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Biomedicine & Pharmacotherapy =... Nov 2023Humans rely on vision as their most important sense. This is accomplished by photoreceptors (PRs) in the retina that detect light but cannot function without the support... (Review)
Review
Humans rely on vision as their most important sense. This is accomplished by photoreceptors (PRs) in the retina that detect light but cannot function without the support and maintenance of the retinal pigment epithelium (RPE). In subretinal hemorrhage (SRH), blood accumulates between the neurosensory retina and the RPE or between the RPE and the choroid. Blood breakdown products subsequently damage PRs and the RPE and lead to poor vision and blindness. Hence, there is a high need for options to preserve the retina and visual functions. We conducted a systematic review of the literature in accordance with the PRISMA guidelines to identify the cell death mechanisms in RPE and PRs after SRH to deepen our understanding of the pathways involved. After screening 736 publications published until November 8, 2022, we identified 19 records that assessed cell death in PRs and/or RPE in experimental models of SRH. Among the different cell death mechanisms, apoptosis was the most widely investigated mechanism (11 records), followed by ferroptosis (4), whereas necroptosis, pyroptosis, and lysosome-dependent cell death were only assessed in one study each. We discuss different therapeutic options that were assessed in these studies, including the removal of the hematoma/iron chelation, cytoprotection, anti-inflammatory agents, and antioxidants. Further systematic investigations will be necessary to determine the exact cell death mechanisms after SRH with respect to different blood breakdown components, cell types, and time courses. This will form the basis for the development of novel treatment options for SRH.
Topics: Humans; Retinal Pigment Epithelium; Retina; Cell Death; Photoreceptor Cells; Hemorrhage
PubMed: 37742603
DOI: 10.1016/j.biopha.2023.115572 -
Current Stem Cell Research & Therapy 2022The main cause of progressive vision impairment in retinal degenerative diseases is the dysfunction of photoreceptors and the underlying retinal pigment epithelial...
BACKGROUND
The main cause of progressive vision impairment in retinal degenerative diseases is the dysfunction of photoreceptors and the underlying retinal pigment epithelial cells. The inadequate regenerative capacity of the neural retina and lack of established therapeutic options demand the development of clinical-grade protocols to halt the degenerative process in the eye or replace the damaged cells by using stem cell-derived products. Recently, stem cell-based regenerative therapies have been at the forefront of clinical investigations for retinal dystrophies.
OBJECTIVE
This article will review different stem cell-based therapies currently employed for retinal degenerative diseases, recent clinical trials, and major challenges in the translation of these therapies from bench to bedside.
METHODOLOGY
A systematic literature review was conducted to identify potentially relevant articles published in MEDLINE/PubMed, Embase, ClinicalTrials.gov, Drugs@FDA, European Medicines Agency, and World Health Organization International Clinical Trials Registry Platform.
RESULTS
Transplantation of healthy cells to replace damaged cells in the outer retina is a clinically relevant concept because the inner retina that communicates with the visual areas of the brain remains functional even after the photoreceptors are completely lost. Various methods have been established for the differentiation of pluripotent stem cells into different retinal cell types that can be used for therapies. Factors released from transplanted somatic stem cells showed trophic support and photoreceptor rescue during the early stages of the disease. Several preclinical and phase I/II clinical studies using terminally differentiated photoreceptor/retinal pigment epithelial cells derived from pluripotent stem cells have shown proof of concept for visual restoration in Age-related Macular Degeneration (AMD), Stargardt disease, and Retinitis Pigmentosa (RP).
CONCLUSION
Cell replacement therapy has great potential for vision restoration. The results obtained from the initial clinical trials are encouraging and indicate its therapeutic benefits. The current status of the therapies suggests that there is a long way to go before these results can be applied to routine clinical practice. Input from the ongoing multicentre clinical trials will give a more refined idea for the future design of clinical-grade protocols to transplant GMP level HLA matched cells.
Topics: Humans; Pluripotent Stem Cells; Retina; Retinal Degeneration; Retinal Pigment Epithelium; Retinal Pigments; Stem Cell Transplantation
PubMed: 34348629
DOI: 10.2174/1574888X16666210804112104 -
Photodermatology, Photoimmunology &... Sep 2020Skin is the organ most extensively exposed to light of a broad range of wavelengths. Several studies have reported that skin expresses photoreceptive molecules called...
BACKGROUND
Skin is the organ most extensively exposed to light of a broad range of wavelengths. Several studies have reported that skin expresses photoreceptive molecules called opsins. However, the identity and functional role of opsins in the human skin remain elusive. We aim to summarize current scientific evidence on the types of opsins expressed in the skin and their biological functions.
METHODS
A primary literature search was conducted using PubMed to identify articles on dermal opsins found in nonhuman animals and humans.
RESULTS
Twenty-two articles, representing, however, a non-exhaustive selection of the scientific papers published in this specific field, met the inclusion criteria. In nonhuman animals, opsins and opsin-like structures have been detected in the skin of fruit fly, zebrafish, frog, octopus, sea urchin, hogfish, and mouse, and they mediate skin color change, light avoidance, shadow reflex, and circadian photoentrainment. In humans, opsins are present in various skin cell types, including keratinocytes, melanocytes, dermal fibroblasts, and hair follicle cells. They have been shown to mediate wound healing, melanogenesis, hair growth, and skin photoaging.
CONCLUSION
Dermal opsins have been identified across many nonhuman animals and humans. Current evidence suggests that opsins have biological significance beyond light reception. In nonhuman animals, opsins are involved in behaviors that are critical for survival. In humans, opsins are involved in various functions of the skin although the underlying molecular mechanisms remain unclear. Future investigation on elucidating the mechanism of dermal opsins will be crucial to expand the therapeutic benefits of photobiomodulation for various skin disorders.
Topics: Animals; Humans; Opsins; Skin
PubMed: 32431001
DOI: 10.1111/phpp.12578 -
International Journal of Molecular... Apr 2020The retinal pigment epithelium (RPE) and the adjacent light-sensitive photoreceptors form a single functional unit lining the back of the eye. Both cell layers are... (Meta-Analysis)
Meta-Analysis
UNLABELLED
The retinal pigment epithelium (RPE) and the adjacent light-sensitive photoreceptors form a single functional unit lining the back of the eye. Both cell layers are essential for normal vision. RPE degeneration is usually followed by photoreceptor degeneration and vice versa. There are currently almost no effective therapies available for RPE disorders such as Stargardt disease, specific types of retinitis pigmentosa, and age-related macular degeneration. RPE replacement for these disorders, especially in later stages of the disease, may be one of the most promising future therapies. There is, however, no consensus regarding the optimal RPE source, delivery strategy, or the optimal experimental host in which to test RPE replacement therapy. Multiple RPE sources, delivery methods, and recipient animal models have been investigated, with variable results. So far, a systematic evaluation of the (variables influencing) efficacy of experimental RPE replacement parameters is lacking. Here we investigate the effect of RPE transplantation on vision and vision-based behavior in animal models of retinal degenerated diseases. In addition, we aim to explore the effect of RPE source used for transplantation, the method of intervention, and the animal model which is used.
METHODS
In this study, we systematically identified all publications concerning transplantation of RPE in experimental animal models targeting the improvement of vision (e.g., outcome measurements related to the morphology or function of the eye). A variety of characteristics, such as species, gender, and age of the animals but also cell type, number of cells, and other intervention characteristics were extracted from all studies. A risk of bias analysis was performed as well. Subsequently, all references describing one of the following outcomes were analyzed in depth in this systematic review: a-, b-, and c-wave amplitudes, vision-based, thickness analyses based on optical coherence tomography (OCT) data, and transplant survival based on scanning laser ophthalmoscopy (SLO) data. Meta-analyses were performed on the a- and b-wave amplitudes from electroretinography (ERG) data as well as data from vision-based behavioral assays.
RESULTS
original research articles met the inclusion criteria after two screening rounds. Overall, most studies were categorized as unclear regarding the risk of bias, because many experimental details were poorly reported. Twenty-three studies reporting one or more of the outcome measures of interest were eligible for either descriptive (thickness analyses based on OCT data; = 2) or meta-analyses. RPE transplantation significantly increased ERG a-wave (Hedges' g 1.181 (0.471-1.892), = 6) and b-wave (Hedges' g 1.734 (1.295-2.172), = 42) amplitudes and improved vision-based behavior (Hedges' g 1.018 (0.826-1.209), = 96). Subgroup analyses revealed a significantly increased effect of the use of young and adolescent animals compared to adult animals. Moreover, transplanting more cells (in the range of 10 versus in the range of 10) resulted in a significantly increased effect on vision-based behavior as well. The origin of cells mattered as well. A significantly increased effect was found on vision-based behavior when using ARPE-19 and OpRegen RPE.
CONCLUSIONS
This systematic review shows that RPE transplantation in animal models for retinal degeneration significantly increases a- and b- wave amplitudes and improves vision-related behavior. These effects appear to be more pronounced in young animals, when the number of transplanted cells is larger and when ARPE-19 and OpRegen RPE cells are used. We further emphasize that there is an urgent need for improving the reporting and methodological quality of animal experiments, to make such studies more comparable.
Topics: Animals; Cell- and Tissue-Based Therapy; Humans; Models, Animal; Publication Bias; Retinal Degeneration; Retinal Pigment Epithelium; Treatment Outcome
PubMed: 32295315
DOI: 10.3390/ijms21082719 -
Ophthalmology May 2020To summarize the rates of atrophy, risk factors, and atrophy-associated visual outcomes in patients with neovascular age-related macular degeneration (nAMD) who received...
TOPIC
To summarize the rates of atrophy, risk factors, and atrophy-associated visual outcomes in patients with neovascular age-related macular degeneration (nAMD) who received anti-vascular endothelial growth factor (VEGF) treatment for macular neovascularization (MNV).
CLINICAL RELEVANCE
Age-related macular degeneration is a leading cause of vision loss worldwide, and VEGF inhibitors are the primary treatment for nAMD. However, atrophy is observed frequently in eyes treated with anti-VEGF therapy, prompting questions regarding a causative role for these therapies in atrophy development.
METHODS
PubMed was searched for articles published in the past 5 years (January 1, 2014, through January 10, 2019). Studies including atrophy outcome(s) in patients with age-related macular degeneration who received anti-VEGF treatment were included. Review articles, retrospective studies, case reports or studies, preclinical studies, prevalence data reports, and non-English studies were excluded. Randomization was not required.
RESULTS
Overall, 145 studies were identified; 29 publications were included, with cohorts ranging from 8 to 1185 eyes. Imaging methods used to assess atrophy varied across studies. All studies confirmed the occurrence of atrophy, and when available, longitudinal data from the included studies demonstrated an increase in atrophy incidence over time. Key risk factors or phenotypes associated with atrophy were fellow eye atrophy, reticular pseudodrusen, increased injections, and type 3 lesion. In addition, visual acuity loss was noted with foveal atrophy.
DISCUSSION
All studies demonstrated that atrophy occurs in the context of MNV treated with anti-VEGF therapy; however, it is not clear whether anti-VEGF treatment is causative of atrophy versus being associated with atrophy development. The included studies were not designed or powered to assess atrophy as a primary outcome. In addition, it is difficult to determine whether prognostic factors directly affect atrophy. Furthermore, patient populations in clinical trials do not necessarily represent real-world patients. Although phenotypes and risk factors may help to identify those at greater risk of atrophy developing, it is important to recognize that adequately treating exudative MNV remains the best option to optimize vision outcomes in patients with nAMD, particularly given the risk of vision loss with undertreatment observed in the real world.
Topics: Angiogenesis Inhibitors; Atrophy; Choroidal Neovascularization; Humans; Intravitreal Injections; Photoreceptor Cells, Vertebrate; Randomized Controlled Trials as Topic; Retinal Pigment Epithelium; Retrospective Studies; Risk Factors; Vascular Endothelial Growth Factor A; Wet Macular Degeneration
PubMed: 32081493
DOI: 10.1016/j.ophtha.2019.11.010