Proliferation Of Retinal Progenitor Cells Research Articles

Platelet-activating factor receptor (PAFR) regulates neuronal maturation and synaptic transmission during postnatal retinal development.

Platelet-activating factor (PAF), PAF receptor (PAFR), and PAF- synthesis/degradation systems are involved in essential CNS processes such as neuroblast proliferation, differentiation, migration, and synaptic modulation. The retina is an important central nervous system (CNS) tissue for visual information processing. During retinal development, the balance between Retinal Progenitor Cell (RPC) proliferation and differentiation is crucial for proper cell determination and retinogenesis. Despite its importance in retinal development, the effects of PAFR deletion on RPC dynamics are still unknown. We compared PAFR knockout mice (PAFR-/-) retinal postnatal development proliferation and differentiation aspects with control animals. Electrophysiological responses were analyzed by electroretinography (ERG). In this study, we demonstrate that PAFR-/- mice increased proliferation during postnatal retinogenesis and altered the expression of specific differentiation markers. The retinas of postnatal PAFR-/- animals decreased neuronal differentiation and synaptic transmission markers, leading to differential responses to light stimuli measured by ERG. Our findings suggest that PAFR signaling plays a critical role in regulating postnatal RPC cell differentiation dynamics during retinal development, cell organization, and neuronal circuitry formation.

Hyaluronan-CD44 Interaction Regulates Mouse Retinal Progenitor Cells Migration, Proliferation and Neuronal Differentiation

Cell-based therapies have shown great potential because of their abilities to replace dying retinal neuron cells and preserve vision. The migration, proliferation and differentiation of retinal progenitor cells(RPCs) plays a vital role in the integration of the RPCs into the retina when transplanted into the host. Our study aimed to explore the effects of Hyaluronan(HA)-CD44 interactions on the regulation of RPCs migration, proliferation and differentiation, and investigate the underlying regulatory mechanisms. We found that CD44 was expressed in RPCs, and the HA-CD44 interaction markedly improved RPCs adhesion and migration. The stimulation of microRNA-21(miR-21) expression by the HA-CD44 interaction was protein kinase C (PKC)/Nanog-dependent in RPCs. Treatment of RPCs with PKC- or Nanog-specific ASODN or miR-21 antagomir effectively blocked HA-mediated RPCs adhesion and migration. Moreover, Rho-Kinase(ROK)/ Grb2-associated binders(Gab-1) associated phosphatidylinositol 3-kinase(PI3K)/AKT signalling activation was required for HA-CD44 interaction mediated RPCs proliferation and neuronal differentiation. Our findings demonstrated new roles for the HA-CD44 interaction in regulating the migration, proliferation and neuronal differentiation of RPCs. HA-CD44 signalling could represent a novel approach to controlling RPC fates, and the findings may be instructive for the application of RPCs for future therapeutic applications.Graphical

Loss of flrt2 gene leads to microphthalmia in zebrafish.

As a member of the fibronectin leucine-rich transmembrane (flrt) gene family, fibronectin leucine-rich transmembrane 2 (flrt2) is strongly expressed in a subset of sclerotome cells, and the resultant protein interacts with FGFR1 in the FGF signaling pathway during development. Studies on flrt2 have focused mainly on its roles in the brain, heart and chondrogenesis. However, reports on its expression and function in the zebrafish retina are lacking. Here, we detected the high expression of flrt2 in zebrafish retina using in situ hybridization technique and developed an flrt2-knockout (KO) zebrafish line using CRISPR/Cas9 genome editing. Quantitative real-time PCR was used to measure the expression levels of flrt2, which results in an approximately 60% mRNA reduction. The flrt2-KO zebrafish eyes' altered morphological, cellular, and molecular events were identified using BrdU labeling, TUNEL assay, immunofluorescent staining, fluorescent dye injection and RNA sequencing. Abnormal eye development, known as microphthalmia, was found in flrt2-KO larvae, and the retinal progenitor cells exhibited increased apoptosis, perhaps owing to the combined effects of crx, neurod4, atoh7, and pcdh8 downregulation and Casp3a and Caspbl upregulation. In contrast, the retinal neural development, as well as retinal progenitor cell differentiation and proliferation, were not affected by the flrt2 deletion. Thus, flrt2 appears to play important roles in retinal development and function, which may provide the basis for further investigations into the molecular mechanisms of retinal development and evolution.

The histone H3K36 demethylase Fbxl11 plays pivotal roles in the development of retinal late-born cell types.

Histone methylation plays a vital role in retinal development. However, the role of histone H3K36 methylation in retinal development is not clear. We examined the role of H3K36 methylation by loss-of-function analysis of H3K36me1/2 demethylases, Fbxl10, and Fbxl11. We analyzed the effect of knockout of these genes in the developing and mature retina on retinal development. Knockout of Fbxl10 specifically in the developing retina did not result in gross developmental abnormalities. Although adult rod photoreceptor-specific knockout of Fbxl11 in mature retinas did not result in morphological abnormalities, Fbxl11 knockout in developing retinas increased apoptosis, suppressed the proliferation of retinal progenitor cells, and resulted in microphthalmia. Morphological analysis revealed perturbed differentiation of rod photoreceptor and bipolar cells. RNA-seq of retinas at P7 showed markedly decreased expression of genes characterizing rod photoreceptor and bipolar cells in Fbxl11-knockout retinas. In addition, perturbation of alternative splicing increased intron retention in Fbxl11-knockout retinas. Genome-wide evaluation of the H3K36 methylation status revealed that Fbxl11 knockout altered the distribution of H3K36me2/3 in genes important for rod photoreceptor development. Taken together, we show that Fbxl11 plays pivotal roles in the development of retinal late-born cell types and may contribute to tight control of H3K36 methylation during retinal development.

Chromatin Remodeling Enzyme Snf2h Is Essential for Retinal Cell Proliferation and Photoreceptor Maintenance

Chromatin remodeling complexes are required for many distinct nuclear processes such as transcription, DNA replication, and DNA repair. However, the contribution of these complexes to the development of complex tissues within an organism is poorly characterized. Imitation switch (ISWI) proteins are among the most evolutionarily conserved ATP-dependent chromatin remodeling factors and are represented by yeast Isw1/Isw2, and their vertebrate counterparts Snf2h (Smarca5) and Snf2l (Smarca1). In this study, we focused on the role of the Snf2h gene during the development of the mammalian retina. We show that Snf2h is expressed in both retinal progenitors and post-mitotic retinal cells. Using Snf2h conditional knockout mice (Snf2h cKO), we found that when Snf2h is deleted, the laminar structure of the adult retina is not retained, the overall thickness of the retina is significantly reduced compared with controls, and the outer nuclear layer (ONL) is completely missing. The depletion of Snf2h did not influence the ability of retinal progenitors to generate all the differentiated retinal cell types. Instead, the Snf2h function is critical for the proliferation of retinal progenitor cells. Cells lacking Snf2h have a defective S-phase, leading to the entire cell division process impairments. Although all retinal cell types appear to be specified in the absence of the Snf2h function, cell-cycle defects and concomitantly increased apoptosis in Snf2h cKO result in abnormal retina lamination, complete destruction of the photoreceptor layer, and consequently, a physiologically non-functional retina.

V-ATPase Regulates Retinal Progenitor Cell Proliferation During Eye Regrowth in Xenopus.

Purpose: The induction of retinal progenitor cell (RPC) proliferation is a strategy that holds promise for alleviating retinal degeneration. However, the mechanisms that can stimulate RPC proliferation during repair remain unclear. Xenopus tailbud embryos successfully regrow functional eyes within 5 days after ablation, and this process requires increased RPC proliferation. This model facilitates identification of mechanisms that can drive in vivo reparative RPC proliferation. This study assesses the role of the essential H+ pump, V-ATPase, in promoting stem cell proliferation. Methods: Pharmacological and molecular loss of function studies were performed to determine the requirement for V-ATPase during embryonic eye regrowth. The resultant eye phenotypes were examined using histology and antibody markers. Misexpression of a yeast H+ pump was used to test whether the requirement for V-ATPase in regrowth is dependent on its H+ pump function. Results: V-ATPase inhibition blocked eye regrowth. Regrowth-incompetent eyes resulting from V-ATPase inhibition contained the normal complement of tissues but were much smaller. V-ATPase inhibition caused a significant reduction in reparative RPC proliferation but did not alter differentiation and patterning. Modulation of V-ATPase activity did not affect apoptosis, a process known to be required for eye regrowth. Finally, increasing H+ pump activity was sufficient to induce regrowth. Conclusions: V-ATPase is required for eye regrowth. These results reveal a key role for V-ATPase in activating regenerative RPC proliferation and expansion during successful eye regrowth.

MiR-124-3p regulates the proliferation and differentiation of retinal progenitor cells through SEPT10.

Retinal degenerative diseases such as glaucoma, retinitis pigmentosa, and age-related macular degeneration pose serious threats to human visual health due to lack of effective therapeutic approaches. In recent years, the transplantation of retinal progenitor cells (RPCs) has shown increasing promise in the treatment of these diseases; however, the application of RPC transplantation is limited by both their poor proliferation and their differentiation capabilities. Previous studies have shown that microRNAs (miRNA) act as essential mediators in the fate determination of stem/progenitor cells. In this study, we hypothesized that miR-124-3p plays a regulatory role in the fate of RPC determination by targeting Septin10 (SEPT10) in vitro. We observed that the overexpression of miR124-3p downregulates SEPT10 expression in RPCs, leading to reduced RPC proliferation and increased differentiation, specifically towards both neurons and ganglion cells. Conversely, antisense knockdown of miR-124-3p was shown to boost SEPT10 expression, enhance RPC proliferation, and attenuate differentiation. Moreover, overexpression of SEPT10 rescued miR-124-3p-caused proliferation deficiency while weakening the enhancement of miR-124-3p-induced-RPC differentiation. Results from this study show that miR-124-3p regulates RPC proliferation and differentiation by targeting SEPT10. Furthermore, our findings enable a more comprehensive understanding into the mechanisms of proliferation and differentiation of RPC fate determination. Ultimately, this study may be useful for helping researchers and clinicians to develop more promising and effective approaches to optimize the use of RPCs in treating retinal degeneration diseases.

Maternal Toxoplasma gondii infection affects proliferation, differentiation and cell cycle regulation of retinal neural progenitor cells in mouse embryo.

Toxoplasmosis affects one third of the world population and has the protozoan Toxoplasma gondii as etiological agent. Congenital toxoplasmosis (CT) can cause severe damage to the fetus, including miscarriages, intracranial calcification, hydrocephalus and retinochoroiditis. Severity of CT depends on the gestational period in which infection occurs, and alterations at the cellular level during retinal development have been reported. In this study, we proposed a mouse CT model to investigate the impact of infection on retinal development. Pregnant females of pigmented C57BL/6 strain mice were infected intragastrically with two T. gondii cysts (ME49 strain) at embryonic day 10 (E10), and the offspring were analyzed at E18. Infected embryos had significantly smaller body sizes and weights than the PBS-treated controls, indicating that embryonic development was affected. In the retina, a significant increase in the number of Ki-67-positive cells (marker of proliferating cells) was found in the apical region of the NBL of infected mice compared to the control. Supporting this, cell cycle proteins Cyclin D3, Cdk6 and pChK2 were significantly altered in infected retinas. Interestingly, the immunohistochemical analysis showed a significant increase in the population of β-III-tubulin-positive cells, one of the earliest markers of neuronal differentiation. Our data suggests that CT affects cell cycle progression in retinal progenitor cells, possibly inducing the arrest of these cells at G2/M phase. Such alterations could influence the differentiation, anticipating/increasing neuronal maturation, and therefore leading to abnormal retinal formation. Our model mimics important events observed in ocular CT.

Notch Inhibition Promotes Regeneration and Immunosuppression Supports Cone Survival in a Zebrafish Model of Inherited Retinal Dystrophy.

Photoreceptor degeneration leads to irreversible vision loss in humans with retinal dystrophies such as retinitis pigmentosa. Whereas photoreceptor loss is permanent in mammals, zebrafish possesses the ability to regenerate retinal neurons and restore visual function. Following acute damage, Müller glia (MG) re-enter the cell cycle and produce multipotent progenitors whose progeny differentiate into mature neurons. Both MG reprogramming and proliferation of retinal progenitor cells require reactive microglia and associated inflammatory signaling. Paradoxically, in zebrafish models of retinal degeneration, photoreceptor death does not induce the MG to reprogram and regenerate lost cells. Here, we used male and female zebrafish cep290 mutants to demonstrate that progressive cone degeneration generates an immune response but does not stimulate MG proliferation. Acute light damage triggered photoreceptor regeneration in cep290 mutants but cones were only restored to prelesion densities. Using irf8 mutant zebrafish, we found that the chronic absence of microglia reduced inflammation and rescued cone degeneration in cep290 mutants. Finally, single-cell RNA-sequencing revealed sustained expression of notch3 in MG of cep290 mutants and inhibition of Notch signaling induced MG to re-enter the cell cycle. Our findings provide new insights on the requirements for MG to proliferate and the potential for immunosuppression to prolong photoreceptor survival.SIGNIFICANCE STATEMENT Inherited retinal degenerations (IRDs) are genetic diseases that lead to the progressive loss of photoreceptors and the permanent loss of vision. Zebrafish can regenerate photoreceptors after acute injury by reprogramming Müller glia (MG) into stem-like cells that produce retinal progenitors, but this regenerative process fails to occur in zebrafish models of IRDs. Here, we show that Notch pathway inhibition can promote photoreceptor regeneration in models of progressive degeneration and that immunosuppression can prevent photoreceptor loss. These results offer insight into the pathways that promote MG-dependent regeneration and the role of inflammation in photoreceptor degeneration.

[Effects of leptin on proliferation and differentiation of hypoxic rat retinal progenitor cells in vitro].

To investigate the the effects of leptin on the proliferation, differentiation and PTEN expression of rat retinal progenitor cells (RPCs) cultured under hypoxic condition. SD rat RPCs were cultured in normoxic conditions or exposed to hypoxia in the presence of 0, 0.3, 1.0, 3.0, 10, and 30 nmol/L leptin for 12, 48 and 72 h, and the cell viability was assessed using cell counting kit 8 (CCK 8) assay. The RPCs in primary culture were divided into control group, hypoxia group, and hypoxia+leptin group, and after 48 h of culture, the cell medium was replaced with differentiation medium and the cells were further cultured for 6 days. Immunofluorescence staining was employed to detect the cells positive for β-tubulin III and GFAP, and Western blotting was used to examine the expression of PTEN at 48 h of cell culture. The first generation of RPCs showed suspended growth in the medium with abundant and bright cellular plasma and formed mulberry like cell spheres after 2 days of culture. Treatment with low-dose leptin (below 3.0 nmol/L) for 48 h obviously improved the viability of RPCs cultured in hypoxia, while at high concentrations (above 10 nmol/L), leptin significantly suppressed the cell viability (P < 0.05). The cells treated with 3.0 nmol/L leptin for 48 h showed the highest viability (P < 0.05). After treatment with 3.0 nmol/L leptin for 48 h, the cells with hypoxic exposure showed similar GFAP and β-tubulin Ⅲ positivity with the control cells (P>0.05), but exhibited an obvious down-regulation of PTEN protein expression compared with the control cells (P < 0.05). In rat RPCs with hypoxic exposure, treatment with low dose leptin can promote the cell proliferation and suppress cellular PTEN protein expression without causing significant effects on cell differentiation.

MiR-381-3p Cooperated With Hes1 to Regulate the Proliferation and Differentiation of Retinal Progenitor Cells.

Retinal progenitor cells (RPCs) transplantation has become a promising therapy for retinal degeneration, which is a major kind of ocular diseases causing blindness. Since RPCs have limited proliferation and differentiation abilities toward retinal neurons, it is urgent to resolve these problems. MicroRNAs have been reported to have vital effects on stem cell fate. In our study, the data showed that overexpression of miR-381-3p repressed Hes1 expression, which promoted RPCs differentiation, especially toward neuronal cells, and inhibited RPCs proliferation. Knockdown of endogenous miR-381-3p increased Hes1 expression to inhibit RPCs differentiation and promote proliferation. In addition, a luciferase assay demonstrated that miR-381-3p directly targeted the Hes1 3’ untranslated region (UTR). Taken together, our study demonstrated that miR-381-3p regulated RPCs proliferation and differentiation by targeting Hes1, which provides an experimental basis of RPCs transplantation therapy for retinal degeneration.

Identification of a modular super-enhancer in murine retinal development

Super-enhancers are expansive regions of genomic DNA comprised of multiple putative enhancers that contribute to the dynamic gene expression patterns during development. This is particularly important in neurogenesis because many essential transcription factors have complex developmental stage– and cell–type specific expression patterns across the central nervous system. In the developing retina, Vsx2 is expressed in retinal progenitor cells and is maintained in differentiated bipolar neurons and Müller glia. A single super-enhancer controls this complex and dynamic pattern of expression. Here we show that deletion of one region disrupts retinal progenitor cell proliferation but does not affect cell fate specification. The deletion of another region has no effect on retinal progenitor cell proliferation but instead leads to a complete loss of bipolar neurons. This prototypical super-enhancer may serve as a model for dissecting the complex gene expression patterns for neurogenic transcription factors during development. Moreover, it provides a unique opportunity to alter expression of individual transcription factors in particular cell types at specific stages of development. This provides a deeper understanding of function that cannot be achieved with traditional knockout mouse approaches.

A chiral microenvironment promotes retinal progenitor cell proliferation by activating the Akt and ERK pathways.

Retinal progenitor cell (RPC) transplantation has been proposed as a potential strategy for the treatment of retinal degeneration, which is a leading cause of vision loss. However, a major obstacle is the poor proliferation of RPCs. Accumulating evidence suggests that the chiral features of the extracellular microenvironment are closely related to cell proliferation. Inspired by this, L/D-phenylalanine-derived molecules (LP and DP) are employed to construct a biomimetic chiral microenvironment for enhancing RPC proliferation. LP and DP self-assemble into left-handed and right-handed helical fibrous networks, respectively. It is found that DP nanofibrous films show an excellent ability in promoting RPC proliferation via the activation of the Akt and extracellular signal-regulated kinase (ERK) pathways. In addition, both LP and DP nanofibrous films have the advantage of attenuating inflammation, and LP films can maintain the stem potential of RPCs. Thus, the promotion of RPC proliferation using a bioinspired chiral fibrous microenvironment is a promising strategy for RPC-based therapies for retinal degeneration.

MTORC1-induced retinal progenitor cell overproliferation leads to accelerated mitotic aging and degeneration of descendent Müller glia.

Retinal progenitor cells (RPCs) divide in limited numbers to generate the cells comprising vertebrate retina. The molecular mechanism that leads RPC to the division limit, however, remains elusive. Here, we find that the hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1) in an RPC subset by deletion of tuberous sclerosis complex 1 (Tsc1) makes the RPCs arrive at the division limit precociously and produce Müller glia (MG) that degenerate from senescence-associated cell death. We further show the hyperproliferation of Tsc1-deficient RPCs and the degeneration of MG in the mouse retina disappear by concomitant deletion of hypoxia-induced factor 1-alpha (Hif1a), which induces glycolytic gene expression to support mTORC1-induced RPC proliferation. Collectively, our results suggest that, by having mTORC1 constitutively active, an RPC divides and exhausts mitotic capacity faster than neighboring RPCs, and thus produces retinal cells that degenerate with aging-related changes.

TLX, an Orphan Nuclear Receptor With Emerging Roles in Physiology and Disease.

TLX (NR2E1), an orphan member of the nuclear receptor superfamily, is a transcription factor that has been described to be generally repressive in nature. It has been implicated in several aspects of physiology and disease. TLX is best known for its ability to regulate the proliferation of neural stem cells and retinal progenitor cells. Dysregulation, overexpression, or loss of TLX expression has been characterized in numerous studies focused on a diverse range of pathological conditions, including abnormal brain development, psychiatric disorders, retinopathies, metabolic disease, and malignant neoplasm. Despite the lack of an identified endogenous ligand, several studies have described putative synthetic and natural TLX ligands, suggesting that this receptor may serve as a therapeutic target. Therefore, this article aims to briefly review what is known about TLX structure and function in normal physiology, and provide an overview of TLX in regard to pathological conditions. Particular emphasis is placed on TLX and cancer, and the potential utility of this receptor as a therapeutic target.

Setd1a Plays Pivotal Roles for the Survival and Proliferation of Retinal Progenitors via Histone Modifications of Uhrf1.

PurposeThe trimethylation of histone H3 at lysine 4 (H3K4me3) facilitates transcriptional gene activation, and Setd1a is the methyltransferase specific to H3K4. H3K4me3 has been reported to regulate rod photoreceptor differentiation; however, the roles H3K4me3 plays in retinal progenitor cell (RPC) proliferation and differentiation during early retinal development remain unclear.MethodsUsing an in vitro retinal explant culture system, we suppressed the expression of Setd1a by introducing shSetd1a. We examined the expression level and H3K4me3 level of genes by RNA Sequencing and ChIP assay, respectively.ResultsWe found that Setd1a depletion resulted in increased apoptosis and proliferation failure in late RPCs. Expression of wild-type SETD1A, but not SETD1A that lacked the catalytic SET domain, reversed the shSetd1a-induced phenotype. RNA Sequencing revealed that proliferation-related genes were downregulated upon shSetd1a expression. Based on publicly available H3K4me3-ChIP sequencing data of retinal development, we identified Uhrf1 as a candidate target gene of Setd1a. The expression of shSetd1a led to a decrease in Uhrf1 transcript levels and reduced H3K4me3 levels at the Uhrf1 locus. Increased apoptosis and the suppression of proliferation in late RPCs were observed in retinal explants expressing shUhrf1, similar to the outcomes observed in shSetd1a-expressing retinas. The overexpression of UHRF1 did not rescue shSetd1a-induced apoptosis, but reversed the suppression of proliferation.ConclusionsThese results indicate that Setd1a contributes to the survival and proliferation of retinal cells by regulating histone methylation, Setd1a regulates Uhrf1 expression, and these two molecules cooperate to regulate RPC survival and proliferation.

PLATELET-ACTIVATING FACTOR (PAF) RECEPTOR ANTAGONIST TREATMENT INCREASES PROLIFERATION AND PROGENITOR MARKERS EXPRESSION IN RETINAL STEM CELLS

<h3>Background</h3> Retinal degenerative diseases are a worldwide public health problem and the main cause of visual loss in humans. Considering stem cell-based therapy as a possible medical approach, quiescent retinal stem cells were identified in the Ciliary Epithelium (CE) of adult mammals; however, regulatory mechanisms inhibit CE stemness, limiting its regenerative potential. It is known that PAF receptor (PAFR) activation suppresses retinal progenitor cell proliferation, suggesting that PAF/PAFR signaling regulates eye stem cells and development. Here we investigated the expression of PAF regulatory enzymes in CE-derived stem cells and the effect of PAFR modulation on proliferation, progenitor, and epithelial markers expression. <h3>Methods</h3> Pigmented epithelium was dissected from mice CE tissue, cultured in DMEN-F12 with 10% FBS for 30 days. Later we add growth factors (EGF/FGF2) to form neurospheres. We analyzed CE and neurospheres transcriptional expression of Pafr, Lpcat1, Pafah1 by real-time PCR. PAFR was modulated during neurosphere forming assay with cPAF (agonist) or PCA4248 (antagonist), and epithelial markers (E-cadherin, N-cadherin), proliferation (Ki67), and progenitor (Pax6 and Nestin) transcripts were analyzed by real-time PCR. An immunohistochemistry assay was performed to investigate proliferation and progenitor markers expression (Ki67 and Sox2). <h3>Results</h3> CE cells downregulated PAF-related enzymes and PAFR expression during neurospheres reprogramming. PAFR agonist inhibited neurosphere formation and controlled epithelial transcriptional expression and morphological phenotype. Oppositely, PAFR antagonist upregulated progenitor transcripts, enhancing CE stemness through increased Ki67, Sox2, Nestin, and Pax6 expression. <h3>Conclusion</h3> Together, our data strongly suggest that PAFR controls CE stemness and can be a promising target for retinal regenerative approaches. <h3>Financial support</h3> FAPESP grant number 2015/24001-1 and 2019/08544-6.

Glucocorticoid agonists enhance retinal stem cell self-renewal and proliferation

BackgroundAdult mammalian retinal stem cells (RSCs) readily proliferate, self-renew, and generate progeny that differentiate into all retinal cell types in vitro. RSC-derived progeny can be induced to differentiate into photoreceptors, making them a potential source for retinal cell transplant therapies. Despite their proliferative propensity in vitro, RSCs in the adult mammalian eye do not proliferate and do not have a regenerative response to injury. Thus, identifying and modulating the mechanisms that regulate RSC proliferation may enhance the capacity to produce RSC-derived progeny in vitro and enable RSC activation in vivo.MethodsHere, we used medium-throughput screening to identify small molecules that can expand the number of RSCs and their progeny in culture. In vitro differentiation assays were used to assess the effects of synthetic glucocorticoid agonist dexamethasone on RSC-derived progenitor cell fate. Intravitreal injections of dexamethasone into adult mouse eyes were used to investigate the effects on endogenous RSCs.ResultsWe discovered that high-affinity synthetic glucocorticoid agonists increase RSC self-renewal and increase retinal progenitor proliferation up to 6-fold without influencing their differentiation in vitro. Intravitreal injection of synthetic glucocorticoid agonist dexamethasone induced in vivo proliferation in the ciliary epithelium—the niche in which adult RSCs reside.ConclusionsTogether, our results identify glucocorticoids as novel regulators of retinal stem and progenitor cell proliferation in culture and provide evidence that GCs may activate endogenous RSCs.

Electrospun PGS/PCL, PLLA/PCL, PLGA/PCL and pure PCL scaffolds for retinal progenitor cell cultivation

Recent advances in cell transplantation technologies have shown that polymeric fibrous tissue-engineered scaffolds provide a suitable physical environment, including the structural support, for cell delivery and effectively mimic the transplanted cells’ extracellular matrix. Our study investigates the structure, composition and properties of three most commonly used polyester-based biopolymer materials blended with poly(ε-caprolactone) (PCL) at 2:1 (wt.%) ratio, namely, poly(glycerol sebacate) (PGS)/PCL, polylactic-co-glycolic acid (PLGA)/PCL, poly-l-lactide (PLLA)/PCL and pure PCL as carrier vehicles for retinal progenitor cell (RPC) attachment and RPC proliferation. The physicochemical properties of PGS/PCL, PLLA/PCL, PLGA/PCL and pure PCL fibrous scaffolds, fabricated under the identical electrospinning conditions, were analysed employing scanning electron microscopy, contact angle analysis, Raman spectroscopy, electrical and ionic conductivity measurements, and supplemented by an in-vitro RPC adhesion and proliferation studies. Our findings have shown that PGS/PCL scaffolds promote RPC attachment and RPC proliferation more favourably compared to other polymeric blends and pure PCL, owing to a combination of advantageous surface and bulk properties, overall demonstrating a potential for PGS/PCL blend to become a suitable vehicle for RPC delivery in a possible future clinical therapy for the treatment of retinal degenerative disorders.

Activation of Type 4 Metabotropic Glutamate Receptor Regulates Proliferation and Neuronal Differentiation in a Cultured Rat Retinal Progenitor Cell Through the Suppression of the cAMP/PTEN/AKT Pathway.

Retinal progenitor cells (RPCs) remain in the eye throughout life and can be characterized by their ability for self-renewal as well as their specialization into different cell types. A recent study has suggested that metabotropic glutamate receptors (mGluRs) participate in the processes of multiple types of stem cells. Therefore, clarifying the functions of different subtypes of mGluRs in RPCs may provide a novel treatment strategy for regulating the proliferation and differentiation of endogenous RPCs after retinal degeneration. In this study, we observed that mGluR4 was functionally expressed in RPCs, with an effect on cell viability and intracellular cAMP concentration. The activation of mGluR4 by VU0155041 (VU, mGluR4 positive allosteric selective modulator) reduced the number of BrdU+/Pax6+ double-positive cells and Cyclin D1 expression levels while increasing the number of neuron-specific class III beta-tubulin (Tuj1)- and Doublecortin (DCX)-positive cells. The knockdown of mGluR4 by target-specific siRNA abolished the effects of VU on RPC proliferation and neuronal differentiation. Further investigation demonstrated that mGluR4 activation inhibited AKT phosphorylation and up-regulated PTEN protein expression. Moreover, the VU0155041-induced inhibition of proliferation and enhancement of neuronal differentiation in RPCs were significantly hampered by Forskolin (adenylyl cyclase activator) and VO-OHpic trihydrate (PTEN inhibitor). In contrast, the effect of LY294002 (a highly selective Akt inhibitor) on proliferation and differentiation was similar to that of VU. These results indicate that mGluR4 activation can suppress proliferation and promote the neural differentiation of cultured rat RPCs through the cAMP/PTEN/AKT pathway. Our research lays the foundation for further pharmacological work exploring a novel potential therapy for several retinal diseases.