100. IN VIVO DIFFERENTIATION OF HUMAN EMBRYONIC STEM CELLS TO UTERINE TISSUE

Abstract

The endometrium undergoes cyclic regeneration. This regeneration has been attributed to adult stem progenitor cells and developmental mechanisms [1, 2]. A better understanding of human endometrial development may shed light on the mechanisms involved in endometrial regeneration and on early origins of adult endometrial disease. The lack of human fetal endometrial tissue has impeded research in early human endometrial development. We hypothesized that directed differentiation of human embryonic stem cells (hESC) to human endometrial tissue by neonatal mouse uterine mesenchyme represents a novel system to study early development of human endometrium. Recent studies have shown that the neonatal mouse uterine mesenchyme is extremely inductive and undergoes reciprocal signalling with human endometrial epithelial cells [3]. Our aim is to establish a xenograft tissue recombination protocol based on a model for human prostate tissue differentiation using hESC [4]. Our method involved formation of embryoid body (EB) with GFP labelled hESC (ENVY) [5] for recombination with 2x0.5mm pieces of epithelial-free uterine mesenchyme from postnatal day 1 mice. Upon fusion in culture, the recombinant tissue is grafted under the kidney capsule of NOD/SCID mice for 4-12 weeks and monitored by in-vivo imaging. Immunohistochemical analysis of recombinant grafts 4 weeks post transplantation (n=4) revealed immature CK8+CK18+Hoxa10+ human epithelial cells surrounded by mouse mesenchymal cells suggesting differentiation of hESC to epithelial cells possibly of endometrial lineage. The ER+PR+SMA+Hoxa10+ mouse mesenchymal cells surrounding human glands differentiated into SMA+ cells possibly via reciprocal signalling from human epithelial cells. At 8 weeks, we found several CK18+/Hoxa10+ human glands co-expressing CA125. These glands are supported by Hoxa10+ human stromal cells. Further experiments are underway to induce the expression of ER and PR in Hoxa10+ epithelial cells which will be crucial in revealing their endometrial lineage.