Abstract 17533: Non-Invasive Dynamic Near-Infrared Fluorescence Imaging of Lymphatics in Animals With Salt-Induced Hypertension
Background: High blood pressure or hypertension is common and a major risk factor for cardiovascular disease. Recent data suggest that the lymphatic system may play an important role in regulation of blood pressure during excessive salt intake. Yet, there is little known how the lymphatic contractile function and architecture responds to dietary salt-intake. Our hypothesis is that salt-induced hypertension is accompanied by changes in lymphatic contractile function and architecture. Thus, we longitudinally characterized lymphatic contractile function and vessel remodeling noninvasively using dynamic near-infrared fluorescence (NIRF) imaging in animal models of salt-induced hypertension.
Methods: FVB mice and Sprague Dawley rats were fed ad libitum a HSD diet (4 % NaCl for mice and 8 % NaCl for rats) and 1 % saline for 2 weeks. In addition, another groups of rats received a HSD (8% NaCl) and 1% saline with intraperitoneal treatment with PBS-liposomes (PL) or with clodronate-liposomes (CL), respectively, every 72 hours for 2 weeks. Functional and architectural changes of lymphatics were longitudinally monitored immediately after i.d. injection of indocyanine green (ICG) to the base of each mouse and rat tail and for up to 20 mins every three to four days for 2 weeks. Blood pressure was also monitored using a non-invasive tail-cuff method in conscious animals.
Results: NIRF imaging data showed a significantly increase in the number of lymphatic contractions in mice and rats fed a HSD as compared to baseline and to that in control animals. HSD feeding in rats also increased blood pressure. The quantification of NIRF imaging data also demonstrated that depletion of macrophages using CL in HSD-fed rats significantly increased contraction frequency as compared to control rats, but reduced contraction frequency as compared to rats fed a HSD alone and fed a HSD with treatment of PL, suggesting VEGF-C secreted by macrophages is an important mediator for lymphatic contractility.
Conclusions: Our study successfully demonstrated the ability to non-invasively and quantitatively image propulsive lymph flow in hypertensive animals, which could provide a new method to investigate lymphatic function and its change in response to potential therapeutics.
- © 2013 by American Heart Association, Inc.