Abstract
Calreticulin (CRT), a Ca(2+)-binding storage protein and chaperone in the endoplasmic reticulum, modulates cell adhesiveness and integrin-dependent Ca(2+) signaling. However, the role of CRT during implantation remains poorly understood. In the present study, we characterized the expression of CRT mRNA and the protein in mouse endometria from pregnancy DI to D7. Real-Time PCR and in situ hybridization results showed that the levels of CRT mRNA in the endometria of pregnant mice were significantly higher than those of non-pregnant mice (P<0.05), and increased gradually from pregnancy DI to D4, reaching the máximum level on D4, followed by a plateau from D4 to D7. Using immunofluorescence histochemistry and western blot, changes of CRT expression in the endometria of pregnant mice were consistent with the expression of CRT mRNA. Furthermore, antisense CRT oligodeoxynucleotide was injected into the uterus horns of pregnant mice (D3) to investígate its effect on embryo implantation. The result showed that the number of implanted embryos markedly decreased in the side of uterine horns receiving antisense CRT oligodeoxynucleotide(í(>)<0.05). These findings suggest that CRT may play an important role in embryo implantation in mice.
Highlights
Signals and molecular pathways responsible for endometrial development and receptivity to embryonic implantation are important issues in reproductive biomedicine because of their implication for treatment of infertility and assisted fertilization and implantation (Wang and Dey, 2006)
Our results demonstrated that levels of CRT mRNA and its protein in the endometria of pregnant mice were significantly higher than those of nonpregnant mice, and increased gradually from Day 1of pregnancy (D1) to D7, reaching the maximum level on D4 and D5, followed by maintaining high levels on D6 and D7
The expression of integrins is necessary for the adhesion and invasive capability of blastocyst to endometrium during the implantation window (Lessey et al, 1992; Lessey et at, 1994) and changes in CRT expression in endometrium may regulate integrin function and cell adhesion to facilitate the implantation process (Leung-Hagestei et al, 1994; Fadel et al, 1994; 2001)
Summary
Signals and molecular pathways responsible for endometrial development and receptivity to embryonic implantation are important issues in reproductive biomedicine because of their implication for treatment of infertility and assisted fertilization and implantation (Wang and Dey, 2006). Successful implantation depends on synchronization between the complex molecular and cellular events associated with development and differentiation of the blastocyst, and the receptivity of the endometrium. These events are finely regulated by a series of signals and molecules, including ovarian steroids and cytokines (Krüssel et al, 2003). Coppolino and Papp et al reported that CRT is involved in cell adhesion via the induction of vinculin and N-cadherin expression (Coppolino et al, 1995; Papp et al, 1999).
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