Faculty of Health and Welfare, Østfold University College, Halden, Norway.
Physiology Unit, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
PLoS One. 2021 Jan 28;16(1):e0245462. doi: 10.1371/journal.pone.0245462. eCollection 2021.
Accumulating evidence indicates that some pituitary cell types are organized in complex networks in both mammals and fish. In this study, we have further investigated the previously described cellular extensions formed by the medaka (Oryzias latipes) luteinizing hormone gonadotropes (Lh cells). Extensions, several cell diameters long, with varicosity-like swellings, were common both in vitro and in vivo. Some extensions approached other Lh cells, while others were in close contact with blood vessels in vivo. Gnrh further stimulated extension development in vitro. Two types of extensions with different characteristics could be distinguished, and were classified as major or minor according to size, origin and cytoskeleton protein dependance. The varicosity-like swellings appeared on the major extensions and were dependent on both microtubules and actin filaments. Immunofluorescence revealed that Lhβ protein was mainly located in these swellings and at the extremity of the extensions. We then investigated whether these extensions contribute to network formation and clustering, by following their development in primary cultures. During the first two days in culture, the Lh cells grew long extensions that with time physically attached to other cells. Successively, tight cell clusters formed as cell somas that were connected via extensions migrated towards each other, while shortening their extensions. Laser photolysis of caged Ca2+ showed that Ca2+ signals originating in the soma propagated from the soma along the major extensions, being particularly visible in each swelling. Moreover, the Ca2+ signal could be transferred between densely clustered cells (sharing soma-soma border), but was not transferred via extensions to the connected cell. In summary, Lh gonadotropes in medaka display a complex cellular structure of hormone-containing extensions that are sensitive to Gnrh, and may be used for clustering and possibly hormone release, but do not seem to contribute to communication between cells themselves.
越来越多的证据表明，一些垂体细胞类型在哺乳动物和鱼类中组织成复杂的网络。在这项研究中，我们进一步研究了先前描述的由斑马鱼（Oryzias latipes）促黄体生成素性腺激素细胞（Lh 细胞）形成的细胞延伸。在体外和体内，都有几个细胞直径长的、具有静脉曲张样肿胀的延伸。一些延伸接近其他 Lh 细胞，而另一些则与体内的血管密切接触。Gnrh 进一步刺激了体外延伸的发育。可以区分出两种具有不同特征的延伸，根据大小、起源和细胞骨架蛋白的依赖性，将它们分为主要延伸和次要延伸。静脉曲张样肿胀出现在主要延伸上，并且依赖于微管和肌动蛋白丝。免疫荧光显示，Lhβ蛋白主要位于这些肿胀处和延伸的末端。然后，我们通过观察其在原代培养中的发育，研究这些延伸是否有助于网络的形成和聚集。在培养的头两天，Lh 细胞生长出长的延伸，随着时间的推移，这些延伸与其他细胞物理连接。随后，由于细胞体通过延伸向彼此迁移并缩短延伸，紧密的细胞簇作为细胞体形成。笼锁 Ca2+的激光光解显示，起源于细胞体的 Ca2+信号沿着主要延伸从细胞体传播，在每个肿胀处特别明显。此外，Ca2+信号可以在密集聚集的细胞（共享细胞体-细胞体边界）之间传递，但不能通过延伸传递到连接的细胞。总之，斑马鱼的 Lh 性腺激素细胞显示出含有激素的延伸的复杂细胞结构，对 Gnrh 敏感，可能用于聚集和可能的激素释放，但似乎不会促进细胞之间的通讯。
