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Abstract：
Pluripotent stem cells are defined as cells that can generate cells of lineages from all three germ layers, ectoderm, mesoderm, and endoderm. On the contrary, unipotent and multipotent stem cells develop into one or more cell types respectively, but their differentiation is limited to the cells present in the tissue of origin or, at most, from the same germ layer. Multipotent and unipotent stem cells have been isolated from a variety of adult tissues, Instead, the presence in adult tissues of pluripotent stem cells is a very debated issue. In the early embryos, all cells are pluripotent. In mammalians, after birth, pluripotent cells are maintained in the bone-marrow and possibly in gonads. In fact, pluripotent cells were isolated from marrow aspirates and cord blood and from cultured bone-marrow stromal cells (MSCs). Only in few cases, pluripotent cells were isolated from other tissues. In addition to have the potential to differentiate toward lineages derived from all three germ layers, the isolated pluripotent cells shared other properties, including the expression of cell surface stage specific embryonic antigen (SSEA) and of transcription factors active in the early embryos, but they were variously described and named. However, it is likely that they are part of the same cell population and that observed diversities were the results of different isolation and expansion strategies. Adult pluripotent stem cells are quiescent and self-renew at very low rate. They are maintained in that state under the influence of the \"niche\" inside which they are located. Any tissue damage causes the release in the blood of inflammatory cytokines and molecules that activate the stem cells and their mobilization and homing in the injured tissue. The inflammatory response could also determine the dedifferentiation of mature cells and their reversion to a progenitor stage and at the same time stimulate the progenitors to proliferate and differentiate to replace the damaged cells. In this review we rate articles reporting isolation and characterization of tissue resident pluripotent cells. In the attempt to reconcile observations made by different authors, we propose a unifying picture that could represent a starting point for future experiments.
摘要：
多能干细胞被定义为可以从所有三个胚层产生谱系细胞的细胞，外胚层,中胚层,和内胚层。相反,单能干细胞和多能干细胞分别发育成一种或多种细胞类型，但是它们的分化仅限于起源组织中存在的细胞，最多,来自相同的胚层。多能和单能干细胞已从多种成体组织中分离，相反，多能干细胞在成体组织中的存在是一个非常有争议的问题。在早期胚胎中，所有细胞都是多能的。在哺乳动物中，出生后,多能细胞维持在骨髓和性腺中。事实上,从骨髓抽吸物和脐带血以及培养的骨髓基质细胞(MSCs)中分离多能细胞.只有在少数情况下，从其他组织中分离多能细胞。除了具有向来自所有三个胚层的谱系分化的潜力外，分离的多能细胞共享其他特性，包括细胞表面阶段特异性胚胎抗原（SSEA）和在早期胚胎中活跃的转录因子的表达，但他们有不同的描述和命名。然而,它们很可能是同一细胞群的一部分，观察到的多样性是不同分离和扩增策略的结果。成体多能干细胞以非常低的速率静止和自我更新。它们在它们所在的“利基”的影响下保持在那个状态。任何组织损伤都会导致血液中释放炎性细胞因子和激活干细胞的分子，以及它们在受损组织中的动员和归巢。炎症反应还可以决定成熟细胞的去分化及其向祖细胞阶段的恢复,并且同时刺激祖细胞增殖和分化以替换受损细胞。在这篇综述中，我们对报道组织常驻多能细胞的分离和表征的文章进行了评分。为了调和不同作者的观察，我们提出了一个统一的画面，可以代表未来实验的起点。
