Vigorous Neuronal Differentiation of Amplified and Grafted Basic Fibroblast Growth Factor-Responsive Neurospheres Derived from Neuroepithelial Stem Cells

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.

Transplantation of Neural Crest-Like Cells Derived from Induced Pluripotent Stem Cells Improves Diabetic Polyneuropathy in Mice

Impaired vascularity and nerve degeneration are the most important pathophysiological abnormalities of diabetic polyneuropathy (DPN). Therefore, regeneration of both the vascular and nervous systems is required for the treatment of DPN. The neural crest (NC) is a transient embryonic structure in vertebrates that differentiates into a vast range of cells, including peripheral neurons, Schwann cells, and vascular smooth muscle cells. In this study, we investigated the ability of transplantation of NC-like (NCL) cells derived from aged mouse induced pluripotent stem (iPS) cells in the treatment of DPN. iPS cells were induced to differentiate into neural cells by stromal cell-derived inducing activity (SDIA) and subsequently supplemented with bone morphogenetic protein 4 to promote differentiation of NC lineage. After the induction, p75 neurotrophin receptor-positive NCL cells were purified using magnetic-activated cell sorting. Sorted NCL cells differentiated to peripheral neurons, glial cells, and smooth muscle cells by additional SDIA. NCL cells were transplanted into hind limb skeletal muscles of 16-week streptozotocin-diabetic mice. Nerve conduction velocity, current perception threshold, intraepidermal nerve fiber density, sensitivity to thermal stimuli, sciatic nerve blood flow, plantar skin blood flow, and capillary number-to-muscle fiber ratio were evaluated. Four weeks after transplantation, the engrafted cells produced growth factors: nerve growth factor, neurotrophin 3, vascular endothelial growth factor, and basic fibroblast growth factor. It was also confirmed that some engrafted cells differentiated into vascular smooth muscle cells or Schwann cell-like cells at each intrinsic site. The transplantation improved the impaired nerve and vascular functions. These results suggest that transplantation of NCL cells derived from iPS cells could have therapeutic effects on DPN through paracrine actions of growth factors and differentiation into Schwann cell-like cells and vascular smooth muscle cells.

Directed fiber outgrowth from transplanted embryonic cortex-derived neurospheres in the adult mouse brain

Neural transplantation has emerged as an attractive strategy for the replacement of neurons that have been lost in the central nervous system. Multipotent neural progenitor cells are potentially useful as donor cells to repopulate the degenerated regions. One important aspect of a transplantation strategy is whether transplanted cells are capable of fiber outgrowth with the aim of rebuilding axonal connections within the host brain. To address this issue, we expanded neuronal progenitor from the cortex of embryonic day 15 ubiquitously green fluorescent protein-expressing transgenic mice as neurospheres in vitro and grafted them into the entorhinal cortex of 8-week-old mice immediately after a perforant pathway lesion. After transplantation into a host brain with a lesion of the entorhino-hippocampal projection, the neurosphere-derived cells extended long fiber projections directed towards the dentate gyrus. Our results indicate that transplantation of neurosphere-derived cells might be a promising strategy to replace lost or damaged axonal projections.

Dopaminergic differentiation of grafted GFP transgenic neuroepithelial stem cells in the brain of a rat model of Parkinson's disease

Neuroepithelial stem cells (NEPs) possess multipotent potential for self-renewal and neuronal differentiation. Using green fluorescent protein (GFP) positive NEPs, we explored, firstly, the survival and differentiation of grafted NEPs in the host rat and, secondly, whether or not transplantation of NEPs is a feasible therapeutic option for treating Parkinson's disease. NEPs were harvested from the neural tube of enhanced GFP transgenic embryos. In culture, GFP(+) NEPs generated abundant neurospheres and differentiated into both neurons and glia. When stereotaxically transplanted into the 6-hydroxydopamine (6-OHDA)-lesioned striatum of rats, NEPs survived and tyrosine hydroxylase (TH)-positive cells were detected in the graft. Furthermore, these grafted GFP(+) NEPs significantly ameliorated Parkinsonian behavioral symptoms compared with controls which were treated only with normal saline. Our results suggest that transplanted NEPs accomplish dopaminergic differentiation may be used for treating Parkinson's disease.

Neural-tube-derived neuroepithelial stem cells: a new transplant resource for Parkinson's disease

To assess the feasibility of using neuroepithelial stem cells as a transplant source for Parkinson's disease, neuroepithelial cells were harvested from the neural tube, cultured and stereotactically transplanted into the striatum of a rat model of Parkinson's disease. In culture, neuroepithelial cells generated abundant neurospheres and differentiated into both neurons and glia. After transplantation, tyrosine-hydroxylase-positive cells were detected in the graft. Furthermore, an apomorphine-induced rotation test showed that the implanted cells successfully promoted functional recovery in animals that underwent this transplantation procedure. Our results demonstrate that neuroepithelial cells may be a new source of donor material for Parkinson's disease.

Stem Cells in Cell Transplantation

This commentary documents the increased number of stem cell-related research reports recently published in the cell transplantation field in the journal Cell Transplantation. The journal covers a wide range of issues in cell-based therapy and regenerative medicine and is attracting clinical and preclinical articles from around the world. It thereby complements and extends the basic coverage of stem cell physiology reported in Stem Cells and Development. Sections in Cell Transplantation cover neuroscience, diabetes, hepatocytes, bone, muscle, cartilage, skin, vessels, and other tissues, as well as tissue engineering that employs novel methods with stem cells. Clearly, the continued use of biomedical engineering will depend heavily on stem cells, and these two journals are well positioned to provide comprehensive coverage of these developments.

Alterations in cellular phenotypes differentiating from embryonic rat brain neurosphere cultures by immunoselection of neuronal progenitors

The neurosphere culture system is widely used to expand neural stem/progenitor cells in vitro and to provide a source of cells for transplantation approaches to CNS disorders. This study describes the populations of neurones, astrocytes and oligodendrocytes which differentiated from embryonic day (E) 14 rat cortical and striatal tissue grown as neurosphere cultures over three passages. The percentages of cells that adopted neuronal phenotypes decreased with passage, astrocytic percentages increased and oligodendrocytic percentages remained constant. In the second part of this study, immunomagnetic separation was used to positively select neuronal progenitor cells from E14 rat cortical and striatal tissue using an antibody, 2F7, which recognises an epitope on the cell surface of pre- and post-mitotic neurones. These immunomagnetically selected cells were grown as neurosphere cultures over three passages and gave rise to significantly different percentages of neurones, astrocytes and oligodendrocytes than those found in the baseline study. In particular, the percentage of neurones arising from the second and third passages was significantly higher following immunoselection. This indicates that neuronal progenitor cells can be isolated using immunomagnetic separation and then expanded using the neurosphere culture system, to generate enriched populations of neurones that can be used in CNS repair.

Potential functional neural repair with grafted neural stem cells of early embryonic neuroepithelial origin

The fate of grafted neuroepithelial stem cells in the normal mature brain environment was assessed both morphologically and electrophysiologically to confirm their feasibility in the functional repair of damaged neural circuitry. The neuroepithelial stem cells were harvested from the mesencephalic neural plate of transgenic green fluorescence protein-carrying rat embryos, and implanted into the normal adult rat striatum. The short- and long-term differentiation pattern of donor-derived cells was precisely monitored immunohistochemically. The functional abilities of the donor-derived cells and communication between them and the host were investigated using host-rat brain slices incorporating the graft with whole-cell patch-clamp recording. Vigorous differentiation of the neuroepithelial stem cells into mostly neurons was noted in the short-term with positive staining for tyrosine hydroxylase, suggesting that the donor-derived cells were exclusively following their genetically programmed fate, together with gamma-aminobutyric acid (GABA) and glutamate expression. In the long-term, the large number of donor-derived neurons was sustained, but the staining pattern showed expression of dopamine- and adenosine 3':5'-monophosphate-regulated phosphoprotein 32, suggesting that some neurons were following environmental cues, together with the appearance of some cholinergic neurons. Some donor-derived astrocytes were also seen in the graft. Many action potentials indicating the presence of both dopaminergic and non-dopaminergic patterns could be elicited and recorded in the donor-derived neurons in addition to spontaneous glutamatergic and GABAergic post-synaptic currents which were strongly shown to be of host origin. Neuroepithelial stem cells are therefore an attractive candidate as a source of donor material for intracerebral grafting in functional repair.