RESUMO
Induced pluripotent stem cells (iPSCs) are considered patient-specific counterparts of embryonic stem cells as they originate from somatic cells after forced expression of pluripotency reprogramming factors Oct4, Sox2, Klf4 and c-Myc. iPSCs offer unprecedented opportunity for personalized cell therapies in regenerative medicine. In recent years, iPSC technology has undergone substantial improvement to overcome slow and inefficient reprogramming protocols, and to ensure clinical-grade iPSCs and their functional derivatives. Recent developments in iPSC technology include better reprogramming methods employing novel delivery systems such as non-integrating viral and non-viral vectors, and characterization of alternative reprogramming factors. Concurrently, small chemical molecules (inhibitors of specific signalling or epigenetic regulators) have become crucial to iPSC reprogramming; they have the ability to replace putative reprogramming factors and boost reprogramming processes. Moreover, common dietary supplements, such as vitamin C and antioxidants, when introduced into reprogramming media, have been found to improve genomic and epigenomic profiles of iPSCs. In this article, we review the most recent advances in the iPSC field and potent application of iPSCs, in terms of cell therapy and tissue engineering.
Assuntos
Diferenciação Celular/genética , Reprogramação Celular/genética , Instabilidade Genômica/genética , Células-Tronco Pluripotentes Induzidas/citologia , Terapia Baseada em Transplante de Células e Tecidos/métodos , Vetores Genéticos/genética , Humanos , Fator 4 Semelhante a Kruppel , Proteínas Proto-Oncogênicas c-myc/genética , Engenharia Tecidual/métodos , Transfecção/métodosRESUMO
Three hundred and seven unselected patients were examined by double contrast barium enemas. Twenty-four patients (7.8%) had carcinomas; 11 patients (3.6%) had polyps; six patients (2%) had possible polyps, not confirmed by colonoscopy; and in four patients (1.3%) the radiological findings were misleading or wrong. No carcinoma was missed by barium enema X-ray examination, to be diagnosed by other means. Two patients had radiological lesions, not demonstrable endoscopically, but confirmed surgically. Extensive follow-up of 286 patients (93.2%) revealed only one subsequent case of carcinoma. The shortcomings of colonoscopy are briefly discussed. It is recommended that barium enema examination precede colonoscopy in the investigation of suspected large bowel neoplasia, and that both be used alternately to screen high-risk patients.