Lymphatic Endothelial Cells under Mechanical Stress: Altered Expression of Inflammatory Cytokines and Fibrosis

Secondary lymphedema, resulting from damage to lymphatic vessels, is a common sequela following surgical removal of lymph nodes for cancer. Current therapeutics for treating lymphedema are limited and further research on underlying causes is warranted. Published studies on molecular mechanisms of lymphedema primarily focus on lymphatic endothelial cells (LECs), which comprise the innermost lining of lymphatic capillaries and collecting vessels. However, traditional static culture of LECs may not adequately recapitulate the lymphedemous cell phenotype as transcriptomal comparison of human dermal LECs has shown significant differences in ex vivo and in vitro LEC gene expression. In this study, we designed a dynamic culture system, in which LECs were exposed to physiologic and excess mechanical strain to determine if native and lymphedemous phenotypes could be reproduced in vitro.

Purified human LECs were cultured in silicon dishes and subjected to 0% (control), 4%, and 8% mechanical strain for 72 hours. Our results indicate that control and stretched LECs maintained a mature phenotype. Extreme stretching at 8% strain significantly increased LEC proliferation and significantly increased Prox1 expression, suggesting a lymphedemous cell phenotype resulting with lymphangiogenesis.

Mechanical strain reinforced a mature lymphatic phenotype and excess strain promoted lymphangiogenesis, while altering collagen deposition and cytokine secretion.