MC-specific deletion of HS.Pdgfrb Cre line specificity detected by ROSA26 eYFP expression (A) and (B) in embryonic skin (n = 2). Colabeling of embryonic hindbrains of Pdgfrb Cre ROSA26 EYFP at E10.5 with isolectin B4 (red, C) revealed PC-specific expression of eYFP (green, C,D); n = 4. Sections of E13.5 embryos were stained with an antibody directed against the HS chain (green), NG2 (red), and 4,6-diamidino-2-phenylindole. Vascular smooth muscle cells (vSMCs) of the dorsal aorta (E,F) have strongly reduced HS deposition with residual HS on the outermost layer of vSMCs in EXT1^MCko embryos (arrow, F). Immunostaining revealed loss of HS in vSMCs and PCs of EXT1^MCko (F,H), whereas HS is strongly expressed in control littermates (E,G) and localized at the abluminal surface of MCs. High magnification imaging of capillaries in the embryonic skin (I-L) showed colocalization of HS and NG2 in control sections (arrows, I.J), whereas NG2-positive cells in EXT1^MCko sections lack HS (arrows, K,L).