PROLIFERATION, DIFFERENTIATION AND MORPHOGENESIS OF FETAL-RAT GLANDULAR STOMACH TRANSPLANTED UNDER THE KIDNEY CAPSULE OF SYNGENEIC HOSTS

Undifferentiated glandular stomach tissue fragments from 16.5-day feta l rats were transplanted under the kidney capsule of syngeneic adult r ats, and the proliferation, differentiation and morphogenesis of the t ransplanted tissues were investigated. Gastric epithelial cells began to invaginate 3-4 days after the transplantation and immature glands w ere formed after 1 week. During the period, there was a gradual increa se in the expression of pepsinogen and cathepsin E, markers of cytodif ferentiation of the stomach epithelia, both at protein and mRNA levels . Cathepsin E was weakly expressed in undifferentiated gastric epithel ial cells at 16.5 days of gestation, and a higher level of the express ion was observed in differentiated epithelia of the transplants. In co ntrast, the pepsinogen-producing cells first appeared around days 3-4 after transplantation and gradually increased in number to about 30% o f the epithelial cells and became localized at the bottom of the gland . During the period of the experiment up to 1 month, the pepsinogen-pr oducing cells were all positive for class III mucin and cathepsin E, i ndicating the immature character of these cells. in addition, no parie tal cells were observed. When the tissue fragments were transplanted i nto adrenalectomized animals, the epithelial differentiation and morph ogenesis was suppressed, but its proliferation was enhanced. The obser ved changes were reversed by hydrocortisone replacement. These results suggest that the development of the 16.5-day fetal stomach is regulat ed intrinsically to a certain extent by the genetic program of the cel ls involved and various gastric functions develop in the absence of lu minal stimulation, stage-specific systemic hormonal change, neuronal r egulation or other systemic influences, and that glucocorticoids modul ate the developmental program of the fetal stomach tissues.