Cardiovascular disorders are a growing threat to the survival of salmonids in their natural environment. Alongside pathogens and stressors, acute or chronic toxic exposure to oil spills and nano - and micrometre-sized plastics poses a significant risk to aquatic life. Currently, there are limited studies on cell cultures that can be used to assess exposure to environmental stressors. The objective of this study was to examine the impact of environmental stressors, specifically varying concentrations of crude oil and nanoplastic particles, on heart cells. The toxicity was assessed both in vivo, using larvae of Atlantic salmon, brown trout, and rainbow trout, and in vitro , using heart cell cultures at different developmental stages.
A novel method was used to cultivate cardiac primary cultures of salmonids , which contracted permanently after two to three weeks. The cultures were subsequently treated with either plastics or crude oil. The number of heartbeats in salmonid larvae and contractions in the cultures was recorded , and samples for gene expression analysis were taken. The cultures treated with nanoplastics or crude oil were sampled immediately after exposure and on days 1, 3, 5, and 7 post-exposure. Atlantic salmon s amples were used to measure 10 genes involved in cytokine signalling as well as oxidative stress and pro-inflammatory responses by RT-qPCR.
The heart cell cultures were more sensitive to the effects of environmental stressors than heart in vivo . While the in vivo studies did not show any change in heart rate, the in vitro studies showed a change in the number of contractions after exposure. On gene expression level we could not detect any signs of oxidative stress or inflammation in the heart or in heart cell cultures after the exposure.
Contracting salmonid heart cell cultures can be a valuable tool for monitoring host-environment interactions involving cardiac cells of fish species used in aquaculture.
Acknowledgements : This project was funded by the Federal Ministry of Education and Research in Germany.