is involved in healing of stromal incision injury in a mouse cornea by selectively stimulating TGFß-induced granulation tissue formation.

Lack of plakoglobin impairs integrity and wound healing in corneal epithelium in mice.

We generated cornea-specific plakoglobin (Jup; junctional plakoglobin) knockout mice in order to investigate the function of plakoglobin on the maintenance of the homeostasis of corneal epithelium in mice. Cornea epithelium-specific conditional knockouts (JupCEΔ/CEΔ) (cKO) were obtained by breeding keratin12-Cre (Krt12-Cre) mice to Jup-floxed (Jupf/f) mice. Light and transmission electron microscopic and immunohistochemical analyses were carried out to determine consequence of the loss of plakoglobin on maintaining corneal epithelium integrity under mechanical stress, e.g., brushing and wound healing. Immunohistochemistry analysis demonstrated that, although Jup ablation did not affect BrdU incorporation, basal cell-like cells labeled for keratin 14 were ectopically present in the supra-basal layer in mutant corneal epithelium, suggestive of altered cell differentiation. Plakoglobin-deficient epithelium exhibits increased fragility against mechanical intervention when compared to wild-type controls under identical treatment. Closure of an epithelial defect was significantly delayed in JupCEΔ/CEΔ epithelium. Our findings indicate that the lack of plakoglobin significantly affects corneal epithelium differentiation, as well as its structural integrity. Plakoglobin is essential to the maintenance of the structure of the corneal epithelium and its wound healing.

Ectodysplasin A regulates epithelial barrier function through sonic hedgehog signalling pathway.

Ectodysplasin A (Eda), a member of the tumour necrosis factor superfamily, plays an important role in ectodermal organ development. An EDA mutation underlies the most common of ectodermal dysplasias, that is X-linked hypohidrotic ectodermal dysplasia (XLHED) in humans. Even though it lacks a developmental function, the role of Eda during the postnatal stage remains elusive. In this study, we found tight junctional proteins ZO-1 and claudin-1 expression is largely reduced in epidermal, corneal and lung epithelia in Eda mutant Tabby mice at different postnatal ages. These declines are associated with tail ulceration, corneal pannus formation and lung infection. Furthermore, topical application of recombinant Eda protein markedly mitigated corneal barrier dysfunction. Using cultures of a human corneal epithelial cell line and Tabby mouse skin tissue explants, Eda up-regulated expression of ZO-1 and claudin-1 through activation of the sonic hedgehog signalling pathway. We conclude that EDA gene expression contributes to the maintenance of epithelial barrier function. Such insight may help efforts to identify novel strategies for improving management of XLHED disease manifestations in a clinical setting.

RNA nanoparticle distribution and clearance in the eye after subconjunctival injection with and without thermosensitive hydrogels.

Thermodynamically and chemically stable RNA nanoparticles derived from the three-way junction (3WJ) of the pRNA from bacteriophage phi29 DNA packaging motor were examined previously for ocular delivery. It was reported that, after subconjunctival injection, RNA nanoparticles with tri-way shape entered the corneal cells but not the retinal cells, whereas particle with four-way shape entered both corneal and retinal cells. The present study evaluated ocular delivery of RNA nanoparticles with various shapes and sizes, and assessed the effect of thermosensitive hydrogels (poly(lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(lactic-co-glycolic acid); PLGA-PEG-PLGA) for increasing the retention of RNA nanoparticles in the eye. Fluorescence imaging of mouse eyes and fluorescence microscopy of dissected eye tissues from the conjunctiva, cornea, retina, and sclera were performed to determine the distribution and clearance of the nanoparticles in the eyes after subconjunctival injection in vivo. RNA nanoparticles entered the cells of the conjunctiva, cornea, retina, and sclera after subconjunctival delivery. The clearance of RNA pentagon was slower than both RNA square and triangle of the same designed edge length (10nm) in the eye, and the clearance of RNA squares of the longer edge lengths (10 and 20nm) was slower than RNA square of the shorter edge length (5nm), thus indicating that the size could affect ocular pharmacokinetics of the nanoparticles. At 24h after the injection, approximately 6-10% of the fluorescence signal from the larger nanoparticles in the study (RNA square of 20nm edge length and RNA pentagon of 10nm edge length) remained in the eye, and up to 70% of the retinal cells contained the nanoparticles. The results suggest that the larger nanoparticles were "gulped" in conjunctival, corneal, retinal, and scleral cells, similar to the behavior observed in macrophages. Additionally, the combination of RNA nanoparticles with the thermosensitive polymers increased the retention of the nanoparticles in the eye.

Generation and Characterization of a Novel Mouse Line, Keratocan-rtTA (KeraRT), for Corneal Stroma and Tendon Research.

Purpose: We created a novel inducible mouse line Keratocan-rtTA (KeraRT) that allows specific genetic modification in corneal keratocytes and tenocytes during development and in adults. Methods: A gene-targeting vector (Kera- IRES2-rtTA3) was constructed and inserted right after the termination codon of the mouse Kera allele via gene targeting techniques. The resulting KeraRT mouse was crossed to tet-O-Hist1H2B-EGFP (TH2B-EGFP) to obtain KeraRT/TH2B-EGFP compound transgenic mice, in which cells expressing Kera are labeled with green fluorescence protein (GFP) by doxycycline (Dox) induction. The expression patterns of GFP and endogenous Kera were examined in KeraRT/TH2B-EGFP. Moreover, KeraRT was bred with tet-O-TGF-α to generate a double transgenic mouse, KeraRT/tet-O-TGF-α, to overexpress TGF-α in corneal keratocytes upon Dox induction. Results: Strong GFP-labeled cells were detected in corneal stroma, limbs, and tail when KeraRT/TH2B-EGFP mice were fed Dox chow. There was no GFP in any single transgenic KeraRT or TH2B-EGFP mouse. Histological analysis showed that GFP in the cornea was limited to stromal keratocytes of KeraRT/TH2B-EGFP, which is consistent with Kera expression. Induction of GFP occurred in 24 hours and reached a plateau by 7 days after Dox induction. GFP could be detected 3-months after induction of KeraRT/TH2B-EGFP. Ectopic expression of TGF-α in corneal keratocytes caused hyperplasia in the corneal epithelium and stroma. Conclusions: The novel Dox inducible KeraRT driver mouse line is a useful genetic tool for gene manipulation and elucidating gene functions in corneal stroma and tendons of limbs and tail during embryonic development, homeostasis and pathogenesis.

The role of corneal stroma: A potential nutritional source for the cornea.

Corneal stroma plays a pivotal role in normal visual function. Anatomically, it is located between the outer epithelium and the inner endothelium and is the thickest layer of the cornea. Keratocytes in the stroma produce a variety of cellular products, including growth factors/cytokines, extracellular matrix (ECM) components, and kinases. These products support normal corneal development and homeostasis.

Mouse Corneal Stroma Fibroblast Primary Cell Culture.

This protocol is developed for primary cell culture of cornea stromal keratocytes isolated from neonatal mouse eyeballs. It provides an optimal condition to isolate stromal keratocytes which maintain high viability for cell culture.

Wnt/ß-catenin signaling modulates corneal epithelium stratification via inhibition of Bmp4 during mouse development.

The development of organs with an epithelial parenchyma relies on reciprocal mesenchymal-epithelial communication. Mouse corneal epithelium stratification is the consequence of a coordinated developmental process based on mesenchymal-epithelial interactions. The molecular mechanism underlying these interactions remains unclear. The Wnt/ß-catenin signaling pathway is involved in fundamental aspects of development through the regulation of various growth factors. Here, we show that conditional ablation of either ß-catenin (Ctnnb1(cKO)) or co-receptors Lrp5/6 (Lrp5/6(cKO)) in corneal stromal cells results in precocious stratification of the corneal epithelium. By contrast, ectopic expression of a murine Ctnnb1 gain-of-function mutant (Ctnnb1(cGOF)) retards corneal epithelium stratification. We also discovered that Bmp4 is upregulated in the absence of ß-catenin in keratocytes, which further triggers ERK1/2 (Mapk3/1) and Smad1/5 phosphorylation and enhances transcription factor p63 (Trp63) expression in mouse corneal basal epithelial cells and in a human corneal epithelial cell line (HTCE). Interestingly, mouse neonates given a subconjunctival BMP4 injection displayed a phenotype resembling that of Ctnnb1(cKO). Conditional ablation of Bmp4 eradicates the phenotype produced in Ctnnb1(cKO) mice. Furthermore, ChIP and promoter-luciferase assays show that ß-catenin binds to and suppresses Bmp4 promoter activity. These data support the concept that cross-talk between the Wnt/ß-catenin/Bmp4 axis (in the stromal mesenchyme) and Bmp4/p63 signaling (in the epithelium) plays a pivotal role in epithelial stratification during corneal morphogenesis.