Development of a co-culture model for in vitro toxicological studies in Atlantic salmon

In vitro assays are needed in order to assess the effects on environmental contaminants in animals. In farmed fish, fatty fish species such as the Atlantic salmon are known to accumulate relatively high levels of persistent organic pollutants. Primary cultures consisting of cells isolated directly from a tissue or organ have traditionally been used in toxicological assessments; however, environmentally unrealistic high doses are often required in order to get a response using fish primary cells. It has been suggested that that the sensitivity of in vitro systems can be significantly improved by adding other cell types to the culture. The aim of this study was therefore to develop and test an in vitro co-culture system consisting of Atlantic salmon hepatocytes and monocytes as a potentially more sensitive model than the mono-cultures of hepatocytes used today. Monocytes isolated from blood were cultured together with primary hepatocytes. Dioxins (2,3,7,8,-TCDD and 1,2,3,7,8-PCDD) were selected as model toxicants and RT-qPCR was used to examine if the co-culture system offered improved sensitivity studying the transcription of important biotransformation and xenobiotic genes. Co-cultivating salmon hepatocytes with monocytes altered the response at the gene transcription level for CYP1a, UGT and bcl-x compared to the conventional hepatocyte mono-culture, indicating that co-culture models are promising models that should be evaluated closer for future in vitro toxicological assessments in fishes.