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Bjørgen H, Brimsholm M, Asserson CF, Skaar K, Knutsen GM, Oaland Ø, Haldorsen R, Fjelldal PG, Hansen T, Rimstad E, Kleist BA, Lund-Iversen M, Kowalewski MP, Koppang EO. Deciphering the pathogenesis of melanized focal changes in the white skeletal muscle of farmed Atlantic salmon (Salmo salar). JOURNAL OF FISH DISEASES 2024:e13988. [PMID: 38943363 DOI: 10.1111/jfd.13988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 06/04/2024] [Accepted: 06/06/2024] [Indexed: 07/01/2024]
Abstract
Melanized focal changes (MFCs) in the fillet of farmed Atlantic salmon is a major quality concern. The changes are thought to initially appear as acute red focal changes (RFCs) that progress into chronic MFCs. Recent findings have indicated that hypoxia may be important in their development, possibly leading to necrosis affecting not only myocytes but also adipocytes. Thus, the aim of this study was to investigate possible hypoxic conditions in RFCs and the subsequent inflammatory responses and lesions in the adipose tissue in RFCs and MFCs. A collection of RFCs, MFCs and control muscle samples from several groups of farmed salmon was studied. Using immunohistochemistry, we found induction of the hypoxia-inducible factor 1 pathway in RFCs. Histological investigations of RFCs and MFCs revealed different stages of fat necrosis, including necrotic adipocytes, a myospherulosis-like reaction and the formation of pseudocystic spaces. Accumulations of foamy macrophages were detected in MFCs, indicating degradation and phagocytosis of lipids. Using in situ hybridization, we showed the presence of tyrosinase- and tyrosinase-related protein-1-expressing amelanotic cells in RFCs, which in turn became melanized in MFCs. In conclusion, we propose a sequence of events leading to the formation of MFCs, highlighting the pivotal role of adiposity, hypoxia and fat necrosis.
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Affiliation(s)
- Håvard Bjørgen
- Unit of Anatomy, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | - Malin Brimsholm
- Unit of Anatomy, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | - Kirstin Skaar
- Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich (UZH), Zurich, Switzerland
| | | | | | | | | | - Tom Hansen
- Matre Research Station, Institute of Marine Research, Matredal, Norway
| | - Espen Rimstad
- Unit of Virology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | | | - Mariusz Pawel Kowalewski
- Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich (UZH), Zurich, Switzerland
| | - Erling Olaf Koppang
- Unit of Anatomy, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
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Jenberie S, van der Wal YA, Jensen I, Jørgensen JB. There and back again? A B cell's tale on responses and spatial distribution in teleosts. FISH & SHELLFISH IMMUNOLOGY 2024; 148:109479. [PMID: 38467322 DOI: 10.1016/j.fsi.2024.109479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 03/04/2024] [Accepted: 03/05/2024] [Indexed: 03/13/2024]
Abstract
Teleost B cells are of special interest due to their evolutionary position and involvement in vaccine-induced adaptive immune responses. While recent progress has revealed uneven distribution of B cell subsets across the various immune sites and that B cells are one of the early responders to infection, substantial knowledge gaps persist regarding their immunophenotypic profile, functional mechanisms, and what factors lead them to occupy different immune niches. This review aims to assess the current understanding of B cell diversity, their spatial distribution in various systemic and peripheral immune sites, how B cell responses initiate, the sites where these responses develop, their trafficking, and the locations where long-term B cell responses take place.
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Affiliation(s)
- Shiferaw Jenberie
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT - the Arctic University of Norway, Tromsø, Norway.
| | | | - Ingvill Jensen
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Jorunn B Jørgensen
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT - the Arctic University of Norway, Tromsø, Norway
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Bjørgen H, Malik S, Rimstad E, Vaadal M, Nyman IB, Koppang EO, Tengs T. Cellular heterogeneity in red and melanized focal muscle changes in farmed Atlantic salmon (Salmo salar) visualized by spatial transcriptomics. Cell Tissue Res 2024; 395:199-210. [PMID: 38087072 PMCID: PMC10837230 DOI: 10.1007/s00441-023-03850-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 11/24/2023] [Indexed: 12/31/2023]
Abstract
Spatial transcriptomics is a technique that provides insight into gene expression profiles in tissue sections while retaining structural information. We have employed this method to study the pathological conditions related to red and melanized focal changes in farmed Atlantic salmon (Salmo salar). Our findings support a model where similar molecular mechanisms are involved in both red and melanized filet discolorations and genes associated with several relevant pathways show distinct expression patterns in both sample types. Interestingly, there appears to be significant cellular heterogeneity in the foci investigated when looking at gene expression patterns. Some of the genes that show differential spatial expression are involved in cellular processes such as hypoxia and immune responses, providing new insight into the nature of muscle melanization in Atlantic salmon.
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Affiliation(s)
- H Bjørgen
- Unit of Anatomy, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 1433, Ås, Norway
| | - S Malik
- Department of Breeding and Genetics, Nofima, 1433, Ås, Norway
| | - E Rimstad
- Unit of Virology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 1433, Ås, Norway
| | - M Vaadal
- Department of Breeding and Genetics, Nofima, 1433, Ås, Norway
| | - I B Nyman
- Unit of Virology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 1433, Ås, Norway
| | - E O Koppang
- Unit of Anatomy, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 1433, Ås, Norway
| | - T Tengs
- Department of Breeding and Genetics, Nofima, 1433, Ås, Norway.
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