Lymphatic Biomechanics & BioEngineering Lab (LBBL)

Secondary lymphedema is a debilitating condition driven by impaired regeneration of lymphatic vasculature following lymphatic injury, surgical removal of lymph nodes in cancer patients, or infection. However, the extent to which collecting lymphatic vessels regenerate following injury remains unclear. Here, we employed a novel mouse model of lymphatic injury in combination with state-of-the-art lymphatic imaging to demonstrate that the implantation of an optimized fibrin gel following lymphatic vessel injury leads to the reconnection of the injured lymphatic vessel network through sprouting lymphangiogenesis of initial-like lymphatic vessels from the ends of the collecting lymphatic vessels, resulting in the restoration of lymph flow to the draining lymph node. Mechanistically, we found that fibrin implantation elevates the tissue levels of CCL5, a potent immune cell-recruiting chemokine. Notably, injured vessels in CCL5-KO mice made fewer connections following fibrin gel implantation. These novel findings shed light on the mechanisms underlying lymphatic regeneration and suggest that enhancing CCL5 signaling may be a promising therapeutic strategy for enhancing lymphatic regeneration.

Despite significant strides in lymphatic system imaging, the timely diagnosis of lymphatic disorders remains elusive. This is driven by the absence of standardized, non-invasive, reliable, quantitative methods for real-time functional analysis of lymphatic contractility with adequate spatial and temporal resolution. Here, we address this unmet need by integrating near-infrared fluorescence lymphangiography imaging with an innovative analytical workflow that combines data acquisition, signal processing, and statistical analysis to integrate traditional peak-and-valley analysis with advanced wavelet time-frequency analyses. Variance component analysis was used to evaluate the drivers of variance attributable to each experimental variable for each lymphangiography measurement type. Generalizability studies were used to assess the reliability of measured parameters and how reliability improves as the number of repeat measurements per subject increases. This allowed us to determine the minimum number of repeat measurements needed per subject for acceptable measurement reliability. This approach not only offers detailed insights into lymphatic pumping behaviors across species, sex and age, but also significantly boosts the reliability of these measurements by incorporating multiple regions of interest and evaluating the lymphatic system under various gravitational loads. For example, the reliability of the peak-and-valley analysis of human lymphatic vessels was increased 3-fold using the described approach. By addressing the critical need for improved imaging and quantification methods, our study offers a new standard approach for the imaging and analysis of lymphatic function that can improve our understanding, diagnosis, and treatment of lymphatic diseases. The results highlight the importance of comprehensive data acquisition strategies to fully capture the dynamic behavior of the lymphatic system.