Predatory bacteria can reduce Pseudomonas aeruginosa induced corneal perforation and proliferation in a rabbit keratitis model

PURPOSE

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

METHODS

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic ΔlasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

RESULTS

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n = 24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n = 25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The ΔlasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus.

CONCLUSION

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Predatory Bacteria can Reduce Pseudomonas aeruginosa Induced Corneal Perforation and Proliferation in a Rabbit Keratitis Model

Purpose

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

Methods

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic Δ lasR mutant and co-injected with PBS or B. bacteriovorus . After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

Results

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n=25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The Δ lasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus .

Conclusion

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Increased LCN2 (lipocalin 2) in the RPE decreases autophagy and activates inflammasome-ferroptosis processes in a mouse model of dry AMD

In dry age-related macular degeneration (AMD), LCN2 (lipocalin 2) is upregulated. Whereas LCN2 has been implicated in AMD pathogenesis, the mechanism remains unknown. Here, we report that in retinal pigmented epithelial (RPE) cells, LCN2 regulates macroautophagy/autophagy, in addition to maintaining iron homeostasis. LCN2 binds to ATG4B to form an LCN2-ATG4B-LC3-II complex, thereby regulating ATG4B activity and LC3-II lipidation. Thus, increased LCN2 reduced autophagy flux. Moreover, RPE cells from cryba1 KO, as well as sting1 KO and Sting1Gt mutant mice (models with abnormal iron chelation), showed decreased autophagy flux and increased LCN2, indicative of CGAS- and STING1-mediated inflammasome activation. Live cell imaging of RPE cells with elevated LCN2 also showed a correlation between inflammasome activation and increased fluorescence intensity of the Liperfluo dye, indicative of oxidative stress-induced ferroptosis. Interestingly, both in human AMD patients and in mouse models with a dry AMD-like phenotype (cryba1 cKO and KO), the LCN2 homodimer variant is increased significantly compared to the monomer. Sub-retinal injection of the LCN2 homodimer secreted by RPE cells into NOD-SCID mice leads to retinal degeneration. In addition, we generated an LCN2 monoclonal antibody that neutralizes both the monomer and homodimer variants and rescued autophagy and ferroptosis activities in cryba1 cKO mice. Furthermore, the antibody rescued retinal function in cryba1 cKO mice as assessed by electroretinography. Here, we identify a molecular pathway whereby increased LCN2 elicits pathophysiology in the RPE, cells known to drive dry AMD pathology, thus providing a possible therapeutic strategy for a disease with no current treatment options.Abbreviations: ACTB: actin, beta; Ad-GFP: adenovirus-green fluorescent protein; Ad-LCN2: adenovirus-lipocalin 2; Ad-LCN2-GFP: adenovirus-LCN2-green fluorescent protein; LCN2AKT2: AKT serine/threonine kinase 2; AMBRA1: autophagy and beclin 1 regulator 1; AMD: age-related macular degeneration; ARPE19: adult retinal pigment epithelial cell line-19; Asp278: aspartate 278; ATG4B: autophagy related 4B cysteine peptidase; ATG4C: autophagy related 4C cysteine peptidase; ATG7: autophagy related 7; ATG9B: autophagy related 9B; BLOC-1: biogenesis of lysosomal organelles complex 1; BLOC1S1: biogenesis of lysosomal organelles complex 1 subunit 1; C57BL/6J: C57 black 6J; CGAS: cyclic GMP-AMP synthase; ChQ: chloroquine; cKO: conditional knockout; Cys74: cysteine 74; Dab2: DAB adaptor protein 2; Def: deferoxamine; DHE: dihydroethidium; DMSO: dimethyl sulfoxide; ERG: electroretinography; FAC: ferric ammonium citrate; Fe2+: ferrous; FTH1: ferritin heavy chain 1; GPX: glutathione peroxidase; GST: glutathione S-transferase; H2O2: hydrogen peroxide; His280: histidine 280; IFNL/IFNλ: interferon lambda; IL1B/IL-1β: interleukin 1 beta; IS: Inner segment; ITGB1/integrin β1: integrin subunit beta 1; KO: knockout; LC3-GST: microtubule associated protein 1 light chain 3-GST; C-terminal fusion; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; LCN2: lipocalin 2; mAb: monoclonal antibody; MDA: malondialdehyde; MMP9: matrix metallopeptidase 9; NLRP3: NLR family pyrin domain containing 3; NOD-SCID: nonobese diabetic-severe combined immunodeficiency; OS: outer segment; PBS: phosphate-buffered saline; PMEL/PMEL17: premelanosome protein; RFP: red fluorescent protein; rLCN2: recombinant LCN2; ROS: reactive oxygen species; RPE SM: retinal pigmented epithelium spent medium; RPE: retinal pigment epithelium; RSL3: RAS-selective lethal; scRNAseq: single-cell ribonucleic acid sequencing; SD-OCT: spectral domain optical coherence tomography; shRNA: small hairpin ribonucleic acid; SM: spent medium; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; STING1: stimulator of interferon response cGAMP interactor 1; TYR: tyrosinase; VCL: vinculin; WT: wild type.

Non-retinoid chaperones improve rhodopsin homeostasis in a mouse model of retinitis pigmentosa

Rhodopsin-associated (RHO-associated) retinitis pigmentosa (RP) is a progressive retinal disease that currently has no cure. RHO protein misfolding leads to disturbed proteostasis and the death of rod photoreceptors, resulting in decreased vision. We previously identified nonretinoid chaperones of RHO, including YC-001 and F5257-0462, by small-molecule high-throughput screening. Here, we profile the chaperone activities of these molecules toward the cell-surface level of 27 RP-causing human RHO mutants in NIH3T3 cells. Furthermore, using retinal explant culture, we show that YC-001 improves retinal proteostasis by supporting RHO homeostasis in Rho^P23H/+ mouse retinae, which results in thicker outer nuclear layers (ONL), indicating delayed photoreceptor degeneration. Interestingly, YC-001 ameliorated retinal immune responses and reduced the number of microglia/macrophages in the Rho^P23H/+ retinal explants. Similarly, F5257-0462 also protects photoreceptors in Rho^P23H/+ retinal explants. In vivo, intravitreal injection of YC-001 or F5257-0462 microparticles in PBS shows that F5257-0462 has a higher efficacy in preserving photoreceptor function and delaying photoreceptor death in Rho^P23H/+ mice. Collectively, we provide proof of principle that nonretinoid chaperones are promising drug candidates in treating RHO-associated RP.

Retinal ganglion cell survival after severe optic nerve injury is modulated by crosstalk between Jak/Stat signaling and innate immune responses in the zebrafish retina

Visual information is transmitted from the eye to the brain along the optic nerve, a structure composed of retinal ganglion cell (RGC) axons. The optic nerve is highly vulnerable to damage in neurodegenerative diseases, such as glaucoma, and there are currently no FDA-approved drugs or therapies to protect RGCs from death. Zebrafish possess remarkable neuroprotective and regenerative abilities. Here, utilizing an optic nerve transection (ONT) injury and an RNA-seq-based approach, we identify genes and pathways active in RGCs that may modulate their survival. Through pharmacological perturbation, we demonstrate that Jak/Stat pathway activity is required for RGC survival after ONT. Furthermore, we show that immune responses directly contribute to RGC death after ONT; macrophages/microglia are recruited to the retina and blocking neuroinflammation or depleting these cells after ONT rescues survival of RGCs. Taken together, these data support a model in which crosstalk between macrophages/microglia and RGCs, mediated by Jak/Stat pathway activity, regulates RGC survival after optic nerve injury.

A whole-mount immunohistochemistry protocol for detection of mouse corneal nerves

A cornea is innervated by sensory nerves, which branch into thick trunks, subbasal plexuses, and sensory endings. Appropriate assessment of nerve structure in a tissue provides a more complete understanding of the role of nerves in health and disease. Here, we present a whole-mount immunohistochemistry protocol that facilitates evaluation of nerve architecture throughout the mouse cornea. The fixation step in this protocol allows for reliable detection of nerve structures within the cornea and likely other tissues.

For complete details on the use and execution of this protocol, please refer to Yun et al, (2020).

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This protocol will assist in maintaining appropriate morphology of corneal nerves

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Neurons are sensitive to fixation methods and durations

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1.3% PFA is the ideal fixative for fluorescent imaging of corneal nerves

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This protocol can be used to guide fluorescent imaging at other tissues

Production of the Cytokine VEGF-A by CD4+ T and Myeloid Cells Disrupts the Corneal Nerve Landscape and Promotes Herpes Stromal Keratitis

Herpes simplex virus type 1 (HSV-1)-infected corneas can develop a blinding immunoinflammatory condition called herpes stromal keratitis (HSK), which involves the loss of corneal sensitivity due to retraction of sensory nerves and subsequent hyperinnervation with sympathetic nerves. Increased concentrations of the cytokine VEGF-A in the cornea are associated with HSK severity. Here, we examined the impact of VEGF-A on neurologic changes that underly HSK using a mouse model of HSV-1 corneal infection. Both CD4⁺ T cells and myeloid cells produced pathogenic levels of VEGF-A within HSV-1-infected corneas, and CD4⁺ cell depletion promoted reinnervation of HSK corneas with sensory nerves. In vitro, VEGF-A from infected corneas repressed sensory nerve growth and promoted sympathetic nerve growth. Neutralizing VEGF-A in vivo using bevacizumab inhibited sympathetic innervation, promoted sensory nerve regeneration, and alleviated disease. Thus, VEGF-A can shape the sensory and sympathetic nerve landscape within the cornea, with implications for the treatment of blinding corneal disease.

Blowing epithelial cell bubbles with GumB: ShlA-family pore-forming toxins induce blebbing and rapid cellular death in corneal epithelial cells

Medical devices, such as contact lenses, bring bacteria in direct contact with human cells. Consequences of these host-pathogen interactions include the alteration of mammalian cell surface architecture and induction of cellular death that renders tissues more susceptible to infection. Gram-negative bacteria known to induce cellular blebbing by mammalian cells, Pseudomonas and Vibrio species, do so through a type III secretion system-dependent mechanism. This study demonstrates that a subset of bacteria from the Enterobacteriaceae bacterial family induce cellular death and membrane blebs in a variety of cell types via a type V secretion-system dependent mechanism. Here, we report that ShlA-family cytolysins from Proteus mirabilis and Serratia marcescens were required to induce membrane blebbling and cell death. Blebbing and cellular death were blocked by an antioxidant and RIP-1 and MLKL inhibitors, implicating necroptosis in the observed phenotypes. Additional genetic studies determined that an IgaA family stress-response protein, GumB, was necessary to induce blebs. Data supported a model where GumB and shlBA are in a regulatory circuit through the Rcs stress response phosphorelay system required for bleb formation and pathogenesis in an invertebrate model of infection and proliferation in a phagocytic cell line. This study introduces GumB as a regulator of S. marcescens host-pathogen interactions and demonstrates a common type V secretion system-dependent mechanism by which bacteria elicit surface morphological changes on mammalian cells. This type V secretion-system mechanism likely contributes bacterial damage to the corneal epithelial layer, and enables access to deeper parts of the tissue that are more susceptible to infection.

Radial and Circumferential Collagen Fibers Are a Feature of the Peripapillary Sclera of Human, Monkey, Pig, Cow, Goat, and Sheep

Purpose

To test the hypothesis that human, monkey, pig, sheep, cow, and goat eyes exhibit circumferential, radial, and interweaving collagen architecture in the posterior sclera.

Methods

We analyzed 1,327 cryosections from the posterior poles of 4 human, 4 monkey, 5 pig, 8 sheep, 1 goat, and 2 cow eyes. Images were acquired using polarized light microscopy and processed to obtain polar fiber orientations relative to the center of the canal. Circumferential, radial, and interweaving regions were identified and analyzed for mean fiber orientation and anisotropy and region width and thickness.

Results

Every eye exhibited circumferential, radial, and interweaving fibers in consistent locations. Radial fibers extended out from near the canal into the peripapillary and peripheral sclera in the innermost sclera. Circumferential fibers were directly adjacent to the canal and most prevalent in the outermost, posterior sclera. Interweaving fibers were found throughout the sclera thickness. Across all species, median anisotropy in the radial, circumferential, and interweaving regions were 0.95, 0.96, and 0.28, respectively.

Conclusions

Regions of radial, circumferential, and interweaving fibers occur in the posterior pole sclera of human, monkey, pig, sheep, cow, and goat eyes. The consistency across species in scleral architecture suggests that they are primary organizational components whose functions should be better understood.

Structure-Function Changes of the Porcine Distal Outflow Tract in Response to Nitric Oxide

Purpose

To correlate outflow function and outflow tract vessel diameter changes induced by nitric oxide (NO).

Methods

In a porcine anterior segment perfusion model, the effects of a nitric oxide donor (100 μM DETA-NO) on outflow facility were compared with controls (n = 8 per group) with trabecular meshwork (TM) and after circumferential ab interno trabeculectomy (AIT). Outflow structures were assessed with spectral-domain optical coherence tomography (SD-OCT) before and after NO, or an NO synthase inhibitor (100 μM L-NAME) and the vasoconstrictor, endothelin-1 (100 pg/mL ET-1). Scans were processed with a custom macroscript and aligned for automated reslicing and quantification of cross-sectional outflow tract areas (CSA).

Results

The facility increased after DETA-NO (Δ of 0.189 ± 0.081 μL/min·mm Hg, P = 0.034) and AIT (Δ of 0.251 ± 0.094 μL/min·mm Hg, P = 0.009), respectively. Even after AIT, DETA-NO increased the facility by 61.5% (Δ of 0.190 ± 0.074 μL/min·mm Hg, P = 0.023) and CSA by 13.9% (P < 0.001). L-NAME + ET-1 decreased CSA by -8.6% (P < 0.001). NO increased the diameter of focal constrictions 5.0 ± 3.8-fold.

Conclusions

NO can dilate vessels of the distal outflow tract and increase outflow facility in a TM-independent fashion. There are short, focally constricting vessel sections that display large diameter changes and may have a substantial impact on outflow.

Spatial Patterns and Age-Related Changes of the Collagen Crimp in the Human Cornea and Sclera

Purpose

Collagen is the main load-bearing component of the eye, and collagen crimp is a critical determinant of tissue mechanical behavior. We test the hypothesis that collagen crimp morphology varies over the human cornea and sclera and with age.

Methods

We analyzed 42 axial whole-globe sections from 20 normal eyes of 20 human donors, ranging in age from 0.08 (1 month) to 97 years. The sections were imaged using polarized light microscopy to obtain μm-scale fiber bundle/lamellae orientation from two corneal and six scleral regions. Crimp morphology was quantified through waviness, tortuosity, and amplitude.

Results

Whole-globe median waviness, tortuosity, and amplitude were 0.127 radians, 1.002, and 0.273 μm, respectively. These parameters, however, were not uniform over the globe, instead exhibiting distinct, consistent patterns. All crimp parameters decreased significantly with age, with significantly different age-related decreases between regions. The crimp morphology of the limbus changed the most drastically with age, such that it had the largest crimp in neonates, and among the smallest in the elderly.

Conclusions

Age-related decreases in crimp parameters are likely one of the mechanisms underlying age-related stiffening of the sclera and cornea, potentially influencing sensitivity to IOP. Further work is needed to determine the biomechanical implications of the crimp patterns observed. The comparatively large changes in the crimp morphology of the limbus, especially in the early years of life, suggest that crimp in this region may play a role in eye development, although the exact nature of this is unclear.

Regeneration of the zebrafish retinal pigment epithelium after widespread genetic ablation

The retinal pigment epithelium (RPE) is a specialized monolayer of pigmented cells within the eye that is critical for maintaining visual system function. Diseases affecting the RPE have dire consequences for vision, and the most prevalent of these is atrophic (dry) age-related macular degeneration (AMD), which is thought to result from RPE dysfunction and degeneration. An intriguing possibility for treating RPE degenerative diseases like atrophic AMD is the stimulation of endogenous RPE regeneration; however, very little is known about the mechanisms driving successful RPE regeneration in vivo. Here, we developed a zebrafish transgenic model (rpe65a:nfsB-eGFP) that enabled ablation of large swathes of mature RPE. RPE ablation resulted in rapid RPE degeneration, as well as degeneration of Bruch’s membrane and underlying photoreceptors. Using this model, we demonstrate for the first time that zebrafish are capable of regenerating a functional RPE monolayer after RPE ablation. Regenerated RPE cells first appear at the periphery of the RPE, and regeneration proceeds in a peripheral-to-central fashion. RPE ablation elicits a robust proliferative response in the remaining RPE. Subsequently, proliferative cells move into the injury site and differentiate into RPE. BrdU incorporation assays demonstrate that the regenerated RPE is likely derived from remaining peripheral RPE cells. Pharmacological disruption using IWR-1, a Wnt signaling antagonist, significantly reduces cell proliferation in the RPE and impairs overall RPE recovery. These data demonstrate that the zebrafish RPE possesses a robust capacity for regeneration and highlight a potential mechanism through which endogenous RPE regenerate in vivo.

Diseases resulting in retinal pigment epithelium (RPE) degeneration are among the leading causes of blindness worldwide, and no therapy exists that can replace RPE or restore lost vision. One intriguing possibility is the development of therapies focused on stimulating endogenous RPE regeneration. For this to be possible, we must first gain a deeper understanding of the mechanisms underlying RPE regeneration. Here, we develop a transgenic zebrafish system through which we ablate large swathes of mature RPE and demonstrate that zebrafish regenerate RPE after widespread injury. Injury-adjacent RPE proliferate and regenerate RPE, suggesting that they are the source of regenerated tissue. Finally, we demonstrate that Wnt signaling may be involved in RPE regeneration. These findings establish a versatile in vivo model through which the molecular and cellular underpinnings of RPE regeneration can be further characterized.

Polarized light microscopy for 3-dimensional mapping of collagen fiber architecture in ocular tissues

Collagen fibers play a central role in normal eye mechanics and pathology. In ocular tissues, collagen fibers exhibit a complex 3-dimensional (3D) fiber orientation, with both in-plane (IP) and out-of-plane (OP) orientations. Imaging techniques traditionally applied to the study of ocular tissues only quantify IP fiber orientation, providing little information on OP fiber orientation. Accurate description of the complex 3D fiber microstructures of the eye requires quantifying full 3D fiber orientation. Herein, we present 3dPLM, a technique based on polarized light microscopy developed to quantify both IP and OP collagen fiber orientations of ocular tissues. The performance of 3dPLM was examined by simulation and experimental verification and validation. The experiments demonstrated an excellent agreement between extracted and true 3D fiber orientation. Both IP and OP fiber orientations can be extracted from the sclera and the cornea, providing previously unavailable quantitative 3D measures and insight into the tissue microarchitecture. Together, the results demonstrate that 3dPLM is a powerful imaging technique for the analysis of ocular tissues.

Polarized light microscopy for 3-dimensional mapping of collagen fiber architecture in ocular tissues

Collagen fibers play a central role in normal eye mechanics and pathology. In ocular tissues, collagen fibers exhibit a complex 3-dimensional (3D) fiber orientation, with both in-plane (IP) and out-of-plane (OP) orientations. Imaging techniques traditionally applied to the study of ocular tissues only quantify IP fiber orientation, providing little information on OP fiber orientation. Accurate description of the complex 3D fiber microstructures of the eye requires quantifying full 3D fiber orientation. Herein, we present 3dPLM, a technique based on polarized light microscopy developed to quantify both IP and OP collagen fiber orientations of ocular tissues. The performance of 3dPLM was examined by simulation and experimental verification and validation. The experiments demonstrated an excellent agreement between extracted and true 3D fiber orientation. Both IP and OP fiber orientations can be extracted from the sclera and the cornea, providing previously unavailable quantitative 3D measures and insight into the tissue microarchitecture. Together, the results demonstrate that 3dPLM is a powerful imaging technique for the analysis of ocular tissues.

Rapid learning curve assessment in an ex vivo training system for microincisional glaucoma surgery

Increasing prevalence and cost of glaucoma have increased the demand for surgeons well trained in newer, microincisional surgery. These procedures occur in a highly confined space, making them difficult to learn by observation or assistance alone as is currently done. We hypothesized that our ex vivo outflow model is sensitive enough to allow computing individual learning curves to quantify progress and refine techniques. Seven trainees performed nine trabectome-mediated ab interno trabeculectomies in pig eyes (n = 63). An expert surgeon rated the procedure using an Operating Room Score (ORS). The extent of outflow beds accessed was measured with canalograms. Data was fitted using mixed effect models. ORS reached a half-maximum on an asymptote after only 2.5 eyes. Surgical time decreased by 1.4 minutes per eye in a linear fashion. The ablation arc followed an asymptotic function with a half-maximum inflection point after 5.3 eyes. Canalograms revealed that this progress did not correlate well with improvement in outflow, suggesting instead that about 30 eyes are needed for true mastery. This inexpensive pig eye model provides a safe and effective microsurgical training model and allows objective quantification of outcomes for the first time.

Training strategies and outcomes of ab interno trabeculectomy with the trabectome

Plasma-mediated ab interno trabeculectomy with the trabectome was first approved by the US Food and Drug Administration in 2004 for use in adult and pediatric glaucomas. Since then, increased clinical experience and updated outcome data have led to its expanded use, including a range of glaucomas and angle presentations, previously deemed to be relatively contraindicated. The main benefits are a high degree of safety, ease, and speed compared to traditional filtering surgery and tube shunts. The increasing burden of glaucoma and expanding life expectancy has resulted in demand for well-trained surgeons. In this article, we discuss the results of trabectome surgery in standard and nonstandard indications. We present training strategies of the surgical technique that include a pig eye model, and visualization exercises that can be performed before and at the conclusion of standard cataract surgery in patients who do not have glaucoma. We detail the mechanism of enhancing the conventional outflow pathway and describe methods of visualization and function testing.

Training strategies and outcomes of ab interno trabeculectomy with the trabectome

Plasma-mediated ab interno trabeculectomy with the trabectome was first approved by the US Food and Drug Administration in 2004 for use in adult and pediatric glaucomas. Since then, increased clinical experience and updated outcome data have led to its expanded use, including a range of glaucomas and angle presentations, previously deemed to be relatively contraindicated. The main benefits are a high degree of safety, ease, and speed compared to traditional filtering surgery and tube shunts. The increasing burden of glaucoma and expanding life expectancy has resulted in demand for well-trained surgeons. In this article, we discuss the results of trabectome surgery in standard and nonstandard indications. We present training strategies of the surgical technique that include a pig eye model, and visualization exercises that can be performed before and at the conclusion of standard cataract surgery in patients who do not have glaucoma. We detail the mechanism of enhancing the conventional outflow pathway and describe methods of visualization and function testing.

Differential Canalograms Detect Outflow Changes from Trabecular Micro-Bypass Stents and Ab Interno Trabeculectomy

Recently introduced microincisional glaucoma surgeries that enhance conventional outflow offer a favorable risk profile over traditional surgeries, but can be unpredictable. Two paramount challenges are the lack of an adequate training model for angle surgeries and the absence of an intraoperative quantification of surgical success. To address both, we developed an ex vivo training system and a differential, quantitative canalography method that uses slope-adjusted fluorescence intensities of two different chromophores to avoid quenching. We assessed outflow enhancement by trabecular micro-bypass (TMB) implantation or by ab interno trabeculectomy (AIT). In this porcine model, TMB resulted in an insignificant (p > 0.05) outflow increase of 13 ± 5%, 14 ± 8%, 9 ± 3%, and 24 ± 9% in the inferonasal, superonasal, superotemporal, and inferotemporal quadrant, respectively. AIT caused a 100 ± 50% (p = 0.002), 75 ± 28% (p = 0.002), 19 ± 8%, and 40 ± 21% increase in those quadrants. The direct gonioscopy and tactile feedback provided a surgical experience that was very similar to that in human patients. Despite the more narrow and discontinuous circumferential drainage elements in the pig with potential for underperformance or partial stent obstruction, unequivocal patterns of focal outflow enhancement by TMB were seen in this training model. AIT achieved extensive access to outflow pathways beyond the surgical site itself.

The hyaloid vasculature facilitates basement membrane breakdown during choroid fissure closure in the zebrafish eye

A critical aspect of vertebrate eye development is closure of the choroid fissure (CF). Defects in CF closure result in colobomas, which are a significant cause of childhood blindness worldwide. Despite the growing number of mutated loci associated with colobomas, we have a limited understanding of the cell biological underpinnings of CF closure. Here, we utilize the zebrafish embryo to identify key phases of CF closure and regulators of the process. Utilizing Laminin-111 as a marker for the basement membrane (BM) lining the CF, we determine the spatial and temporal patterns of BM breakdown in the CF, a prerequisite for CF closure. Similarly, utilizing a combination of in vivo time-lapse imaging, β-catenin immunohistochemistry and F-actin staining, we determine that tissue fusion, which serves to close the fissure, follows BM breakdown closely. Periocular mesenchyme (POM)-derived endothelial cells, which migrate through the CF to give rise to the hyaloid vasculature, possess distinct actin foci that correlate with regions of BM breakdown. Disruption of talin1, which encodes a regulator of the actin cytoskeleton, results in colobomas and these correlate with structural defects in the hyaloid vasculature and defects in BM breakdown. cloche mutants, which entirely lack a hyaloid vasculature, also possess defects in BM breakdown in the CF. Taken together, these data support a model in which the hyaloid vasculature and/or the POM-derived endothelial cells that give rise to the hyaloid vasculature contribute to BM breakdown during CF closure.

A Central Role for Sympathetic Nerves in Herpes Stromal Keratitis in Mice

Purpose

Herpes simplex virus type 1 (HSV-1) is a neurotrophic virus that can cause herpes stromal keratitis (HSK), a severe corneal inflammation that can lead to corneal scarring and blindness. This study identified neurologic changes that occur in HSV-1–infected corneas and related them to HSV-1–induced immunopathology.

Methods

Corneas of BALB/c and C57BL/6 mice were infected with HSV-1 strains that induce HSK. Changes in sensory nerves were identified by immunofluorescence staining of sensory and sympathetic nerves for substance P (SP) and tyrosine hydroxylase (TH), respectively, and confocal microscopic examination. Some mice received superior cervical ganglionectomy (SCGx) to eliminate sympathetic nerves from the cornea.

Results

Normal corneas exclusively expressed sensory nerves that entered the stroma as large nerve stalks, branched to form a plexus at the epithelial/stromal interface, and extended termini into the epithelium. These nerves completely retracted from the infected cornea and were replaced by sympathetic nerves that sprouted extensively to hyperinnervate the corneal stroma but failed to form a plexus or extend termini into the epithelium. The hyperinnervating nerves expressed the sympathetic nerve marker TH and their invasion was blocked by performing SCGx. Moreover, the corneal opacity and neovascularization that normally characterizes HSK in this mouse model were largely abrogated by SCGx. Sensory nerves reinnervated infected corneas following SCGx, reformed a nerve plexus, and extended termini into the epithelium resulting in recovery of corneal sensitivity.

Conclusions

Sympathetic nerves have a central role in HSK in mice, preventing reinnervation by sensory nerves and promoting severe and persistent corneal inflammation.

Identifying the Palisades of Vogt in Human Ex Vivo Tissue

PURPOSE

The Palisades of Vogt (POV) constitute the corneal epithelial stem cell niche, but identification of this region in ex vivo tissue is difficult. Here we introduce a simple, direct method of identifying the POV in unsectioned, ex vivo human tissue.

METHODS

Twenty-two eyes were studied, four whole and eighteen rims. Orientation of whole eyes was determined and the eyes were marked to maintain their cardinal orientation prior to dissection. Samples were imaged with brightfield, linearly polarized light and transmitted circularly polarized light (CPL), and optical coherence tomography (OCT) volumes were acquired in all twelve clock hrs around the limbus. Five samples were also fluorescently labeled to identify the epithelial basement membrane, and whole mounts were imaged with laser scanning confocal microscopy. Images were compared to confirm that the structures visible with polarized light were POV.

RESULTS

Under CPL the POV presented as amber radial ridges visible in the superior and inferior regions of the tissue. Identification of POV was confirmed by correlating the structures seen under CPL, OCT and laser-scanning confocal microscopy.

CONCLUSIONS

CPL can be used to quickly identify POV regions in donor tissue. This technique can assist in targeted harvesting of stem cell regions for research and tissue for limbal transplant.

The Palisades of Vogt in Congenital Corneal Opacification (An American Ophthalmological Society Thesis)

PURPOSE

The purposes of this study are first, to determine if the palisades of Vogt (POV) are present or absent in cases of congenital corneal opacification (CCO) by using spectral domain ocular coherence tomography (SD-OCT), and second, in those cases already undergoing penetrating keratoplasty (PKP), to see whether the absence or presence of POV corresponds to re-epithelialization following transplant.

METHODS

This was a retrospective case review of 20 eyes (10 normal, 10 with CCO) evaluated with SD-OCT. The operator was masked to the clinician's assessment of the ocular surface. In those cases where the decision to perform PKP had already been made, the correlation between POV presence or absence and posttransplant graft epithelialization was determined.

RESULTS

All cases were imaged without adverse event. Nine eyes showed some evidence of POV and corresponding vasculature. Eight of 10 affected eyes underwent PKP, and subsequently 7 eyes epithelialized and 2 showed some peripheral neovascularization. The one eye that showed no signs of POV was the one that failed to epithelialize. All control subjects had consistent and regular POV.

CONCLUSIONS

Congenital corneal opacification is rare, and this study shows that at least some POV are present in the majority of cases of CCO. However, the palisades may not be entirely normal compared to age-matched controls. When there was absence of POV in a case of CCO, there was immediate and complete failure of epithelialization.

Congenital aniridia: etiology, manifestations and management

Congenital aniridia manifests as total or partial absence of the iris caused most commonly by mutations in PAX6, FOXC1, PITX2, and CYP1B1. Recently two new genes, FOXD3 and TRIM44, have also been implicated in isolated studies. We discuss the genotype-phenotype correlations for the main implicated genes. Classic aniridia is a panocular condition, which includes aniridia, cataract, corneal pannus, foveal, and optic nerve hypoplasia associated with mutations in the PAX6 gene. Classical aniridia is due to PAX6 mutations, while other genes contribute to aniridia-like phenotypes. We review the challenges involved in the management of aniridia, and discuss various surgical interventions. The clinical importance of defining the genotype in cases of congenital aniridia has become acutely apparent with the advent of possible therapies for classical aniridia, which are discussed.

Polarization microscopy for characterizing fiber orientation of ocular tissues

Characterizing the collagen fiber orientation and organization in the eye is necessary for a complete understanding of ocular biomechanics. In this study, we assess the performance of polarized light microscopy to determine collagen fiber orientation of ocular tissues. Our results demonstrate that the method provides objective, accurate, repeatable and robust data on fiber orientation with µm-scale resolution over a broad, cm-scale, field of view, unaffected by formalin fixation, without requiring tissue dehydration, labeling or staining. Together, this shows that polarized light microscopy is a powerful method for studying collagen architecture in the eye, with applications ranging from normal physiology and aging, to pathology and transplantation.

Human limbal biopsy-derived stromal stem cells prevent corneal scarring

Conventional allograft therapy for corneal scarring is widespread and successful, but donor tissue is not universally available, and some grafts fail owing to rejection and complications such as endothelial failure. We investigated direct treatment of corneal scarring using autologous stem cells, a therapy that, if successful, could reduce the need for corneal grafts. Mesenchymal cells were expanded from small superficial, clinically replicable limbal biopsies of human cadaveric corneo-scleral rims. Limbal biopsy-derived stromal cells (LBSCs) expanded rapidly in media containing human serum, were highly clonogenic, and could generate spheres expressing stem cell genes (ABCG2, Nestin, NGFR, Oct4, PAX6, and Sox2). Human LBSCs differentiated into keratocytes expressing characteristic marker genes (ALDH3A1, AQP1, KERA, and PTGDS) and organized a thick lamellar stroma-like tissue containing aligned collagen and keratan sulfate proteoglycans when cultured on aligned nanofiber substrata. When engrafted into mouse corneal wounds, LBSCs prevented formation of light-scattering scar tissue containing fibrotic matrix components. The presence of LBSCs induced regeneration of ablated stroma with tissue exhibiting lamellar structure and collagen organization indistinguishable from that of native tissue. Because the limbus can be easily biopsied from either eye of an affected individual and LBSCs capable of corneal stromal remodeling can be expanded under xeno-free autologous conditions, these cells present a potential for autologous stem cell-based treatment of corneal stromal blindness.

Dental pulp stem cells: a new cellular resource for corneal stromal regeneration

Corneal blindness afflicts millions of individuals worldwide and is currently treated by grafting with cadaveric tissues; however, there are worldwide donor tissue shortages, and many allogeneic grafts are eventually rejected. Autologous stem cells present a prospect for personalized regenerative medicine and an alternative to cadaveric tissue grafts. Dental pulp contains a population of adult stem cells and, similar to corneal stroma, develops embryonically from the cranial neural crest. We report that adult dental pulp cells (DPCs) isolated from third molars have the capability to differentiate into keratocytes, cells of the corneal stoma. After inducing differentiation in vitro, DPCs expressed molecules characteristic of keratocytes, keratocan, and keratan sulfate proteoglycans at both the gene and the protein levels. DPCs cultured on aligned nanofiber substrates generated tissue-engineered, corneal stromal-like constructs, recapitulating the tightly packed, aligned, parallel fibrillar collagen of native stromal tissue. After injection in vivo into mouse corneal stroma, human DPCs produced corneal stromal extracellular matrix containing human type I collagen and keratocan and did not affect corneal transparency or induce immunological rejection. These findings demonstrate a potential for the clinical application of DPCs in cellular or tissue engineering therapies for corneal stromal blindness.

In vitro expansion of corneal endothelial cells on biomimetic substrates

Corneal endothelial (CE) cells do not divide in vivo, leading to edema, corneal clouding and vision loss when the density drops below a critical level. The endothelium can be replaced by transplanting allogeneic tissue; however, access to donated tissue is limited worldwide resulting in critical need for new sources of corneal grafts. In vitro expansion of CE cells is a potential solution, but is challenging due to limited proliferation and loss of phenotype in vitro via endothelial to mesenchymal transformation (EMT) and senescence. We hypothesized that a bioengineered substrate recapitulating chemo-mechanical properties of Descemet's membrane would improve the in vitro expansion of CE cells while maintaining phenotype. Results show that bovine CE cells cultured on a polydimethylsiloxane surface with elastic modulus of 50 kPa and collagen IV coating achieved >3000-fold expansion. Cells grew in higher-density monolayers with polygonal morphology and ZO-1 localization at cell-cell junctions in contrast to control cells on polystyrene that lost these phenotypic markers coupled with increased α-smooth muscle actin expression and fibronectin fibril assembly. In total, these results demonstrate that a biomimetic substrate presenting native basement membrane ECM proteins and mechanical environment may be a key element in bioengineering functional CE layers for potential therapeutic applications.

Processing of spatial-frequency altered faces in schizophrenia: effects of illness phase and duration

Low spatial frequency (SF) processing has been shown to be impaired in people with schizophrenia, but it is not clear how this varies with clinical state or illness chronicity. We compared schizophrenia patients (SCZ, n = 34), first episode psychosis patients (FEP, n = 22), and healthy controls (CON, n = 35) on a gender/facial discrimination task. Images were either unaltered (broadband spatial frequency, BSF), or had high or low SF information removed (LSF and HSF conditions, respectively). The task was performed at hospital admission and discharge for patients, and at corresponding time points for controls. Groups were matched on visual acuity. At admission, compared to their BSF performance, each group was significantly worse with low SF stimuli, and most impaired with high SF stimuli. The level of impairment at each SF did not depend on group. At discharge, the SCZ group performed more poorly in the LSF condition than the other groups, and showed the greatest degree of performance decline collapsed over HSF and LSF conditions, although the latter finding was not significant when controlling for visual acuity. Performance did not change significantly over time for any group. HSF processing was strongly related to visual acuity at both time points for all groups. We conclude the following: 1) SF processing abilities in schizophrenia are relatively stable across clinical state; 2) face processing abnormalities in SCZ are not secondary to problems processing specific SFs, but are due to other known difficulties constructing visual representations from degraded information; and 3) the relationship between HSF processing and visual acuity, along with known SCZ- and medication-related acuity reductions, and the elimination of a SCZ-related impairment after controlling for visual acuity in this study, all raise the possibility that some prior findings of impaired perception in SCZ may be secondary to acuity reductions.

A laser-induced mouse model with long-term intraocular pressure elevation

Purpose

To develop and characterize a mouse model with intraocular pressure (IOP) elevation after laser photocoagulation on the trabecular meshwork (TM), which may serve as a model to investigate the potential of stem cell-based therapies for glaucoma.

Methods

IOP was measured in 281 adult C57BL/6 mice to determine normal IOP range. IOP elevation was induced unilaterally in 50 adult mice, by targeting the TM through the limbus with a 532-nm diode laser. IOP was measured up to 24 weeks post-treatment. The optic nerve damage was detected by electroretinography and assessed by semiautomatic counting of optic nerve axons. Effects of laser treatment on the TM were evaluated by histology, immunofluorescence staining, optical coherence tomography (OCT) and transmission electron microscopy (TEM).

Results

The average IOP of C57BL/6 mice was 14.5±2.6 mmHg (Mean ±SD). After laser treatment, IOP averaged above 20 mmHg throughout the follow-up period of 24 weeks. At 24 weeks, 57% of treated eyes had elevated IOP with the mean IOP of 22.5±2.5 mmHg (Mean ±SED). The difference of average axon count (59.0%) between laser treated and untreated eyes was statistically significant. Photopic negative response (PhNR) by electroretinography was significantly decreased. CD45+ inflammatory cells invaded the TM within 1 week. The expression of SPARC was increased in the TM from 1 to 12 weeks. Histology showed the anterior chamber angle open after laser treatment. OCT indicated that most of the eyes with laser treatment had no synechia in the anterior chamber angles. TEM demonstrated disorganized and compacted extracellular matrix in the TM.

Conclusions

An experimental murine ocular hypertension model with an open angle and optic nerve axon loss was produced with laser photocoagulation, which could be used to investigate stem cell-based therapies for restoration of the outflow pathway integrity for ocular hypertension or glaucoma.

Application of Elliptic Fourier analysis to describe the lamina cribrosa shape with age and intraocular pressure

The lamina cribrosa (LC) plays an important biomechanical role in the optic nerve head (ONH). We developed a statistical shape model of the LC and tested if the shape varies with age or IOP. The ONHs of 18 donor eyes (47-91 years, mean 76 years) fixed at either 5 or 50 mmHg of IOP were sectioned, stained, and imaged under a microscope. A 3D model of each ONH was reconstructed and the outline of the vertical sagittal section closest to the geometric center of the LC extracted. The outline shape was described using Elliptic Fourier analysis, and principal components analysis (PCA) employed to identify the primary modes of LC shape variation. Linear mixed effect models were used to determine if the shape measurements were associated with age or IOP. The analysis revealed several modes of shape variation: thickness and depth directly (PC 1), or inversely (PC 2) related, and superior-inferior asymmetry (PC 3). Only PC 3 was associated with IOP, with higher IOP correlating with greater curvature of the LC superiorly compared to inferiorly. Our analysis enabled a concise and complete characterization of LC shape, revealing variations without defining them a priori. No association between LC shape and age was found for the relatively old population studied. Superior-inferior asymmetry of LC shape was associated with IOP, with more asymmetry at higher IOP. Increased IOP was not associated with LC thickness or depth.

ABCB5 is a limbal stem cell gene required for corneal development and repair

Corneal epithelial homeostasis and regeneration are sustained by limbal stem cells (LSCs), and LSC deficiency is a major cause of blindness worldwide. Transplantation is often the only therapeutic option available to patients with LSC deficiency. However, while transplant success depends foremost on LSC frequency within grafts, a gene allowing for prospective LSC enrichment has not been identified so far. Here we show that ATP-binding cassette, sub-family B, member 5 (ABCB5) marks LSCs and is required for LSC maintenance, corneal development and repair. Furthermore, we demonstrate that prospectively isolated human or murine ABCB5-positive LSCs possess the exclusive capacity to fully restore the cornea upon grafting to LSC-deficient mice in xenogeneic or syngeneic transplantation models. ABCB5 is preferentially expressed on label-retaining LSCs in mice and p63α-positive LSCs in humans. Consistent with these findings, ABCB5-positive LSC frequency is reduced in LSC-deficient patients. Abcb5 loss of function in Abcb5 knockout mice causes depletion of quiescent LSCs due to enhanced proliferation and apoptosis, and results in defective corneal differentiation and wound healing. Our results from gene knockout studies, LSC tracing and transplantation models, as well as phenotypic and functional analyses of human biopsy specimens, provide converging lines of evidence that ABCB5 identifies mammalian LSCs. Identification and prospective isolation of molecularly defined LSCs with essential functions in corneal development and repair has important implications for the treatment of corneal disease, particularly corneal blindness due to LSC deficiency.

Mitochondrial Dynamics in Retinal Ganglion Cell Axon Regeneration and Growth Cone Guidance

Failed axon regeneration and retinal ganglion cell (RGC) death after trauma or disease, including glaucomatous and mitochondrial optic neuropathies, are increasingly linked to mitochondrial dysfunction. Mitochondria are highly dynamic organelles whose size, organization, and function are regulated by a balance between mitochondrial fission and fusion. Mitochondria are ubiquitous in axonal growth cones both in vitro and in vivo and during development and regeneration. However, the roles that mitochondrial fission and fusion dynamics play in the growth cone during axon regeneration are largely unstudied. Here we discuss recent data suggesting mitochondria in the distal axon and growth cone play a central role in axon growth by integrating intrinsic axon growth states with signaling from extrinsic cues. Mitochondrial fission and fusion are intrinsically regulated in the distal axon in the growth cones of acutely purified embryonic and postnatal RGCs with differing intrinsic axon growth potentials. These differences in fission and fusion correlate with differences in mitochondrial bioenergetics; embryonic RGCs with high intrinsic axon growth potential rely more on glycolysis whereas RGCs with low intrinsic axon growth potential rely more on oxidative phosphorylation. Mitochondrial fission and fusion are also differentially modulated by KLFs that either promote or suppress intrinsic axon growth, and altering the balance between mitochondrial fission and fusion can differentially regulate axon growth rate and growth cone guidance responses to both inhibitory and permissive guidance cues.

Azithromycin treatment increases survival of high-risk corneal allotransplants

PURPOSE

To test the therapeutic efficacy of azithromycin (AZM), a macrolide antibiotic for prolonging murine "high-risk" corneal allograft survival.

METHODS

Fully major histocompatibility complex-mismatched corneas were transplanted from C57BL/6 donors to BALB/c recipients with suture-induced vascularized high-risk corneal beds. Recipient mice were either not treated or treated with topical AZM, oral AZM, or both. Evaluation of graft vascularization and clarity was performed in a masked fashion. Lymph nodes were excised and analyzed for CD4, FoxP3, and CD44 by flow cytometry, and for T-cell priming by proliferation and cytokine production in mixed lymphocyte cultures. Corneal whole mounts were evaluated by confocal microscopy.

RESULTS

The incidence of graft rejection in the control group (81.8%) was significantly reduced by AZM treatment (18.2% topical, 21.7% oral, 33.3% topical + oral), although corneal vascularization was not affected by the treatment. The frequency of corneas that retained complete clarity after transplantation was higher in the AZM-treated groups. Reduced graft rejection in the AZM-treated groups was not associated with a reduced allospecific T-cell response or increased frequency of regulatory T cells.

CONCLUSIONS

AZM is effective in prolonging survival of high-risk corneal allografts by an as yet undefined mechanism that does not seem to involve modulation of corneal neovascularization or allospecific T-cell priming.

Patients with cystic fibrosis have inducible IL-17+IL-22+ memory cells in lung draining lymph nodes

BACKGROUND

IL-17 is an important cytokine signature of the TH differentiation pathway TH17. This T-cell subset is crucial in mediating autoimmune disease or antimicrobial immunity in animal models, but its presence and role in human disease remain to be completely characterized.

OBJECTIVE

We set out to determine the frequency of TH17 cells in patients with cystic fibrosis (CF), a disease in which there is recurrent infection with known pathogens.

METHODS

Explanted lungs from patients undergoing transplantation or organ donors (CF samples=18; non-CF, nonbronchiectatic samples=10) were collected. Hilar nodes and parenchymal lung tissue were processed and examined for TH17 signature by using immunofluorescence and quantitative real-time PCR. T cells were isolated and stimulated with antigens from Pseudomonas aeruginosa and Aspergillus species. Cytokine profiles and staining with flow cytometry were used to assess the reactivity of these cells to antigen stimulation.

RESULTS

We found a strong IL-17 phenotype in patients with CF compared with that seen in control subjects without CF. Within this tissue, we found pathogenic antigen-responsive CD4+IL-17+ cells. There were double-positive IL-17+IL-22+ cells [TH17(22)], and the IL-22+ population had a higher proportion of memory characteristics. Antigen-specific TH17 responses were stronger in the draining lymph nodes compared with those seen in matched parenchymal lungs.

CONCLUSION

Inducible proliferation of TH17(22) with memory cell characteristics is seen in the lungs of patients with CF. The function of these individual subpopulations will require further study regarding their development. T cells are likely not the exclusive producers of IL-17 and IL-22, and this will require further characterization.

Antitumor effects of EGFR antisense guanidine-based peptide nucleic acids in cancer models

Peptide nucleic acids have emerged over the past two decades as a promising class of nucleic acid mimics because of their strong binding affinity and sequence selectivity toward DNA and RNA, and resistance to enzymatic degradation by proteases and nucleases. While they have been shown to be effective in regulation of gene expression in vitro, and to a small extent in vivo, their full potential for molecular therapy has not yet been fully realized due to poor cellular uptake. Herein, we report the development of cell-permeable, guanidine-based peptide nucleic acids targeting the epidermal growth factor receptor (EGFR) in preclinical models as therapeutic modality for head and neck squamous cell carcinoma (HNSCC) and nonsmall cell lung cancer (NSCLC). A GPNA oligomer, 16 nucleotides in length, designed to bind to EGFR gene transcript elicited potent antisense effects in HNSCC and NSCLC cells in preclinical models. When administered intraperitoneally in mice, EGFRAS-GPNA was taken-up by several tissues including the xenograft tumor. Systemic administration of EGFRAS-GPNA induced antitumor effects in HNSCC xenografts, with similar efficacies as the FDA-approved EGFR inhibitors: cetuximab and erlotinib. In addition to targeting wild-type EGFR, EGFRAS-GPNA is effective against the constitutively active EGFR vIII mutant implicated in cetuximab resistance. Our data reveals that GPNA is just as effective as a molecular platform for treating cetuximab resistant cells, demonstrating its utility in the treatment of cancer.

Klf4 regulates the expression of Slurp1, which functions as an immunomodulatory peptide in the mouse cornea

PURPOSE

The secreted Ly6/uPAR-related protein-1 (Slurp1), associated with the hyperkeratotic disorder mal de Meleda, is abundantly expressed in corneas. Here, we examine its corneal expression and functions.

METHODS

Gene expression was quantified by quantitative PCR (qPCR), immunoblots, and immunofluorescent staining. Effect of Kruppel-like factor 4 (Klf4) on Slurp1 promoter was evaluated by chromatin immunoprecipitation (ChIP) and transient transfections. Adenoviral vectors were used to express Slurp1 in corneas. Leukocytic infiltration in bacterial lipopolysaccharide (LPS)-, herpes simplex virus type 1 (HSV-1)-, or adenovirus (serotype 5)-treated mouse corneas was characterized by flow cytometry.

RESULTS

Corneal expression of Slurp1 increased sharply upon mouse eyelid opening, concurrent with the elevated expression of Klf4. Slurp1 was significantly decreased in Klf4 conditional null (Klf4CN) corneas that displayed elevated expression of cytokines and cytokine receptors, as well as neutrophil influx consistent with a proinflammatory environment. In additional models of corneal inflammation, Slurp1 expression was abrogated within 24 hours of LPS injection or HSV-1 or adenoviral infection, accompanied by a predominantly neutrophilic infiltrate. Neutrophilic infiltration was enhanced in HSV-1-infected Klf4CN corneas lacking Slurp1. SLURP1 promoter activity was stimulated by KLF4, suppressed by IL-4, IL-13, and TNFα, and unperturbed by IFN-γ. Slurp1 downregulation and neutrophil influx were comparable in HSV-1-infected wild-type (WT) and Ifng-/- mouse corneas. Mouse corneas infected with Slurp1-expressing adenoviral vectors displayed reduced signs of inflammation and restricted neutrophilic infiltration compared with those infected with control vectors.

CONCLUSIONS

Klf4 regulates the expression of Slurp1, a key immunomodulatory peptide that is abundantly expressed in healthy corneas and is downregulated in proinflammatory conditions.

Human lamina cribrosa insertion and age

PURPOSE

To test the hypothesis that in healthy human eyes the lamina cribrosa (LC) insertion into the pia mater increases with age.

METHODS

The optic nerve heads (ONHs) of donor eyes fixed at either 5 or 50 mm Hg of IOP were sectioned, stained, and imaged under bright- and dark-field conditions. A 3-dimensional (3D) model of each ONH was reconstructed. From the 3D models we measured the area of LC insertion into the peripapillary scleral flange and into the pia, and computed the total area of insertion and fraction of LC inserting into the pia. Linear mixed effect models were used to determine if the measurements were associated with age or IOP.

RESULTS

We analyzed 21 eyes from 11 individuals between 47 and 91 years old. The LC inserted into the pia in all eyes. The fraction of LC inserting into the pia (2.2%-29.6%) had a significant decrease with age (P = 0.049), which resulted from a nonsignificant increase in the total area of LC insertion (P = 0.41) and a nonsignificant decrease in the area of LC insertion into the pia (P = 0.55). None of the measures was associated with fixation IOP (P values 0.44-0.81). Differences between fellow eyes were smaller than differences between unrelated eyes.

CONCLUSIONS

The LC insertion into the pia mater is common in middle-aged and older eyes, and does not increase with age. The biomechanical and vascular implications of the LC insertion into the pia mater are not well understood and should be investigated further.

Critical role of Klf5 in regulating gene expression during post-eyelid opening maturation of mouse corneas

BACKGROUND

Klf5 plays an important role in maturation and maintenance of the mouse ocular surface. Here, we quantify WT and Klf5-conditional null (Klf5CN) corneal gene expression, identify Klf5-target genes and compare them with the previously identified Klf4-target genes to understand the molecular basis for non-redundant functions of Klf4 and Klf5 in the cornea.

METHODOLOGY/PRINCIPAL FINDINGS

Postnatal day-11 (PN11) and PN56 WT and Klf5CN corneal transcriptomes were quantified by microarrays to compare gene expression in maturing WT corneas, identify Klf5-target genes, and compare corneal Klf4- and Klf5-target genes. Whole-mount corneal immunofluorescent staining was employed to examine CD45+ cell influx and neovascularization. Effect of Klf5 on expression of desmosomal components was studied by immunofluorescent staining and transient co-transfection assays. Expression of 714 and 753 genes was increased, and 299 and 210 genes decreased in PN11 and PN56 Klf5CN corneas, respectively, with 366 concordant increases and 72 concordant decreases. PN56 Klf5CN corneas shared 241 increases and 98 decreases with those previously described in Klf4CN corneas. Xenobiotic metabolism related pathways were enriched among genes decreased in Klf5CN corneas. Expression of angiogenesis and immune response-related genes was elevated, consistent with neovascularization and CD45+ cell influx in Klf5CN corneas. Expression of 1574 genes was increased and 1915 genes decreased in WT PN56 compared with PN11 corneas. Expression of ECM-associated genes decreased, while that of solute carrier family members increased in WT PN56 compared with PN11 corneas. Dsg1a, Dsg1b and Dsp were down-regulated in Klf5CN corneas and their corresponding promoter activities were stimulated by Klf5 in transient co-transfection assays.

CONCLUSIONS/SIGNIFICANCE

Differences between PN11 and PN56 corneal Klf5-target genes reveal dynamic changes in functions of Klf5 during corneal maturation. Klf5 contributes to corneal epithelial homeostasis by regulating the expression of desmosomal components. Klf4- and Klf5-target genes are largely distinct, consistent with their non-redundant roles in the mouse cornea.

Quantitative assessment of ultrastructure and light scatter in mouse corneal debridement wounds

PURPOSE

The mouse has become an important wound healing model with which to study corneal fibrosis, a frequent complication of refractive surgery. The aim of the current study was to quantify changes in stromal ultrastructure and light scatter that characterize fibrosis in mouse corneal debridement wounds.

METHODS

Epithelial debridement wounds, with and without removal of basement membrane, were produced in C57BL/6 mice. Corneal opacity was measured using optical coherence tomography, and collagen diameter and matrix order were quantified by x-ray scattering. Electron microscopy was used to visualize proteoglycans. Quantitative PCR (Q-PCR) measured mRNA transcript levels for several quiescent and fibrotic markers.

RESULTS

Epithelial debridement without basement membrane disruption produced a significant increase in matrix disorder at 8 weeks, but minimal corneal opacity. In contrast, basement membrane penetration led to increases in light scatter, matrix disorder, and collagen diameter, accompanied by the appearance of abnormally large proteoglycans in the subepithelial stroma. This group also demonstrated upregulation of several quiescent and fibrotic markers 2 to 4 weeks after wounding.

CONCLUSIONS

Fibrotic corneal wound healing in mice involves extensive changes to collagen and proteoglycan ultrastructure, consistent with deposition of opaque scar tissue. Epithelial basement membrane penetration is a deciding factor determining the degree of ultrastructural changes and resulting opacity.

Optical coherence tomography as a rapid, accurate, noncontact method of visualizing the palisades of Vogt

PURPOSE

This study explored the efficacy of optical coherence tomography (OCT) as a high-resolution, noncontact method for imaging the palisades of Vogt by correlating OCT and confocal microscopy images.

METHODS

Human limbal rims were acquired and imaged with OCT and confocal microscopy. The area of the epithelial basement membrane in each of these sets was digitally reconstructed, and the models were compared.

RESULTS

OCT identified the palisades within the limbus and exhibited excellent structural correlation with immunostained tissue imaged by confocal microscopy.

CONCLUSIONS

OCT successfully identified the limbal palisades of Vogt that constitute the corneal epithelial stem cell niche. These findings offer the exciting potential to characterize the architecture of the palisades in vivo, to harvest stem cells for transplantation more accurately, to track palisade structure for better diagnosis, follow-up and staging of treatment, and to assess and intervene in the progression of stem cell depletion by monitoring changes in the structure of the palisades.

Recurrent enterococcal endophthalmitis seeded by an intraocular lens biofilm

A case of endophthalmitis following uneventful phacoemulsification and posterior chamber intraocular lens (IOL) implantation in a 77-year-old diabetic man was culture-positive for Enterococcus faecalis. After successful treatment with intravitreal, topical, and systemic antibiotic agents, the infection seemed to clear and the patient achieved a corrected visual acuity of 20/25. Four months after the initial presentation, the patient again developed signs and symptoms of endophthalmitis, with regrowth of E faecalis. The antibiotic therapy was repeated. One month later, the IOL was removed surgically and found to harbor a biofilm of the strain demonstrated by DNA analysis. The microbiologic and DNA analyses support that a biofilm on an IOL could be a vector for a cause of recurrent endophthalmitis. Intraocular lens exchange in cases of postoperative endophthalmitis caused by E faecalis may be considered to decrease the risk for recurrent infection.

Ligand-independent antiapoptotic function of estrogen receptor-beta in lung cancer cells

Recent studies have demonstrated the presence of estrogen receptor (ER)beta in the mitochondria in various cell types and tissues, but the exact function of this localization remains unclear. In this study, we have examined the function of mitochondrial ERbeta in non-small-cell lung cancer (NSCLC) cells. Down-regulation of ERbeta by short hairpin RNA constructs sensitized NSCLC cells to various apoptosis-inducing agents such as cisplatin, taxol, and etoposide. The increased growth inhibition and induction of apoptosis in ERbeta-knockdown cells was observed irrespective of estrogen treatment, suggesting a ligand-independent role of ERbeta in regulating the intrinsic apoptotic pathway. Further, ERbeta from the mitochondrial fraction physically interacted with the proapoptotic protein Bad, in a ligand-independent manner. Glutathione-S-transferase pull-down assays and molecular modeling studies revealed that the DNA-binding domain and hinge region of ERbeta, and the BH3 domain of Bad were involved in these interactions. Further investigations revealed that ERbeta inhibited Bad function by disrupting Bad-Bcl-X(L) and Bad-Bcl-2 interactions. Reintroduction of ERbeta in the mitochondria of ERbeta knockdown cells reversed their sensitivity to cisplatin. Overall, our results demonstrate a ligand-independent role of ERbeta in regulating apoptosis, revealing a novel function for ERbeta in the mitochondria.

Increased fusiform area activation in schizophrenia during processing of spatial frequency-degraded faces, as revealed by fMRI

BACKGROUND

People with schizophrenia demonstrate perceptual organization impairments, and these are thought to contribute to their face processing difficulties.

METHOD

We examined the neural substrates of emotionally neutral face processing in schizophrenia by investigating neural activity under three stimulus conditions: faces characterized by the full spectrum of spatial frequencies, faces with low spatial frequency information removed [high spatial frequency (HSF) condition], and faces with high spatial frequency information removed [low spatial frequency (LSF) condition]. Face perception in the HSF condition is more reliant on local feature processing whereas perception in the LSF condition requires greater reliance on global form processing. Past studies of perceptual organization in schizophrenia indicate that patients perform relatively more poorly with degraded stimuli but also that, when global information is absent, patients may perform better than controls because of their relatively increased ability to initially process individual features. Therefore, we hypothesized that people with schizophrenia (n=14) would demonstrate greater face processing difficulties than controls (n=13) in the LSF condition, whereas they would demonstrate a smaller difference or superior performance in the HSF condition.

RESULTS

In a gender-discrimination task, behavioral data indicated high levels of accuracy for both groups, with a trend toward an interaction involving higher patient performance in the HSF condition and poorer patient performance in the LSF condition. Patients demonstrated greater activity in the fusiform gyrus compared to controls in both degraded conditions.

CONCLUSIONS

These data suggest that impairments in basic integration abilities may be compensated for by relatively increased activity in this region.

Free edges in epithelial cell sheets stimulate epidermal growth factor receptor signaling

Epithelia tend to migrate when edges are present, for instance, after wounding or during development. Using a new tissue culture model, we found that the existence of free edges is in itself a signal that causes activation of the epidermal growth factor and cell motility.

The ability of epithelia to migrate and cover wounds is essential to maintaining their functions as physical barriers. Wounding induces many cues that may affect the transition to motility, including the immediate mechanical perturbation, release of material from broken cells, new interactions with adjacent extracellular matrix, and breakdown of physical separation of ligands from their receptors. Depending on the exact nature of wounds, some cues may be present only transiently or insignificantly. In many epithelia, activation of the epidermal growth factor receptor (EGFR) is a central event in induction of motility, and we find that its continuous activation is required for progression of healing of wounds in sheets of corneal epithelial cells. Here, we examine the hypothesis that edges, which are universally and continuously present in wounds, are a cue. Using a novel culture model we find that their presence is sufficient to cause activation of the EGFR and increased motility of cells in the absence of other cues. Edges that are bordered by agarose do not induce activation of the EGFR, indicating that activation is not due to loss of any specific type of cell–cell interaction but rather due to loss of physical constraints.

Activated CD11b+ CD15+ granulocytes increase in the blood of patients with uveal melanoma

PURPOSE

To determine whether activated CD11b(+) CD15(+) granulocytes increase in the blood of patients with uveal melanoma.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation from the blood of patients with primary choroidal/ciliochoroidal uveal melanomas (six women, four men; age range, 46-91 years) and healthy control donors (14 women, 10 men; age range, 50-81 years). The expression of CD15 and CD68 on CD11b(+) myeloid cells within PBMCs and primary uveal melanomas was evaluated by flow cytometry. CD3zeta chain expression by CD3epsilon(+) T cells in PBMCs and within primary uveal melanomas was measured as an indirect indication of T-cell function.

RESULTS

The percentage of CD11b(+) cells in PBMCs of patients with uveal melanoma increased 1.8-fold in comparison to healthy donors and comprised three subsets: CD68 negative CD15(+) granulocytes, which increased 4.1-fold; CD68(-) CD15(-) cells, which increased threefold; and CD68(+) CD15(low) cells, which were unchanged. A significant (2.7-fold) reduction in CD3zeta chain expression on CD3epsilon(+) T cells, a marker of T-cell dysfunction, was observed in PBMCs of patients with uveal melanoma in comparison with healthy control subjects and correlated significantly with the percentage of CD11b(+) cells in PBMCs. CD3zeta chain expression on T cells within primary tumors was equivalent to CD3zeta expression in PBMCs of the same patient in four of five patients analyzed.

CONCLUSIONS

Activated CD11b(+) CD15(+) granulocytes expand in the blood of patients with uveal melanoma and may contribute to immune evasion by ocular tumors by inhibiting T-cell function via decreasing CD3zeta chain expression.

Synthesis of conformationally preorganized and cell-permeable guanidine-based gamma-peptide nucleic acids (gammaGPNAs)

A general method for preparing optically pure guanidine-based gamma-peptide nucleic acid (gammaGPNA) monomers for all four natural nucleobases (A, C, G, and T) is described. These second-generation gammaGPNAs differ from the first-generation GPNAs in that the guanidinium group is installed at the gamma- instead of the alpha-position of the N-(2-aminoethyl)glycine backbone unit. This positional switch enables GPNAs to be synthesized from relatively cheap L- as opposed to D-amino acids. Unlike their alpha-predecessors, which are randomly folded, gammaGPNAs prepared from L-amino acids are preorganized into a right-handed helix and bind to DNA and RNA with exceptionally high affinity and sequence selectivity and are readily taken up by mammalian cells.

Estrogen receptor beta functions through nongenomic mechanisms in lung cancer cells

Recent studies have shown that estrogens promote the growth of lung cancer cells and may potentially be responsible for increased susceptibility to lung cancer in women. These observations raise the possibility of using antiestrogens in treating and preventing lung cancer. However, it is not clear how estrogen receptors (ERs) modulate the growth of non-small cell lung cancer (NSCLC) cells. Our Western blotting and real-time PCR analysis showed that NSCLC cells expressed ERbeta, but not ERalpha. In addition, ERbeta-specific ligands, but not ERalpha-specific ligands, promoted the growth of lung cancer cells. Furthermore, knockdown of ERbeta by short hairpin RNA constructs resulted in loss of estrogen-dependent growth of lung cancer cells. Interestingly, endogenous ERbeta failed to transcriptionally activate estrogen response element (ERE)-luciferase constructs in NSCLC cells, suggesting a lack of genomic function. Upon further investigation, ERbeta was found to be in the cytoplasm in all lung cancer cells and failed to translocate to the nucleus in the presence of estrogen, as observed by biochemical, ArrayScan, and confocal microscopy experiments. Nonetheless, estrogen caused rapid activation of cAMP, Akt, and MAPK signaling pathways in lung cancer cells. Immunohistochemical analysis of lung tumor biopsies showed strong ERbeta staining in the cytoplasm, whereas no staining was observed for ERalpha. In conclusion, our results suggest that that proliferative effects of estrogen in lung cancer cells is mediated primarily, if not exclusively, by the nongenomic action of ERbeta.

Hepatocyte growth factor inhibits epithelial to myofibroblast transition in lung cells via Smad7

Idiopathic pulmonary fibrosis is a lethal parenchymal lung disease characterized by denudation of the lung epithelium, fibroblast proliferation, and collagen deposition. Cellular changes underlying disease progression involve injury to alveolar epithelial cells, epithelial to mesenchymal transition, proliferation of alpha-smooth muscle actin (alpha-SMA)-expressing myofibroblasts and of fibroblasts resulting in enhanced deposition of extracellular matrix proteins. Hepatocyte growth factor (HGF) inhibits progression of bleomycin-induced pulmonary fibrosis in mice. The mechanism underlying the inhibitory effect of HGF was investigated in an in vitro model. We show that HGF markedly antagonizes basal and transforming growth factor (TGF)-beta-induced expression of myofibroblast markers such as alpha-SMA, collagen type 1, and fibronectin in rat alveolar epithelial cells. HGF also inhibited TGF-beta-induced alpha-SMA expression in primary murine alveolar epithelial cells. Since TGF-beta is known to regulate alpha-SMA expression, the effect of HGF on components of TGF-beta signaling was investigated. HGF induced expression of Smad7, an inhibitor of TGF-beta signaling, in a mitogen-activated protein kinase-dependent manner. HGF also induced the nuclear export of Smad7 and Smad ubiquitin regulatory factor 1 (Smurf1) to the cytoplasm. HGF-dependent decrease in alpha-SMA was abolished with specific siRNAs targeted to Smad7. Thus, induction of Smad7 by HGF serves to limit acquisition of the myofibroblast phenotype in alveolar epithelial cells.

The effect of probe placement and type of viscoelastic material on endoscopic cyclophotocoagulation laser energy transmission

BACKGROUND AND OBJECTIVE

Endoscopic cyclophotocoagulation is a laser modality used to treat refractory glaucoma through the ablation of ciliary epithelium on the ciliary processes, which results in reduced aqueous production. The purpose of this study was to investigate the effect of various viscoelastics and optimal probe positioning on endoscopic cyclophotocoagulation treatment.

MATERIALS AND METHODS

Six different viscoelastic materials and a balanced salt solution, which was used as a control, were evaluated by placing 2 mL of each in a separate 2 mL glass tube. Laser power was measured at six distances to represent clinical placement of the laser probe in relation to the ciliary processes.

RESULTS

The amount of energy measured with the probe at the bottom of the tube and 1 and 2 mm away was not statistically significantly different among the viscoelastic materials or the balanced salt solution. There was a gradual decrease in transmission of laser energy in all viscoelastics as the laser probe was moved farther away.

CONCLUSION

To preserve the intended laser energy setting, the optimal distance between the treated tissue and the laser probe is 2 mm.

A Serratia marcescens OxyR homolog mediates surface attachment and biofilm formation

OxyR is a conserved bacterial transcription factor with a regulatory role in oxidative stress response. From a genetic screen for genes that modulate biofilm formation in the opportunistic pathogen Serratia marcescens, mutations in an oxyR homolog and predicted fimbria structural genes were identified. S. marcescens oxyR mutants were severely impaired in biofilm formation, in contrast to the hyperbiofilm phenotype exhibited by oxyR mutants of Escherichia coli and Burkholderia pseudomallei. Further analysis revealed that OxyR plays a role in the primary attachment of cells to a surface. Similar to what is observed in other bacterial species, S. marcescens OxyR is required for oxidative stress resistance. Mutations in oxyR and type I fimbrial genes resulted in severe defects in fimbria-associated phenotypes, revealing roles in cell-cell and cell-biotic surface interactions. Transmission electron microscopy revealed the absence of fimbria-like surface structures on an OxyR-deficient strain and an enhanced fimbrial phenotype in strains bearing oxyR on a multicopy plasmid. The hyperfimbriated phenotype conferred by the multicopy oxyR plasmid was absent in a type I fimbrial mutant background. Real-time reverse transcriptase PCR indicated an absence of transcripts from a fimbrial operon in an oxyR mutant that were present in the wild type and a complemented oxyR mutant strain. Lastly, chromosomal P(lac)-mediated expression of fimABCD was sufficient to restore wild-type levels of yeast agglutination and biofilm formation to an oxyR mutant. Together, these data support a model in which OxyR contributes to early stages of S. marcescens biofilm formation by influencing fimbrial gene expression.