title: Toll-like receptor deficiency worsens inflammation and lymphedema after lymphatic injury.
abstract: Mechanisms regulating lymphedema pathogenesis remain unknown. Recently, we have shown that lymphatic fluid stasis increases endogenous danger signal expression, and these molecules influence lymphatic repair (Zampbell JC, et al. Am J Physiol Cell Physiol 300: C1107-C1121, 2011). Endogenous danger signals activate Toll-like receptors (TLR) 2, 4, and 9 and induce homeostatic or harmful responses, depending on physiological context. The purpose of this study was to determine the role of TLRs in regulating tissue responses to lymphatic fluid stasis. A surgical model of lymphedema was used in which wild-type or TLR2, 4, or 9 knockout (KO) mice underwent tail lymphatic excision. Six weeks postoperatively, TLR KOs demonstrated markedly increased tail edema compared with wild-type animals (50-200% increase; P < 0.01), and this effect was most pronounced in TLR4 KOs (P < 0.01). TLR deficiency resulted in decreased interstitial and lymphatic transport, abnormal lymphatic architecture, and fewer capillary lymphatics (40-50% decrease; P < 0.001). Lymphedematous tissues of TLR KOs demonstrated increased leukocyte infiltration (P < 0.001 for TLR4 KOs), including higher numbers of infiltrating CD3+ cells (P < 0.05, TLR4 and TLR9 KO), yet decreased infiltrating F4/80+ macrophages (P < 0.05, all groups). Furthermore, analysis of isolated macrophages revealed twofold reductions in VEGF-C (P < 0.01) and LYVE-1 (P < 0.05) mRNA from TLR2-deficient animals. Finally, TLR deficiency was associated with increased collagen type I deposition and increased transforming growth factor-β1 expression (P < 0.01, TLR4 and TLR9 KO), contributing to dermal fibrosis. In conclusion, TLR deficiency worsens tissue responses to lymphatic fluid stasis and is associated with decreased lymphangiogenesis, increased fibrosis, and reduced macrophage infiltration. These findings suggest a role for innate immune responses, including TLR signaling, in lymphatic repair and lymphedema pathogenesis.
authors: Division of Plastic and Reconstructive Surgery, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors: Jamie C
authors: JC
authors: Zampell
authors: Sonia
authors: S
authors: Elhadad
authors: Tomer
authors: T
authors: Avraham
authors: Evan
authors: E
authors: Weitman
authors: Seth
authors: S
authors: Aschen
authors: Alan
authors: A
authors: Yan
authors: Babak J
authors: BJ
authors: Mehrara
mesh_terms: D000818:Animals; D003094:Collagen / Q000276:immunology / Q000378:metabolism; D005260:Female; D005355:Fibrosis / Q000150:complications / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D017353:Gene Deletion; D015870:Gene Expression / Q000276:immunology; D006023:Glycoproteins / Q000276:immunology / Q000378:metabolism; D007113:Immunity, Innate; D007249:Inflammation / Q000150:complications / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D017254:Leukemic Infiltration / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D042583:Lymphangiogenesis / Q000235:genetics / Q000276:immunology*; D042601:Lymphatic Vessels / Q000276:immunology / Q000293:injuries / Q000378:metabolism*; D008209:Lymphedema / Q000150:complications / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics; D051217:Toll-Like Receptor 9 / Q000172:deficiency / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000276:immunology / Q000378:metabolism; D042582:Vascular Endothelial Growth Factor C / Q000276:immunology / Q000378:metabolism
chemical_list: D003094:Collagen; D006023:Glycoproteins; D026901:Membrane Transport Proteins; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D053773:Transforming Growth Factor beta1; D042582:Vascular Endothelial Growth Factor C; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; C495370:Tlr9 protein, mouse; C492273:LYVE1 protein, mouse