Preclinical evaluation of Apelin mRNA delivery for the treatment of lymphedema
Secondary lymphedema is a chronic condition causes by a lymphatic dysfunction leading to the accumulation of fluid and fibrotic adipose tissue (AT) in the limb. It is a characterized by tortuous lymphatic capillary network and a severe decrease in lymphatic collecting vessels pumping. Whereas the vascular endothelial growth factor-C (VEGF-C) is well known to promote lymphatic capillary growth, poorly is known about the regenerative control of the lymphatic collecting vessels. Here, we identified apelin as a powerful molecule for regenerating collector function. We found a significant decrease in apelin expression in lymphedematous arm compared to the normal arm in women who developed secondary lymphedema after breast cancer. The role of apelin in lymphedema was confirmed in apelin-knockout mice, in which lymphedema is aggravated and associated with fibrosis and dermal backflow. This was reversed by intradermal injection of apelin-lentivector that significantly reduced limb swelling and dermis fibrosis and was associated with an increase in lymphatic density. Mechanistically, we discovered that apelin stimulates both lymphatic endothelial cell (LEC) gene expression and signaling. Apelin induces E2F transcription factor 8 (E2F8) on the promoter of collagen- and calcium-binding EGF domains 1 (CCBE1) that controls VEGF-C processing.  At cellular level, apelin induces Akt and eNOS pathways to stimulate lymphatic pumping. Our results show that apelin represents a novel partner for VEGF-C to restore lymphatic function in lymphedema. As secondary lymphedema appears after cancer treatment, we validated the apelin-VEGF-C combination using a novel class of safe and non-integrative RNA-delivery lentiflash vector for the treatment of lymphedema. This study paves the way for a novel therapy using Lentiflash vector that will be evaluated for phase I/IIa clinical trial for the treatment of lymphedema