REGENERATION OF THE ENDOTHELIUM IN THE CANINE AND FELINE THORACIC-DUCT

Recent improvements in microsurgical techniques on lymphatic vessels facilitated the treatment of lymphoedema. But it is becoming clear that a successful treatment of lymphatic disease has to be based on knowledge of ongoing processes. Particularly, one of the important and unclear issue is cellular mechanisms of lymphatic regeneration. The regeneration of endothelial and the smooth muscle cells of the thoracic duct has been experimentally tested in vivo. The canine and feline thoracic duct was cryo-injured using 3 mm-based copper rod. Damaged endothelial cells remained attached to the substrate and lost unthrombogenecy within 48 hr. Adjacent EC restored the defect within 3 days by migration and proliferation. We observed that on the first day, the endothelial monolayer included some elongated multinuclear cells with blind silver lines whereas, on the third day, they were replaced by a population of smaller ECs with numerous mitoses. Organization of the monolayer was restituted within 7 days. The newly formed endothelium was similar to regenerating endothelium of arteries. In general, the clot that appeared at the zone of injury on the second day was dissolved by the third day. Occasionally, the dense polymorphic clot adhered to the wall and caused a delay in reendothelisation. Complete restitution of the tunica media which involved migration and proliferation mechanisms accompanied the endothelium regeneration.