Transplantation of human fetal tissue from spontaneous abortions to a rodent model of Parkinson's disease

Enhanced survival of human-induced pluripotent stem cell transplant in parkinsonian rat brain by locally applied cyclosporine

A major limitation with cell transplantation in patients is the unimpressive number of cells survived. The death of grafted cells involves apoptosis and immunorejection. In this review, we encapsulate the recent preclinical development that improves the survival of grafted cells and mitigates the immunorejection of human-induced pluripotent stem cells (iPSCs) through co-grating nanoparticles-containing cyclosporine A (NanoCsA) in hemiparkinsonian rats. The study supported the notion that NanoCsA allows for long-lasting CsA discharge and limits immunorejection of human iPSC xenograft in a 6-hydroxydopamine Parkinson's disease rat model.

Concise Review: Human-Animal Neurological Chimeras: Humanized Animals or Human Cells in an Animal?

Blastocyst complementation is an emerging methodology in which human stem cells are transferred into genetically engineered preimplantation animal embryos eventually giving rise to fully developed human tissues and organs within the animal host for use in regenerative medicine. The ethical issues surrounding this method have caused the National Institutes of Health to issue a moratorium on funding for blastocyst complementation citing the potential for human cells to substantially contribute to the brain of the chimeric animal. To address this concern, we performed an in-depth review of the neural transplantation literature to determine how the integration of human cells into the nonhuman neural circuitry has altered the behavior of the host. Despite reports of widespread integration of human cell transplants, our review of 150 transplantation studies found no evidence suggestive of humanization of the animal host, and we thus conclude that, at present, concerns over humanization should not prevent research on blastocyst complementation to continue. We suggest proceeding in a controlled and transparent manner, however, and include recommendations for future research with careful consideration for how human cells may contribute to the animal host nervous system. Stem Cells 2019;37:444-452.

Derivation of Adult Human Fibroblasts and their Direct Conversion into Expandable Neural Progenitor Cells

Generation of induced pluripotent stem cell (iPSCs) from adult skin fibroblasts and subsequent differentiation into somatic cells provides fascinating prospects for the derivation of autologous transplants that circumvent histocompatibility barriers. However, progression through a pluripotent state and subsequent complete differentiation into desired lineages remains a roadblock for the clinical translation of iPSC technology because of the associated neoplastic potential and genomic instability. Recently, we and others showed that somatic cells cannot only be converted into iPSCs but also into different types of multipotent somatic stem cells by using defined factors, thereby circumventing progression through the pluripotent state. In particular, the direct conversion of human fibroblasts into induced neural progenitor cells (iNPCs) heralds the possibility of a novel autologous cell source for various applications such as cell replacement, disease modeling and drug screening. Here, we describe the isolation of adult human primary fibroblasts by skin biopsy and their efficient direct conversion into iNPCs by timely restricted expression of Oct4, Sox2, Klf4, as well as c-Myc. Sox2-positive neuroepithelial colonies appear after 17 days of induction and iNPC lines can be established efficiently by monoclonal isolation and expansion. Precise adjustment of viral multiplicity of infection and supplementation of leukemia inhibitory factor during the induction phase represent critical factors to achieve conversion efficiencies of up to 0.2%. Thus far, patient-specific iNPC lines could be expanded for more than 12 passages and uniformly display morphological and molecular features of neural stem/progenitor cells, such as the expression of Nestin and Sox2. The iNPC lines can be differentiated into neurons and astrocytes as judged by staining against TUJ1 and GFAP, respectively. In conclusion, we report a robust protocol for the derivation and direct conversion of human fibroblasts into stably expandable neural progenitor cells that might provide a cellular source for biomedical applications such as autologous neural cell replacement and disease modeling.

Therapeutic strategies in multiple sclerosis. II. Long-term repair

Spontaneous myelin repair in multiple sclerosis (MS) provides a striking example of the brain's inherent capacity for sustained and stable regenerative tissue repair--but also clearly emphasizes the limitations of this capacity; remyelination ultimately fails widely in many patients, and disability and handicap accumulate. The observation of endogenous partial myelin repair has raised the possibility that therapeutic interventions designed to supplement or promote remyelination might have a useful and significant impact both in the short term, in restoring conduction, and in the long term, in safeguarding axons. Therapeutic remyelination interventions must involve manipulations to either the molecular or the cellular environment within lesions; both depend crucially on a detailed understanding of the biology of the repair process and of those glia implicated in spontaneous repair, or capable of contributing to exogenous repair. Here we explore the biology of myelin repair in MS, examining the glia responsible for successful remyelination, oligodendrocytes and Schwann cells, their 'target' cells, neurons and the roles of astrocytes. Options for therapeutic remyelinating strategies are reviewed, including glial cell transplantation and treatment with growth factors or other soluble molecules. Clinical aspects of remyelination therapies are considered--which patients, which lesions, which stage of the disease, and how to monitor an intervention--and the remaining obstacles and hazards to these approaches are discussed.