Lymphatics in lymphangioleiomyomatosis and idiopathic pulmonary fibrosis.

Sept 2012

Glasgow CG, El-Chemaly S, Moss J.

Source

Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1590, USA.

Abstract

The primary function of the lymphatic system is absorbing and transporting macromolecules and immune cells to the general circulation, thereby regulating fluid, nutrient absorption and immune cell trafficking. Lymphangiogenesis plays an important role in tissue inflammation and tumour cell dissemination. Lymphatic involvement is seen in lymphangioleiomyomatosis (LAM) and idiopathic pulmonary fibrosis (IPF). LAM, a disease primarily affecting females, involves the lung (cystic destruction), kidney (angiomyolipoma) and axial lymphatics (adenopathy and lymphangioleiomyoma). LAM occurs sporadically or in association with tuberous sclerosis complex (TSC). Cystic lung destruction results from proliferation of LAM cells, which are abnormal smooth muscle-like cells with mutations in the TSC1 or TSC2 gene. Lymphatic abnormalities arise from infiltration of LAM cells into the lymphatic wall, leading to damage or obstruction of lymphatic vessels. Benign appearing LAM cells possess metastatic properties and are found in the blood and other body fluids. IPF is a progressive lung disease resulting from fibroblast proliferation and collagen deposition. Lymphangiogenesis is associated with pulmonary destruction and disease severity. A macrophage subset isolated from IPF bronchoalveolar lavage fluid (BALF) express lymphatic endothelial cell markers in vitro, in contrast to the same macrophage subset from normal BALF. Herein, we review lymphatic involvement in LAM and IPF.

European Respiratory

Contractile Physiology of Lymphatics

Contractile Physiology of Lymphatics

Lymphat Res Biol. 2009

Zawieja DC.

Department of Systems Biology and Translational Medicine, Cardiovascular Research Institute Division of Lymphatic Biology, Texas A&M Health Science Center College of Medicine, Temple, Texas 77843-1114, USA.

The lymphatic system has important roles in body fluid regulation, macromolecular homeostasis, lipid absorption, and immune function. To accomplish these roles, lymphatics must move fluid and its other contents (macromolecules, lipids/chylomicra, immune cells) from the interstitium through the lymphatics, across the nodes, and into the great veins. Thus, the principal task of the lymphatic vascular system is transport.

The body must impart energy to the lymph via pumping mechanisms to propel it along the lymphatic network and use pumps and valves to generate lymph flow and prevent its backflow. The lymphatic system utilizes both extrinsic pumps, which rely on the cyclical compression and expansion of lymphatics by surrounding tissue forces, and intrinsic pumps, which rely on the intrinsic rapid/phasic contractions of lymphatic muscle.

The intrinsic lymph pump function can be modulated by neural, humoral, and physical factors. Generally, increased lymph pressure/stretch of the muscular lymphatics activates the intrinsic lymph pump, while increased lymph flow/shear in the muscular lymphatics can either activate or inhibit the intrinsic lymph pump depending on the pattern and magnitude of the flow. To regulate lymph transport, lymphatic pumping and resistance must be controlled.

A better understanding of these mechanisms could provide the basis for the development of better diagnostic and treatment modalities for lymphatic dysfunction.

MaryAnnLiebert