Exosomal miR-135b enhances neovascularization in vivo. (A) Representative light microscopic photographs of Matrigel plugs harvested 1 week after subcutaneous injection into nude mice. The exosomes derived from RPMI8226, RPMI8226-HR/control, RPMI8226-HR/anti-miR135b, or phosphate-buffered saline (as a vehicle control) were mixed with growth factor–reduced Matrigel. (B) The neovasculature induced by the exosome of RPMI8226-HR cells in Matrigel was visualized by immunohistochemical staining of frozen sections with anti-mouse CD31 antibody. Representative photographs reveal abundant vasculature positively stained for CD31 (red). Nuclear counterstaining was performed using DAPI (blue). The scale bar indicates 200 µm. (C) Quantitative data for the neovessels lined in Matrigel plugs determined by pixel density. The exosome derived from RPMI8226-HR cells increased the density of vasculature positive for CD31 in Matrigel plugs compared with vehicle control (*P < .01 vs control, Student t test). The HR exosome–induced increase of neoangiogenesis was canceled by anti–miR-135b disrupting the activity of exosomal miR-135b (RPMI8226-HR/con-exo vs RPMI8226-HR/anti-miR135b-exo; ^#P < .05, Student t test). Values are mean ± SD. exo, exosome; con, control.