Retinal ganglion cell and microvascular density loss in hereditary spastic paraplegia

Background

Hereditary spastic paraplegia (HSP) is characterized by progressive degeneration of distal axons in the long corticospinal tracts. Loss of retinal cells and microvascular networks has neither been suspected nor investigated. We concurrently examined the retinal microvasculature and retinal layer morphology in patients with HSP to assess whether retinal features may portray disease and its progression.

Methods

Fifteen patients with HSP and 30 healthy controls were included in this cross-sectional case-control study. Disease severity was assessed with the Spastic Paraplegia Rating Scale (SPRS). Severity of ataxia was determined by the Scale for the Assessment and Rating of Ataxia (SARA). Retinal microvasculature was measured by means of optical coherence tomography angiography (OCT-A) and morphology of retinal layers using structural OCT. Mixed-effects models were applied for data analysis.

Results

HSP patients showed significantly reduced vessel density of the superficial vascular plexus (SVP), reduced ganglion cell layer (GCL) volume, reduced inner plexiform layer (IPL) volume and reduced temporal-inferior peripapillary retinal nerve fiber layer (pRNFL) thickness versus healthy controls. GCL volume reduction correlated significantly with the worsening of visual acuity and higher SARA scores.

Conclusions

These findings demonstrate that, in HSP both cells and vascular networks of the retina are compromised. Assessment of the retinal GCL, IPL and SVP may aid in diagnosis and monitoring of disease progression as well as provide novel structural outcome measures for clinical trials.

Short-term outcomes in patients with center-involving diabetic macular edema after a single dose of intravitreal bevacizumab

Background

A significant portion of diabetic macular edema (DME) is refractory to anti-vascular endothelial growth factor (anti-VEGF) agents. This study investigates morphological and functional outcomes to a single intravitreal bevacizumab (IVB) injection in patients with center-involving DME (ciDME) at 4–6 weeks and compares treatment responders and non-responders based on spectral domain optical coherence tomography (SD-OCT) features.

Methods

IRB approved observational, retrospective chart review of patients with ciDME, identified by ICD-10 code, who received IVB and underwent baseline and 4–6 weeks follow-up SD-OCT imaging between January 1, 2016 and January 19, 2021. Patients who had received previous treatment with anti-VEGF or intraocular steroids within 1 year were excluded. Variables included best-corrected visual acuity (BCVA), central subfield thickness (CST) and total macular volume (TMV). Eyes were classified as responders if CST reduction was greater than 10%. OCT scans were graded qualitatively by two masked graders using Imagivault software. Paired Student’s t-tests, Wilcoxon signed rank tests and Chi-Square tests were used for analysis.

Results

A total of 334 prospective subjects were identified, and after applying exclusion criteria 52 eyes from 46 patients (mean age 64.22 ± 8.12 years, 58.7% male) were included. Mean BCVA did not significantly change with treatment, 63.9 ETDRS letters (~ 20/50) at baseline and 65.9 ETDRS letters (~ 20/50) post-treatment (p = 0.07). Mean CST decreased from 466 ± 123 μm at baseline to 402 ± 86 μm post-treatment (p < 0.001). 22 (42.3%) of eyes were categorized as responders and 30 (57.7%) as non-responders. Average change in CST from baseline in responders was -164 μm (p < 0.001) and + 9 μm in non-responders (p = 0.47). Vitreomacular adhesion (VMA) was more prevalent in non-responders (28.7% vs. 4.8%, p = 0.03). In addition, cyst location in the inner nuclear layer (INL) was present more frequently in responders (95.5% vs. 73.3%, p = 0.037) as was subretinal fluid (45.5% vs. 13.3%, p = 0.01).

Conclusion

The short-term response to a single IVB was sub-optimal with structural but no functional improvements. Greater baseline CST, presence of INL cysts and subretinal fluid may represent factors indicative of a better treatment response.

Structural retinal changes in cerebral small vessel disease

Cerebral small vessel disease (CSVD) is an important contributor to cognitive impairment and stroke. Previous research has suggested associations with alterations in single retinal layers. We have assessed changes of all individual retinal layers in CSVD using high-resolution optical coherence tomography (OCT) for the first time. Subjects with recent magnetic resonance imaging (MRI) underwent macular and peripapillary retinal imaging using OCT for this case-control study. Number and volume ratio index (WMRI) of white matter lesions (WML) were determined on MRI. Data were analyzed using multiple linear regression models. 27 CSVD patients and 9 control participants were included. Ganglion cell layer (GCL) volume was significantly reduced in patients with CSVD compared to age-matched controls (p = 0.008). In patients with CSVD, larger foveal outer plexiform layer (OPL) volume and decreased temporal peripapillary retinal nerve fiber layer (RNFL) thickness were significantly associated with a higher WMRI in linear regression when controlling for age (p ≤ 0.033). Decreased foveal GCL volume and temporal-inferior RNFL thickness at Bruch's membrane opening (MRW), and increased temporal MRW were associated with a higher WML burden (p ≤ 0.037). Thus, we identified alterations in several OCT layers in individuals with CSVD (GCL, OPL, MRW and RNFL). Their potential diagnostic value merits further study.

Microvascular Breakdown Due to Retinal Neurodegeneration in Ataxias

BACKGROUND

Neurodegenerative ataxias are devastating disorders of the cerebellum and spinal cord, accompanied by death of retinal ganglion cells, leading to relentlessly progressive decline of motor coordination and permanent disability. Retinal microvascular affection has not yet been determined.

OBJECTIVES

The aim of this study is to assess whether retinal microvascular alterations occur and, if so, whether they are concurrent with or follow cell death in the retina in neurodegenerative diseases.

METHODS

This study involves the cross-sectional observational study of 43 patients with ataxia and 43 controls enrolled from August 1, 2018, to September 30, 2020. The extent of ataxia was determined by the Scale for the Assessment and Rating of Ataxia. Changes in retinal vasculature were examined by optical coherence tomography angiography (OCT-A) and retinal cell and fiber density by OCT in ataxias concurrently.

RESULTS

When comparing the ataxia cohort with healthy subjects, ataxia patients exhibited reduced vessel density in the radial peripapillary capillary (RPC) network (P = 0.005), capillary density inside the optic nerve head (cdONH) (P < 0.001), nasal superficial vascular plexus (P = 0.03) as well as reduced ganglion cell layer (GCL) volume (P = 0.04), and temporal peripapillary retinal nerve fiber layer thickness (P = 0.04). Mixed effect analysis modeling laterality confirmed these findings.

CONCLUSIONS

These findings demonstrate a distinct pattern of concurrent changes in vessel density of the retinal superficial vascular complex, encompassing the superficial vascular plexus, RPC network and cdONH, and retinal GCL volume, providing new insights into the ongoing degeneration in ataxias. Our findings may have relevance for design of novel therapeutic approaches for ataxias and possibly other neurodegenerative diseases.

AhR and IDO1 in pathogenesis of Covid-19 and the "Systemic AhR Activation Syndrome:" a translational review and therapeutic perspectives

Covid-19 is the acute illness caused by SARS-CoV-2 with initial clinical symptoms such as cough, fever, malaise, headache, and anosmia. After entry into cells, corona viruses (CoV) activate aryl hydrocarbon receptors (AhRs) by an indoleamine 2,3-dioxygenase (IDO1)-independent mechanism, bypassing the IDO1-kynurenine-AhR pathway. The IDO1-kynurenine-AhR signaling pathway is used by multiple viral, microbial and parasitic pathogens to activate AhRs and to establish infections. AhRs enhance their own activity through an IDO1-AhR-IDO1 positive feedback loop prolonging activation induced by pathogens. Direct activation of AhRs by CoV induces immediate and simultaneous up-regulation of diverse AhR-dependent downstream effectors, and this, in turn, results in a "Systemic AhR Activation Syndrome" (SAAS) consisting of inflammation, thromboembolism, and fibrosis, culminating in multiple organ injuries, and death. Activation of AhRs by CoV may lead to diverse sets of phenotypic disease pictures depending on time after infection, overall state of health, hormonal balance, age, gender, comorbidities, but also diet and environmental factors modulating AhRs. We hypothesize that elimination of factors known to up-regulate AhRs, or implementation of measures known to down-regulate AhRs, should decrease severity of infection. Although therapies selectively down-regulating both AhR and IDO1 are currently lacking, medications in clinical use such as dexamethasone may down-regulate both AhR and IDO1 genes, as calcitriol/vitamin D3 may down-regulate the AhR gene, and tocopherol/vitamin E may down-regulate the IDO1 gene. Supplementation of calcitriol should therefore be subjected to epidemiological studies and tested in prospective trials for prevention of CoV infections, as should tocopherol, whereas dexamethasone could be tried in interventional trials. Because lack of physical exercise activates AhRs via the IDO1-kynurenine-AhR signaling pathway increasing risk of infection, physical exercise should be encouraged during quarantines and stay-at-home orders during pandemic outbreaks. Understanding which factors affect gene expression of both AhR and IDO1 may help in designing therapies to prevent and treat humans suffering from Covid-19.

Mild hypothermia ameliorates anesthesia toxicity in the neonatal macaque brain

Sedatives and anesthetics can injure the developing brain. They cause apoptosis of neurons and oligodendrocytes, impair synaptic plasticity, inhibit neurogenesis and trigger long-term neurocognitive deficits. The projected vulnerable period in humans extends from the third trimester of pregnancy to the third year of life. Despite all concerns, there is no ethically and medically acceptable alternative to the use of sedatives and anesthetics for surgeries and painful interventions. Development of measures that prevent injury while allowing the medications to exert their desired actions has enormous translational value. Here we investigated protective potential of hypothermia against histological toxicity of the anesthetic sevoflurane in the developing nonhuman primate brain. Neonatal rhesus monkeys underwent sevoflurane anesthesia over 5 h. Body temperature was regulated in the normothermic (>36.5 °C), mild hypothermic (35-36.5 °C) and moderately hypothermic (<35 °C) range. Animals were euthanized at 8 h and brains examined immunohistochemically (activated caspase 3) and stereologically to quantify apoptotic neuronal and oligodendroglial death. Sevoflurane anesthesia was well tolerated at all temperatures, with oxygen saturations, end tidal CO2 and blood gases remaining at optimal levels. Compared to controls, sevoflurane exposed brains displayed significant apoptosis in gray and white matter affecting neurons and oligodendrocytes. Mild hypothermia (35-36.5 °C) conferred significant protection from apoptotic brain injury, whereas moderate hypothermia (<35 °C) did not. Hypothermia ameliorates anesthesia-induced apoptosis in the neonatal primate brain within a narrow temperature window (35-36.5 °C). Protection is lost at temperatures below 35 °C. Given the mild degree of cooling needed to achieve significant brain protection, application of our findings to humans should be explored further.

Awareness of Age-Related Macular Degeneration in Community-Dwelling Elderly Persons in Germany

Background: Due to current demographic trends age-related macular degeneration (AMD) is becoming more prevalent. When disease progresses to late-stage neovascular AMD, rapid initiation of treatment is required to achieve optimal outcomes. However, many affected individuals may be unaware of their disease impeding and delaying care seeking. Therefore, in an exploratory study we assessed whether elderly persons living independently in the community were aware of their AMD. Methods: Participants were recruited in eleven seniors' community centers. Participants underwent a standardized interview followed by non-mydriatic fundus photography of the macula and the optic disc in both eyes (Canon CR-2AF, Canon, New York, USA). The images were graded by an ophthalmologist and the data were analyzed descriptively. Results: A total of 281 participants (73.9 ± 8.1 years; 71.9% women) underwent bilateral fundus photography. The fundus photographs of 208 participants (74%; 73.6 ± 7.0 years; 73.1% women) could be graded. In a third (32.2%, n = 67) no pathological changes were detected. AMD was present in 24.5% of the examined subjects (n = 51). Half of the cases had early (47.1%), followed by intermediate (41.2%) and late (11.7%) AMD. Only one third (n = 16, 31.4%) were aware of their disease. Conclusions: A quarter of community dwelling elderly had AMD but only a third of these were aware of being affected with AMD. This confirms previous studies demonstrating low awareness for age-related eye diseases in the community. Considering the increase in population aging, awareness campaigns for AMD are needed.

Extended Multiple-Field High-Definition transcranial direct current stimulation (HD-tDCS) is well tolerated and safe in healthy adults

BACKGROUND

High definition transcranial direct current stimulation (HD-tDCS) has been administered over single brain regions for small numbers of sessions. Safety, feasibility and tolerability of HD-tDCS over multiple brain regions, multiple daily stimulations and long periods are not established.

OBJECTIVE

We studied safety, feasibility and tolerability of daily HD-tDCS over 2-4 brain regions for 20 sessions in healthy adults.

METHODS

Five healthy adults underwent physical and neurological examination, electrocardiogram (EKG), electroencephalogram (EEG) and cognitive screening (ImpACT) before, during and after HD-tDCS. Four networks (left/right temporoparietal and frontal) were stimulated in sequence (20 min each) using HD-tDCS in 20 daily sessions. Sessions 1-10 included sequential stimulation of both temporoparietal networks, sessions 11-15 stimulations of 4 networks and sessions 16-20 two daily stimulation cycles of 4 networks/cycle (1.5 mA/network). Side effects, ImpACT scores and EEG power spectrum were compared before and after HD-tDCS.

RESULTS

All subjects completed the trial. Adverse events were tingling, transient redness at the stimulation site, perception of continuing stimulation after end of session and one self-resolving headache. EEG power spectrum showed decreased delta power in frontal areas several days after HD-tDCS. While at the group level ImpACT scores did not differ before and after stimulations, we found a trend for correlation between decreased EEG delta power and individual improvements in ImpACT scores after HD-tDCS.

CONCLUSION

Prolonged, repeat daily stimulation of multiple brain regions using HD-tDCS is feasible and safe in healthy adults. Preliminary EEG results suggest that HD-tDCS may induce long lasting changes in excitability in the brain.

Clemastine effects in rat models of a myelination disorder

BackgroundPelizaeus Merzbacher disease (PMD) is a dysmyelinating disorder of the central nervous system caused by impaired differentiation of oligodendrocytes. This study was prompted by findings that antimuscarinic compounds enhance oligodendrocyte differentiation and remyelination in vitro. One of these compounds, clemastine fumarate, is licensed for treatment of allergic conditions. We tested whether clemastine fumarate can promote myelination in two rodent PMD models, the myelin-deficient and the PLP transgenic rat.MethodsPups were treated with daily injections of clemastine (10-30 mg/kg/day) on postnatal days 1-21. Neurologic phenotypes and myelination patterns in the brain, optic nerves, and spinal cords were assessed using histological techniques.ResultsNo changes in neurological phenotype or survival were observed even at the highest dose of clemastine. Postmortem staining with Luxol fast blue and myelin basic protein immunohistochemistry revealed no evidence for improved myelination in the CNS of treated rats compared to vehicle-treated littermates. Populations of mature oligodendrocytes were unaffected by the treatment.ConclusionThese results demonstrate lack of therapeutic effect of clemastine in two rat PMD models. Both models have rapid disease progression consistent with the connatal form of the disease. Further studies are necessary to determine whether clemastine bears a therapeutic potential in milder forms of PMD.