Fig. 7. Additional details concerning pericyte origin. (A-D) Expression of CD45 by pericytes and macrophages. Sections of 5 day Matrigel plugs were stained for DAPI (blue), CD45 (red), F4/80 (green) and NG2 (magenta). Although many NG2⁺ cells express both CD45 and F4/80, others express only CD45 (arrow) and still others lack both CD45 and F4/80 (arrowheads). All panels represent z-stacks of confocal images. Scale bar: 40 µm. (E-H) Mature Matrigel vessels are derived from immature cellular networks. Five-day Matrigel plugs were transplanted into EGFP⁺ recipients and allowed to continue their vascularization for 14 additional days. Sections were analyzed by staining for NG2 (magenta), CD31 (red) and DAPI (blue). The majority of vessels in the transplanted plugs were negative for EGFP (green), demonstrating that the cellular components of the vessels were already present prior to transplantation. In other vessels such as the one shown here, the EGFP label is absent from NG2⁺ pericytes (arrowheads) and present in some but not all CD31⁺ endothelial cells (arrows). Thus, only a subpopulation of the endothelial cells are recruited subsequent to transplantation. All panels represent z-stacks of confocal images. Scale bar: 40 µm.