Neural transplantation

Regenerative medicine for neurological diseases-will regenerative neurosurgery deliver?

Regenerative medicine aspires to transform the future practice of medicine by providing curative, rather than palliative, treatments. Healing the central nervous system (CNS) remains among regenerative medicine's most highly prized but formidable challenges. "Regenerative neurosurgery" provides access to the CNS or its surrounding structures to preserve or restore neurological function. Pioneering efforts over the past three decades have introduced cells, neurotrophins, and genes with putative regenerative capacity into the CNS to combat neurodegenerative, ischemic, and traumatic diseases. In this review we critically evaluate the rationale, paradigms, and translational progress of regenerative neurosurgery, harnessing access to the CNS to protect, rejuvenate, or replace cell types otherwise irreversibly compromised by neurological disease. We discuss the evidence surrounding fetal, somatic, and pluripotent stem cell derived implants to replace endogenous neuronal and glial cell types and provide trophic support. Neurotrophin based strategies via infusions and gene therapy highlight the motivation to preserve neuronal circuits, the complex fidelity of which cannot be readily recreated. We specifically highlight ongoing translational efforts in Parkinson's disease, amyotrophic lateral sclerosis, stroke, and spinal cord injury, using these to illustrate the principles, challenges, and opportunities of regenerative neurosurgery. Risks of associated procedures and novel neurosurgical trials are discussed, together with the ethical challenges they pose. After decades of efforts to develop and refine necessary tools and methodologies, regenerative neurosurgery is well positioned to advance treatments for refractory neurological diseases. Strategic multidisciplinary efforts will be critical to harness complementary technologies and maximize mechanistic feedback, accelerating iterative progress toward cures for neurological diseases.

A balanced evaluation of the evidence for adult neurogenesis in humans: implication for neuropsychiatric disorders

There is a widespread belief that neurogenesis exists in adult human brain, especially in the dentate gyrus, and it is to be maintained and, if possible, augmented with different stimuli including exercise and certain drugs. Here, we examine the evidence for adult human neurogenesis and note important limitations of the methodologies used to study it. A balanced review of the literature and evaluation of the data indicate that adult neurogenesis in human brain is improbable. In fact, in several high-quality recent studies in adult human brain, unlike in adult brains of other species, neurogenesis was not detectable. These findings suggest that the human brain requires a permanent set of neurons to maintain acquired knowledge for decades, which is essential for complex high cognitive functions unique to humans. Thus, stimulation and/or injection of neural stem cells into human brains may not only disrupt brain homeostatic systems, but also disturb normal neuronal circuits. We propose that the focus of research should be the preservation of brain neurons by prevention of damage, not replacement.

Stem cells and motor recovery after stroke

In stroke patients with severe persistent neurological deficits, alternative therapeutic modalities are limited. Stem cell therapy might be an opportunity when the safety profile of this approach will be achieved. This review will give possible mechanisms of restoration of function in animals and a statement of clinical trials in humans. The sources of neural stem cells for therapeutic use will be detailed. Potentials mechanisms of transplanted cell-mediated recovery are described with a particular emphasis on ipsilesional post-stroke plasticity. The optimal conditions for cell transplant therapy after stroke are evoked but not yet clearly defined. Finally, since multimodality imaging will be crucial in the post-transplantation patient assessment, the final part describes recent advances in the in vivo monitoring of repair progress.

Autologous bone marrow stromal cell transplantation for central nervous system disorders - recent progress and perspective for clinical application

There is increasing evidence that the transplanted BMSC significantly promote functional recovery after CNS damage in the animal models of various kinds of CNS disorders, including cerebral infarct, traumatic brain injury and spinal cord injury. However, there are several shortages of information when considering clinical application of BMSC transplantation for patients with CNS disorders. In this review, therefore, we discuss what we should clarify to establish cell transplantation therapy as the scientifically proven entity in clinical situation and describe our recent works for this purpose. The BMSC have the ability to alter their gene expression profile and phenotype in response to the surrounding circumstances and to protect the neurons by producing some neurotrophic factors. They also promote neurite extension and rebuild the neural circuits in the injured CNS. The BMSC can be expanded in vitro using the animal serum-free medium. Pharmacological modulation may accelerate the in vitro proliferation of the BMSC. Using in vivo optical imaging technique, the transplanted BMSC can non-invasively be tracked in the living animals for at least 8 weeks after transplantation. It is urgent issues to develop clinical imaging technique to track the transplanted cells in the CNS and evaluate the therapeutic significance of BMSC transplantation in order to establish it as a definite therapeutic strategy in clinical situation in the future.

Assessing the value of autologous and allogeneic cells for regenerative medicine

The advantages and disadvantages of autologous and allogeneic human cells for regenerative medicine are summarized. The comparison of relative advantages includes: ease and cost of treating large numbers of patients, the speed of availability of therapy and the differing complexity of the development pathways. The comparison of relative disadvantages deals with issues such as variability of source material, the risks of cell abnormality and of viral and prion contamination, and the sensitive issues surrounding use of embryo-derived cells. From the comparisons, several potentially decisive issues are drawn out, such as possible immune response and teratoma formation, the impact of patents and the virtues of hospital versus industry-centered development.

Synergistic effects of granulocyte-colony stimulating factor on bone marrow stromal cell transplantation for mice cerebral infarct

This study was aimed to assess whether ex vivo treatment with granulocyte-colony stimulating factor (G-CSF) modifies biological properties of bone marrow stromal cells (BMSC) and enhances functional recovery by BMSC transplantation into infarct brain. Immunohistochemistry was conducted to characterize the cultured BMSC. The pharmacological effects of G-CSF on their proliferation, cell cycle, and growth factor production were precisely analyzed, using FACS and ELISA techniques. Non-treated or G-CSF treated BMSC were stereotactically transplanted into the mice brain subjected to cerebral infarct, and its effects on functional and histological aspects were evaluated. The BMSC expressed the receptor for G-CSF. Treatment with 0.1muM of G-CSF significantly enhanced the proliferation of BMSC by increasing their population in S phase, and increased their production of SDF-1alpha, HGF, and NGF. When transplanted into infarct brain, G-CSF treated BMSC significantly improved motor function as early as 2 weeks after transplantation, whereas non-treated BMSC did 4 weeks after transplantation. These findings strongly suggest that G-CSF may enhance the proliferation and growth factor production of the cultured BMSC and accelerate functional restoration by BMSC transplantation. Such pharmacological "activation" of the BMSC may contribute to successful clinical application of BMSC transplantation therapy for ischemic stroke.

Everything that glitters isn't gold: a critical review of postnatal neural precursor analyses

Adult neurogenesis research has made enormous strides in the last decade but has been complicated by several failures to replicate promising findings. Prevalent use of highly sensitive methods with inherent sources of error has led to extraordinary conclusions without adequate crossvalidation. Perhaps the biggest culprit is the reliance on molecules involved in DNA synthesis and genetic markers to indicate neuronal neogenesis. In this Protocol Review, we present an overview of common methodological issues in the field and suggest alternative approaches, including viral vectors, siRNA, and inducible transgenic/knockout mice. A multipronged approach will enhance the overall rigor of research on stem cell biology and related fields by allowing increased replication of findings between groups and across systems.