Evidence of mutant huntingtin and tau-related pathology within neuronal grafts in Huntington's disease cases.

A number of post-mortem studies conducted in transplanted Huntington's disease (HD) patients from various trials have reported the presence of pathological and misfolded proteins, in particular mutant huntingtin (mHtt) and phosphorylated tau neuropil threads, in the healthy grafted tissue. Here, we extended these observations with histological analysis of post-mortem tissue from three additional HD patients who had received similar striatal allografts from the fetal tissue transplantation trial conducted in Los Angeles in 1998. Immunohistochemical staining was performed using anti-mHtt antibodies, EM48 and MW7, as well as anti-hyperphosphorylated tau antibodies, AT8 and CP13. Immunofluorescence was used to assess the colocalization of EM48+ mHtt aggregates with the neuronal marker MAP2 and/or the extracellular matrix protein phosphacan in both the host and grafts. We confirmed the presence of mHtt aggregates within grafts of all three cases as well as tau neuropil threads in the grafts of two of the three transplanted HD patients. Phosphorylated tau was also variably expressed in the host cerebral cortex of all three subjects. While mHtt inclusions were present within neurons (immunofluorescence co-localization of MAP2 and EM48) as well as within the extracellular matrix of the host (immunofluorescence co-localization of phosphacan and EM48), their localization was limited to the extracellular matrix in the grafted tissue. This study corroborates previous findings that both mHtt and tau pathology can be found in the host and grafts of HD patients years post-grafting.

[Clinical analysis of transcranial facial nerve bridging with interpositional graft for the treatment of facial nerve injury].

Objective:To retrospectively analyze the effectiveness of transcranial facial nerve bridging in the treatment of facial nerve dysfunction. Methods:A retrospective analysis was conducted on 27 patients with facial nerve dysfunction who underwent transcranial facial nerve bridging at the Eye, Ear, Nose, and Throat Hospital affiliated with Fudan University from 2017 to 2022. The main collected data includes the patient's age, gender, primary lesion, damaged location, interval from facial paralysis to surgery, and preoperative and postoperative House-Brackmann（HB） scale for facial nerve function. Statistical comparisons were made between the average HB level of patients before and after surgery. Results:A total of 27 patients included 17 males and 10 females. The average age of patients during surgery is（42.50±3.38） years old. Primary lateral skull base diseases include trauma（n=3）, tumors（n=22）, and infections（n=2）. The duration of facial paralysis varies from 6 months to 5 years. Statistics analysis has found that the average postoperative HB score of patients who underwent transcranial facial nerve bridging was significantly lower at（3.750 ± 0.183） compared to preoperative（4.875±0.168）. The proportion of patients with good facial nerve function increased significantly from 7.4% before surgery to 42.9% after surgery. Conclusion:Transcranial facial nerve bridging surgery with interpositional graft has a significant effect on improving facial nerve function in patients with facial nerve injury. Further research is still needed to evaluate the long-term effectiveness of this surgery, to determine the optimal patient selection criteria and postoperative rehabilitation strategies.

Evaluating the Feasibility of Hydrogel-Based Neural Cell Sprays.

Neurological injuries have poor prognoses with serious clinical sequelae. Stem cell transplantation enhances neural repair but is hampered by low graft survival (ca. 80%) and marker expression/proliferative potential of hydrogel-sprayed astrocytes was retained. Combining a cell spray format with polymer encapsulation technologies could form the basis of a non-invasive graft delivery method, offering potential advantages over current cell delivery approaches.

30 years of American Society for Neural Therapy and Repair (ASNTR): A personal perspective at the intersection of science, politics, and culture.

The American Society for Neural Therapy and Repair (ASNTR) started 30 years ago in 1993 as the American Society for Neural Transplantation (ASNT), with an emphasis on neural transplantation. Through the years, the Society has been shaped as much by our expanding knowledge of neurodegenerative disorders and how to treat them as it has by politics and culture. What once felt like a leash on neuroscience research, has turned into an advantage as neural transplantation evolved into Neural Therapy and Repair. As a Co-Founder this brief commentary provides a personalized account of our research during the Society's years.

Neurite Outgrowth and Gene Expression Profile Correlate with Efficacy of Human Induced Pluripotent Stem Cell-Derived Dopamine Neuron Grafts.

Transplantation of human induced pluripotent stem cell-derived dopaminergic (iPSC-DA) neurons is a promising therapeutic strategy for Parkinson's disease (PD). To assess optimal cell characteristics and reproducibility, we evaluated the efficacy of iPSC-DA neuron precursors from two individuals with sporadic PD by transplantation into a hemiparkinsonian rat model after differentiation for either 18 (d18) or 25 days (d25). We found similar graft size and dopamine (DA) neuron content in both groups, but only the d18 cells resulted in recovery of motor impairments. In contrast, we report that d25 grafts survived equally as well and produced grafts rich in tyrosine hydroxylase-positive neurons, but were incapable of alleviating any motor deficits. We identified the mechanism of action as the extent of neurite outgrowth into the host brain, with d18 grafts supporting significantly more neurite outgrowth than nonfunctional d25 grafts. RNAseq analysis of the cell preparation suggests that graft efficacy may be enhanced by repression of differentiation-associated genes by REST, defining the optimal predifferentiation state for transplantation. This study demonstrates for the first time that DA neuron grafts can survive well in vivo while completely lacking the capacity to induce recovery from motor dysfunction. In contrast to other recent studies, we demonstrate that neurite outgrowth is the key factor determining graft efficacy and our gene expression profiling revealed characteristics of the cells that may predict their efficacy. These data have implication for the generation of DA neuron grafts for clinical application.

Miniature-swine iPSC-derived GABA progenitor cells function in a rat Parkinson's disease model.

Induced pluripotent stem cells (iPS cells) are considered a promising source of cell-based therapy for the treatment of Parkinson's disease (PD). Recent studies have shown forebrain GABA interneurons have crucial roles in many psychiatric disorders, and secondary changes in the GABA system play a directly effect on the pathogenesis of PD. Here, we first describe an efficient differentiation procedure of GABA progenitors (MiPSC-iGABAPs) from miniature-swine iPSCs through two major developmental stages. Then, the MiPSC-iGABAPs were stereotactically transplanted into the right medial forebrain bundle (MFB) of 6-hydroxydopamine (OHDA)-lesioned PD model rats to confirm their feasibility for the neural transplantation as a donor material. Furthermore, the grafted MiPSC-iGABAPs could survive and migrate from the graft site into the surrounding brain tissue including striatum (ST) and substantia nigra (SN) for at least 32 weeks, and significantly improved functional recovery of PD rats from their parkinsonian behavioral defects. Histological studies showed that the grafted cells could migrate and differentiate into various neurocytes, including GABAergic, dopaminergic neurons, and glial cells in vivo, and many induced dopaminergic neurons extended dense neurites into the host striatum. Moreover, over 50% of the grafted MiPSC-iGABAPs could express GABA, and these GABAergic neurons might be responsible for modifying the balance of excitatory and inhibitory signals in the striatum to promote behavioral recovery. Thus, the present study confirmed that the MiPSC-iGABAPs can be used as an attractive donor material for the neural grafting to remodel basal ganglia circuitry in neurodegenerative diseases, avoiding tumorigenicity of iPSCs and the nonproliferative and nondifferentiated potential of mature neurons.

Combined cell-based therapy strategies for the treatment of Parkinson's disease: focus on mesenchymal stromal cells.

Parkinson's disease is a neurodegenerative condition characterized by motor impairments caused by the selective loss of dopaminergic neurons in the substantia nigra. Levodopa is an effective and well-tolerated dopamine replacement agent. However, levodopa provides only symptomatic improvements, without affecting the underlying pathology, and is associated with side effects after long-term use. Cell-based replacement is a promising strategy that offers the possibility to replace lost neurons in Parkinson's disease treatment. Clinical studies of transplantation of human fetal ventral mesencephalic tissue have provided evidence that the grafted dopaminergic neurons can reinnervate the striatum, release dopamine, integrate into the host neural circuits, and improve motor functions. One of the limiting factors for cell therapy in Parkinson's disease is the low survival rate of grafted dopaminergic cells. Different factors could cause cell death of dopaminergic neurons after grafting such as mechanical trauma, growth factor deprivation, hypoxia, and neuroinflammation. Neurotrophic factors play an essential role in the survival of grafted cells. However, direct, timely, and controllable delivery of neurotrophic factors into the brain faces important limitations. Different types of cells secrete neurotrophic factors constitutively and co-transplantation of these cells with dopaminergic neurons represents a feasible strategy to increase neuronal survival. In this review, we provide a general overview of the pioneering studies on cell transplantation developed in patients and animal models of Parkinson's disease, with a focus on neurotrophic factor-secreting cells, with a particular interest in mesenchymal stromal cells; that co-implanted with dopaminergic neurons would serve as a strategy to increase cell survival and improve graft outcomes.

Therapeutic function of a novel rat induced pluripotent stem cell line in a 6­OHDA­induced rat model of Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder of the central nervous system that results from the loss of dopaminergic (DA) nigral neurons. Induced pluripotent stem cells (iPSCs) have shown potential for cell transplantation treatment of neurodegenerative disorders. In the present study, the small molecules CHIR99021 and RepSox (CR) significantly facilitated reprogramming and enhanced the efficiency of GFP+/iPS­like colonies [rat iPSCs induced by OCT3/4, Sox2, Klf4, c­Myc, Nanog and Lin28 + CR (RiPSCs­6F/CR)] generation by ~4.0­fold during lentivirus­mediated reprogramming of six transcription factors in rat embryonic fibroblasts. The generation of iPSCs was detected by reverse transcription­PCR, immunofluorescence and western blot analysis. Subsequently, RiPSCs­6F/CR were stereotactically transplanted into the right medial forebrain bundle (MFB) of 6­hydroxydopamine­lesioned rats with PD. The transplanted RiPSCs­6F/CR survived and functioned in the MFB of rats with PD for ≥20 weeks, and significantly improved functional restoration from their PD­related behavioral defects. Furthermore, the grafted RiPSCs­6F/CR could migrate and differentiate into various neurocytes in vivo, including γ aminobutyric acid­ergic, DA neurons and glial cells. In conclusion, the present study confirmed that RiPSCs­6F/CR induced by small molecules could be used as potential donor material for neural grafting to remodel basal ganglia circuitry in neurodegenerative diseases.

A combined cell and gene therapy approach for homotopic reconstruction of midbrain dopamine pathways using human pluripotent stem cells.

Midbrain dopamine (mDA) neurons can be replaced in patients with Parkinson's disease (PD) in order to provide long-term improvement in motor functions. The limited capacity for long-distance axonal growth in the adult brain means that cells are transplanted ectopically, into the striatal target. As a consequence, several mDA pathways are not re-instated, which may underlie the incomplete restoration of motor function in patients. Here, we show that viral delivery of GDNF to the striatum, in conjunction with homotopic transplantation of human pluripotent stem-cell-derived mDA neurons, recapitulates brain-wide mDA target innervation. The grafts provided re-instatement of striatal dopamine levels and correction of motor function and also connectivity with additional mDA target nuclei not well innervated by ectopic grafts. These results demonstrate the remarkable capacity for achieving functional and anatomically precise reconstruction of long-distance circuitry in the adult brain by matching appropriate growth-factor signaling to grafting of specific cell types.

Stem cell sprays for neurological injuries: a perspective.

Injuries to the brain and spinal cord have major clinical consequences with high costs for healthcare systems. Neural cell transplantation therapies have significant translational potential to promote regeneration post-injury with clinical trials commencing for various pathologies. However, there are challenges associated with current clinical approaches used for systemic or direct delivery of transplant cells to neural tissue in regenerative applications. These include risks associated with surgical microinjection into neural tissue (e.g. haemorrhage, cell clumping) and high cell loss due to systemic clearance or with cell passage through fine gauge needles into densely packed neural tissue. This article presents lines of evidence supporting the concept that cell spray delivery technology can offer significant translational benefits for neural transplantation therapy, versus current cell delivery methods. Potential benefits include rapid/homogenous cell delivery, release over large surface areas, minimal invasiveness, compatibility with neurosurgical procedures in acute injury, no predictable clinical complications and the capacity to combine cell therapies with drug/biomolecule delivery. Accordingly, we consider that the development of cell spray delivery technology represents a key goal to develop advanced cell therapies for regenerative neurology.

Dementia model mice exhibited improvements of neuropsychiatric symptoms as well as cognitive dysfunction with neural cell transplantation.

Elderly patients with dementia suffer from cognitive dysfunctions and neuropsychiatric symptoms (NPS) such as anxiety and depression. Alzheimer's disease (AD) is a form of age-related dementia, and loss of cholinergic neurons is intimately associated with development of AD symptoms. We and others have reported that neural cell transplantation ameliorated cognitive dysfunction in AD model mice. It remains largely unclear whether neural cell transplantation ameliorates the NPS of AD. It would be interesting to determine whether NPS correlates with cognitive dysfunctions before and after neural cell transplantation in AD model mice. Based on the revalidation of our previous data from a Morris water maze test, we found that neural cell transplantation improved anxiety and depression significantly and marginally affected locomotion activity in AD mice. A correlation analysis revealed that the spatial learning function of AD mice was correlated with their NPS scores both before and after cell transplantation in a similar manner. In contrast, in the mice subjected to cell transplantation, spatial reference memory function was not correlated with NPS scores. These results suggested the neural cell transplantation in the AD model mice significantly improved NPS to the same degree as cognitive dysfunctions, possibly via distinct mechanisms, such as the cholinergic and GABAergic systems.

Pluripotent Stem Cell Therapies for Parkinson Disease: Present Challenges and Future Opportunities.

In Parkinson's disease (PD), there are currently no effective therapies to prevent or slow down disease progression. Cell replacement therapy using human pluripotent stem cell (hPSC)-derived dopamine neurons holds considerable promise. It presents a novel, regenerative strategy, building on the extensive history of fetal tissue grafts and capturing the potential of hPSCs to serve as a scalable and standardized cell source. Progress in establishing protocols for the direct differentiation to midbrain dopamine (mDA) neurons from hPSC have catalyzed the development of cell-based therapies for PD. Consequently, several groups have derived clinical-grade mDA neuron precursors under clinical good manufacture practice condition, which are progressing toward clinical testing in PD patients. Here we will review the current status of the field, discuss the remaining key challenges, and highlight future areas for further improvements of hPSC-based technologies in the clinical translation to PD.

First Human Trial of Stem Cell Transplantation in Complex Arrays for Stroke Patients Using the Intracerebral Microinjection Instrument.

BACKGROUND: In preclinical studies, the Intracerebral Microinjection Instrument (IMI) has demonstrated the ability to deliver therapeutics within the brain in 3-dimensional arrays from a single overlying penetration while incurring minimal localized trauma. OBJECTIVE: To evaluate the safety and performance of the IMI in its first use in humans to deliver stem cells in complex configurations within brain regions affected by ischemic injury. METHODS: As part of a phase 1 study, 3 chronically hemiparetic motor stroke patients received intracerebral grafts of the therapeutic stem cell line, NSI-566, using the IMI and its supporting surgical planning software. The patients were 37 to 54 yr old, had ischemic strokes more than 1 yr prior to transplantation, and received Fugl-Meyer motor scale scores of 17-48 at screening. During a single surgical procedure, patients received several neural grafts (42 ± 3) within the peri-infarct region targeted strategically to facilitate neural repair. RESULTS: The IMI enabled multiple cellular deposits to be safely placed peripheral to stroke lesions. The procedure was well tolerated, recovery was uneventful, and there occurred no subsequent complications. The IMI performed reliably throughout the procedures without evident targeting errors. One year after transplantation, all 3 subjects displayed significant clinical improvement, and imaging analysis demonstrated occupation of infarct cavities with new tissue without tumor formation. CONCLUSION: IMI technology permits unprecedented numbers of injections to be tactically placed in 3-dimensional arrays safely and reliably in human subjects.This advanced methodology can optimize the benefits of novel therapeutics by enabling versatile 3-dimensional intracerebral targeting.

Changes in the Distribution of Cell Contacts and Mitotic Cycle Disturbances in Cells of the Allograft of Rat Embryonic Neocortex.

Morphological changes in the allograft of rat anterior cerebral vesicle at the early stages after transplantation into the peripheral nerve of an adult rat were studied by immunohistochemical methods. Immunohistochemical reaction to bromodeoxyuridine showed that the delay of mitotic division in neural stem/progenitor cells in the grafts occurred during S/G2 stage. In transplants of rat embryonic neocortex (E13), changes in the cell cycle of neural stem/progenitor cells in 3 h after transplantation into the nerve correlated with abnormal distribution of adherens junctions and interkinetic nuclear migration.

Roles of Reelin/Disabled1 pathway on functional recovery of hemiplegic mice after neural cell transplantation; Reelin promotes migration toward motor cortex and maturation to motoneurons of neural grafts.

Reelin is a large glycoprotein which regulates central nervous system (CNS) development. Dysfunctions of Reelin were reported on certain neuropsychiatric diseases. We examined involvement of Reelin pathway in functional recovery of hemiplegic mice after neural transplantation. Reelin was expressed 1 day after cryogenic injury of right motor cortex. We transplanted neural stem/progenitor cells (NSPCs) from wild-type mice into ipsilateral striatum of hemiplegic mice. The grafts migrated from the striatum and reached the injured cortex 14 days after transplantation. The transplantation significantly improved their motor functions (P < .05). The NSPCs migrating toward the cortex expressed Reelin receptors, Apoer and Vldlr, and phosphorylated Disabled1 (Dab1), a downstream signaling molecule of Reelin. The grafts expressed Ncadherin and active form of Integrin ß1, both of which were known to become active with Reelin stimulation. At day 28, the grafts expressed Ctip2, Crim1, Foxp2, and Fezf2, all of which were forebrain motoneuron associated markers, and Nfm and Synapsin1 on the damaged cortex. We then transplanted NSPCs of yotari mice (yot/yot genotype) having nonfunctional Dab1 by a mutation of its gene. Majority of the grafts from yotari mice (>80%) did not migrate and thus remained at the striatum. The grafts did not express the forebrain motoneuron associated markers nor the cell adhesion molecules including Ncadherin and active Integrin ß1. Reelin pathway was involved in graft migration by regulating certain adhesion molecules and in their differentiation to functional motoneurons accompanying synapse formation. We suggested involvement of Reelin pathway for neural regeneration and functional recovery of hemiplegic mice in adulthood after neural transplantation.

Grafted Miniature-Swine Neural Stem Cells of Early Embryonic Mesencephalic Neuroepithelial Origin can Repair the Damaged Neural Circuitry of Parkinson's Disease Model Rats.

Although recent progress in the use of human iPS cell-derived midbrain dopaminergic progenitors is remarkable, alternatives are essential in the strategies of treatment of basal-ganglia-related diseases. Attention has been focused on neural stem cells (NSCs) as one of the possible candidates of donor material for neural transplantation, because of their multipotency and self-renewal characteristics. In the present study, miniature-swine (mini-swine) mesencephalic neuroepithelial stem cells (M-NESCs) of embryonic 17 and 18 days grafted in the parkinsonian rat striatum were assessed immunohistochemically, behaviorally and electrophysiologically to confirm their feasibility for the neural xenografting as a donor material. Grafted mini-swine M-NESCs survived in parkinsonian rat striatum at 8 weeks after transplantation and many of them differentiated into tyrosine hydroxylase (TH)-positive cells. The parkinsonian model rats grafted with mini-swine M-NESCs exhibited a functional recovery from their parkinsonian behavioral defects. The majority of donor-derived TH-positive cells exhibited a matured morphology at 8 weeks. Whole-cell recordings from donor-derived neurons in the host rat brain slices incorporating the graft revealed the presence of multiple types of neurons including dopaminergic. Glutamatergic and GABAergic post-synaptic currents were evoked in the donor-derived cells by stimulation of the host site, suggesting they receive both excitatory and inhibitory synaptic inputs from host area. The present study shows that non-rodent mammalian M-NESCs can differentiate into functionally active neurons in the diseased xenogeneic environment and could improve the parkinsonian behavioral defects over the species. Neuroepithelial stem cells could be an attractive candidate as a source of donor material for neural transplantation.

Restorative Strategies in Movement Disorders: the Contribution of Imaging.

PURPOSE OF REVIEW: The purpose of this review was to review the imaging, particularly positron emission tomography (PET), findings in neurorestoration studies in movement disorders, with specific focus on neural transplantation in Parkinson's disease (PD) and Huntington's disease (HD). RECENT FINDINGS: PET findings in PD transplantation studies have shown that graft survival as reflected by increases in dopaminergic PET markers does not necessarily correlate with clinical improvement. PD patients with more denervated ventral striatum and more imbalanced serotonin-to-dopamine ratio in the grafted neurons tended to have worse outcome. In HD transplantation studies, variable graft survival and clinical responses may be related to host inflammatory/immune responses to the grafts. Information gleaned from imaging findings in previous neural transplantation studies has been used to refine study protocol and patient selection in future trials. This includes identifying suitable candidates for transplantation using imaging markers, employing multiple and/or novel PET tracers to better assess graft functions and inflammatory responses to grafts.

Gene Editing, Gene Therapy, and Cell Xenotransplantation: Cell Transplantation Across Species.

PURPOSE OF REVIEW: Cell xenotransplantation has the potential to provide a safe, ethically acceptable, unlimited source for cell replacement therapies. This review focuses on genetic modification strategies aimed to overcome remaining hurdles standing in the way of clinical porcine islet transplantation and to develop neural cell xenotransplantation. RECENT FINDINGS: In addition to previously described genetic modifications aimed to mitigate hyperacute rejection, instant blood-mediated inflammatory reaction, and cell-mediated rejection, new data showing the possibility of increasing porcine islet insulin secretion by transgenesis is an interesting addition to the array of genetically modified pigs available for xenotransplantation. Moreover, combining multiple modifications is possible today thanks to new, improved genomic editing tools. SUMMARY: Genetic modification of large animals, pigs in particular, has come a long way during the last decade. These modifications can help minimize immunological and physiological incompatibilities between porcine and human cells, thus allowing for better tolerance and function of xenocells.

Peptide-Based Scaffolds Support Human Cortical Progenitor Graft Integration to Reduce Atrophy and Promote Functional Repair in a Model of Stroke.

Stem cell transplants offer significant hope for brain repair following ischemic damage. Pre-clinical work suggests that therapeutic mechanisms may be multi-faceted, incorporating bone-fide circuit reconstruction by transplanted neurons, but also protection/regeneration of host circuitry. Here, we engineered hydrogel scaffolds to form "bio-bridges" within the necrotic lesion cavity, providing physical and trophic support to transplanted human embryonic stem cell-derived cortical progenitors, as well as residual host neurons. Scaffolds were fabricated by the self-assembly of peptides for a laminin-derived epitope (IKVAV), thereby mimicking the brain's major extracellular protein. Following focal ischemia in rats, scaffold-supported cell transplants induced progressive motor improvements over 9 months, compared to cell- or scaffold-only implants. These grafts were larger, exhibited greater neuronal differentiation, and showed enhanced electrophysiological properties reflective of mature, integrated neurons. Varying graft timing post-injury enabled us to attribute repair to both neuroprotection and circuit replacement. These findings highlight strategies to improve the efficiency of stem cell grafts for brain repair.

Mechanisms and use of neural transplants for brain repair.

Under appropriate conditions, neural tissues transplanted into the adult mammalian brain can survive, integrate, and function so as to influence the behavior of the host, opening the prospect of repairing neuronal damage, and alleviating symptoms associated with neuronal injury or neurodegenerative disease. Alternative mechanisms of action have been postulated: nonspecific effects of surgery; neurotrophic and neuroprotective influences on disease progression and host plasticity; diffuse or locally regulated pharmacological delivery of deficient neurochemicals, neurotransmitters, or neurohormones; restitution of the neuronal and glial environment necessary for proper host neuronal support and processing; promoting local and long-distance host and graft axon growth; formation of reciprocal connections and reconstruction of local circuits within the host brain; and up to full integration and reconstruction of fully functional host neuronal networks. Analysis of neural transplants in a broad range of anatomical systems and disease models, on simple and complex classes of behavioral function and information processing, have indicated that all of these alternative mechanisms are likely to contribute in different circumstances. Thus, there is not a single or typical mode of graft function; rather grafts can and do function in multiple ways, specific to each particular context. Consequently, to develop an effective cell-based therapy, multiple dimensions must be considered: the target disease pathogenesis; the neurodegenerative basis of each type of physiological dysfunction or behavioral symptom; the nature of the repair required to alleviate or remediate the functional impairments of particular clinical relevance; and identification of a suitable cell source or delivery system, along with the site and method of implantation, that can achieve the sought for repair and recovery.