OBJECTIVE: Hoxa-10-/- mice have severely compromised fertility from aberrant Dcz. CycD3, G1-phase cell cycle protein involved in stromal cell Dcz, is significantly reduced in Hoxa-10-/- mice. Our objective was to determine whether adenovirus-driven replacement of CycD3 can improve Dcz in Hoxa-10-/- mice both in vitro & in vivo. DESIGN: Experimental study. MATERIALS AND METHODS: Hoxa-10-/- stromal cell culture infected with empty (rAd-GFP) (control) or CycD3 sense (rAd-CycD3) vectors was assessed at 24 and 72h after Dcz conditioned medium treatment by immunostaining & proteomics. Hoxa-10-/- mice treated with rAd-GFP or rAd-CycD3 on d5 were sacrificed on d8 (n¼6, 6), d10 (n¼5, 5) and d12 [n¼5 (rAdCycD3 only)]. Implantation sites (IS) were assessed grossly, and with immunohistochemistry (IHC) & in situ hybridization (ISH). RESULTS: Stromal cell culture infected with rAd-CycD3 had increased proliferation at 24 h & percentage of binucleation at 72 h than rAd-GFP (18.8%1.7 vs. 6.2%1.9, P