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.