An in vitro Model of Human Retinal Detachment Reveals Successive Death Pathway Activations

Microglia in Cultured Porcine Retina: Qualitative Immunohistochemical Analyses of Reactive Microglia in the Outer Retina

A late stage of several retinal disorders is retinal detachment, a complication that results in rapid photoreceptor degeneration and synaptic damages. Experimental retinal detachment in vivo is an invasive and complicated method performed on anesthetized animals. As retinal detachment may result in visual impairment and blindness, research is of fundamental importance for understanding degenerative processes. Both morphological and ethical issues make the porcine retina a favorable organotypic model for studies of the degenerative processes that follow retinal detachment. In the cultured retina, photoreceptor degeneration and synaptic injuries develop rapidly and correlate with resident microglial cells' transition into a reactive phenotype. In this immunohistochemical study, we have begun to analyze the transition of subsets of reactive microglia which are known to localize close to the outer plexiform layer (OPL) in degenerating in vivo and in vitro retina. Biomarkers for reactive microglia included P2Ry12, CD63 and CD68 and the general microglial markers were CD11b, Iba1 and isolectin B₄ (IB₄). The reactive microglia markers labeled microglia subpopulations, suggesting that protective or harmful reactive microglia may be present simultaneously in the injured retina. Our findings support the usage of porcine retina cultures for studies of photoreceptor injuries related to retinal detachment.

Applications of a novel reciprocating positive displacement pump in the simulation of pulsatile arterial blood flow

Pulsatile arterial blood flow plays an important role in vascular system mechanobiology, especially in the study of mechanisms of pathology. Limitations in cost, time, sample size, and control across current in-vitro and in-vivo methods limit future exploration of novel treatments. Presented is the verification of a novel reciprocating positive displacement pump aimed at resolving these issues through the simulation of human ocular, human fingertip and skin surface, human cerebral, and rodent spleen organ systems. A range of pulsatile amplitudes, frequencies, and flow rates were simulated using pumps made of 3D printed parts incorporating a tubing system, check valve and proprietary software. Volumetric analysis of 430 total readings across a flow range of 0.025ml/min to 16ml/min determined that the pump had a mean absolute error and mean relative error of 0.041 ml/min and 1.385%, respectively. Linear regression analysis compared to expected flow rate across the full flow range yielded an R2 of 0.9996. Waveform analysis indicated that the pump could recreate accurate beat frequency for flow ranges above 0.06ml/min at 70BPM. The verification of accurate pump output opens avenues for the development of novel long-term in-vitro benchtop models capable of looking at fluid flow scenarios previously unfeasible, including low volume-high shear rate pulsatile flow.

Effect of surgical timing in 23-g pars plana vitrectomy for primary repair of macula-off rhegmatogenous retinal detachment, a retrospective study

Background

Rhegmatogenous retinal detachment (RRD) is a common, potentially blinding ocular pathology that is considered a surgical emergency. Macular involvement has been identified as a major negative prognostic indicator for visual recovery after RRD correction. It is not currently clear whether early intervention improves visual outcomes, and in practice, there are potential disadvantages to performing early surgery for fovea-involving RRD. Such disadvantages include inadequate assessment of coexisting comorbidities, increased rate of complications related to poorly trained staff or tired surgeons, and anesthetic risk.

Methods

A single-center, retrospective, cohort study of patients who underwent repair of macula-involving rhegmatogenous retinal detachment at the University of Virginia was performed. Variables collected included patient demographics, ocular history, clinical characteristics, and post-operative complications. Patients were excluded if they had a history of congenital or acquired pathology with an effect on visual function, bilateral or repeat rhegmatogenous detachment, age less than 18 years, follow up duration less than 6 months, or if they were repaired using scleral buckle, pneumatic retinopexy, 25- or 27-gauge pars plana vitrectomy, or any combination of these techniques. A multivariate regression model was used to compare overall outcomes such as post-operative visual acuity, intra-ocular pressure, retina attachment status, and complications among patients of differing timing of surgical repair. These analyses were adjusted for clinical factors known or considered to be associated with worse prognosis in rhegmatogenous retinal detachment.

Results

A total of 104 patients undergoing 23-gauge vitrectomy for repair of macula involving rhegmatogenous retinal detachments were included in this study with mean follow up period 17.9 ± 14.1 months. Early surgical repair (< 48 h) was pursued in 26 patients, moderately delayed surgical repair (3–7 days), was performed in 29 patients and late surgical repair (> 7 days) in 49 patients. Our analysis showed no difference in post-operative visual acuity between patients with detachments undergoing early versus moderately delayed repair of RRD. However, mean visual acuity differed between patients undergoing early versus late repair at 3, 6, and 12 months. No significant difference was observed in post-operative complications between the three surgical timepoints including cataract formation, development of glaucoma and re-detachment rate. Use of 360 laser was found to be protective against re-detachment overall (OR 6.70 95% CI 1.93–23.2).

Conclusions

These findings indicate that a moderate delay of 3–7 days from symptom onset for repair of macula-involving retinal detachment may be a safe approach as there are no differences in terms of visual acuity or post-operative complications compared to early repair within 48 h. Delaying surgery for > 7 days however is not recommended due to the loss of recovery of visual acuity observed in this study. Use of 360 laser may prevent risk of re-detachment after primary repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02364-4.

Deciphering the Retinal Epigenome during Development, Disease and Reprogramming: Advancements, Challenges and Perspectives

Retinal neurogenesis is driven by concerted actions of transcription factors, some of which are expressed in a continuum and across several cell subtypes throughout development. While seemingly redundant, many factors diversify their regulatory outcome on gene expression, by coordinating variations in chromatin landscapes to drive divergent retinal specification programs. Recent studies have furthered the understanding of the epigenetic contribution to the progression of age-related macular degeneration, a leading cause of blindness in the elderly. The knowledge of the epigenomic mechanisms that control the acquisition and stabilization of retinal cell fates and are evoked upon damage, holds the potential for the treatment of retinal degeneration. Herein, this review presents the state-of-the-art approaches to investigate the retinal epigenome during development, disease, and reprogramming. A pipeline is then reviewed to functionally interrogate the epigenetic and transcriptional networks underlying cell fate specification, relying on a truly unbiased screening of open chromatin states. The related work proposes an inferential model to identify gene regulatory networks, features the first footprinting analysis and the first tentative, systematic query of candidate pioneer factors in the retina ever conducted in any model organism, leading to the identification of previously uncharacterized master regulators of retinal cell identity, such as the nuclear factor I, NFI. This pipeline is virtually applicable to the study of genetic programs and candidate pioneer factors in any developmental context. Finally, challenges and limitations intrinsic to the current next-generation sequencing techniques are discussed, as well as recent advances in super-resolution imaging, enabling spatio-temporal resolution of the genome.

Oral Ursodeoxycholic Acid Crosses the Blood Retinal Barrier in Patients with Retinal Detachment and Protects Against Retinal Degeneration in an Ex Vivo Model

Rhegmatogenous retinal detachment (RD) is a threatening visual condition and a human disease model for retinal degenerations. Despite successful reattachment surgery, vision does not fully recover, due to subretinal fluid accumulation and subsequent photoreceptor cell death, through mechanisms that recapitulate those of retinal degenerative diseases. Hydrophilic bile acids are neuroprotective in animal models, but whether they can be used orally for retinal diseases is unknown. Ursodeoxycholic acid (UDCA) being approved for clinical use (e.g., in cholestasis), we have evaluated the ocular bioavailability of oral UDCA, administered to patients before RD surgery. The level of UDCA in ocular media correlated with the extent of blood retinal barrier disruption, evaluated by the extent of detachment and the albumin concentration in subretinal fluid. UDCA, at levels measured in ocular media, protected photoreceptors from apoptosis and necrosis in rat retinal explants, an ex vivo model of RD. The subretinal fluid from UDCA-treated patients, collected during surgery, significantly protected rat retinal explants from cell death, when compared to subretinal fluid from control patients. Pan-transcriptomic analysis of the retina showed that UDCA upregulated anti-apoptotic, anti-oxidant, and anti-inflammatory genes. Oral UDCA is a potential neuroprotective adjuvant therapy in RD and other retinal degenerative diseases and should be further evaluated in a clinical trial.