Clinical trials have indicated that autologous hematopoietic stem cell transplantation (HSCT) can persistently suppress inflammatory disease activity in a subset of patients with severe multiple sclerosis (MS), but the mechanism has remained unclear. To understand whether the beneficial effects on the course of disease are mediated by lympho-depletive effects alone or are sustained by a regeneration of the immune repertoire, we examined the long-term immune reconstitution in patients with MS who received HSCT. After numeric recovery of leukocytes, at 2-yr follow-up there was on average a doubling of the frequency of naive CD4+ T cells at the expense of memory T cells. Phenotypic and T cell receptor excision circle (TREC) analysis confirmed a recent thymic origin of the expanded naive T cell subset. Analysis of the T cell receptor repertoire showed the reconstitution of an overall broader clonal diversity and an extensive renewal of clonal specificities compared with pretherapy. These data are the first to demonstrate that long-term suppression of inflammatory activity in MS patients who received HSCT does not depend on persisting lymphopenia and is associated with profound qualitative immunological changes that demonstrate a de novo regeneration of the T cell compartment.

Background-Human herpesvirus-6 (HHV-6), a ubiquitous β-herpesvirus, is the causative agent of roseola infantum and has been associated with a number of neurologic disorders including seizures, encephalitis/meningitis, and multiple sclerosis. Although the role of HHV-6 in human CNS disease remains to be fully defined, a number of studies have suggested that the CNS can be a site for persistent HHV-6 infection.

The mechanisms by which neural and glial progenitor cells in the adult brain respond to tissue injury are unknown. We studied the responses of these cells to stab wound injury in rats and in two transgenic mouse models in which Y/GFP is driven either by Sox2 (a neural stem cell marker) or by Talpha-1 (which marks newly born neurons). The response of neural progenitors was low in all nonneurogenic regions, and no neurogenesis occurred at the injury site. Glial progenitors expressing Olig2 and NG2 showed the greatest response. The appearance of these progenitors preceded the appearance of reactive astrocytes. Surprisingly, we found evidence of the translocation of the transcription factor Olig2 into cytoplasm in the first week after injury, a mechanism that is known to mediate the differentiation of astrocytes during brain development. Translocation of Olig2, down-regulation of NG2, and increased glial fibrillary acidic protein expression were recapitulated in vitro after exposure of glial progenitors to serum components or bone morphogentic protein by up-regulation of Notch-1. The glial differentiation and Olig2 translocation could be blocked by inhibition of Notch-1 with the gamma-secretase inhibitor DAPT. Together, these data indicate that the prompt maturation of numerous Olig2(+) glial progenitors to astrocytes underlies the repair process after a traumatic injury. In contrast, neural stem cells and neuronal progenitor cells appear to play only a minor role in the injured adult CNS.

The uterine endometrium is composed of epithelial and stromal cells, which undergo extensive degeneration and regeneration in every estrous cycle, and dramatic changes occur during pregnancy. The high turnover of cells requires a correspondingly high level of cell division by progenitor cells in the uterus, but the character and source of these cells remain obscure. In the present study, using a novel transgenic mouse, we showed that CD45-positive hematopoietic progenitor cells colonize the uterine epithelium and that in pregnancy more than 80% of the epithelium can derive from these cells. Since we also found green fluorescent protein (GFP)-positive uterine endothelial cells in long-term GFP bone marrow-transplanted mice, we conclude that circulating CD45؉ cells play an important role in regenerating the uterine epithelium. STEM CELLS 2007;25:2820 -2826 Disclosure of potential conflicts of interest is found at the end of this article.

Though first described as a lymphotropic virus, human herpesvirus 6 (HHV-6) is highly neuropathogenic. Two viral variants are known: HHV-6A and HHV-6B. Both variants can infect glial cells and have been differentially associated with central nervous system diseases, suggesting an HHV-6 variant-specific tropism for glial cell subtypes. We have performed infections with both viral variants in human progenitor-derived astrocytes (HPDA) and monitored infected cell cultures for cytopathic effect (CPE), intra-and extracellular viral DNA load, the presence of viral particles by electronic microscopy, mRNA transcription, and viral protein expression. HHV-6A established a productive infection with CPE, visible intracellular virions, and high virus DNA loads. HHV-6B-infected HPDA showed no morphological changes, intracellular viral particles, and decreasing intra-and extracellular viral DNA over time. After long-term passage, HHV-6B-infected HPDA had stable but low levels of intracellular viral DNA load with no detectable viral mRNA. Our results demonstrate that HHV-6A and HHV-6B have differential tropisms and patterns of infection for HPDA in vitro, where HHV-6A results in a productive lytic infection. In contrast, HHV-6B was associated with a nonproductive infection. These findings suggest that HHV-6 variants might be responsible for specific infection patterns in glial cells in vivo. Astrocytes may be an important reservoir for this virus in which differential tropism of HHV-6A and HHV-6B may be associated with different disease outcomes.

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The finding that certain somatic cells can be directly converted into cells of other lineages by the delivery of specific sets of transcription factors paves the way to novel therapeutic applications. Here we show that human cord blood (CB) CD133 + cells lose their hematopoietic signature and are converted into CB-induced neuronal-like cells (CB-iNCs) by the ectopic expression of the transcription factor Sox2, a process that is further augmented by the combination of Sox2 and c-Myc. Gene-expression analysis, immunophenotyping, and electrophysiological analysis show that CBiNCs acquire a distinct neuronal phenotype characterized by the expression of multiple neuronal markers. CB-iNCs show the ability to fire action potentials after in vitro maturation as well as after in vivo transplantation into the mouse hippocampus. This system highlights the potential of CB cells and offers an alternative means to the study of cellular plasticity, possibly in the context of drug screening research and of future cell-replacement therapies.neurons | reprogramming | stem cells T he fate of adult somatic cells is not fixed rigidly and can be reprogrammed by experimental manipulation. The generation of induced pluripotent stem cells (iPSCs) represents the most dramatic evidence that the epigenome of somatic cells are remarkably plastic (1). Recently, it has been reported that fibroblasts can be converted by ectopic expression of defined transcription factors into postmitotic neurons (2-9), neural progenitors (10, 11), and self-renewing neural stem cells (NSCs) (12, 13). However, most reported methods rely on the use of multiple transcription factors and the use of fibroblasts as donor cells.Here we investigate if cord blood (CB) stem cells can be induced to acquire a neuronal phenotype by using only one transcription factor. It has been previously shown that stem cell populations are more amenable to reprogramming than other somatic cells, probably as a result of their preexisting epigenetic state (14,15). Moreover, because of their biological characteristics and availability, CB cells as a donor cell type could offer clear logistic advantages vs. other adult somatic cell types (16,17). These cells can be collected without any risk for the donor and are young cells carrying minimal somatic mutations.Strikingly, we show that forced expression of Sox2 is sufficient to convert CB CD133 + cells into induced neuronal progenitor (NP)-like cells, a conversion process that is augmented by the coexpression of c-Myc. Sox2 is highly expressed in adult NSCs, is one of the earliest functional markers of neuroectodermal specification in the embryo, and plays a key role in the neural lineage specification (18)(19)(20). We show that Sox2-transduced CB cells acquire a distinct neuronal morphology and express multiple neuronal markers in vitro, and that they can be expanded for as many as 25 passages when cultured in permissive condition culture. Moreover, we show that CB-induced neuronal-like cells (CB-iNCs) are able to differentiate in vitro and ...

The cytokine transforming growth factor α (TGFα) has proangiogenic and proneurogenic effects and can potentially reduce infarct volumes. Therefore, we administered TGFα or vehicle directly into the area surrounding the infarct in female mice that received gender-mismatched bone marrow transplants from GFP-expressing males prior to undergoing permanent middle cerebral artery occlusion. Newborn cells were tracked with BrdU labeling and immunohistochemistry at 90 days after stroke onset. We also studied the ingress of bone marrow derived cells into the ischemic brain to determine whether such cells contribute to angiogenesis or neurogenesis. Infarct volumes were measured at 90 days post stroke. The results show that TGFα led to significant increments in the number of newborn neurons and glia in the ischemic hemisphere. TGFα also led to significant increments in the number of bone marrow derived cells entering into the ischemic hemisphere. Most of these cells did not label with BrdU and represented endothelial cells that incorporated into blood vessels in the infarct border zone. Our results also show that infarct size was significantly reduced in animals treated with TGFα compared with controls. These results suggest that TGFα can induce angiogenesis, neurogenesis and neuroprotection after stroke. At least part of the pro-angiogenic effect appears to be secondary to the incorporation of bone marrow derived endothelial cells into blood vessels in the infarct border zone.