Regulation of Adipogenesis by Lymphatic Fluid Stasis Part I: Adipogenesis, Fibrosis, and Inflammation

Background Although fat deposition is a defining clinical characteristic of lymphedema, the cellular mechanisms that regulate this response remain unknown. The goals of this two-part study were to determine the effect of lymphatic fluid stasis on adipogenesis and inflammation (part 1) and how these changes regulate the temporal and spatial expression of fat differentiation genes (part 2). Methods Adult female mice underwent tail lymphatic ablation and were sacrificed 6 weeks after surgery (n=20). Fat deposition, fibrosis, and inflammation were then analyzed in the regions of the tail exposed to lymphatic fluid stasis as compared with normal lymphatic flow. Results Lymphatic fluid stasis in the tail resulted in significant subcutaneous fat deposition with a 2-fold increase in fat thickness (p<0.01). In addition, lymphatic stasis was associated with subcutaneous fat fibrosis and collagen deposition. Adipogenesis in response to lymphatic fluid stasis was associated with a marked mononuclear cell inflammatory response (5-fold increase in CD45+ cells; p<0.001). In addition, we noted a significant increase in the number of monocytes/macrophages as identified by F4/80 immunohistochemistry (p