An in vitro comparison of two different subpopulations of retinal progenitor cells for self-renewal and multipotentiality

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.

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.

miR-762 regulates the proliferation and differentiation of retinal progenitor cells by targeting NPDC1

Retinal degenerations, which lead to irreversible decline in visual function, are still no effective recovery treatments. Currently, retinal progenitor cell (RPC) transplantation therapy is expected to provide a new approach to treat these diseases; however, the limited proliferation capacity and differentiation potential toward specific retinal neurons of RPCs hinder their potential clinical applications. microRNAs have been reported to serve as important regulators in the cell fate determination of stem/progenitor cells. In this study, our data demonstrated that miR-762 inhibited NPDC1 expression to positively regulate RPC proliferation and suppress RPC neuronal differentiation. Furthermore, the knockdown of miR-762 upregulated NPDC1 expression in RPCs, leading to the inhibition of RPC proliferation and the increase in neuronal differentiation. Moreover, NPDC1 could rescue anti-miR-762-induced RPC proliferation deficiency and the inhibitory effect of miR-762 on RPC differentiation. In conclusion, our study demonstrated that miR-762 plays a crucial role in regulating RPC proliferation and differentiation by directly targeting NPDC1, which is firstly reported that microRNAs positively regulate RPC proliferation and negatively regulate RPC differentiation, which provides a comprehensive understanding of the molecular mechanisms that dominate RPC proliferation and differentiation in vitro.

Enhanced proliferation and differentiation of retinal progenitor cells through a self-healing injectable hydrogel

Fabrication of self-healing injectable CS-Odex hydrogels via a dynamic Schiff-base linkage for RPC delivery.

Mussel-inspired injectable hydrogel and its counterpart for actuating proliferation and neuronal differentiation of retinal progenitor cells

Biomaterials-mediated retinal progenitor cell (RPC)-based transplantation therapy has shown substantial potential for retinal degeneration (RD), but it is limited by the poor RPC survival, proliferation and differentiation. Herein, the gelatin-hyaluronic acid (Gel-HA)-based hydrogels formed via moderate Michael-type addition reaction with or without the introduction of mussel-inspired polydopamine (PDA), i.e. Gel-HA-PDA and its counterpart Gel-HA hydrogels are developed, and their effects on the biological behaviour of RPCs, including adhesion, survival, proliferation, differentiation, delivery and migration are investigated. The hybrid hydrogels can adopt the intricate structure of the retina with suitable mechanical strength, degradation rate and biological activity to support cellular adhesion, survival and delivery. Meanwhile, Gel-HA hydrogel can remarkably promote RPC proliferation with much larger cell clusters, while Gel-HA-PDA hydrogel significantly enhances RPC adhesion and migration, and directs RPCs to preferentially differentiate toward retinal neurons such as photoreceptors (the most crucial cell-type for RD treatment), which is mainly induced by the activation of integrin α5β1-phosphatidylinositol-3-kinase (PI3K) pathway. This study demonstrates that Gel-HA hydrogel possesses great potential for RPC proliferation, while mussel-inspired PDA-modified Gel-HA hydrogel with superior biocompatibility can significantly promote RPC neuronal differentiation, providing new insights for developing biomedical materials applied for RPC-based transplantation therapy.

REST, regulated by RA through miR-29a and the proteasome pathway, plays a crucial role in RPC proliferation and differentiation

One of the primary obstacles in the application of retinal progenitor cells (RPCs) to the treatment of retinal degenerative diseases, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP), is their limited ability to proliferate and differentiate into specific retinal neurons. In this study, we revealed that repressor element-1-silencing transcription factor (REST), whose expression could be transcriptionally and post-transcriptionally mediated by retinoic acid (RA, one isomeride of a vitamin A derivative used as a differentiation-inducing agent in many disease treatments), plays a pivotal role in the regulation of proliferation and differentiation of RPCs. Our results show that direct knockdown of endogenous REST reduced RPC proliferation but accelerated RPC differentiation toward retinal neurons, which phenocopied the observed effects of RA on RPCs. Further studies disclosed that the expression level of REST could be downregulated by RA not only through upregulating microRNA (miR)-29a, which directly interacted with the 3′-untranslated region (3′-UTR) of the REST mRNA, but also through promoting REST proteasomal degradation. These results show us a novel functional protein, REST, which regulates RPC proliferation and differentiation, can be mediated by RA. Understanding the mechanisms of REST and RA in RPC fate determination enlightens a promising future for the application of REST and RA in the treatment of retinal degeneration diseases.

miR-29a regulates the proliferation and differentiation of retinal progenitors by targeting Rbm8a

During development, tight regulation of the expansion of retinal progenitor cells (RPCs) and their differentiation into neuronal and glial cells is important for retinal formation and function. Our study demonstrated that microRNA (miR)-29a modulated the proliferation and differentiation of RPCs by suppressing RBM8A (one of the factors in the exon junction complex). Particularly, overexpression of miR-29a reduced RPC proliferation but accelerated RPC differentiation. By contrast, reduction of endogenous miR-29a elicited the opposite effects. Overexpression of miR-29a repressed the translation of Rbm8a, thus negatively regulating RPC proliferation and promoting the neuronal and glial differentiation of RPCs, and knockdown of endogenous Rbm8a phenocopied the observed effects of miR-29a overexpression. Furthermore, a luciferase reporter assay showed that miR-29a directly interacted with the Rbm8a mRNA 3′UTR, which indicated that Rbm8a is the direct target of miR-29a. To further verify the result, co-overexpression of the Rbm8a 3′ UTR-wt (plasmids into which the Rbm8a 3′ UTR sequence had been introduced) and miR-29a in RPCs rescued the phenotype associated with miR-29a overexpression, reversing the promotion of differentiation and inhibition of proliferation. These results show a novel mechanism by which miR-29a regulates the proliferation and differentiation of RPCs through Rbm8a.

Effects of corneal stromal cell- and bone marrow-derived endothelial progenitor cell-conditioned media on the proliferation of corneal endothelial cells

AIM

To explore the effects of conditioned media on the proliferation of corneal endothelial cells (CECs) and to compare the efficiency of different conditioned media (CM).

METHODS

Rat CECs, corneal stromal cells (CSCs), bone marrow-derived endothelial progenitor cells (BEPCs), and bone marrow-derived mesenchymal stem cells (BMSCs) were isolated and cultured in vitro. CM was collected from CSCs, BEPCs, and BMSCs. CECs were cultivated in different culture media. Cell morphology was recorded, and gene and protein expression were analyzed.

RESULTS

After grown in CM for 5d, CECs in each experimental group remained polygonal, in a cobblestone-like monolayer arrangement. Immunocytofluorescence revealed positive expression of Na(+)/K(+)-ATP, aquaporin 1 (AQP1), and zonula occludens 1 (ZO-1). Based on quantitative polymerase chain reaction (qPCR) analysis, Na(+)/K(+)-ATP expression in CSC-CM was notably upregulated by 1.3-fold (±0.036) (P<0.05, n=3). The expression levels of ZO-1, neuron specific enolase (NSE), Vimentin, paired homebox 6 (PAX6), and procollagen type VIII (COL8A1) were notably upregulated in each experimental group. Each CM had a positive effect on CEC proliferation, and CSC-CM had the strongest effect on proliferation.

CONCLUSION

CSC-CM, BEPC-CM, and BMSC-CM not only stimulated the proliferation of CECs, but also maintained the characteristic differentiated phenotypes necessary for endothelial functions. CSC-CM had the most notable effect on CEC proliferation.

Electrospun SF/PLCL nanofibrous membrane: a potential scaffold for retinal progenitor cell proliferation and differentiation

Biocompatible polymer scaffolds are promising as potential carriers for the delivery of retinal progenitor cells (RPCs) in cell replacement therapy for the repair of damaged or diseased retinas. The primary goal of the present study was to investigate the effects of blended electrospun nanofibrous membranes of silk fibroin (SF) and poly(L-lactic acid-co-ε-caprolactone) (PLCL), a novel scaffold, on the biological behaviour of RPCs in vitro. To assess the cell-scaffold interaction, RPCs were cultured on SF/PLCL scaffolds for indicated durations. Our data revealed that all the SF/PLCL scaffolds were thoroughly cytocompatible, and the SF:PLCL (1:1) scaffolds yielded the best RPC growth. The in vitro proliferation assays showed that RPCs proliferated more quickly on the SF:PLCL (1:1) than on the other scaffolds and the control. Quantitative polymerase chain reaction (qPCR) and immunocytochemistry analyses demonstrated that RPCs grown on the SF:PLCL (1:1) scaffolds preferentially differentiated toward retinal neurons, including, most interestingly, photoreceptors. In summary, we demonstrated that the SF:PLCL (1:1) scaffolds can not only markedly promote RPC proliferation with cytocompatibility for RPC growth but also robustly enhance RPCs’ differentiation toward specific retinal neurons of interest in vitro, suggesting that SF:PLCL (1:1) scaffolds may have potential applications in retinal cell replacement therapy in the future.

c-Kit+ cells isolated from human fetal retinas represent a new population of retinal progenitor cells

Definitive surface markers for retinal progenitor cells (RPCs) are still lacking. Therefore, we sorted c-Kit+ and stage-specific embryonic antigen-4− (SSEA4−) retinal cells for further biological characterization. RPCs were isolated from human fetal retinas (gestational age of 12–14 weeks). c-Kit+/SSEA4− RPCs were sorted by fluorescence-activated cell sorting, and their proliferation and differentiation capabilities were evaluated by using immunocytochemistry and flow cytometry. The effectiveness and safety were assessed following injection of c-Kit+/SSEA4− cells into the subretina of Royal College of Surgeons (RCS) rats. c-Kit+ cells were found in the inner part of the fetal retina. Sorted c-Kit+/SSEA4− cells expressed retinal stem cell markers. Our results clearly demonstrate the proliferative potential of these cells. Moreover, c-Kit+/SSEA4− cells differentiated into retinal cells that expressed markers of photoreceptor cells, ganglion cells and glial cells. These cells survived for at least 3 months after transplantation into the host subretinal space. Teratomas were not observed in the c-Kit+/SSEA4−-cell group. Thus, c-Kit can be used as a surface marker for RPCs, and c-Kit+/SSEA4− RPCs exhibit the ability to self-renew and differentiate into retinal cells.

Effects of let-7b and TLX on the proliferation and differentiation of retinal progenitor cells in vitro

MicroRNAs manifest significant functions in brain neural stem cell (NSC) self-renewal and differentiation through the post-transcriptional regulation of neurogenesis genes. Let-7b is expressed in the mammalian brain and regulates NSC proliferation and differentiation by targeting the nuclear receptor TLX, which is an essential regulator of NSC self-renewal. Whether let-7b and TLX act as important regulators in retinal progenitor cell (RPC) proliferation and differentiation remains unknown. Here, our data show that let-7b and TLX play important roles in controlling RPC fate determination in vitro. Let-7b suppresses TLX expression to negatively regulate RPC proliferation and accelerate the neuronal and glial differentiation of RPCs. The overexpression of let-7b downregulates TLX levels in RPCs, leading to reduced RPC proliferation and increased neuronal and glial differentiation, whereas antisense knockdown of let-7b produces robust TLX expression,enhanced RPC proliferation and decreased differentiation. Moreover, the inhibition of endogenous TLX by small interfering RNA suppresses RPC proliferation and promotes RPC differentiation. Furthermore, overexpression of TLX rescues let-7b-induced proliferation deficiency and weakens the RPC differentiation enhancement caused by let-7b alone. These results suggest that let-7b, by forming a negative feedback loop with TLX, provides a novel model to regulate the proliferation and differentiation of retinal progenitors in vitro.

Reciprocal actions of microRNA-9 and TLX in the proliferation and differentiation of retinal progenitor cells

Recent research has demonstrated critical roles of a number of microRNAs (miRNAs) in stem cell proliferation and differentiation. miRNA-9 (miR-9) is a brain-enriched miRNA. Whether miR-9 has a role in retinal progenitor cell (RPC) proliferation and differentiation remains unknown. In this study, we show that miR-9 plays an important role in RPC fate determination. The expression of miR-9 was inversely correlated with that of the nuclear receptor TLX, which is an essential regulator of neural stem cell self-renewal. Overexpression of miR-9 downregulated the TLX levels in RPCs, leading to reduced RPC proliferation and increased neuronal and glial differentiation, and the effect of miR-9 overexpression on RPC proliferation and differentiation was inhibited by the TLX overexpression; knockdown of miR-9 resulted in increased TLX expression as well as enhanced proliferation of RPCs. Furthermore, inhibition of endogenous TLX by small interfering RNA suppressed RPC proliferation and promoted RPCs to differentiate into retinal neuronal and glial cells. These results suggest that miR-9 and TLX form a feedback regulatory loop to coordinate the proliferation and differentiation of retinal progenitors.

Bone marrow mesenchymal stem cells stimulate proliferation and neuronal differentiation of retinal progenitor cells

During retina development, retinal progenitor cell (RPC) proliferation and differentiation are regulated by complex inter- and intracellular interactions. Bone marrow mesenchymal stem cells (BMSCs) are reported to express a variety of cytokines and neurotrophic factors, which have powerful trophic and protective functions for neural tissue-derived cells. Here, we show that the expanded RPC cultures treated with BMSC-derived conditioned medium (CM) which was substantially enriched for bFGF and CNTF, expressed clearly increased levels of nuclear receptor TLX, an essential regulator of neural stem cell (NSC) self-renewal, as well as betacellulin (BTC), an EGF-like protein described as supporting NSC expansion. The BMSC CM- or bFGF-treated RPCs also displayed an obviously enhanced proliferation capability, while BMSC CM-derived bFGF knocked down by anti-bFGF, the effect of BMSC CM on enhancing RPC proliferation was partly reversed. Under differentiation conditions, treatment with BMSC CM or CNTF markedly favoured RPC differentiation towards retinal neurons, including Brn3a-positive retinal ganglion cells (RGCs) and rhodopsin-positive photoreceptors, and clearly diminished retinal glial cell differentiation. These findings demonstrate that BMSCs supported RPC proliferation and neuronal differentiation which may be partly mediated by BMSC CM-derived bFGF and CNTF, reveal potential limitations of RPC culture systems, and suggest a means for optimizing RPC cell fate determination in vitro.

The role of miR-31-modified adipose tissue-derived stem cells in repairing rat critical-sized calvarial defects

With the increasing application of microRNAs (miRNAs) in the treatment and monitoring of different diseases, miRNAs have become an important tool in biological and medical research. Recent studies have proven that miRNAs are involved in the osteogenic differentiation of stem cells. However, few studies have reported the use of miRNA-modified adult stem cells to repair critical-sized defects (CSDs) using tissue engineering technology. It is known that miR-31 is a pleiotropically acting miRNA that inhibits cancer metastasis and targets special AT-rich sequence-binding protein 2 (Satb2) in fibroblasts. However, it is not clear whether the function of miR-31 is to enhance adipose tissue-derived stem cell (ASC) osteogenesis, along with its association with Satb2, during osteogenic differentiation and bone regeneration. In this study, we systematically evaluated the function of miR-31 in enhancing ASC osteogenesis and the therapeutic potential of miR-31-modified ASCs in a rat CSD model with β-tricalcium phosphate (β-TCP) scaffolds. ASCs were treated with lentivirus (Lenti)-miR-31, Lenti-as-miR-31 (antisense) or Lenti-NC (negative control). These genetically modified ASCs were then combined with β-TCP scaffolds to repair CSDs in rats. The results showed that in cultured ASCs in vitro, Lenti-as-miR-31 significantly enhanced osteogenic mRNA and protein expression when compared with the Lenti-NC group. Moreover, we firstly found that a Runt-related transcription factor 2 (Runx2), Satb2 and miR-31 regulatory loop triggered by bone morphogenetic protein-2 (BMP-2) plays an important role in ASCs' osteogenic differentiation and bone regeneration. More importantly, we found that miR-31-knockdown ASCs dramatically improved the repair of CSDs, including increased bone volume, increased bone mineral density (BMD) and decreased scaffold residue in vivo. These data confirm the essential role of miR-31-modified ASCs in osteogenesis in vitro and in vivo.

Insulin-like growth factor 1 promotes the proliferation and adipogenesis of orbital adipose-derived stromal cells in thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is characterised by increased volume of the orbital contents involving adipose tissue, but the factors responsible for stimulation of orbital adipogenesis remain uncertain. Previous studies have shown that insulin-like growth factor 1 (IGF-1) is increased in the orbital fatty connective tissues of patients with TAO. The present study was conducted to investigate the effects of IGF-1 on orbital adipose-derived stromal cells (OADSCs) derived from TAO patients and to identify the signalling mechanisms involved. Our results showed that IGF-1 significantly promoted the cell proliferation and lipid accumulation of TAO OADSCs. The mRNA expression of adipogenic markers (adiponectin, leptin, adipocyte fatty acid binding protein [AP2] and fatty acid synthase [FAS]) was increased in TAO cultures treated with IGF-1. Further research demonstrated that the protein levels of peroxisome proliferator-activated receptor-γ (PPARγ) were up-regulated when OADSCs were treated with IGF-1. We also found that the inhibition of either IGF-1 receptor (IGF-1R) or phosphoinositide 3-kinase (PI3K) activity decreased the levels of IGF-1-stimulated mRNA encoding adiponectin, leptin, AP2, and FAS, as well as PPARγ protein levels. Moreover, the expression of phosphorylated Akt (p-Akt) protein in TAO cells was up-regulated by IGF-1, while a specific PI3K inhibitor (LY294002) or an antibody of IGF-1R blocked this effect. These results indicate that IGF-1 is a pro-proliferative and pro-adipogenic factor in TAO OADSCs. IGF-1 enhances the adipogenesis of TAO OADSCs by up-regulation of PPARγ via the activation of the IGF-1R and PI3K pathways, suggesting that the blocking of IGF-1R or inhibition of PI3K signalling might be a potential novel therapeutic approach to TAO.

An in vitro comparison study: the effects of fetal bovine serum concentration on retinal progenitor cell multipotentiality

Retinal progenitor cells (RPCs) are an excellent resource for retinal replacement therapy, because they show enormous potential to differentiate into retinal-specific cell types. While the differentiating influence of serum has long been appreciated, the effects of serum concentration on RPC differentiation into specified retinal neural cells have not been investigated. Using cultured murine RPCs, this study compared the effects of different levels of fetal bovine serum (FBS) (1%, 5%, 10% and 20%) on RPC differentiation in vitro. RPC multipotentiality was assessed by using quantitative polymerase chain reaction (qPCR) to determine the relative expression levels of 10 genes involved in retinal development. In addition, analyses of cell morphology and retinal development-related protein expression were performed using microscopy and immunocytochemistry. The data revealed that 1% FBS-induced cultures preferentially generated rhodopsin- and PKC-α-positive cells. Calbindin and AP2α expression levels were greater in 5% FBS-induced cultures. Brn3a was expressed at similar levels in 1%, 5% and 10% FBS treatment conditions but diminished in 20% FBS conditions. Twenty percent FBS induced more glial fibrillary acid protein (GFAP)-immunoreactive cells corresponding to glia populations. These findings suggest that the concentration of FBS plays an important role in RPC differentiation in vitro. Treatment with low levels of FBS favors differentiation of rhodopsin-positive photoreceptors, interneurons and retinal ganglion cells (RGCs), while high FBS concentrations preferentially induce differentiation of glia cells. These results are expected to facilitate research in the treatment of neurodegenerative retinal diseases.