Relaxation of the mouse pubic symphysis during late pregnancy is not accompanied by the influx of granulocytes.
In some animals, such as mice and guinea pigs, a hormonally controlled mechanism increases the flexibility of the pubic symphysis and enhances the cervical remodeling necessary for safe delivery. Cervical ripening during pregnancy is associated with a paradoxical influx of leukocytes. However, the changes in cell metabolism during relaxation of the mouse pubic symphysis for delivery have not been extensively studied. In this work, we used light microscopy and transmission and scanning electron microcopy, as well as immunohistochemistry and Western blotting for MMP-8, to investigate the involvement of granulocytes or resident stromal cells in the relaxation of the virgin pubic symphysis during late pregnancy (days 18 and 19, before delivery) in vivo and in explanted joints. MMP-8 was studied because this collagenase is a hallmark for cervical ripening associated with the influx of granulocytes during late pregnancy. Extensive dissolution and disorganization of the extracellular matrix was seen around fibroblastic-like cells in late pregnancy. In contrast to the cervix (positive control), morphological and immunohistochemical analyses revealed that there was no characteristic cellular inflammatory response in the interpubic tissue. Staining for MMP-8 was observed in chondroid and fibroblastic-like cells of virgin and relaxed interpubic ligament, respectively. However, no granulocytes were seen during the extensive remodeling of the pubic joint in late pregnancy. These results indicate that constitutive stromal cells may have an important role in tissue relaxation during remodeling of the pubic symphysis in pregnancy.
Department of Histology and Embryology, Institute of Biology, State University of Campinas (UNICAMP), 13083-970 Campinas, São Paulo, Brazil.
Renata Giardini
RG
Rosa
Christiane Aparecida Badin
CA
Tarsitano
Stephen
S
Hyslop
Aureo Tatsumi
AT
Yamada
Olga Maria S
OM
Toledo
Paulo Pinto
PP
Joazeiro
D000818:Animals; D015153:Blotting, Western; D005260:Female; D006098:Granulocytes / Q000648:ultrastructure*; D007150:Immunohistochemistry; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011631:Pubic Symphysis / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure*
D020784:Matrix Metalloproteinase 8