FIG. 6.

P3-mediated FGFR3 inhibition slows 9-cisRA-induced tracheal lymphangiogenesis in Prox1-GFP mice. Prox1-GFP mice were treated daily with either vehicle control (ethanol), 9-cisRA, 9-cisRA+scrambled peptide (Sc), or 9-cisRA+peptide P3 (P3) for 7 days. Whole trachea specimens were mounted, and the lymphatics visualized under fluorescent microscopy. Five animals were used in each group. (A) Representative gross photographs of trachea in situ and a harvested trachea before whole mounting. (B) Low (5 × ) and high (10 × ) power representative images of trachea specimens. Lymphatics fluoresce green. High-magnification (10 × ) portions of each low-magnification photograph (5 × ) are shown on the right. White boxes indicate the high-magnification field of view. Vertical white lines indicate the border of tracheal cartilage, past which lymphatic vessels do not normally grow. (C) Total lymphatic vessel length and number of sprouts past the cartilage border. 9-cisRA treated animals demonstrated significantly increased total lymphatic vessel length and number of sprouts compared with vehicle control and 9-cisRA+P3 treated animals. Therefore, P3-mediated FGFR3 inhibition appears to be sufficient to block 9-cisRA-promoted lymphangiogenesis. White arrowheads indicate lymphatic vessels growing past the cartilage border. *Indicates a p-value < 0.05. GFP, green fluorescent protein. Color images are available online.