Figure 4.

Lymphatics on the side of the skull extend along the MMA from the pterygopalatine artery (PPA) towards the top of the skull. (A) Schematic of blood vessels in the dura mater at the side of the skull. The MMA, TS, retroglenoid vein (RGV), and sigmoid sinus (SS) are shown. The purple areas around the MMA are analyzed at different developmental time points as shown in (B–D), and the multiple open arrows in (B–D) indicate the MMA and its branches. (B) At P6, Prox1-GFP-positive/LYVE-1-weak lymphatic vessels (arrows) are distributed along the base of the MMA (open arrows), connecting with the PPA (arrowhead). (C) By P9, Prox1-GFP-positive/LYVE-1-weak lymphatic vessels (arrows) have extended along the MMA and one of its branches towards the top of the skull. (D) At P20, the Prox1-GFP-positive lymphatic vessels (arrows) have extended along several branches of the MMA, and most Prox1-GFP positive lymphatic vessels have enhanced LYVE-1 expression. The lymphatic vessels at the base of the MMA connect with Prox1-GFP/LYVE-1-double positive lymphatics along the PPA, which passes through the base of the skull. The boxed regions in (C) are magnified in (E–H), with staining using different antibodies. (E–F′) At P9, Prox1-GFP-positive lymphatic vessels along the MMA and PPA are labeled by Prox1 antibody staining. Some of the Prox1-GFP-positive vessel area (asterisk) is not stained with Prox1 antibody. (G–H′) At P9, Prox1-GFP-positive lymphatic vessels along the MMA and PPA are also positive for Podoplanin. Scale = 1mm in (B–D) and 100 μm in (E–H′).