MMP9 expression, fibrin accumulation, and vascularization in implantation sites from galardin-treated wild-type and Plg-deficient mice. (A) At 7.5 dpc in situ hybridization for MMP9 mRNA showed expression in the giant trophoblast cells (black arrows). Few giant trophoblasts were observed in the ectoplacental cone in 7.5 dpc implantation sites from galardin-treated Plg-deficient mice (part d) compared with implantation sites from mock- and galardin-treated wild-type mice and from mock-treated Plg-deficient mice (parts a–c). Fibrin(ogen) was detected by immunohistochemical staining using rabbit anti-fibrin(ogen) (parts e–h). No difference in the fibrin(ogen) staining pattern was observed among implantation sites from the four groups of mice. Endothelial cells were detected by in situ hybridization for PECAM mRNA (parts i–l). A decrease in the vascularization was seen in implantation sites from some galardin-treated Plg-deficient mice (part l), when compared with implantation sites from mock- and galardin-treated wild-type mice and from mock-treated Plg-deficient mice (parts i–k) (see Table 2). The areas boxed in parts i and l are shown at higher magnification in parts m and n, respectively. am, antimesometrial; d, decidua; e, embryo; m, mesometrial. Scale bar: 500 μm in parts a–l; 50 μm in parts m,n. (B) Expression of MMP-9 at 8.5 dpc was detected by in situ hybridization (parts a–d) and was present in the giant trophoblast cells (black arrows) that are identified by their expression of PL-1 mRNA (red arrows) (parts e–h). The spatial distribution of the giant trophoblast cells in 8.5 dpc implantation sites from galardin-treated Plg-deficient mice (part d), was similar to that of mock-treated wild-type mice 7.5 dpc implantation sites (data not shown). Endothelial cells were detected by in situ hybridization for PECAM mRNA (parts i–l). The vascularization of the decidua in 8.5 dpc galardin-treated Plg-deficient mice (parts l,n) was like that found at 7.5 dpc mock-treated wild-type mice (Fig. 3A, parts i,m). The areas boxed in parts i and l are shown at higher magnification in parts m and n, respectively. am, antimesometrial; d, decidua; e, embryo; m, mesometrial. Scale bar: 500 μm in parts a–l; 100 μm in parts m,n.