Objective: To assess pinopode formation in Lif null and Hoxa10 null mice with infertility secondary to failed implantation.
Design: Controlled animal experiment.
Setting: Animal research and laboratory facility.
Animal(s): Lif null, Hoxa10 null, and ICR mice and Sprague-Dawley rats.
Intervention(s): Endometrial tissue was collected during the peri-implantation period and after ovariectomy.
Main outcome measure(s): Endometrial epithelial tissue was examined under scanning-electron microscopy and assigned a score depending on the number of pinopodes present.
Result(s): Pinopode scores in ICR, Lif null, and Hoxa10 null mice were comparable throughout the peri-implantation period, rising on day 3.5 of pregnancy and remaining elevated through to day 7.5, suggesting that pinopodes are not a good indicator of receptivity in mice. In contrast, pinopode scores in rats clearly demarcated the window of receptivity, appearing on day 4 of pregnancy and declining sharply on day 6. Pinopode scores were low in E(2)-treated ovariectomized mice, but unexpectedly, pinopode scores in vehicle-injected ovariectomized ICR mice were markedly elevated.
Conclusion(s): Lif null and Hoxa10 null mice, in which implantation is impaired, have a similar number of pinopodes to fertile ICR mice. Pinopodes do not define a window of implantation in mice.