Department of Comparative Physiology, Uppsala University, Uppsala, Sweden.
Stem Cells Dev. 2012 Nov 20;21(17):3173-86. doi: 10.1089/scd.2012.0077. Epub 2012 Jun 13.
During evolution, the innate and adaptive immune systems were developed to protect organisms from non-self substances. The innate immune system is phylogenetically more ancient and is present in most multicellular organisms, whereas adaptive responses are restricted to vertebrates. Arthropods lack the blood cells of the lymphoid lineage and oxygen-carrying erythrocytes, making them suitable model animals for studying the regulation of the blood cells of the innate immune system. Many crustaceans have a long life span and need to continuously synthesize blood cells, in contrast to many insects. The hematopoietic tissue (HPT) of Pacifastacus leniusculus provides a simple model for studying hematopoiesis, because the tissue can be isolated, and the proliferation of stem cells and their differentiation can be studied both in vivo and in vitro. Here, we demonstrate new findings of a physical link between the HPT and the brain. Actively proliferating cells were localized to an anterior proliferation center (APC) in the anterior part of the tissue near the area linking the HPT to the brain, whereas more differentiated cells were detected in the posterior part. The central areas of HPT expand in response to lipopolysaccharide-induced blood loss. Cells isolated from the APC divide rapidly and form cell clusters in vitro; conversely, the cells from the remaining HPT form monolayers, and they can be induced to differentiate in vitro. Our findings offer an opportunity to learn more about invertebrate hematopoiesis and its connection to the central nervous system, thereby obtaining new information about the evolution of different blood and nerve cell lineages.
在进化过程中，先天免疫系统和适应性免疫系统的发展是为了保护生物体免受非自身物质的侵害。先天免疫系统在进化上更为古老，存在于大多数多细胞生物中，而适应性反应则仅限于脊椎动物。节肢动物缺乏淋巴细胞系的血细胞和携氧红细胞，使它们成为研究先天免疫系统血细胞调节的合适模型动物。许多甲壳类动物的寿命很长，需要不断合成血细胞，这与许多昆虫不同。中华绒螯蟹的造血组织（HPT）为研究造血提供了一个简单的模型，因为可以分离组织，并可以在体内和体外研究干细胞的增殖及其分化。在这里，我们展示了 HPT 与大脑之间存在物理联系的新发现。活跃增殖的细胞定位于组织前部靠近 HPT 与大脑相连区域的前部增殖中心（APC），而更多分化的细胞则位于后部。HPT 的中心区域会因脂多糖诱导的失血而扩张。从 APC 分离出的细胞在体外迅速分裂并形成细胞簇；相反，剩余 HPT 的细胞形成单层，并且可以在体外诱导其分化。我们的发现为了解无脊椎动物造血及其与中枢神经系统的联系提供了机会，从而获得有关不同血液和神经细胞谱系进化的新信息。
