Neuroprotective effect of intravitreal cell-based glucagon-like peptide-1 production in the optic nerve crush model

Anti-inflammatory effect of glucagon-like Peptide-1 receptor agonist on the neurosensory retina in an acute optic nerve injury rat model

PURPOSE

To explore the possibility of using glucagon-like peptide-1 receptor agonist (GLP-1RA) as a new treatment for neuroinflammation, by analyzing retinal pathological changes in an optic nerve crush rat model.

METHODS

Eight-week-old male Sprague-Dawley rats were divided into lixisenatide (LIX, n = 10), traumatic control (T-CON, n = 10), and normal control (n = 5) groups. The optic nerves of left eyes in the LIX and T-CON groups were crushed in a standardized manner. The LIX group was treated with subcutaneous injections of lixisenatide (200 μg/kg/day) for 5 days. One week after initiating treatment, quantitative polymerase chain reaction, Western blot, and immunohistochemistry analyses were performed on the retinal tissues of each group to identify inflammatory markers.

RESULTS

The LIX group showed significantly lower mRNA levels of interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), thioredoxin interacting protein (TXNIP), and glial fibrillary acidic protein (GFAP) than the T-CON group. Also, the LIX group exhibited decreased TXNIP and GFAP expression compared with the T-CON group, and similar expression to the normal control group, according to Western blot analysis. Significantly increased immunohistochemistry staining of Brn3a and decreased TUNEL staining were seen in the LIX group compared with the T-CON group, indicating that lixisenatide contributes to retinal ganglion cell survival in cases of acute optic nerve injury.

CONCLUSIONS

Neuroinflammation was significantly reduced in lixisenatide-treated retinas compared with untreated retinas in our acute optic nerve injury rat model. The neuroprotective effect of lixisenatide indicates that it can serve a new treatment option against clinically intractable traumatic optic neuropathy.

Liraglutide Treatment Does Not Induce Changes in the Peripapillary Retinal Nerve Fiber Layer Thickness in Patients with Diabetic Retinopathy

Purpose: Liraglutide treatment has shown promising anti-inflammatory and nerve regenerative results in preclinical and clinical trials. We sought to assess if liraglutide treatment would induce nerve regeneration through its anti-inflammatory and neurotrophic mechanisms by increasing peripapillary retinal nerve fiber layer (RNFL) thickness in individuals with long-term type 1 diabetes. Methods: Secondary analyses were performed on a prospective, double-blinded, randomized, placebo-controlled trial on adults with type 1 diabetes, distal symmetric polyneuropathy (DSPN), and confirmed diabetic retinopathy, who were randomized 1:1 to either 26 weeks placebo or liraglutide treatment. The primary endpoint was a change in peripapillary RNFL thickness between treatments, assessed by optical coherence tomography. Results: Thirty-seven participants were included in the secondary analysis. No differences in mean peripapillary RNFL thickness (overall ΔMean RNFL thickness; liraglutide -1 (±8) μm (-1%) vs. placebo -1 (±5) μm (-1%), P = 0.78, n = 37) or any of the quadrants. Peripapillary RNFL thicknesses were shown between treatments in either nonproliferative (ΔMean RNFL thickness; liraglutide -1 (±5) μm (-1%) vs. placebo 0 (±4) μm (0%), P = 0.80, N = 26) or proliferative diabetic retinopathy subgroup (ΔMean RNFL thickness; liraglutide -2 (±14) μm (-3%) vs. placebo -1 (±6) μm (-2%), P = 0.88, N = 11). Conclusions: In this study, 26 weeks of liraglutide treatment did not induce measurable changes in the assessed optic nerve thickness. Thus, this methodology does not support the induction of substantial nerve regeneration in this cohort with established retinopathy and DSPN. The trial was approved by the Danish Health and Medicines Authority. Informed consent was obtained from all participants. TODINELI study: EUDRA CT: 2013-004375-12, Ethics Ref: N-20130077 Clinical trial registration number: clinicaltrials.gov NCT02138045.

Protective effects of intravitreal administration of mesenchymal stem cell-derived exosomes in an experimental model of optic nerve injury

Traumatic optic neuropathy results in the loss of retinal ganglion cells (RGCs), leading to unavoidable visual impairment. However, there is no effective therapy by far. Accumulated studies support the perception that mesenchymal stem cells (MSCs) secrete exosomes that serve as a protective paracrine factor. The study aimed to explore and evaluate the potential therapeutic effects of intravitreal transplantation of MSC-derived exosomes (MSC-exos) in an experimental model of optic nerve crush (ONC). Exosomes were isolated from rat MSCs and characterized by transmission electron microscope and western blotting. At the onset of ONC, a single intravitreal injection of exosomes or PBS was administered to the rats. At day 30, hematoxylin and eosin staining, immunohistochemistry, and βIII-tubulin staining were performed to evaluate the survival of RGCs. Moreover, TUNEL assay was used to examine the apoptosis of RGCs. Inflammation-relevant factors were identified via quantitative polymerase chain reaction. The expression levels of cell apoptosis-related molecules and key members of the PI3K/AKT signaling pathway were determined via western blot analysis. We found that MSC-exos exhibited typical characteristic morphologies (cup-shaped) and sizes (peak size of 93 nm). Furthermore, they exhibited substantial expression of the exosome markers CD63 and TSG101, but lacked the expression of the cellular marker GM130. Treatment with intravitreal MSC-exos notably promoted the survival of RGCs in ONC rats. The level of pro-inflammatory cytokines, including TNF-α, IL-1β, IL-6, IL-8, and MCP-1, were reduced, whereas those of the anti-inflammatory factor IL-10 were increased. Moreover, the apoptosis induced by ONC was decreased by the administration of MSC-exos via upregulation of the Bcl-2/Bax ratio and downregulation of caspase-3 activity. Furthermore, MSC-exos significantly stimulated AKT phosphorylation, whereas LY294002 restored the apoptosis-preventing effects of MSC-exos. The results of our results demonstrated that intravitreal administration of MSC-exos ameliorates ONC-induced injury in a rat model. These findings might aid in the development of effective exosome-based therapeutic strategies for the treatment of optic nerve degeneration.

Agonist of growth hormone-releasing hormone enhances retinal ganglion cell protection induced by macrophages after optic nerve injury

Optic neuropathies are leading causes of irreversible visual impairment and blindness, currently affecting more than 100 million people worldwide. Glaucoma is a group of optic neuropathies attributed to progressive degeneration of retinal ganglion cells (RGCs). We have previously demonstrated an increase in survival of RGCs by the activation of macrophages, whereas the inhibition of macrophages was involved in the alleviation on endotoxin-induced inflammation by antagonist of growth hormone-releasing hormone (GHRH). Herein, we hypothesized that GHRH receptor (GHRH-R) signaling could be involved in the survival of RGCs mediated by inflammation. We found the expression of GHRH-R in RGCs of adult rat retina. After optic nerve crush, subcutaneous application of GHRH agonist MR-409 or antagonist MIA-602 promoted the survival of RGCs. Both the GHRH agonist and antagonist increased the phosphorylation of Akt in the retina, but only agonist MR-409 promoted microglia activation in the retina. The antagonist MIA-602 reduced significantly the expression of inflammation-related genes Il1b, Il6, and Tnf Moreover, agonist MR-409 further enhanced the promotion of RGC survival by lens injury or zymosan-induced macrophage activation, whereas antagonist MIA-602 attenuated the enhancement in RGC survival. Our findings reveal the protective effect of agonistic analogs of GHRH on RGCs in rats after optic nerve injury and its additive effect to macrophage activation, indicating a therapeutic potential of GHRH agonists for the protection of RGCs against optic neuropathies especially in glaucoma.

Updates on Genes and Genetic Mechanisms Implicated in Primary Angle-Closure Glaucoma

Primary angle-closure glaucoma (PACG) is estimated to affect over 30 million people worldwide by 2040 and is highly prevalent in the Asian population. PACG is more severe and carries three times the higher risk of blindness than primary open-angle glaucoma, thus representing a significant public health concern. High heritability and ethnic-specific predisposition to PACG suggest the involvement of genetic factors in disease development. In the recent past, genetic studies have led to the successful identification of several genes and loci associated with PACG across different ethnicities. The precise cellular and molecular roles of these multiple loci in the development and progression of PACG remains to be elucidated. Nonetheless, these studies have significantly increased our understanding of the emerging cellular processes and biological pathways that might provide more significant insights into the disease’s genetic etiology and may be valuable for future clinical applications. This review aims to summarize and update the current knowledge of PACG genetics analysis research.

Repurposing GLP1 agonists for neurodegenerative diseases

There is a large unmet medical need to find disease modifying therapies against neurodegenerative diseases. This review summarizes data indicating that insulin resistance occurs in neurodegeneration and strategies to normalize insulin sensitivity in neurons may provide neuroprotective actions. In particular, recent preclinical and clinical studies in Parkinson's disease and Alzheimer's disease have indicated that glucagon-like peptide 1 (GLP1) agonism and dipeptidyl peptidase-4 inhibition may exert neuroprotection. Mechanistic insights from these studies and future directions for drug development against neurodegeneration based on GLP1 agonism are discussed.

Relationships Between Neurodegeneration and Vascular Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and constitutes a major cause of vision impairment and blindness in the world. DR has long been described exclusively as a microvascular disease of the eye. However, in recent years, a growing interest has been focused on the contribution of neuroretinal degeneration to the pathogenesis of the disease, and there are observations suggesting that neuronal death in the early phases of DR may favor the development of microvascular abnormalities, followed by the full manifestation of the disease. However, the mediators that are involved in the crosslink between neurodegeneration and vascular changes have not yet been identified. According to our hypothesis, vascular endothelial growth factor (VEGF) could probably be the most important connecting link between the death of retinal neurons and the occurrence of microvascular lesions. Indeed, VEGF is known to play important neuroprotective actions; therefore, in the early phases of DR, it may be released in response to neuronal suffering, and it would act as a double-edged weapon inducing both neuroprotective and vasoactive effects. If this hypothesis is correct, then any retinal stress causing neuronal damage should be accompanied by VEGF upregulation and by vascular changes. Similarly, any compound with neuroprotective properties should also induce VEGF downregulation and amelioration of the vascular lesions. In this review, we searched for a correlation between neurodegeneration and vasculopathy in animal models of retinal diseases, examining the effects of different neuroprotective substances, ranging from nutraceuticals to antioxidants to neuropeptides and others and showing that reducing neuronal suffering also prevents overexpression of VEGF and vascular complications. Taken together, the reviewed evidence highlights the crucial role played by mediators such as VEGF in the relationship between retinal neuronal damage and vascular alterations and suggests that the use of neuroprotective substances could be an efficient strategy to prevent the onset or to retard the development of DR.

Neuroprotective Peptides in Retinal Disease

In the pathogenesis of many disorders, neuronal death plays a key role. It is now assumed that neurodegeneration is caused by multiple and somewhat converging/overlapping death mechanisms, and that neurons are sensitive to unique death styles. In this respect, major advances in the knowledge of different types, mechanisms, and roles of neurodegeneration are crucial to restore the neuronal functions involved in neuroprotection. Several novel concepts have emerged recently, suggesting that the modulation of the neuropeptide system may provide an entirely new set of pharmacological approaches. Neuropeptides and their receptors are expressed widely in mammalian retinas, where they exert neuromodulatory functions including the processing of visual information. In multiple models of retinal diseases, different peptidergic substances play neuroprotective actions. Herein, we describe the novel advances on the protective roles of neuropeptides in the retina. In particular, we focus on the mechanisms by which peptides affect neuronal death/survival and the vascular lesions commonly associated with retinal neurodegenerative pathologies. The goal is to highlight the therapeutic potential of neuropeptide systems as neuroprotectants in retinal diseases.

GLP-1's role in neuroprotection: a systematic review

Glucagon-like peptide 1 (GLP-1) is a target for treatment of diabetes; however, its function in the brain is not well studied. In this systematic review, we aimed to analyze the neuroprotective role of GLP-1 and its defined mechanisms. Methods: We searched 'Web of Science' and 'Pubmed' to identify relevant studies using GLP-1 as the keyword. Two hundred and eighty-nine clinical and preclinical studies have been included. Data have been presented by grouping neurodegenerative, neurovascular and specific cell culture models. Results: Recent literature shows that GLP-1 and its agonists, DPP-4 inhibitors and combined GLP-1/GIP molecules are effective in partially or fully reversing the effects of neurotoxic compounds, neurovascular complications of diabetes, neuropathological changes related with Alzheimer's disease, Parkinson's disease or vascular occlusion. Possible mechanisms that provide neuroprotection are enhancing the viability of the neurons and restoring neurite outgrowth by increased neurotrophic factors, increasing subventricular zone progenitor cells, decreasing apoptosis, decreasing the level of pro-inflammatory factors, and strengthening blood-brain barrier. Conclusion: Based on the preclinical studies, GLP-1 modifying agents are promising targets for neuroprotection. On the other hand, the number of clinical studies that investigate GLP-1 as a treatment is low and further clinical trials are needed for a benchside to bedside translation of recent findings.

Methods to Induce Chronic Ocular Hypertension: Reliable Rodent Models as a Platform for Cell Transplantation and Other Therapies

Glaucoma, a form of progressive optic neuropathy, is the second leading cause of blindness worldwide. Being a prominent disease affecting vision, substantial efforts are being made to better understand glaucoma pathogenesis and to develop novel treatment options including neuroprotective and neuroregenerative approaches. Cell transplantation has the potential to play a neuroprotective and/or neuroregenerative role for various ocular cell types (e.g., retinal cells, trabecular meshwork). Notably, glaucoma is often associated with elevated intraocular pressure, and over the past 2 decades, several rodent models of chronic ocular hypertension (COH) have been developed that reflect these changes in pressure. However, the underlying pathophysiology of glaucoma in these models and how they compare to the human condition remains unclear. This limitation is the primary barrier for using rodent models to develop novel therapies to manage glaucoma and glaucoma-related blindness. Here, we review the current techniques used to induce COH-related glaucoma in various rodent models, focusing on the strengths and weaknesses of the each, in order to provide a more complete understanding of how these models can be best utilized. To so do, we have separated them based on the target tissue (pre-trabecular, trabecular, and post-trabecular) in order to provide the reader with an encompassing reference describing the most appropriate rodent COH models for their research. We begin with an initial overview of the current use of these models in the evaluation of cell transplantation therapies.

Injectable Neurotrophic Factor Delivery System Supporting Retinal Ganglion Cell Survival and Regeneration Following Optic Nerve Crush

In general, neurons belonging to the central nervous system (CNS), such as retinal ganglion cells (RGCs), do not regenerate. Due to this, strategies have emerged aimed at protecting and regenerating these cells. Neurotrophic factor (NTF) supplementation has been a promising approach but is limited by length of delivery and delivery vehicle. For this study, we tested a polymeric delivery system (sulfonated reverse thermal gel or SRTG) engineered to deliver cilliary neurotrophic factor (CNTF), while also being injectable. A rat optic nerve crush (ONC) model was used to determine the neuroprotective and regenerative capacity of our system. The results demonstrate that one single intravitreal injection of SRTG-CNTF following ONC showed significant protection of RGC survival at both 1 and 2 week time points, when compared to the control groups. Furthermore, there was no significant difference in the RGC count between the eyes that received the SRTG-CNTF following ONC and a healthy control eye. Intravitreal injection of the polymer system also induced noticeable axon regeneration 500 μm downstream from the lesion site compared to all other control groups. There was a significant increase in Müller cell response in groups that received the SRTG-CNTF injection following optic nerve crush also indicative of a regenerative response. Finally, higher concentrations of CNTF released from SRTG-CNTF showed a protective effect on RGCs and Müller cell response at a longer time point (4 weeks). In conclusion, we were able to show a neuroprotective and regenerative effect of this polymer SRTG-CNTF delivery system and the viability for treatment of neurodegenerations.

Exploring Optic Nerve Axon Regeneration

Background:

Traumatic optic nerve injury is a leading cause of irreversible blindness across the world and causes progressive visual impairment attributed to the dysfunction and death of retinal ganglion cells (RGCs). To date, neither pharmacological nor surgical interventions are sufficient to halt or reverse the progress of visual loss. Axon regeneration is critical for functional recovery of vision following optic nerve injury. After optic nerve injury, RGC axons usually fail to regrow and die, leading to the death of the RGCs and subsequently inducing the functional loss of vision. However, the detailed molecular mechanisms underlying axon regeneration after optic nerve injury remain poorly understood.

Methods:

Research content related to the detailed molecular mechanisms underlying axon regeneration after optic nerve injury have been reviewed.

Results:

The present review provides an overview of regarding potential strategies for axonal regeneration of RGCs and optic nerve repair, focusing on the role of cytokines and their downstream signaling pathways involved in intrinsic growth program and the inhibitory environment together with axon guidance cues for correct axon guidance. A more complete understanding of the factors limiting axonal regeneration will provide a rational basis, which contributes to develop improved treatments for optic nerve regeneration. These findings are encouraging and open the possibility that clinically meaningful regeneration may become achievable in the future.

Conclusion:

Combination of treatments towards overcoming growth-inhibitory molecules and enhancing intrinsic growth capacity combined with correct guidance using axon guidance cues is crucial for developing promising therapies to promote axon regeneration and functional recovery after ON injury.

Glucagon-like Peptide-1 and the Central/Peripheral Nervous System: Crosstalk in Diabetes

Glucagon-like peptide-1 (GLP-1) is released in response to meals and exerts important roles in the maintenance of normal glucose homeostasis. GLP-1 is also important in the regulation of neurologic and cognitive functions. These actions are mediated via neurons in the nucleus of the solitary tract that project to multiple regions expressing GLP-1 receptors (GLP-1Rs). Treatment with GLP-1R agonists (GLP-1-RAs) reduces ischemia-induced hyperactivity, oxidative stress, neuronal damage and apoptosis, cerebral infarct volume, and neurologic damage, after cerebral ischemia, in experimental models. Ongoing human trials report a neuroprotective effect of GLP-1-RAs in Alzheimer's and Parkinson's disease. In this review, we discuss the role of GLP-1 and GLP-1-RAs in the nervous system with focus on GLP-1 actions on appetite regulation, glucose homeostasis, and neuroprotection.

Intravitreal triamcinolone acetonide, retinal microglia and retinal ganglion cell apoptosis in the optic nerve crush model

PURPOSE

To evaluate the effect of intravitreal triamcinolone acetonide (TA) on the activation of retinal microglia cells (RMGCs) and survival of retinal ganglion cells (RGCs) in an optic nerve crush (ONC) model.

METHODS

Adult female Sprague-Dawley rats underwent a standardized ONC and either received an intravitreal injection of TA (TA group) or of phosphate-buffered saline (PBS, PBS group) in the right eyes. At 1, 3, 7, 14 and 28 days after the ONC, the animals were killed. The retinas were examined by immunohistochemistry, light microscopy, Western blot or retrograde labelling of RGCs by fluorogold injected into the superior colliculi.

RESULTS

The TA group as compared to the PBS control group showed a significantly (p < 0.0001) lower density of activated RMGCs, at 14 days [4.2 ± 1.6 versus 9.3 ± 2.2 cells/high-power microscopic field (HPF)] and at 28 days (2.3 ± 1.1 versus 4.4 ± 1.5 cells/HPF), and with a significantly lower expression of inflammatory factors. Central density of RGCs as stained by haematoxylin-eosin or by fluorogold was significantly (all p < 0.05) more reduced in the PBS group than in the TA group at days 14 and 28 after baseline. The survival rate (cell density in the study eye as compared to cell density in the contralateral unaffected eye) was significantly higher in the TA group than in the PBS group on days 14 (58% versus 45%; p = 0.003) and 28 (52% versus 41%; p = 0.022).

CONCLUSIONS

Intravitreal TA as compared to intravitreal PBS was associated with a lower density of activated RMGCs and a higher density of surviving RGCs in an ONC model.

Stem cell treatment of degenerative eye disease

Stem cell therapies are being explored extensively as treatments for degenerative eye disease, either for replacing lost neurons, restoring neural circuits or, based on more recent evidence, as paracrine-mediated therapies in which stem cell-derived trophic factors protect compromised endogenous retinal neurons from death and induce the growth of new connections. Retinal progenitor phenotypes induced from embryonic stem cells/induced pluripotent stem cells (ESCs/iPSCs) and endogenous retinal stem cells may replace lost photoreceptors and retinal pigment epithelial (RPE) cells and restore vision in the diseased eye, whereas treatment of injured retinal ganglion cells (RGCs) has so far been reliant on mesenchymal stem cells (MSC). Here, we review the properties of non-retinal-derived adult stem cells, in particular neural stem cells (NSCs), MSC derived from bone marrow (BMSC), adipose tissues (ADSC) and dental pulp (DPSC), together with ESC/iPSC and discuss and compare their potential advantages as therapies designed to provide trophic support, repair and replacement of retinal neurons, RPE and glia in degenerative retinal diseases. We conclude that ESCs/iPSCs have the potential to replace lost retinal cells, whereas MSC may be a useful source of paracrine factors that protect RGC and stimulate regeneration of their axons in the optic nerve in degenerate eye disease. NSC may have potential as both a source of replacement cells and also as mediators of paracrine treatment.

Towards retinal ganglion cell regeneration

Traumatic optic nerve injury and glaucoma are among the leading causes of incurable vision loss across the world. What is worse, neither pharmacological nor surgical interventions are significantly effective in reversing or halting the progression of vision loss. Advances in cell biology offer some hope for the victims of optic nerve damage and subsequent partial or complete visual loss. Retinal ganglion cells (RGCs) travel through the optic nerve and carry all visual signals to the brain. After injury, RGC axons usually fail to regrow and die, leading to irreversible loss of vision. Various kinds of cells and factors possess the ability to support the process of axon regeneration for RGCs. This article summarizes the latest advances in RGC regeneration.

Successful subretinal delivery and monitoring of MicroBeads in mice

Background

To monitor viability of implanted genetically engineered and microencapsulated human stem cells (MicroBeads) in the mouse eye, and to study the impact of the beads and/or xenogenic cells on retinal integrity.

Methodology/Principal Findings

MicroBeads were implanted into the subretinal space of SV126 wild type mice using an ab externo approach. Viability of microencapsulated cells was monitored by noninvasive retinal imaging (Spectralis™ HRA+OCT). Retinal integrity was also assessed with retinal imaging and upon the end of the study by light and electron microscopy. The implanted GFP-marked cells encapsulated in subretinal MicroBeads remained viable over a period of up to 4 months. Retinal integrity and viability appeared unaltered apart from the focal damage due to the surgical implantation, GFAP upregulation, and opsin mistargeting in the immediate surrounding tissue.

Conclusions/Significance

The accessibility for routine surgery and its immune privileged state make the eye an ideal target for release system implants for therapeutic substances, including neurotrophic and anti-angiogenic compounds or protein based biosimilars. Microencapsulated human stem cells (MicroBeads) promise to overcome limitations inherent with single factor release systems, as they are able to produce physiologic combinations of bioactive compounds.

Neuroprotective and neurotrophic actions of glucagon-like peptide-1: an emerging opportunity to treat neurodegenerative and cerebrovascular disorders

Like type-2 diabetes mellitus (T2DM), neurodegenerative disorders and stroke are an ever increasing, health, social and economic burden for developed Westernized countries. Age is an important risk factor in all of these; due to the rapidly increasing rise in the elderly population T2DM and neurodegenerative disorders, both represent a looming threat to healthcare systems. Whereas several efficacious drugs are currently available to ameliorate T2DM, effective treatments to counteract pathogenic processes of neurodegenerative disorders are lacking and represent a major scientific and pharmaceutical challenge. Epidemiological data indicate an association between T2DM and most major neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. Likewise, there is an association between T2DM and stroke incidence. Studies have revealed that common pathophysiological features, including oxidative stress, insulin resistance, abnormal protein processing and cognitive decline, occur across these. Based on the presence of shared mechanisms and signalling pathways in these seemingly distinct diseases, one could hypothesize that an effective treatment for one disorder could prove beneficial in the others. Glucagon-like peptide-1 (GLP-1)-based anti-diabetic drugs have drawn particular attention as an effective new strategy to not only regulate blood glucose but also to reduce apoptotic cell death of pancreatic beta cells in T2DM. Evidence supports a neurotrophic and neuroprotective role of GLP-1 receptor (R) stimulation in an increasing array of cellular and animal neurodegeneration models as well as in neurogenesis. Herein, we review the physiological role of GLP-1 in the nervous system, focused towards the potential benefit of GLP-1R stimulation as an immediately translatable treatment strategy for acute and chronic neurological disorders.

Encapsulated glucagon-like peptide-1-producing mesenchymal stem cells have a beneficial effect on failing pig hearts

Stem cell therapy is an exciting and emerging treatment option to promote post-myocardial infarction (post-MI) healing; however, cell retention and efficacy in the heart remain problematic. Glucagon-like peptide-1 (GLP-1) is an incretin hormone with cardioprotective properties but a short half-life in vivo. The effects of prolonged GLP-1 delivery from stromal cells post-MI were evaluated in a porcine model. Human mesenchymal stem cells immortalized and engineered to produce a GLP-1 fusion protein were encapsulated in alginate (bead-GLP-1 MSC) and delivered to coronary artery branches. Control groups were cell-free beads and beads containing unmodified MSCs (bead-MSC), n = 4-5 per group. Echocardiography confirmed left ventricular (LV) dysfunction at time of delivery in all groups. Four weeks after intervention, only the bead-GLP-1 MSC group demonstrated LV function improvement toward baseline and showed decreased infarction area compared with controls. Histological analysis showed reduced inflammation and a trend toward reduced apoptosis in the infarct zone. Increased collagen but fewer myofibroblasts were observed in infarcts of the bead-GLP-1 MSC and bead-MSC groups, and significantly more vessels per mm(2) were noted in the infarct of the bead-GLP-1 MSC group. No differences were observed in myocyte cross-sectional area between groups. Post-MI delivery of GLP-1 encapsulated genetically modified MSCs provided a prolonged supply of GLP-1 and paracrine stem cell factors, which improved LV function and reduced epicardial infarct size. This was associated with increased angiogenesis and an altered remodeling response. Combined benefits of paracrine stem cell factors and GLP-1 were superior to those of stem cells alone. These results suggest that encapsulated genetically modified MSCs would be beneficial for recovery following MI.

Cell transplantation approaches to retinal ganglion cell neuroprotection in glaucoma

Glaucoma is a complex neurodegenerative disease that involves interactions among multiple signaling pathways, ultimately leading to progressive retinal ganglion cell (RGC) death. The development of neuroprotective approaches to glaucoma therapy could preserve vision by modulating these pathologic pathways or by acting directly on RGCs to attenuate cell death and maintain function. Intraocular cell transplantation is being evaluated as one approach to achieve sustained RGC neuroprotection. Unlike traditional pharmacological approaches, transplanted cells might be capable of simultaneously targeting multiple pro-survival pathways via local delivery of secreted factors and/or via modulation of the intraocular microenvironment. Elucidating the mechanisms by which different cell types attenuate RGC death in models of glaucoma may uncover additional novel mechanisms of neuroprotection. In this review, we will discuss the rationale for transplantation-based approaches to neuroprotection for glaucoma and explore the various mechanisms of action proposed to account for RGC neuroprotection achieved by two distinct cell classes that have been studied most extensively for this purpose: glial cells and mesenchymal stem cells.