Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 129

The two important characteristics for cells in regenerative medicine therapies are the potential for self-renewal and differentiation. Cells limited in their capacity for self-renewal divide in culture for a finite number of passages. In contrast, cells with unlimited self-renewal may be grown in culture for extended times. Cell differentiation potential can be unipotent, multipotent, or pluripotent. Unipotent cells keep their phenotype. In the bladder, urothelial and bladder smooth-muscle progenitor cells isolated from bladder biopsies are unipotent. Multipotent cells are able to be guided into several phenotypes depending on culture conditions, but the range of possible phenotypic outcomes is more restricted. Bone marrow adipose tissue is a common source of multipotent progenitor cells. These cells can be turned into chondrocytes, adipocytes, or smooth-muscle differentiation pathways. Pluripotent cells have unlimited differentiation potential. Pluripotent cells can become virtually any cell in the body. An example of pluripotent cells are embryonic stem cells. Autologous homologous cells are typically progenitor cells and are usually preferred for regenerative medicine techniques. Sometimes, heterologous cells are used in situations when autologous cells cannot yet be expanded from a particular tissue, such as the pancreas, or are otherwise unavailable for expansion (total-bladder replacements for bladder cancer patients).

Researchers have invested a great deal of time and energy looking into pluripotent stem cells, because of their unlimited self-renewal and plasticity. However, clinical applications remain limited. Pluripotent stem cells are generally allogeneic, and there is a possibility to create immune responses when using them. Furthermore, issues persist with using embryonic stem cells and controlling localization and phenotype for the specific time frames needed for regenerative medicine and tissue-engineering processes. Embryonic stem cells can also form teratomas, which further complicate their implication into clinical procedures. Developers of products using embryonic stem cells will need to address these issues when seeking regulatory approval. Last, many countries have limited or banned clinical use of embryonic cells, because of ethical concerns.

Multiple preclinical studies have demonstrated that bladder implants with progenitor cells elicited superior structure and function when compared with cell-free implants.