RESUMO
The use of non-integrating human artificial chromosomes (HACs) in gene therapy possibly allows for safe and reliable genetic modification of human cells without insertional mutagenesis and/or unexpected oncogene activations. Although we previously demonstrated that the HAC provides long-term therapeutic erythropoietin (EPO) production in normal human primary fibroblasts (hPFs), the expression level of EPO was too low to provide medical benefits for human therapy. Thus, the next challenge for the application of this system in therapeutic purposes is to improve the transgene expression on HACs. Here, we newly constructed chromosome 14-based HACs and examined the effects of the telomere and promoter regions on the expression level of the tansgene in hPFs. We showed that the use of natural telomere/sub-telomere and enhancers within the 5' untranslated region of the human ubiquitin C gene greatly increased (over 1000-fold) the EPO production in hPFs. Furthermore, we demonstrated the reprogramming of mouse embryonic fibroblasts by HAC-mediated introduction of four transcription factors, and established induced pluripotent stem cells with no trace of the HACs carrying multiple expression cassettes with large genome fragments. These results indicate that this HAC system could allow us to manipulate multiple transgenes efficiently in human primary cells, providing a promising tool not only for gene therapy but also for investigating genome functions in drug discoveries.
Assuntos
Reprogramação Celular , Cromossomos Artificiais Humanos/genética , Cromossomos Humanos Par 14/genética , Técnicas de Transferência de Genes , Vetores Genéticos , Transgenes , Animais , Linhagem Celular , Elementos Facilitadores Genéticos/genética , Eritropoetina/genética , Fibroblastos , Expressão Gênica , Terapia Genética , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Camundongos , Regiões Promotoras Genéticas/genética , Telômero/genéticaRESUMO
Telomerase-mediated life-span extension enables the expansion of normal cells without malignant transformation, and thus has been thought to be useful in cell therapies. Currently, integrating vectors including the retrovirus are used for human telomerase reverse transcriptase (hTERT)-mediated expansion of normal cells; however, the use of these vectors potentially causes unexpected insertional mutagenesis and/or activation of oncogenes. Here, we established normal human fibroblast (hPF) clones retaining non-integrating human artificial chromosome (HAC) vectors harboring the hTERT expression cassette. In hTERT-HAC/hPF clones, we observed the telomerase activity and the suppression of senescent-associated SA-beta-galactosidase activity. Furthermore, the hTERT-HAC/hPF clones continued growing beyond 120days after cloning, whereas the hPF clones retaining the silent hTERT-HAC senesced within 70days. Thus, hTERT-HAC-mediated episomal expression of hTERT allows the extension of the life-span of human primary cells, implying that gene delivery by non-integrating HAC vectors can be used to control cellular proliferative capacity of primary cultured cells.
Assuntos
Proliferação de Células , Cromossomos Artificiais Humanos/genética , Vetores Genéticos/genética , Telomerase/genética , Animais , Células CHO , Divisão Celular , Senescência Celular , Cricetinae , Cricetulus , Fibroblastos/enzimologia , Fibroblastos/fisiologia , Técnicas de Transferência de Genes , Humanos , Telomerase/análiseRESUMO
Monoclonal antibodies (MoAbs) recognizing lineage- and stage-specific human cell-surface antigens are valuable reagents for the characterization and isolation of various specialized cell populations derived from human embryonic stem cells (hESCs). In this report, we examined the use of in vitro differentiated transchromosomic mouse embryonic stem cells (TC-ESCs) as immunogens to obtain MoAbs against human cell-surface antigens. Immunization of a neural-cell population derived from differentiating human chromosome 4 and 11 TC-ESCs resulted in two chromosome-specific MoAbs, h4-neural1 and h11-neural1, respectively. The staining profiles of differentiated TC-ESCs and human embryonic carcinoma cells with these MoAbs were similar to the expression profile of nestin, a well-characterized intracellular marker for neural progenitor cells. We also described the successful purification and identification of the gene for h4-neural1 antigen (CD133, 4p15.32) with immunoaffinity chromatography. This procedure may have significant utility in generating MoAbs useful for understanding the mechanism that regulates the in vitro differentiation of hESCs.