Quantification of Lymphangiogenesis in the Murine Lymphedema Tail Model Using Intravital Microscopy

Background: Lymphedema is chronic limb swelling resulting from lymphatic dysfunction. It affects an estimated five million Americans. There is no cure for this disease. Assessing lymphatic growth is essential in developing novel therapeutics. Intravital microscopy (IVM) is a powerful imaging tool for investigating various biological processes in live animals. Tissue nanotransfection technology (TNT) facilitates a direct, transcutaneous nonviral vector gene delivery using a chip with nanochannel poration in a rapid (<100 ms) focused electric field. TNT was used in this study to deliver the genetic cargo in the murine tail lymphedema to assess the lymphangiogenesis. The purpose of this study is to experimentally evaluate the applicability of IVM to visualize and quantify lymphatics in the live mice model. Methods and Results: The murine tail model of lymphedema was utilized. TNT was applied to the murine tail (day 0) directly at the surgical site with genetic cargo loaded into the TNT reservoir: TNT_pCMV6 group receives pCMV6 (expression vector backbone alone) (n = 6); TNT_Prox1 group receives pCMV6-Prox1 (n = 6). Lymphatic vessels (fluorescein isothiocyanate [FITC]-dextran stained) and lymphatic branch points (indicating lymphangiogenesis) were analyzed with the confocal/multiphoton microscope. The experimental group TNT_Prox1 exhibited reduced postsurgical tail lymphedema and increased lymphatic distribution compared to TNT_pCMV6 group. More lymphatic branching points (>3-fold) were observed at the TNT site in TNT_Prox1 group. Conclusions: This study demonstrates a novel, powerful imaging tool for investigating lymphatic vessels in live murine tail model of lymphedema. IVM can be utilized for functional assessment of lymphatics and visualization of lymphangiogenesis following gene-based therapy.