Quantification of Lymphatic Vascular Permeability via Near-Infrared Imaging

Abstract

Though the lymphatic system is involved in many essential bodily functions, little is known about its role in the progression of lymphatic diseases like lymphedema. Recently, inflammation has been implicated as the primary mediator of lymphatic pathologies, due to its ability to decrease lymphatic function and induce a mal-adaptive remodeling response (Aldrich & Sevick-Muraca, 2013). One of the failure modes that inflammation is hypothesized to influence is by increasing the permeability of the lymphatic vasculature (Scallan & Huxley, 2010). A minimally-invasive method of quantifying lymphatic vessel permeability was designed using near-infrared imaging, a fluorescent tracer, and applied pressure. The method partially occluded the lymphatic collecting vessels and was tested using IFN-γ as a positive control. The average apparent permeability for the control group was determined to be somewhat similar to a previous in vivo study of isolated vessels but had a wide range of values overall (Scallan & Huxley, 2010). Comparison of the IFN-γ treated group to the control group revealed no significant difference and therefore inconclusive results as to the accuracy of the method. Future work will include testing different positive controls to verify the method followed by application of the method on diet-induced obese mice for determination of the changes to vessel permeability as compared to the control group to understand possible causes that contribute to the development of lymphatic diseases like lymphedema.