THE PRESENCE OF MYOFIBROBLASTS, SMOOTH MUSCLE CELLS AND ELASTIC FIBERS IN THE LYMPHATIC COLLECTORS OF HORSES

Abstract

Horses are highly susceptible to lymphedema. Knowledge of the morphological componentsof lymphatic collectors is therefore essential to understanding the function of the lymphaticsystem. A better knowledge of the lymphatic system allows the development of more effectivetreatments against lymphedema. The composition of hypodermal and deep lymphatic collectorswas investigated with immunohistochemical staining, using antibodies against proteins of thecollector walls from the skin in the hind limbs of 10 healthy horses. Lymphatic collectors can besubdivided into passive (elastic fibers) and active (smooth muscle cells and myofibroblasts)components. The presence of myofibroblasts in equine lymphatic collectors has not previouslybeen described. The high concentration of myofibroblasts, especially in the dermal collectors,suggests their possible importance in lymph flow. Myofibroblasts may act as pacemaker cells forthe contraction of smooth muscle cells and probably play a role in the proliferation of smoothmuscle cells during training, as there appears to be correlation between the percentage ofsmooth muscle cells in equine lymphatic collectors and level of physical fitness. The response ofthe lymphatics to stimulation may allow effective treatment of lymphedema without usingpharmacological drugs. The high percentage of elastic fibers (approximately 45% in equinelymphatic collectors) indicates the importance of passive components within the lymph flow.