Clinical Utility of Spectral-Domain Optical Coherence Tomography Marker Disorganization of Retinal Inner Layers in Diabetic Retinopathy

BACKGROUND AND OBJECTIVE

Disorganization of retinal inner layers (DRIL) is a potential spectral-domain optical coherence tomography (SD-OCT) imaging biomarker with clinical utility in diabetic retinopathy (DR).

PATIENTS AND METHODS

A cross-sectional study was conducted at a large academic center. The cohort was composed of 1,175 patients with type 2 diabetes with and without retinopathy on initial examination between September 2009 and January 2019 (n = 2,083 eyes). DR risk and progression factors were obtained from the medical record. Trained graders masked to patients' clinical histories evaluated SD-OCT scans for DRIL.

RESULTS

Of 2,083 eyes, 28.1% (n = 585) demonstrated presence of DRIL with high interrater reliability (K = 0.88, 95% CI 0.86-0.90). DRIL was associated with worse visual acuity (VA) (P < 0.001) and DR severity (P < 0.0001). Insulin users had more severe DR (P < 0.0001). DR-related factors, race (Black, White) and sex (male) were significantly associated with DRIL (P < 0.05).

CONCLUSIONS

DRIL was strongly associated with DR severity and worse VA, supporting its utility as an unfavorable prognostic indicator. [Ophthalmic Surg Lasers Imaging Retina 2023;54:692-700.].

Deep Learning Algorithm Detects Presence of Disorganization of Retinal Inner Layers (DRIL)-An Early Imaging Biomarker in Diabetic Retinopathy

Purpose

To develop and train a deep learning-based algorithm for detecting disorganization of retinal inner layers (DRIL) on optical coherence tomography (OCT) to screen a cohort of patients with diabetic retinopathy (DR).

Methods

In this cross-sectional study, subjects over age 18, with ICD-9/10 diagnoses of type 2 diabetes with and without retinopathy and Cirrus HD-OCT imaging performed between January 2009 to September 2019 were included in this study. After inclusion and exclusion criteria were applied, a final total of 664 patients (5992 B-scans from 1201 eyes) were included for analysis. Five-line horizontal raster scans from Cirrus HD-OCT were obtained from the shared electronic health record. Two trained graders evaluated scans for presence of DRIL. A third physician grader arbitrated any disagreements. Of 5992 B-scans analyzed, 1397 scans (∼30%) demonstrated presence of DRIL. Graded scans were used to label training data for the convolution neural network (CNN) development and training.

Results

On a single CPU system, the best performing CNN training took ∼35 mins. Labeled data were divided 90:10 for internal training/validation and external testing purpose. With this training, our deep learning network was able to predict the presence of DRIL in new OCT scans with a high accuracy of 88.3%, specificity of 90.0%, sensitivity of 82.9%, and Matthews correlation coefficient of 0.7.

Conclusions

The present study demonstrates that a deep learning-based OCT classification algorithm can be used for rapid automated identification of DRIL. This developed tool can assist in screening for DRIL in both research and clinical decision-making settings.

Translational Relevance

A deep learning algorithm can detect disorganization of retinal inner layers in OCT scans.

Abstract 5646: Spatial transcriptomic profiling of the human and mouse retina prepared with CryoJane Tape Transfer System using GeoMx and CosMx spatial analysis

The goal of this study is to identify key transcriptomic markers within layers of the retina by individually profiling layers using cellular and subcellular spatial transcriptomics, additionally, comparing the results between each level. Both human and mouse retina samples, prepared fresh frozen and fixed frozen, are analyzed using the GeoMx® Digital Spatial Profiler (DSP) and CosMx® Spatial Molecular Imager (SMI) using the whole mouse transcriptome atlas and 1000-plex mouse neuro panel, respectively. Samples are fixed using Cryo-Jane Taper Transfer system. Samples are mounted on to adhesive coated slides as well as adhesive tape to mount samples to glass slides. This method is used to secure fragile frozen tissue, such as the retina. Human and mouse samples were stained using immunofluorescent microscopy targeting neurofilament H (NF-H), glial fibrillary acidic protein (GFAP) and NeuN on DSP and 18s rRNA, amyloid-beta and GFAP on SMI. Staining allows for identification of structural layers in the retina. Simultaneously, regions of interest (ROI) for spatial profiling are selected based on immunofluorescent stains. On DSP, each sample had 3x ROIs in the photoreceptor layer, inner nuclear layer and ganglion cell layer, then, oligonucleotides were collected and sequenced. Finally, raw counts were Q3 normalized for analysis. For SMI data analysis, 6 field of views (FOVs) were put on each section to cover most regions with multiple layers. ~8000 genes were detected on human retina samples using DSP. Around 500 unique genes were detected between the photoreceptor and inner nuclear layer using DSP. Preliminary SMI results show we were able to identify cell types (amacrine, horizontal cell, biopolar cell, ganglion cell, etc) and cell specific markers for outer nuclear layer, inner nuclear layer and ganglion cell layer. Data between DSP and SMI showed high concordance with one another, identifying many genes in each layer.

Citation Format: Charles Glaser, Su Ma, Wei Yang, Yan Liang, Joeseph Beechem, Vera L. Bonilha, Sujata Rao, William Horrigan, Bela Anand-Apte. Spatial transcriptomic profiling of the human and mouse retina prepared with CryoJane Tape Transfer System using GeoMx and CosMx spatial analysis. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5646.

Visual imaging as a predictor of neurodegeneration in experimental autoimmune demyelination and multiple sclerosis

Thalamic volume is associated with clinical disability in multiple sclerosis (MS) and is vulnerable to secondary neurodegeneration due to its extensive connectivity throughout the central nervous system (CNS). Using a model of autoimmune demyelination that exhibits CNS-infiltrating immune cells in both spinal cord white matter and optic nerve, we sought to evaluate neurodegenerative changes due to lesions affecting the spino- and retino-thalamic pathways. We found comparable axonal loss in spinal cord white matter and optic nerve during the acute phase of disease consistent with synaptic loss, but not neuronal cell body loss in the thalamic nuclei that receive input from these discrete pathways. Loss of spinal cord neurons or retinal ganglion cells retrograde to their respective axons was not observed until the chronic phase of disease, where optical coherence tomography (OCT) documented reduced inner retinal thickness. In patients with relapsing-remitting MS without a history of optic neuritis, OCT measures of inner retinal volume correlated with retino-thalamic (lateral geniculate nucleus) and spino-thalamic (ventral posterior nucleus) volume as well as neuroperformance measures. These data suggest retinal imaging may serve as an important noninvasive predictor of neurodegeneration in MS.

Extracellular matrix dysfunction in Sorsby patient-derived retinal pigment epithelium

Sorsby Fundus Dystrophy (SFD) is a rare form of macular degeneration that is clinically similar to age-related macular degeneration (AMD), and a histologic hallmark of SFD is a thick layer of extracellular deposits beneath the retinal pigment epithelium (RPE). Previous studies of SFD patient-induced pluripotent stem cell (iPSC) derived RPE differ as to whether these cultures recapitulate this key clinical feature by forming increased drusenoid deposits. The primary purpose of this study is to examine whether SFD patient-derived iPSC-RPE form basal deposits similar to what is found in affected family member SFD globes and to determine whether SFD iPSC RPE may be more oxidatively stressed. We performed a careful comparison of iPSC RPE from three control individuals, multiple iPSC clones from two SFD patients' iPSC RPE, and post-mortem eyes of affected SFD family members. We also examined the effect of CRISPR-Cas9 gene correction of the S204C TIMP3 mutation on RPE phenotype. Finally, targeted metabolomics with liquid chromatography and mass spectrometry analysis and stable isotope-labeled metabolite analysis were performed to determine whether SFD RPE are more oxidatively stressed. We found that SFD iPSC-RPE formed significantly more sub-RPE deposits (∼6-90 μm in height) compared to control RPE at 8 weeks. These deposits were similar in composition to the thick layer of sub-RPE deposits found in SFD family member globes by immunofluorescence staining and TEM imaging. S204C TIMP3 correction by CRISPR-Cas9 gene editing in SFD iPSC RPE cells resulted in significantly reduced basal laminar and sub-RPE calcium deposits. We detected a ∼18-fold increase in TIMP3 accumulation in the extracellular matrix (ECM) of SFD RPE, and targeted metabolomics showed that intracellular 4-hydroxyproline, a major breakdown product of collagen, is significantly elevated in SFD RPE, suggesting increased ECM turnover. Finally, SFD RPE cells have decreased intracellular reduced glutathione and were found to be more vulnerable to oxidative stress. Our findings suggest that elements of SFD pathology can be demonstrated in culture which may lead to insights into disease mechanisms.

3D iPSC modeling of the retinal pigment epithelium-choriocapillaris complex identifies factors involved in the pathology of macular degeneration

The retinal pigment epithelium (RPE)-choriocapillaris (CC) complex in the eye is compromised in age-related macular degeneration (AMD) and related macular dystrophies (MDs), yet in vitro models of RPE-CC complex that enable investigation of AMD/MD pathophysiology are lacking. By incorporating iPSC-derived cells into a hydrogel-based extracellular matrix, we developed a 3D RPE-CC model that recapitulates key features of both healthy and AMD/MD eyes and provides modular control over RPE and CC layers. Using this 3D RPE-CC model, we demonstrated that both RPE- and mesenchyme-secreted factors are necessary for the formation of fenestrated CC-like vasculature. Our data show that choroidal neovascularization (CNV) and CC atrophy occur in the absence of endothelial cell dysfunction and are not necessarily secondary to drusen deposits underneath RPE cells, and CC atrophy and/or CNV can be initiated systemically by patient serum or locally by mutant RPE-secreted factors. Finally, we identify FGF2 and matrix metalloproteinases as potential therapeutic targets for AMD/MDs.

The retinal pigment epithelium in Sorsby Fundus Dystrophy shows increased sensitivity to oxidative stress-induced degeneration

Sorsby Fundus Dystrophy (SFD) is a rare inherited autosomal dominant macular degeneration caused by specific mutations in TIMP3. Patients with SFD present with pathophysiology similar to the more common Age-related Macular Degeneration (AMD) and loss of vision due to both choroidal neovascularization and geographic atrophy. Previously, it has been shown that RPE degeneration in AMD is due in part to oxidative stress. We hypothesized that similar mechanisms may be at play in SFD. The objective of this study was to evaluate whether mice carrying the S179C-Timp3 mutation, a variant commonly observed in SFD, showed increased sensitivity to oxidative stress. Antioxidant genes are increased at baseline in the RPE in SFD mouse models, but not in the retina. This suggests the presence of a pro-oxidant environment in the RPE in the presence of Timp3 mutations. To determine if the RPE of Timp3 mutant mice is more susceptible to degeneration when exposed to low levels of oxidative stress, mice were injected with low doses of sodium iodate. The RPE and photoreceptors in Timp3 mutant mice degenerated at low doses of sodium iodate, which had no effect in wildtype control mice. These studies suggest that TIMP3 mutations may result in a dysregulation of pro-oxidant-antioxidant homeostasis in the RPE, leading to RPE degeneration in SFD.

Primary cilia are present on endothelial cells of the hyaloid vasculature but are not required for the development of the blood-retinal barrier

Endothelial cilia are found in a variety of tissues including the cranial vasculature of zebrafish embryos. Recently, endothelial cells in the developing mouse retina were reported to also possess primary cilia that are potentially involved in vascular remodeling. Fish carrying mutations in intraflagellar transport (ift) genes have disrupted cilia and have been reported to have an increased rate of spontaneous intracranial hemorrhage (ICH), potentially due to disruption of the sonic hedgehog (shh) signaling pathway. However, it remains unknown whether the endothelial cells forming the retinal microvasculature in zebrafish also possess cilia, and whether endothelial cilia are necessary for development and maintenance of the blood-retinal barrier (BRB). In the present study, we found that the endothelial cells lining the zebrafish hyaloid vasculature possess primary cilia during development. To determine whether endothelial cilia are necessary for BRB integrity, ift57, ift88, and ift172 mutants, which lack cilia, were crossed with the double-transgenic zebrafish strain Tg(l-fabp:DBP-EGFP;flk1:mCherry). This strain expresses a vitamin D-binding protein (DBP) fused to enhanced green fluorescent protein (EGFP) as a tracer in the blood plasma, while the endothelial cells forming the vasculature are tagged by mCherry. The Ift mutant fish develop a functional BRB, indicating that endothelial cilia are not necessary for early BRB integrity. Additionally, although treatment of zebrafish larvae with Shh inhibitor cyclopamine results in BRB breakdown, the Ift mutant fish were not sensitized to cyclopamine-induced BRB breakdown.

A novel TIMP3 mutation associated with a retinitis pigmentosa-like phenotype

BACKGROUND

Sorsby Fundus Dystrophy is an inherited macular degeneration caused by pathogenic variants in the TIMP3 gene. Clinical exam findings typically drusen -like deposits beneath the RPE or reticular pseudo drusen deposits above the RPE with a majority of patients developing choroidal neovascularization.

MATERIALS AND METHODS

Case report of two members of a family that present with atypical clinical exam findings. Protein modeling of the novel Y137CTIMP3 variant was performed and compared with other known variants.

RESULTS

In this study we describe a father and son initially diagnosed with retinitis pigmentosa of unknown genetic origin. More recent genetic testing of the patients, identified a novel c.410A>G; p.Tyr137Cys variant of uncertain clinical significance in the Tissue Inhibitor of Metalloproteinase-3 (TIMP3) gene. The atypical clinical findings led us to compare the theoretical molecular effects of this variant on the TIMP3 protein structure and interactions with other proteins using homology modeling and machine learning predictions.

CONCLUSIONS

It is important to consider mutations in TIMP3 in atypical cases of Retinitis Pigmentosa particularly in the absence of known variants.

Inhibition of choroidal neovascularization by systemic delivery of gold nanoparticles

Choroidal neovascularization (CNV) is the abnormal growth of blood vessels that sprout from the choroid vasculature and grow beneath and into the retina. The newly formed blood vessels in CNV often leak blood and fluid which deteriorates vision over time, eventually leading to blindness. In the present study, we examined the efficacy of intravenously injected gold nanoparticles in the laser-induced CNV animal model. Using optical coherence tomography (OCT) and fluorescein angiography, we evaluated CNV lesions longitudinally, over a period of 21 days, with and without nanoparticle treatment. Intravenously injected low concentration of bare gold nanoparticles showed significant anti-angiogenic properties by suppressing CNV development and progression. The treatment group showed significantly decreased fluorescein leakage at the CNV site compared to vehicle injected control mice. OCT assisted CNV volume measurement at all time points showed a significant reduction in lesion size in the treatment group compared with controls.

Role of FGF and Hyaluronan in Choroidal Neovascularization in Sorsby Fundus Dystrophy

Sorsby's fundus dystrophy (SFD) is an inherited blinding disorder caused by mutations in the tissue inhibitor of metalloproteinase-3 (TIMP3) gene. The SFD pathology of macular degeneration with subretinal deposits and choroidal neovascularization (CNV) closely resembles that of the more common age-related macular degeneration (AMD). The objective of this study was to gain further insight into the molecular mechanism(s) by which mutant TIMP3 induces CNV. In this study we demonstrate that hyaluronan (HA), a large glycosaminoglycan, is elevated in the plasma and retinal pigment epithelium (RPE)/choroid of patients with AMD. Mice carrying the S179C-TIMP3 mutation also showed increased plasma levels of HA as well as accumulation of HA around the RPE in the retina. Human RPE cells expressing the S179C-TIMP3 mutation accumulated HA apically, intracellularly and basally when cultured long-term compared with cells expressing wildtype TIMP3. We recently reported that RPE cells carrying the S179C-TIMP3 mutation have the propensity to induce angiogenesis via basic fibroblast growth factor (FGF-2). We now demonstrate that FGF-2 induces accumulation of HA in RPE cells. These results suggest that the TIMP3-MMP-FGF-2-HA axis may have an important role in the pathogenesis of CNV in SFD and possibly AMD.

The fenestrae-associated protein Plvap regulates the rate of blood-borne protein passage into the hypophysis

To maintain body homeostasis, endocrine systems must detect and integrate blood-borne peripheral signals. This is mediated by fenestrae, specialized permeable pores in the endothelial membrane. Plasmalemma vesicle-associated protein (Plvap) is located in the fenestral diaphragm and is thought to play a role in the passage of proteins through the fenestrae. However, this suggested function has yet to be demonstrated directly. We studied the development of fenestrated capillaries in the hypophysis, a major neuroendocrine interface between the blood and brain. Using a transgenic biosensor to visualize the vascular excretion of the genetically tagged plasma protein DBP-EGFP, we show that the developmental acquisition of vascular permeability coincides with differential expression of zebrafish plvap orthologs in the hypophysis versus brain. Ultrastructural analysis revealed that plvapb mutants display deficiencies in fenestral diaphragms and increased density of hypophyseal fenestrae. Measurements of DBP-EGFP extravasation in plvapb mutants provided direct proof that Plvap limits the rate of blood-borne protein passage through fenestrated endothelia. We present the regulatory role of Plvap in the development of blood-borne protein detection machinery at a neuroendocrine interface through which hormones are released to the general circulation.

Sorsby Fundus Dystrophy Mutation in Tissue Inhibitor of Metalloproteinase 3 (TIMP3) promotes Choroidal Neovascularization via a Fibroblast Growth Factor-dependent Mechanism

Choroidal neovascularization (CNV) leads to loss of vision in patients with Sorsby Fundus Dystrophy (SFD), an inherited, macular degenerative disorder, caused by mutations in the Tissue Inhibitor of Metalloproteinase-3 (TIMP3) gene. SFD closely resembles age-related macular degeneration (AMD), which is the leading cause of blindness in the elderly population of the Western hemisphere. Variants in TIMP3 gene have recently been identified in patients with AMD. A majority of patients with AMD also lose vision as a consequence of choroidal neovascularization (CNV). Thus, understanding the molecular mechanisms that contribute to CNV as a consequence of TIMP-3 mutations will provide insight into the pathophysiology in SFD and likely the neovascular component of the more commonly seen AMD. While the role of VEGF in CNV has been studied extensively, it is becoming increasingly clear that other factors likely play a significant role. The objective of this study was to test the hypothesis that basic Fibroblast Growth Factor (bFGF) regulates SFD-related CNV. In this study we demonstrate that mice expressing mutant TIMP3 (Timp3S179C/S179C) showed reduced MMP inhibitory activity with an increase in MMP2 activity and bFGF levels, as well as accentuated CNV leakage when subjected to laser injury. S179C mutant-TIMP3 in retinal pigment epithelial (RPE) cells showed increased secretion of bFGF and conditioned medium from these cells induced increased angiogenesis in endothelial cells. These studies suggest that S179C-TIMP3 may promote angiogenesis and CNV via a FGFR-1-dependent pathway by increasing bFGF release and activity.

Prolonged ocular exposure leads to retinal lesions in mice

Retinal lesions in the posterior pole of laboratory mice occur due to native, developmental abnormalities or as a consequence of environmental or experimental conditions. In this study, we investigated the rate and extent of retinal lesions as a result of prolonged ocular exposure following general anesthesia. Following experimental preparation induction procedures (EPIP) involving general anesthesia, mydriasis/cycloplegia, and topical anesthesia to the cornea, two ocular recovery conditions (protected and unprotected) were tested within two different animal recovery chambers (open or closed). The anterior and posterior poles were evaluated for the development of retinal lesions using digital color photography, scanning laser ophthalmoscopy, and spectral-domain optical coherence during anesthesia recovery and up to 2.5 months thereafter. In some mice, electroretinograms, histological and immunohistological evaluations were performed to assess functional and structural changes that accompanied the retinal lesions detected by in vivo imaging. Our data suggests that prolonged ocular surface exposure to circulating ambient room air leads to significant anterior and posterior segment ocular complications. The most abundant, semi-reversible complication observed was the development of lesions in the outer retina, which had a 90% probability of occurring after 45 min of exposure. The lesions mostly resolved short-term, but functional and imaging evidence suggest that some perturbations to the outer retina may persist one or more months following initial development.

Heterogeneity of cultured melanocyte elongation and proliferation factor in bilateral diffuse uveal melanocytic proliferation

A patient with bilateral diffuse uveal melanocytic proliferation (BDUMP) associated with endometrial cancer was treated with plasmapheresis, but failed therapy with progressive serous retinal detachment. We collected plasma before and after plasmapheresis therapy. Our goal was to determine if the cultured melanocyte elongation and proliferation (CMEP) factor and hepatocyte growth factor (HGF) was present in the IgG enriched fraction and understand why our patient failed plasmapheresis therapy. Melanocytes were cultured for 3-5 days in the presence of control medium, unfractionated pre-plasmapheresis BDUMP medium, IgG enriched or IgG depleted BDUMP medium, or unfractionated post-plasmapheresis BDUMP medium. Subretinal fluid was collected from patients with BDUMP and control retinal detachments and analyzed by electropheresis with immunoblotting. Medium with unfractionated BDUMP plasma stimulated melanocyte growth 1.4-1.5 fold compared to control medium on days 3-5 (p < 0.001 for all). Both IgG enriched and IgG depleted BDUMP medium mildly increased melanocyte growth 1.3 fold (p < 0.05 for enriched, p < 0.01 for depleted) compared to control. In comparison, unfractionated BDUMP medium caused a 1.7-fold increase in melanocyte growth, which was significantly more than the enriched (p < 0.01) and depleted (p < 0.05) fractions. Pre-plasmapheresis and post-plasmapheresis unfractionated BDUMP medium equally stimulated melanocyte growth 1.7-fold (p < 0.05) compared to control. HGF was present in IgG depleted, pre-plasmapheresis, and post-plasmapheresis samples, but absent in the IgG enriched fraction. There was no enrichment of IgG in the subretinal fluid from eyes with BDUMP. In conclusion, CMEP factor is not concentrated in the IgG enriched plasma fraction in our patient who failed plasmapheresis therapy. HGF levels have no correlation with melanocyte growth. Because plasmapheresis preferentially removes immunoglobulins from the plasma, our patient responded poorly to plasmapheresis treatment with worsening retinal detachment.

Sorsby fundus dystrophy: Insights from the past and looking to the future

Sorsby fundus dystrophy (SFD), an autosomal dominant, fully penetrant, degenerative disease of the macula, is manifested by symptoms of night blindness or sudden loss of visual acuity, usually in the third to fourth decades of life due to choroidal neovascularization (CNV). SFD is caused by specific mutations in the Tissue Inhibitor of Metalloproteinase-3, (TIMP3) gene. The predominant histo-pathological feature in the eyes of patients with SFD are confluent 20-30 m thick, amorphous deposits found between the basement membrane of the retinal pigment epithelium (RPE) and the inner collagenous layer of Bruch's membrane. SFD is a rare disease but it has generated significant interest because it closely resembles the exudative or "wet" form of the more common age-related macular degeneration (AMD). In addition, in both SFD and AMD donor eyes, sub-retinal deposits have been shown to accumulate TIMP3 protein. Understanding the molecular functions of wild-type and mutant TIMP3 will provide significant insights into the patho-physiology of SFD and perhaps AMD. This review summarizes the current knowledge on TIMP3 and how mutations in TIMP3 cause SFD to provide insights into how we can study this disease going forward. Findings from these studies could have potential therapeutic implications for both SFD and AMD.

Endogenous insulin signaling in the RPE contributes to the maintenance of rod photoreceptor function in diabetes

In diabetes, there are two major physiological aberrations: (i) Loss of insulin signaling due to absence of insulin (type 1 diabetes) or insulin resistance (type 2 diabetes) and (ii) increased blood glucose levels. The retina has a high proclivity to damage following diabetes, and much of the pathology seen in diabetic retinopathy has been ascribed to hyperglycemia and downstream cascades activated by increased blood glucose. However, less attention has been focused on the direct role of insulin on retinal physiology, likely due to the fact that uptake of glucose in retinal cells is not insulin-dependent. The retinal pigment epithelium (RPE) is instrumental in maintaining the structural and functional integrity of the retina. Recent studies have suggested that RPE dysfunction is a precursor of, and contributes to, the development of diabetic retinopathy. To evaluate the role of insulin on RPE cell function directly, we generated a RPE specific insulin receptor (IR) knockout (RPEIRKO) mouse using the Cre-loxP system. Using this mouse, we sought to determine the impact of insulin-mediated signaling in the RPE on retinal function under physiological control conditions as well as in streptozotocin (STZ)-induced diabetes. We demonstrate that loss of RPE-specific IR expression resulted in lower a- and b-wave electroretinogram amplitudes in diabetic mice as compared to diabetic mice that expressed IR on the RPE. Interestingly, RPEIRKO mice did not exhibit significant differences in the amplitude of the RPE-dependent electroretinogram c-wave as compared to diabetic controls. However, loss of IR-mediated signaling in the RPE reduced levels of reactive oxygen species and the expression of pro-inflammatory cytokines in the retina of diabetic mice. These results imply that IR-mediated signaling in the RPE regulates photoreceptor function and may play a role in the generation of oxidative stress and inflammation in the retina in diabetes.

Retinoic acid signaling is essential for maintenance of the blood-retinal barrier

The predominant function of the blood-retinal barrier (BRB) is to maintain retinal homeostasis by regulating the influx and efflux between the blood and retina. Breakdown of the BRB occurs in a number of ocular diseases that result in vision loss. Understanding the molecular and cellular pathways involved in the development and maintenance of the BRB is critical to developing therapeutics for these conditions. To visualize the BRB in vivo, we used the transgenic Tg(l-fabp:DBP-EGFP:flk1:mCherry) zebrafish model that expresses vitamin D binding protein (a member of the albumin gene family) tagged to green fluorescent protein. Retinoic acid (RA) plays a number of important roles in vertebrate development and has been shown to play a protective role during inflammation-induced blood-brain barrier disruption. The role of RA in BRB development and maintenance remains unknown. To disrupt RA signaling, Tg(l-fabp:DBP-EGFP:flk1:mCherry) zebrafish were treated with N, N-diethylaminobenzaldehyde and 4-[(1 E)-2-[5,6-dihydro-5,5-dimethyl-8-(2-phenylethynyl)-2-naphthalenyl]ethenyl]benzoic acid, which are antagonists of retinal dehydrogenase and the RA receptor, respectively. Treatment with either compound resulted in BRB disruption and reduced visual acuity, whereas cotreatment with all- trans RA effectively rescued BRB integrity. Additionally, transgenic overexpression of Cyp26a1, which catalyzes RA degradation, resulted in breakdown of the BRB. Our results demonstrate that RA signaling is critical for maintenance of the BRB and could play a role in diseases such as diabetic macular edema.-Pollock, L. M., Xie, J., Bell, B. A., Anand-Apte, B. Retinoic acid signaling is essential for maintenance of the blood-retinal barrier.

Morphine alters the circulating proteolytic profile in mice: functional consequences on cellular migration and invasion

Opioids modulate the tumor microenvironment with potential functional consequences for tumor growth and metastasis. We evaluated the effects of morphine administration on the circulating proteolytic profile of tumor-free mice. Serum from morphine-treated (1 or 10 mg/kg, i.p. every 12 h) or saline-treated mice was collected at different time points and tested ex vivo in endothelial, lymphatic endothelial, and breast cancer cell migration assays. Serum from mice that were treated with 10 mg/kg morphine for 3 d displayed reduced chemotactic potential for endothelial and breast cancer cells, and elicited reduced cancer cell invasion through reconstituted basement membrane compared with serum from saline controls. This was associated with decreased circulating matrix metalloproteinase 9 (MMP-9) and increased circulating tissue inhibitor of metalloproteinase 1 (TIMP-1) and TIMP-3/4 as assessed by zymography and reverse zymography. By using quantitative RT-PCR, we confirmed morphine-induced alterations in MMP-9 and TIMP expression and identified organs, including the liver and spleen, in which these changes originated. Pharmacologic inhibition of MMP-9 abrogated the difference in chemotactic attraction between serum from saline-treated and morphine-treated mice, which indicated that reduced proteolytic ability mediated the decreased migration toward serum from morphine-treated mice. This novel mechanism may enable morphine administration to promote an environment that is less conducive to tumor growth, invasion, and metastasis.-Xie, N., Khabbazi, S., Nassar, Z. D., Gregory, K., Vithanage, T., Anand-Apte, B., Cabot, P. J., Sturgess, D., Shaw, P. N., Parat, M.-O. Morphine alters the circulating proteolytic profile in mice: functional consequences on cellular migration and invasion.

A mutagenesis-derived Lrp5 mouse mutant with abnormal retinal vasculature and low bone mineral density

PURPOSE

Familial exudative vitreoretinopathy (FEVR) is caused by mutations in the genes encoding low-density lipoprotein receptor-related protein (LRP5) or its interacting partners, namely frizzled class receptor 4 (FZD4) and norrin cystine knot growth factor (NDP). Mouse models for Lrp5, Fzd4, and Ndp have proven to be important for understanding the retinal pathophysiology underlying FEVR and systemic abnormalities related to defective Wnt signaling. Here, we report a new mouse mutant, tvrm111B, which was identified by electroretinogram (ERG) screening of mice generated in the Jackson Laboratory Translational Vision Research Models (TVRM) mutagenesis program.

METHODS

ERGs were used to examine outer retinal physiology. The retinal vasculature was examined by in vivo retinal imaging, as well as by histology and immunohistochemistry. The tvrm111B locus was identified by genetic mapping of mice generated in a cross to DBA/2J, and subsequent sequencing analysis. Gene expression was examined by real-time PCR of retinal RNA. Bone mineral density (BMD) was examined by peripheral dual-energy X-ray absorptiometry.

RESULTS

The tvrm111B allele is inherited as an autosomal recessive trait. Genetic mapping of the decreased ERG b-wave phenotype of tvrm111B mice localized the mutation to a region on chromosome 19 that included Lrp5. Sequencing of Lrp5 identified the insertion of a cytosine (c.4724_4725insC), which is predicted to cause a frameshift that disrupts the last three of five conserved PPPSPxS motifs in the cytoplasmic domain of LRP5, culminating in a premature termination. In addition to a reduced ERG b-wave, Lrp5^tvrm111B homozygotes have low BMD and abnormal features of the retinal vasculature that have been reported previously in Lrp5 mutant mice, including persistent hyaloid vessels, leakage on fluorescein angiography, and an absence of the deep retinal capillary bed.

CONCLUSIONS

The phenotype of the Lrp5^tvrm111B mutant includes abnormalities of the retinal vasculature and of BMD. This model may be a useful resource to further our understanding of the biological role of LRP5 and to evaluate experimental therapies for FEVR or other conditions associated with LRP5 dysfunction.

Eotaxin-Rich Proangiogenic Hematopoietic Progenitor Cells and CCR3+ Endothelium in the Atopic Asthmatic Response

Angiogenesis is closely linked to and precedes eosinophilic infiltration in asthma. Eosinophils are recruited into the airway by chemoattractant eotaxins, which are expressed by endothelial cells, smooth muscles cells, epithelial cells, and hematopoietic cells. We hypothesized that bone marrow-derived proangiogenic progenitor cells that contain eotaxins contribute to the initiation of angiogenesis and inflammation in asthma. Whole-lung allergen challenge of atopic asthma patients revealed vascular activation occurs within hours of challenge and before airway inflammation. The eotaxin receptor CCR3 was expressed at high levels on submucosal endothelial cells in patients and a murine model of asthma. Ex vivo exposure of murine endothelial cells to eotaxins induced migration and angiogenesis. In mechanistic studies, wild-type mice transplanted with eotaxin-1/2-deficient bone marrow had markedly less angiogenesis and inflammation in an atopic asthma model, whereas adoptive transfer of proangiogenic progenitor cells from wild-type mice in an atopic asthma model into the eotaxin-1/2-deficient mice led to angiogenesis and airway inflammation. The findings indicate that Th2-promoting hematopoietic progenitor cells are rapidly recruited to the lung upon allergen exposure and release eotaxins that coordinately activate endothelial cells, angiogenesis, and airway inflammation.

Retinal vasculature of adult zebrafish: in vivo imaging using confocal scanning laser ophthalmoscopy

Over the past 3 decades the zebrafish (Danio rerio) has become an important biomedical research species. As their use continues to grow additional techniques and tools will be required to keep pace with ongoing research using this species. In this paper we describe a novel method for in vivo imaging of the retinal vasculature in adult animals using a commercially available confocal scanning laser ophthalmoscope (SLO). With this instrumentation, we demonstrate the ability to distinguish diverse vascular phenotypes in different transgenic GFP lines. In addition this technology allows repeated visualization of the vasculature in individual zebrafish over time to document vascular leakage progression and recovery induced by intraocular delivery of proteins that induce vascular permeability. SLO of the retinal vasculature was found to be highly informative, providing images of high contrast and resolution that were capable of resolving individual vascular endothelial cells. Finally, the procedures required to acquire SLO images from zebrafish are non-invasive, simple to perform and can be achieved with low animal mortality, allowing repeated imaging of individual fish.

Simultaneous assessment of glomerular filtration and barrier function in live zebrafish

The zebrafish pronephros is a well-established model to study glomerular development, structure, and function. A few methods have been described to evaluate glomerular barrier function in zebrafish larvae so far. However, there is a need to assess glomerular filtration as well. In the present study, we extended the available methods by simultaneously measuring the intravascular clearances of Alexa fluor 647-conjugated 10-kDa dextran and FITC-conjugated 500-kDa dextran as indicators of glomerular filtration and barrier function, respectively. After intravascular injection of the dextrans, mean fluorescence intensities of both dextrans were measured in the cardinal vein of living zebrafish (4 days postfertilization) by confocal microscopy over time. We demonstrated that injected 10-kDa dextran was rapidly cleared from the circulation, became visible in the lumen of the pronephric tubule, quickly accumulated in tubular cells, and was detectably excreted at the cloaca. In contrast, 500-kDa dextran could not be visualized in the tubule at any time point. To check whether alterations in glomerular function can be quantified by our method, we injected morpholino oligonucleotides (MOs) against zebrafish nonmuscle myosin heavy chain IIA (zMyh9) or apolipoprotein L1 (zApol1). While glomerular filtration was reduced in zebrafish nonmuscle myosin heavy chain IIA MO-injected larvae, glomerular barrier function remained intact. In contrast, in zebrafish apolipoprotein L1 MO-injected larvae, glomerular barrier function was compromised as 500-kDa dextran disappeared from the circulation and became visible in tubular cells. In summary, we present a novel method that allows to simultaneously assess glomerular filtration and barrier function in live zebrafish.