BACKGROUND In the intestinal mucosa, numerous cytokines produced by the epithelium, fibroblasts, and immune cells were shown to affect epithelial differentiation and proliferation through epithelial-mesenchymal and epithelial-immune cell interactions. To date, the importance of cytokines in postnatal development of the rat small intestine has not been established.

AIM To investigate the developmental changes in expression of mucosal cytokines in the postnatal maturation of the rat small intestinal epithelium and their regulation by glucocorticoids (GC).

RESULTS TGF-β1, TGF-β2, and IL-1β decreased during the third week of life while levels of TNF-α increased and TGF-α remained constant. In parallel, SI transcripts increased and showed a progressive accumulation in the apical part of the enterocytes first localised at the base of the villi from 18 days onwards. Interestingly, precocious induction of SI mRNA by HC paralleled the decrease in expression of TGF-β isoforms and of IL-1β. All cytokines were expressed in the myofibroblast cell lines. In addition, the results showed that TNF-α was differentially expressed in basal culture conditions and after DX stimulation in jejunal and ileal myofibroblasts. DX decreased IL-1β but not the TGF-β isoforms, similar to that in vivo.

CONCLUSIONS This study shows that mucosal cytokines are developmentally regulated and that GC are potentially involved in this regulation in parallel with maturation of the gut mucosa at weaning.