Spinal cord injury (SCI) is a major cause of paralysis. Currently, there are no effective therapies to reverse this disabling condition. The presence of ependymal stem/progenitor cells (epSPCs) in the adult spinal cord suggests that endogenous stem cell-associated mechanisms might be exploited to repair spinal cord lesions. epSPC cells that proliferate after SCI are recruited by the injured zone, and can be modulated by innate and adaptive immune responses. Here we demonstrate that when epSPCs are cultured from rats with a SCI (ependymal stem/progenitor cells injury [epSPCi]), these cells proliferate 10 times faster in vitro than epSPC derived from control animals and display enhanced self renewal. Genetic profile analysis revealed an important influence of inflammation on signaling pathways in epSPCi after injury, including the upregulation of Jak/Stat and mitogen activated protein kinase pathways. Although neurospheres derived from either epSPCs or epSPCi differentiated efficiently to oligodendrocites and functional spinal motoneurons, a better yield of differentiated cells was consistently obtained from epSPCi cultures. Acute transplantation of undifferentiated epSPCi or the resulting oligodendrocyte precursor cells into a rat model of severe spinal cord contusion produced a significant recovery of motor activity 1 week after injury. These transplanted cells migrated long distances from the rostral and caudal regions of the transplant to the neurofilament-labeled axons in and around the lesion zone. Our findings demonstrate that modulation of endogenous epSPCs represents a viable cell-based strategy for restoring neuronal dysfunction in patients with spinal cord damage.

The biology of the ␣ subunits of hypoxia-inducible factors (HIF␣) has expanded from their role in angiogenesis to their current position in the self-renewal and differentiation of stem cells. The results reported in this article show the discovery of FM19G11, a novel chemical entity that inhibits HIF␣ proteins that repress target genes of the two ␣ subunits, in various tumor cell lines as well as in adult and embryonic stem cell models from rodents and humans, respectively. FM19G11 inhibits at nanomolar range the transcriptional and protein expression of Oct4, Sox2, Nanog, and Tgf-␣ undifferentiating factors, in adult rat and human embryonic stem cells, FM19G11 activity occurs in ependymal progenitor stem cells from rats (epSPC), a cell model reported for spinal cord regeneration, which allows the progression of oligodendrocyte cell differentiation in a hypoxic environment, has created interest in its characterization for pharmacological research. Experiments using small interfering RNA showed a significant depletion in Sox2 protein only in the case of HIF2␣ silencing, but not in HIF1␣-mediated ablation. Moreover, chromatin immunoprecipitation data, together with the significant presence of functional hypoxia response element consensus sequences in the promoter region of Sox2, strongly validated that this factor behaves as a target gene of HIF2␣ in epSPCs. FM19G11 causes a reduction of overall histone acetylation with significant repression of p300, a histone acetyltransferase required as a co-factor for HIF-transcription activation. Arrays carried out in the presence and absence of the inhibitor showed the predominant involvement of epigenetic-associated events mediated by the drug.

No abstract

The DNA mismatch repair (MMR) system maintains genomic integrity by correcting replication errors: its malfunction causes genomic instability in several tumor types. Hypoxia-inducible factor-1␣ (HIF1␣), the major regulator of the processes that occur in hypoxia and certain epigenetic events downregulate the expression of MMR genes in cancer cells. However, there is a lack of information regarding MMR regulation and the genetic stability of stem cells under hypoxic conditions. The expression of the MMR system is downregulated in murine and human stem cells cultured in hypoxia, which correlates with lower DNA repair activity in neural stem cells. We observed, through the use of short hairpin loop RNAi expression constructs, that HIF1␣ positively regulated MLH1 and MSH6 when the C17.2 neural stem cells were exposed to short-term hypoxia. However, in prolonged exposure to oxygen depletion, the reduced transcriptional activation of MMR genes was directed by specific epigenetic events. Chromatin immunoprecipitation experiments showed a hypoacetylated/hypermethylated histone H3 and lower SP1 binding within MLH1 and MSH6 adjacent promoter regions. Treatment with the histone deacetylase inhibitor trichostatin A increased histone H3 acetylation and SP1 occupancy and enhanced MMR expression. Sequencing of microsatellite markers revealed genomic instability in the murine and human stem cells grown under hypoxia. Thus, the present article reports, for the first time in the stem cell field, experimental data that indicate that hypoxic niches are an environment in which stem cells might undergo genomic instability, which could lie at the origin of subpopulations with cancer stem cell properties.

Spinal cord injury is a major cause of paralysis with no currently effective therapies. Induction of self-renewal and proliferation of endogenous regenerative machinery with noninvasive and nontoxic therapies could constitute a real hope and an alternative to cell transplantation for spinal cord injury patients. We previously showed that FM19G11 promotes differentiation of adult spinal cord-derived ependymal stem cells under hypoxia. Interestingly, FM19G11 induces self-renewal of these ependymal stem cells grown under normoxia. The analysis of the mechanism of action revealed an early increment of mitochondrial uncoupling protein 1 and 2 with an early drop of ATP, followed by a subsequent compensatory recovery with activated mitochondrial metabolism and the induction of glucose uptake by upregulation of the glucose transporter GLUT-4. Here we show that phosphorylation of AKT and AMP-activated