APOE and hydrops fetalis: Nevertheless, we found that in C/EBPβCKO/APOE−/− mice, it seems challenging to obtain enough cells from the mouse aorta using the conventional digestion method (collagenase IV or collagenase IV + collagenase I), while Sufficient cells can be obtained when digesting mice with either Control or HF group (Supplementary Fig. 3d).