Comparison of normal hindlimb lymphatic systems in rats with detours present after lymphatic flow blockage.

Yuiko Suzuki,Yukari Nakajima,Mayumi Okuwa,Junko Sugama,Toshio Nakatani,Atsushi Asakura

doi:10.1371/journal.pone.0260404

Yuiko Suzuki, Yukari Nakajima + Show 4 more

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https://doi.org/10.1371/journal.pone.0260404

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Abstract

In the present study, we aimed to identify the normal hindlimb lymphatic systems in rats and compare them with the detours after lymphatic flow blockage. The lymphatic systems of the hindlimbs of normal rats were investigated via lymphography using a near-infrared fluorescence imaging system. The lymphatic vessels were stained using Evans Blue. The lymphatic flow was blocked through lymphatic vessel ligation combined with inguinal and popliteal lymph node dissection. Detours that appeared after 30 days were visualized using lymphography and immunostaining with anti-podoplanin antibodies. Three main results were obtained in the present study. First, the deep medial system, the superficial medial system, a connection between the superficial and deep medial lymphatic systems, and the superficial lateral system, were elucidated. Second, three types of detours, namely the detour of the lateral abdomen, the detour to the lymphatic vessel near the midline of the abdomen, and the detour to the contralateral inguinal lymph node, were identified after lymphatic flow blockage. Lastly, detours were located in the fatty layer above the panniculus carnosus muscle and their lumina were wide. The histology suggested that the detour was a pre-collecting lymphatic vessel. Lymphatic routes in the rat hindlimbs after lymphatic flow blockage were different from those of the normal rat lymphatic system. It was suggested that the detour is a pre-collecting lymphatic vessel and that encouraging its development may be a new method of simple lymphatic drainage.

Highlights

Secondary lymphedema is a chronic disease that is characterized by tissue swelling due to excess lymphatic fluid retention in the interstitial spaces
The lymphatic routes were identified through indocyanine green (ICG) lymphography, Evans Blue (EB) staining, and immunostaining with the anti-podoplanin antibody
The deep medial system was identified when ICG was injected into the rat’s inner ankle. It is likely could no longer visualize the fluorescence at the inguinal area due to the increasing depth of the lymphatic vessels (LVs) below the skin (Fig 1B)

Summary

Introduction

Secondary lymphedema is a chronic disease that is characterized by tissue swelling due to excess lymphatic fluid retention in the interstitial spaces. Breast cancer-related lymphedema occurs after breast cancer treatment, such as the dissection of lymph nodes (LNs) in cancer resection or radiation therapy [1, 2]. There is no curative treatment for lymphedema. Complete decongestive therapy is considered the gold-standard treatment for managing lymphedema and includes two phases: reduction and maintenance [6]. Patients are requested to perform daily self-care, including simple lymphatic drainage (SLD), application of compression garments, physical exercises, and skincare [7]. The aim of SLD is to prevent the accumulation of lymph fluid, but a full body massage is time-consuming. The effectiveness of SLD is unclear owing to the paucity of information [7,8,9]

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