In situ localization and characterization of bone marrow-derived cells in the decidua of normal murine pregnancy.

The study reported here was designed to examine the in situ distribution and characteristics of hemopoietically derived decidual cells during normal pregnancy in mice prenatally reconstituted with bone marrow cells carrying a transgenic marker. Bone marrow cells from a transgenic CD-1 strain (CD-1 beta; carrying 1000 copies of beta-globin genes in tandem) were injected into the yolk sac of Day 17 conventional CD-1 embryos. The pregnant females were allowed to deliver normally, and the female offspring raised to puberty were mated with CD-1 males and then killed on Day 12 of gestation. The extent of chimerism in sections of their spleens, uteri, and other organs was evaluated by in situ hybridization of the sections with a biotinylated cDNA probe specific for the beta-globin genes followed by avidin-biotin-peroxidase staining. Tissue controls were provided by CD-1 beta and CD-1 mice, respectively. Tissues were also processed without the application of the probe or with the application of biotinylated lambda DNA as specificity controls. Reconstituted mice exhibited variable degrees of hemopoietic chimerism as indicated by labeling of their splenic lymphocytes (18-54%; mean 42%) as well as hemopoietic cells in other organs. Variable cellular labeling was also noted in their decidua basalis and metrial glands. Labeled cells in these tissues were identified as typical decidual cells, macrophages, and granulated metrial gland (GMG) cells. Labeling of typical decidual cells varied extensively among implantation sites in the same chimera, the average labeling ranging from 17% to 33% (mean 24%) in various chimeras. Labeling was also noted in GMG cells, lymphocytes, and some decidual cells migrating out of metrial gland explants after 24-h culture. The non-pregnant uterus of a chimeric mouse revealed significant labeling of endometrial stromal cells indicative of their hemopoietic origin. These results revealed a hemopoietic origin of certain typical decidual cells and GMG cells identified in situ during normal murine pregnancy and a hemopoietic origin of certain endometrial stromal cells that may represent precursors of decidual cells. The precise timing of the predecidual stem cell migration from the bone marrow to the uterus remains to be defined.