Correlation of Optical Coherence Tomography and Retinal Histology in Normal and Pro23His Retinal Degeneration Pig

Exploring the Potential of Wild Olive (Acebuche) Oil as a Pharm-Food to Prevent Ocular Hypertension and Fibrotic Events in the Retina of Hypertensive Mice

SCOPE

Our laboratory has previously described the antioxidant and anti-inflammatory potential of a wild olive (acebuche, ACE) oil against hypertension-associated vascular retinopathies. The current study aims to analyze the antifibrotic effect of ACE oil on the retina of hypertensive mice.

METHODS AND RESULTS

Mice are rendered hypertensive by administration of NG-nitro-L-arginine-methyl-ester (L-NAME) and simultaneously subjected to dietary supplementation with ACE oil or a reference extra virgin olive oil (EVOO). Intraocular pressure (IOP) is measured by rebound tonometry, and retinal vasculature/layers are analyzed by fundus fluorescein angiography and optical coherence tomography. Different fibrosis-related parameters are analyzed in the retina and choroid of normotensive and hypertensive mice with or without oil supplementation. Besides preventing the alterations found in hypertensive animals, including increased IOP, reduced fluorescein signal, and altered retinal layer thickness, the ACE oil-enriched diet improves collagen metabolism by regulating the expression of major fibrotic process modulators (matrix metalloproteinases, tissue inhibitors of metalloproteinases, connective tissue growth factor, and transforming growth factor beta family).

CONCLUSION

Regular consumption of EVOO and ACE oil (with better outcomes in the latter) might help reduce abnormally high IOP values in the context of hypertension-related retinal damage, with significant reduction in the surrounding fibrotic process.

A novel porcine model of CLN3 Batten disease recapitulates clinical phenotypes

Mouse models of CLN3 Batten disease, a rare lysosomal storage disorder with no cure, have improved our understanding of CLN3 biology and therapeutics through their ease of use and a consistent display of cellular pathology. However, the translatability of murine models is limited by disparities in anatomy, body size, life span and inconsistent subtle behavior deficits that can be difficult to detect in CLN3 mutant mouse models, thereby limiting their use in preclinical studies. Here, we present a longitudinal characterization of a novel miniswine model of CLN3 disease that recapitulates the most common human pathogenic variant, an exon 7-8 deletion (CLN3Δex7/8). Progressive pathology and neuron loss is observed in various regions of the CLN3Δex7/8 miniswine brain and retina. Additionally, mutant miniswine present with retinal degeneration and motor abnormalities, similar to deficits seen in humans diagnosed with the disease. Taken together, the CLN3Δex7/8 miniswine model shows consistent and progressive Batten disease pathology, and behavioral impairment mirroring clinical presentation, demonstrating its value in studying the role of CLN3 and safety/efficacy of novel disease-modifying therapeutics.

In Vivo Imaging of Retinal and Choroidal Morphology and Vascular Plexuses of Vertebrates Using Swept-Source Optical Coherence Tomography

Purpose

To perform in vivo evaluation of the structural morphology and vascular plexuses of the neurosensory retina and choroid across vertebrate species using swept-source optical coherence tomography (SS-OCT) and SS-OCT angiography (SS-OCTA) imaging.

Methods

A custom-built SS-OCT system with an incorporated flexible imaging arm was used to acquire the three-dimensional (3D) retinal OCT and vascular OCTA data of five different vertebrates: a mouse (C57BL/6J), a rat (Long Evans), a gray short-tailed opossum (Monodelphis domestica), a white sturgeon (Acipenser transmontanus), and a great horned owl (Bubo virginianus).

Results

In vivo structural morphology of the retina and choroid, as well as en face OCTA images of retinal and choroidal vasculature of all species were generated. The retinal morphology and vascular plexuses were similar between rat and mouse, whereas distinct choroidal and paired superficial vessels were observed in the opossum retina. The retinal and vascular structure of the sturgeon, as well as the pecten oculi and overlying the avascular and choroidal vasculature in the owl retina are reported in vivo.

Conclusions

A high-quality two-dimensional and 3D in vivo visualization of the retinal structures and en face visualization of the retina and choroidal vascular plexus of vertebrates was possible. Our studies affirm that SS-OCT and SS-OCTA are viable methods for evaluating the in vivo retinal and choroidal structure across terrestrial, aquatic, and aerial vertebrates.

Translational Relevance

In vivo characterization of retinal morphology and vasculature plexus of multiple species using SS-OCT and SS-OCTA imaging can increase the pool of species available as models of human retinal diseases.

Mapping Retinal Abnormalities in Psychosis: Meta-analytical Evidence for Focal Peripapillary and Macular Reductions

BACKGROUND

Several studies have suggested that the retina structure is affected in schizophrenia spectrum disorders (SSD). We aimed to investigate the location and size of the potential differences between patients and healthy controls (HC) in several thickness and volume measures across the retina.

STUDY DESIGN

We included cross-sectional studies comparing peripapillary retinal nerve fiber layer (pRNFL) thickness, macular volume, macular thickness (MT), foveal thickness, ganglion cell and inner plexiform layer thickness (GCL+IPL), cup volume, and cup/disc ratio (C/D) in the right and/or left eyes and/or the pRNFL and MT quadrants between patients with SSD and HC. Search databases were MEDLINE, Web of Science, PsycINFO, Cochrane Central, and medrxiv.org. Risk of bias was assessed with the Newcastle-Ottawa Scale. Standardized mean differences (SMD), subgroup analysis, and meta-regression with several variables were computed using the dmetar package in R. PROSPERO: CRD42021287873.

STUDY RESULTS

Data from 22 reports (942 patients, 742 HC) were included. We found a retinal thinning in pRNFL (-0.30; 95% CI: -0.46, -0.14), macula (-0.37; 95% CI: -0.61, -0.13), and GCL+IPL (-0.33; 95% CI: -0.57, -0.10). The retinal thinning was especially pronounced in the superior and inferior quadrants of the inner ring of the macula. We also observed a decrease of macular volume (-0.44; 95% CI: -0.68, -0.20) and an increase in C/D ratio (0.35; 95% CI: 0.03, 0.67).

CONCLUSIONS

Current evidence demonstrates retinal thinning in SSD, affecting both axonal and cellular structures, specially focused in the inner ring of the macula.

OCT guided micro-focal ERG system with multiple stimulation wavelengths for characterization of ocular health

Inherited retinal disorders and dry age-related macular degeneration are characterized by the degeneration and death of different types of photoreceptors at different rate and locations. Advancement of new therapeutic interventions such as optogenetics gene therapy and cell replacement therapies are dependent on electrophysiological measurements at cellular resolution. Here, we report the development of an optical coherence tomography (OCT) guided micro-focal multi-color laser stimulation and electroretinogram (ERG) platform for highly localized monitoring of retina function. Functional evaluation of wild type and transgenic pigs affected by retinal degeneration was carried out using OCT guided micro-focal ERG (μfERG) with selected stimulation wavelengths for S, M and L cones as well as rod photoreceptors. In wild type pigs, μfERG allowed functional recording from rods and each type of cone photoreceptor cells separately. Furthermore, functional deficits in P23H transgenic pigs consistent with their retinal degeneration phenotype were observed, including decrease in the S and M cone function and lack of rod photoreceptor function. OCT guided μfERG based monitoring of physiological function will enable characterization of animal models of retinal degenerative diseases and evaluation of therapeutic interventions at the cellular level.

Normative Data of Axial Length, Retinal Thickness Measurements, Visual Evoked Potentials, and Full-Field Electroretinography in Female, Wild-Type Minipigs

Purpose

The purpose of this study was to present normative data of optical coherence tomography (OCT), electrophysiological, and ocular biometry parameters and their correlation in minipigs.

Methods

Eighty-eight eyes of 44 minipigs underwent full-field electroretinogram (ERG) recording and ocular biometry. However, 10 eyes of 6 minipigs were excluded because of poor OCT image quality. The thickness of the retinal sublayers was measured on a vertical line at 5 locations with a 1 mm interval from the disc margin to the dorsal periphery and at 10 locations on the visual streak. Visual evoked potentials (VEPs) were measured in 15 eyes of 8 minipigs.

Results

All minipigs were female with a mean age and axial length of 13.83 ± 10.56 months and 20.33 ± 0.88 mm, respectively. The implicit time of the a-wave and b-wave in scotopic 3.0 ERGs was longer than that in photopic 3.0 ERG. The implicit time of the n2-wave and p2-wave in VEP was 25.67 ± 7.41 ms and 52.96 ± 10.38 ms, respectively. The total retinal layer (TRL) and nerve fiber layer (NFL) became thinner near the periphery. The inner retinal sublayers near the visual streak were thicker than those at other locations. Central TRL and NFL thickness on visual streak was 223.06 ± 23.19 µm and 74.03 ± 13.93 µm, respectively. The temporal TRL and NFL on the visual streak were thicker than those on the nasal side.

Conclusions

The normative electrophysiological and OCT parameters used in our study can be used as reference data in further pig studies.

Translational Relevance

This study presents normative data of minipigs, which are adequate animal models for preclinical studies.

In vivo imaging of the inner retinal layer structure in mice after eye-opening using visible-light optical coherence tomography

The growth of the mouse eye and retina after birth is a dynamic, highly regulated process. In this study, we applied visible-light optical coherence tomography (vis-OCT), a non-invasive imaging technique, to examine developing retinal layer structures after eye-opening. We introduced a resampled circumpapillary B-scan averaging technique to improve the inter-layer contrast, enabling retinal layer thickness measurements as early as postnatal day 13 (P13) - right after eye-opening. We confirmed vis-OCT measurements using ex vivo confocal microscopy of retinal sections at different ages. Our results demonstrate that vis-OCT can visualize the developmental murine retinal layer structure in vivo, which offers us new opportunities to better characterize the pathological alterations in mouse models of developmental eye diseases.

Corneal-Smart Phone: A novel method to intelligently estimate postmortem interval

The changes of postmortem corneal opacity are often used to roughly estimate the postmortem interval (PMI) in forensic practice. The difficulty associated with this time estimate is the lack of objective means to rapidly quantify postmortem corneal changes in crime scenes. This study constructed a data analysis model of PMI estimation and implemented an intelligent analysis system for examining the sequential changes of postmortem corneal digital images, named Corneal-Smart Phone, which can be used to quickly estimate PMI. The smart phone was used in combination with an attachment device that provided a darkroom environment and a steady light source to capture postmortem corneal images. By segmenting the corneal pupil region images, six color features, Red (R), Green (G), Blue (B), Hue (H), Saturation (S), Brightness (V) and four texture features Contrast (CON), Correlation (COR), Angular Second Moment (ASM), and Homogeneity (HOM), were extracted and correlated with PMI model. The results indicated that CON had the highest correlation with PMI (R²  = 0.983). No intra/intersubject variation in CON values were observed (p > 0.05). With the increase in ambient temperature or the decrease in humidity, the CON values were increased. PMI prediction error was <3 h within 36 h postmortem and extended to about 6-8 h after 36 h postmortem. The correct classification rate of the blind test samples was 82%. Our study provides a method that combines postmortem corneal image acquisition and digital image analysis to enable users to quickly obtain PMI estimation.

Neonatal and Juvenile Ocular Development in Göttingen Minipigs and Domestic Pigs: A Histomorphological and Immunohistochemical Study

Pigs are considered one of the relevant animal models for ocular research as they share several histological and anatomical similarities with the human eye. With the increasing interest in juvenile animal models, this study aimed to describe the postnatal development of ocular structures in 16 Göttingen minipigs and 25 F2 domestic pigs, between birth and 6 months of age, using histopathology and immunohistochemistry against Ki-67, caspase-3, calbindin, glial fibrillary acidic protein, rhodopsin, and synaptophysin. All ocular structures in both pig breeds were incompletely developed at birth and for variable periods postnatally. Noteworthy histological features of immaturity included vascularization in the corneal stroma in neonatal Göttingen minipigs, increased cellularity in different substructures, remnants of the hyaloid vasculature, short and poorly ramified ciliary body processes, and a poorly developed cone inner segment. Increased cellular proliferation, highlighted by abundant Ki-67 immunolabeling, was observed in almost all developing structures of the pig eye for variable periods postnatally. Apoptosis, highlighted with caspase-3 immunolabeling, was observed in the retinal inner nuclear layer at birth and in the regressing hyaloid vasculature remnants. Immunohistochemistry against rhodopsin, synaptophysin, and calbindin demonstrated the short size of the developing photoreceptors and the immature cone inner segment morphology. Calbindin labeling revealed significant differences in the amount of positively labeled cone nuclei between the retinal area centralis and the non-area centralis regions. The elongation of Müller cell processes in the developing retina was shown with glial fibrillary acidic protein. In both pig breeds, the eyes reached histomorphological and immunohistochemical maturity at 6 months of age.

Interpretation of OCT and OCTA images from a histological approach: Clinical and experimental implications

Optical coherence tomography (OCT) and OCT angiography (OCTA) have been a technological breakthrough in the diagnosis, treatment, and follow-up of many retinal diseases, thanks to its resolution and its ability to inform of the retinal state in seconds, which gives relevant information about retinal degeneration. In this review, we present an immunohistochemical description of the human and mice retina and we correlate it with the OCT bands in health and pathological conditions. Here, we propose an interpretation of the four outer hyperreflective OCT bands with a correspondence to retinal histology: the first and innermost band as the external limiting membrane (ELM), the second band as the cone ellipsoid zone (EZ), the third band as the outer segment tips phagocytosed by the pigment epithelium (PhaZ), and the fourth band as the mitochondria in the basal portion of the RPE (RPEmitZ). The integrity of these bands would reflect the health of photoreceptors and retinal pigment epithelium. Moreover, we describe how the vascular plexuses vary in different regions of the healthy human and mice retina, using OCTA and immunohistochemistry. In humans, four, three, two or one plexuses can be observed depending on the distance from the fovea. Also, specific structures such as vascular loops in the intermediate capillary plexus, or spider-like structures of interconnected capillaries in the deep capillary plexus are found. In mice, three vascular plexuses occupy the whole retina, except in the most peripheral retina where only two plexuses are found. These morphological issues should be considered when assessing a pathology, as some retinal diseases are associated with structural changes in blood vessels. Therefore, the analysis of OCT bands and OCTA vascular plexuses may be complementary for the diagnosis and prognosis of retinal degenerative processes, useful to assess therapeutic approaches, and it is usually correlated to visual acuity.

A Common Outer Retinal Change in Retinal Degeneration by Optical Coherence Tomography Can Be Used to Assess Outcomes of Gene Therapy

Identifying early disease hallmarks in animal models with slow disease progression may expedite disease detection and assessment of treatment outcomes. Using optical coherence tomography, a widely applied noninvasive method for monitoring retinal structure changes, we analyzed retinal optical sections from six mouse lines with retinal degeneration caused by mutations in different disease-causing genes. While images from wild-type mice revealed four well-separated hyper-reflective bands in the outer retina (designated as outer retina reflective bands, ORRBs) at all ages, the second band (ORRB2) and the third band (ORRB3) were merged in retinas of five mutant mouse lines at early ages, suggesting the pathological nature of this alteration. This ORRB change appeared to be degenerating photoreceptor related, and occurred before obvious morphological changes that can be identified on both hematoxylin and eosin-stained sections and electron microscopic sections. Importantly, the merging of ORRB2 and ORRB3 was reversed by treatment with adeno-associated viral vector-mediated gene replacement therapies, and this restoration occurred much earlier than measurable functional or structural improvement. Our data suggest that the ORRB change could be a common hallmark of early retinal degeneration and its restoration could be used for rapid and noninvasive assessment of therapeutic effects following gene therapy or other treatment interventions.

Noninvasive Imaging and Correlative Histology of Cone Photoreceptor Structure in the Pig Retina

PURPOSE

To evaluate different methods of studying cone photoreceptor structure in wild-type (WT) and transgenic pigs carrying the human rhodopsin P23H mutant gene (TgP23H).

METHODS

For in vivo imaging, pigs were anesthetized with tiletamine-zolazepam and isoflurane and given lidocaine-bupivacaine retrobulbar injections. Stay sutures and a custom head mount were used to hold and steer the head for adaptive optics scanning light ophthalmoscopy (AOSLO). Six WT and TgP23H littermates were imaged at postnatal day 30 (P30), P90, and P180 with AOSLO and optical coherence tomography (OCT), and two additional sets of littermates were imaged at P3 and P15 with OCT only. AOSLO imaging and correlative differential interference contrast microscopy were performed on a P240 WT pig and on WT and TgP23H littermates at P30 and P180.

RESULTS

AOSLO cone density generally underestimates histology density (mean difference ± SD = 24.8% ± 21.4%). The intensity of the outer retinal hyperreflective OCT band attributed to photoreceptors is attenuated in TgP23H pigs at all ages. In contrast, AOSLO images show cones that retain inner and outer segments through P180. At retinal locations outside the visual streak, TgP23H pigs show a heterogeneous degenerating cone mosaic by using two criteria: variable contrast on a split detector AOSLO and high reflectivity on a confocal AOSLO.

CONCLUSIONS

AOSLO reveals that the cone mosaic is similar to ex vivo histology. Its use as a noninvasive tool will enable observation of morphologic changes that arise in the cone mosaic of TgP23H pigs over time.

TRANSLATIONAL RELEVANCE

Pigs are widely used for translational studies, and the ability to noninvasively assess cellular changes in the cone mosaic will facilitate more detailed investigations of new retinal disease models as well as outcomes of potential therapies.