Signaling Role Of Prokineticin2/Prokineticin Receptor2in Female Reproduction System

Objective:To investigate the signaling role of prokineticin2(PK2) and its receptor prokineticin receptor2(PKR2) on female reproduction and the possible underlying mechanism.Methods:The PK2and PKR2gene-targed knockout mice were backcrossed to C57BL6background and the resulted three kinds of hetergeneous mice were used for our research.We observed the mice phenotypes including the bodyweight,the brain weight,and testis or vagina development. Immunofluorescence stain was used for observation of GnRH nerves in the brain and the connections among GnRH nerves,PKR2and ERa.Stages of the estrus cycle were determined by cytologic evaluation of vaginal smears. The lavages were smeared on glass slides, examined microscopically to evaluate the cytologic features. We observed the estrus cycle changes in heterogeneous mice groups.PKR2antagonist(3Cl-MPL) was delivered subcutaneously into C57BL6mice to observe the effect of PK2receptor antagonist on estrus cycle too.LH level was measured by RIA. All murine hormone assays were performed by the Ligand Assay Core of the Specialized Cooperative Center for Research in Reproduction at the University of Virginia (Charlottesville, VA). Results are expressed as the mean±SD. Differences between groups were examined for statistical significance by using ANOVA following with Dunnett’ test, or Student’s t test.Results:We observed the sexually dimorphic expression of PKR2in the preoptic area of hypothalamus. Compared to the male mice, there was more widespread PKR2expression in the preoptic area of the hypothalamus in the female mice. In the preoptic area of hypothalamus, there was significant co-expression of PKR2with ERa. Loss of one copy of PK2or PKR2gene was shown to cause elongated and irregular estrous cycle in the female mice. The alterations in the estrous cycle were more pronounced in PK2and PKR2compound heterozygous mice. Consistent with this observation, administration of a PK2receptor antagonist into female mice led to temporary blocking of estrus cycle at proestrus phase. The administration of PKR2antagonist also blunted the surge of LH level. Taken together, these studies indicate PK2signaling is required for the maintenance of normal female estrus cycle. The signaling role of PK2likely links to the established role of PK2as a suprachiasmatic circadian clock output molecule.