Transcriptome Profiling of Atlantic Salmon Adherent Head Kidney Leukocytes Reveals That Macrophages Are Selectively Enriched During Culture

Abstract

The Atlantic salmon (Salmo salar) is an economically important fish, both in aquaculture and in the wild. In vertebrates, macrophages are some of the first cell types to respond to pathogen infection and disease. While macrophage biology has been characterized in mammals, less is known in fish. Our previous work identified changes in the morphology, phagocytic ability, and miRNA profile of Atlantic salmon adherent head kidney leukocytes (HKLs) from predominantly “monocyte-like” at Day 1 of in vitro culture to predominantly “macrophage-like” at Day 5 of culture. Therefore, to further characterize these two cell populations, we examined the mRNA transcriptome profile in Day 1 and Day 5 HKLs using a 44K oligonucleotide microarray. Large changes in the transcriptome were revealed, including changes in the expression of macrophage and immune-related transcripts (e.g. csf1r, arg1, tnfa, mx2), lipid-related transcripts (e.g. fasn, dhcr7, fabp6), and transcription factors involved in macrophage differentiation and function (e.g. klf2, klf9, irf7, irf8, stat1). The in silico target prediction analysis of differentially expressed genes (DEGs) using miRNAs known to change expression in Day 5 HKLs, followed by gene pathway enrichment analysis, supported that these miRNAs may be involved in macrophage maturation by targeting specific DEGs. Elucidating how immune cells, such as macrophages, develop and function is a key step in understanding the Atlantic salmon immune system. Overall, the results indicate that, without the addition of exogenous factors, the adherent HKL cell population differentiates in vitro to become macrophage-like.

Experimental Handling Challenges Result in Minor Changes in the Phagocytic Capacity and Transcriptome of Head-Kidney Cells of the Salmonid Fish Coregonus maraena

“…The release of stress hormones initiates a cascade of secondary messengers, which alters the expression of a panel of genes ( 45 , 46 ). These expression patterns also modulate the function of immune cells, including monocytes/macrophages, granulocytes, and lymphocytes, in the head kidney ( 47 – 49 ). For this reason, we investigated the impact of the experimental handling procedure on the transcriptome of the head kidney and the consequences of handling on innate immune functions in maraena whitefish.…”

Self-assembling ferritin nanoplatform for the development of infectious hematopoietic necrosis virus vaccine

“…Zebrafish liver (ZFL) cells (CRL-2643, ATCC) were cultured in DMEM 4.5 g/mL glucose (Gibco) supplemented with 0.01 mg/mL insulin, 50 ng/mL epidermal growth factor, 10% (v/v) heat-inactivated FBS, 5% (v/v) antibiotic/antimycotic, and 0.5% (v/v) heat-inactivated trout serum at 28°C with 5% CO 2 as previously described ( 27 ). Adherent rainbow trout head kidney macrophages (RT-HKM) were isolated from the head kidney as described previously ( 27 , 28 ), and cultured in the same supplemented medium at 15°C with 5% CO 2 . After 24 h, the cells were washed in PBS to remove nonadherent cells, and the media was replaced with fresh culture media and then changed every 48 hours for up to 5 days, which were used for immune gene expression assays.…”

Genome rearrangements, male pregnancy and immunological tolerance – the curious case of the syngnathid immune system

“…These methods are at the forefront of transcriptome research, providing a high-resolution investigative assessment of cell types that transcends traditional bulk-RNA sequencing techniques. Among the fish species that have so far undergone immune cell characterizations or specific cell isolations are zebrafish (Danio rerio) (Dee et al, 2016;Athanasiadis et al, 2017;Carmona et al, 2017;Tang et al, 2017;Hernańdez et al, 2018;Ferrero et al, 2020;Loes et al, 2021), Atlantic cod (Gadus morhua) (Guslund et al, 2020;Guslund et al, 2022), Atlantic salmon (Salmo salar) (Smith et al, 2021), Nile tilapia (Oreochromis niloticus) (Niu et al, 2020;, Mexican tetra (Astyanax mexicanus) (Peuß et al, 2020) and rainbow trout (Oncorhynchus mykiss) (Perdiguero et al, 2021). Recently, the first syngnathid immune cell repertoire was characterized in S. typhle providing a crucial baseline for future immune cell studies within the lineage .…”