Comparative Ocular Anatomy in Commonly Used Laboratory Animals

AI and early diagnostics: mapping fetal facial expressions through development, evolution, and 4D ultrasound

The development of facial musculature and expressions in the human fetus represents a critical intersection of developmental biology, neurology, and evolutionary anthropology, offering insights into early neurological and social development. Fetal facial expressions, shaped by Cranial Nerve VII, reflect evolutionary adaptations for nonverbal communication and exhibit minimal asymmetry in universal expressions. Advancements in 4D ultrasound imaging and artificial intelligence (AI) have introduced innovative methods for analyzing these movements, revealing their potential as diagnostic tools for neurodevelopmental disorders like Bell's Palsy and Ramsay Hunt Syndrome before birth. These technologies promise early interventions that could significantly improve neonatal outcomes. By integrating imaging, AI, and longitudinal studies, researchers propose a multidisciplinary approach to establish diagnostic criteria for fetal facial movements. However, translating these advancements into clinical practice requires addressing ethical and practical challenges, refining imaging and AI methodologies, and fostering interdisciplinary collaboration. The review highlights the universality of fetal expressions while emphasizing the importance of distinguishing typical variability from pathological markers. In conclusion, these findings suggest transformative potential for maternal-fetal medicine, paving the way for proactive strategies to manage neurodevelopmental risks. Focused research is essential to fully harness these innovations and establish a new frontier in perinatal science.

Recent advances and strategies for nanocarrier-mediated topical therapy and theranostic for posterior eye disease

Posterior eye disorders, such as age-related macular degeneration, diabetic retinopathy, and glaucoma, have a significant impact on human quality of life and are the primary cause of age-related retinal diseases among adults. There is a pressing need for innovative topical approaches to treat posterior eye disorders, as current methods often rely on invasive procedures with inherent risks. Limited success was attained in the realm of topical ophthalmic delivery through non-invasive means. Additionally, there exists a dearth of literature that delves into the potential of this approach for drug delivery and theranostic purposes, or that offers comprehensive design strategies for nanocarrier developers to surmount the significant physiological ocular barriers. This review offers a thorough and up-to-date state-of-the-art overview of 40 studies on therapeutic loaded nanocarriers and theranostic devices that, to the best of our knowledge, represent all successful works that reached posterior eye segments through a topical non-invasive administration. Most importantly, based on the successful literature studies, this review provides a comprehensive summary of the potential design strategies that can be implemented during nanocarrier development to overcome each ocular barrier.

AA, Kulkarni V, Oh Y, Xia S, Ding Z, Han H, Anders N, Rudek MA, Chow W, Stark W, Ensign LM, Hanes J, Xu Q. Six-month effective treatment of corneal graft rejection

Topical corticosteroid eye drop is the mainstay for preventing and treating corneal graft rejection. While the frequent topical corticosteroid use is associated with risk of intraocular pressure (IOP) elevation and poor patient compliance that leads to graft failure and the requirement for a repeated, high-risk corneal transplantation. Here, we developed dexamethasone sodium phosphate (DSP)-loaded dicarboxyl-terminated poly(lactic acid) nanoparticle (PLA DSP-NP) formulations with relatively high drug loading (8 to 10 weight %) and 6 months of sustained intraocular DSP delivery in rats with a single dosing. PLA DSP-NP successfully reversed early signs of corneal rejection, leading to rat corneal graft survival for at least 6 months. Efficacious PLA DSP-NP doses did not affect IOP and showed no signs of ocular toxicity in rats for up to 6 months. Subconjunctival injection of DSP-NP is a promising approach for safely preventing and treating corneal graft rejection with the potential for improved patient adherence.

Scientific and Regulatory Policy Committee Points to Consider: Fixation, Trimming, and Sectioning of Nonrodent Eyes and Ocular Tissues for Examination in Ocular and General Toxicity Studies

A Working Group of the Society of Toxicologic Pathology's Scientific and Regulatory Policy Committee conducted a technical and scientific review of current practices relating to the fixation, trimming, and sectioning of the nonrodent eye to identify key points and species-specific anatomical landmarks to consider when preparing and evaluating eyes of rabbits, dogs, minipigs, and nonhuman primates from ocular and general toxicity studies. The topics addressed in this Points to Consider article include determination of situations when more comprehensive evaluation of the globe and/or associated extraocular tissues should be implemented (expanded ocular sampling), and what constitutes expanded ocular sampling. In addition, this manuscript highlights the practical aspects of fixing, trimming, and sectioning the eye to ensure adequate histopathological evaluation of all major ocular structures, including the cone-dense areas (visual streak/macula/fovea) of the retina for rabbits, dogs, minipigs, and nonhuman primates, which is a current regulatory expectation for ocular toxicity studies.[Box: see text].

Mucosa-Associated Lymphoid Tissue and Tertiary Lymphoid Structures of the Eye and Ear in Laboratory Animals

Mucosa-associated lymphoid tissue (MALT) of special senses is poorly described and can be confused with nonspecific mononuclear cell infiltrates and tertiary lymphoid structures (TLS). In the eye, MALT consists mostly of conjunctiva-associated lymphoid tissue (CALT) and lacrimal drainage-associated lymphoid tissue (LDALT). In humans, CALT and LDALT are important components of the normal eye-associated lymphoid tissue (EALT), but EALT is less frequently described in ocular tissues of animals. The EALT are acquired postnatally in preferential mucosal sites, expand with antigenic exposure, form well-developed lymphoid follicles, and are reported to senesce. Lymphoid follicles that are induced concurrently with chronic inflammation are more appropriately considered TLS but must be differentiated from inflammation in MALT. Less understood is the etiology for formation of lymphoid tissue aggregates in the ciliary body, limbus, or choroid of healthy eyes in animals and humans. In the healthy eustachian tube and middle ear of animals and humans, MALT may be present but is infrequently described. Concurrent with otitis media, lymphoid follicles in the eustachian tube are probably expanded MALT, but lymphoid follicles in the middle ear may be TLS. The purpose of this comparative review is to familiarize toxicologic pathologists with MALT in the special senses and to provide considerations for differentiating and reporting eye and ear MALT from immune or inflammatory cell infiltrates or inflammation in nonclinical studies, and the circumstances for reporting TLS in compartments of the eye and ear.

Intravitreal Administration of Acetyl Triethyl Citrate and Benzyl Benzoate Is Retinotoxic in Rabbits but Not in Cynomolgus Monkeys

Sustained drug delivery formulations are developed to reduce dose frequency while maintaining efficacy of intravitreal (ITV) administered therapeutics. Available safety data for components novel to the eye's posterior segment may be limited, requiring preclinical assessments to identify potential toxicities. We evaluated the in vivo and in vitro safety of two solvents, acetyl triethyl citrate (ATEC) and benzyl benzoate (BB), as novel sustained delivery formulations for ITV administration. In vivo tolerability was assessed following ITV administration of ATEC and BB to rabbits and cynomolgus monkeys. In rabbits, ITV solvent administration resulted in moderate to severe retinal toxicity characterized by focal retinal necrosis and/or degeneration, sometimes accompanied by inflammation, with a clear association between the physical presence of the solvent and areas of retinal damage. In contrast, solvent administration in monkeys appeared well tolerated, producing no histologic abnormalities. Toxicity in primary human retinal pigment epithelial cells, characterized by cellular toxicity and mitochondrial injury, corroborated the retinal toxicity in rabbits. In conclusion, ITV solvent depots of ATEC or BB result in chemical and focal retinal toxicity in rabbits, but not monkeys. Additional investigation is needed to demonstrate a sufficient margin of safety prior to use of ATEC or BB in ITV drug products.

Histological Features of Postnatal Development of the Eye in White Rabbits

Rabbits are frequently used in studies assessing the toxicity of ophthalmic drugs; however, the postnatal histological changes that occur in the rabbit eye have not been fully described. To characterize postnatal ocular development in white rabbits, a histological investigation of the eyes and eyelids was sequentially performed between postnatal days (PNDs) 1 and 42. The eyes opened during PNDs10 to 12. Significant changes prior to eyelid opening included the proliferation of uveal and optic nerve cells, regression of the lenticular vasculature, and thinning of the retina with a decreasing number of retinal cells. After eyelid opening, several significant changes occurred in the anterior segment, including thickening of the cornea and the development of lacrimation-related tissues in the eyelid and conjunctiva. Additionally, the differentiation of retinal layer-derived cells and optic nerve thickening occurred. The lens size continued to increase throughout the postnatal period. The histological structure of the eyes and eyelids was nearly mature by PNDs28 to 42. This study characterizes the postnatal changes in the histological features of the eyes in juvenile white rabbits, providing fundamental knowledge on the appropriate design of histological studies of the eyes in juvenile rabbits, particularly ophthalmic drug evaluations.

Therapeutic targeting of the RB1 pathway in retinoblastoma with the oncolytic adenovirus VCN-01

Retinoblastoma is a pediatric solid tumor of the retina activated upon homozygous inactivation of the tumor suppressor RB1 VCN-01 is an oncolytic adenovirus designed to replicate selectively in tumor cells with high abundance of free E2F-1, a consequence of a dysfunctional RB1 pathway. Thus, we reasoned that VCN-01 could provide targeted therapeutic activity against even chemoresistant retinoblastoma. In vitro, VCN-01 effectively killed patient-derived retinoblastoma models. In mice, intravitreous administration of VCN-01 in retinoblastoma xenografts induced tumor necrosis, improved ocular survival compared with standard-of-care chemotherapy, and prevented micrometastatic dissemination into the brain. In juvenile immunocompetent rabbits, VCN-01 did not replicate in retinas, induced minor local side effects, and only leaked slightly and for a short time into the blood. Initial phase 1 data in patients showed the feasibility of the administration of intravitreous VCN-01 and resulted in antitumor activity in retinoblastoma vitreous seeds and evidence of viral replication markers in tumor cells. The treatment caused local vitreous inflammation but no systemic complications. Thus, oncolytic adenoviruses targeting RB1 might provide a tumor-selective and chemotherapy-independent treatment option for retinoblastoma.

Transscleral cyclophotocoagulation and its histological effects on the conjunctiva

Micropulse transscleral cyclophotocoagulation (MP-TCP) is increasingly being used as an initial procedure prior to conjunctival filtration surgeries. However, it is uncertain whether MP-TCP may cause inflammation and scarring of the bulbar conjunctiva. Thus, we aimed to study the histological effects of MP-TCP (compared to controls and continuous wave [CW]-TCP) on the conjunctiva. Our study included 10 Dutch Belted Rabbits that underwent TCP in their right eyes (n = 5, MP-TCP; n = 5, CW-TCP), while their left eyes served as controls. The rabbits were euthanised at 4 weeks, and their dissected globes underwent histopathological and immunohistochemical examination. We observed greater conjunctival inflammation in MP-TCP or CW-TCP-treated eyes compared to controls, but not between each other. The majority of the lymphocytic infiltrates were CD4 T-cells. Increased conjunctival fibrosis was evident in MP-TCP or CW-TCP-treated eyes, to similar extents, compared to controls. However, the increased staining for myofibroblasts was not statistically significant in TCP-treated eyes. We concluded that MP-TCP causes significantly greater overall conjunctival inflammation and scarring compared to controls, similar to CW-TCP. As these are risk-factors for fibrosis and failure of the conjunctival bleb, further studies are required to explore the effect, if any, of post-TCP conjunctival changes on future bleb morphology and survival.

Ocular safety assessment of sodium iodate in cynomolgus monkeys

Although sodium iodate (NaIO3)-induced retinal injury model has been widely used in rodents, its application in large animal species has encountered variation in retinal toxicity. NaIO3 induced retinal degeneration and functional changes in sheep, but not in swine. In monkeys, administration of NaIO3 via a carotid artery affected only the cell function of ipsilateral retinal pigment epithelium. The aim of the present study was to identify the dosage and route of NaIO3 administration resulting in morphologic and functional retinal changes in cynomolgus monkeys. Separate groups of animals received NaIO3 intravenously in three different dosing paradigms. Vehicle control animals received phosphate-buffered saline. At selected time points following dosing, flash electroretinograms (ERGs) were recorded followed by necropsy. The eyes were examined microscopically post-necropsy and the levels of circulating microRNA-183 cluster were evaluated in the blood samples collected on days 1, 4, and 5 postdose. A statistically significant reduction in both scotopic a-wave and scotopic and photopic b-wave signals ( p < 0.05) were observed between the ERG signals acquired from NaIO3-treated and vehicle control animals, coupled with time-dependent elevations in plasma miR-183 cluster. Mild to moderate retinal degeneration was observed in the outer layer of the retina, which correlated well with the functional and clinical observations. There were no statistically significant differences in scotopic oscillatory potentials. These findings suggest that intravenous injection of sublethal NaIO3 markedly damaged the cone and rod photoreceptors both functionally and morphologically, and plasma miR-183 reflected the retinal toxicity in those animals with moderate retinal damage.

General considerations in ocular toxicity risk assessment from the toxicologists' viewpoints

Humans commonly obtain approximately 80% of external information from vision. Since loss of vision markedly decreases quality of life, risk assessments for visual toxicity of new drugs are extremely important. However, the ICH S4 guideline for nonclinical toxicity study of new drugs only indicates a brief instruction for ophthalmologic examinations, and submitted data for drug approval according only to this guideline are not always considered sufficient in light of ocular toxicity risk assessments. The eye is an assembly of many specialized sub-organs which have specific functions, and its integral maintenance of homeostasis plays an important role of visual function. When only a part of integrity of functions is lost, overall function of the eye might be commonly disturbed. Therefore, understanding of anatomy and physiology of these sub-organs may help know mechanisms of observed ocular changes. In ophthalmologic examinations in nonclinical toxicity studies, it is vital to understand the principles and features of each examination. Comparisons of findings between pre and post drug treatment as well as considerations of species differences, strain differences, age differences, and location/degree of abnormalities are essential. In addition, many kinds of spontaneous ocular findings are well known in experimental animals. To differentiate treatment-related changes from spontaneous findings, mastering basic skills for ophthalmologic examinations and taking advantage of collection of background data are necessary. For ocular toxicity risk assessments, while an evaluation of "sight-threatening" effects is most critical matter, "quality of vision" related findings also should be considered. To extrapolate animal data to human, clinical significances of ocular toxicity findings should be evaluated based on considerations for "species differences", "safety margins", "reversibility", and "risk-benefit balance". In addition, a detailed recording of features of lesions is also important for an appropriate judgment of clinical significance of ocular findings. For preparation of histopathological specimens, careful sampling of organs and suitable selection of fixatives are important. To accurately orient ocular lesions in the specimen for histopathological examinations, securing close communications prior to necropsy among ophthalmologists, gross necropsy pathologists and histopathology technicians should be effective and helpful. It is impossible to detect all ocular changes in histopathological examinations; that is, there is a limitation in histopathological examinations. Therefore, for ocular toxicity risk assessments, comprehensive evaluation with pathological findings as well as other results of various examinations in toxicity studies should be considered. In conclusion, for ocular toxicity risk assessments, integrated judgments from all examination data in nonclinical toxicity studies are required. To achieve appropriate risk assessments which can be extrapolated to human, close communications and sharing of data regarding the eye are most important among toxicologists, clinical sign investigators, histopathology technicians and pathologists.