Following 24 h ex vivo HF organ culture experiments (see methods) we first found, via quantitative immunohistomorphometry, that PGD2 and 15d-PGJ2 both suppressed the number of proliferating K15+ bulge cells (reduced number of both K15+ Ki-67+ and K15+ EdU+ cells in this compartment) following treatment (Fig. 3a–d). Here, PTGDS is linked to hydrops fetalis.