135. Evaluation of Lymphatic Junctional Protein Transformation in Secondary Lymphedema Murine Models

PURPOSE: Secondary lymphedema is a chronic limb swelling resulting from lymphatic dysfunction after lymphatic injury. There is no cure for lymphedema. Capillary lymphatics consist of a single layer of lymphatic endothelial cells and have a discontinuous junction structure (button-like junctions) which enables intersitial fluid clearance whereas collecting vessels are covered by smooth muscle cells (SMCs) and have continuous junctional proteins (zippers). Capillary lymphatic junctional protein zippering has been implicated in primary lymphedema. The purpose of this study is to understand the plasticity of lymphatic morphology during secondary lymphedema progression in murine lymphedema tail and hindlimb model. METHODS: Murine tail and hindlimb models of lymphedema were utilized. Normal and lymphedema-induced mice tail and hindlimb (post-op day 14) tissues were used to study junctional proteins. Horizontal whole mount of mice tail/hindlimb skin was immunostained with LYVE1 (lymphatics) and VE-Cadherin (junction protein). Images were acquired using 63x glycerol immersion objective on a Leica upright confocal microscope. The proportions of junctional proteins comprised of buttons, intermediates and zippers were calculated in the z-stack images using Imaris. Junctional morphology were quantified based on VE-Cadherin pattern in the LYVE1 stained areas. RESULTS: A significant change in buttons (p=0.004), intermediate (p=0.026), Zippers (p=0.039) in post-surgical lymphedema compared to normal mice tail. The variation in junctional pattern may hinder intersitial fluid during lymphedema progression. CONCLUSION: Lymphatic junctional proteins plasticity occurred in lymphedema with greater zipper proteins and less buttons in both murine tail and murine hindlimb lymphedema models. The transition to zipper junctional proteins may hinder interstitial fluid clearance in secondary lymphedema and provide new targets for treatment strategies.