Cytokines in reproductive remodeling of molting White Leghorn hens

The role of cytokines in regression of the ovary and oviduct during induced molting in chickens was investigated by evaluating the expressions of IL-1beta, IL-6, IFN-gamma, IL-2, TGF-beta2, MIP-1beta and IL-8 in the regressing ovary and oviduct by semi-quantitative RT-PCR. In addition, serum hormonal profiles (estrogen, progesterone and corticosterone), along with the gross regression and histological changes of the ovary and oviduct, were investigated. The correlation between expression of cytokines and hormonal changes during the induced molting was also studied. The expression of IL-6, IL-8, MIP-1beta and IFN-gamma mRNAs in the ovary, and IL-1beta, IL-6, IL-8, MIP-1beta, IFN-gamma and TGF-beta2 mRNAs in the oviduct, were up-regulated significantly during induced molting, suggesting their role in tissue regression. However, histological findings suggested no significant increase in immune cells in the regressing oviduct and ovary. Significant up-regulation of TGF-beta2 in the regressing oviduct might have suppressed leukocyte recruitment thereby preventing the inflammatory response and tissue damage. The down-regulation of estrogen and progesterone and up-regulation of corticosterone is well correlated with increased expression of cytokines. It appears that cytokines released during the process of induced molting may have a role in decreasing ovarian steroids and increasing the corticosterone levels in chicken. From this study, it may be concluded that cytokines play a major role in regression of the ovary and oviduct during induced molting in chickens.