Pluripotency associated genes are reactivated by chromatin-modifying agents in neurosphere cells.

Chromatin architecture in stem cells determines the pattern of gene expression and thereby cell identity and fate. The chromatin-modifying agents trichostatin A (TSA) and 5-Aza-2'-deoxycytidine (AzaC) affect histone acetylation and DNA methylation, respectively, and thereby influence chromatin structure and gene expression. In our previous work, we demonstrated that TSA/AzaC treatment of neurosphere cells induces hematopoietic activity in vivo that is long-term, multilineage, and transplantable. Here, we have analyzed the TSA/AzaC-induced changes in gene expression by global gene expression profiling. TSA/AzaC caused both up- and downregulation of genes, without increasing the total number of expressed genes. Chromosome analysis showed no hot spot of TSA/AzaC impact on a particular chromosome or chromosomal region. Hierarchical cluster analysis revealed common gene expression patterns among neurosphere cells treated with TSA/AzaC, embryonic stem (ES) cells, and hematopoietic stem cells. Furthermore, our analysis identified several stem cell genes and pluripotency-associated genes that are induced by TSA/AzaC in neurosphere cells, including Cd34, Cd133, Oct4, Nanog, Klf4, Bex1, and the Dppa family members Dppa2, 3, 4, and 5. Sox2 and c-Myc are constitutively expressed in neurosphere cells. We propose a model in which TSA/AzaC, by removal of epigenetic inhibition, induces the reactivation of several stem cell and pluripotency-associated genes, and their coordinate expression enlarges the differentiation potential of somatic precursor cells.

Impact of different bone marrow cell preparations on left ventricular remodelling after experimental myocardial infarction.

OBJECTIVE: Bone marrow (BM)-derived haematopoietic stem cells have been proposed as a potential cell source to functionally engraft the myocardium and to improve cardiac function after myocardial infarction (MI). However, experimental and clinical data are inconsistent. Since the specific characteristics of different BM cell subsets could influence their therapeutic potential we determined the effect of different BM cell populations on left ventricular remodelling after MI. METHODS AND RESULTS: MI was induced in female mice by coronary artery ligation. Surviving mice were randomised to receive either: total BM, mature Lin(+) or primitive Lin(-) cells from male mice, or saline, via intracardiac injection. Injected cells were detected in the infarct and border zone by PCR for Y-chromosomal sequences. Serial transthoracic echocardiography was performed 1, 21, and 42 days after MI. Over a period of 6 weeks, mortality was not different between the groups. After MI, animals exhibited left ventricular dilatation, as expected. Left ventricular remodelling was not influenced by Lin(+) or Lin(-) BM cells but was partially improved by unfractionated BM cell injection. Paracrine secretion of cytokines (e.g. IL-6, GM-CSF) was differentially regulated in supernatants of cultured BM cells. SUMMARY: Treatment with unfractionated BM cells, but not Lin(+), or Lin(-) cells partially improved cardiac remodelling and function after MI. This may be mediated by paracrine effects.