Immunopathology in human lymphoedema

Lymphoedema is a condition of abnormal tissue swelling resulting from failure of lymph drainage. The condition is often chronic and it frequently results in the accumulation of adipose tissue (AT) within the affected region. The mechanisms underlying AT formation in lymphoedema have not been determined. This research therefore aims to characterize the AT of patients with lymphoedema. Liposuction tissue samples were obtained from lymphoedema patients’ limbs (4 arms, 4 legs) and from limbs of healthy individuals undergoing cosmetic liposuction surgery (3 arms, 4 legs). AT tissue samples were fixed in neutral buffered formalin and processed for histological analysis, including hematoxylin and eosin, Milligan’s trichrome, or picrosirius red staining. Image analysis was performed to determine the mean adipocyte cell number, size, tissue fibrosity, and the degree of collagen deposition. Immunohistochemical analyses was also performed, using antibodies specific to lymphatic endothelial cells (podoplanin), blood vascular endothelial cells (CD31), and macrophages (HAM56), to determine the relative location of perivascular collagen and the identity of macrophage-like cells. Histological analysis of lymphoedema AT revealed abundant collagen, especially type III collagen, and perivascular fibrosis. Overall, adipocyte cell number, size, and the extent of collagen content were found to be similar in lymphoedema and normal AT. Using immunohistochemistry, we detected CD31 expression in lymphoedema and normal AT, and this occurred in areas of collagen deposition. Unfortunately, no positive staining for podoplanin and HAM56 were detected in either lymphoedema or normal AT. Taken together, this research provides important information into the etiopathology of this chronic and debilitating condition.