The Effects of ROCK Inhibitor on Prevention of Dexamethasone-Induced Glaucoma Phenotype in Human Trabecular Meshwork Cells

Purpose

This study investigated the effects of dexamethasone (Dex) on human trabecular meshwork (TM) cells, a model of glucocorticoid-induced glaucoma, and evaluated the impact of ripasudil (Rip) as a co-delivery or sequential dosing strategy.

Methods

In vitro experiments were conducted to assess the effects of Dex and Rip on TM cells. Confocal microscopy was used to evaluate the impact of Dex and Rip on F-actin staining signals. Contractility of the TM cells upon Dex and Rip treatment mimicking co-delivery and sequential delivery was quantified using collagen gel contraction assay. Transepithelial electrical resistance (TEER) values and fluorescein isothiocyanate (FITC)-dextran permeability were also measured to assess the impact of Dex and Rip on TM cells.

Results

Dex and Rip did not exhibit cytotoxicity at the maximum tested concentration (20 µM). Dex-treated TM cells exhibited higher F-actin staining signals compared to controls, which were reduced when co-treated with Rip. Rip inhibited Dex-induced collagen gel contraction activity in both co-delivery and sequential treatments. Dex resulted in increased TEER values as the dose increased, whereas TEER values were maintained when co-treated with Rip.

Conclusions

Co-delivery of Rip has the potential to prevent glaucoma symptoms when patients are treated with Dex. This study highlights the importance of identifying strategies to reduce the side effects of prolonged use of glucocorticoids, such as Dex, in the treatment of various diseases.

Translational Relevance

This study demonstrates the potential of co-delivering ripasudil with dexamethasone to mitigate glucocorticoid-induced ocular hypertension and a secondary glaucoma that resembles primary open-angle glaucoma, providing insights for the development of novel preventive strategies in clinical care.

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.

Transient expression of Wnt5a elicits ocular features of pseudoexfoliation syndrome in mice

PURPOSE

Pseudoexfoliation (PEX) syndrome is an age-related systemic disease with ocular manifestations. The development of animal models is critical in order to elucidate the cause of the disease and to test potential treatment regimens. The purpose of this study is to report phenotypes found in mouse eyes injected with Adenovirus coding Wnt5a. Some of the phenotypes resemble those found in PEX patients while others are different.

METHODS

Recombinant Adenovirus coding Wnt5a or green fluorescent protein (GFP) were injected into mouse eyes. Two months after the injection, eyes were examined for PEX phenotypes using slit lamp, fluorescence stereomicroscope, histological staining, immunostaining and transmission electron microscope.

RESULT

Certain ocular features of PEX syndrome were found in mouse eyes injected with recombinant Adenovirus coding Wnt5a. These features include accumulation of exfoliation-like extracellular material on surfaces of anterior segment structures and its dispersion in the anterior chamber, saw-tooth appearance and disrupted basement membrane of the posterior iris pigment epithelium, iris stromal atrophy and disorganized ciliary zonules. Ultrastructure analysis of the exfoliation material revealed that the microfibril structure found in this model was different from those of PEX patients.

CONCLUSION

These features, resembling signs of ocular PEX syndrome in patients, suggest that new information obtained from this study will be helpful for developing better mouse models for PEX syndrome.

Study of corneal epithelial progenitor origin and the Yap1 requirement using keratin 12 lineage tracing transgenic mice

Key issues in corneal epithelium biology are the mechanism for corneal epithelium stem cells to maintain the corneal epithelial homeostasis and wound healing responses, and what are the regulatory molecular pathways involved. There are apparent discrepancies about the locations of the progenitor populations responsible for corneal epithelial self-renewal. We have developed a genetic mouse model to trace the corneal epithelial progenitor lineages during adult corneal epithelial homeostasis and wound healing response. Our data revealed that the early corneal epithelial progenitor cells expressing keratin-12 originated from limbus, and gave rise to the transit amplifying cells that migrated centripetally to differentiate into corneal epithelial cells. Our results support a model that both corneal epithelial homeostasis and wound healing are mainly maintained by the activated limbal stem cells originating form limbus, but not from the corneal basal epithelial layer. In the present study, we further demonstrated the nuclear expression of transcriptional coactivator YAP1 in the limbal and corneal basal epithelial cells and its essential role for maintaining the high proliferative potential of those corneal epithelial progenitor cells in vivo.

Targeted overexpression of TGF-α in the corneal epithelium of adult transgenic mice induces changes in anterior segment morphology and activates noncanonical Wnt signaling

PURPOSE

Transforming growth factor-alpha (TGF-α) transduces its signal through the epidermal growth factor receptor and is essential for corneal epithelial homeostasis. Previous studies have demonstrated that overexpression of TGF-α in the developing eye leads to anterior segment dysgenesis. However, the underlying mechanisms remain unclear. Here we examined the effects of TGF-α overexpression on adult ocular surface homeostasis.

METHODS

Binary Tet-On transgenic Krt12(rtTA)/tet-O-TGF-α mice were subjected to doxycycline (Dox) induction to overexpress TGF-α in the corneal epithelium. Intraocular pressure (IOP) was measured by noninvasive tonometry. The enucleated eyes of the experimental mice were subjected to histopathology, immunohistochemistry, and biochemistry examination.

RESULTS

Histologic and immunofluorescent examination showed that double-transgenic mice overexpressing TGF-α manifested peripheral anterior synechiae. Elevation of IOP, activation of glial cells, and loss of retinal ganglion cells were also observed. Quantitative real-time PCR revealed that the expressions of genes (RXRα, PITX2, and FOXC1) related to anterior segment dysgenesis were downregulated. Canonical Wnt signaling was suppressed, whereas noncanonical Wnt ligands (Wnt4 and Wnt5a) were upregulated. Increased myosin light chain phosphorylation suggested that noncanonical Wnt signaling is activated in affected eyes.

CONCLUSIONS

Overexpression of TGF-α in the corneal epithelium induces changes in anterior segment morphology. Corneal endothelial abnormalities are associated with the activation of the noncanonical Wnt and RhoA/ROCK signaling axis, indicating a potential application of RhoA/ROCK inhibitors as a therapeutic strategy for certain types of secondary angle-closure glaucoma.

Lumican expression in diaphragm induced by mechanical ventilation

Background

Diaphragmatic dysfunction found in the patients with acute lung injury required prolonged mechanical ventilation. Mechanical ventilation can induce production of inflammatory cytokines and excess deposition of extracellular matrix proteins via up-regulation of transforming growth factor (TGF)-β1. Lumican is known to participate in TGF-β1 signaling during wound healing. The mechanisms regulating interactions between mechanical ventilation and diaphragmatic injury are unclear. We hypothesized that diaphragmatic damage by short duration of mechanical stretch caused up-regulation of lumican that modulated TGF-β1 signaling.

Methods

Male C57BL/6 mice, either wild-type or lumican-null, aged 3 months, weighing between 25 and 30 g, were exposed to normal tidal volume (10 ml/kg) or high tidal volume (30 ml/kg) mechanical ventilation with room air for 2 to 8 hours. Nonventilated mice served as control groups.

Results

High tidal volume mechanical ventilation induced interfibrillar disassembly of diaphragmatic collagen fiber, lumican activation, type I and III procollagen, fibronectin, and α-smooth muscle actin (α-SMA) mRNA, production of free radical and TGF-β1 protein, and positive staining of lumican in diaphragmatic fiber. Mechanical ventilation of lumican deficient mice attenuated diaphragmatic injury, type I and III procollagen, fibronectin, and α-SMA mRNA, and production of free radical and TGF-β1 protein. No significant diaphragmatic injury was found in mice subjected to normal tidal volume mechanical ventilation.

Conclusion

Our data showed that high tidal volume mechanical ventilation induced TGF-β1 production, TGF-β1-inducible genes, e.g., collagen, and diaphragmatic dysfunction through activation of the lumican.

Promiscuous recombination of LoxP alleles during gametogenesis in cornea Cre driver mice

PURPOSE

To examine whether promiscuous Cre/LoxP recombination happens during gametogenesis in double transgenic mice carrying LoxP modified alleles and Cre transgene driven by tissue-specific promoter outside the gonads of adult mice.

METHODS

Cre driver mice were crossbred with reporter mouse lines (e.g., ZEG and Rosa26R) to obtain Cre/ZEG and Cre/Rosa26R double transgenic mice. The frequency of promiscuous LoxP/Cre recombination was determined by the expression of second reporter genes in the offspring of double transgenic mice.

RESULTS

The frequency of promiscuous LoxP/Cre recombination varied in different lines of Cre driver mice and in the sex of the same driver mice with higher penetrance in male than in female double transgenic mice. Polymerase chain reaction (PCR) and recombination analysis demonstrate that the recombination of floxed allele occurs during the transition from spermatogonia (diploid) to primary spermatocyte (tetraploid) in the testis. Thereby, target-floxed allele(s) may be ubiquitously ablated in experimental animals intended for tissue-specific gene deletion.

CONCLUSIONS

Gametogenesis-associated recombination should always be examined in tissue-specific gene ablation studies.

A role for the mitogen-activated protein kinase kinase kinase 1 in epithelial wound healing

The mitogen-activated protein kinase kinase (MEK) kinase 1 (MEKK1) mediates activin B signals required for eyelid epithelium morphogenesis during mouse fetal development. The present study investigates the role of MEKK1 in epithelial wound healing, another activin-regulated biological process. In a skin wound model, injury markedly stimulates MEKK1 expression and activity, which are in turn required for the expression of genes involved in extracellular matrix (ECM) homeostasis. MEKK1 ablation or down-regulation by interfering RNA significantly delays skin wound closure and impairs activation of Jun NH2-terminal kinases, induction of plasminogen activator inhibitor (PAI)-1, and restoration of cell-cell junctions of the wounded epidermis. Conversely, expression of wild-type MEKK1 accelerates reepithelialization of full-thickness skin and corneal debridement wounds by mechanisms involving epithelial cell migration, a cell function that is partially abolished by neutralizing antibodies for PAI-1 and metalloproteinase III. Our data suggest that MEKK1 transmits wound signals, leading to the transcriptional activation of genes involved in ECM homeostasis, epithelial cell migration, and wound reepithelialization.

Keratocan, a cornea-specific keratan sulfate proteoglycan, is regulated by lumican

Lumican is an extracellular matrix glycoprotein widely distributed in mammalian connective tissues. Corneal lumican modified with keratan sulfate constitutes one of the major proteoglycans of the stroma. Lumican-null mice exhibit altered collagen fibril organization and loss of corneal transparency. A closely related protein, keratocan, carries the remaining keratan sulfate of the cornea, but keratocan-null mice exhibit a less severe corneal phenotype. In the current study, we examined the effect of lumican overexpression in corneas of wild type mice. These mice showed no alteration in collagen organization or transparency but had increased keratocan expression at both protein and mRNA levels. Corneas of lumican-null mice showed decreased keratocan. This coupling of keratocan expression with lumican also was observed after intrastromal injection of a lumican expression minigene into the corneal stroma of Lum-/- mice. Small interfering RNA knockdown of lumican in vitro reduced keratocan expression, whereas co-injection of a lumican-expressing minigene with a beta-galactosidase reporter driven by the keratocan promoter demonstrated an increase of keratocan transcriptional activity in response to lumican expression in Lum-/- corneas in vivo. These observations demonstrate that lumican has a novel regulatory role in keratocan expression at the transcriptional level. Such results help provide an explanation for the differences in severity of corneal manifestation found in Lum-/- and Kera-/- mice. The results also suggest a critical level of small proteoglycans to be essential for collagen organization but that overabundance is not detrimental to extracellular matrix morphogenesis.

Soluble lumican glycoprotein purified from human amniotic membrane promotes corneal epithelial wound healing

PURPOSE

To purify and characterize the glycoprotein lumican, isolated from human amniotic membrane (AM), and to examine its efficacy in treating corneal epithelium debridement.

METHODS

An affinity-purified, anti-human lumican antibody-conjugated protein A Sepharose column was used to purify soluble lumican protein from human AM. The purified AM lumican was characterized by two-dimensional and SDS gel electrophoresis, plus Western blot analysis with anti-lumican antibody. The effects of lumican on corneal epithelial wound healing were examined in an organ culture mouse eye model.

RESULTS

Lumican was found to be abundantly present in the stroma of human AM. It was extracted from the AM by isotonic, 1 M NaCl, and 4 M guanidine HCl solutions, suggesting that it is present in both the soluble and matrix-bound states. In two-dimensional gel electrophoresis, the 50-kDa human amniotic lumican purified by antibody-conjugated affinity chromatography migrated in a smear between pH 3.0 and 6.0. After endo-beta-galactosidase digestion, it existed as a single core protein at pH 6.0, suggesting that native human amniotic lumican is a glycoprotein with short sugar moiety. Addition of purified human AM lumican to cultured medium promoted re-epithelialization and enhanced cell proliferation of wild-type mouse corneal epithelial cells in an organ culture. In lumican-knockout (lum(-/-)) mice, the effect of human lumican on promoting corneal epithelial wound healing was even more dramatic than in wild-type mice.

CONCLUSIONS

The diversified functions of lumican include modulation of epithelial cells in wound healing and serving as an extracellular matrix component. Administration of lumican may be beneficial for treating epithelial defects in the cornea and other tissues.

Role of lumican in the corneal epithelium during wound healing

Lumican regulates collagenous matrix assembly as a keratan sulfate proteoglycan in the cornea and is also present in the connective tissues of other organs and embryonic corneal stroma as a glycoprotein. In normal unwounded cornea, lumican is expressed by stromal keratocytes. Our data show that injured mouse corneal epithelium ectopically and transiently expresses lumican during the early phase of wound healing, suggesting a potential lumican functionality unrelated to regulation of collagen fibrillogenesis, e. g. modulation of epithelial cell adhesion or migration. An anti-lumican antibody was found to retard corneal epithelial wound healing in cultured mouse eyes. Healing of a corneal epithelial injury in Lum(-/-) mice was significantly delayed compared with Lum(+/-) mice. These observations indicate that lumican expressed in injured epithelium may modulate cell behavior such as adhesion or migration, thus contributing to corneal epithelial wound healing.