Julien Resseguier

• Superio, Joshua Lustracion; Resseguier, Julien Alain Andre; Nobrega, Rafael Henrique; Grebstad, Caroline Maylinn; Fakriadis, Ioannis & Foss, Atle [Vis alle 10 forfattere av denne artikkelen] (2024). Unravelling spermatogenesis in spotted wolffish: Insights from the ultrastructure of juvenile male testes to the cryopreservation of broodstock sperm. Aquaculture. ISSN 0044-8486. 592. doi: 10.1016/j.aquaculture.2024.741214. Fulltekst i vitenarkiv Vis sammendrag

  This study aimed to deepen our understanding of the reproductive biology of male spotted wolffish (Anarhichas minor) using two different experimental approaches involving juvenile and mature broodstock fish. The first approach consisted of a detailed histological examination of the testes to identify the onset of gonadal maturation and characterize the spermatogenic stages in two- and three-year-old juvenile specimens. Light microscopy analysis revealed clear differences between the age groups. Two-year-old fish displayed well-defined interstitial tissue, Sertoli cells, and cysts housing spermatogonia stem cells in which meiosis had not yet begun. In contrast, three-year-old fish exhibited cysts containing spermatocytes, spermatids, and abundant spermatozoa, indicating the initiation of the spermatogenic cycle, albeit with asynchronous puberty. Histochemical staining revealed a significant presence of smooth myoid cells in the interstitial tissue of sexually mature fish. In contrast, electron microscopy further revealed synaptonemal complexes with chromatin differentiation and the appearance of centriolar structures. The second approach focused on optimizing semen freezing and cryopreservation procedures in mature broodstock individuals over the age of 10 years. Seven freezing extenders (KT, TS-2, OP, MT, MH, HBSS, or SR), with seawater (SW) as a control, were assessed along with two cryoprotectants dimethylsulfoxide (DMSO) or methanol to evaluate their impact on pre- and post-thaw semen quality. Results showed that the MT and HBSS extenders were superior in total sperm kinetics at 1:3 dilution and that DMSO showed optimal results in sperm motility and velocity variants. Moreover, the MT and HBSS groups demonstrated consistent sperm viability after cryopreservation, with values similar to fresh samples. Based on the viability results of the SYBR-green-14/PI assay comparing fresh and cryopreserved sperm using MT and HBSS, the MT extender emerged as the most effective freezing medium for cryopreservation of spotted wolffish broodstock sperm. In conclusion, this study provides a comprehensive understanding of the reproductive dynamics of male spotted wolffish, offering valuable insights for both scientific research and aquaculture management.

• Resseguier, Julien Alain Andre; Nguyen-Chi, Mai; Wohlmann, Jens; Rigaudeau, Dimitri; Salinas, Irene & Oehlers, Stefan H. [Vis alle 13 forfattere av denne artikkelen] (2023). Identification of a pharyngeal mucosal lymphoid organ in zebrafish and other teleosts: Tonsils in fish? Science Advances. 9(44), s. 1–18. doi: 10.1126/sciadv.adj0101. Fulltekst i vitenarkiv Vis sammendrag

  The constant exposure of the fish branchial cavity to aquatic pathogens causes local mucosal immune responses to be extremely important for their survival. Here, we used a marker for T lymphocytes/natural killer (NK) cells (ZAP70) and advanced imaging techniques to investigate the lymphoid architecture of the zebrafish branchial cavity. We identified a sub-pharyngeal lymphoid organ, which we tentatively named “Nemausean lymphoid organ” (NELO). NELO is enriched in T/NK cells, plasma/B cells, and antigen-presenting cells embedded in a network of reticulated epithelial cells. The presence of activated T cells and lymphocyte proliferation, but not V(D)J recombination or hematopoiesis, suggests that NELO is a secondary lymphoid organ. In response to infection, NELO displays structural changes including the formation of T/NK cell clusters. NELO and gill lymphoid tissues form a cohesive unit within a large mucosal lymphoid network. Collectively, we reveal an unreported mucosal lymphoid organ reminiscent of mammalian tonsils that evolved in multiple teleost fish families.

• Gerber, Lucie Claire Lola; Resseguier, Julien Alain Andre; Helle-Valle, Tellef; Farhat, Elie; Nilsson, Göran Erik & Nilsson, Sjannie Lefevre (2023). Expression of prolyl hydroxylase domains, the upstream regulators of HIF, in the brain of the anoxia-tolerant crucian carp during anoxia-reoxygenation. American Journal of Physiology. Regulatory Integrative and Comparative Physiology. ISSN 0363-6119. 326(2), s. R184–R195. doi: 10.1152/ajpregu.00211.2023. Fulltekst i vitenarkiv Vis sammendrag

  We report a profound upregulation of most egln paralog mRNA levels in anoxia and upon reoxygenation, with egln3ii showing the largest, a 17-fold increase, and highest relative mRNA abundance. The relative abundance of prolyl hydroxylase domain (PHD) proteins was maintained during anoxia and increased at reoxygenation. PHD immunoreactivity was localized to axonal branches with region-specific changes during anoxia-reoxygenation. These dynamic and regional changes in crucian carp, champion of anoxia tolerance, are most likely adaptive and call for further mechanistic studies.

• Garcia, Benjamin; Dong, Fen; Casadei, Elisa; Resseguier, Julien; Ma, Jie & Cain, Kenneth D. [Vis alle 9 forfattere av denne artikkelen] (2022). A Novel Organized Nasopharynx-Associated Lymphoid Tissue in Teleosts That Expresses Molecular Markers Characteristic of Mammalian Germinal Centers. Journal of Immunology. ISSN 0022-1767. 209(11), s. 2215–2226. doi: 10.4049/jimmunol.2200396. Fulltekst i vitenarkiv
• Dalum, Alf Seljenes; Kraus, Aurora; Khan, Shanawaz; Davydova, Erna; Rigaudeau, Dimitri & Bjørgen, Håvard [Vis alle 13 forfattere av denne artikkelen] (2021). High-Resolution, 3D Imaging of the Zebrafish Gill-Associated Lymphoid Tissue (GIALT) Reveals a Novel Lymphoid Structure, the Amphibranchial Lymphoid Tissue. Frontiers in Immunology. 12. doi: 10.3389/fimmu.2021.769901. Fulltekst i vitenarkiv Vis sammendrag

  The zebrafish is extensively used as an animal model for human and fish diseases. However, our understanding of the structural organization of its immune system remains incomplete, especially the mucosa-associated lymphoid tissues (MALTs). Teleost MALTs are commonly perceived as diffuse and scattered populations of immune cells throughout the mucosa. Yet, structured MALTs have been recently discovered in Atlantic salmon (Salmo salar L.), including the interbranchial lymphoid tissue (ILT) in the gills. The existence of the ILT was only recently identified in zebrafish and other fish species, highlighting the need for in-depth characterizations of the gill-associated lymphoid tissue (GIALT) in teleosts. Here, using 3-D high-resolution microscopy, we analyze the GIALT of adult zebrafish with an immuno-histology approach that reveals the organization of lymphoid tissues via the labeling of T/NK cells with an antibody directed to a highly conserved epitope on the kinase ZAP70. We show that the GIALT in zebrafish is distributed over at least five distinct sub-regions, an organization found in all pairs of gill arches. The GIALT is diffuse in the pharyngeal part of the gill arch, the interbranchial septum and the filaments/ lamellae, and structured in two sub-regions: the ILT, and a newly discovered lymphoid structure located along each side of the gill arch, which we named the Amphibranchial Lymphoid Tissue (ALT). Based on RAG2 expression, neither the ILT nor the ALT constitute additional thymi. The ALT shares several features with the ILT such as presence of abundant lymphoid cells and myeloid cells embedded in a network of reticulated epithelial cells. Further, the ILT and the ALT are also a site for T/NK cell proliferation. Both ILT and ALT show structural changes after infection with Spring Viraemia of Carp Virus (SVCV). Together, these data suggest that ALT and ILT play an active role in immune responses. Comparative studies show that whereas the ILT seems absent in most neoteleosts (“Percomorphs”), the ALT is widely present in cyprinids, salmonids and neoteleosts, suggesting that it constitutes a conserved tissue involved in the protection of teleosts via the gills.

• Resseguier, Julien; Levraud, Jean-Pierre; Dal, Nils-Jørgen Knudsen; Fenaroli, Federico; Primard, Charlotte & Wohlmann, Jens [Vis alle 10 forfattere av denne artikkelen] (2021). Biodistribution of surfactant-free poly(lactic-acid) nanoparticles and uptake by endothelial cells and phagocytes in zebrafish: Evidence for endothelium to macrophage transfer. Journal of Controlled Release. ISSN 0168-3659. 331, s. 228–245. doi: 10.1016/j.jconrel.2021.01.006. Fulltekst i vitenarkiv Vis sammendrag

  In the development of therapeutic nanoparticles (NP), there is a large gap between in vitro testing and in vivo experimentation. Despite its prominence as a model, the mouse shows severe limitations for imaging NP and the cells with which they interact. Recently, the transparent zebrafish larva, which is well suited for high-resolution live-imaging, has emerged as a powerful alternative model to investigate the in vivo behavior of NP. Poly(D,L lactic acid) (PLA) is widely accepted as a safe polymer to prepare therapeutic NP. However, to prevent aggregation, many NP require surfactants, which may have undesirable biological effects. Here, we evaluate ‘safe-by-design’, surfactant-free PLA-NP that were injected intravenously into zebrafish larvae. Interaction of fluorescent NPs with different cell types labelled in reporter animals could be followed in real-time at high resolution; furthermore, by encapsulating colloidal gold into the matrix of PLA-NP we could follow their fate in more detail by electron microscopy, from uptake to degradation. The rapid clearance of fluorescent PLA-NP from the circulation coincided with internalization by endothelial cells lining the whole vasculature and macrophages. After 30 min, when no NP remained in circulation, we observed that macrophages continued to internalize significant amounts of NP. More detailed video-imaging revealed a new mechanism of NP transfer where NP are transmitted along with parts of the cytoplasm from endothelial cells to macrophages.

• Kocere, Agnese; Resseguier, Julien; Wohlmann, Jens; Skjeldal, Frode Miltzow; Khan, Shanawaz & Speth, Martin [Vis alle 14 forfattere av denne artikkelen] (2020). Real-time imaging of polymersome nanoparticles in zebrafish embryos engrafted with melanoma cancer cells: Localization, toxicity and treatment analysis. EBioMedicine. 58, s. 1–12. doi: 10.1016/j.ebiom.2020.102902. Fulltekst i vitenarkiv Vis sammendrag

  Background The developing zebrafish is an emerging tool in nanomedicine, allowing non-invasive live imaging of the whole animal at higher resolution than is possible in the more commonly used mouse models. In addition, several transgenic fish lines are available endowed with selected cell types expressing fluorescent proteins; this allows nanoparticles to be visualized together with host cells. Methods Here, we introduce the zebrafish neural tube as a robust injection site for cancer cells, excellently suited for high resolution imaging. We use light and electron microscopy to evaluate cancer growth and to follow the fate of intravenously injected nanoparticles. Findings Fluorescently labelled mouse melanoma B16 cells, when injected into this structure proliferated rapidly and stimulated angiogenesis of new vessels. In addition, macrophages, but not neutrophils, selectively accumulated in the tumour region. When injected intravenously, nanoparticles made of Cy5-labelled poly(ethylene glycol)-block-poly(2-(diisopropyl amino) ethyl methacrylate) (PEG-PDPA) selectively accumulated in the neural tube cancer region and were seen in individual cancer cells and tumour associated macrophages. Moreover, when doxorubicin was released from PEG-PDPA, in a pH dependant manner, these nanoparticles could strongly reduce toxicity and improve the treatment outcome compared to the free drug in zebrafish xenotransplanted with mouse melanoma B16 or human derived melanoma cells. Interpretation The zebrafish has the potential of becoming an important intermediate step, before the mouse model, for testing nanomedicines against patient-derived cancer cells.

• Dal, Nils-Jørgen Knudsen; Kocere, Agnese; Wohlmann, Jens; Herck, Simon Van; Bauer, Tobias A & Resseguier, Julien [Vis alle 11 forfattere av denne artikkelen] (2020). Zebrafish Embryos Allow Prediction of Nanoparticle Circulation Times in Mice and Facilitate Quantification of Nanoparticle–Cell Interactions. Small. ISSN 1613-6810. 16(5), s. 1–12. doi: 10.1002/smll.201906719. Fulltekst i vitenarkiv Vis sammendrag

  The zebrafish embryo is a vertebrate well suited for visualizing nanoparticles at high resolution in live animals. Its optical transparency and genetic versatility allow noninvasive, real‐time observations of vascular flow of nanoparticles and their interactions with cells throughout the body. As a consequence, this system enables the acquisition of quantitative data that are difficult to obtain in rodents. Until now, a few studies using the zebrafish model have only described semiquantitative results on key nanoparticle parameters. Here, a MACRO dedicated to automated quantitative methods is described for analyzing important parameters of nanoparticle behavior, such as circulation time and interactions with key target cells, macrophages, and endothelial cells. Direct comparison of four nanoparticle (NP) formulations in zebrafish embryos and mice reveals that data obtained in zebrafish can be used to predict NPs' behavior in the mouse model. NPs having long or short blood circulation in rodents behave similarly in the zebrafish embryo, with low circulation times being a consequence of NP uptake into macrophages or endothelial cells. It is proposed that the zebrafish embryo has the potential to become an important intermediate screening system for nanoparticle research to bridge the gap between cell culture studies and preclinical rodent models such as the mouse.

• Resseguier, Julien; Dalum, Alf Seljenes; Pasquier, Louis Du; Zhang, Yaqing; Koppang, Erling Olaf & Boudinot, Pierre [Vis alle 7 forfattere av denne artikkelen] (2020). Lymphoid Tissue in Teleost Gills: Variations on a Theme. Biology (Basel). 9(6). doi: 10.3390/biology9060127. Fulltekst i vitenarkiv Vis sammendrag

  In bony fish, the gill filaments are essential for gas exchanges, but also are vulnerable to infection by water-borne microorganisms. Omnipresent across fish, gill-associated lymphoid tissues (GIALT) regulate interactions with local microbiota and halt infection by pathogens. A special GIALT structure has recently been found in Salmonids, the interbranchial lymphoid tissue (ILT). However, the structural variation of GIALT across bony fish remains largely unknown. Here, we show how this critical zone of interaction evolved across fishes. By labeling a conserved T-cell epitope on tissue sections, we find that several basal groups of teleosts possess typical ILT, while modern teleosts have lymphoepithelium of different shape and size at the base of primary gill filaments. Within Cypriniformes, neither body size variation between two related species, zebrafish and common carp, nor morphotype variation, did have a drastic effect on the structure of ILT. Thereby this study is the first to describe the presence of ILT in zebrafish. The ILT variability across fish orders seems to represent different evolutionary solutions to balancing trade-offs between multiple adaptations of jaws and pharyngeal region, and immune responses. Our data point to a wide structural variation in gill immunity between basal groups and modern teleosts.

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• Superio, Joshua Lustracion; Resseguier, Julien Alain Andre; Nóbrega, Rafael Henrique; Grebstad, Caroline M.; Fakriadis, Ioannis & Foss, Atle [Vis alle 10 forfattere av denne artikkelen] (2024). UNRAVELING SPERMATOGENESIS IN SPOTTED WOLFFISH: INSIGHTS FROM JUVENILE MALE TESTES ULTRASTRUCTURE TO BROODSTOCK SPERM CRYOPRESERVATION. Fulltekst i vitenarkiv
• Gerber, Lucie; Helle-Valle, Tellef; Resseguier, Julien Alain Andre; Torp, May-Kristin; Dahl, Helge Andre & Nilsson, Göran Erik [Vis alle 8 forfattere av denne artikkelen] (2022). Prolyl Hydroxylase Domains in the Anoxia Tolerant Crucian Carp (c. carassius): Insights into the Regulation of the HIF Response to Anoxia-Reoxygenation. Fulltekst i vitenarkiv
• Gerber, Lucie; Helle-Valle, Tellef; Resseguier, Julien Alain Andre; Torp, May-Kristin; Dahl, Helge Andre & Nilsson, Göran Erik [Vis alle 8 forfattere av denne artikkelen] (2022). Prolyl Hydroxylase Domains in the Anoxia Tolerant Crucian Carp (c. carassius): Insights into the Regulation of the HIF Response to Anoxia-Reoxygenation. Fulltekst i vitenarkiv

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