Seminar 17th January 2014 1 p.m. 85/2209
BIOENGINEERING SEMINAR, Lymphatic System Biomechanics and Pumping
Prof Jimmy Moore
Imperial College London
- Web page
- http://www.imperial.ac.uk/AP/faces/pages/read/Home.jsp?person=james.moore.jr&_adf.ctrl-state=ih9ddsi1f_107&_afrRedirect=2514615360894937
- Categories
- Bioinformatics, Biomathematics, Biomedical
- Submitter
- Nicholas Evans
SEMINAR, Friday 17th January 2014, 13:00, 85/2209
Lymphatic System Biomechanics and Pumping
James E. Moore Jr., Ph.D. The Bagrit and Royal Academy of Engineering Chair in Medical Device Design, Department of Bioengineering, Imperial College London. james.moore.jr@imperial.ac.uk
The lymphatic system is an extensive vessel network featuring one-way valves and contractile walls that pump interstitial fluid, plasma proteins, lipids and immune cells through lymph nodes and then back to the blood circulation at the subclavian veins. This system is crucial in the function of the immune system, as well as being the pathway of distribution for metastatic cells arising from the most deadly forms of cancer. Failure to drain and pump this excess fluid results in edema, characterized by fluid retention and swelling of limbs. This condition affects a large number of cancer survivors who have had lymph nodes removed as part of their treatment, and is incurable.
We are developing multi-scale computational models of lymphatic function from the sub-cellular to the whole organ level in conjunction with a series of experiments aimed at elucidating desirable model characteristics and providing model parameter estimations. Our modeling is based on lymphatic endothelial and smooth muscle cell mechanotransduction of flow-induced shear stress and vessel diameter. Models of vessel segments in series have been characterized through pump curves of steady pressure difference versus flow rate. These curves exhibit non-linear behaviors typical of mixed source pumps, with a sharp drop-off at the maximum flow rate in some cases. These models also provide the opportunity to quantify the importance of various modeling parameters through sensitivity analysis. For example, the phase angle between successive lymphangion contractions is an important determinant of pumping efficiency, with out-of-phase behavior being the most efficient.
Experimental support for the modeling efforts includes multiple approaches. Experiments with rat mesentery lymphatics revealed that these vessels quickly adapted to increased volume loads by increasing lymph flow rate and contraction frequencies. Valves are biased toward the open position, with that bias increasing with transmural pressure.
Unlike the arterial and venous systems, the lymphatic system has not been the subject of extensive modeling efforts. Our work is aimed at constructing models that strike a delicate balance between the need to represent complex physiological phenomena and the desire to keep the modeling feasible computationally. The multi-scale approach is ideally suited for this purpose.