Administration Of Exogenous Calcitonin Promotes Implantation Of Blastocyst By Up-regulatingβ3Expression In Endometrial Epithelial Cells

Objective:Implantation failure has been found to be the major reason for unsuccessful outcomes of ART procedures. Calcitonin is produced by uterine epithelia specifically within implantation window, and plays important roles in the implantation process. The objective of this study is to investigate whether exogenous calcitonin could improve the efficiency of implantation by increasing uterine receptivity.Methods:The uterine receptivity of ovariectomized mice was induced by injection of estradiol and progesterone. The expressions of eight implantation-related genes in murine endometrium and RL95-2 cells were analyzed by real-time RT-PCR, Western blot, immunohistochemical analysis, flow cytometry and ELISA respectively. Using an in vitro model of endometrium-trophoblast interaction established with JAR trophoblast and RL95-2 cells, the endometrial receptivity was evaluated by attachment assay and outgrowth assay. The in vivo implantation efficiency was evaluated by embryo transfer test.Results:The i.p. injection of calcitonin increased the expressions of integrinβ3, HB-EGF, and LIF in murine endometrium. The stimulation of RL95-2 cells with calcitonin up-regulated the expression ofβ3 as well asαvβ3 integrin through PKC pathway. The increasedαvβ3 expression resulted in further up-regulation of HB-EGF and LIF in RL95-2 cells in presence of ECM molecules. Treatment of RL95-2 cells with calcitonin promoted the attachment of trophoblast spheroids to EEC monolayer and the expansion of spheroids on the monolayer. Moreover, the i.p. injection of exogenous calcitonin in pre-implantation phase increased the implantation rate of transferred-blastocysts in mice, especially in the individuals with relatively low endometrial receptivity.Conclusions:These data suggest that the administration of exogenous calcitonin in pre-implantation phase could increase the receptivity of endometrium and promote implantation efficiency by modulating endometrial epithelial cells. Our findings may provide a novel approach for improving uterine receptive state in IVF-ET programs, thereby improving pregnancy rates in humans.