A 1D Model Characterizing the Role of Spatiotemporal Contraction Distributions on Lymph Transport

Abstract

ABSTRACTBackgroundLymphedema is a condition in which the two primary functions of the lymphatic system, immunity and lymph transport, are compromised. Computational models of lymphatic function to characterize lymph transport have proved useful in quantifying changes in lymph transport in health and disease; however, much is unknown regarding the regulation of contractions throughout a lymphatic network. The purpose of this paper is to study the role of pacemaking cells and contractile wave propagation on lymph transport using a 1-D mathematical model.MethodA 1D fluid-solid modeling framework with constitutive relationships were employed to characterize the interaction between the contracting vessel wall and the lymph flow during contractions. The time-space distribution of contraction waves along the length of a three-lymphangion chain, was determined by prescribing the location of pacemaking cells and parameters that govern the contractile wave propagation, with the total contractile response at each location determined as the summation of the local electrical signals.ResultsSpatiotemporal changes in radius and lymphangion ejection fraction from our illustrative simulations mimic well values reported in isolated lymphatics from the wild-type (WT) and Smmhc-CreERT2;Cx45fx/fx knock-out (KO) reported in the literature. The flow rate is 5.43 and 2.45 μL/hr in the WT and the KO (average) models, respectively. The average and the peak WSS in the WT model are 0.08 and 4 dyn/cm2 and −0.03 and 0.87 dyn/cm2 in the KO (average) models, respectively.ConclusionsThe factors that govern the timing of lymphatic contractions remain largely unknown; but these factors likely play a central role in health and disease. This modeling framework captures well lymphatic contractile wave propagations and how it relates to lymph transport and may motivate novel assays and experimental endpoints to evaluate subtle changes in lymphatic pumping function in the development and progression of lymphedema.