Basic fibroblast growth factor expression is implicated in mesenchymal stem cells response to light-induced retinal injury

Therapeutic effect against retinal neovascularization in a mouse model of oxygen-induced retinopathy: bone marrow-derived mesenchymal stem cells versus Conbercept

Background

To study the therapeutic effect of bone marrow-derived mesenchymal stem cells (BMSC) against retinal neovascularization and to compare with anti-vascular endothelial growth factor (VEGF) therapy.

Methods

Neonatal C57BL/6 mice were exposed in hyperoxygen and returned to room air to develop oxygen-induced retinopathy (OIR). Red fluorescent protein-labeled BMSC and Conbercept were intravitreally injected into OIR mice, respectively. Inhibition of neovascularization and apoptosis in OIR mice were assessed through retinal angiography, histopathology and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay.

Results

BMSC were able to migrate and integrate into the host retina, significantly inhibit retinal neovascular tufts and remodel the capillary network after injecton. Treatment with BMSC increased the retinal vascular density, decreased the number of acellular capillaries and inhibited retinal cell death. This effect was not inferior to current anti-VEGF therapy by using Conbercept.

Conclusions

Intravitreal injection of BMSC exerts a protective effect against retinal neovascularization and offers a therapeutic strategy for oxygen-induced retinopathy.

Potential therapeutic application of mesenchymal stem cells in ophthalmology

At present a wide variety of methods have been proposed to treat eye disorders, drug therapies are most commonly used. It should be noted that effective treatment modalities especially for degeneration of the retina and optic nerve are lacking. In the last few years stem cell transplantation has been proposed as an alternative method. The opportunities that stem cells provide within clinical use are almost unlimited. These cells are presently applied to treat various traumatic and degenerative disorders due to their unique biologic properties. Stem cells have high proliferative capabilities and are a self-maintained population of cells capable of differentiating into different cell types. Thus, they are represent a very primary stage of a cell lineage. Their ability to differentiate into different pathways provides animals with great plasticity in the renewal of somatic cells in postnatal ontogenesis. Pre-clinical and clinical ophthalmology studies where mesenchymal stem cells are applied and various methods of their administration are discussed herein. In addition the safety and efficacy of using bone marrow- and adipose tissue-derived mesenchymal stem cells have been discussed.

Over-expression of CNTF in bone marrow mesenchymal stem cells protects RPE cells from short-wavelength, blue-light injury

Increasing evidence has demonstrated that excessive blue-light (BL) with high photochemical energy and phototoxicity could induce apoptosis in retinal pigment epithelium (RPE) cells. RPE apoptosis leads to retina damage and further aggravate age-related macular degeneration (ARMD). Because of their neuroprotective, plasticity, and immunomodulatory ability, bone marrow mesenchymal stem cells (BMSCs) are recognized for retinal neuroprotection. RPE cells possess ciliary neurotrophic factor (CNTF) receptor complexes and can respond to CNTF; hence, we investigated the effects of BMSCs over-expressing CNTF on BL-injured RPE cells. BL-injured RPE cells were co-cultured with CNTF-BMSCs and GFP-BMSCs for 24 and 48 h. Superoxide dismutase and malondialdehyde assays were conducted to examine the effects of CNTF-BMSCs on the oxidative stress of RPE cells. VEGF protein secretion by RPE was determined by ELISA, and western blotting analysis was used to determine apoptotic protein expression and autophagic flux. Immunofluorescence was used to demonstrate the relationship between autophagy and apoptosis. We found that CNTF-BMSCs enhanced antioxidant capacity, decreased VEGF secretion, promoted autophagic flux, and inhibited apoptosis in BL-injured RPE cells, compared to GFP-BMSCs. Our findings suggest that CNTF over-expression enhances the protective effects of BMSCs on RPE cells, thus indicating subretinal-transplantation of CNTF-BMSCs may be a promising therapy for BL-injured retina.

MiR-218 Induces Neuronal Differentiation of ASCs in a Temporally Sequential Manner with Fibroblast Growth Factor by Regulation of the Wnt Signaling Pathway

Differentiation of neural lineages from mesenchymal stem cells has raised the hope of generating functional cells as seed cells for nerve tissue engineering. As important gene regulators, microRNAs (miRNAs) have been speculated to play a vital role in accelerating stem cell differentiation and repairing neuron damage. However, miRNA roles in directing differentiation of stem cells in current protocols are underexplored and the mechanisms of miRNAs as regulators of neuronal differentiation remain ambiguous. In this study, we have determined that miR-218 serves as crucial constituent regulator in neuronal differentiation of adipose stem cells (ASCs) through Wnt signaling pathway based on comprehensive annotation of miRNA sequencing data. Moreover, we have also discovered that miR-218 and Fibroblast Growth Factor-2 (FGF2) modulate neuronal differentiation in a sequential manner. These findings provide additional understanding of the mechanisms regulating stem cell neuronal differentiation as well as a new method for neural lineage differentiation of ASCs.

Mesenchymal stem cells attenuate hydrogen peroxide-induced oxidative stress and enhance neuroprotective effects in retinal ganglion cells

The apoptosis of retinal ganglion cells leads to visual impairment and blindness in ocular neurodegenerative diseases, especially in diabetic retinopathy (DR). Mounting evidence suggests that oxidative stress contributes to the pathogenesis of DR. In the present study, we investigated whether bone mesenchymal stem cells (BMSCs) have protective ability to relieve hydrogen peroxide (H₂O₂)-induced injury on retinal ganglion cells in vitro. An immortalized retinal ganglion cells, RGC-5 cells, were exposed to an indicated concentration of H₂O₂ for 24 h. Cell viability was analyzed by CCK-8 assay to find out a certain concentration to build H₂O₂ oxidative damage model. Morphological changes in RGC-5 cells were observed under optical microscope, and cell apoptosis was detected with Hoechst fluorescence staining. Then, BMSCs were co-cultured with RGC-5 cells in a transwell culture system for 24 h and 48 h. Flow cytometry was performed to qualify the apoptosis rate of RGC-5 cells. Conditioned medium was collected for evaluation the inflammatory cytokines by ELISA. The content of intracellular malondialdehyde (MDA) and superoxide dismutase (SOD) was assayed by thiobarbituric acid and xanthine oxidase method, respectively. qRT-PCR and ELISA were conducted for analysis of the expression changes in brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), respectively. After H₂O₂ exposure, the morphological varieties were observed as cytoplasm shrinking and paramorphia together with nuclear gathering. Meanwhile, the apoptotic cells had hyperfluorescence with Hoechst 33258 staining. Co-culture with BMSCs significantly inhibited retinal cell death. It was found that BMSCs reduced H₂O₂-induced inflammatory factors IL-1β and TNF-α, down-regulated intracellular oxidant factor MDA, up-regulated intracellular antioxidant factor SOD, and increased neurotrophins BDNF and CNTF expression. BMSCs may enhance protective effect of RGC-5 cells in H₂O₂-induced damage through improving antioxidant capacity, inhibiting pro-inflammatory cytokine secretion, and promoting neurotrophin expression.

Mesenchymal Stem Cells Modulate Light-induced Activation of Retinal Microglia Through CX3CL1/CX3CR1 Signaling

PURPOSE

To evaluate the effect of CX3CL1/CX3CR1 signaling on the interaction between mesenchymal stem cells (MSCs) and retinal microglia.

METHODS

Supernatants of homogenized retina were harvested from light-damaged SD rats (ISHR) to stimulated retinal microglia. Stimulated microglia were cocultured with MSCs, CX3CL1 over-expressing MSCs (CX3CL1-MSCs) or CX3CL1-blocked MSCs (anti-CX3CL1-MSCs) for 24 hours, and their molecular and functional changes were examined. Moreover, soluble CX3CL1 was directly added to microglia cultures.

RESULTS

ISHR stimulation activated retinal microglia. MSCs coculture inhibited the protein expression of pro-inflammatory factors by activated microglia, increased the protein expression of neurotrophic factors, and was accompanied with upregulation of CX3CR1. Meanwhile, MSCs suppressed proliferative and migratory function of activated microglia, but promoted the phagocytic capability. These effects were strengthened by CX3CL1- MSCs, and reversed by anti-CX3CL1-MSCs. Soluble CX3CL1 could enhanced microglial migration.

CONCLUSIONS

MSCs might restore homeostatic functions of retinal microglia responded to light damage mainly through CX3CL1/CX3CR1 signaling.

Stem cell therapies for age-related macular degeneration: the past, present, and future

In the developed world, age-related macular degeneration (AMD) is one of the major causes of irreversible blindness in the elderly. Although management of neovascular AMD (wet AMD) has dramatically progressed, there is still no effective treatment for nonneovascular AMD (dry AMD), which is characterized by retinal pigment epithelial (RPE) cell death (or dysfunction) and microenvironmental disruption in the retina. Therefore, RPE replacement and microenvironmental regulation represent viable treatments for dry AMD. Recent advances in cell biology have demonstrated that RPE cells can be easily generated from several cell types (pluripotent stem cells, multipotent stem cells, or even somatic cells) by spontaneous differentiation, coculturing, defined factors or cell reprogramming, respectively. Additionally, in vivo studies also showed that the restoration of visual function could be obtained by transplanting functional RPE cells into the subretinal space of recipient. More importantly, clinical trials approved by the US government have shown promising prospects in RPE transplantation. However, key issues such as implantation techniques, immune rejection, and xeno-free techniques are still needed to be further investigated. This review will summarize recent advances in cell transplantation for dry AMD. The obstacles and prospects in this field will also be discussed.