M2 macrophage polarization in cutaneous polyarteritis nodosa: an immunohistochemical study

Abstract

Background Cutaneous polyarteritis nodosa (CPAN), a cutaneous vasculitis that affects small-and medium-sized arteries, is thought to be mediated by immune complexes. However, little is known about its etiology. Macrophages are important pathogenic factors in various vascular inflammatory diseases, including certain types of vasculitis. However, their role in CPAN remains unexplored. Objectives To describe the demographic, clinical, and laboratory findings and investigate the distribution of M1 and M2 macrophages in CPAN. Methods This was a cross-sectional study involving fourteen patients with CPAN and nine control participants. Medical records were reviewed to determine demographic and clinical data, and laboratory findings. Skin biopsies obtained during disease manifestations were evaluated immunohistochemically. M1 macrophages were identified using STAT1 expression, and M2 macrophages were identified using CD163, CD206, and CMAF expression. Results CPAN was predominant in women, and the mean age of patients was 39 years. The main dermatological lesions were ulcers, subcutaneous nodules, and livedo. Increased lipoprotein(a) levels (28%) and a positive tuberculin skin test in 40% of the tested patients were our main laboratory findings. Direct immunofluorescence was positive in 88.9% of the cases. Immunohistochemical analysis revealed an increased percentage of M2 macrophages in CPAN patients compared with that in the control group. Conclusions This is a novel study on macrophage polarization in CPAN, where the number of cells expressing CD163 and CMAF was found to be increased. M2 macrophage predominance suggests an important role for the innate immune system in the pathophysiology of CPAN and may provide insights for potential therapeutic targets.