Granulated and non-granulated decidual prolactin-related protein-positive decidual cells in the pregnant mouse endometrium

Identification of the cell types responsible for the synthesis of decidual prolactin-related protein (dPRP) in the pregnant mouse endometrium. Histochemistry and immunocytochemistry were used to determine peri-implantation dPRP and perlecan distribution in the mouse uterus. We identified dPRP in pre-decidual and mature decidual cells from days 5 to 12 of pregnancy. On day 8, dPRP immunoreactivity was detected within cytoplasmic granules of a specific population of granulated decidual cells (GDCs). In mesometrial decidual cells, weak immunoreactivity was seen from days 7 to 14. Between days 11 and 14, dPRP was found in cytoplasm and in the extracellular matrix surrounding islands of spongiotrophoblast. Perlecan, a heparan sulfate proteoglycan, was co-localized with dPRP. GDCs are a putative source of dPRP in pregnant mice. Co-localization of perlecan with dPRP suggests that the former acts as a dPRP reservoir and facilitates its paracrine effect in developing placental tissues.