Creation of a Rat Lower Limb Lymphedema Model

Abstract

Background Lymphedema is a frequent complication after surgical treatments of cancer involving lymph node resection. However, research of lymphedema treatments, such as vascularized lymph node transfer, is limited by the absence of an adequate lymphedema animal model. The purpose of this study was to determine if we could create sustainable lower limb lymphedema in the rat with a combination of inguinal lymphadenectomy, circumferential skin and subcutaneous tissue excision, and radiotherapy. Methods Inguinal lymphadenectomies were completed in 15 Sprague-Dawley rats. In cohort A, 5 rats received a 0.5- to 1.0-cm wide excision of proximal thigh skin and subcutaneous tissue. This step was omitted for the 10 rats in cohort B. Cohort A then received a single radiation dose of 22.7 Gy, whereas cohort B received a cumulative dose of 40.5 Gy. Bioimpedance measurements were obtained monthly to assess lymphedema progression, and lymphatic drainage at 6 months postradiation was visualized via indocyanine green (ICG) lymphangiography. Results Two rats in cohort A developed visually appreciable lymphedema in the lower limb, with bioimpedance ratios of 0.684 and 0.542 and ankle circumference ratios of 1.294 and 1.061, respectively, consistent with lymphedema. Furthermore, ICG lymphangiography in these cohort A rats revealed impaired lower limb lymphatic drainage. In cohort B, however, bioimpedance and circumference ratios, and ICG lymphangiography, did not reveal abnormal lymphatic drainage. Conclusions The combination of inguinal lymphadenectomy, circumferential skin and subcutaneous tissue excision, and radiotherapy can successfully create lower limb lymphedema in the rat. When soft tissue excision is omitted, lymphedema does not develop.

Creation of a rat lymphedema model using extensive lymph node dissection and circumferential soft tissue resection: Is this a reliable model?

“…Both inflammation and fibrosis were successfully established in this animal model. The volume of the hindlimb was measured using micro-CT in our study, and the data correlated with previous publications in which swelling was successfully created (Harb et al, 2020). In addition, ICG lymphography was performed 1 and 2 months after surgery, and a dermal backflow pattern was observed.…”

“…The creation of lymphedema by performing lymph node dissection and circumferential excision of the skin to create soft tissue defects is not a new idea. Similar practice has been reported (Harb et al, 2020;Kanter et al, 1990). However, most of the publications confirmed the presence of lymphedema based on the presence of swelling and reduced nodal uptake of Tc99.…”

“…One of the main difficulties in creating lymphedema in rat hindlimbs is that recovery with lymphatic regeneration or lymphatic drainage from collateral lymphatics is quick. Rats have an extensive superficial lymphatic network with the potential to provide collateral drainage (Harb et al, 2020;Suami & Scaglioni, 2017). This anatomical feature underscores the importance of creating a circumferential skin defect sized 5 mm in the model to block the superficial collateral network of lymphatics and preclude quick recovery from lymphedema.…”

“…The rational of the model design was based on the fact that a circumferential soft-tissue defect completely damages the continuity of functioning lymphatic vessels. Although a similar model has been presented, the investigation of lymphedema seemed to be inadequate without histological features to represent the hallmark of lymphedema (Harb et al, 2020). In our reported model, an increased hindlimb volume and lymphatic stasis were observed after the model was established using micro-computed tomography (CT) and indocyanine green (ICG) lymphography.…”

“…Attempts have been made to create lymphedema in rats or mice that mimics clinical scenarios, such as lymph node dissection and radiotherapy, but many of the models presented transient lymphedema only (Harb et al, 2020;Kanter et al, 1990;Kataru et al, 2019;Park et al, 2013;Wang & Zhong, 1985;Yang et al, 2014). A more sustainable lymphedema model often requires a combination of other interventions, such as regional radiotherapy, with lymph node dissection (Park et al, 2013;Yang et al, 2014).…”