Uterine development and endometrial programming.

Structural patterning and functional programming of uterine tissues are mechanistically coupled. These processes ensure anteroposterior differentiation of uterine tissues from adjacent segments of the developing female reproductive tract (FRT) and radial patterning that establishes uterine-specific histoarchitecture and functionality. Uterine organogenesis begins prenatally and is completed postnatally. Genes required for FRT development include Pax2, Lim1 and Emx2, genes in the abdominal-B Hoxa cluster, and members of both Wnt and Hedgehog (Hh) gene families. Disruption of morphoregulatory gene expression patterns can prevent FRT development entirely or compromise uterine organogenesis specifically. Oestrogen receptor-alpha (ER) -dependent events associated with development of the neonatal porcine uterus can be altered by administration of oestrogen (E) or relaxin (RLX). Expression of the RLX receptor is detectable in porcine endometrium at birth, before onset of ER expression and uterine gland genesis. Uterotrophic effects of both E and RLX can be inhibited with the ER antagonist ICl 182,780, indicating that RLX may act via crosstalk with the ER system in neonatal tissues. Exposure of neonatal gilts to E alters temporospatial patterns of Hh, Wnt and Hoxa expression in the uterine wall. Oestrogen given for two weeks from birth produced hypoplastic adult porcine uteri that were less responsive to periattachment conceptus signals as reflected by reduced growth response and luminal fluid protein accumulation, altered endometrial gene expression, and reduced capacity for conceptus support. Data reinforce the concept that factors affecting signalling events in uterine tissues that produce changes in morphoregulatory gene expression patterns during critical organisational periods can alter the developmental trajectory of the uterus with lasting consequences. Thus, uterine tissues can be programmed epigenetically for success or failure during perinatal life.