Noradrenergic Components of Locomotor Recovery Induced by Intraspinal Grafting of the Embryonic Brainstem in Adult Paraplegic Rats.

Intraspinal grafting of serotonergic (5-HT) neurons was shown to restore plantar stepping in paraplegic rats. Here we asked whether neurons of other phenotypes contribute to the recovery. The experiments were performed on adult rats after spinal cord total transection. Grafts were injected into the sub-lesional spinal cord. Two months later, locomotor performance was tested with electromyographic recordings from hindlimb muscles. The role of noradrenergic (NA) innervation was investigated during locomotor performance of spinal grafted and non-grafted rats using intraperitoneal application of α2 adrenergic receptor agonist (clonidine) or antagonist (yohimbine). Morphological analysis of the host spinal cords demonstrated the presence of tyrosine hydroxylase positive (NA) neurons in addition to 5-HT neurons. 5-HT fibers innervated caudal spinal cord areas in the dorsal and ventral horns, central canal, and intermediolateral zone, while the NA fiber distribution was limited to the central canal and intermediolateral zone. 5-HT and NA neurons were surrounded by each other's axons. Locomotor abilities of the spinal grafted rats, but not in control spinal rats, were facilitated by yohimbine and suppressed by clonidine. Thus, noradrenergic innervation, in addition to 5-HT innervation, plays a potent role in hindlimb movement enhanced by intraspinal grafting of brainstem embryonic tissue in paraplegic rats.

Cerebral organoids transplantation improves neurological motor function in rat brain injury.

BACKGROUND AND PURPOSE: Cerebral organoids (COs) have been used for studying brain development, neural disorders, and species-specific drug pharmacology and toxicology, but the potential of COs transplantation therapy for brain injury remains to be answered. METHODS: With preparation of traumatic brain injury (TBI) model of motor dysfunction, COs at 55 and 85 days (55 and 85 d-CO) were transplanted into damaged motor cortex separately to identify better transplantation donor for brain injury. Further, the feasibility, effectiveness, and underlying mechanism of COs transplantation therapy for brain injury were explored. RESULTS: 55 d-CO was demonstrated as better transplantation donor than 85 d-CO, evidenced by more neurogenesis and higher cell survival rate without aggravating apoptosis and inflammation after transplantation into damaged motor cortex. Cells from transplanted COs had the potential of multilinage differentiation to mimic in-vivo brain cortical development, support region-specific reconstruction of damaged motor cortex, form neurotransmitter-related neurons, and migrate into different brain regions along corpus callosum. Moreover, COs transplantation upregulated hippocampal neural connection proteins and neurotrophic factors. Notably, COs transplantation improved neurological motor function and reduced brain damage. CONCLUSIONS: This study revealed 55 d-CO as better transplantation donor and demonstrated the feasibility and efficacy of COs transplantation in TBI, hoping to provide first-hand preclinical evidence of COs transplantation for brain injury.

Engineering advanced neural tissue constructs to mitigate acute cerebral inflammation after brain transplantation in rats.

Stroke, traumatic brain injuries, and other similar conditions often lead to significant loss of functional brain tissue and associated disruption of neuronal signaling. A common strategy for replacing lost neurons is the injection of dissociated neural stem cells or differentiated neurons. However, this method is unlikely to be suitable for replacing large brain cavities, and the resulting distribution of neurons may lack the necessary architecture to support appropriate brain function. Engineered neural tissues may be a viable alternative. Cell death is a prominent concern in neuronal grafting studies, a problem that could be magnified with the transplantation of engineered neural tissues. Here, we examined the effect of one contributor to cell death, acute cerebral inflammation, on neuronal survival after the transplantation of bioengineered constructs based on silk scaffolds. We found evidence of a high degree of inflammation and poor neuronal survival after introducing engineered constructs into the motor cortex of rats. Integrating a corticosteroid (methylprednisolone) into the constructs resulted in significantly improved neuron survival during the acute phase of inflammation. The improved construct survival was associated with decreased markers of inflammation and an anti-inflammatory state of the immune system due to the steroid treatment.

Neurotransplantation therapy.

Neurotransplantation may be a promising approach for therapy of cerebellar diseases characterized by a substantial loss of neurons. Neurotransplantation could rescue neurons from degeneration and maintain cerebellar reserve, facilitate cerebellar compensation, or help reconstruct damaged neural circuits by cell substitution. These mechanisms of action can be of varying importance according to the type of cerebellar disease. Neurotransplantation therapy in cerebellar ataxias is still at the stage of experimental studies. There is currently little knowledge regarding cerebellar patients. Nevertheless, data provided by experiments in animal models of cerebellar degeneration and both clinical studies and experiences in patients with other neurologic diseases enable us to suggest basic principles, expectations, limitations, and future directions of neurotransplantation therapy for cerebellar diseases.

Survival of iPSC-derived grafts within the striatum of immunodeficient mice: Importance of developmental stage of both transplant and host recipient.

Degeneration of the striatum can occur in multiple disorders with devastating consequences for the patients. Infantile infections with streptococcus, measles, or herpes can cause striatal necrosis associated with dystonia or dyskinesia; and in patients with Huntington's disease the striatum undergoes massive degeneration, leading to behavioral, psychological and movement issues, ultimately resulting in death. Currently, only supportive therapies are available for striatal degeneration. Clinical trials have shown some efficacy using transplantation of fetal-derived primary striatal progenitors. Large banks of fetal progenitors that give rise to medium spiny neurons (MSNs), the primary neuron of the striatum, are needed to make transplantation therapy a reality. However, fetal tissue is of limited supply, has ethical concerns, and is at risk of graft immunorejection. An alternative potential source of MSNs is induced pluripotent stem cells (iPSCs), adult somatic tissues reprogrammed back to a stem cell fate. Multiple publications have demonstrated the ability to differentiate striatal MSNs from iPSCs. Previous publications have demonstrated that the efficacy of fetal progenitor transplants is critically dependent upon the age of the donor embryo/fetus as well as the age of the transplant recipient. With the advent of iPSC technology, a question that remains unanswered concerns the graft's "age," which is crucial since transplanting pluripotent cells has an inherent risk of over proliferation and teratoma formation. Therefore, in order to also determine the effect of transplant recipient age on the graft, iPSCs were differentiated to three stages along a striatal differentiation paradigm and transplanted into the striatum of both neonatal and adult immunodeficient mice. This study demonstrated that increased murine transplant-recipient age (adult vs neonate) resulted in decreased graft survival and volume/rostro-caudal spread after six weeks in vivo, regardless of "age" of the cells transplanted. Importantly, this study implicates that the in vivo setting may provide a better neurogenic niche for iPSC-based modeling as compared to the in vitro setting. Together, these results recapitulate findings from fetal striatal progenitor transplantation studies and further demonstrate the influence of the host environment on cellular survival and maturation.

The immunologic considerations in human head transplantation.

The idea of head transplantation appears at first as unrealistic, unethical, and futile. Here we discuss immunological considerations in human head transplantation. In a separate accompanying article we discuss surgical, ethical, and psychosocial issues concerned in body-to-head transplantation (BHT) [1]. The success of such an unusual allograft, where the donor and the recipient can reject each other, depends on prevention of complex immunologic reactions, especially rejection of the head by the body (graft-vs-host) or probably less likely, the possibility of the head rejecting the total body allograft (host-vs-graft). The technical and immunologic difficulties are enormous, especially since rapid nerve and cord connections and regeneration have not yet been possible to achieve. In this article we begin by briefly reviewing neuro-immunologic issues that may favor BHT such as the blood brain barrier (BBB) and point out its shortcomings. And we touch on the cellular and humoral elements in the brain proper that differ in some respects from those in other organs and in the periphery. Based on recent successes in vascular composite allografts (VCAs), we will elaborate on potential specific advantages and difficulties in BHT of various available immunosuppressive medications already utilized in VCAs. The risk/benefit ratio of these drugs will be emphasized in relation to direct brain toxicity such as seizure disorders, interference, or promotion of nerve regeneration, and potentiation of cerebral viral infections. The final portion of this article will focus on pre-transplant immunologic manipulation of the deceased donor body along with pretreatment of the recipient.

Brain protection during cephalosomatic anastomosis.

Cephalosomatic anastomosis requires neuroprotective techniques, such as deep hypothermia, to preserve brain activity. Despite the failure of pharmacologic neuroprotection, new strategies, including ischemic pre- and postconitioning and the use of Perftoran, have to be explored to complement hypothermia. This article summarizes the field of brain protection during CSA and these promising strategies.

Human striatum remodelling after neurotransplantation in Huntington's disease.

BACKGROUND: Restoration of functions in Huntington's disease (HD) by neurotransplantation stems from the formation of a striatum-like structure capable of establishing host connections as a result of grafted striatal neuroblast maturation. For the first time, we demonstrated some developmental steps accomplished by progenitor cells in the brain of an HD patient and analysed the molecular asset of the human primordium. CASE REPORT: Surgery involved bilateral (two sessions) stereotactic, caudate-putaminal transplantation of whole ganglionic eminence fragments from single legally aborted fetuses. MRI showed that the tissue deposits of the left hemisphere grew and joined to constitute a single tissue mass that remodelled basal ganglia anatomy and remained stable in size over time. No evidence of graft growth was observed contralaterally. PET demonstrated increased striatal and stable cortical metabolism. Unified Huntington's Disease Rating Scale assessments demonstrated improvement of motor performances, which faded over the 36-month follow-up. Cognitive performance tended to decrease at a lower rate than before transplantation. CONCLUSION: The striatal primordium grew into the host brain and this process was associated with metabolic change and some clinical benefit. The study suggests the plasticity and reparative potential of un-manipulated primordium in an era where promising cell-based therapies are still in their infancy.

Autologous dural substitutes: a prospective study.

OBJECTIVE: Duraplasty can be performed both by means of autologous tissues (such as galea-pericranium, temporal muscle, fascia lata) or by commercially available dural patches. Nowadays many neurosurgeons consider galea-pericranium duraplasty time-consuming, technically demanding or not adequate, thus dural surrogates are increasingly popular. In this prospective research we compared duraplasty using autologous galea-pericranium vs. dural patches in terms of postoperative long term results, ease/time required and costs. PATIENTS AND METHODS: Research has been designed as prospective cohort study, that included 185 patients undergoing supratentorial elective neurosurgery with galea-pericranium or non-autologous duraplasty (minimum follow-up 12 months). Variables taken into account were: wound infection, CSF fistula, subcutaneous CSF collection, bone flap osteitis, brain abscess, empyema and tardive wound dehiscence (particularly after postoperative radiotherapy). Time for galea-pericranium collection, size of galea-pericranium harvest and dural defects were recorded in each case. Costs for non-autologous duroplasty were calculated. RESULTS: No statistically significant differences were evident in long term postoperative results between the two groups. Mean time of galea-pericranium collection is less than 2min and enough galea-pericranium can be harvested in supratentorial approach to cover almost any dural defect. The only difference between the two groups is costs: an average of 268.7€/patient spent just for duraplasty. This figure is surely substantial if considered for the entire amount of surgeries performed in a department. CONCLUSIONS: Considering that in our study long term results are equivalent, that galea-pericranium duraplasty is feasible and rapid, our indications are in favor of saving a considerable amount of money since an ideal autologous dural substitute is available and "free".

Anticonvulsant effects by bilateral and unilateral transplantation of GABA-producing cells into the subthalamic nucleus in an acute seizure model.

Neural transplantation of GABA-producing cells into key structures within seizure-suppressing circuits holds promise for medication-resistant epilepsy patients not eligible for resection of the epileptic focus. The substantia nigra pars reticulata (SNr), a basal ganglia output structure, is well known to modulate different seizure types. A recent microinjection study by our group indicated that the subthalamic nucleus (STN), which critically regulates nigral activity, might be a more promising target for focal therapy in epilepsies than the SNr. As a proof of principle, we therefore assessed the anticonvulsant efficacy of bilateral and unilateral allografting of GABA-producing cell lines into the STN using the timed intravenous pentylenetetrazole seizure threshold test, which allows repeated seizure threshold determinations in individual rats. We observed (a) that grafted cells survived up to the end of the experiments, (b) that anticonvulsant effects can be induced by bilateral transplantation into the STN using immortalized GABAergic cells derived from the rat embryonic striatum and cells additionally transfected to obtain higher GABA synthesis than the parent cell line, and (c) that anticonvulsant effects were observed even after unilateral transplantation into the STN. Neither grafting of control cells nor transplantation outside the STN induced anticonvulsant effects, emphasizing the site and cell specificity of the observed anticonvulsant effects. To our knowledge, the present study is the first showing anticonvulsant effects by grafting of GABA-producing cells into the STN. The STN can be considered a highly promising target region for modulation of seizure circuits and, moreover, has the advantage of being clinically established for functional neurosurgery.

Transplantation of human fetal tissue for neurodegenerative diseases: validation of a new protocol for microbiological analysis and bacterial decontamination.

Restorative cell therapy concepts in neurodegenerative diseases are aimed at replacing lost neurons. Despite advances in research on pluripotent stem cells, fetal tissue from routine elective abortions is still regarded as the only safe cell source. Progenitor cells isolated from distinct first-trimester fetal CNS regions have already been used in clinical trials and will be used again in a new multicenter trial funded by the European Union (TRANSEURO). Bacterial contamination of human fetal tissue poses a potential risk of causing infections in the brain of the recipient. Thus, effective methods of microbial decontamination and validation of these methods are required prior to approval of a neurorestorative cell therapy trial. We have developed a protocol consisting of subsequent washing steps at different stages of tissue processing. Efficacy of microbial decontamination was assessed on rat embryonic tissue incubated with high concentrations of defined microbe solutions including representative bacterial and fungal species. Experimental microbial contamination was reduced by several log ranks. Subsequently, we have analyzed the spectrum of microbial contamination and the effect of subsequent washing steps on aborted human fetal tissue; 47.7% of the samples taken during human fetal tissue processing were positive for a microbial contamination, but after washing, no sample exhibited bacterial growth. Our data suggest that human fetal tissue for neural repair can carry microbes of various species, highlighting the need for decontamination procedures. The decontamination protocol described in this report has been shown to be effective as no microbes could be detected at the end of the procedure.

Is the adult mouse striatum a hostile host for neural transplant survival?

Human donor cells, including neurally directed embryonic stem cells and induced pluripotent stem cells with the potential to be used for neural transplantation in a range of neurodegenerative disorders, must first be tested preclinically in rodent models of disease to demonstrate safety and efficacy. One strategy for circumventing the rejection of xenotransplanted human cells is to desensitize the host animal to human cells in the early neonatal period so that a subsequent transplant in adulthood is not immunorejected. This method has been robustly validated in the rat, but currently not in the mouse in which most transgenic models of neurodegeneration have been generated. Thus, we set out to determine whether this could be achieved through modification of the existing rat protocol. Mice were inoculated in the neonatal period with a suspension of human embryonic cortical tissue of varying cell numbers, and received a subsequent human embryonic cortical tissue cell transplant in adulthood. Graft survival was compared with those in mice immunosuppressed with cyclosporine A and those receiving allografts of mouse whole ganglionic eminence tissue. Poor survival was found across all groups, suggesting a general problem with the use of mouse hosts for testing human donor cells.

Microtransplantation of whole ganglionic eminence cells ameliorates motor deficit, enlarges the volume of grafts, and prolongs survival in a rat model of Huntington's disease.

Studies have demonstrated that embryonic cell therapy is a potential approach for the treatment of Huntington's disease (HD). However, because of the limited resource of embryos, greater attention is needed in developing more efficient surgical techniques that not only enhance the therapy outcome but also avoid inefficient therapeutics of transplantation. In this study, we explored the curative effects of two different transplantation methods using a rat model of HD. Whole ganglionic eminence (WGE) cells or phosphate-buffered saline were transplanted into unilateral striatum of quinolinic acid (QA)-lesioned rats using microtransplantation instruments (with an outer diameter of 50 µm) or traditional transplantation instruments (with an outer diameter of 470 µm). Apomorphine-induced rotation test and adjusting step test were assessed after QA-induced lesion and 2, 4, 6, 8, 10, and 12 weeks after transplantation. The expression of neuronal nuclei (NeuN), dopamine, cAMP-regulated phosphoprotein of molecular weight 32 kDa (DARPP-32), and glial fibrillary acidic protein (GFAP) was analyzed at 12 weeks after transplantation. We observed that microtransplanted rats performed better in the stepping test and had higher numbers of DARPP-32-positive cells compared with traditionally transplanted rats. Moreover, microtransplantation group showed lower GFAP expression surrounding the grafts in unilateral striatum and a higher survival rate posttransplantation compared with the traditional transplantation group. We conclude that microtransplantation is capable of enhancing therapeutic efficacy in the rat model of HD. This finding establishes the basis of an alternative transplantation strategy for treatment of HD.

Long distance directional growth of dopaminergic axons along pathways of netrin-1 and GDNF.

Different experimental and clinical strategies have been used to promote survival of transplanted embryonic ventral mesencephalic (VM) neurons. However, few studies have focused on the long-distance growth of dopaminergic axons from VM transplants. The aim of this study is to identify some of the growth and guidance factors that support directed long-distance growth of dopaminergic axons from VM transplants. Lentivirus encoding either glial cell line-derived neurotrophic factor (GDNF) or netrin-1, or a combination of lenti-GDNF with either lenti-GDNF family receptor α1 (GFRα-1) or lenti-netrin-1 was injected to form a gradient along the corpus callosum. Two weeks later, a piece of embryonic day 14 VM tissue was transplanted into the corpus callosum adjacent to the low end of the gradient. Results showed that tyrosine hydroxylase (TH(+)) axons grew a very short distance from the VM transplants in control groups, with few axons reaching the midline. In GDNF or netrin-1 expressing groups, more TH(+) axons grew out of transplants and reached the midline. Pathways co-expressing GDNF with either GFRα-1 or netrin-1 showed significantly increased axonal outgrowth. Interestingly, only the GDNF/netrin-1 combination resulted in the majority of axons reaching the distal target (80%), whereas along the GDNF/GFRα-1 pathway only 20% of the axons leaving the transplant reached the distal target. This technique of long-distance axon guidance may prove to be a useful strategy in reconstructing damaged neuronal circuits, such as the nigrostriatal pathway in Parkinson's disease.

Stem cells expanded from the human embryonic hindbrain stably retain regional specification and high neurogenic potency.

Stem cell lines that faithfully maintain the regional identity and developmental potency of progenitors in the human brain would create new opportunities in developmental neurobiology and provide a resource for generating specialized human neurons. However, to date, neural progenitor cultures derived from the human brain have either been short-lived or exhibit restricted, predominantly glial, differentiation capacity. Pluripotent stem cells are an alternative source, but to ascertain definitively the identity and fidelity of cell types generated solely in vitro is problematic. Here, we show that hindbrain neuroepithelial stem (hbNES) cells can be derived and massively expanded from early human embryos (week 5-7, Carnegie stage 15-17). These cell lines are propagated in adherent culture in the presence of EGF and FGF2 and retain progenitor characteristics, including SOX1 expression, formation of rosette-like structures, and high neurogenic capacity. They generate GABAergic, glutamatergic and, at lower frequency, serotonergic neurons. Importantly, hbNES cells stably maintain hindbrain specification and generate upper rhombic lip derivatives on exposure to bone morphogenetic protein (BMP). When grafted into neonatal rat brain, they show potential for integration into cerebellar development and produce cerebellar granule-like cells, albeit at low frequency. hbNES cells offer a new system to study human cerebellar specification and development and to model diseases of the hindbrain. They also provide a benchmark for the production of similar long-term neuroepithelial-like stem cells (lt-NES) from pluripotent cell lines. To our knowledge, hbNES cells are the first demonstration of highly expandable neuroepithelial stem cells derived from the human embryo without genetic immortalization.

Survival, differentiation, and connectivity of ventral mesencephalic dopamine neurons following transplantation.

The reconstruction of midbrain dopamine (DA) circuitry through intracerebral transplantation of new DA neurons contained in embryonic ventral mesencephalon (VM) is a promising therapeutic approach for Parkinson's disease (PD). Although some of the early open-label trials have provided proof-of-principal that VM grafts can provide sustained improvement of motor function in some patients, subsequent trials showed that the functional response can be highly variable. This chapter reviews an extensive body of basic and clinical research on the survival, differentiation, and connectivity of DA neurons in VM grafts, and also looks at how these parameters are affected by certain host- and donor-specific variables. We also review how technical advances in the tools available to study the integration of grafted DA neurons, such as transgenic reporter mice, have made significant contributions to our understanding of the capacity of different DA neuronal subtypes for target-directed growth and innervation of appropriate host brain structures. Our established and on-going understanding of the capacity of grafted DA neurons to structurally and functionally integrate following transplantation forms an important basis for the refinement and optimization of VM grafting procedures, and also the development of new procedures based on the use of stem cells.

Current status of clinical trials of neural transplantation in Parkinson's disease.

There is a major unmet need for therapies for Parkinson's disease (PD) that go beyond treating symptoms and instead modify the course of the disease. The use of neural transplantation to repair the degenerating dopaminergic nigrostriatal pathway is one strategy by which this might be achieved. A series of small, independent open-label studies initially reported beneficial effects in patients treated with cell transplants derived from the fetal ventral mesencephalon. However, this initial promise was subsequently tempered by negative results from two larger, randomized studies, and the emergence of complications related to the procedure. The reason for these discordant results has been debated and this has led to the development of a new, multicenter, collaborative study--TRANSEURO--which will ultimately herald the next generation of clinical trials of cell therapy in PD, including those involving stem cells. In this chapter, we discuss what has been learned from previous studies of neural transplantation and go on to consider how relevant disease-modifying effects could be demonstrated in PD. We then go on to discuss how the design of future trials of transplantation-based therapies might be better conceived and executed.

In vivo imaging of the integration and function of nigral grafts in clinical trials.

In vivo functional imaging has provided objective evidence for the integration and function of nigral grafts in the brains of patients with Parkinson's disease. Clinical trials with the use of positron emission tomography have shown that transplants of human dopamine-rich fetal ventral mesencephalic tissue can survive, grow, and release dopamine providing motor symptom relief, and also that they can restore brain activation related to movement. Positron emission tomography has aided in the elucidation of the pathophysiology of serious adverse effects, so-called graft-induced dyskinesias. With the use of newly established radioligands, positron emission tomography and single-photon emission computed tomography could help to improve Parkinson's patient selection in future clinical trials by selecting those with better predicted outcomes. Moreover, positron emission tomography could help monitoring postoperational inflammatory processes around the grafted tissue and the effect of immunosuppression. Recent evidence from positron emission tomography has provided insight of how ongoing extrastriatal serotonergic denervation may have relevance to nonmotor symptoms in transplanted Parkinson's disease patients indicating new cell therapy targets for a more complete relief of symptoms. Functional and structural magnetic resonance imaging techniques could help to better assess the integration of nigral graft with the host brain by assessing the restoration of brain activation during movement and of functional and structural connectivity. This knowledge should lead to the development of new, optimized in vivo imaging protocols that could help to better schedule, monitor, and modify the clinical outcomes of future human trials assessing the efficacy of fetal or stem cell therapy in Parkinson's disease.

Long-term expansion of human foetal neural progenitors leads to reduced graft viability in the neonatal rat brain.

We previously reported that early passage human foetal neural progenitors (hFNPs) survive long-term in the rodent host brain whereas late passage cells disappear at later post-graft survival times. The extent to which this finding is related to changes in the expanded FNPs or in the adult host brain environment was not determined. Here we report the effect of expanding hFNPs for different periods of time in vitro on their ability to survive transplantation into the neonatal rat hippocampus, a generally more permissive environment than the adult rat brain. After 2 and 8 weeks in vitro, transplanted hFNPs formed large grafts, most of which survived well until at least 12 weeks. However, following continued expansion, hFNPs formed smaller grafts, and cells transplanted after 20 weeks expansion produced no surviving grafts, even at early survival times. To determine whether this could be due to a dilution of "true" neural stem cells through more differentiated progeny over time in culture, we derived homogeneous neural stem (NS) cells grown as a monolayer from the 8 week expanded hFNPs. These cells homogeneously expressed the neural stem cell markers sox-2, 3CB2 and nestin and were expanded for 5 months before transplantation into the neonatal rat brain. However, these cells exhibited a similar survival profile to the long-term expanded FNPs. These results indicate that, while the cellular phenotype of neural stem cells may appear to be stable in vitro using standard markers, expansion profoundly influences the ability of such cells to form viable grafts.