The mouse pubic symphysis as a remodeling system: morphometrical analysis of proliferation and cell death during pregnancy, partus and postpartum

Abstract

Marked changes in mice pubic symphysis occur by the end of pregnancy. Tissue remodeling involves a dynamic balance between cell proliferation and programmed cell death as well as changes in the extracellular matrix components. Therefore, it is important to consider both of these cellular behaviors when investigating the mechanism that regulates interpubic tissue remodeling, growth during late pregnancy and partus ensuring involution during the postpartum period. Proliferating and programmed death cells were identified by immunohistochemistry (proliferating cell nuclear antigen and TUNEL detection, respectively) and the rates at which these processes occurred were determined by morphometric analysis. The results demonstrated that cellular proliferation was intense during the period of ligament formation, from D15 to D18, thereafter abruptly declining on D19. From parturition (D19) onwards, an ever-increasing decline in the cellular proliferation levels could be observed. The quantitative analyses of cellular death showed opposite results when compared to cellular proliferation. During early pregnancy the cycle of cellular renovation was clearly proliferative and during late mouse pregnancy the cycle was directed by programmed cellular death. Although the high levels of cellular death during postpartum involution could be shown by the TUNEL-positive cells, we were unable to observed picnotic nucleus at the light microscopy.

Changes of Large Molecular Weight Hyaluronan and Versican in the Mouse Pubic Symphysis Through Pregnancy1

“…This modification involves gradual expansion of the dense connective tissue as well as dedifferentiation of chondrocytes to form fibroblasts. These fibroblasts proliferate to produce a symphyseal structure that resembles a true ligament [7]. By Gestation Day (d) 14, the ligament is fully formed.…”

Temporal Changes in Matrix Metalloproteinases, Their Inhibitors, and Cathepsins in Mouse Pubic Symphysis During Pregnancy and Postpartum

“…These modifications in the PS during pregnancy also involve changes in extracellular matrix (ECM) components. 2,3,17,18 Early biochemical studies of PS collagen metabolism detected collagen peptidase in the joint of nonpregnant animals, with the activity of this enzyme being enhanced by hormone administration. Although there is evidence for collagen breakdown in the PS of mouse, 19 little is known about the enzymes involved and the possible temporal changes in their expression and activity during pregnancy and postpartum.…”

Hyaluronan involvement in the changes of mouse interpubic tissue during late pregnancy and post‐partum

“…Furthermore, in the days following parturition there is both a reduction in the length of the interpubic ligament together with low cellular proliferation (Veridiano et al, 2007).…”

“…Nonetheless, from days D19 to 5dpp it is still possible to notice an intracellular staining of HA through histochemical analysis. Furthermore, in the days following parturition there is both a reduction in the length of the interpubic ligament together with low cellular proliferation (Veridiano et al, 2007).…”