Adenovirus-Mediated Antisense Vector-Induced Inhibition of Human Telomerase RNA May Induce Differentiation of CD34+ Cells

BACKGROUND: Background Telomerase activation and human telomerase RNA (hTR) expression are known to be related to the preservation of the "stemness" of stem cells. In this study, we have inhibited the expression of hTR to find the relationship between the telomerase activity and differentiation of normal hematopoietic stem cells. METHODS: We used cord blood collected from 10 full term pregnant women. We classified the CD34+ hematopoietic stem cells from the same donor into three groups: the Ad-OA group was treated with the recombinant adenoviral (Ad) vector Ad-OA using telomerase antisense, the Ad-M6 group was treated with a mutant version of the Ad-OA without telomerase antisense, and a control group without any treatment. RESULTS: The mean number of colony-forming cells (CFCs) were 110+/-38 for the Ad-OA groups, 540+/-56 for the Ad-M6 groups, and 650+/-72 for the control groups. Thus, CFCs in the Ad-OA group were lower than in the Ad-M6 group (P<0.01). The myeloid portion of the CFCs in the Ad-OA group was higher than the Ad-M6 and control groups (P<0.01). The Ad-OA group showed a higher percentage of granulocytes suggesting more of a tendency for myeloid differentiation than the Ad-M6 and control groups (P<0.01). We found that the suppression of telomerase activity by the antisense telomerase adenovirus induced the differentiation of hematopoietic stem cells confirmed by differential cell count and cytochemical staining. CONCLUSION: These findings suggest that the activity of the telomerase may play a role in the differentiation of normal CD34+ hematopoietic stem cells into mature cells.

Manipulation of Human Telomerase Activity in Cancer and Stem Cells: Application of siRNA-induced Inhibition of Human Telomerase RNA (hTR)

BACKGROUND: We have determined the effects of human telomerase RNA inhibiton using siRNA in tumor cells and human embryonic and mesenchymal stem cells. METHODS: We selected the sequences against the predicted loop; these sequneces were comprised of nucleotides from 76 to 94 residues and from 143 to 163 residues as the target sequences, and we cloned these sequences into pU6sh75 and pU6sh143 cells. Three different kinds of cell lines were used: HeLa, SNUhES3, and human mesenchymal stem cells. The degree of inhibition of telomerase activity was assessed by TRAP assay and RT-PCR. RESULTS: The telomerase activity of the HeLa and SNUhES3 cells were 135.3+/-14.5 and 109.0+/-18.2; these cells showed higher activity than human mesenchymal stem cells and Wi38 cells (46.3+/-5.0 and 26.0+/-12.0), which were control cells. When each of the types of cells was treated with siRNA-hTR, the transfection efficiency of pU6sh75 for the HeLa, SNUhES3, and human mesenchymal stem cells was 91.0+/-8.4%, 83.3+/-16.0% and 81.9+/-12.3%, respectively. In the case of pU6sh143, its transfection efficiency was similar to pU6sh75; the HeLa, SNUhES3 and human mesenchymal stem cells tranfection efficiency was 90.1+/-9.0%, 79.9+/-18.2% and 79.4+/-15.1%, respectively. After two days of transfection, the level of telomerase activity in the pU6sh75 transfected cells decreased to 64.3+/-10.1% and 56.0+/-11.0% in the HeLa and SNUhES3 cells, respectively. When the cells were transfected with pU6sh143, the telomerase activity also decreased in the HeLa and SNUhES3 cells (71.3+/-9.1% and 61.6+/-8.3%, respectively). However, the difference of telomerase activity was not significant in the human mesenchymal stem cells: 43.0+/-7.2% with pU6sh75 and 46.0+/-9.0% with pU6sh143. CONCLUSION: Telomerase RNA inhibiton with siRNA may be a feasible way to inhibit the telomerase activity of human tumor and embryonic stem cells.

Hematopoietic Differentiation of Embryoid Bodies Derived from the Human Embryonic Stem Cell Line SNUhES3 in Co-culture with Human Bone Marrow Stromal Cells

Human embryonic stem (ES) cells can be induced to differentiate into hematopoietic precursor cells via two methods: the formation of embryoid bodies (EBs) and co-culture with mouse bone marrow (BM) stromal cells. In this study, the above two methods have been combined by co-culture of human ES-cell-derived EBs with human BM stromal cells. The efficacy of this method was compared with that using EB formation alone. The undifferentiated human ES cell line SNUhES3 was allowed to form EBs for two days, then EBs were induced to differentiate in the presence of a different serum concentration (EB and EB/high FBS group), or co- cultured with human BM stromal cells (EB/BM co-culture group). Flow cytometry and hematopoietic colony-forming assays were used to assess hematopoietic differentiation in the three groups. While no significant increase of CD34+/CD45- or CD34+/CD38- cells was noted in the three groups on days 3 and 5, the percentage of CD34+/CD45- cells and CD34+/ CD38- cells was significantly higher in the EB/BM co-culture group than in the EB and EB/high FBS groups on day 10. The number of colony-forming cells (CFCs) was increased in the EB/BM co-culture group on days 7 and 10, implying a possible role for human BM stromal cells in supporting hematopoietic differentiation from human ES cell-derived EBs. These results demonstrate that co-culture of human ES-cell-derived EBs with human BM stromal cells might lead to more efficient hematopoietic differentiation from human ES cells cultured alone. Further study is warranted to evaluate the underlying mechanism.