tailieunhanh - Stem Cells in Endocrinology - part 10

Các loại tế bào gốc cũng có thể ảnh hưởng đến nguy cơ đột biến di truyền. Các ứng cử viên tốt nhất có sẵn như là một nguồn của các tế bào thay thế an toàn, hiệu quả và mở rộng là những tế bào ES. | Chapter 13 Preclinical Trials for Stem Cell Therapy 247 tion clonal selection quality testing and creation of working cell banks for subsequent differentiation under standardized conditions. The type of stem cell may also influence the risk of genetic mutation. The best available candidates as a source of safe effective and expandable replacement cells are ES cells. Most somatic stem cells appear to be telomerase-negative are usually difficult to isolate and senesce within about 50 divisions limiting their expandability. Hematopoietic and mesenchymal stem cells have had limited success in part because of their ability to be easily cloned manipulated and expanded. These are important features that limit the usefulness of somatic stem cells for the development of safe efficacious and cost-effective cell therapies for the millions of patients with chronic degenerative diseases. Whether embryonic or other stem cells are involved screening for genetic stability including karyotyping will be a critical part of the safety evaluation necessary for the implementation of stem cell-based therapies. . Toxicities From Ex Vivo Culturing Transplantation of tissues from a foreign species carries the risk of infectious disease transmission from the donor to the recipient. Use of animal proteins or cells to grow human stem cells effectively transforms the human transplant into a xenotransplant. Of the potential risks most concerning is exposure of the transplant recipient to animal retroviruses such as the porcine endogenous retrovirus PERV 32 . Past experiments have shown that PERV can infect human cell lines in vitro 33 . Recently cross-species infection occurred from the transplantation of PERV-infected pig pancreatic islet cells into NOD SCID nonobese diabetic severe combined immunodeficiency mice 34 . This risk effectively eliminates animal stem cells for therapeutic application and it also greatly limits the use of human stem cells that have been exposed to animal proteins.