Impairment of lymphatic drainage in adult Bmp9-KO mice. (A) Representative fluorescence images of WT and Bmp9-KO hind limbs obtained 3 and 15 minutes after injection of DiD-lipidots. The extremity of the paw was hidden not to saturate the images by the fluorescence signal at the injection site. The black arrowhead outlines lymphatic collectors; the white arrow indicates the popliteal lymph node. The values of the scale bars for fluorescence intensity were adjusted to normalize each image series at comparable values. (B) Quantitative analysis of dye accumulation into the popliteal lymph node. Signal over noise ratio was measured. Values are means ± SE; n = 6 (Bmp9-KO) or n = 9 (WT). *P ≤ .05, significantly different by Mann-Whitney U statistical test.