No abstract

HDAC activity is essential for maintaining the self-renewal and pluripotency of MSCs.

MicroRNAs have been shown to effectively regulate gene expression at the translational level. Recently, we identified novel microRNAs that were upregulated in a mouse model of spinal cord injury. Among those, we have focused on microRNA 486, which directly represses NeuroD6 expression through a conserved sequence in its untranslated region. We correlated the overexpression of microRNA 486 in motor neurons with a poor outcome due to progressive neurodegeneration and a pathophysiology that is mediated by reactive oxygen species. The expression of microRNA 486 was induced by reactive oxygen species that were produced by inflammatory factors, and reactive oxygen species were accumulated in response to the knockdown of NeuroD6, which enhances the downregulation of glutathione peroxidase 3 and thioredoxin-like 1 after traumatic spinal cord injury. NeuroD6 directly bound to regulatory regions of thioredoxin-like 1 and glutathione peroxidase 3 in motor neurons and activated their expression, which promoted reactive oxygen species scavenging. Moreover, knocking down microRNA 486 induced the expression of NeuroD6, which effectively ameliorated the spinal cord injury and allowed the mice to recover motor function. The infusion of exogenic NeuroD6 in spinal cord injury lesions effectively blocked apoptosis by reactivating thioredoxin-like 1 and glutathione peroxidase 3, which was accompanied by a recovery of motor function. Collectively, these findings have identified a novel microRNA in spinal cord injury lesions called microRNA 486, demonstrating a new role for NeuroD6 in neuroprotection, and suggest a potential therapeutic target for spinal cord injuries.

In this study, we isolated and characterized a population of non-human primate adipose tissue stromal cells (pATSCs) containing multipotent progenitor cells. We show that these pATSCs can differentiate into several mesodermal lineages, as well as neural lineage cells. For neural induction of pATSCs and non-human primate bone marrow stromal cells (pBMSCs), the cells were cultured in Neurobasal (NB) media supplemented with B27, basic fibroblast growth factor (bFGF), brain-derived neurotrophic factor (BDNF) and epidermal growth factor (EGF). After 4 days in culture, the pATSCs form compact, spheroid bodies that ultimately become neurospheres (NS). Free-floating neurospheres undergo extensive differentiation when cultured on PDL-laminin. Our data suggest that the neurogenic potential of pATSCs is markedly higher than that of pBMSCs. We have also performed microarray analysis and characterized the gene expression patterns in undifferentiated pATSCs. The direct comparison of gene expression profiles in undifferentiated pATSCs and pATSC-NS, and delineated specific members of important growth factor, signaling, cell adhesion and transcription factors families. Our data indicate that adipose tissue may be an alternative source of stem cells for therapy of central nervous system (CNS) defects.

Cellular senescence involves a reduction in adult stem cell self-renewal, and epigenetic regulation of gene expression is one of the main underlying mechanisms. Here, we observed that the cellular senescence of human umbilical cord blood-derived multipotent stem cells (hUCB-MSCs) caused by inhibition of histone deacetylase (HDAC) activity leads to down-regulation of high mobility group A2 (HMGA2) and, on the contrary, to up-regulation of p16INK4A, p21CIP1/WAF1 and p27KIP1. We found that let-7a1, let-7d, let-7f1, miR-23a, miR-26a and miR-30a were increased during replicative and HDAC inhibitor-mediated senescence of hUCB-MSCs by microRNA microarray and real-time quantitative PCR. Furthermore, the configurations of chromatins beading on these miRNAs were prone to transcriptional activation during HDAC inhibitor-mediated senescence. We confirmed that miR-23a, miR-26a and miR-30a inhibit HMGA2 to accelerate the progress of senescence. These findings suggest that HDACs may play important roles in cellular senescence by regulating the expression of miRNAs that target HMGA2 through histone modification.Electronic supplementary materialThe online version of this article (doi:10.1007/s00018-010-0457-9) contains supplementary material, which is available to authorized users.