Death of Axotomized Retinal Ganglion Cells Delayed after Intraoptic Nerve Transplantation of Olfactory Ensheathing Cells in Adult Rats

Cell replacement with stem cell-derived retinal ganglion cells from different protocols

Glaucoma, characterized by a degenerative loss of retinal ganglion cells, is the second leading cause of blindness worldwide. There is currently no cure for vision loss in glaucoma because retinal ganglion cells do not regenerate and are not replaced after injury. Human stem cell-derived retinal ganglion cell transplant is a potential therapeutic strategy for retinal ganglion cell degenerative diseases. In this review, we first discuss a 2D protocol for retinal ganglion cell differentiation from human stem cell culture, including a rapid protocol that can generate retinal ganglion cells in less than two weeks and focus on their transplantation outcomes. Next, we discuss using 3D retinal organoids for retinal ganglion cell transplantation, comparing cell suspensions and clusters. This review provides insight into current knowledge on human stem cell-derived retinal ganglion cell differentiation and transplantation, with an impact on the field of regenerative medicine and especially retinal ganglion cell degenerative diseases such as glaucoma and other optic neuropathies.

Therapeutic strategies for glaucoma and optic neuropathies

Glaucoma is a neurodegenerative eye disease that causes permanent vision impairment. The main pathological characteristics of glaucoma are retinal ganglion cell (RGC) loss and optic nerve degeneration. Glaucoma can be caused by elevated intraocular pressure (IOP), although some cases are congenital or occur in patients with normal IOP. Current glaucoma treatments rely on medicine and surgery to lower IOP, which only delays disease progression. First-line glaucoma medicines are supported by pharmacotherapy advancements such as Rho kinase inhibitors and innovative drug delivery systems. Glaucoma surgery has shifted to safer minimally invasive (or microinvasive) glaucoma surgery, but further trials are needed to validate long-term efficacy. Further, growing evidence shows that adeno-associated virus gene transduction and stem cell-based RGC replacement therapy hold potential to treat optic nerve fiber degeneration and glaucoma. However, better understanding of the regulatory mechanisms of RGC development is needed to provide insight into RGC differentiation from stem cells and help choose target genes for viral therapy. In this review, we overview current progress in RGC development research, optic nerve fiber regeneration, and human stem cell-derived RGC differentiation and transplantation. We also provide an outlook on perspectives and challenges in the field.

Update of application of olfactory ensheathing cells and stem cells/exosomes in the treatment of retinal disorders

Age-related macular degeneration, diabetic retinopathy, retinitis pigmentosa and other retinal disorders are the main causes of visual impairment worldwide. In the past, these retinal diseases, especially dry age-related macular degeneration, proliferative diabetic retinopathy and retinitis pigmentosa, were treated with traditional surgery and drugs. However, the effect was moderate. In recent years, researchers have used embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells, olfactory ensheathing cells and other stem cells to conduct experiments and found that stem cells can inhibit inflammation, regulate immune response, secrete neurotrophic factors, and differentiate into retinal cells to replace and promote restoration of the damaged parts. These stem cells have the potential to treat retinal diseases. Whether it is in animal experiments or clinical trials, the increase in the number of retinal cells, maintenance of function and improvement of visual function all reflect the advanced of stem cells to treat retinal diseases, but its risk preserves the donor's hidden pathogenic genes, immune rejection and tumorigenicity. With the development of exosomes study, researchers have discovered that exosomes come from a wide range of sources and can be secreted by almost all types of cells. Using exosomes with stem cell to treat retinal diseases is more effective than using stem cells alone. This review article summarizes the recent advances in the application of olfactory ensheathing cells and stem cells/exosomes in the treatment of retinal disorders.

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.

Intravitreal Co-Administration of GDNF and CNTF Confers Synergistic and Long-Lasting Protection against Injury-Induced Cell Death of Retinal Ganglion Cells in Mice

We have recently demonstrated that neural stem cell-based intravitreal co-administration of glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF) confers profound protection to injured retinal ganglion cells (RGCs) in a mouse optic nerve crush model, resulting in the survival of ~38% RGCs two months after the nerve lesion. Here, we analyzed whether this neuroprotective effect is long-lasting and studied the impact of the pronounced RGC rescue on axonal regeneration. To this aim, we co-injected a GDNF- and a CNTF-overexpressing neural stem cell line into the vitreous cavity of adult mice one day after an optic nerve crush and determined the number of surviving RGCs 4, 6 and 8 months after the lesion. Remarkably, we found no significant decrease in the number of surviving RGCs between the successive analysis time points, indicating that the combined administration of GDNF and CNTF conferred lifelong protection to injured RGCs. While the simultaneous administration of GDNF and CNTF stimulated pronounced intraretinal axon growth when compared to retinas treated with either factor alone, numbers of regenerating axons in the distal optic nerve stumps were similar in animals co-treated with both factors and animals treated with CNTF only.

Synergistic protection of RGCs by olfactory ensheathing cells and alpha-crystallin through regulation of the Akt/BAD Pathway

BACKGROUND

Our recent in vivo studies have shown that olfactory ensheathing cells (OECs) and α-crystallin can promote retinal ganglion cell (RGC) survival and axonal regeneration synergistically after optic nerve injury. However, the mechanism is still unknown.

OBJECTIVES

Here, we studied the synergistic effect and mechanism of OECs and α-crystallin on RGC survival after H₂O₂-induced oxidative damage and a crushing injury to the optic nerve in an adult rat model.

METHODS

After H₂O₂-induced oxidative damage, RGC-5 cells were treated with OECs, α-crystallin or a combination of OECs and α-crystallin. Apoptosis of RGC-5 cells was assessed by flow cytometry. Phosphorylated Akt, BAD, and cleaved-caspase3 were detected by Western blot after optic nerve injury in vivo and H₂O₂-induced RGC-5 oxidative damage in vitro.

RESULTS

The results showed that OECs and α-crystallin could both independently inhibit RGC-5 apoptosis (P<0.01), increase the phosphorylation of both Akt and BAD, and decrease the activation of caspase-3 (P<0.01). However, the effect of the combination of both was more significant than either alone.

CONCLUSION

These findings indicate that inhibition of superoxide damage to RGCs through regulation of the Akt/BAD pathway is one of the mechanisms by which OECs and α-crystallin promote optic nerve recovery after injury.

Models and treatments for traumatic optic neuropathy and demyelinating optic neuritis

Pathologies of the optic nerve could result as primary insults in the visual tract or as secondary deficits due to inflammation, demyelination, or compressing effects of the surrounding tissue. The extent of damage may vary from mild to severe, differently affecting patient vision, with the most severe forms leading to complete uni- or bilateral visual loss. The aim of researchers and clinicians in the field is to alleviate the symptoms of these, yet uncurable pathologies, taking advantage of known and novel potential therapeutic approaches, alone or in combinations, and applying them in a limited time window after the insult. In this review, we discuss the epidemiological and clinical profile as well as the pathophysiological mechanisms of two main categories of optic nerve pathologies, namely traumatic optic neuropathy and optic neuritis, focusing on the demyelinating form of the latter. Moreover, we report on the main rodent models mimicking these pathologies or some of their clinical aspects. The current treatment options will also be reviewed and novel approaches will be discussed.

Branched-Chain Amino Acids Enhance Retinal Ganglion Cell Survival and Axon Regeneration after Optic Nerve Transection in Rats

PURPOSE

This study's aim was to investigate the beneficial effects of branched-chain amino acids (BCAAs) on the neuronal survival and axon regeneration of retinal ganglion cells (RGCs) after optic nerve (ON) transection.

METHOD

The experimental rats received daily BCAA injections through the caudal vein after left intra-orbital ON transection. Neuroprotection was evaluated by counting Fluorogold-labeled RGCs. The role of mammalian target of rapamycin (mTOR) pathway activation in promoting RGC survival was studied after rapamycin administration. Moreover, a peripheral nerve (PN) graft was transplanted onto the transected ON to study the effects of BCAAs on axon regeneration of injured RGCs.

RESULTS

Our results showed that BCAAs alleviated the death of RGCs 7 and 14 days after ON transection, accompanied by an activation of mTOR pathway in RGCs. Blocking mTOR pathway with rapamycin eliminated such neuroprotective effects of BCAAs. Moreover, BCAAs also promoted axon regeneration of injured RGCs into a PN graft.

CONCLUSION

Our results suggest a neuroprotection of BCAAs through the activation of mTOR pathway. BCAAs also have a beneficial effect on axon regeneration of injured RGCs. Therefore, BCAAs could be considered for the clinical treatment of ON injury.

The Therapeutic Effects after Transplantation of Whole-Layer Olfactory Mucosa in Rats with Optic Nerve Injury

Background

Existing evidence suggests the potential therapy of transplanting olfactory ensheathing cells (OEC) either alone or in combination with neurotrophic factors or other cell types in optic nerve injury (ONI). However, clinical use of autologous OEC in the acute stages of ONI is not possible. On the other hand, acute application of heterologous transplantation may bring the issue of immune rejection. The olfactory mucosa (OM) with OEC in the lamina propria layer is located in the upper region of the nasal cavity and is easy to dissect under nasal endoscopy, which makes it a candidate as autograft material in acute stages of ONI. To investigate the potential of the OM on the protection of injured neurons and on the promotion of axonal regeneration, we developed a transplantation of syngenic OM in rats with ONI model.

Methods

After the right optic nerve was crushed in Lewis rats, pieces of syngenic whole-layer OM were transplanted into the lesion. Rats undergoing phosphate buffered saline (PBS) injection were used as negative controls (NC). The authors evaluated the regeneration of retinal ganglion cells (RGCs) and axons for 3, 7, 14, and 28 days after transplantation. Obtained retinas and optic nerves were analyzed histologically.

Results

Transplantations of OM significantly promoted the survival of retinal ganglion cells (RGCs) and axonal growth of RGCs compared with PBS alone. Moreover, OM group was associated with higher expression of GAP-43 in comparison with the PBS group. In addition to the potential effects on RGCs, transplantations of OM significantly decreased the expression of GFAP in the retinas, suggesting inhibiting astrocyte activation.

Conclusions

Transplantation of whole-layer OM in rats contributes to the neuronal survival and axon regeneration after ONI.

Harnessing Nanotopography of Electrospun Nanofibrous Nerve Guide Conduits (NGCs) for Neural Tissue Engineering

The anatomical recovery of nerve defects with their neurological functions after an injury caused by diseases or accidents is an important clinical issue. The most efficient surgical technique so far to the nerve defects, which are unrepairable by direct end-to-end suture, can be autograft transplantation. The autograft transplantation, however, has disadvantages including multiple rounds of surgery, a shortage of nerve donor, and function loss at the donor site. Tissue-engineered nerve guide conduits (TENGCs) have emerged as a potential alternative to autologous nerve grafts for nerve regeneration and functional recovery. Various TENGCs researches are being carried out to improve characteristics and enhance functionality such as material selection, biomimetic, topography, and enhancement by the biomolecules additions. Among them, the customizable surface nanotopography of aligned fibrous TENGCs foster neural repair by providing a cell-friendly environment, permissiveness, guidance cues, and directional growth of the cells. Fibrous nerve guide conduits (NGCs) made of longitudinally ordered fibers is a promising candidate for nerve tissue engineering.

The Glia Response after Peripheral Nerve Injury: A Comparison between Schwann Cells and Olfactory Ensheathing Cells and Their Uses for Neural Regenerative Therapies

The peripheral nervous system (PNS) exhibits a much larger capacity for regeneration than the central nervous system (CNS). One reason for this difference is the difference in glial cell types between the two systems. PNS glia respond rapidly to nerve injury by clearing debris from the injury site, supplying essential growth factors and providing structural support; all of which enhances neuronal regeneration. Thus, transplantation of glial cells from the PNS is a very promising therapy for injuries to both the PNS and the CNS. There are two key types of PNS glia: olfactory ensheathing cells (OECs), which populate the olfactory nerve, and Schwann cells (SCs), which are present in the rest of the PNS. These two glial types share many similar morphological and functional characteristics but also exhibit key differences. The olfactory nerve is constantly turning over throughout life, which means OECs are continuously stimulating neural regeneration, whilst SCs only promote regeneration after direct injury to the PNS. This review presents a comparison between these two PNS systems in respect to normal physiology, developmental anatomy, glial functions and their responses to injury. A thorough understanding of the mechanisms and differences between the two systems is crucial for the development of future therapies using transplantation of peripheral glia to treat neural injuries and/or disease.

Synergistic effect of olfactory ensheathing cells and alpha-crystallin on restoration of adult rat optic nerve injury

Olfactory enshesathing cells (OECs) and α-crystallin all can promote axonal regeneration after optic nerve injury. However, their mechanisms were different. Here, we study the synergistic effect of OECs and α-crystallin on the optic nerve regeneration. α-Crystallin was injected into vitreous cavity, and OECs were transplanted to the optic nerve injury area. The regeneration length of optic nerve were measured by anterograde tracing using cholera toxin subunit B (CTB). The survival of RGCs were assessed by counting the numbers of βIII-tubulin-labeled RGCs in a retinal whole mount. The results that OECs and α-crystallin all could promoted RGCs survival and axonal regeneration (P<0.01). Especially in the combination group, the length of axonal regeneration was 5.6mm after optic nerve injury for 3 months. These findings indicated that compared to OECs and α-crystallin alone, the combination of OECs and α-crystallin could promote axonal regeneration more effectively.

Human umbilical cord blood stem cells and brain-derived neurotrophic factor for optic nerve injury: a biomechanical evaluation

Treatment for optic nerve injury by brain-derived neurotrophic factor or the transplantation of human umbilical cord blood stem cells has gained progress, but analysis by biomechanical indicators is rare. Rabbit models of optic nerve injury were established by a clamp. At 7 days after injury, the vitreous body received a one-time injection of 50 μg brain-derived neurotrophic factor or 1 × 10(6) human umbilical cord blood stem cells. After 30 days, the maximum load, maximum stress, maximum strain, elastic limit load, elastic limit stress, and elastic limit strain had clearly improved in rabbit models of optical nerve injury after treatment with brain-derived neurotrophic factor or human umbilical cord blood stem cells. The damage to the ultrastructure of the optic nerve had also been reduced. These findings suggest that human umbilical cord blood stem cells and brain-derived neurotrophic factor effectively repair the injured optical nerve, improve biomechanical properties, and contribute to the recovery after injury.

Exciting directions in glaucoma

Glaucoma is a complex, life-long disease that requires an individualized, multifaceted approach to treatment. Most patients will be started on topical ocular hypotensive eyedrop therapy, and over time multiple classes of drugs will be needed to control their intraocular pressure. The search for drugs with novel mechanisms of action, to treat those who do not achieve adequate intraocular pressure control with, or become refractory to, current therapeutics, is ongoing, as is the search for more efficient, targeted drug delivery methods. Gene-transfer and stem-cell applications for glaucoma therapeutics are moving forward. Advances in imaging technologies improve our understanding of glaucoma pathophysiology and enable more refined patient evaluation and monitoring, improving patient outcomes.

A prospective randomized double-blind clinical trial using a combination of olfactory ensheathing cells and Schwann cells for the treatment of chronic complete spinal cord injuries

The aim of this prospective randomized double-blind clinical study is to examine the benefits of using olfactory ensheathing cells (OECs) combined with or without Schwann cells (SCs) in treating chronic complete spinal cord injuries (SCIs). This would offer patients a better alternative for neurological functional recovery. According to the initial design, 28 eligible participants with cervical chronic complete SCI were recruited and randomly allocated into four groups of seven participants each. The neurological assessments were to be performed according to the American Spinal Injury Association (ASIA) and International Association of Neurorestoratology (IANR) Functional Rating Scales, in combination with electrophysiological tests, for example, electromyography (EMG) and paraspinal somatosensory evoked potentials (PSSEPs). Here we have summarized the data from seven patients; three patients received an OEC intraspinal transplantation, one underwent SC implantation, and one received a combination of OECs and SCs. The remaining two patients were used as controls. The scores were evaluated independently by at least two neurologists in a blinded fashion for comparing the neurological functional changes during pre- and post-cell transplantation (6-month follow-up). All patients who received OECs, SCs alone, and a combination of them showed functional improvement. Mild fever occurred in one of the patients with OEC transplant that subsided after symptomatic treatments. All treated patients except one showed improvement in the electrophysiological tests. The functional improvement rate comprises 5/5 (100%) in the treated group, but 0/2 (0%) in the control group (p = 0.008). These preliminary findings show that transplanting OECs, SCs, or a combination of them is well tolerated and that they have beneficial effects in patients. Thus, further studies in larger patient cohorts are warranted to assess the benefits and risks of these intervention strategies. This manuscript is published as part of the IANR special issue of Cell Transplantation.

Sustained effect of bone marrow mononuclear cell therapy in axonal regeneration in a model of optic nerve crush

In adult mammals, the regeneration of the optic nerve is very limited and at the moment there are several groups trying different approaches to increase retinal ganglion cell (RGC) survival and axonal outgrowth. One promising approach is cell therapy. In previous work, we performed intravitreal transplantation of bone-marrow mononuclear cells (BMMCs) after optic nerve crush in adult rats and we demonstrated an increase in RGC survival and axon outgrowth 14 days after injury. In the present work, we investigated if these results could be sustained for a longer period of time. Optic nerve crush was performed in Lister-hooded adult rats and BMMC or saline injections were performed shortly after injury. Neuronal survival and regeneration were evaluated in rats׳ retina and optic nerve after 28 days. We demonstrated an increase of 5.2 fold in the axon outgrowth 28 days after lesion, but the BMMCs had no effect on RGC survival. In an attempt to prolong RGC survival, we established a new protocol with two BMMC injections, the second one 7 days after the injury. Untreated animals received two injections of saline. We observed that although the axonal outgrowth was still increased after the second BMMC injection, the RGC survival was not significantly different from untreated animals. These results demonstrate that BMMCs transplantation promotes neuroregeneration at least until 28 days after injury. However, the effects on RGC survival previously observed by us at 14 days were not sustained at 28 days and could not be prolonged with a second dose of BMMC.

Dose-dependent protective effect of lithium chloride on retinal ganglion cells is interrelated with an upregulated intraretinal BDNF after optic nerve transection in adult rats

Neuroprotection of lithium for axotomized retinal ganglion cells (RGCs) is attributed to upregulated intraretinal Bcl-2. As lithium also upregulates brain-derived neurotrophic factor (BDNF) which can rescue axotomized RGCs, it is hypothesized that lithium could protect RGCs through BDNF. This study investigated this hypothesis and a possible relationship between the dose and protection of lithium. All adult experimental rats received daily intraperitoneal injections of lithium chloride (LiCl) at 30, 60 or 85 mg/kg·bw until they were euthanized 2, 7 or 14 days after left intraorbital optic nerve (ON) transection. Our results revealed that RGC densities promoted and declined with increased dose of LiCl and the highest RGC densities were always in the 60 mg/kg·bw LiCl group at both 7 and 14 day points. Similar promotion and decline in the mRNA and protein levels of intraretinal BDNF were also found at the 14 day point, while such BDNF levels increased in the 30 mg/kg·bw LiCl group but peaked in the 60 and 85 mg/kg·bw LiCl groups at the 7 day point. These findings suggested that lithium can delay the death of axotomized RGCs in a dose-dependent manner within a certain period after ON injury and such beneficial effect is interrelated with an upregulated level of intraretinal BDNF.

Stem cell therapy for glaucoma: science or snake oil?

In recent years there has been substantial progress in developing stem cell treatments for glaucoma. As a downstream approach that targets the underlying susceptibility of retinal ganglion and trabecular meshwork cells, stem cell therapy has the potential to both replace lost, and protect damaged, cells by secreting neurotrophic factors. A variety of sources, including embryonic cells, adult cells derived from the central nervous system, and induced pluripotent stem cells show promise as therapeutic approaches. Even though safety concerns and ethical controversies have limited clinical implementation, some institutions have already commercialized stem cell therapy and are using direct-to-consumer advertising to attract patients with glaucoma. We review the progress of stem cell therapy and its current commercial availability.

Using manganese-enhanced MRI to assess optic nerve regeneration

Experimental visual pathway lesion in the form of optic nerve (ON) crush or transection injury results in massive death of retinal ganglion cells (RGCs) and permanent loss of synaptic connections (Berkelaar et al., J Neurosci 14:4368-4374, 1994). Despite the fact that RGC axon regeneration is inhibited in a manner typical of other CNS lesions, the rodent ON injury model is one of the few models where robust axon regeneration has been achieved after therapeutic intervention (Berry et al., Restor Neurol Neurosci 26:147-174, 2008). However, assessment of the efficacy of therapeutic approaches in promoting ON regeneration has traditionally relied on histological methods, which necessitate the sacrifice of experimental animals and thus preclude longitudinal in vivo monitoring of individual subjects. Manganese-enhanced MRI (MEMRI) utilizes the paramagnetic properties and uptake and transport mechanisms of manganese ions (Mn(2+)) by neurons, thus enabling serial in vivo monitoring of the entire axonal projections (Sandvig et al., J Magn Reson Imaging 34:670-675, 2011; Thuen et al., J Magn Reson Imaging 4:492-500, 2005; Pautler et al., Magn Res Med 50:33-39, 2003; Saleem et al., Neurotechnique 34:685-700, 2000). The above properties of Mn(2+) render MEMRI a highly suitable technique for assessment of ON regeneration after injury, especially with a view to in vivo monitoring of neuronal connectivity and axon-regenerative responses to treatment. In this chapter, we provide a generic protocol for ON lesioning and MEMRI application for assessment of ON regeneration in rodents.

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.

Survival and integration of developing and progenitor-derived retinal ganglion cells following transplantation

There is considerable interest in transplanting stem cells or progenitors into the injured nervous system and enhancing their differentiation into mature, integrated, functional neurons. Little is known, however, about what intrinsic or extrinsic signals control the integration of differentiated neurons, either during development or in the adult. Here we ask whether purified, postmitotic, differentiated retinal ganglion cells (RGCs) directly isolated from rat retina or derived from in vitro-differentiated retinal progenitor cells can survive, migrate, extend neurites, and form morphologic synapses in a host retina, in vivo and ex vivo. We found that acutely purified primary and in vitro-differentiated RGCs survive transplantation and migrate into deeper retinal layers, including into their normal environment, the ganglion cell layer (GCL). Transplanted RGCs from a wide range of developmental ages, but not from adults, were capable of extending lengthy neurites in the normal and injured adult rat retina ex vivo and to a lesser degree after transplantation in vivo. We have also demonstrated that RGCs may be differentiated and purified from retinal precursor cultures and that they share many of the same cell biological properties as primary RGCs. We have established that progenitor-derived RGCs have similar capacity for integration as developing primary RGCs but appear to form a lower number of presynaptic punctae. This work provides insight for further understanding of the integration of developing RGCs into their normal environment and following injury.

Long-term outcome of olfactory ensheathing cell therapy for patients with complete chronic spinal cord injury

The neurorestorative effect of the parenchymal transplantation of olfactory ensheathing cells (OECs) for cord trauma remains clinically controversial. The aim of this article is to study the long-term result of OECs for patients with complete chronic spinal cord injury (SCI). One hundred and eight patients suffered from complete chronic SCI were followed up successfully within the period of 3.47 ± 1.12 years after OEC therapy. They were divided into two groups based on the quality and quantity of their rehabilitative training: group A (n = 79) in sufficient rehabilitation (or active movement-target enhancement-neurorehabilitation therapy, AMTENT) and group B (n = 29) in insufficient rehabilitation. All patients were assessed by using the American Spinal Injury Association (ASIA) standard and the International Association of Neurorestoratology Spinal Cord Injury Functional Rating Scale (IANR-SCIFRS). Thirty-one patients were evaluated by the tests of magnetic resonance imaging (MRI), electromyography (EMG), and paravertebral sensory evoked potential (PVSEP). We found the following. 1) According to ASIA and IANR-SCIFRS assessment for all 108 patients, averaged motor scores increased from 37.79 ± 18.45 to 41.25 ± 18.18 (p < 0.01), light touch scores from 50.32 ± 24.71 to 55.90 ± 24.46 (p < 0.01), pin prick scores from 50.53 ± 24.92 to 54.53 ± 24.62 (p < 0.01); IANR-SCIFRS scores increased from 19.32 ± 9.98 to 23.12 ± 10.30 (p < 0.01). 2) The score changes in terms of motor, light touch, pin prick, and IANR-SCIFRS in group A were remarkably different (all p < 0.01). The score changes in group B were remarkably different in terms of motor (p < 0.05) and IANR-SCIFRS (p < 0.01), but not light touch or pin prick (p > 0.05). 3) Comparing group A with group B, the increased scores in terms of motor, light touch, and pin prick were remarkably different (all p < 0.01), but not IANR-SCIFRS (p > 0.05). 4) Fourteen of 108 patients (12.96%) became ASIA B from ASIA A; 18 of 108 (16.67%) became ASIA C from ASIA A. Nine of them (8.33%) improved their walk ability or made them rewalk by using a walker with or without assistance; 12 of 84 men (14.29%) improved their sex function. 5) MRI examinations were taken for 31 patients; there were no neoplasm, bleeding, swelling, cysts, neural tissue destruction or infection (abscess) or any other pathological changes in or around OEC transplant sites. 6) EMG examinations were done on 31 patients; 29 showed improvement and the remaining 2 had no change. PVSEP tests were performed in 31 patients; 28 showed improvements and the remaining 3 had no change. 7) No deterioration or complications were observed in our patients within the follow-up period. Our data suggest OEC therapy is safe and can improve neurological functions for patients with complete chronic SCI and ameliorate their quality of life; the AMTENT most likely plays a critical role in enhancing functional recovery after cell-based neurorestorotherapy.

Olfactory ensheathing cell neurorestorotherapy for amyotrophic lateral sclerosis patients: benefits from multiple transplantations

Our previous series of studies have proven that olfactory ensheathing cell (OEC) transplantation appears to be able to slow the rate of clinical progression after OEC transplantation in the first 4 months and cell intracranial (key points for neural network restoration, KPNNR) and/or intraspinal (impaired segments) implants provide benefit for patients (including both the bulbar onset and limb onset subtypes) with amyotrophic lateral sclerosis (ALS). Here we report the results of cell therapy in patients with ALS on the basis of long-term observation following multiple transplants. From March of 2003 to January of 2010, 507 ALS patients received our cellular treatment. Among them, 42 patients underwent further OEC therapy by the route of KPNNR for two or more times (two times in 35 patients, three times in 5 patients, four times in 1 patient, and five times in 1 patient). The time intervals are 13.1 (6-60) months between the first therapy and the second one, 15.2 (8-24) months between the second therapy and the third one, 16 (6-26) months between the third therapy and the fourth one, and 9 months between the fourth therapy and the fifth time. All of the patients exhibited partial neurological functional recovery after each cell-based administration. Firstly, the scores of the ALS Functional Rating Scale (ALS-FRS) and ALS Norris Scale increased by 2.6 + 2.4 (0-8) and 4.9 + 5.2 (0-20) after the first treatment, 1.1 + 1.3 (0-5) and 2.3 + 2.9 (0-13) after the second treatment, 1.1 + 1.5 (0-4), and 3.4 + 6.9 (0-19) after the third treatment, 0.0 + 0.0 (0-0), and 2.5 + 3.5 (0-5) after the fourth treatment, and 1 point after the fifth cellular therapy, which were evaluated by independent neurologists. Secondly, the majority of patients have achieved improvement in electromyogram (EMG) assessments after the first, second, third, and fourth cell transplantation. After the first treatment, among the 42 patients, 36 (85.7%) patients' EMG test results improved, the remaining 6 (14.3%) patients' EMG results showed no remarkable change. After the second treatment, of the 42 patients, 30 (71.4%) patients' EMG results improved, 11 (26.2%) patients showed no remarkable change, and 1 (2.4%) patient became worse. After the third treatment, out of the 7 patients, 4 (57.1%) patients improved, while the remaining 3 (42.9%) patients showed no change. Thirdly, the patients have partially recovered their breathing ability as demonstrated by pulmonary functional tests. After the first treatment, 20 (47.6%) patients' pulmonary function ameliorated. After the second treatment, 18 (42.9%) patients' pulmonary function improved. After the third treatment, 2 (28.6%) patients recovered some pulmonary function. After the fourth and fifth treatment, patients' pulmonary function did not reveal significant change. The results show that multiple doses of cellular therapy definitely serve as a positive role in the treatment of ALS. This repeated and periodic cell-based therapy is strongly recommended for the patients, for better controlling this progressive deterioration disorder.

Effects of neural progenitor cell transplantation in children with severe cerebral palsy

Cerebral palsy (CP) is a chronic nervous system disease that severely damages the physical and developmental health of children. Traditional treatment brings about only improvement of mild to moderate CP, but severe CP still lacks effective interventions. To explore safety and efficacy of using neural progenitor cells (NPCs) to treat CP in children, we performed NPC transplantation in 45 patients with severe CP by injecting NPCs derived from aborted fetal tissue into the lateral ventricle. Gross motor function measures (GMFM), the Peabody Developmental Motor Scale-Fine Motor (PDMS-FM) test, and a unified survey questionnaire designed specifically for children with CP were used to evaluate neurological function of the patients. Motor development was significantly accelerated within the first month after cell transplantation, but the rate of improvement gradually slowed to preoperative levels. However, after 1 year, the developmental level in each functional sphere (gross motor, fine motor, and cognition) of the treatment group was significantly higher compared to the control group. No delayed complications of this therapy were noted. These results suggest that NPC transplantation is a safe and effective therapeutic method for treating children with severe CP.

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.

Transplanted olfactory ensheathing cells reduce retinal degeneration in Royal College of Surgeons rats

PURPOSE OF THE STUDY

Retinitis pigmentosa (RP) is a group of genetic disorders and a slow loss of vision that is caused by a cascade of retinal degenerative events. We examined whether these retinal degenerative events were reduced after cultured mixtures of adult olfactory ensheathing cells (OECs) and olfactory nerve fibroblasts (ONFs) were transplanted into the subretinal space of 1-month-old RCS rat, a classic model of RP.

MATERIALS AND METHODS

The changes in retinal photoreceptors and Müller cells of RCS rats after cell transplantation were observed by the expression of recoverin and glial fibrillary acidic protein (GFAP), counting peanut agglutinin (PNA)-positive cone outer segments and calculating the relative apoptotic area. The retinal function was also evaluated by Flash electroretinography (ERG). To further investigate the mechanisms, by which OECs/ONFs play important roles in the transplanted retinas, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and basic fibroblast growth factor (bFGF) secretion of the cultured cells were analyzed by ELISA. The ability of OECs/ONFs to ingest porcine retinal outer segments and the amount of phagocytosis were compared with retinal pigment epithelium (RPE) cells.

RESULTS

Our research showed that the transplantation of OECs/ONFs mixtures restored recoverin expression, protected retinal outer segments, increased PNA-positive cone outer segments, reduced caspase-positive apoptotic figures, downregulated GFAP, and maintained the b-wave of the ERG. Cultured OECs/ONFs expressed and secreted NGF, BDNF, and bFGF which made contributions to assist survival of the photoreceptors. An in vitro phagocytosis assay showed that OECs, but not ONFs, phagocytosed porcine retinal outer segments, and the phagocytic ability of OECs was even superior to that of RPE cells.

CONCLUSIONS

These findings demonstrate that transplantation of OECs/ONFs cleaned up the accumulated debris in subretinal space, and provided an intrinsic continuous supply of neurotrophic factors. It suggested that transplantation of OECs/ONFs might be a possible future route for protection of the retina and reducing retinal degeneration in RP.

Dose-dependent and combined effects of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine on the survival of retinal ganglion cells in adult hamsters

This study investigated the effects of daily intraperitoneal injections of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine (L-NA) on the survival of retinal ganglion cells (RGCs) at 1 and 2 weeks after unilateral optic nerve transection in adult hamsters. The left optic nerves of all animals were transected intraorbitally 1 mm from the optic disc and RGCs were retrogradely labeled with Fluorogold before they received different daily dosages of single MK-801 or L-NA as well as daily combinational treatments of these two chemicals. All experimental and control animals survived for 1 or 2 weeks after optic nerve transection. Our results revealed that the mean numbers of surviving RGCs increased and then decreased when the dosage of MK-801 (1.0, 3.0 and 4.5 mg/kg) and L-NA (1.5, 3.0, 4.5 and 6.0 mg/kg) increased at both 1 and 2 weeks survival time points. Daily combinational use of 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA lead to a highest RGC number that was even higher than the sum of the RGC numbers in 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA subgroups at 2 weeks. These findings indicated that both MK-801 and L-NA can protect axotomized RGCs in a dose-dependent manner and combinational treatment of these chemicals possesses a potentiative and protective effect.

In vivo MRI of olfactory ensheathing cell grafts and regenerating axons in transplant mediated repair of the adult rat optic nerve

The purpose of the present study was to use magnetic resonance imaging (MRI) as a tool for monitoring transplant-mediated repair of the adult rat visual pathway. We labelled rat olfactory ensheathing cells (OECs) using micron-sized particles of iron oxide (MPIO) and transplanted them by: i) intravitreal injection (ivit) and ii) intra-optic nerve (ON) injection (iON) in adult rats with ON crush (ONC) injury. We applied T(2)-weighted MRI and manganese-enhanced MRI (MEMRI) to visualise transplanted cells and ON axons at specific times after injury and cell engraftment. Our findings demonstrate that ivit MPIO-labelled OECs are unequivocally detected by T(2)-weighted MRI in vivo and that the T(1)-weighted 3D FLASH sequence applied for MEMRI facilitates simultaneous visualisation of Mn(2+-) enhanced regenerating retinal ganglion cell (RGC) axons and MPIO-labelled OEC grafts. Furthermore, analysis of MRI data and ultrastructural findings supports the hypothesis that iON OEC transplants mediate regeneration and remyelination of RGC axons post injury.

Heterogeneous spine loss in layer 5 cortical neurons after spinal cord injury

A large thoracic spinal cord injury disconnects the hindlimb (HL) sensory-motor cortex from its target, the lumbar spinal cord. The fate of the synaptic structures of the axotomized cortical neurons is not well studied. We evaluated the density of spines on axotomized corticospinal neurons at 3, 7, and 21 days after the injury in adult mice expressing yellow fluorescence protein in a subset of layer 5 neurons. Spine density of the dendritic segment proximal to the soma (in layer 5) declined as early as 3 days after injury, far preceding the onset of somatic atrophy. In the distal segment (in layer 2/3), spine loss was slower and less severe than in the proximal segment. Axotomy of corticospinal axons in the brainstem (pyramidotomy) induced a comparable reduction of spine density, demonstrating that the loss is not restricted to the neurons axotomized in the thoracic spinal cord. Surprisingly, in both forms of injury, the spine density of putative non-axotomized layer 5 neurons was reduced as well. The spine loss may reflect fast rearrangements of cortical circuits after axotomy, for example, by a disconnection of HL cortical neurons from synaptic inputs that no longer provide useful information.

Transplanted olfactory ensheathing cells reduce the gliotic injury response of Müller cells in a rat model of retinitis pigmentosa

Retinitis pigmentosa leads to progressive visual loss and blindness. Until now there has been no effective therapy. Experimental studies have shown that transplantation of olfactory ensheathing cells into CNS lesions reorganizes the glial scar and stimulates axon regeneration. We now report that cultured syngeneic adult rat olfactory ensheathing cells transplanted into the subretinal space of pigmented Royal College of Surgeon rats survived for a minimum of 8weeks, migrated into surrounding space, and suppressed the gliotic injury response of the Müller cells. Further investigation of intraretinal transplantation of olfactory ensheathing cells may suggest a possible future route for protection of the retina in retinitis pigmentosa.

Current approaches and future prospects for stem cell rescue and regeneration of the retina and optic nerve

The 3 most common causes of visual impairment and legal blindness in developed countries (age-related macular degeneration, glaucoma, and diabetic retinopathy) share 1 end point: the loss of neural cells of the eye. Although recent treatment advances can slow down the progression of these conditions, many individuals still suffer irreversible loss of vision. Research is aimed at developing new treatment strategies to rescue damaged photoreceptors and retinal ganglion cells (RGC) and to replace lost cells by transplant. The neuroprotective and regenerative potential of stem and progenitor cells from a variety of sources has been explored in models of retinal disease and ganglion cell loss. Continuous intraocular delivery of neurotrophic factors via stem cells (SC) slows down photoreceptor cells and RGC loss in experimental models. Following intraocular transplantation, SC are capable of expressing proteins and of developing a morphology characteristic of photoreceptors or RGC. Recently, recovery of vision has been achieved for the first time in a rodent model of retinal dystrophy, using embryonic SC differentiated into photoreceptors prior to transplant. This indicates that clinically significant synapse formation and acquisition of the functional properties of retinal neurons, and restoration of vision, are distinct future possibilities.

Efficacy of olfactory ensheathing cells to support regeneration after spinal cord injury is influenced by method of culture preparation

Olfactory ensheathing cells (OEC) have been shown to stimulate regeneration, myelination and functional recovery in different spinal cord injury models. However, recent reports from several laboratories have challenged this treatment strategy. The discrepancy in results could be attributed to many factors including variations in culture protocols. The present study investigates whether the differences in culture preparation could influence neuroprotective and growth-promoting effects of OEC after transplantation into the injured spinal cord. Primary OEC cultures were purified using method of differential cell adhesion (a-OEC) or separated with immunomagnetic beads (b-OEC). After cervical C4 hemisection in adult rats, short-term (3 weeks) or long-term (7 weeks) cultured OEC were transplanted into the lateral funiculus at 1mm rostral and caudal to the transection site. At 3-8 weeks after transplantation, labeled OEC were mainly found in the injection sites and in the trauma zone. Short-term cultured a-OEC supported regrowth of rubrospinal, raphaespinal and CGRP-positive fibers, and attenuated retrograde degeneration in the red nucleus. Short-term cultured b-OEC failed to promote axonal regrowth but increased the density of rubrospinal axons within the dorsolateral funiculus and provided significant neuroprotection for axotomized rubrospinal neurons. In addition, short-term cultured OEC attenuated sprouting of rubrospinal terminals. In contrast, long-term cultured OEC neither enhanced axonal growth nor prevented retrograde cell death. The results suggest that the age of OEC in culture and the method of cell purification could affect the efficacy of OEC to support neuronal survival and regeneration after spinal cord injury. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

Bone marrow mononuclear cells increase retinal ganglion cell survival and axon regeneration in the adult rat

The central nervous system (CNS) of adult mammals generally does not regenerate, and many studies have attempted to identify factors that could increase neuroprotection and/or axonal outgrowth after CNS lesions. Using the optic nerve crush of rats as a model for CNS injury, we investigated the effect of intravitreal transplantation of syngeneic bone-marrow mononuclear cells (BMMCs) on the survival of retinal ganglion cells (RGC) and on the regeneration of optic axons. Control animals received intravitreal saline injections after lesion. Injections of BMMCs resulted in a 1.6-fold increase in the number of RGCs surviving 14 days after injury. The BMMC-treated animals also had increased numbers of axons, which grew up to 1.5 mm from the crush site, and also had reduced Müller glia activation. Analysis of mRNAs in all conditions revealed an increase in levels of fibroblast growth factor 2 (FGF-2) mRNA in treated animals 14 days after injury. To investigate whether the regenerated axons could reach the brain, we retrograde labeled the RGCs by injecting a lipophilic tracer into the superior colliculus. We also analyzed the expression of NGFI-A in the superficial layers of the superior colliculus as a possible marker of synaptic input from RGC axons. We found evidence that more RGCs were able to reach the brain after treatment and we showed that NGFI-A expression was higher in the treated animals 60 days after injury. These results demonstrate that transplant of BMMCs can increase neuroprotection and neuroregeneration after injury in a model of optic nerve crush, and these effects could be mediated by FGF-2.

Survival of retinal ganglion cells in slice culture provides a rapid screen for olfactory ensheathing cell preparations

Transplants of olfactory ensheathing cells (OECs) cultured from the olfactory bulb are able to induce structural regeneration of severed central axons and return of function in rat models. For clinical purposes it would be preferable to obtain the cells from the more accessible olfactory mucosa in the nasal lining. However, in our laboratory preparations cultures from mucosal samples yielded around 5% of OECs compared with the 50% obtained from samples cultured from the bulb, and when transplanted these mucosal cell preparations were less effective at repair. There are a number of manipulations which may increase the OEC content and the effectiveness of mucosal preparations, but in vivo transplantation would be a highly labour intensive method for evaluating them. As a candidate for a high throughput assay to screen for beneficial effects of modifications to mucosal cells we here report the effects of co-culture of the cells with retinal explants. Both bulbar and mucosal cell preparations prolong the survival of the explants. Counts of the surviving retinal ganglion cells, identified by beta-III-tubulin immunohistochemistry and by their axon trajectory, show that the bulbar cell preparations have around twice the potency of those from the mucosa. This in vitro system, therefore, provides a bioassay that discriminates bulbar and mucosal cell preparations, and a useful tool for evaluating the functional effects of manipulations of cultured mucosal preparations.

Synergistic effect of neural stem cells and olfactory ensheathing cells on repair of adult rat spinal cord injury

Spinal cord injury (SCI) is a common clinical disease that places a heavy burden on families and society. Cellular therapy provides a method of giving a supplement of cells lost in the injury and promoting functional recovery after SCI. Neural stem cells (NSCs) and olfactory ensheathing cells (OECs) are two most promising cell types. NSCs have the potential of differentiating into neurons and glial cells, and OECs could help the axons of neurons pass through the glial scar to promote functional recovery. NSCs were isolated from the cortices of fetal rats on days 12-14 of embryonic development and OECs were isolated from the olfactory bulbs of adult rats. In vitro coculture studies demonstrated OECs could promote NSCs to differentiate into neurons. Four groups of rats that had been 3/4 spinal cord transectioned at T9 were injected with DMEM/F12 solution, NSCs, OECs, and NSCs + OECs, respectively, 7 days post-SCI. Twelve weeks postoperation, the hindlimb locomotor function of rats in the cotransplantation group was significantly improved compared with that in the other three groups. Histological observation and immunohistochemical staining of NF-200 both showed new nerve fibers across the injured region. Cotransplantation of NSCs and OECs might have a synergistic effect on promoting neural regeneration and improving the recovery of locomotion function. Cotransplantation of NSCs and OECs was better than a single graft of either NSCs or OECs. These findings have provided a new way of thinking in the treatment of SCI.