Single and combined impacts of irradiation and surgery on lymphatic vasculature and fibrosis associated to secondary lymphedema

Abstract

Lymphedema (LD) refers to a condition of lymphatic dysfunction associated with excessive fluid accumulation, fibroadipose tissue deposition and swelling. In industrialized countries, LD development mainly results from a local disruption of the lymphatic network by an infection or cancer-related surgery (secondary LD). In the absence of efficient therapy, animal models are needed to decipher the cellular and molecular mechanisms underlying LD and test putative drugs. In this study, we optimized and characterized a murine model of LD that combines an irradiation of the mice hind limb and a radical surgery (lymph node resection associated to lymphatic vessel ligation). We investigated the respective roles of irradiation and surgery in LD formation by comparing their impacts, alone or in combination (with different intervention sequences), on eight different features of the pathology: swelling (paw thickness), indocyanine green (ICG) clearance, lymphatic vasculature remodeling, epidermal and dermal thickening, adipocyte accumulation, inflammatory cell infiltration and collagen deposition. This study supports the importance of radiation prior to surgery to experimentally induce a rapid, severe and sustained tissue remodeling harboring the different hallmarks of LD. We provide the first experimental evidence for an excessive deposition of periostin (POSTN) and tenascin-C (TNC) in LD. Through a computerized method of digital image quantification, we established the spatial map of lymphatic expansion, as well as collagen, POSTN and TNC deposition in papillary and reticular dermis of lymphedematous skins. This mouse model is available to study the patho-physiology of LD and test potential therapeutic targets.

Development of a rat model of lymphedema and the implantation of a collagen-based medical device for therapeutic intervention

“…Other models of lymphedema involve the removal of popliteal lymph nodes and adjacent lymphatic vessels in the hindlimbs (canine, sheep, and rabbit models) ( 18 – 20 ), and axillary lymph nodes in forelimbs (rat model) ( 21 ). The effect of irradiation prior to lymph node removal in hindlimbs was elegantly studied in mouse model ( 22 ). The removal of both deep and superficial lymphatic vessels around the circumference of the thigh muscle coupled with radiation therapy (45 Gy) in rat hindlimb induced a chronic lymphedema condition persisting up to 9 months ( 23 ), as evaluated by tape measurements of limb circumference and water-fill method, although this radiation dose was associated with considerable mortality.…”