Primate Eye Research Articles

Safety and efficacy of CRISPR-mediated genome ablation of VEGFA as a treatment for choroidal neovascularization in nonhuman primate eyes

CRISPR-based genome editing enables permanent suppression of angiogenic factors like vascular endothelial growth factor (VEGF) as potential treatment for choroidal neovascularization (CNV) – a major cause of blindness in age-related macular degeneration. We previously designed adeno-associated viral (AAV) vectors with S. pyogenes Cas 9 (SpCas9) and guide RNAs (gRNAs) to target conserved sequences in VEGFA across mouse, rhesus macaque, and human, with successful suppression of VEGF and laser-induced CNV in mice. Here, we advanced the platform to nonhuman primates and found that subretinal AAV8-SpCas9 with gRNAs targeting VEGFA may reduce VEGF and CNV severity as compared to SpCas9 without gRNAs. However, all eyes that received AAV8-SpCas9 regardless of gRNA presence developed subfoveal deposits, concentric macular rings, and outer retinal disruption that worsened at higher dose. Immunohistochemistry showed subfoveal accumulation of retinal pigment epithelial cells, collagen, and vimentin, disrupted photoreceptor structure, and retinal glial and microglial activation. Subretinal AAV8-SpCas9 triggered aqueous elevations in CCL2, but minimal systemic humoral or cellular responses against AAV8, SpCas9, or GFP reporter. Our findings suggest that CRISPR-mediated VEGFA ablation in NHP eyes may suppress VEGF and CNV, but can also lead to unexpected subretinal fibrosis, photoreceptor damage, and retinal inflammation despite minimal systemic immune responses.

Lamina Cribrosa Microstructure in Nonhuman Primates With Naturally Occurring Peripapillary Retinal Nerve Fiber Layer Thinning.

The lamina cribrosa (LC) is hypothesized to be the site of initial axonal damage in glaucoma with the circumpapillary retinal nerve fiber layer thickness (RNFL-T) widely used as a standard metric for quantifying the glaucomatous damage. The purpose of this study was to determine in vivo, 3-dimensional (3D) differences in the microstructure of the LC in eyes of nonhuman primates (NHPs) with naturally occurring glaucoma. Spectral-domain optical coherence tomography (OCT) scans (Leica, Chicago, IL, USA) of the optic nerve head were acquired from a colony of 50 adult rhesus monkeys suspected of having high prevalence of glaucoma. The RNFL-T was analyzed globally and in quadrants using a semi-automated segmentation software. From a set of 100 eyes, 18 eyes with the thinnest global RNFL-T were selected as the study group and 18 eyes with RNFL-T values around the 50th percentile were used as controls. A previously described automated segmentation algorithm was used for LC microstructure analysis. Parameters included beam thickness, pore diameter and their ratio (beam-to-pore ratio [BPR]), pore area and shape parameters, beam and pore volume, and connective tissue volume fraction (CTVF; beam volume/total volume). The LC microstructure was analyzed globally and in the following volumetric sectors: quadrants, central and peripheral lamina, and three depth slabs (anterior, middle, and posterior). Although no significant difference was detected between groups for age, weight, or disc size, the study group had significantly thinner RNFL than the control group (P < 0.01). The study group had significantly smaller global and sectoral pore diameter and larger BPR compared with the control group. Across eyes, the global RNFL-T was associated positively with pore diameter globally. BPR and CTVF were significantly and negatively associated with the corresponding RNFL-T in the superior quadrant. Global and sectoral microstructural differences were detected when comparing thin and normal RNFL-T eyes. Whether these LC differences are the cause of RNFL damage or the result of remodeling of the LC requires further investigation. Our findings indicate structural alterations in the LC of NHP exhibiting natural thinning of the RNFL, a common characteristic of glaucomatous damage.

In Vivo Visualization of Intravascular Patrolling Immune Cells in the Primate Eye.

Insight into the immune status of the living eye is essential as we seek to understand ocular disease and develop new treatments. The nonhuman primate (NHP) is the gold standard preclinical model for therapeutic development in ophthalmology, owing to the similar visual system and immune landscape in the NHP relative to the human. Here, we demonstrate the utility of phase-contrast adaptive optics scanning light ophthalmoscope (AOSLO) to visualize immune cell dynamics on the cellular scale, label-free in the NHP. Phase-contrast AOSLO was used to image preselected areas of retinal vasculature in five NHP eyes. Images were registered to correct for eye motion, temporally averaged, and analyzed for immune cell activity. Cell counts, dimensions, velocities, and frequency per vessel were determined manually and compared between retinal arterioles and venules. Based on cell appearance and circularity index, cells were divided into three morphologies: ovoid, semicircular, and flattened. Immune cells were observed migrating along vascular endothelium with and against blood flow. Cell velocity did not significantly differ between morphology or vessel type and was independent of blow flood. Venules had a significantly higher cell frequency than arterioles. A higher proportion of cells resembled "flattened" morphology in arterioles. Based on cell speeds, morphologies, and behaviors, we identified these cells as nonclassical patrolling monocytes (NCPMs). Phase-contrast AOSLO has the potential to reveal the once hidden behaviors of single immune cells in retinal circulation and can do so without the requirement of added contrast agents that may disrupt immune cell behavior.

Lens Power and Associated Factors in Nonhuman Primate Subjects: A Cross-sectional Study.

We aimed to examine the normative profile of crystalline lens power (LP) and its associations with ocular biometric parameters including age, axial length (AL), spherical equivalent refraction (SE), corneal radius (CR), lens thickness, anterior chamber depth, and AL/CR ratio among a cynomolgus monkey colony. This population-based cross-sectional Non-human Primate Eye Study recruited middle-aged subjects in South China. All included macaques underwent a detailed ophthalmic examination. LP was calculated using the modified Bennett's formula, with biometry data from an autorefractometer and A-scan. SPSS version 25.0 was used for statistical analysis. A total of 301 macaques with an average age of 18.75 ± 2.95years were collected in this study. The mean LP was 25.40 ± 2.96 D. Greater LP was independently associated with younger age, longer AL, and lower SE (P = 0.028, P = 0.025, and P = 0.034, respectively). LP showed a positive correlation with age, SE, CR, AL, lens thickness, and anterior chamber depth, whereas no correlation was observed between LP and AL/CR ratio. Our results suggested the LP distribution in the nonhuman primate colony and indicated that AL and SE strongly influenced the rate of LP. Therefore, this study contributed to a deeper understanding of the relative significance of the LP on the optics of the crystalline lens study.

Primate eye tracking with carbon-nanotube-paper-composite based capacitive sensors and machine learning algorithms

BackgroundAccurate real-time eye tracking is crucial in oculomotor system research. While the scleral search coil system is the gold standard, its implantation procedure and bulkiness pose challenges. Camera-based systems are affected by ambient lighting and require high computational and electric power. New MethodThis study presents a novel eye tracker using proximity capacitive sensors made of carbon-nanotube-paper-composite (CPC). These sensors detect femtofarad-level capacitance changes caused by primate corneal movement during horizontal and vertical eye rotations. Data processing and machine learning algorithms are evaluated to enhance the accuracy of gaze angle prediction. ResultsThe system performance is benchmarked against the scleral coil during smooth pursuits, saccades tracking, and fixations. The eye tracker demonstrates up to 0.97 correlation with the coil in eye tracking and is capable of estimating gaze angle with a median absolute error as low as 0.30°. ComparisonThe capacitive eye tracker demonstrates good consistency and accuracy in comparison to the gold-standard scleral search coil method. ConclusionsThis lightweight, non-invasive capacitive eye tracker offers potential as an alternative to traditional coil and camera-based systems in oculomotor research and vision science.

Graft cell expansion from hiPSC-RPE strip after transplantation in primate eyes with or without RPE damage

Clinical studies using suspensions or sheets of human pluripotent cell-derived retinal pigment epithelial cells (hiPSC-RPE) have been conducted globally for diseases such as age-related macular degeneration. Despite being minimally invasive, cell suspension transplantation faces challenges in targeted cell delivery and frequent cell leakage. Conversely, although the RPE sheet ensures targeted delivery with correct cell polarity, it requires invasive surgery, and graft preparation is time-consuming. We previously reported hiPSC-RPE strips as a form of quick cell aggregate that allows for reliable cell delivery to the target area with minimal invasiveness. In this study, we used a microsecond pulse laser to create a local RPE ablation model in cynomolgus monkey eyes. The hiPSC-RPE strips were transplanted into the RPE-ablated and intact sites. The hiPSC-RPE strip stably survived in all transplanted monkey eyes. The expansion area of the RPE from the engrafted strip was larger at the RPE injury site than at the intact site with no tumorigenic growth. Histological observation showed a monolayer expansion of the transplanted RPE cells with the expression of MERTK apically and collagen type 4 basally. The hiPSC-RPE strip is considered a beneficial transplantation option for RPE cell therapy.

Choroidal Morphology and Photoreceptor Activity Are Related and Affected by Myopia Development.

The choroid is critical for the regulation of eye growth and is involved in the pathogenesis of myopia-associated ocular complications. This study explores the relationship among choroidal biometry, photoreceptor activity, and myopic growth in marmosets (Callithrix jacchus) with lens-induced myopia. A total of 34 common marmosets aged 92 to 273days old were included in this study. Axial myopia was induced in 17 marmosets using negative soft contact lenses and 17 marmosets served as untreated controls. Cycloplegic refraction (RE) and vitreous chamber depth (VCD) were measured using autorefraction and A-scan ultrasonography, respectively. Choroidal scans were obtained using spectral-domain optical coherence tomography and binarized to calculate subfoveal choroidal thickness (ChT), total choroidal area (TCA), luminal area (LA), stromal area (SA), choroidal vascularity index (CVI), and LA/SA. To assess photoreceptor activity, the a-wave of the full-field electroretinogram was measured. Regression models were used to investigate the relationship between outcome measures. Eyes induced with axial myopia (RE = -7.14 ± 4.03 diopters [D], VCD = 6.86 ± 0.39mm) showed significant reductions (4.92-21.24%) in all choroidal parameters (ChT, TCA, LA, SA, CVI, and LA/SA) compared to controls (RE = -1.25 ± 0.60 D, VCD = 6.58 ± 0.26mm, all P < 0.05), which changed as a function of refraction and vitreous elongation, and were associated with a decrease in the a-wave amplitude. Further, multiple regression showed that a combination of ChT and CVI could well predict RE and VCD. This study reports the existence of significant alterations in choroidal morphology in non-human primate eyes induced with myopia. The changes in choroidal anatomy were associated with reduced light-adapted a-wave amplitude. These findings may represent early markers for reduced visual performance and chorioretinal complications known to occur in eyes with large degrees of myopia.

Expression patterns of CYP26A1, FGF8, CDKN1A, and NPVF in the developing rhesus monkey retina

The fovea centralis (fovea) is a specialized region of the primate retina that plays crucial roles in high-resolution visual acuity and color perception. The fovea is characterized by a high density of cone photoreceptors and no rods, and unique anatomical properties that contribute to its remarkable visual capabilities. Early histological analyses identified some of the key events that contribute to foveal development, but the mechanisms that direct the specification of this area are not understood. Recently, the expression of the retinoic acid-metabolizing enzyme CYP26A1 has become a hallmark of some of the retinal specializations found in vertebrates, including the primate fovea and the high-acuity area in avian species. In chickens, the retinoic acid pathway regulates the expression of FGF8 to then direct the development of a rod-free area. Similarly, high levels of CYP26A1, CDKN1A, and NPVF expression have been observed in the primate macula using transcriptomic approaches. However, which retinal cells express these genes and their expression dynamics in the developing primate eye remain unknown. Here, we systematically characterize the expression patterns of CYP26A1, FGF8, CDKN1A, and NPVF during the development of the rhesus monkey retina, from early stages of development in the first trimester until the third trimester (near term). Our data suggest that some of the markers previously proposed to be fovea-specific are not enriched in the progenitors of the rhesus monkey fovea. In contrast, CYP26A1 is expressed at high levels in the progenitors of the fovea, while it localizes in a subpopulation of macular Müller glia cells later in development. Together these data provide invaluable insights into the expression dynamics of several molecules in the nonhuman primate retina and highlight the developmental advancement of the foveal region.

Activation of primate frontal eye fields with a CMUT phased array system

BackgroundThere are pushes toward non-invasive stimulation of neural tissues to prevent issues that arise from invasive brain recordings and stimulation. Transcranial Focused Ultrasound (TFUS) has been examined as a way to stimulate non-invasively, but previous studies have limitations in the application of TFUS. As a result, refinement is needed to improve stimulation results. New MethodWe utilized a custom-built capacitive micromachined ultrasonic transducer (CMUT) that would send ultrasonic waves through skin and skull to targets located in the Frontal Eye Fields (FEF) region triangulated from co-registered MRI and CT scans while a non-human primate subject was performing a discrimination behavioral task. ResultsWe observed that the stimulation immediately caused changes in the local field potential (LFP) signal that continued until stimulation ended, at which point there was higher voltage upon the cue for the animal to saccade. This co-incided with increases in activity in the alpha band during stimulation. The activity rebounded mid-way through our electrode-shank, indicating a specific point of stimulation along the shank. We observed different LFP signals for different stimulation targets, indicating the ability to“steer” the stimulation through the transducer. We also observed a bias in first saccades towards the opposite direction. ConclusionsIn conclusion, we provide a new approach for non-invasive stimulation during performance of a behavioral task. With the ability to steer stimulation patterns and target using a large amount of transducers, the ability to provide non-invasive stimulation will be greatly improved for future clinical and research applications.

Poster Session: Optogenetic Stimulation and Calcium Imaging of Single Ganglion Cells in the Living Macaque Fovea.

The perceptual roles of most retinal ganglion cell (RGC) classes are controversial in part because we lack a paradigm for measuring the perceptual consequences of activating cells of only one class in the living primate eye. Recent success in classifying single RGCs with in vivo calcium imaging and in vivo optogenetic activation of RGCs en masse now bring such a paradigm within reach. As a first step, we demonstrate the optogenetic stimulation of single foveal RGCs in the living macaque. RGCs in an anesthetized female macaque were stimulated and imaged using adaptive optics scanning light ophthalmoscopy. Co-expression of ChrimsonR and GCaMP6s was achieved via intravitreal injection of a viral vector. On each trial, a targeted soma was exposed to four, 12.5 µm diameter flashes of 0.8 second duration. Targets were limited to those RGCs with at least a 20 µm separation from their nearest neighbors. The GCaMP responses to the flash of both targeted and nearby cells were imaged and the ΔF/F for each soma's response was averaged over the flashes. The ΔF/F values were used to calculate z-scores for each cell's response. Five cells were found to have responded significantly (z-score > 3.5) with no significant response from their neighbors. We can directly activate single RGCs in the living eye and measure the resulting calcium signal, the first step toward a method to measure the sensations produced by individual RGCs in the awake behaving monkey.

Nonhuman Primate Eyes Display Variable Growth and Aging Rates in Alignment With Human Eyes.

To assess age-related biometric changes of the eye in nonhuman primates (NHPs), to and decipher the growth and aging rates and their comparability with humans. Ocular anatomic measurements were performed on 341 macaca fascicularis aged 0.5 to 23 years via multimodal approaches including IOLMaster 700. Linear or polynomial regression models were simulated to determine the best fitted age-related function. The metrics were compared with human equivalents in published reports. Macaques exhibited a postnatal eye growth pattern similar to humans, characterized by continuous eye extension coordinated with dramatic reshaping of the lens but not the cornea. The age-related growth of lens thickness (LT), anterior chamber depth (ACD), and axis length (AL) exhibited nonlinear and bipolar patterns. The inflection points were 10 to 12 years old for LT and ACD and 13 to 15 years old for AL in macaques, which were comparable in chronological age at a ratio of ∼1: ratio with that in humans. In contrast, the speed of aging, including the increase in lens density and the decrease in retinal nerve fiber layer thickness, was comparable in relative age at a ratio of ∼1:3 according to the differences in lifespan between macaques and humans. Lens density was a robust indicator for the aging process. Macaque eyes recapitulated the age-related process of human eyes to varying extents with different growth and aging rates. Chronological age or relative age should be considered in different scenarios when macaques are included in preclinical studies.

Commentary: Retinal changes after internal limiting membrane peeling.

The internal limiting membrane (ILM) is the innermost of the 10 retinal layers. It is a transparent membrane measuring nearly 10 microns and is formed by the basement membrane of the Müller cells. It is peeled as a standard treatment of full-thickness macular hole (FTMH). However, many reports have shown that peeling the ILM may actually damage the retina. Wollensak et al.[1] showed that ILM removal reduces the mean strength of the central retina by almost half. Histological studies performed on human and primate eyes have shown that ILM peeling causes damage to the processes and end feet of the Müller cells. A selective delay has been noted in the B-wave recovery of focal macular electroretinogram in eyes that have undergone ILM peeling. Several anatomical changes have been described after ILM peeling.[2] Swelling of the arcuate nerve fiber layer (SANFL): It was first described by Clark et al.[3] as an early postoperative change. It is seen as hypoautofluorescent arcuate striae in the macular region on fundus autofluorescence (FAF) and infrared (IR) imaging; however, it cannot be detected on either biomicroscopic fundus examination or color photograph. It is seen as a hyperreflectant swelling on spectral domain optical coherence tomography (SD-OCT). It usually disappears gradually over a period of 2–3 months. It does not seem to affect the best-corrected visual acuity (BCVA) or retinal sensitivity. Dissociated optic nerve fiber layer (DONFL): It was first described by Tadayoni et al.[4] in 2001. It is also known as “concentric macular dark spots (CMDS)” or “inner retinal dimpling”.[2] It gives the macula a ‘‘moth-eaten’’ appearance due to the presence of small depressions on the retinal contour situated along the course of retinal nerve fibers on the en face scan. SD-OCT scans show that the depth of these dimples is limited to the RNFL only. Liu et al. found three distribution patterns, namely, papillomacular bundle-dominated, scattered, and temporal raphe-spared patters.[5] Ye et al.[6] showed that DONFL appeared within two months of surgery. The number progressed during the next four months and then slowed down. The number did not change after 12 months since the surgery. It has not been found to have association with either BCVA or retinal sensitivity. Steel et al.[7] showed that the use of a diamond-dusted membrane scraper to initiate the peel is a risk factor for the formation of DONFL. The extent of DONFL has been seen to be positively associated with the amount of cellular debris on the retinal side of the peeled ILM.[8] The perioperative optical coherence tomography (OCT) for ophthalmic surgery (PIONEER) study showed that the immediate increase in the inner retinal layer thickness on intraoperative OCT following ILM peeling was associated with the development of DONFL, while the technique used for peeling did not.[9] Foveal displacement: Several authors have reported a nasal shift of the fovea, that is, shortening of the foveopapillary distance (FPD). Ishida et al.[10] reported that the displacement was greater in the temporal retina compared to the nasal retina. They further reported that the degree of the retinal displacement significantly correlated with the maximum base diameter of the FTMH. However, Nair et al.[11] reported that a temporal foveal shift may be seen in around 25% of the eyes, especially those with a longer temporal segment. Ohta et al. reported that the steepness of the foveal slope increased after ILM peeling in an asymmetrical pattern as the nasal side became significantly steeper than the temporal one.[12] None of these findings seem to affect the BCVA or retinal sensitivity. Retinal thinning: Several studies have shown that the macular volume, especially that of the temporal macula, shows a progressive reduction.[2] It has been proposed that hemi-temporal ILM peeling is as effective as conventional 360-degree peeling for the treatment of FTMH. Additionally, it is associated with less retinal displacement, lesser DONFL formation, lower rates of subjective metamorphopsia, faster visual rehabilitation, and greater safety.[13–15] We congratulate the authors for their study showing that the outcomes of papillomacular bundle sparing ILM peeling is comparable to conventional ILM peeling in terms of hole closure rates and visual gain, with the advantage of less retinal damage for the treatment of idiopathic FTMH ≤400 microns.[16] Studies with larger sample size and larger macular hole size will help validate the surgical technique.

Neurons in Primate Area MSTd Signal Eye Movement Direction Inferred from Dynamic Perspective Cues in Optic Flow.

Smooth eye movements are common during natural viewing; we frequently rotate our eyes to track moving objects or to maintain fixation on an object during self-movement. Reliable information about smooth eye movements is crucial to various neural computations, such as estimating heading from optic flow or judging depth from motion parallax. While it is well established that extraretinal signals (e.g., efference copies of motor commands) carry critical information about eye velocity, the rotational optic flow field produced by eye rotations also carries valuable information. Although previous work has shown that dynamic perspective cues in optic flow can be used in computations that require estimates of eye velocity, it has remained unclear where and how the brain processes these visual cues and how they are integrated with extraretinal signals regarding eye rotation. We examined how neurons in the dorsal region of the medial superior temporal area (MSTd) of two male rhesus monkeys represent the direction of smooth pursuit eye movements based on both visual cues (dynamic perspective) and extraretinal signals. We find that most MSTd neurons have matched preferences for the direction of eye rotation based on visual and extraretinal signals. Moreover, neural responses to combinations of these signals are well predicted by a weighted linear summation model. These findings demonstrate a neural substrate for representing the velocity of smooth eye movements based on rotational optic flow and establish area MSTd as a key node for integrating visual and extraretinal signals into a more generalized representation of smooth eye movements.SIGNIFICANCE STATEMENT We frequently rotate our eyes to smoothly track objects of interest during self-motion. Information about eye velocity is crucial for a variety of computations performed by the brain, including depth perception and heading perception. Traditionally, information about eye rotation has been thought to arise mainly from extraretinal signals, such as efference copies of motor commands. Previous work shows that eye velocity can also be inferred from rotational optic flow that accompanies smooth eye movements, but the neural origins of these visual signals about eye rotation have remained unknown. We demonstrate that macaque neurons signal the direction of smooth eye rotation based on visual signals, and that they integrate both visual and extraretinal signals regarding eye rotation in a congruent fashion.

Peptide-guided lipid nanoparticles deliver mRNA to the neural retina of rodents and nonhuman primates.

Lipid nanoparticle (LNP)-based mRNA delivery holds promise for the treatment of inherited retinal degenerations. Currently, LNP-mediated mRNA delivery is restricted to the retinal pigment epithelium (RPE) and Müller glia. LNPs must overcome ocular barriers to transfect neuronal cells critical for visual phototransduction, the photoreceptors (PRs). We used a combinatorial M13 bacteriophage-based heptameric peptide phage display library for the mining of peptide ligands that target PRs. We identified the most promising peptide candidates resulting from in vivo biopanning. Dye-conjugated peptides showed rapid localization to the PRs. LNPs decorated with the top-performing peptide ligands delivered mRNA to the PRs, RPE, and Müller glia in mice. This distribution translated to the nonhuman primate eye, wherein robust protein expression was observed in the PRs, Müller glia, and RPE. Overall, we have developed peptide-conjugated LNPs that can enable mRNA delivery to the neural retina, expanding the utility of LNP-mRNA therapies for inherited blindness.

Discovery of Clinical Manifestations in Spontaneous Glaucoma Suspect Nonhuman Primates

Introduction: The primary aim of this study was to assess the longitudinal changes in retinal nerve fiber layer (RNFL) thickness and relative ONH parameters using spectral-domain optical coherence tomography (SD-OCT) in the living eyes of nonhuman primates with spontaneous glaucoma. Methods: Totally 9 macaque subjects underwent a standard fundus photo and OCT examination, including 3 adult monkeys with stable elevated intraocular pressure (IOP) as the glaucoma suspect group and 6 normal IOP monkeys as the control group. Each eye of primates with IOP measurement was repeated three times. OCT measurements recorded RNFL, Bruch’s membrane opening (BMO) minimum rim width (MRW). The follow-up scan of glaucomatous subjects was undergone in 10 months. Results: The mean ages of glaucoma and healthy subjects are 19.33 ± 0.33 and 20.5 ± 1.46 years. Elevated IOP was achieved in three nonhuman primate eyes with an average increase of 10 mm Hg over the study period. Elevated IOP was associated with decreased RNFL thickness in all the regions and decreased RNFL phase retardation in the superior and inferior regions. When averaged over the entire retinal area, only the whole RNFL and temporal regions showed a significant decrease. The mean IPL thicknesses are 87.17 ± 2.15 μm in glaucomatous and 93.33 ± 1.51 μm in healthy eyes (p = 0.03). Lamina cribrosa parameters are measured from the OCT images and showed significant differences between glaucoma primates and normal primates. Conclusions: Of the measured parameters, decreased RNFL and MRW were correlated with glaucomatous damage. Natural glaucoma primate can be a natural glaucoma model which is closer to glaucoma in humans.

Mitomycin C-loaded PTMC15-F127-PTMC15 hydrogel maintained better bleb function after filtering glaucoma surgery in monkeys with intraocular hypertension.

There is an unmet need for a safer and more effective approach for antimetabolite application to prevent bleb fibrosis after glaucoma filtering surgery. Here, we utilized our previously developed thermosensitive sustained-release agent, mitomycin C-loaded poly(trimethylene carbonate)15-F127-poly(trimethylene carbonate)15 (MMC-hydrogel), aiming to further evaluate the efficacy and safety of MMC-hydrogel in high intraocular pressure (IOP) primate eyes. Twelve primate eyes after high IOP induction were randomly divided into three groups, which respectively received phosphate-buffered saline (PBS)-hydrogel, MMC-hydrogel, and MMC treatment during trabeculectomy. IOP and bleb volume were measured using a Tonopen and anterior segment optical coherence tomography over 28 days. At the end of the experiment, all experimental primate eyes were enucleated. Histopathology and immunohistochemistry were performed to reveal myofibroblast cells and collagen deposition of filtering blebs. The MMC-hydrogel group had satisfactory IOP control (9.25 ± 4.80 mmHg) and maintained well-functioning blebs for a longer time. Fibrosis and scarring were significantly alleviated in this MMC-hydrogel group. There was no obvious toxicity to ocular surfaces or intraocular structures. Taken together, these data suggest that PTMC15-F127-PTMC15-loaded MMC-hydrogel plays a role in functional maintenance and scarring inhibition, showing high efficacy in reducing post-filtering surgery bleb fibrosis. This MMC-hydrogel may offer a new solution for filtering bleb management after glaucoma surgery.

Neural correlates of curved saccades in the primate frontal eye field

Neural correlates of curved saccades in the primate frontal eye field

Calcium-permeable AMPA receptors on AII amacrine cells mediate sustained signaling in the On-pathway of the primate retina.

Midget and parasol ganglion cells (GCs) represent the major output channels from the primate eye to the brain. On-type midget and parasol GCs exhibit a higher background spike rate and thus can respond more linearly to contrast changes than their Off-type counterparts. Here, we show that a calcium-permeable AMPA receptor (CP-AMPAR) antagonist blocks background spiking and sustained light-evoked firing in On-type GCs while preserving transient light responses. These effects are selective for On-GCs and are occluded by a gap-junction blocker suggesting involvement of AII amacrine cells (AII-ACs). Direct recordings from AII-ACs, cobalt uptake experiments, and analyses of transcriptomic data confirm that CP-AMPARs are expressed by primate AII-ACs. Overall, our data demonstrate that under some background light levels, CP-AMPARs at the rod bipolar to AII-AC synapse drive sustained signaling in On-type GCs and thus contribute to the more linear contrast signaling of the primate On- versus Off-pathway.

Chimpanzee (Pan troglodytes) gaze is conspicuous at ecologically-relevant distances

Chimpanzee (Pan troglodytes) sclera appear much darker than the white sclera of human eyes, to such a degree that the direction of chimpanzee gaze may be concealed from conspecifics. Recent debate surrounding this topic has produced mixed results, with some evidence suggesting that (1) primate gaze is indeed concealed from their conspecifics, and (2) gaze colouration is among the suite of traits that distinguish uniquely social and cooperative humans from other primates (the cooperative eye hypothesis). Using a visual modelling approach that properly accounts for specific-specific vision, we reexamined this topic to estimate the extent to which chimpanzee eye coloration is discriminable. We photographed the faces of captive chimpanzees and quantified the discriminability of their pupil, iris, sclera, and surrounding skin. We considered biases of cameras, lighting conditions, and commercial photography software along with primate visual acuity, colour sensitivity, and discrimination ability. Our visual modeling of chimpanzee eye coloration suggests that chimpanzee gaze is visible to conspecifics at a range of distances (within approximately 10 m) appropriate for many species-typical behaviours. We also found that chimpanzee gaze is discriminable to the visual system of primates that chimpanzees prey upon, Colobus monkeys. Chimpanzee sclera colour does not effectively conceal gaze, and we discuss this result with regard to the cooperative eye hypothesis, the evolution of primate eye colouration, and methodological best practices for future primate visual ecology research.

Expanding RNAi therapeutics to extrahepatic tissues with lipophilic conjugates.

Therapeutics based on short interfering RNAs (siRNAs) delivered to hepatocytes have been approved, but new delivery solutions are needed to target additional organs. Here we show that conjugation of 2'-O-hexadecyl (C16) to siRNAs enables safe, potent and durable silencing in the central nervous system (CNS), eye and lung in rodents and non-human primates with broad cell type specificity. We show that intrathecally or intracerebroventricularly delivered C16-siRNAs were active across CNS regions and cell types, with sustained RNA interference (RNAi) activity for at least 3 months. Similarly, intravitreal administration to the eye or intranasal administration to the lung resulted in a potent and durable knockdown. The preclinical efficacy of an siRNA targeting the amyloid precursor protein was evaluated through intracerebroventricular dosing in a mouse model of Alzheimer's disease, resulting in amelioration of physiological and behavioral deficits. Altogether, C16 conjugation of siRNAs has the potential for safe therapeutic silencing of target genes outside the liver with infrequent dosing.