Monaghan, S. | Search bioRxiv

bioRxiv2024

Characterisation of mesenchymal stromal cells in the skin of Atlantic salmon

BackgroundThe skin serves as the first line of defence for an organism against the external environment. Despite the global significance of salmon in aquaculture, a critical component of this first line of defence, mesenchymal stromal cells, remains unexplored. These pluripotent cells can differentiate into various tissues, including bone, cartilage, tendon, ligament, adipocytes, dermis, muscle and connective tissue within the skin. These cells are pivotal for preserving the integrity of skin tissue throughout an organisms lifespan and actively participate in wound healing processes. ResultsIn this study, we characterise mesenchymal stromal cells in detail for the first time in healthy Atlantic salmon tissue and during the wound healing process. Single-nucleus sequencing and spatial transcriptomics revealed the transcriptional dynamics of these cells, elucidating the differentiation pathways leading to osteogenic and fibroblast lineages in the skin of Atlantic salmon. We charted their activity during an in vivo wound healing time course, showing clear evidence of their active role during this process, as they become transcriptionally more active during the remodelling stage of wound healing. ConclusionsFor the first time, we chart the activity of sub-clusters of differentiating stromal cells during the process of wound healing, revealing different spatial niches of the various MSC subclusters, and setting the stage for investigations into the manipulation of MSCs to improve fish health.

genomics↗

bioRxiv2020

A commercial autogenous injection vaccine protects ballan wrasse (Labrus bergylta, Ascanius) against Aeromonas salmonicida vapA type V

Atypical Aeromonas salmonicida (aAs) and Vibrionaceae related species are bacteria routinely recovered from diseased ballan wrasse used as cleaner fish in Atlantic salmon farming. Autogenous multivalent vaccines formulated from these microorganisms are widely used by the industry to protect farmed wrasse despite limited experimental proof that they are primary pathogens. In this study, the components of a commercial multivalent injection wrasse vaccine were tested for infectivity, pathogenicity and virulence via intra peritoneal injection at pre-deployment size (25-50g) and the efficacy of the vaccine for protection against aAs assessed. Injection with 3.5x109, 8x109 1.8x109 and 5x109 cfu/fish of Vibrio splendidus, V. ichthyoenteri, Aliivibrio logeii and A. salmonicida, respectively, did not cause significant mortalities, lesions or clinical signs after a period of 14 days. IP injection with both aAs and Photobacterium indicum successfully reproduced the clinical signs and internal lesions observed during natural outbreaks of the disease. Differences in virulence (LD50 at day 8-post infection of 3.6x106 cfu/fish and 1.6x107 cfu/fish) were observed for two aAs vapA type V isolates. In addition, the LD50 for Photobacterium indicum was 2.2x107 cfu/fish. The autogenous vaccine was highly protective against the two aAs vapA type V isolates after 700-degree days of immunisation. The RPSFINAL values for the first isolate were 95 and 91% at 1x106 cfu/fish and 1x107 cfu/fish, respectively, and 79% at 1x107 cfu/fish for the second isolate tested. In addition, significantly higher anti aAs seral antibodies (IgM), were detected by ELISA in vaccinated fish in contrast with control (mock vaccinated) fish. These results suggest wrasse can be effectively immunised and protected against aAs infection by injection with oil adjuvanted vaccines prepared with inactivated homologous isolates. Further work should assess the efficacy of vaccination against other isolates that have proven to be pathogenic such as aAs type VI and Photobacterium indicum and explore the feasibility of immersion vaccination. In addition, a full characterisation of aAs isolates within the same vapA types should be performed as differences in virulence between vapA type V isolates were observed and partial genome analysis indicated small but potentially important genomic differences in these isolates.

pathology↗