M1/M2 macrophages and associated mechanisms in congenital bicuspid aortic valve stenosis

The aim of this study was to observe macrophage infiltration in congenital bicuspid aortic valve (CBAV) stenosis. M1/M2 macrophage distribution, inflammatory cytokine expression and the role of M1 macrophages during CBAV stenosis were also explored. The experimental and control groups comprised 30 severely stenotic CBAVs and 30 severely stenotic tricuspid aortic valves (TAVs), respectively. Histological and morphological changes were assessed using hematoxylin-eosin (HE) staining and mRNA levels of vascular endothelial growth factor (VEGF) were examined using the quantitative polymerase chain reaction. Nonspecific, M1 and M2 macrophages were monitored using cluster of differentiation (CD)68, inducible nitric oxide synthase (iNOS) and CD163 staining, respectively. Endothelial nitric oxide synthase (eNOS), interleukin (IL)-10, arginase (Arg)-1 and macrophage colony-stimulating factor (M-CSF) were also examined using immunohistochemical staining. Of note, HE staining revealed a higher cell density and neovascularization was more common in CBAVs than TAVs. At the mRNA level, VEGF expression was two-fold higher in CBAVs relative to that in TAVs (P=0.02). Furthermore, CD68 and iNOS were significantly higher in CBAVs compared with TAVs (P=0.029 and 0.021, respectively), while CD163 expression was lower in CBAVs (P=0.033). In addition, eNOS expression was higher and Arg-1, IL-10 and M-CSF expression were lower in CBAVs compared with TAVs (all P<0.0001). The present study suggested that CBAVs are associated with a higher total and M1 macrophage density and a lower M2 macrophage density than TAVs, and that M1 macrophage infiltration may contribute to calcification of CBAVs.