Background: Lymphangiogenesis plays an important role in metastasis of many solid tumors. To study lymphangiogenesis under controlled conditions, an in vitro model is needed. The goal of this work was to establish such an in vitro model by determining a molecular profile of rat mesenteric lymphatic endothelial cells (RMLEC) and characterizing their proliferative responses to angiogenic and lymphangiogenic factors, such as vascular endothelial growth factor A and C (VEGF-A and VEGF-C).
Methods and Results: RMLEC strongly expressed most lymphatic-specific markers, including Prox-1, LYVE-1, and VEGFR-3. Proliferation of RMLEC was serum and heparin dependent.
In the presence of low (2%) serum concentration, exogenously added VEGF-A and VEGFC
stimulated RMLEC in a linear and dose-dependent manner. This effect was abrogated by
anti-VEGF-A and VEGF-C antibodies, as well as by soluble Tie-2 and Flt-4 fusion proteins. Abrogation was reversed by VEGF-A, suggesting that this factor as an important regulator of lymphangiogenesis.
Conclusions: Cultured RMLEC preserved a molecular profile consistent with the phenotype
of lymphatic endothelium in vivo and respond to either VEGF-A or VEGF-C factors. VEGFA
was able to rescue RMLEC proliferation inhibited by a neutralizing VEGF-C antibody or
soluble Tie-2 fusion protein. These results support the existence of cross-talk among angiogenic
and lymphangiogenic factors. This work established experimental conditions that allow
in vitro modeling of lymphatic endothelial responses to lymphangiogenic regulators. Preliminary
results using this model suggest that VEGF-A, VEGF-C, and angiopoietins work in
concert to promote lymphangiogenesis in vivo.
