Human and mouse embryonic stem cells (HESCs and MESCs, respectively) self-renew indefinitely while maintaining the ability to generate all three germ-layer derivatives. Despite the importance of ESCs in developmental biology and their potential impact on tissue replacement therapy, the molecular mechanism underlying ESC self-renewal is poorly understood. Here we show that activation of the canonical Wnt pathway is sufficient to maintain self-renewal of both HESCs and MESCs. Although Stat-3 signaling is involved in MESC self-renewal, stimulation of this pathway does not support self-renewal of HESCs. Instead we find that Wnt pathway activation by 6-bromoindirubin-3'-oxime (BIO), a specific pharmacological inhibitor of glycogen synthase kinase-3 (GSK-3), maintains the undifferentiated phenotype in both types of ESCs and sustains expression of the pluripotent state-specific transcription factors Oct-3/4, Rex-1 and Nanog. Wnt signaling is endogenously activated in undifferentiated MESCs and is downregulated upon differentiation. In addition, BIO-mediated Wnt activation is functionally reversible, as withdrawal of the compound leads to normal multidifferentiation programs in both HESCs and MESCs. These results suggest that the use of GSK-3-specific inhibitors such as BIO may have practical applications in regenerative medicine.

The CA1 pyramidal neurons in the hippocampus are selectively vulnerable to transient ischemic damage. In experimental animals, the CA1 pyramidal neurons undergo cell death several days after brief forebrain ischemia. It remains, however, unknown whether this delayed neuronal death is necrosis or apoptosis. To investigate the degenerating processes of the CA1 pyramidal neurons in gerbil hippocampus after brief ischemia, lysosomal and nuclear alterations in the cells were examined using immunocytochemistry, in situ nick-end labeling, and Southern blotting. By light and electron microscopy, immunoreactivity for cathepsins B, H, and L, representative lysosomal cysteine proteinases, increased in the CA1 pyramidal neurons 3 d after ischemic insult, which showed cell shrinkage. By morphometric analysis, the volume density of cathepsin B-positive lysosomes markedly increased 3 d after ischemic insult, while that of autophagic vacuole-like structures also increased at this stage, suggesting that cathepsin B- immunopositive lysosomes increasing in the neurons after ischemic insult are mostly autolysosomes. Nuclei of the CA1 neurons were nick- end labeled by biotinylated dUTP mediated by terminal deoxytransferase 3 and 4 d after ischemic insult, but not in the prior stages. Simultaneously, dense chromatin masses appeared in nuclei of the neurons. By Southern blotting, laddering of DNA occurred only in CA1 hippocampal tissues obtained 4 d after ischemic insult. Confocal laser scanning microscopy demonstrated that the fragmented DNA in the CA1 pyramidal layer was phagocytosed by microglial cells. The results suggest that delayed death of the CA1 pyramidal neurons after brief ischemia is not necrotic but apoptotic.

The incidence of coronary aneurysm in acute Kawasaki disease was 25%, 55% of which showed regression. During follow-up, ischemic heart disease developed in 4.7% and myocardial infarction in 1.9%. Death occurred in 0.8%.

The molecular mechanism underlying pluripotency is largely unknown. Here, we provide the first global transcriptional profile of the state of "stemness" in human embryonic stem cells (HESCs). We have identified a set of 918 genes enriched in undifferentiated HESCs compared with their differentiated counterparts. These include ligand/receptor pairs and secreted inhibitors of the FGF, TGFbeta/BMP, and Wnt pathways, highlighting a prevalent role for these pathways in HESCs. Importantly, a significant number of HESCs-enriched genes, including several signaling components, are found to be intersected with published mouse embryonic stem cell data, indicating that a "core molecular program" is shared between the two pluripotent stem cells.