Inflammation-Driven Dermal Lymphangiogenesis in Atopic Dermatitis is Associated with CD11b+ Macrophage Recruitment and VEGF-C Up-regulation in the IL-4-Transgenic Mouse Model

Please cite this paper as: Shi VY, Bao L, Chan LS. Inflammation-driven dermal lymphangiogenesis in atopic dermatitis is associated with CD11b+ macrophage recruitment and VEGF-C up-regulation in the IL-4-transgenic mouse model. Microcirculation 19: 567–579, 2012. Abstract Objective: To investigate the presence and extent of inflammatory lymphangiogenesis in AD and determine the role of IL-4 in lymphatic proliferation in both K14-IL-4 Tg mouse model of AD and cultured human epidermal cells. Methods: Skin tissues from Tg mice were collected for immunostaining against PDPN, LYVE-1, CD11b and VEGF-C. The regulation of specific lymphatic biomarkers and growth factors were determined using qPCR and Western Blot analyses. Dermal lymphatic uptake and drainage were assessed using intradermal EB dye micro-injections. Total RNA from IL-4-stimulated HaCaT cells was analyzed in a PCR array to evaluate the regulation of lymphangiogenic-related genes. Results: Prominent dermal microvascular lymphangiogenesis occurs in the Tg mice, characterized by a significant increase in number and caliber of the vasculature. The extent of both lymphatic proliferation and drainage parallels the progression of lesion severity, as does the up-regulation of pro-lymphangiogenic factors VEGF-C, VEGFR-3, ANG-1, and ANG-2. IL-4-stimulated HaCaT cells express high levels of MCP-1, a strong macrophage chemo-attractant. Additionally, Tg mice show significantly increased number of dermal CD11b+ macrophages expressing VEGF-C in the skin. Conclusions: Our results provide the first demonstration of inflammation-mediated lymphangiogenesis in AD and that IL-4 triggered macrophage recruitment may be closely linked to this phenomenon.