Evaluation of visual function in Royal College of Surgeon rats using a depth perception visual cliff test

Effect of recurrent severe insulin-induced hypoglycemia on the cognitive function and brain oxidative status in the rats

BACKGROUND

Episodes of recurrent or severe hypoglycemia can occur in patients with diabetes mellitus, insulinoma, neonatal hypoglycemia, and medication errors. However, little is known about the short-term and long-term effects of repeated episodes of acute severe hypoglycemia on the brain, particularly in relation to hippocampal damage and cognitive dysfunction.

METHODS

Thirty-six wistar rats were randomly assigned to either the experimental or control group. The rats were exposed to severe hypoglycemia, and assessments were conducted to evaluate oxidative stress in brain tissue, cognitive function using the Morris water maze test, as well as histopathology and immunohistochemistry studies. The clinical and histopathological evaluations were conducted in the short-term and long-term.

RESULTS

The mortality rate attributed to hypoglycemia was 34%, occurring either during hypoglycemia or within 24 h after induction. Out of the 14 rats monitored for 7 to 90 days following severe/recurrent hypoglycemia, all exhibited clinical symptoms, which mostly resolved within three days after the last hypoglycemic episode, except for three rats. Despite the decrease in catalase activity in the brain, the total antioxidant capacity following severe insulin-induced hypoglycemia increased. The histopathology findings revealed that the severity of the hippocampal damage was higher compared to the brain cortex 90 days after hypoglycemia. Memory impairments with neuron loss particularly pronounced in the dentate gyrus region of the hippocampus were observed in the rats with severe hypoglycemia. Additionally, there was an increase in reactive astrocytes indicated by GFAP immunoreactivity in the brain cortex and hippocampus.

CONCLUSION

Recurrent episodes of severe hypoglycemia can lead to high mortality rates, memory impairments, and severe histopathological changes in the brain. While many histopathological and clinical changes improved after three months, it seems that the vulnerability of the hippocampus and the development of sustained changes in the hippocampus were greater and more severe compared to the brain cortex following severe and recurrent hypoglycemia. Furthermore, it does not appear that oxidative stress plays a central role in neuronal damage following severe insulin-induced hypoglycemia. Further research is necessary to assess the consequences of repeated hypoglycemic episodes on sustained damage across various brain regions.

Potential neuroprotective effect of stem cells from apical papilla derived extracellular vesicles enriched by lab-on-chip approach during retinal degeneration

Retinal degeneration (RD) is recognized as a frequent cause of visual impairments, including inherited (Retinitis pigmentosa) and degenerative (age-related macular) eye diseases. Dental stem cells (DSCs) have recently demonstrated a promising neuroprotection potential for ocular diseases through a paracrine manner carried out by extracellular vesicles (EVs). However, effective isolation of EVs is still challenging, and isolation methods determine the composition of enriched EVs and the subsequent biological and functional effects. In the present study, we assessed two enrichment methods (micro-electromechanical systems and ultrafiltration) to isolate the EVs from stem cells from apical papilla (SCAP). The size distribution of the corresponding isolates exhibited the capability of each method to enrich different subsets of EVs, which significantly impacts their biological and functional effects. We confirmed the neuroprotection and anti-inflammatory capacity of the SCAP-EVs in vitro. Further experiments revealed the possible therapeutic effects of subretinal injection of SCAP-EVs in the Royal College of Surgeons (RCS) rat model. We found that EVs enriched by the micro-electromechanical-based device (MEMS-EVs) preserved visual function, reduced retinal cell apoptosis, and prevented thinning of the outer nuclear layer (ONL). Interestingly, the effect of MEMS-EVs was extended to the retinal ganglion cell/retinal nerve fiber layer (GCL/RNFL). This study supports the use of the microfluidics approach to enrich valuable subsets of EVs, together with the choice of SCAP as a source to derive EVs for cell-free therapy of RD.

Effect of Applying Binocular Visual Training after Slanted Lateral Rectus Recession on Orthophoric Rate and Binocular Visual Function Recovery on Patients with Convergence Insufficiency-Type Intermittent Exotropia

OBJECTIVE

To explore the effect of applying binocular visual training after slanted lateral rectus recession on orthophoric rate and binocular visual function recovery on patients with convergence insufficiency-type intermittent exotropia (CI-IXT).

METHODS

A total of 76 CI-IXT child patients treated at the Strabismus and Pediatric Ophthalmology Department of our hospital from June 2019 to June 2020 were selected as the research objects, and those who met the inclusion criteria were equally divided into group A (63 eyes) and group B (61 eyes) according to the sealed envelope randomization. All child patients accepted the slanted lateral rectus recession, and after that, those in group A accepted the binocular visual training and those in group B accepted the conventional visual function rehabilitation training, so as to compare their position of eye, the best corrected visual acuity, etc., after training for statistical analysis.

RESULTS

Compared with group B after one month of surgery, group A had significantly less patients with grade I binocular vision function (P < 0.001) and more patients with grade II and III vision function (P < 0.05); between group A and group B, after 3 months and 6 months of treatment, the number of eyes with normal stereoscopic vision was significantly higher in group A (P < 0.05); at 15 days, 1 month, 3 months, and 6 months of treatment, the visual strain scores of group A were significantly lower (P < 0.001); after treatment, the number of orthophoria eyes was significantly higher in group A (P < 0.001), while the numbers of overcorrected eyes and undercorrected eyes were significantly higher in group B (P < 0.001); and the total incidence rate of adverse reactions was significantly lower in group A (P < 0.05).

CONCLUSION

Applying binocular visual training to child patients with CI-IXT after slanted lateral rectus recession can promote the recovery of binocular vision and ensure higher safety, and further study will help to establish a better solution for the affected children.

Visual Behavior Impairments as an Aberrant Sensory Processing in the Mouse Model of Fragile X Syndrome

Fragile X Syndrome (FXS), the most common inherited form of human intellectual disability (ID) associated with autistic-like behaviors, is characterized by dys-sensitivity to sensory stimuli, especially vision. In the absence of Fragile Mental Retardation Protein (FMRP), both retinal and cerebral structures of the visual pathway are impaired, suggesting that perception and integration of visual stimuli are altered. However, behavioral consequences of these defects remain unknown. In this study, we used male Fmr1^−/y mice to further define visual disturbances from a behavioral perspective by focusing on three traits characterizing visual modality: perception of depth, contrasts and movements. We performed specific tests (Optomotor Drum, Visual Cliff) to evaluate these visual modalities, their evolution from youth to adulthood, and to assess their involvement in a cognitive task. We show that Fmr1^−/y mice exhibit alteration in their visual skills, displaying impaired perspective perception, a drop in their ability to understand a moving contrasted pattern, and a defect in contrasts discrimination. Interestingly, Fmr1^−/y phenotypes remain stable over time from adolescence to late adulthood. Besides, we report that color and shape are meaningful for the achievement of a cognitive test involving object recognition. Altogether, these results underline the significance of visual behavior alterations in FXS conditions and relevance of assessing visual skills in neuropsychiatric models before performing behavioral tasks, such as cognitive assessments, that involve visual discrimination.