Reck-immunoreactivity associated with clusters of vascular cells in the mouse implantation chamber. (A) An example of a cluster of cells (red arrow) positive for Reck at a vessel terminus found in the DB. (B) Immunofluorescent double staining of a terminal cell cluster for Reck (green) and PECAM (red; panel 1) or Reck (red) and SMA (green; panel 2) followed by nuclear counter-staining with DAPI (blue). (C) Two adjacent sections stained for Reck (panel 1) and Ki67 (panel 2), respectively. Blue arrows: a bifurcating vessel. Red arrows: a terminal cell cluster. (D) Temporal changes in the number of Reck-positive bifurcating vessels (blue bar) and terminal cell clusters (red bar) per slice from the medial part of implantation chambers. Bar represents mean ± s.e.m., n = 7. The difference between stages is statistically significant (p < 0.05) for both Reck-positive bifurcating vessels and terminal cell clusters. Scale bar: A, 30 μm; B, C, 20 μm.