Clinic of Obstetrics and Gynecology, Medical University Hannover, Germany.
Exp Gerontol. 2009 Oct;44(10):634-8. doi: 10.1016/j.exger.2009.07.006. Epub 2009 Jul 26.
Rejuvenation represents a well organized and tightly regulated cellular process in vitro and in vivo, whereby senescent and/or certain differentiated cells revert specific properties acquired during previous steps of maturation to restore again a younger phenotype. Effects of the microenvironment and cellular mechanisms including asymmetric mitosis or retrodifferentiation can contribute to rejuvenation during a dynamic cellular development in contrast to terminally differentiated cells like unicellular organisms, which appear unable to retrodifferentiate and to rejuvenate. The process of rejuvenation is observed in distinct cell populations and includes a coordinated multistep network of transduction cascades with extracellular signaling and cell-to-cell communication to relay intracellular pathways. This provides a certain tissue homeostasis by a regenerative potential and renewal upon tissue-specific repair requirements in addition to residual stem cells, which can vary among different organs and species to extend their life span. However, dysfunctions within a rejuvenation program may also include the risk of neoplastic growth during such a retrograde development. In contrast to rejuvenation in certain cell types, a life span extension - also termed longevity - does not represent a retrograde development but an overall prolonged function of tissues, organs and/or whole organisms. Thus, rejuvenation of a distinct cell population could contribute to longevity of the corresponding organism but may not necessarily be required since longevity could also be achieved mechanistically by inhibition of the mTOR-mediated signaling pathway or by sufficient supply of anti-oxidative defence compounds, physiologically by nutrient restrictions, genetically by the induction of longevity genes or environmentally by the inhibition of aging.
衰老细胞再激活是一个在体外和体内均有组织且受调控的细胞过程，在此过程中，衰老细胞和/或某些已分化细胞会恢复其在成熟过程中获得的某些特性，从而恢复其年轻表型。微环境和细胞机制的影响，包括不对称有丝分裂或去分化，可有助于在动态细胞发育过程中实现衰老细胞再激活，而类似于单细胞生物的终末分化细胞似乎无法去分化和再激活。衰老细胞再激活过程可见于多种细胞群中，包括一个协调的多步骤转导级联网络，涉及细胞外信号和细胞间通讯，以传递细胞内途径。这为特定组织提供了一定的组织内稳态，通过再生潜力和组织特异性修复需求来更新细胞，此外，还存在残余干细胞，这些干细胞在不同器官和物种之间有所差异，可延长其寿命。然而，衰老细胞再激活程序中的功能障碍也可能包括在这种逆行发育过程中发生肿瘤生长的风险。与某些细胞类型的衰老细胞再激活不同，寿命延长——也称为长寿——并不代表逆行发育，而是组织、器官和/或整个生物体的整体延长功能。因此，特定细胞群的衰老细胞再激活可能有助于相应生物体的长寿，但并非必需，因为长寿也可以通过抑制 mTOR 介导的信号通路或通过充分供应抗氧化防御化合物、生理性的营养限制、遗传诱导长寿基因或环境抑制衰老来实现。
