ABSTRACT
BACKGROUND: Sustained lymph stagnation engenders a pathological response that is complex and not well characterized. Tissue inflammation in lymphedema may reflect either an active or passive consequence of impaired immune traffic. METHODS AND FINDINGS: We studied an experimental model of acute post-surgical lymphedema in the tails of female hairless, immunocompetent SKH-1 mice. We performed in vivo imaging of impaired immune traffic in experimental, murine acquired lymphatic insufficiency. We demonstrated impaired mobilization of immunocompetent cells from the lymphedematous region. These findings correlated with histopathological alterations and large-scale transcriptional profiling results. We found intense inflammatory changes in the dermis and the subdermis. The molecular pattern in the RNA extracted from the whole tissue was dominated by the upregulation of genes related to acute inflammation, immune response, complement activation, wound healing, fibrosis, and oxidative stress response. CONCLUSIONS: We have characterized a mouse model of acute, acquired lymphedema using in vivo functional imaging and histopathological correlation. The model closely simulates the volume response, histopathology, and lymphoscintigraphic characteristics of human acquired lymphedema, and the response is accompanied by an increase in the number and size of microlymphatic structures in the lymphedematous cutaneous tissues. Molecular characterization through clustering of genes with known functions provides insights into processes and signaling pathways that compose the acute tissue response to lymph stagnation. Further study of genes identified through this effort will continue to elucidate the molecular mechanisms and lead to potential therapeutic strategies for lymphatic vascular insufficiency.
Subject(s)
Dermatitis/etiology , Inflammation/etiology , Lymphedema/complications , Postoperative Complications/etiology , Animals , Cell Lineage , Cell Movement , Complement Activation/genetics , Dermatitis/immunology , Dermatitis/physiopathology , Female , Fibrosis/genetics , Gene Expression Profiling , Glycoproteins/analysis , Granulocytes/pathology , Granulocytes/transplantation , Immunocompetence , Inflammation/diagnostic imaging , Inflammation/genetics , Inflammation/immunology , Inflammation/physiopathology , Luciferases/analysis , Luciferases/genetics , Lymphedema/diagnostic imaging , Lymphedema/genetics , Lymphedema/immunology , Lymphedema/physiopathology , Lymphocyte Subsets/pathology , Lymphocyte Subsets/transplantation , Lymphoscintigraphy , Membrane Transport Proteins , Mice , Mice, Hairless , Mice, Inbred Strains , Mice, Transgenic , Microspheres , Oligonucleotide Array Sequence Analysis , Organ Size , Oxidative Stress/genetics , Polymerase Chain Reaction , Postoperative Complications/immunology , Postoperative Complications/physiopathology , RNA, Messenger/biosynthesis , Spleen/pathology , Tail/blood supply , Tail/pathology , Tail/surgery , Transcription, Genetic , Wound Healing/geneticsABSTRACT
Chronic regional impairments of the lymphatic circulation often lead to striking architectural abnormalities in the lymphedematous tissues. Lymphedema is a common, disabling disease that currently lacks a cure. Vascular endothelial growth factors C and D mediate lymphangiogenesis through the VEGFR-3 receptor on lymphatic endothelia. The purpose of this study was to investigate the therapeutic potential for lymphangiogenesis with VEGF-C. We developed a rabbit ear model to simulate human chronic postsurgical lymphatic insufficiency. Successful, sustained surgical ablation of the ear lymphatics was confirmed by water displacement volumetry. After complete healing, the experimental animals (n=8) received a single, s.c. 100 microg dose of VEGF-C in the operated ear; controls (n=8) received normal saline. Radionuclide lymphoscintigraphy was performed to quantitate lymphatic function. Immunohistochemistry (IHC) was performed 7-8 days following treatment. After VEGF-C, there was a quantifiable amelioration of lymphatic function. IHC confirmed a significant increase in lymphatic vascularity, along with reversal of the intense tissue hypercellularity of untreated lymphedema. This study confirms the capacity of a single dose of VEGF-C to induce therapeutic lymphangiogenesis in acquired lymphedema. In addition to improving lymphatic function and vascularity, VEGF-C can apparently reverse the abnormalities in tissue architecture that accompany chronic lymphatic insufficiency.
