Knockdown of Puma protects cord blood CD34(+) cells against γ- irradiation / 中国实验血液学杂志

Puma (P53 upregulated modulator of apoptosis) is a BCL-2 homology 3 (BH3)-only BCL-1 family member and a critical mediator of P53-dependent and -independent apoptosis. Puma plays an essential role in the apoptosis of hematopoietic stem cells exposed to irradiation without an increased risk of malignancies. This study was purposed to develop an effective lentiviral vector to target Puma in human hematopoietic cells and to investigate the effect of Puma gene knockdown on the biological function of human cord blood CD34(+) cells. SF-LV-shPuma-EGFP and control vectors were constructed, and packaged with the pSPAX2/pMD2.G packaging plasmids via 293T cells to produce pseudo-type lentiviruses. SF-LV-shPuma-EGFP or control lentiviruses were harvested within 72 hours after transfection and then were used to transduce human cord blood CD34(+) cells. GFP(+) transduced cells were sorted by flow cytometry (FCM) for subsequent studies. Semi-quantitative real time RT PCR, Western blot, FCM with Annexin V-PE/7-AAD double staining, Ki67 staining, colony forming cell assay (CFC), CCK-8 assay and BrdU incorporation were performed to determine the expression of Puma and its effect on the cord blood CD34(+) cells. The results showed that Puma was significantly knocked down in cord blood CD34(+) cells and the low expression of Puma conferred a radio-protective effect on the cord blood CD34(+) cells. This effect was achieved through reduced apoptosis and sustained quiescence after irradiation due to Puma knockdown. It is concluded that knockdown of puma gene in CD34(+) hematopoietic stem cells of human cord blood possesses the radioprotective effect, maintains the cells in silence targeting Puma in human hematopoietic cells may have a similar effect with that on mouse hematopoietic cells as previously shown, and our lentiviral targeting system for Puma provides a valuable tool for future translational studies with human cells.

An improved method for generating integration-free human induced pluripotent stem cells / 中国实验血液学杂志

The genome instability and tumorigenicity of induced pluripotent stem cells (iPSC) hinder their great potentials for clinical application. Using episomal vectors to generate iPSC is the best way to solve safety issues at present. This method is simple and the exogenous gene was not integrated into the host genome. However, the reprogramming efficiency for this method is very low and thus limits its usage. This study was purposed to improve episomal method for generating induced pluripotent stem cells from cord blood mononuclear cells (CB MNC), to establish integration-free iPSC technology system, and to lay the foundation for individualized iPSC for future clinical uses. To improve the reprogramming efficiency for iPSC, episomal method was used at various combinations of episomal vectors, pre-stimulating culture mediums and oxygen condition were tested to optimize the method. The results showed that using erythroid culture medium for culturing 8 days, transfecting with episomal vectors with SFFV (spleen focus forming virus) promoter under the hypoxic condition (3%), CB MNC could be mostly efficiently reprogrammed with the efficiency 0.12%. Furthermore, the results showed that erythroblasts (CD36(+)CD71(+)CD235a(low)) were the cells that are reprogrammed with high efficiency after culture for 8 days. It is concluded that a highly efficient and safe method for generation of integration-free iPSC is successfully established, which is useable in clinical study.