Rivera-Torruco Guadalupe, Muench Marcus O, Valle-Rios Ricardo
Cell Therapy Core, Vitalant Research Institute, San Francisco, CA, United States.
Department of Laboratory Medicine, Medical Center, University of California, San Francisco, San Francisco, CA, United States.
Front Hematol. 2024;3. doi: 10.3389/frhem.2024.1371823. Epub 2024 May 28.
Hematopoiesis is a process by which all blood cells are formed. The mechanisms controlling it have been studied for decades. Surprisingly, while hematopoietic stem cells are among the most extensively studied stem cell types, the complete understanding of how they are regulated during development, adulthood, or in non-homeostatic conditions remains elusive. In this review, our primary focus is on research findings that explore where hematopoietic precursors are found in adults outside their primary niches in the bone marrow. This phenomenon is termed extramedullary hematopoiesis (EMH). Early in development hematopoietic stem cells migrate through different regions within and outside the embryo and later the fetus. Although, the primary home for hematopoietic progenitors is the adult bone marrow, it is now recognized that other adult organs may act as hematopoietic progenitor reservoirs both in mice and humans. The first reports about this topic were principally originated from clinical observations, in cases where the bone marrow was malfunctioning, leading to an aberrant hematopoiesis outside the bone marrow. It is worth highlighting that those extramedullary organs, like the small intestine or fat tissue, contain subsets of fully functioning hematopoietic progenitors demonstrated by both and studies. Nonetheless, there are still some unanswered questions regarding the source of these cells, how they differ in function compared to their counterparts in the bone marrow, and the specific roles they play within the tissues where they are located.
造血是一个形成所有血细胞的过程。控制它的机制已经研究了几十年。令人惊讶的是，尽管造血干细胞是研究最为广泛的干细胞类型之一，但对于它们在发育、成年期或非稳态条件下如何受到调控仍未完全理解。在这篇综述中，我们主要关注的是探索在成年人骨髓外主要微环境之外发现造血前体细胞的研究结果。这种现象被称为髓外造血（EMH）。在发育早期，造血干细胞迁移通过胚胎内和胚胎外以及后来胎儿的不同区域。虽然造血祖细胞的主要归宿是成年骨髓，但现在人们认识到，在小鼠和人类中，其他成年器官也可能作为造血祖细胞的储存库。关于这个主题的最初报告主要源于临床观察，即骨髓功能出现故障导致骨髓外异常造血的病例。值得强调的是，像小肠或脂肪组织等那些髓外器官含有功能完全正常的造血祖细胞亚群，这已被……和……研究证实。尽管如此，关于这些细胞的来源、与骨髓中的对应细胞相比其功能有何不同以及它们在所在组织中所起的具体作用，仍然存在一些未解决的问题。
