Biological Correlations and Confounders for Quantification of Retinal Ganglion Cells by Optical Coherence Tomography Based on Studies of Outbred Mice.

Purpose: Despite popularity of optical coherence tomography (OCT) in glaucoma studies, it's unclear how well OCT-derived metrics compare to traditional measures of retinal ganglion cell (RGC) abundance. Here, Diversity Outbred (J:DO) mice are used to directly compare ganglion cell complex (GCC) thickness measured by OCT to metrics of retinal anatomy measured ex vivo with retinal wholemounts and optic nerve histology. Methods: J:DO mice (n = 48) underwent fundoscopic and OCT examinations, with automated segmentation of GCC thickness. RGC axons were quantified from para-phenylenediamine-stained optic nerve cross-sections and somas from BRN3A-immunolabeled retinal wholemounts, with total inner retinal cellularity assessed by TO-PRO and subsequent hematoxylin staining. Results: J:DO tissues lacked overt disease. GCC thickness, RGC abundance, and total cell abundance varied broadly across individuals. GCC thickness correlated significantly to RGC somal density (r = 0.58) and axon number (r = 0.44), but not total cell density. Retinal area and nerve cross-sectional area varied widely. No metrics were significantly influenced by sex. In bilateral comparisons, GCC thickness (r = 0.95), axon (r = 0.72), and total cell density (r = 0.47) correlated significantly within individuals. Conclusions: Amongst outbred mice, OCT-derived measurements of GCC thickness correlate significantly to RGC somal and axon abundance. Factors limiting correlation are likely both biological and methodological, including differences in retinal area that distort sampling-based estimates of RGC abundance. Translational Relevance: There are significant-but imperfect-correlations between GCC thickness and RGC abundance across genetic contexts in mice, highlighting valid uses and ongoing challenges for meaningful use of OCT-derived metrics.

Quantification and image-derived phenotyping of retinal ganglion cell nuclei in the nee mouse model of congenital glaucoma.

The nee mouse model exhibits characteristic features of congenital glaucoma, a common cause of childhood blindness. The current study of nee mice had two components. First, the time course of neurodegeneration in nee retinal flat-mounts was studied over time using a retinal ganglion cell (RGC)-marker, BRN3A; a pan-nuclear marker, TO-PRO-3; and H&E staining. Based on segmentation of nuclei using ImageJ and RetFM-J, this analysis identified a rapid loss of BRN3A+ nuclei from 4 to 15 weeks of age, with the first statistically significant difference in average density compared to age-matched controls detected in 8-week-old cohorts (49% reduction in nee). Consistent with a model of glaucoma, no reductions in BRN3A- nuclei were detected, but the combined analysis indicated that some RGCs lost BRN3A marker expression prior to actual cell loss. These results have a practical application in the design of experiments using nee mice to study mechanisms or potential therapies for congenital glaucoma. The second component of the study pertains to a discovery-based analysis of the large amount of image data with 748,782 segmented retinal nuclei. Using the automatedly collected region of interest feature data captured by ImageJ, we tested whether RGC density of glaucomatous mice was significantly correlated to average nuclear area, perimeter, Feret diameter, or MinFeret diameter. These results pointed to two events influencing nuclear size. For variations in RGC density above approximately 3000 nuclei/mm2 apparent spreading was observed, in which BRN3A- nuclei-regardless of genotype-became slightly larger as RGC density decreased. This same spreading occurred in BRN3A+ nuclei of wild-type mice. For variation in RGC density below 3000 nuclei/mm2, which only occurred in glaucomatous nee mutants, BRN3A+ nuclei became smaller as disease was progressively severe. These observations have relevance to defining RGCs of relatively higher sensitivity to glaucomatous cell death and the nuclear dynamics occurring during their demise.

Recombinant adenovirus causes prolonged mobilization of macrophages in the anterior chambers of mice.

PURPOSE: Ocular tissues of mice have been studied in many ways using replication-deficient species C type 5 adenovirus (Ad5) as a tool for manipulating gene expression. Whereas refinements to injection protocols and tropism have led to several advances in targeting cells of interest, there remains a relative lack of information concerning how Ad5 may influence other ocular cell types capable of confounding experimental interpretation. Here, a slit lamp is used to thoroughly photodocument the sequelae of intraocular Ad5 injections over time in mice, with attention to potentially confounding indices of inflammation. METHODS: A cohort of C57BL/6J mice was randomly split into three groups (Virus, receiving unilateral intracameral injection with 5×107 plaque-forming units (pfu) of a cargo-less Ad5 construct; Saline, receiving unilateral balanced salt solution injection; and Naïve, receiving no injections). From this initial experiment, a total of 52 eyes from 26 mice were photodocumented via slit lamp at four time points (baseline and 1, 3, and 10 weeks following initiation of the experiment) by an observer masked to treatments and other parameters of the experimental design. Following the last in vivo exam, tissues were collected. Based on the slit-lamp data, tissues were studied via immunostaining with the macrophage marker F4/80. Subsequently, three iterations of the original experiment were performed with otherwise identical experimental parameters testing the effect of age, intravitreal injection, and A195 buffer, adding slit-lamp photodocumentation of an additional 32 eyes from 16 mice. RESULTS: The masked investigator could use the sequential images from each mouse in the initial experiment to assign each mouse to its correct treatment group with near perfect fidelity. Virus-injected eyes were characterized by corneal damage indicative of intraocular injection and a prolonged mobilization of clump cells on the surface of the iris. Saline-injected eyes had only transient corneal opacities indicative of intraocular injections, and Naïve eyes remained normal. Immunostaining with F4/80 was consistent with ascribing the clump cells visualized via slit-lamp imaging as a type of macrophage. Experimental iterations using Ad5 indicate that all virus-injected eyes had the distinguishing feature of a prolonged presence of clump cells on the surface of the iris regardless of injection site. Mice receiving an intraocular injection of Ad5 at an advanced age displayed a protracted course of corneal cloudiness that prevented detailed visualization of the iris at the last time point. CONCLUSIONS: Because the eye is often considered an "immune privileged site," we suspect that several studies have neglected to consider that the presence of Ad5 in the eye might evoke strong reactions from the innate immune system. Ad5 injection caused a sustained mobilization of clump cells-that is, macrophages. This change is likely a consequence of either direct macrophage transduction or a secondary response to cytokines produced locally by other transduced cells. Regardless of how these cells were altered, the important implication is that the adenovirus led to long-lasting changes in the environment of the anterior chamber. Thus, these findings describe a caveat of Ad5-mediated studies involving macrophage mobilization, which we encourage groups to use as a bioassay in their experiments and consider in interpretation of their ongoing experiments using adenoviruses.

Acute Ischemic Stroke and COVID-19: Experience From a Comprehensive Stroke Center in Midwest US.

Background: COVID-19 has been associated with increased risk of venous and arterial thromboembolism including ischemic stroke. We report on patients with acute ischemic stroke and concomitant COVID-19 in a diverse patient population. Methods: This is a retrospective analysis of patients hospitalized with acute ischemic stroke (AIS) and COVID-19 to our comprehensive stroke center in Chicago, IL, between March 1, 2020, and April 30, 2020. We reviewed stroke characteristics, etiologies, and composite outcomes. We then compared our cohort with historic patients with AIS without COVID-19 admitted in the same time frame in 2019 and 2020. Results: Out of 13 patients with AIS and COVID-19, Latinos and African-Americans compromised the majority of our cohort (76.8%), with age ranging from 31-80 years. Most strokes were cortical (84.6%) and more than 50% of patients had no identifiable source, and were categorized as embolic stroke of unknown source (ESUS). A trend toward less alteplase administration was noted in the COVID-19 stroke patients compared to the non-COVID group from 2020 and 2019 (7.1 vs. 20.7% p 0.435 and 7.1 vs. 27.2% p 0.178). Endovascular thrombectomy was performed in 3 (23%) patients. Systemic thrombotic complications occurred in 3 (23%) COVID-19 AIS patients. Median National Institutes of Health Stroke Scale and modified Rankin Scale at discharge were 11 (IQR 4-23) and 4 (IQR 3-4), respectively. In the logistic regression model corrected for age and sex, COVID-19 was associated with discharge to mRS > 2 (p 0.046, OR 3.82, CI 1.02-14.3). Eight patients (63.8%) were discharged home or to acute rehabilitation, and two deceased from COVID-19 complications. Conclusion: AIS in the setting of COVID-19 is associated with worse outcomes, especially among African-American and Latino populations. Large vessel disease with ESUS was common suggesting an increased risk of coagulopathy and endothelial dysfunction as a potential etiology.

Neurological manifestations and COVID-19: Experiences from a tertiary care center at the Frontline.

OBJECTIVE: To report neurological manifestations seen in patients hospitalized with Coronavirus disease 2019 (COVID-19) from a large academic medical center in Chicago, Illinois. METHODS: We retrospectively reviewed data records of 50 patients with COVID-19 who were evaluated by the neurology services from March 1, 2020 - April 30, 2020. Patients were categorized into 2 groups based on timing of developing neurological manifestations: the "Neuro first" group had neurological manifestations upon initial assessment, and the "COVID first" group developed neurological symptoms greater than 24 h after hospitalization. The demographics, comorbidities, disease severity and neurological symptoms and diagnoses of both groups were analyzed. Statistical analysis was performed to compare the two groups. RESULTS: A total of 50 patients (48% African American and 24% Latino) were included in the analysis. Most common neurological manifestations observed were encephalopathy (n = 30), cerebrovascular disease (n = 20), cognitive impairment (n = 13), seizures (n = 13), hypoxic brain injury (n = 7), dysgeusia (n = 5), and extraocular movement abnormalities (n = 5). The "COVID-19 first" group had more evidence of physiologic disturbances on arrival with a more severe/critical disease course (83.3% vs 53.8%, p 0.025). CONCLUSION: Neurologic manifestations of COVID-19 are highly variable and can occur prior to the diagnosis of or as a complication of the viral infection. Despite similar baseline comorbidities and demographics, the COVID-19 patients who developed neurologic symptoms later in hospitalization had more severe disease courses. Differently from previous studies, we noted a high percentage of African American and Latino individuals in both groups.