Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA.
Dev Genes Evol. 2013 Mar;223(1-2):103-15. doi: 10.1007/s00427-012-0428-2. Epub 2013 Jan 15.
Hemocytes (blood cells) are motile cells that move throughout the extracellular space and that exist in all clades of the animal kingdom. Hemocytes play an important role in shaping the extracellular environment and in the immune response. Developmentally, hemocytes are closely related to the epithelial cells lining the vascular system (endothelia) and the body cavity (mesothelia). In vertebrates and insects, common progenitors, called hemangioblasts, give rise to the endothelia and blood cells. In the adult animal, many differentiated hemocytes seem to retain the ability to proliferate; however, in most cases investigated closely, the bulk of hemocyte proliferation takes place in specialized hematopoietic organs. Hematopoietic organs provide an environment where undifferentiated blood stem cells are able to self-renew, and at the same time generate offspring that differentiate into different blood cell types. Hematopoiesis in vertebrates, taking place in the bone marrow, has been subject to intensive research by immunologists and stem cell biologists. Much less is known about blood cell formation in invertebrate animals. In this review, we will survey structural and functional properties of invertebrate hematopoietic organs, with a main focus on insects and other arthropod taxa. We will then discuss similarities, at the molecular and structural level, that are apparent when comparing the development of blood cells in hematopoietic organs of vertebrates and arthropods. Our comparative review is intended to elucidate aspects of the biology of blood stem cells that are more easily missed when focusing on one or a few model species.
血细胞（blood cells）是在整个细胞外空间中移动的运动细胞，存在于动物王国的所有进化枝中。血细胞在塑造细胞外环境和免疫反应中起着重要作用。从发育的角度来看，血细胞与血管系统（内皮细胞）和体腔（间皮细胞）的上皮细胞密切相关。在脊椎动物和昆虫中，称为血球母细胞的共同祖细胞产生内皮细胞和血细胞。在成年动物中，许多分化的血细胞似乎保留了增殖的能力；然而，在大多数密切研究的情况下，大部分血细胞增殖发生在专门的造血器官中。造血器官提供了一个环境，未分化的血液干细胞能够自我更新，同时产生分化为不同血细胞类型的后代。脊椎动物的造血作用发生在骨髓中，免疫学家和干细胞生物学家对其进行了深入研究。关于无脊椎动物血细胞形成的了解要少得多。在这篇综述中，我们将调查无脊椎动物造血器官的结构和功能特性，主要集中在昆虫和其他节肢动物类群上。然后，我们将讨论在比较脊椎动物和节肢动物造血器官中血细胞发育时，在分子和结构水平上明显的相似之处。我们的比较综述旨在阐明在关注一个或几个模式物种时更容易忽略的血液干细胞生物学方面。
