Control (n=3) and GOF β-catenin (n=4) mice were treated with estrogen and progesterone to mimic early pregnancy as described in the Materials and Methods section. pSTAT3 (A,B) and Ki-67 (C–E) expression were assessed by IHC (insets: IgG control for anti-pSTAT3 or anti-Ki-67 antibodies). Expression of epithelial junctional complex factors including Ctnna1 (F; P=0.02) and Cldn1 (G; P=0.05) downstream of pSTAT3 were assessed by qRT-PCR. (H) Endometrial stromal cells were isolated from control and GOF β-catenin mice and treated with estradiol and progesterone for 8 days in vitro to induce decidualization. Prl8a2 expression, a marker of decidualization, was determined by qRT-PCR. Decid, decidualization treatment. Control *P=0.04, GOF β-catenin *P=0.02. All values are means +/− s.e.m. compared by T-test. Images of pSTAT3 and Ki-67 IHC are representative. LE, luminal epithelium; GE, glandular epithelium; ST, stroma; MYO, myometrium.