Hypoxic-Preconditioned Bone Marrow Stem Cell Medium Significantly Improves Outcome After Retinal Ischemia in Rats

Research hotspots and frontiers of preconditioning in cerebral ischemia: A bibliometric analysis

Background

Preconditioning is a promising strategy against ischemic brain injury, and numerous studies in vitro and in vivo have demonstrated its neuroprotective effects. However, at present there is no bibliometric analysis of preconditioning in cerebral ischemia. Therefore, a comprehensive overview of the current status, hot spots, and emerging trends in this research field is necessary.

Materials and methods

Studies on preconditioning in cerebral ischemia from January 1999-December 2022 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace was used for data mining and visual analysis.

Results

A total of 1738 papers on preconditioning in cerebral ischemia were included in the study. The annual publications showed an upwards and then downwards trend but currently remain high in terms of annual publications. The US was the leading country, followed by China, the most active country in recent years. Capital Medical University published the largest number of articles. Perez-Pinzon, Miguel A contributed the most publications, while KITAGAWA K was the most cited author. The focus of the study covered three areas: (1) relevant diseases and experimental models, (2) types of preconditioning and stimuli, and (3) mechanisms of ischemic tolerance. Remote ischemic preconditioning, preconditioning of mesenchymal stem cells (MSCs), and inflammation are the frontiers of research in this field.

Conclusion

Our study provides a visual and scientific overview of research on preconditioning in cerebral ischemia, providing valuable information and new directions for researchers.

Potential of mesenchymal stem cell-derived conditioned medium/secretome as a therapeutic option for ocular diseases

Research has shown that the therapeutic effect of mesenchymal stem cells (MSCs) is partially due to its secreted factors as opposed to the implantation of the cells into the treated tissue or tissue replacement. MSC secretome, especially in the form of conditioned medium (MSC-CM) is now being explored as an alternative to MSCs transplantation. Despite the observed benefits of MSC-CM, only a few clinical trials have evaluated it and other secretome components in the treatment of eye diseases. This review provides insight into the potential therapeutic use of MSC-CM in eye conditions, such as corneal diseases, dry eye, glaucoma, retinal diseases and uveitis. We discuss the current evidence, some limitations, and the progress that remains to be achieved before clinical translation becomes possible.

Advances in the applications of mesenchymal stem cell-conditioned medium in ocular diseases

Mesenchymal stem cell-conditioned medium (MSC-CM), also known as secretome, is secreted by MSC and contains a variety of bioactive factors with anti-inflammatory, anti-apoptotic, neuroprotection, and proliferation effects. Increasing evidence proved that MSC-CM plays an important role in various diseases, including skin, bone, muscle, and dental diseases. However, the role of MSC-CM in ocular diseases is not quite clear, Therefore, this article reviewed the composition, biological functions, preparation, and characterization of MSC-CM and summarized current research advances in different sources of MSC-CM in corneal and retinal diseases, including dry eye, corneal epithelial damage, chemical corneal injury, retinitis pigmentosa (RP), anterior ischemic optic neuropathy (AION), diabetic retinopathy (DR), and other retinal degenerative changes. For these diseases, MSC-CM can promote cell proliferation, reduce inflammation and vascular leakage, inhibit retinal cell degeneration and apoptosis, protect corneal and retinal structures, and further improves visual function. Hence, we summarize the production, composition and biological functions of MSC-CM and focus on describing its mechanisms in the treatment of ocular diseases. Furthermore, we look at the unexplored mechanisms and further research directions for MSC-CM based therapy in ocular diseases.

MicroRNA-based engineering of mesenchymal stem cell extracellular vesicles for treatment of retinal ischemic disorders: Engineered extracellular vesiclesand retinal ischemia

Mesenchymal stem cell (MSCs)-derived extracellular vesicles (EVs) are emerging therapeutic tools. Hypoxic pre-conditioning (HPC) of MSCs altered the production of microRNAs (miRNAs) in EVs, and enhanced the cytoprotective, anti-inflammatory, and neuroprotective properties of their derivative EVs in retinal cells. EV miRNAs were identified as the primary contributors of these EV functions. Through miRNA seq analyses, miRNA-424 was identified as a candidate for the retina to overexpress in EVs for enhancing cytoprotection and anti-inflammatory effects. FEEs (functionally engineered EVs) overexpressing miR424 (FEE424) significantly enhanced neuroprotection and anti-inflammatory activities in vitro in retinal cells. FEE424 functioned by reducing inflammatory cytokine production in retinal microglia, and attenuating oxygen free radicals in retinal Muller cells and microvascular endothelial cells, providing a multi-pronged approach to enhancing recovery after retinal ischemic insult. In an in vivo model of retinal ischemia, native, HPC, and FEE424 MSC EVs robustly and similarly restored function to close to baseline, and prevented loss of retinal ganglion cells, but HPC EVs provided the most effective attenuation of apoptosis-related and inflammatory cytokine gene expression. These results indicate the potential for EV engineering to produce ameliorative effects for retinal diseases with a significant inflammatory component. STATEMENT OF SIGNIFICANCE: We show that functionally engineered extracellular vesicles (FEEs) from mesenchymal stem cells (MSCs) provide cytoprotection in rat retina subjected to ischemia. FEEs overexpressing microRNA 424 (FEE424) function by reducing inflammatory cytokine production in retinal microglia, and attenuating oxygen free radicals in Muller cells and microvascular endothelial cells, providing a multi-pronged approach to enhancing recovery. In an in vivo model of retinal ischemia in rats, native, hypoxic-preconditioned (HPC), and FEE424 MSC EVs robustly and similarly restored function, and prevented loss of retinal ganglion cells, but HPC EVs provided the most effective attenuation of apoptosis-related and inflammatory cytokine gene expression. The results indicate the potential for EV engineering to produce ameliorative effects for retinal diseases with a significant inflammatory component.

A hypothermia mimetic molecule (zr17-2) reduces ganglion cell death and electroretinogram distortion in a rat model of intraorbital optic nerve crush (IONC)

Introduction: Ocular and periocular traumatisms may result in loss of vision. Our previous work showed that therapeutic hypothermia prevents retinal damage caused by traumatic neuropathy. We also generated and characterized small molecules that elicit the beneficial effects of hypothermia at normal body temperature. Here we investigate whether one of these mimetic molecules, zr17-2, is able to preserve the function of eyes exposed to trauma. Methods: Intraorbital optic nerve crush (IONC) or sham manipulation was applied to Sprague-Dawley rats. One hour after surgery, 5.0 µl of 330 nmol/L zr17-2 or PBS, as vehicle, were injected in the vitreum of treated animals. Electroretinograms were performed 21 days after surgery and a- and b-wave amplitude, as well as oscillatory potentials (OP), were calculated. Some animals were sacrificed 6 days after surgery for TUNEL analysis. All animal experiments were approved by the local ethics board. Results: Our previous studies showed that zr17-2 does not cross the blood-ocular barrier, thus preventing systemic treatment. Here we show that intravitreal injection of zr17-2 results in a very significant prevention of retinal damage, providing preclinical support for its pharmacological use in ocular conditions. As previously reported, IONC resulted in a drastic reduction in the amplitude of the b-wave (p < 0.0001) and OPs (p < 0.05), a large decrease in the number of RGCs (p < 0.0001), and a large increase in the number of apoptotic cells in the GCL and the INL (p < 0.0001). Interestingly, injection of zr17-2 largely prevented all these parameters, in a very similar pattern to that elicited by therapeutic hypothermia. The small molecule was also able to reduce oxidative stress-induced retinal cell death in vitro. Discussion: In summary, we have shown that intravitreal injection of the hypothermia mimetic, zr17-2, significantly reduces the morphological and electrophysiological consequences of ocular traumatism and may represent a new treatment option for this cause of visual loss.

Mesenchymal Stromal Cells Preconditioning: A New Strategy to Improve Neuroprotective Properties

Neurological diseases represent one of the main causes of disability in human life. Consequently, investigating new strategies capable of improving the quality of life in neurological patients is necessary. For decades, researchers have been working to improve the efficacy and safety of mesenchymal stromal cells (MSCs) therapy based on MSCs’ regenerative and immunomodulatory properties and multilinear differentiation potential. Therefore, strategies such as MSCs preconditioning are useful to improve their application to restore damaged neuronal circuits following neurological insults. This review is focused on preconditioning MSCs therapy as a potential application to major neurological diseases. The aim of our work is to summarize both the in vitro and in vivo studies that demonstrate the efficacy of MSC preconditioning on neuronal regeneration and cell survival as a possible application to neurological damage.

Modulation of Mesenchymal Stem Cells for Enhanced Therapeutic Utility in Ischemic Vascular Diseases

Mesenchymal stem cells are multipotent stem cells isolated from various tissue sources, including but not limited to bone marrow, adipose, umbilical cord, and Wharton Jelly. Although cell-mediated mechanisms have been reported, the therapeutic effect of MSCs is now recognized to be primarily mediated via paracrine effects through the secretion of bioactive molecules, known as the “secretome”. The regenerative benefit of the secretome has been attributed to trophic factors and cytokines that play neuroprotective, anti-angiogenic/pro-angiogenic, anti-inflammatory, and immune-modulatory roles. The advancement of autologous MSCs therapy can be hindered when introduced back into a hostile/disease environment. Barriers include impaired endogenous MSCs function, limited post-transplantation cell viability, and altered immune-modulatory efficiency. Although secretome-based therapeutics have gained popularity, many translational hurdles, including the heterogeneity of MSCs, limited proliferation potential, and the complex nature of the secretome, have impeded the progress. This review will discuss the experimental and clinical impact of restoring the functional capabilities of MSCs prior to transplantation and the progress in secretome therapies involving extracellular vesicles. Modulation and utilization of MSCs–secretome are most likely to serve as an effective strategy for promoting their ultimate success as therapeutic modulators.

Cell-Based Neuroprotection of Retinal Ganglion Cells in Animal Models of Optic Neuropathies

Retinal ganglion cells (RGCs) comprise a heterogenous group of projection neurons that transmit visual information from the retina to the brain. Progressive degeneration of these cells, as it occurs in inflammatory, ischemic, traumatic or glaucomatous optic neuropathies, results in visual deterioration and is among the leading causes of irreversible blindness. Treatment options for these diseases are limited. Neuroprotective approaches aim to slow down and eventually halt the loss of ganglion cells in these disorders. In this review, we have summarized preclinical studies that have evaluated the efficacy of cell-based neuroprotective treatment strategies to rescue retinal ganglion cells from cell death. Intraocular transplantations of diverse genetically nonmodified cell types or cells engineered to overexpress neurotrophic factors have been demonstrated to result in significant attenuation of ganglion cell loss in animal models of different optic neuropathies. Cell-based combinatorial neuroprotective approaches represent a potential strategy to further increase the survival rates of retinal ganglion cells. However, data about the long-term impact of the different cell-based treatment strategies on retinal ganglion cell survival and detailed analyses of potential adverse effects of a sustained intraocular delivery of neurotrophic factors on retina structure and function are limited, making it difficult to assess their therapeutic potential.

Mesenchymal Stem Cell Induced Foxp3(+) Tregs Suppress Effector T Cells and Protect against Retinal Ischemic Injury

Mesenchymal stem/stromal cells (MSC) are well known for immunomodulation; however, the mechanisms involved in their benefits in the ischemic retina are unknown. This study tested the hypothesis that MSC induces upregulation of transcription factor forkhead box protein P3 (Foxp3) in T cells to elicit immune modulation, and thus, protect against retinal damage. Induced MSCs (iMSCs) were generated by differentiating the induced pluripotent stem cells (iPSC) derived from urinary epithelial cells through a noninsertional reprogramming approach. In in-vitro cultures, iMSC transferred mitochondria to immune cells via F-actin nanotubes significantly increased oxygen consumption rate (OCR) for basal respiration and ATP production, suppressed effector T cells, and promoted differentiation of CD4+CD25+ T regulatory cells (Tregs) in coculture with mouse splenocytes. In in-vivo studies, iMSCs transplanted in ischemia-reperfusion (I/R) injured eye significantly increased Foxp3+ Tregs in the retina compared to that of saline-injected I/R eyes. Furthermore, iMSC injected I/R eyes significantly decreased retinal inflammation as evidenced by reduced gene expression of IL1β, VCAM1, LAMA5, and CCL2 and improved b-wave amplitudes compared to that of saline-injected I/R eyes. Our study demonstrates that iMSCs can transfer mitochondria to immune cells to suppress the effector T cell population. Additionally, our current data indicate that iMSC can enhance differentiation of T cells into Foxp3 Tregs in vitro and therapeutically improve the retina's immune function by upregulation of Tregs to decrease inflammation and reduce I/R injury-induced retinal degeneration in vivo.

Mesenchymal stem cell-derived exosomes: a promising vector in treatment for diabetes and its microvascular complications

Mesenchymal stem cell-derived exosomes (MSC-exos) are phospholipid bimolecular vesicles containing various materials, and they mediate crosstalk among cells. MSC-exos can maintain glucose homeostasis and delay the progression of diabetes and its microvascular complications through multiple mechanisms, such as by improving β-cell viability and insulin resistance as well as through multiple signal transduction pathways. However, related knowledge has not yet been systematically summarized. Therefore, we reviewed the applications and relevant mechanisms of MSC-exos in treatments for diabetes and its microvascular complications, particularly treatments for improving islet β-cells viability, insulin resistance, diabetic nephropathy, and retinopathy.

Interaction Between Mesenchymal Stem Cells and Retinal Degenerative Microenvironment

Retinal degenerative diseases (RDDs) are a group of diseases contributing to irreversible vision loss with yet limited therapies. Stem cell-based therapy is a promising novel therapeutic approach in RDD treatment. Mesenchymal stromal/stem cells (MSCs) have emerged as a leading cell source due to their neurotrophic and immunomodulatory capabilities, limited ethical concerns, and low risk of tumor formation. Several pre-clinical studies have shown that MSCs have the potential to delay retinal degeneration, and recent clinical trials have demonstrated promising safety profiles for the application of MSCs in retinal disease. However, some of the clinical-stage MSC therapies have been unable to meet primary efficacy end points, and severe side effects were reported in some retinal “stem cell” clinics. In this review, we provide an update of the interaction between MSCs and the RDD microenvironment and discuss how to balance the therapeutic potential and safety concerns of MSCs' ocular application.

Donor heart preservation with hypoxic-conditioned medium-derived from bone marrow mesenchymal stem cells improves cardiac function in a heart transplantation model

Background

In heart transplantation, donor hearts inevitably suffer from ischemia/reperfusion (I/R) injury, which leads to primary graft dysfunction and affects patients’ survival rate. Bone marrow mesenchymal stem cells (BMSCs) have been reported to attenuate myocardial I/R injury via their paracrine effects, which can be enhanced by hypoxic preconditioning. We hypothesized that the donor heart preservation with hypoxic conditioned medium (CdM) derived from BMSCs would improve post-transplant graft function.

Methods

Normoxic or hypoxic CdM were isolated from rat BMSCs cultured under normoxic (20% O₂) or hypoxic (1% O₂) condition. Donor hearts were explanted; stored in cardioplegic solution supplemented with either a medium (vehicle), normoxic CdM (N-CdM), or hypoxic CdM (H-CdM); and then heterotopically transplanted. Antibody arrays were performed to compare the differences between hypoxic and normoxic CdM.

Results

After heart transplantation, the donor heart preservation with normoxic CdM was associated with a shorter time to return of spontaneous contraction and left ventricular systolic diameter, lower histopathological scores, higher ejection fraction, and fractional shortening of the transplanted hearts. The cardioprotective effects may be associated with the inhibition of apoptosis and inflammation, as reflected by less TUNEL-positive cells and lower levels of plasma proinflammatory cytokines (interleukin-1β, interleukin-6, tumor necrosis factor-α) and cardiac troponin I in the N-CdM group compared with the vehicle group. These therapeutic effects can be further enhanced by hypoxic preconditioning. Antibody arrays revealed that nine proteins were significantly increased in hypoxic CdM compared with normoxic CdM. Furthermore, compared with vehicle and N-CdM groups, the protein levels of PI3K and p-Akt/Akt ratio in the transplanted hearts significantly increased in the H-CdM group. However, no significant difference was found in the phosphorylation of Smad2 and Smad3 for the donor hearts among the three groups.

Conclusions

Our results indicate that the cardioplegic solution-enriched with hypoxic CdM can be a novel and promising preservation solution for donor hearts.

Emergence of the Stem Cell Secretome in Regenerative Engineering

The secretome is defined as the set of molecules and biological factors that are secreted by cells into the extracellular space. In the past decade, secretome-based therapies have emerged as a promising approach to overcome the limitations associated with cell-based therapies for tissue and organ regeneration. Considering the growing number of recent publications related to secretome-based therapies, this review takes a step-by-step engineering approach to evaluate the role of the stem cell secretome in regenerative engineering. We discuss the functional benefits of the secretome, the techniques used to engineer the secretome and tailor its therapeutic effects, and the delivery systems and strategies that have been developed to use the secretome for tissue regeneration.

Hypoxia Enhances Mesenchymal Characteristics Maintenance of Buffalo Bone Marrow-Derived Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (BMSCs) from livestock are valuable resources for veterinary therapeutics and animal reproduction. Previous studies have shown that hypoxic conditions were beneficial in maintaining the mesenchymal feature of BMSCs. However, the effects of hypoxia on buffalo BMSCs (bBMSCs) remain unclear. In this study, the effects of hypoxic conditions on cell morphology, migration, polarity, and karyotype of bBMSCs were examined. The results showed that hypoxia (5% oxygen) enhanced colony formation and stress fiber synthesis of bBMSCs. Under the hypoxic culture conditions, the migration capacity and normal karyotype rate of bBMSCs were significantly improved (p < 0.05), which resulted in weakened cell polarity and enhanced karyotype stability in bBMSCs. In addition, it was significantly (p < 0.05) upregulated in the expression levels of HIF-TWIST signaling pathway axis-related genes (Hif-1, Hif-2, Twist, Snail, Slug, Fn1, N-cadherin, Collal). The HIF-TWIST axis of bBMSCs was also activated in hypoxia. Finally, it was more effective and easier to maintain the mesenchymal feature of bBMSCs in hypoxic conditions. These findings not only provide theoretical guidance to elucidate the detailed regulation mechanism of hypoxia on mesenchymal nature maintenance of bBMSCs, but also provide positive support to further establish the stable in vitro culture system of bBMSCs.

TNFα-Mediated Priming of Mesenchymal Stem Cells Enhances Their Neuroprotective Effect on Retinal Ganglion Cells

Purpose

To determine whether priming of bone marrow mesenchymal stem cells (MSCs) by signals from injured retina, particularly tumor necrosis factor α (TNFα), increase their exosomes’ neuroprotective efficacy on retinal ganglion cells (RGCs).

Methods

MSCs were primed with retinal cell culture conditioned medium, with or without the TNFα blocker etanercept or TNFα prior to isolation of exosomes. MSC conditioned medium or exosomes were added to rat retinal cultures or human stem cell–derived retinal ganglion cell (hRGC) cultures, and RGC neuroprotective effects were quantified. Luminex assays were used to compare primed versus unprimed exosomes.

Results

MSC conditioned medium and exosomes exerted a significant neuroprotective effect on injured rat and hRGC. This effect was significantly increased after MSCs were primed with retinal conditioned medium or TNFα. Blocking of TNFα signaling with etanercept prevented priming-induced RGC neuroprotective efficacy. Priming increased Pigment epithelium-derived factor (PEDF) and VEGF-AA exosomal abundance.

Conclusions

MSC exosomes promote RGC survival not just in rodent retinal cultures but also with hRGC. Their efficacy can be further enhanced through TNFα priming with the mechanism of action potentially mediated, at least in part, through increased levels of PEDF and VEGF-AA.

Mesenchymal stem cell-derived extracellular vesicles and retinal ischemia-reperfusion

Retinal ischemia is a major cause of vision loss and impairment and a common underlying mechanism associated with diseases such as glaucoma, diabetic retinopathy, and central retinal artery occlusion. The regenerative capacity of the diseased human retina is limited. Our previous studies have shown the neuroprotective effects of intravitreal injection of mesenchymal stem cells (MSC) and MSC-conditioned medium in retinal ischemia in rats. Based upon the hypothesis that the neuroprotective effects of MSCs and conditioned medium are largely mediated by extracellular vesicles (EVs), MSC derived EVs were tested in an in-vitro oxygen-glucose deprivation (OGD) model of retinal ischemia. Treatment of R28 retinal cells with MSC-derived EVs significantly reduced cell death and attenuated loss of cell proliferation. Mechanistic studies on the mode of EV endocytosis by retinal cells were performed in vitro. EV endocytosis was dose- and temperature-dependent, saturable, and occurred via cell surface heparin sulfate proteoglycans mediated by the caveolar endocytic pathway. The administration of MSC-EVs into the vitreous humor 24 h after retinal ischemia in a rat model significantly enhanced functional recovery, and decreased neuro-inflammation and apoptosis. EVs were taken up by retinal neurons, retinal ganglion cells, and microglia. They were present in the vitreous humor for four weeks after intravitreal administration, with saturable binding to vitreous humor components. Overall, this study highlights the potential of MSC-EV as biomaterials for neuroprotective and regenerative therapy in retinal disorders.

Hypoxic conditioned medium derived from bone marrow mesenchymal stromal cells protects against ischemic stroke in rats

In recent years, studies have shown that the secretome of bone marrow mesenchymal stromal cells (BMSCs) contains many growth factors, cytokines, and antioxidants, which may provide novel approaches to treat ischemic diseases. Furthermore, the secretome may be modulated by hypoxic preconditioning. We hypothesized that conditioned medium (CM) derived from BMSCs plays a crucial role in reducing tissue damage and improving neurological recovery after ischemic stroke and that hypoxic preconditioning of BMSCs robustly improves these activities. Rats were subjected to ischemic stroke by middle cerebral artery occlusion and then intravenously administered hypoxic CM, normoxic CM, or Dulbecco modified Eagle medium (DMEM, control). Cytokine antibody arrays and label-free quantitative proteomics analysis were used to compare the differences between hypoxic CM and normoxic CM. Injection of normoxic CM significantly reduced the infarct area and improved neurological recovery after stroke compared with administering DMEM. These outcomes may be associated with the attenuation of apoptosis and promotion of angiogenesis. Hypoxic preconditioning significantly enhanced these therapeutic effects. Fourteen proteins were significantly increased in hypoxic CM compared with normoxic CM as measured by cytokine arrays. The label-free quantitative proteomics analysis revealed 163 proteins that were differentially expressed between the two groups, including 107 upregulated proteins and 56 downregulated proteins. Collectively, our results demonstrate that hypoxic CM protected brain tissue from ischemic injury and promoted functional recovery after stroke in rats and that hypoxic CM may be the basis of a potential therapy for stroke patients.

Human Mesenchymal Stem Cells Expressing Erythropoietin Enhance Survivability of Retinal Neurons Against Oxidative Stress: An In Vitro Study

Retinal degeneration is a prominent feature in ocular disorders. In exploring possible treatments, Mesenchymal Stem Cells (MSCs) have been recognized to yield therapeutic role for retinal degenerative diseases. Studies have also displayed that erythropoietin (EPO) administration into degenerative retina models confers significant neuroprotective actions in limiting pathological cell death. In this study, we aimed to use MSCs to deliver EPO and to evaluate the ability of EPO to rescue retinal neurons from dying upon reactive oxidative stress induction. We derived human MSCs from Wharton's jelly (hWJMSCs) of the umbilical cord and cells were transduced with lentivirus particles encoding EPO and a reporter gene of green fluorescent protein (GFP). The supernatants of both transduced and non-transduced cells were collected and used as a pre-conditioning medium for Y79 retinoblastoma cells (retinal neuron cell line) following exposure to glutamate induction. Retinal cells exposed to glutamate showed reduced mitochondrial depolarization and enhanced improvement in cell viability when incubated with pre-conditioned media of transduced cells. Our results established a proof-of-concept that MSCs could be used as a candidate for the delivery of EPO therapeutic gene in the treatment of retinal degenerations.

Adaptive Plasticity in the Retina: Protection Against Acute Injury and Neurodegenerative Disease by Conditioning Stimuli

Although both preclinical and clinical conditioning studies in heart and brain lead the field of conditioning medicine, investigations of retinal conditioning still number more than 100. In this brief review, we highlight findings to date from animal and cell culture models of conditioning that provide demonstrated protection in acute and chronic retinal injury and disease models. The multitude of stimuli used to condition the retina, the signaling mediators and pathways identified, and the injury- and disease-resilient phenotypes documented are discussed herein, along with our recommendations for the kinds of studies needed to continue to advance this promising field. In our view, the robust protection afforded by these adaptive epigenetic responses to conditioning stress provides significant incentives for both furthering our investment in bench research and underwriting clinical trials, so that the full potential of this therapy can be realized.

Hypothermia Prevents Retinal Damage Generated by Optic Nerve Trauma in the Rat

Ocular and periocular traumatisms may result in loss of vision. Hypothermia provides a beneficial intervention for brain and heart conditions and, here, we study whether hypothermia can prevent retinal damage caused by traumatic neuropathy. Intraorbital optic nerve crush (IONC) or sham manipulation was applied to male rats. Some animals were subjected to hypothermia (8 °C) for 3 h following surgery. Thirty days later, animals were subjected to electroretinography and behavioral tests. IONC treatment resulted in amplitude reduction of the b-wave and oscillatory potentials of the electroretinogram, whereas the hypothermic treatment significantly (p < 0.05) reversed this process. Using a descending method of limits in a two-choice visual task apparatus, we demonstrated that hypothermia significantly (p < 0.001) preserved visual acuity. Furthermore, IONC-treated rats had a lower (p < 0.0001) number of retinal ganglion cells and a higher (p < 0.0001) number of TUNEL-positive cells than sham-operated controls. These numbers were significantly (p < 0.0001) corrected by hypothermic treatment. There was a significant (p < 0.001) increase of RNA-binding motif protein 3 (RBM3) and of BCL2 (p < 0.01) mRNA expression in the eyes exposed to hypothermia. In conclusion, hypothermia constitutes an efficacious treatment for traumatic vision-impairing conditions, and the cold-shock protein pathway may be involved in mediating the beneficial effects shown in the retina.

Cellular Reparative Mechanisms of Mesenchymal Stem Cells for Retinal Diseases

The use of multipotent mesenchymal stem cells (MSCs) has been reported as promising for the treatment of numerous degenerative disorders including the eye. In retinal degenerative diseases, MSCs exhibit the potential to regenerate into retinal neurons and retinal pigmented epithelial cells in both in vitro and in vivo studies. Delivery of MSCs was found to improve retinal morphology and function and delay retinal degeneration. In this review, we revisit the therapeutic role of MSCs in the diseased eye. Furthermore, we reveal the possible cellular mechanisms and identify the associated signaling pathways of MSCs in reversing the pathological conditions of various ocular disorders such as age-related macular degeneration (AMD), retinitis pigmentosa, diabetic retinopathy, and glaucoma. Current stem cell treatment can be dispensed as an independent cell treatment format or with the combination of other approaches. Hence, the improvement of the treatment strategy is largely subjected by our understanding of MSCs mechanism of action.

Bone-marrow mesenchymal stem-cell administration significantly improves outcome after retinal ischemia in rats

PURPOSE

Ischemia-associated retinal degeneration is one of the leading causes of vision loss, and to date, there are no effective treatment options. We hypothesized that delayed injection of bone-marrow stem cells (BMSCs) 24 h after the onset of ischemia could effectively rescue ischemic retina from its consequences, including apoptosis, inflammation, and increased vascular permeability, thereby preventing retinal cell loss.

METHODS

Retinal ischemia was induced in adult Wistar rats by increasing intraocular pressure (IOP) to 130-135 mmHg for 55 min. BMSCs harvested from rat femur were injected into the vitreous 24 h post-ischemia. Functional recovery was assessed 7 days later using electroretinography (ERG) measurements of the a-wave, b-wave, P2, scotopic threshold response (STR), and oscillatory potentials (OP). The retinal injury and anti-ischemic effects of BMSCs were quantitated by measuring apoptosis, autophagy, inflammatory markers, and retinal-blood barrier permeability. The distribution and fate of BMSC were qualitatively examined using real-time fundus imaging, and retinal flat mounts.

RESULTS

Intravitreal delivery of BMSCs significantly improved recovery of the ERG a- and b-waves, OP, negative STR, and P2, and attenuated apoptosis as evidenced by decreased TUNEL and caspase-3 protein levels. BMSCs significantly increased autophagy, decreased inflammatory mediators (TNF-α, IL-1β, IL-6), and diminished retinal vascular permeability. BMSCs persisted in the vitreous and were also found within ischemic retina.

CONCLUSIONS

Taken together, our results indicate that intravitreal injection of BMSCs rescued the retina from ischemic damage in a rat model. The mechanisms include suppression of apoptosis, attenuation of inflammation and vascular permeability, and preservation of autophagy.