Ectopic epithelial cell clusters in salmonid intestine are associated with inflammation

Abstract

An epizootic incidence of intestinal adenocarcinomas was reported in brood fish of Atlantic salmon (Salmo salar L.) in 2009. The condition was associated with a specific diet inducing enteritis and morphological changes. Here, two field trials of fish up to slaughter size were initiated. In Trial 1, two different feed recipes were used. Feed I was predominantly based on marine ingredients, whereas plant ingredients were limited to soy protein concentrate and wheat. Feed II was lower in fishmeal and without soya protein, which was substituted with plant proteins from other sources. In Trial 2, a commercial feed (Feed III) was included. No macroscopic tumours were observed in 300 fish (Trial 1). At the end of both trials, samples from five different segments of the gastrointestinal tract of a total of 39 fish were investigated with morphological methods. Here, we show the presence of ectopic proliferating epithelial cells only occurring in inflamed intestine and predominantly in the second segment of the mid-intestine. Presence of ectopic epithelial cells in submucosal inflammatory foci may indicate early stages in tumorigenesis, but other possibilities such as proliferative enteric disorders cannot be excluded. Together with inflammation, carcinogenesis should be a focus of investigation in future feed trials.

Dietary inclusion of Antarctic krill meal during the finishing feed period improves health and fillet quality of Atlantic salmon (Salmo salarL.)

“…In addition to liver, dietary krill meal inclusion appeared to improve gut health as ectopic epithelial cells and focal Ca deposits were not observed in KM. Focal accumulation of Ca in necrotic tissue (dystrophic calcification) has previously been observed in intestinal inflammation in Atlantic salmon (62) , and the presence of ectopic epithelial cells in the intestine has been associated with chronic feed-induced gut inflammation associated with plant-based ingredients (63,64) . The level of plant-based ingredients was similar for the FM and KM diets in the present study.…”

Candida utilis yeast as a functional protein source for Atlantic salmon (Salmo salar L.): Local intestinal tissue and plasma proteome responses

“…Currently, in commercial salmon diets, the refined soy product with a reduced level of ANF, soy protein concentrate, is the primary protein source of plant origin [5] and has not been shown to cause pathological changes in the distal intestine (DI) of salmonids after short-term dietary exposure [9]. However, a certain degree of inflammation and ectopic epithelial cells have been observed in the DI of salmonids when fed diets based on FM and soy protein concentrate over a longer period of time [10].…”

Effects of Antarctic Krill Products on Feed Intake, Growth Performance, Fillet Quality, and Health in Salmonids

“…In addition to the effects in the liver, krill PL appeared to reduce inflammation and improve gut health, with no ectopic epithelial cells and focal calcium deposits observed in intestinal tissues in KM-fed salmon in comparison to 15% FM-fed fish that showed both ectopic epithelial cells and focal calcium deposits in intestinal tissues [53]. It is known that focal accumulation of calcium deposits in necrotic tissue is related to intestinal inflammation in Atlantic salmon [78], and the presence of ectopic epithelial cells in the intestine has been associated with chronic feed-induced gut inflammation associated with plant-based ingredients [79,80]. Taken together, KM inclusion is beneficial in lowering liver and intestinal lipids, and it seems that not only the amount of PL but also the source of PL is important in reducing the lipid accumulation in the liver and intestine.…”