Embryo implantation in the anterior chamber of the eye. Effects on uterine allografts and the microvasculature.

A model suitable for the in vivo study of embryo implantation in the presence or absence of uterine tissue has been developed. After transplantation of a uterine allograft to the anterior chamber of rat eyes, embryos were transferred to control, normally cycling, and pseudopregnant recipients. Implantation rates were 86%, 46% and 49%, respectively, for the three groups. Despite embryo growth rates being delayed by 3-4 days, histologic studies showed relatively normal egg cylinder stage embryos equivalent to those of day 8 of normal development. Uterine allografts varied greatly in appearance, from inert-looking pieces of connective tissue to recognizable uterine structures with an epithelium and a degree of decidual response. Reduced implantation rates in the presence of a uterine allograft may be due either to the uterine production of blastotoxic substances or the presence of a chronic inflammatory reaction resulting from the rejection of the allograft by the recipient. This model provides a unique system for continuous, noninvasive in vivo observations of the implantation process.