A new method for in vivo visualization of vessel remodeling using a near-infrared dye.

OBJECTIVES: Vascular obstructive events can be partially compensated for by remodeling processes that increase vessel diameter and collateral tortuosity. However, methods for visualizing remodeling events in vivo and with temporal comparisons from the same animal remain elusive. METHODS: Using a novel infrared conjugated polyethylene glycol dye, we investigated the possibility of intravital vascular imaging of the mouse ear before and after ligation of the primary feeder artery. For comparison, we used two different mouse models known to have impaired vascular remodeling after ligation (i.e., aged and PAI-1(-/-) mice). The results obtained with the infrared dye were confirmed using immunofluorescence labeling of the ear microvasculature with confocal microscopy. RESULTS: After ligation, increases in vessel diameter (between 10% and 60%) and tortuosity (approximately 15%) were observed in C57Bl/6 mice using both the infrared dye and the immunofluorescence technique. However, aged C57Bl/6 and PAI-1(-/-) mice did not show vascular remodeling following ligation. CONCLUSIONS: Vascular remodeling can be visualized and accurately quantified using a new infrared dye in vivo. This analysis technique could be generally employed for quantitative investigations of changes in vascular remodeling.