Abstract
Molecular mechanisms of reconnection of collecting lymph vessels were analyzed by using murine popliteal prenodal lymph vessels. At 1 and 2 weeks after being divided by cutting the lymph vessel, lymphatic reconnection was frequently observed accompanied by mesh-like lymphatic channels. Electron microscopic study also showed a monolayer of endothelial cells in the newly developed lymph vessels. Smooth muscle markers were immunofluorescently demonstrated in the wall of the new vessels. At 1 week after the procedure of cutting, augmented expressions of VEGF receptors 1, 2 and 3 were found immunohistochemically at the site of the reconnected lymph vessels. The expression of mRNA for VEGF receptor 3 was enhanced at 5 days and 1 week in small pieces of the tissues containing the reconnected lymph vessels, compared with that in the corresponding tissues obtained with sham operated ones. The administration of VEGF-C at the cutting site of the collecting lymph vessel significantly increased the rate of the reconnected lymph vessels, whereas additional treatment with Flt4/Fc chimera protein significantly reduced the rate of the reconnected ones. These results suggest that activation of VEGF-C-VEGF receptor 3 has critical roles in reconnection of the collecting lymph vessels in adult mice.
Acknowledgements
The authors thank Mr. M. Momose, Clinical Laboratory Center, Shinshu University Hospital, for his excellent technical assistance.
This study was supported financially, in part, by a Research Grant from Japan Foundation of Cardiovascular Research, Grants-in-Aid for scientific research (No. 08770032, 09770024, 11470010) from the Japanese Ministry of Education, Science, Sports and Culture, and Grants-in-Aid for scientific research (No. 15500315, 19500384) from the Japan Society for the Promotion of Science.