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Epithelial and mesenchymal cell types are basic for animal multicellularity and they have complementary functions coordinated by cellular interactions. Sponges are especially important model organisms to address the evolutionary basis of morphogenetic programs for epithelial and mesenchymal organization in animals. Evolutionary studies in sponges can contribute to the understanding of the mechanisms that control tissue maintenance and tumor progression in humans. In the present study, sponge mesenchymal and epithelial cells were isolated from the demosponge Hymeniacidon heliophila, and aggregate formation was observed by video microscopy. Epithelial-mesenchymal interaction, epithelial transition, and cell migration led to sponge cell aggregation after drastic stress. Based on their different morphologies, adhesion specificities, and motilities, we suggest a role for different sponge cell types as well as complementary functions in cell aggregation. Micromanipulation under the microscope and cell tracking were also used to promote specific grafting-host interaction, to further test the effects of cell type interaction. The loss of cell polarity and flattened shape during the epithelial to mesenchymal cell transition generated small immobile aggregates of round/amoeboid cells. The motility of these transited epithelial-cell aggregates was observed by cell tracking using fluorescent dye, but only after interaction with streams of migratory mesenchymal cells. Cell motility occurred independently of morphological changes, indicating a progressive step in the transition toward a migratory mesenchymal state. Our data suggest a two-step signaling process: (a) the lack of interaction between mesenchymal and epithelial cells triggers morphological changes; and (b) migratory mesenchymal cells instruct epithelial cells for directional cell motility. These results could have an impact on the understanding of evolutionary aspects of metastatic cancer cells. HIGHLIGHTS: Morphogenetic movements observed in modern sponges could have a common evolutionary origin with collective cell migration of human metastatic cells. A sponge regenerative model was used here to characterize epithelial and mesenchymal cells, and for the promotion of grafting/host interactions with subsequent cell tracking. The transition from epithelial to mesenchymal cell type can be observed in sponges in two steps: (a) withdrawal of epithelial/mesenchymal cell interactions to trigger morphological changes; (b) migratory mesenchymal cells to induce epithelial cells to a collective migratory state., (© 2019 Wiley Periodicals, Inc.)

The main characteristic of sponges (Porifera) is the presence of the aquiferous system-a system formed by canals and choanocyte chambers, in which the sponges carry out most of their physiological functions. Despite of the importance for the biology of the group, the knowledge about this structure is still incipient, even when morphological investigations are taken in account. Here, we investigated the anatomy and ultrastructure of the tropical demosponge Cladocroce caelum (Haplosclerida, Demospongiae) using light and electron microscopy. In the studied region, specimens of this species were repent or repent-branched, possessing one to several oscula. A uniform and reduced atrium was found just below each osculum. There was a thin ectosome and the choanosome presented meager mesohyl, but a high number of choanocyte chambers. The choanocyte chambers were rounded, and, as in other haplosclerids, they are found separated from the mesohyl by endopinacocytes, "hanging" in the inhalant canals. Even though the utility of the general organization of the aquiferous system has been advocated as a possible tool to understand the phylogeny of the group, we found that these characters might not be as useful as expected. The size of the particles ingested by the sponge and the amount of bacteria to sustain their bodies are discussed. In addition, we found that the density of choanocyte chambers was reduced when the specimens were carrying out the spermatogenesis, indicating that the reproduction may impair the filtering activity of the sponge. Our findings consist in a first step to better comprehend the physiology, development, and adaptation to the environmental conditions where the species is found., (© 2018 Wiley Periodicals, Inc.)

The metamorphosis of the cinctoblastula of Homoscleromorpha is studied in five species belonging to three genera. The different steps of metamorphosis are similar in all species. The metamorphosis occurs by the invagination and involution of either the anterior epithelium or the posterior epithelium of the larva. During metamorphosis, morphogenetic polymorphism was observed, which has an individual character and does not depend on either external or species specific factors. In the rhagon, the development of the aquiferous system occurs only by epithelial morphogenesis and subsequent differentiation of cells. Mesohylar cells derive from flagellated cells after ingression. The formation of pinacoderm and choanoderm occurs by the differentiation of the larval flagellated epithelium. This is possibly due to the conservation of cell junctions in the external surface of the larval flagellated cells and of the basement membrane in their internal surface. The main difference in homoscleromorph metamorphosis compared with Demospongiae is the persistence of the flagellated epithelium throughout this process and even in the adult since exo- and endopinacoderm remain flagellated. The antero-posterior axis of the larva corresponds to the baso-apical axis of the adult in Homoscleromorpha., (Copyright (c) 2007 Wiley-Liss, Inc.)

The potency of flagellated cells of Halisarca dujardini (Halisarcida, Demospongiae) larvae from the White Sea (Arctic) was investigated experimentally during metamorphosis. Two types of experiments were conducted. First, larvae were maintained in Ca2+ free seawater (CFSW) until the internal cells were released outside through the opening of the posterior pole. These larvae that only composed of flagellated cells (epithelial larvae) were then returned to sea water (SW) to observe their metamorphosis. The posterior aperture closed before they settled on a substratum and started a metamorphosis similar to intact larvae. Secondly, epithelial larvae were, first, further treated in CFSW and then mechanically dissociated. Separated cells or groups of cells were returned to SW, where they constituted large friable conglomerates. After 12-17 h in SW, flagellated cells showed the first steps of dedifferentiation, and regional differentiation was noticeable within conglomerates after approximately 24-36 h. External cells differentiated into pinacocytes while internal cells kept their flagella and became united in a layer. Within 48-72 h, internal cells of the conglomerates formed spherical or ovoid clusters with an internal cavity bearing flagella. These clusters further fused together in a rhagon containing one or two large choanocyte chambers. The sequence of cellular processes in epithelial larvae and in flagellated cell conglomerates was similar. Previous observations indicating the totipotentiality of larval flagellated cells during normal metamorphosis of H. dujardini are thus confirmed., (Copyright (c) 2007 Wiley-Liss, Inc.)

Cell viability is an essential touchstone in the study of the effect of medium components on cell physiology. We developed a flow-cytometric assay to determine sponge-cell viability, based on the combined use of fluorescein diacetate (FDA) and propidium iodide (PI). Cell fluorescence measurements based on incubation of cells with FDA or PI resulted in a useful and reproducible estimate of the viability of primary sponge-cell cultures. We studied the effects of temperature, ammonium, and the fungicide amphotericin B on the viability of a primary-cell culture from the marine sponge Suberites domuncula using the aforementioned flow-cytometric assay. S. domuncula cells die rapidly at a temperature of >or=22 degrees C, but they are insensitive to ammonium concentrations of up to 25 mM. Amphotericin B, which is frequently used in sponge-cell culture media, was found to be toxic to S. domuncula cells., (Copyright 2004 Wiley Periodicals, Inc.)

Marine sponges (Porifera) possess an extraordinary diversity of bioactive metabolites for new drug discovery and development. In vitro cultivation of sponge cells in a bioreactor system is very attractive for the sustainable production of sponge-derived bioactive metabolites; however, it is still a challenging task. The recent establishment of sponge primmorphs, multicellular aggregates from dissociated mixed-cell population (MCP), has been widely acknowledged to hold great promise for cultivation in vitro. Here we present a new method to establish an in vitro sponge primmorph culture from archaeocyte-dominant cell population (ADCP) enriched by a Ficoll gradient, rather than a mixed-cell population (MCP). Our rationale is based upon the totipotency (the ability of a cell to differentiate into other cell types) of archaeocyte cells and the different biological functions of various sponge cell types. A sponge, Hymeniacidon perleve collected from the China Yellow Sea was used as a model system for this investigation. Distinct dynamics of primmorph formation were observed while significant increases in DNA synthesis, cell proliferation (up to threefold), and cell growth (up to fourfold) were achieved. Furthermore, a time-dependent spiculogenesis was clearly demonstrated in our longterm culture, indicating high metabolic activity of primmorphs from the ADCP. This new method represents an important step forward to advance sponge cell culture in vitro that may lead to commercial exploitation of sponge-derived drugs., (Copyright 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 583-590, 2003.)

Freshwater sponges, Corvomeyenia carolinensis Harrison, were placed into tap water to induce degenerative reduction body formation. Reduction bodies were examined using light and electron microscopy in order to define their histochemical and ultrastructural characteristics. The reduction body of freshwater sponges is an extremely simple developmental system consisting primarily of an archeocyte reserve delimited by a simple squamous pinacoderm. The freshwater sponge reduction body displays many similarities to overwintering phases of marine sponges. The system presents an unusually straightforward vehicle for investigations of degeneration and regeneration as processes in developmental biology and may represent a reasonable vehicle in which to examine the process of the genesis of lysosomes.