c-Kit-Mediated Functional Positioning of Stem Cells to Their Niches Is Essential for Maintenance and Regeneration of Adult Hematopoiesis

The mechanism by which hematopoietic stem and progenitor cells (HSPCs) through interaction with their niches maintain and reconstitute adult hematopoietic cells is unknown. To functionally and genetically track localization of HSPCs with their niches, we employed novel mutant loxPs, lox66 and lox71 and Cre-recombinase technology to conditionally delete c-Kit in adult mice, while simultaneously enabling GFP expression in the c-Kit-deficient cells. Conditional deletion of c-Kit resulted in hematopoietic failure and splenic atrophy both at steady state and after marrow ablation leading to the demise of the treated adult mice. Within the marrow, the c-Kit-expressing GFP+ cells were positioned to Kit ligand (KL)-expressing niche cells. This c-Kit-mediated cellular adhesion was essential for long-term maintenance and expansion of HSPCs. These results lay the foundation for delivering KL within specific niches to maintain and restore hematopoiesis

Cloning and Construction of Adenovirus Expressing Human Angiopoietin-1 or Vascular Endothelial Growth Factor

Aim: We aimed to clone angiopoietin-1 (Ang1) and vascular endothelial growth factor (VEGF) full-length DNAs of human origin and construct replication-deficient adenovirus encoding for either of these two genes which can be potentially served for clinical applications. Methods: VEGF165 and Ang1 full-length cDNAs of human origin were amplified by RT-PCR, verified by sequencing, cloned into a pShuttle-CMV vector, recombined with a E1 and E3 regions double-deleted adenovirus, packaged in 293A cells, and purified by ultracentrifugation. The titers of Ad-Ang1 and Ad-VEGF165 were determined by a tissue culture infectious dose50 method. Expression of Ang1 and VEGF165 proteins in H9C2 cardiac myoblasts was examined by Western blot. To examine the protective properties of Ad-Ang1 and Ad-VEGF165, DNA fragmentation induced by H2O2 was analyzed in H9C2 cells 24 hours after transfection. Ad-GFP served as a vehicle control. Results: Sequencing analysis indicated that there is one base difference at site 1206 (t) in Ang1 compared with that of GeneBank (c, U83508) although the coded amino acids are the same (Ileucine). VEGF165 cDNA sequence was same as that of GeneBank (AB021221). Western blot showed that protein levels of Ang1 and VEGF165 were increased 3.53 and 11.53 fold respectively 24 h after transfection as compared to control. Examination of DNA fragmentation suggested that Ang1 and/or VEGF165 significantly protected H9C2 cells from H2O2 induced apoptosis. Conclusions: The two constructed adenoviral vectors, Ad-Ang1 and Ad-VEGF165, functionally expressed target proteins. We demonstrated, for the first time, that the combined utilization of Ang1 and VEGF165 inhibited apoptosis, in addition to their angiogenesis properties

Vascular Endothelial Growth Factor and Angiopoietin-1 Protected Cardiac Myoblasts From Apoptosis Induced by H\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e

Aim: To explore the protective effects and involved mechanisms of two angiogenic growth factors, vascular endothelial growth factor (VEGF165) and angiopoietin-1 in cardiac myoblasts. Methods: Replication-deficient adenovirus encoding for human VEGF165 (Ad-VEGF165) or angiopoietin-1 (Ad-Ang1) were transfected into H9C2 cardiac myoblasts. Recombinant adenovirus encoding for green fluorescent protein (Ad-GFP) was used as vehicle control. Twenty-four hours later, cell apoptosis was induced by 300 μmmol of H2O2. Genomic DNA was extracted and DNA fragmentation was analyzed in 1.6% agarose gels. Phosphatidylinositol-3 kinase(PI-3 K) activity and bcl-2 expression level were investigated in H9C2 after gene transfection 24 hours later by an immol/Lunoprecipitated kinase assay and Western blot assay respectively. The effect of wartmannin, a specific inhibitor of PI-3 K, on DNA fragmentation, PI-3 K activity and bcl-2 expression was also analyzed by a pre-treatment of 30 minutes before transfection. Results: Apoptotic DNA fragmentation induced by H2O2 was significantly inhibited by the transfaction of Ad-VEGF165 and/or Ad-Ang1 but then aborted by the pretreatment of wartmannin. PI-3 K activity was significantly elevated after Ad-VEGF165 + Ad-Ang1 transfection as compared to Ad-GFP transfection group(2.60 vs 1.32, P \u3c 0.01). Anti-apoptotic factor bcl-2 expression was upregulated in Ad-VEGF165 (2.1-fold), Ad-Ang1 (1.7-fold) and Ad-VEGF165 + Ad-Ang1 (1.7-fold) treated groups as compared to Ad-GFP transfection group. Wortmannin suppressed PI-3 K activiation induced by Ad-VEGF165 (from 1.83 to 0.69, P \u3c 0.05). Ad-Ang1 (from 1.80 to 0.97, P = 0.07) or Ad-VEGF165a + Ad-Ang1 (from 2.60 to 0.42, P \u3c 0.01). However, upregulation of bcl-2 induced by Ad-VEGF165 and/or Ad-Ang1 was not aborted by wortmannin pretreatment. Conclusions: VEGF165 and/or Ang1 can protect cardiac myoblasts from apoptosis induced by H2O2 throught PI-3 K and bcl-2 pathway. The anti-apoptotic function of either VEGF165 or Ang1 could be served as a now therapeutic target including their angiogenic benefits