The Dynamic Feature of Macrophage M1/M2 Imbalance Facilitates the Progression of Non-Traumatic Osteonecrosis of the Femoral Head

Abstract

Non-traumatic osteonecrosis of the femoral head (NONFH) remains a common refractory disease with poorly understood pathogenesis. Macrophage M1/M2 imbalance and chronic inflammatory microenvironment have been suggested to be closely related to osteonecrosis. Here we describe direct visual evidence for the involvement of dynamic changes in macrophages and the chronic inflammatory microenvironment in human NONFH. Osteonecrosis induces inflammatory responses and macrophage enrichment in the reparative area, and the number of inflammatory cells and macrophages falls during progressive-to end-stage NONFH. Multiplex immunohistochemistry demonstrated that macrophage M1/M2 ratio increased from 3 to 10 during progressive-to end-stage. During the progressive-stage, new blood vessels formed in the reparative area, M2 macrophages accumulated in perivascular (M1/M2 ratio ∼0.05), while M1 macrophages were enriched in avascular areas (M1/M2 ratio ∼12). Furthermore, inflammatory cytokines were detected in synovial fluid and plasma using cytometric bead arrays. Interleukin (IL)-6 and IL-1β were persistently enriched in synovial fluid compared to plasma in patients with NONFH, and this difference was confirmed by immunohistochemistry staining. However, only IL-6 levels in plasma were higher in patients with progressive-stage NONFH than in osteoarthritis. Moreover, fibrosis tissues were observed in the necrotic area in progressive-stage and end-stage NONFH based on Sirius Red staining. Together, these findings indicate that macrophage M1/M2 imbalance facilitates the progression of NONFH, a chronic inflammatory disease characterized by chronic inflammation, osteonecrosis and tissue fibrosis in the local lesion. Inhibiting inflammation, promoting the resolution of inflammation, switching macrophages to an M2 phenotype, or inhibiting their adoption of an M1 phenotype may be useful therapeutic strategies against NONFH.

A comparative in vitro and in vivo study of porcine‐ and bovine‐derived non‐cross‐linked collagen membranes

“…M1 macrophages release pro‐inflammatory cytokines that can cause tissue damage. To prevent tissue damage, the differentiation of M2 macrophages increases 51 . Study has shown that the rapid transition of macrophage polarization from M1 to M2 is beneficial for successful implantation of material 52 .…”

“…To prevent tissue damage, the differentiation of M2 macrophages increases. 51 Study has shown that the rapid transition of macrophage polarization from M1 to M2 is beneficial for successful implantation of material. 52 In this study, we calculated the M2/M1 ratio around the two implanted materials.…”

Polarization Behavior of Bone Macrophage as Well as Associated Osteoimmunity in Glucocorticoid-Induced Osteonecrosis of the Femoral Head

“…Inflammatory cytokines such as TNF-α, IL-6 and IL-1β were detected in synovial fluid and plasma of patients with GIONFH. 64 During the progression of GIONFH, large numbers of chronic inflammatory cells may infiltrate into the peripheral blood and necrotic zone. 65 Multiple studies [66][67][68] evaluated immune infiltration in serum by analyzing GSE123568 which enrolled thirty patients with GIONFH and ten healthy controls, and found decreased infiltration of memory B cells and activated dendritic cells.…”

The role of immune cells in modulating chronic inflammation and osteonecrosis

“…In either case, an excessive or insufficient inflammatory reaction eventually translates to chronic inflammation, which is the bridge between bone injury and osteonecrosis. Chronic inflammation hinders bone repair and regeneration following bone injury, which finally leads to osteonecrosis ( 10 , 14 , 16 , 35 – 40 ). ( Figure 2 )…”

“…Animal models of osteonecrosis showed high numbers of macrophage infiltration in areas with osteonecrosis, high ratio of M1 to M2 macrophages, and significant upregulation of pro-inflammatory factors TGF-β, IL-1β and IL-6 ( 57 – 59 ). Interestingly, a recent study of specimens from patients with non-traumatic ONFH also found that the main macrophage subset in the osteonecrosis area had the M1 phenotype, the local microenvironment was enriched with IL-1β and IL-6, and the ratio of M1 to M2 macrophages was significantly increased as osteonecrosis progressed ( 35 ). Inhibiting M1 macrophage polarization and reducing the M1/M2 ratio in femoral head and jaw reduced the secretion of local pro-inflammatory factors and the apoptosis of bone cells caused by inflammation, relieving steroid-induced osteonecrosis of the femoral head (SONFH) and bisphosphonate-related osteonecrosis of the jaw to some extent ( 60 , 61 ).…”