Ependymal and Neural Stem Cells of Adult Molly Fish (Poecilia sphenops, Valenciennes, 1846) Brain: Histomorphometry, Immunohistochemical, and Ultrastructural Studies

Abstract

This study was conducted on 16 adult specimens of molly fish (Poecilia sphenops) to investigate ependymal cells (ECs) and their role in neurogenesis using ultrastructural examination and immunohistochemistry. The ECs lined the ventral and lateral surfaces of the optic ventricle and their processes extended through the tectal laminae and ended at the surface of the tectum as a subpial end-foot. Two cell types of ECs were identified: cuboidal non-ciliated (5.68 ± 0.84/100 μm2) and columnar ciliated (EC3.22 ± 0.71/100 μm2). Immunohistochemical analysis revealed two types of GFAP immunoreactive cells: ECs and astrocytes. The ECs showed the expression of IL-1β, APG5, and Nfr2. Moreover, ECs showed immunostaining for myostatin, S100, and SOX9 in their cytoplasmic processes. The proliferative activity of the neighboring stem cells was also distinct. The most interesting finding in this study was the glia–neuron interaction, where the processes of ECs met the progenitor neuronal cells in the ependymal area of the ventricular wall. These cells showed bundles of intermediate filaments in their processes and basal poles and were connected by desmosomes, followed by gap junctions. Many membrane-bounded vesicles could be demonstrated on the surface of the ciliated ECs that contained neurosecretion. The abluminal and lateral cell surfaces of ECs showed pinocytotic activities with many coated vesicles, while their apical cytoplasm contained centrioles. The occurrence of stem cells in close position to the ECs, and the presence of bundles of generating axons in direct contact with these stem cells indicate the role of ECs in neurogenesis. The TEM results revealed the presence of neural stem cells in a close position to the ECs, in addition to the presence of bundles of generating axons in direct contact with these stem cells. The present study indicates the role of ECs in neurogenesis.

Structural and immunohistochemical characterization of pancreas of Molly fish (Poecilia sphenops), with a special reference to its immune role

“…Our previous study revealed the expression of S100 protein in the ependymal cells of Molly fish (Mokhtar, Sayed, et al, 2022). It has been reported that S100 protein is required for the defense systems by many species.…”

“…In addition, the pancreatic acinar cell of intrahepatic pancreas and disseminated pancreas showed immunoreactivity to IL‐1β, NF‐κB, and Nrf2. Our previous studies reported the expression of these proteins in the intestinal bulb, spleen, liver, and ependymal cells of the Molly fish (Hussein et al, 2023, Mokhtar, Hussein, & Sayed, 2022, Mokhtar, Sayed, et al, 2022, Sayed et al, 2022). IL‐1β performs a variety of physiological functions, and fish retain its ability to use IL‐1β to regulate inflammatory process (Secombes et al, 2011), as it has a pivotal role in the local and systemic responses initiation to different stimuli through T and B lymphocytes, natural killer cells, and activating macrophages (Dinarello, 2011).…”

“…Among the striking findings in this study is the expression of SOX9 in the pancreatic acinar cell of intrahepatic pancreas and disseminated pancreas. We previously reported expression of the SOX9 expression in different tissues of Molly fish (Hussein et al, 2023, Mokhtar, Hussein, & Sayed, 2022, Mokhtar, Sayed, et al, 2022, Sayed et al, 2022). SOX9 is a member of the SOX family, which play an important role in the regulatory mechanisms of cell proliferation and cell fate during embryogenesis (Bastide et al, 2007).…”

“…Interestingly, strong immunoreactivity to APG5 and TGF‐β was detected in the pancreatic acinar cells of both hepatopancreas and disseminated pancreas of Molly fish. APG5 and TGF‐β expressions were reported in different tissues of Molly fish (Hussein et al, 2023; Mokhtar, Hussein, & Sayed, 2022; Mokhtar, Sayed, et al, 2022; Sayed et al, 2022). APG5 is one of the principal players in the autophagy process, where it plays a fundamental role in formation of autophagic vesicles, development and proliferation of lymphocyte, differentiation of adipocyte, and apoptosis (Pierdominici et al, 2012).…”

Distribution of the Order Lampriformes in the Mediterranean Sea with Notes on Their Biology, Morphology, and Taxonomy

“…Moreover, the areal distribution of this species seems to be related to the movements of different aquatic masses within the water column [ 54 ]. Despite some cases of pathogenic infections that have been recorded in Lampriformes [ 57 , 67 ], no information in these species about the immune system and its role in organism defense is available [ 68 , 69 , 70 ].…”