Expression of p16INK4a in mouse endometrium and its effect during blastocyst implantation

The expression of tumor suppressor gene p16INK4a in mouse endometrium during early pregnancy and its possible role in blastocyst implantation were investigated in the present study. Real-time fluorescent quantitative PCR (FQ-PCR) and immunohistochemistry were applied to detect p16INK4a mRNA and protein expressions in endometrium of un-pregnant and pregnant mice on day 2, 3, 4, 5, 7, respectively. In addition, p16INK4a antibody was injected into the horns of uteri in pregnant mice on day 3 and its effect during blastocyst implantation was detected in vivo. The higher expressions of p16INK4a mRNA and protein were observed in pregnant mice compared with that in un-pregnant mice, with a steady increase from day 2 to day 5 and reaching the maximal level on day 5 of pregnancy and then decreasing. p16INK4a antibody decreased the number of implanted blastocysts compared with that of saline-injected group. The results suggest that p16INK4a may be associated with apoptosis of luminal epithelial cells and decidual cells, coordinating decidualization of endometrium and invasion of trophoblastic cells. Thus, we presume that p16INK4a participates in the process of blastocyst implantation in mice.