Fig. 2.

The localization of calpain 2 and paxillin in cumulus cells of COC during cumulus expansion in vivo. A, Cross-sections of mouse COC were stained with antibodies to visualize either calpain 2 (red) or paxillin (green) at 0 and 8 h after hCG (scale bars, 20 μm). Circle with white line shows the localization of the oocyte. B, High-magnification views of cumulus cells immunostained for calpain 2 (red) and paxillin (green) corresponding to the ones shown in A; a and b, double immunostaining of calpain 2 and paxillin in cumulus cells from eCG-injected mice (hCG 0 h) (scale bars, 5 μm); c and d, calpain 2 and paxillin colocalize to cell-cell adhesion sites (white arrowheads) in cumulus cells at 8 h after hCG injection (scale bars, 5 μm); e and f, calpain 2 and paxillin colocalize to specific sites at the base of cell surface protrusions (white arrowheads) but not on the surface of protrusion (blue arrowheads) in cumulus cells at 8 h after hCG injection (scale bars, 3 μm). C, The localization of α-actin in cumulus cells of COC recovered from mice at 8 h after hCG injection. Immunofluorescent images localize α-actin (green) and nuclei [4′,6-diamidino-2-phenylindole (DAPI); blue]. α-actin is accumulated within protrusions (white arrowheads). D, The percentage of detached cumulus cells in COC, five COC in each section (section number is five, total 25 COC) were used for this analysis. *, The number of detached cells was significantly higher in COC recovered from mice 8 h after hCG injection as compared with that in control COC at 0 h hCG (P < 0.01). Values are mean ± sem of three replicates. E, The number of cumulus cells with protrusions in COC, five COC in each section (section number is five, total 25 COC) were used for this analysis. *, The number of cells with protrusions was significantly higher in COC recovered from mice 8 h after hCG injection as compared with that in COC of hCG 0-h mice (P < 0.01). Values are mean ± sem of three replicates.