Stromal induction and specification of morphogenesis and cytodifferentiation of the epithelia of the Mullerian ducts and urogenital sinus during development of the uterus and vagina in mice.

Homotypic and heterotypic recombinations were preapred with trypsin-separated epithelium and stroma from uterus of 1- to 9-day-old and vagina of 2- to 150-day-old mice. Growth of homotypic recombinants in adult female hosts resulted in normal uterine and vaginal morphogenesis. Heterotypic recombinants composed of uterine stroma and vaginal epithelium (VE) usually formed uterus, while recombinants composed of vaginal stroma and uterine epithelium (UE) usually underwent vaginal morphogenesis. The developmental responses of these heterotypic recombinants was age-dependent. Epithelia (UE and VE) from mice two to five-days old were responsive to stromal induction. However, from days 5 to 9 postpartum a progressive loss in competence was observed in both epithelia, and vaginal epithelium nine or more days old was unresponsive to heterotypic inductors. Inductive activities of uterine stroma were demonstrated in 2- to 7-day-old neonates and of vaginal stroma in 2- to 150-day-old mice. These results indicate that establishment of the regional specification of Mullerian and sinus epithelium during uterine and vaginal morphogenesis is due to inductive activities of the stroma.