Human neural progenitor cells promote photoreceptor survival in retinal explants

Cellular Localization and Distribution of TGF-β1, GDNF and PDGF-BB in the Adult Primate Central Nervous System

The available data on the localization of transforming growth factor beta1 (TGF-β1), glial cell line-derived neurotrophic factor (GDNF), and platelet-derived growth factor-BB (PDGF-BB) in the adult primate and human central nervous system (CNS) are limited and lack comprehensive and systematic information. This study aimed to investigate the cellular localization and distribution of TGF-β1, GDNF, and PDGF-BB in the CNS of adult rhesus macaque (Macaca mulatta). Seven adult rhesus macaques were included in the study. The protein levels of TGF-β1, PDGF-BB, and GDNF in the cerebral cortex, cerebellum, hippocampus, and spinal cord were analyzed by western blotting. The expression and location of TGF-β1, PDGF-BB, and GDNF in the brain and spinal cord was examined by immunohistochemistry and immunofluorescence staining, respectively. The mRNA expression of TGF-β1, PDGF-BB, and GDNF was detected by in situ hybridization. The molecular weight of TGF-β1, PDGF-BB, and GDNF in the homogenate of spinal cord was 25 KDa, 30 KDa, and 34 KDa, respectively. Immunolabeling revealed GDNF was ubiquitously distributed in the cerebral cortex, hippocampal formation, basal nuclei, thalamus, hypothalamus, brainstem, cerebellum, and spinal cord. TGF-β1 was least distributed and found only in the medulla oblongata and spinal cord, and PDGF-BB expression was also limited and present only in the brainstem and spinal cord. Besides, TGF-β1, PDGF-BB, and GDNF were localized in the astrocytes and microglia of spinal cord and hippocampus, and their expression was mainly found in the cytoplasm and primary dendrites. The mRNA of TGF-β1, PDGF-BB, and GDNF was localized to neuronal subpopulations in the spinal cord and cerebellum. These findings suggest that TGF-β1, GDNF and PDGF-BB may be associated with neuronal survival, neural regeneration and functional recovery in the CNS of adult rhesus macaques, providing the potential insights into the development or refinement of therapies based on these factors.

Reduced Retinal Degeneration in an Oxidative Stress Organ Culture Model through an iNOS-Inhibitor

Simple Summary

There is an urgent need to develop new therapeutic approaches for diseases of the retina, like glaucoma. In their pathogenesis, oxidative stress and the corresponding defense reactions play an important role. In porcine retinal organ cultures, hydrogen peroxide can be used to simulate oxidative stress. In the present study, we investigated whether the treatment with an inducible nitric oxide synthase inhibitor protects retinal cells from oxidative stress. Therefore, porcine retinal explants were damaged with hydrogen peroxide and treated with the nitric oxide synthase inhibitor. Analyzes of the retina at four and eight days showed that a inhibitor was able to prevent degeneration in porcine retinas, since retinal ganglion cells were protected to some extent. Moreover, in the later course, there was also protection of other retinal cells (bipolar cells). Hence, this inhibitor seems to be a promising treatment option for retinal diseases.

Abstract

In retinal organ cultures, H₂O₂ can be used to simulate oxidative stress, which plays a role in the development of several retinal diseases including glaucoma. We investigated whether processes underlying oxidative stress can be prevented in retinal organ cultures by an inducible nitric oxide synthase (iNOS)-inhibitor. To this end, porcine retinal explants were cultivated for four and eight days. Oxidative stress was induced via 300 µM H₂O₂ on day one for three hours. Treatment with the iNOS-inhibitor 1400 W was applied simultaneously, remaining for 72 h. Retinal ganglion cells (RGC), bipolar and amacrine cells, apoptosis, autophagy, and hypoxia were evaluated immunohistologically and by RT-qPCR. Additionally, RGC morphology was analyzed via transmission electron microscopy. H₂O₂-induced RGCs loss after four days was prevented by the iNOS-inhibitor. Additionally, electron microscopy revealed a preservation from oxidative stress in iNOS-inhibitor treated retinas at four and eight days. A late rescue of bipolar cells was seen in iNOS-inhibitor treated retinas after eight days. Hypoxic stress and apoptosis almost reached the control situation after iNOS-inhibitor treatment, especially after four days. In sum, the iNOS-inhibitor was able to prevent strong H₂O-induced degeneration in porcine retinas. Hence, this inhibitor seems to be a promising treatment option for retinal diseases.

Coculture techniques for modeling retinal development and disease, and enabling regenerative medicine

Stem cell-derived retinal organoids offer the opportunity to cure retinal degeneration of wide-ranging etiology either through the study of in vitro models or the generation of tissue for transplantation. However, despite much work in animals and several human pilot studies, satisfactory therapies have not been developed. Two major challenges for retinal regenerative medicine are (a) physical cell-cell interactions, which are critical to graft function, are not formed and (b) the host environment does not provide suitable queues for development. Several strategies offer to improve the delivery, integration, maturation, and functionality of cell transplantation. These include minimally invasive delivery, biocompatible material vehicles, retinal cell sheets, and optogenetics. Optimizing several variables in animal models is practically difficult, limited by anatomical and disease pathology which is often different to humans, and faces regulatory and ethical challenges. High-throughput methods are needed to experimentally optimize these variables. Retinal organoids will be important to the success of these models. In their current state, they do not incorporate a representative retinal pigment epithelium (RPE)-photoreceptor interface nor vascular elements, which influence the neural retina phenotype directly and are known to be dysfunctional in common retinal diseases such as age-related macular degeneration. Advanced coculture techniques, which emulate the RPE-photoreceptor and RPE-Bruch's-choriocapillaris interactions, can incorporate disease-specific, human retinal organoids and overcome these drawbacks. Herein, we review retinal coculture models of the neural retina, RPE, and choriocapillaris. We delineate the scientific need for such systems in the study of retinal organogenesis, disease modeling, and the optimization of regenerative cell therapies for retinal degeneration.

Retina in a dish: Cell cultures, retinal explants and animal models for common diseases of the retina

For many retinal diseases, including age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy (DR), the exact pathogenesis is still unclear. Moreover, the currently available therapeutic options are often unsatisfactory. Research designed to remedy this situation heavily relies on experimental animals. However, animal models often do not faithfully reproduce human disease and, currently, there is strong pressure from society to reduce animal research. Overall, this creates a need for improved disease models to understand pathologies and develop treatment options that, at the same time, require fewer or no experimental animals. Here, we review recent advances in the field of in vitro and ex vivo models for AMD, glaucoma, and DR. We highlight the difficulties associated with studies on complex diseases, in which both the initial trigger and the ensuing pathomechanisms are unclear, and then delineate which model systems are optimal for disease modelling. To this end, we present a variety of model systems, ranging from primary cell cultures, over organotypic cultures and whole eye cultures, to animal models. Specific advantages and disadvantages of such models are discussed, with a special focus on their relevance to putative in vivo disease mechanisms. In many cases, a replacement of in vivo research will mean that several different in vitro models are used in conjunction, for instance to analyze and validate causative molecular pathways. Finally, we argue that the analytical decomposition into appropriate cell and tissue model systems will allow making significant progress in our understanding of complex retinal diseases and may furthermore advance the treatment testing.

Evaluation of Congo Red Staining in Degenerating Porcine Photoreceptors In Vitro: Protective Effects by Structural and Trophic Support

Congo red (CR) is a histological stain used for the detection of extracellular amyloids mediating various neurodegenerative diseases. Given that damaged photoreceptors appear to degenerate similarly to other nerve cells, CR staining was evaluated in experimentally injured porcine retina. CR staining appeared mostly as discrete cytosolic deposits with no obvious plaque formation during the investigated time period. Increases of CR labeling coincided temporally with the known accumulation of mislocalized opsins and increases of cell death. Coculture, either with human retinal pigment epithelium (ARPE) or human neural progenitor (ReN) cells, was accompanied by a significant reduction of CR labeling. Of particular interest was the reduction of CR labeling in cone photoreceptors, which are important for the perception of color and fine details and afflicted in age-related macular degeneration (AMD). Electron microscopy revealed inclusions in the inner segment, cell body, and occasionally synaptic terminals of photoreceptor cells in cultured specimens. Closer examinations indicated the presence of different types of inclusions resembling protein aggregates as well as inclusion bodies. The current results indicate that injury-related response resulted in accumulation of CR deposits in photoreceptor cells, and that trophic and/or structural support attenuated this response.

Human neural progenitor cells decrease photoreceptor degeneration, normalize opsin distribution and support synapse structure in cultured porcine retina

Retinal neurodegenerative disorders like retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy and retinal detachment decrease retinal functionality leading to visual impairment. The pathological events are characterized by photoreceptor degeneration, synaptic disassembly, remodeling of postsynaptic neurons and activation of glial cells. Despite intense research, no effective treatment has been found for these disorders. The current study explores the potential of human neural progenitor cell (hNPC) derived factors to slow the degenerative processes in adult porcine retinal explants. Retinas were cultured for 3 days with or without hNPCs as a feeder layer and investigated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), immunohistochemical, western blot and quantitative real time-polymerase chain reaction (qRT-PCR) techniques. TUNEL showed that hNPCs had the capacity to limit photoreceptor cell death. Among cone photoreceptors, hNPC coculture resulted in better maintenance of cone outer segments and reduced opsin mislocalization. Additionally, maintained synaptic structural integrity and preservation of second order calbindin positive horizontal cells was also observed. However, Müller cell gliosis only seemed to be alleviated in terms of reduced Müller cell density. Our observations indicate that at 3 days of coculture, hNPC derived factors had the capacity to protect photoreceptors, maintain synaptic integrity and support horizontal cell survival. Human neural progenitor cell applied treatment modalities may be an effective strategy to help maintain retinal functionality in neurodegenerative pathologies. Whether hNPCs can independently hinder Müller cell gliosis by utilizing higher concentrations or by combination with other pharmacological agents still needs to be determined.

Osmotic induction of placental growth factor in retinal pigment epithelial cells in vitro: contribution of NFAT5 activity

One risk factor of neovascular age-related macular degeneration is systemic hypertension; hypertension is mainly caused by extracellular hyperosmolarity after consumption of dietary salt. In retinal pigment epithelial (RPE) cells, high extracellular osmolarity induces vascular endothelial growth factor (VEGF)-A (Hollborn et al. in Mol Vis 21:360-377, 2015). The aim of the present study was to determine whether extracellular hyperosmolarity and chemical hypoxia trigger the expression of further VEGF family members including placental growth factor (PlGF) in human RPE cells. Hyperosmotic media were made up by addition of 100 mM NaCl or sucrose. Chemical hypoxia was induced by CoCl2. Gene expression was quantified by real-time RT-PCR, and secretion of PlGF-2 was investigated with ELISA. Nuclear factor of activated T cell 5 (NFAT5) was depleted using siRNA. Extracellular hyperosmolarity triggered expression of VEGF-A, VEGF-D, and PlGF genes, and secretion of PlGF-2. Hypoosmolarity decreased PlGF gene expression. Hypoxia induced expression of VEGF-A, VEGF-B, VEGF-D, and PlGF genes. Extracellular hyperosmolarity and hypoxia produced additive PlGF gene expression. Both hyperosmolarity and hypoxia induced expression of KDR and FLT-4 receptor genes, while hyperosmolarity caused neuropilin-2 and hypoxia neuropilin-1 gene expression. The hyperosmotic, but not the hypoxic, PlGF gene expression was in part mediated by NFAT5. The expression of PlGF in RPE cells depends on the extracellular osmolarity. The data suggest that high consumption of dietary salt may exacerbate the angiogenic response of RPE cells in the hypoxic retina via transcriptional activation of various VEGF family member genes.

Stem cell approaches to glaucoma: from aqueous outflow modulation to retinal neuroprotection

Long-term pharmacological management of glaucoma currently relies on self-administered drugs to regulate intraocular pressure (IOP). A number of approaches using stem cells have recently shown promise as potential future treatment strategies complementary to IOP lowering. Several sources of endogenous stem cells have been identified in the eye, some of which may be able to repair the damaged trabecular meshwork and restore functional regulation of aqueous outflow. Neural and mesenchymal stem cells secrete growth factors which provide neuroprotective effects, reducing loss of retinal ganglion cells (RGCs) in animal models. In the future, stem cells may even replace RGCs to reform functional connections between the eye and the brain, although the complexity of such a repair task is formidable. With advances in biomaterial cell scaffolds and concurrent efforts in other neural systems, stem cell therapies are becoming a realistic option for treating multiple eye diseases, and despite ongoing challenges, there are reasons for optimism that stem cells may play a role in the treatment of human glaucoma in the future.

A Subsequent Human Neural Progenitor Transplant into the Degenerate Retina Does Not Compromise Initial Graft Survival or Therapeutic Efficacy

PURPOSE

Stem and progenitor cell transplantation provides a promising clinical application for treating degenerative retinal diseases, including age-related macular degeneration (AMD) and retinitis pigmentosa (RP). Our previous studies have shown that a single subretinal injection of human cortical-derived neural progenitor cells (hNPCctx) into cyclosporine-treated Royal College of Surgeons (RCS) rats preserved both photoreceptors and visual function. However, it is still unknown whether nonautologous progenitor cell readministration for sustained vision is efficacious and safe in terms of the initial graft initiating an immune response to a subsequent graft.

METHODS

A cell suspension containing 3×104 hNPCctx into one eye of cyclosporine-treated RCS rats at postnatal day 21 (P21), followed by a second transplantation at P95 into the previously untreated fellow eye.

RESULTS

hNPCctx delayed photoreceptor degeneration and preserved visual function, as measured by electroretinography (ERG), optokinetic response (OKR), and luminance threshold recordings (LTRs). Visual function and photoreceptors of the initially treated eye were still preserved 6 weeks after hNPCctx were injected into the second eye. Antibodies against T-cell markers showed that CD3, CD4, and CD8 T cells were not detected at P90 and P140 in most cases. No detectable level of anti-nestin antibody was found in serum by enzyme-linked immunosorbent assay (ELISA).

CONCLUSIONS

This xenograft study with cyclosporine-treated animals demonstrates that readministration of hNPCctx into the fellow eye did not induce anti-graft immune responses or lower therapeutic efficacy of hNPCctx in preserving vision. Thus, readministration of progenitor cells to sustain long-term efficacy may be an option for long-term therapies of retinal degeneration.

TRANSLATIONAL RELEVANCE

Redosing neural progenitors do not affect the efficacy of the initial grafts in protecting vision or induce unwanted immune responses.

Silver and gold nanoparticles exposure to in vitro cultured retina--studies on nanoparticle internalization, apoptosis, oxidative stress, glial- and microglial activity

The complex network of neuronal cells in the retina makes it a potential target of neuronal toxicity – a risk factor for visual loss. With growing use of nanoparticles (NPs) in commercial and medical applications, including ophthalmology, there is a need for reliable models for early prediction of NP toxicity in the eye and retina. Metal NPs, such as gold and silver, gain much of attention in the ophthalmology community due to their potential to cross the barriers of the eye. Here, NP uptake and signs of toxicity were investigated after exposure to 20 and 80 nm Ag- and AuNPs, using an in vitro tissue culture model of the mouse retina. The model offers long-term preservation of retinal cell types, numbers and morphology and is a controlled system for delivery of NPs, using serum-free defined culture medium. AgNO₃-treatment was used as control for toxicity caused by silver ions. These end-points were studied; gross morphological organization, glial activity, microglial activity, level of apoptosis and oxidative stress, which are all well described as signs of insult to neural tissue. TEM analysis demonstrated cellular- and nuclear uptake of all NP types in all neuronal layers of the retina. Htx-eosin staining showed morphological disruption of the normal complex layered retinal structure, vacuole formation and pyknotic cells after exposure to all Ag- and AuNPs. Significantly higher numbers of apoptotic cells as well as an increased number of oxidative stressed cells demonstrated NP-related neuronal toxicity. NPs also caused increased glial staining and microglial cell activation, typical hallmarks of neural tissue insult. This study demonstrates that low concentrations of 20 and 80 nm sized Ag- and AuNPs have adverse effects on the retina, using an organotypic retina culture model. Our results motivate careful assessment of candidate NP, metallic or-non-metallic, to be used in neural systems for therapeutic approaches.

Stem cell therapy for glaucoma: possibilities and practicalities

Glaucoma is a progressive, neurodegenerative, optic neuropathy in which currently available therapies cannot always prevent, and do not reverse, vision loss. Stem cell transplantation may provide a promising new avenue for treating many presently incurable degenerative conditions, including glaucoma. This article will explore the various ways in which transplantation of stem or progenitor cells may be applied for the treatment of glaucoma. We will critically discuss the translational prospects of two cell transplantation-based treatment modalities: neuroprotection and retinal ganglion cell replacement. In addition, we will identify specific questions that need to be addressed and obstacles to overcome on the path to clinical translation, and offer insight into potential strategies for approaching this goal.

Protective effects of placental growth factor on retinal neuronal cell damage

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor family. Although it has been reported that PlGF protects against neuronal damage in the brain, little is known about the effects of PlGF in the retina. Therefore, we investigated the effects of PlGF on retinal neuronal cells. To evaluate the effects of PlGF against L-buthionine-(S,R)-sulfoximine (BSO)/glutamate cell death, oxygen-glucose deprivation (OGD)-induced cell death, and light-induced cell death, RGC-5 and 661W cells were used. We evaluated the mechanism responsible for the protective effects of PlGF against retinal neuronal cell death by performing the examinations with U1026, which is a mitogen-activated protein kinase (MEK) inhibitor, and LY294002, which is a phosphoinositide 3-kinase (PI3K) inhibitor. In addition, we measured caspase-3/7 activity in RGC-5 cells and 661W cells. PlGF protected against RGC-5 cell death induced by BSO/glutamate and OGD and against 661W cell death induced by light irradiation. Moreover, an anti-PlGF antibody negated these protective effects. The protective effects of PlGF against OGD-induced RGC-5 cell death and light-induced 661W cell death were suppressed by using an anti-PlGF antibody, U1026, and LY294002. Treatment with PlGF suppressed caspase-3/7 activity in both cell lines. We demonstrated for the first time that PlGF exerts a protective effect by inhibiting the activation of caspase-3/7 through the MEK and PI3K pathway in retinal neuronal cells. These data suggest that PlGF may be an important protective factor in the retina.

VEGF induces neuroglial differentiation in bone marrow-derived stem cells and promotes microglia conversion following mobilization with GM-CSF

PURPOSE

Evaluation of potential tropic effects of vascular endothelial growth factor (VEGF) on the incorporation and differentiation of bone-marrow-derived stem cells (BMSCs) in a murine model of anterior ischemic optic neuropathy (AION).

METHODS

In the first approach, small-sized subset of BMCs were isolated from GFP donors mice by counterflow centrifugal elutriation and depleted of hematopoietic lineages (Fr25lin(-)). These cells were injected into a peripheral vein (1 × 10(6) in 0.2 ml) or inoculated intravitreally (2 × 10(5)) to syngeneic mice, with or without intravitreal injection of 5 μg/2μL VEGF, simultaneously with AION induction. In a second approach, hematopoietic cells were substituted by myelablative transplant of syngeseic GFP + bone marrow cells. After 3 months, progenitors were mobilized with granulocyte-macrophage colony-stimulating factor (GM-CSF) followed by VEGF inoculation into the vitreous body and AION induction . Engraftment and phenotype were examined by immunohistochemistry and FISH at 4 and 24 weeks post-transplantation, and VEGF receptors were determined by real time PCR.

RESULTS

VEGF had no quantitative effect on incorporation of elutriated cells in the injured retina, yet it induced early expression of neuroal markers in cells incorporated in the RGC layer and promoted durable gliosis, most prominent perivascular astrocytes. These effects were mediated by VEGF-R1/Flt-1, which is constitutively expresses in the elutriated fraction of stem cells. Mobilization with GM-CSF limited the differentiation of bone marrow progenitors to microglia, which was also fostered by VEGF.

CONCLUSIONS

VEGF signaling mediated by Flt-1 induces early neural and sustained astrocytic differentiation of stem cells elutriated from adult bone-marrow, with significant contribution to stabilization retinal architecture following ischemic injury.

Neuronal differentiation and extensive migration of human neural precursor cells following co-culture with rat auditory brainstem slices

Congenital or acquired hearing loss is often associated with a progressive degeneration of the auditory nerve (AN) in the inner ear. The AN is composed of processes and axons of the bipolar spiral ganglion neurons (SGN), forming the connection between the hair cells in the inner ear cochlea and the cochlear nuclei (CN) in the brainstem (BS). Therefore, replacement of SGNs for restoring the AN to improve hearing function in patients who receive a cochlear implantation or have severe AN malfunctions is an attractive idea. A human neural precursor cell (HNPC) is an appropriate donor cell to investigate, as it can be isolated and expanded in vitro with maintained potential to form neurons and glia. We recently developed a post-natal rodent in vitro auditory BS slice culture model including the CN and the central part of the AN for initial studies of candidate cells. Here we characterized the survival, distribution, phenotypic differentiation, and integration capacity of HNPCs into the auditory circuitry in vitro. HNPC aggregates (spheres) were deposited adjacent to or on top of the BS slices or as a monoculture (control). The results demonstrate that co-cultured HNPCs compared to monocultures (1) survive better, (2) distribute over a larger area, (3) to a larger extent and in a shorter time-frame form mature neuronal and glial phenotypes. HNPC showed the ability to extend neurites into host tissue. Our findings suggest that the HNPC-BS slice co-culture is appropriate for further investigations on the integration capacity of HNPCs into the auditory circuitry.

Stromal factors SDF1α, sFRP1, and VEGFD induce dopaminergic neuron differentiation of human pluripotent stem cells

Human embryonic stem cell (hESC)-derived dopaminergic (DA) neurons hold potential for treating Parkinson's disease (PD) through cell replacement therapy. Generation of DA neurons from hESCs has been achieved by coculture with the stromal cell line PA6, a source of stromal cell-derived inducing activity (SDIA). However, the factors produced by stromal cells that result in SDIA are largely undefined. We previously reported that medium conditioned by PA6 cells can generate functional DA neurons from NTera2 human embryonal carcinoma stem cells. Here we show that PA6-conditioned medium can induce DA neuronal differentiation in both NTera2 cells and the hESC I6 cell line. To identify the factor(s) responsible for SDIA, we used large-scale microarray analysis of gene expression combined with mass spectrometric analysis of PA6-conditioned medium (CM). The candidate factors, hepatocyte growth factor (HGF), stromal cell-derived factor-1 α (SDF1α), secreted frizzled-related protein 1 (sFRP1), and vascular endothelial growth factor D (VEGFD) were identified, and their concentrations in PA6 CM were established by immunoaffinity capillary electrophoresis. Upon addition of SDF1α, sFRP1, and VEGFD to the culture medium, we observed an increase in the number of cells expressing tyrosine hydroxylase (a marker for DA neurons) and βIII-tubulin (a marker for immature neurons) in both the NTera2 and I6 cell lines. These results indicate that SDF1α, sFRP1, and VEGFD are major components of SDIA and suggest the potential use of these defined factors to elicit DA differentiation of pluripotent human stem cells for therapeutic intervention in PD.

GM-CSF protects rat photoreceptors from death by activating the SRC-dependent signalling and elevating anti-apoptotic factors and neurotrophins

BACKGROUND

The term retinitis pigmentosa (RP) comprises a heterogeneous group of hereditary and sporadic human retinal degenerative diseases. The molecular and cellular events still remain obscure, thus hiding effective therapies. Granulocyte–macrophage colony-stimulating factor (GM-CSF) is a hematopoietic factor which plays a crucial role in protecting neuronal cells. Binding of GM-CSF to its receptor induces several intracellular signaling pathways and kinases. Here we examined whether GM-CSF has a neuroprotective effect on photoreceptor degeneration in Royal College of Surgeons (RCS) rats.

METHODS

GM-CSF was injected into the vitreous body of RCS rats either once at the onset of photoreceptor degeneration at day 21, or twice at day 21 and day 42. At day 84, when photoreceptor degeneration is completed, the rats were sacrificed, their eyes enucleated and processed for histological staining and counting the surviving photoreceptor nuclei. The expression of apoptosis-related factors, such as BAD, APAF1 and BCL-2 was examined by Western blot analysis. The expression of neurotrophins such as ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF), and glia-derived neurotrophic actor (GDNF), as well as glial fibrillary acidic protein (GFAP) was analysed by Western blots and immunohistochemistry. The expression of JAK/STAT, ERK1/2 and SRC pathway proteins was assessed by Western blot analysis.

RESULTS

GM-CSF protects significantly against photoreceptor degeneration in comparison to control group. After a single injection of GM-CSF at P21, a 4-fold increase of photoreceptors was observed, whereas eyes which received a repeated injection of GM-CSF at P42 showed a 10-fold increase of photoreceptors. Western blot analysis revealed a decreased BAD and an increased pBAD and BCL-2 expression, indicating changed expression profiles of apoptosis-related proteins. Neurotrophic factors examined are up-regulated, whereas GFAP was also modulated. At cell signalling levels, GM-CSF activates SRC-dependent STAT3 which is independent of JAK2, while proteins of the ERK1/2 pathway are not affected.

CONCLUSIONS

The data suggest that GM-CSF is a potent therapeutic agent in photoreceptor degeneration caused by mutation of the receptor tyrosine kinase gene (Mertk), and may be also effective in other photoreceptor degeneration.

Comparison of the effect between pegaptanib and ranibizumab on exudative age-related macular degeneration with small lesion size

PURPOSE

To compare the effect of pegaptanib versus ranibizumab on exudative age-related macular degeneration (AMD) with small lesion size.

METHODS

This is a retrospective study of 81 eyes from 78 patients with exudative AMD treated and followed up over 12 months. Patients with baseline best corrected visual acuity (BCVA) under 20/400 and with a greatest linear dimension of lesion over 4500 μm were excluded from the study. Twenty-six eyes from 25 patients were treated with three consecutive intravitreal injections of pegaptanib (IVP group) and 55 eyes from 54 patients were treated with three consecutive ranibizumab injections (IVR group). Each therapy was repeated as needed. The alteration in BCVA was evaluated in the IVP and IVR groups.

RESULTS

No differences were detected in baseline parameters between the IVP and IVR groups. The mean BCVA (logMAR) at month 1, 3, 6 and 12 after the initial treatment was improved from baseline in the IVP group (-0.095, -0.17, -0.18 and -0.18, respectively) and in the IVR group (-0.077, -0.15, -0.17 and -0.11, respectively), which was statistically significant. There was no difference in the change in mean BCVA between IVP and IVR groups at the same time periods.

CONCLUSIONS

The visual outcome of IVP was equivalent with IVR in exudative AMD with small lesion size.

Protocols for investigating microRNA functions in human neural progenitor cells

Human embryonic stem cells and induced pluripotent stem cells offer great hope for studies of pathogenic mechanisms of disease and cell-based therapies. One powerful approach to manipulate the behaviors of human stem cells and their progenies is through microRNAs (miRNAs), a class of small noncoding RNAs that regulate gene expression at the posttranscriptional level. Each miRNA may target up to hundreds of mRNAs; some are specifically expressed in progenitor cells and affect multiple cellular processes. Here we present experimental protocols for investigating the endogenous functions of specific miRNAs in the proliferation, survival, and migration of human neural progenitor cells derived from embryonic stem cells. These methods may be applicable to protein factors and neural progenitor cells derived from patient-specific induced pluripotent stem cells.