Cell proliferation in the process of oviducal tissue remodeling during induced molting in hens

Tissue remodeling and calcium binding protein-D28K (CaBP-D28K) dynamics were examined in the oviduct relative to induced molting. The oviducal tissues of premolting, 7, 10, 13, and 16 d after cessation of laying, and postmolting hens were examined. Frequency of proliferating cells and immunoreactive CaBP-D28K molecules were identified by immunocytochemistry for proliferating cell nuclear antigen (PCNA) and Western blot for CaBP-D28K. The relative frequency of PCNA-positive cells in the mucosal epithelium of the magnum, isthmus, and shell gland was low in premolting and 7 d after the cessation of egg laying. In the magnum and isthmus it was markedly increased in 10 and 13 d after cessation, followed by a slight decrease at 16 d after cessation. The frequency in the shell gland was kept high 10, 13, and 16 d after cessation. The frequency of PCNA-positive cells in each segment was decreased when the birds resumed laying. In the stroma of magnum and isthmus where the tubular glands were located, the frequency of PCNA-positive cells was significantly increased 10 d after the cessation of egg laying relative to premolting and 7 d after cessation. In postmolting hens and in hens 16 d after cessation, the frequency was decreased to a same level to that of premolting hen. In the shell gland, the frequency of PCNA-positive cells was high at 10, 13, and 16 d, and diminished in postmolting hen. Single immunoprecipitate band for CaBP-D28K was observed in the shell gland of premolting, postmolting, and younger hens, whereas the density of bands was greater in postmolting hens and younger hens than in premolting hens. We suggest that the oviducal tissues are remodeled by replacing the old glandular cells with new ones that are derived from the mucosal epithelium and uninvoluted glandular cells. Such rejuvenation of shell gland tissue may lead the improvement of CaBP-D28K induction.