Lymphatic Vasculature Requires Estrogen Receptor-α Signaling to Protect From Lymphedema.

OBJECTIVE: Estrogens exert beneficial effect on the blood vascular system. However, their role on the lymphatic system has been poorly investigated. We studied the protective effect of the 17β estradiol-the most potent endogenous estrogen-in lymphedema-a lymphatic dysfunction, which results in a massive fluid and fat accumulation in the limb.

APPROACH AND RESULTS: Screening of DNA motifs able to mobilize ERs (estrogen receptors) and quantitative real-time polymerase chain reaction analysis revealed that estradiol promotes transcriptional activation of lymphangiogenesis-related gene expression including VEGF (vascular endothelial growth factor)-D, VEGFR (VEGF receptor)-3, lyve-1, and HASs (hyaluronan synthases). Using an original model of secondary lymphedema, we observed a protective effect of estradiol on lymphedema by reducing dermal backflow-a representative feature of the pathology. Blocking ERα by tamoxifen-the selective estrogen modulator-led to a remodeling of the lymphatic network associated with a strong lymphatic leakage. Moreover, the protection of lymphedema by estradiol treatment was abrogated by the endothelial deletion of the receptor ERα in Tie2-Cre; ERαlox/lox mice, which exhibit dilated lymphatic vessels. This remodeling correlated with a decrease in lymphangiogenic gene expression. In vitro, blocking ERα by tamoxifen in lymphatic endothelial cells decreased cell-cell junctions, inhibited migration and sprouting, and resulted in an inhibition of Erk but not of Akt phosphorylation.

CONCLUSIONS: Estradiol protection from developing lymphedema is mediated by an activation of its receptor ERα and is antagonized by tamoxifen. These findings reveal a new facet of the estrogen influence in the management of the lymphatic system and provide more evidence that secondary lymphedema is worsened by hormone therapy.