Nerve growth factor (NGF) is increased in intervertebral discs (IVDs) after disc injury and anti-NGF therapy improves low back pain in humans. Furthermore, M1 and M2 macrophage subtypes play a role in degenerative IVD injury. We examined M1 and M2 macrophage markers and NGF and cytokine expression in IVD-derived cells from control and IVD-injured mice for 28 days following injury. Ngf messenger RNA (mRNA) expression was increased 1 day after injury in injured compared with control mice, and persisted for up to 28 days. Flow cytometric analysis demonstrated that the proportion of F4/80+ CD11b+ cells was significantly increased from 1 day after injury for up to 28 days in injured compared to control mice. mRNA expression of M1 macrophage markers Tnfa, Il1b, and Nos2 was significantly increased 1 day after injury in injured compared to control mice, before gradually decreasing. At 28 days, no significant difference was observed in M1 markers. The M2a marker, Ym1, was significantly increased 1 day after injury in injured compared with control mice, while M2a and M2c markers Tgfb and Cd206 were significantly increased 7, 14, and 28 days after injury. Tumor necrosis factor α (TNF-α) and transforming growth factor β (TGF-β) stimulated Ngf mRNA and NGF protein expression in IVD cells. Our results suggest that TNF-α and TGF-β may stimulate NGF production under inflammatory and non-inflammatory conditions following IVD injury. As TNF-α and TGF-β are produced by M1 and M2 macrophages, further investigations are needed to reveal the role of macrophages in NGF expression following IVD injury. Our results may aid in developing treatments for IVD-related LBP pathology.

Macrophages, particularly M1 macrophages, produce proinflammatory cytokines and contribute to the degenerative process in injured intervertebral discs (IVDs). We previously showed that macrophages in both intact and injured IVDs increased following IVD injury. Resident macrophages and macrophages recruited from the peripheral blood have distinct roles in tissue. However, it remains to be determined whether increased macrophages derive from resident or recruited macrophages. We investigated the origin of M1 macrophages in injured IVDs using green fluorescent protein (GFP) transgenic bone marrow chimeric mice. The M1 macrophage marker, CD86, increased in both disc‐derived resident macrophages and bone marrow‐derived macrophages (BMMs) after lipopolysaccharide/interferon γ stimulation in vitro. Following IVD injury, the proportion of cells positive for the CD86 ligand, the F4/80 antigen, and the surface glycoprotein CD11b (CD86+ CD11b+ F4/80+) significantly increased in GFP+ populations at days 3, 7, and 14. In contrast, CD86+ CD11b+ F4/80+ cells in GFP− populations significantly increased on day 3, and thereafter decreased on days 7 and 14. The proportion of CD86+ CD11b+ F4/80+ cells in the GFP+ populations was significantly higher than that in the GFP− populations at days 1, 3, 7, and 14. Monocyte chemoattractant protein‐1 expression in disc‐derived macrophages, but not in BMMs, increased following interleukin‐1β stimulation. Our results suggest M1 macrophages following IVD injury originate from recruited macrophages. Resident macrophages may behave differently in IVD injury. The role of resident macrophages needs to be clarified. Further investigation is needed.

No abstract

Introduction There are few reports on body composition, particularly muscle mass, in patients with adolescent idiopathic scoliosis (AIS). The purpose of this study was to measure body composition including muscle mass and estimated bone mass of patients with AIS using bioelectrical impedance analysis (BIA) and to clarify the relationship between the degree of scoliosis and body composition. Methods The subjects were 210 girls (mean age 14.0 years, range 10-18 years) whose body composition was evaluated using BIA (Tanita MC-780). Body mass index (BMI), percent body fat (%BF), lean muscle mass index (LMI: muscle mass/height^2), and estimated bone mass index (eBoneMI: estimated bone mass/height^2) were determined by age and compared with those of previous reports. We divided 111 subjects whose bone maturation was complete into two groups for comparison of body composition metrics: those with Cobb angle <40° (moderate scoliosis group) and those with Cobb angle ≥40° (severe scoliosis group). The relationships between Cobb angle and each body composition parameter were evaluated. Results Age-adjusted BMI, %BF, and LMI tended to be low at all ages compared with means for the healthy Japanese population as previously reported. BMI, LMI, and eBoneMI were significantly lower in the severe scoliosis group compared with those in the moderate scoliosis group (p<0.05). In addition, all BMI, LMI, and eBoneMI were weakly correlated with Cobb angle (r= −0.20, −0.26, and −0.24). Conclusions On the basis of the results of this study, patients with AIS are thinner, with lower BMI, %BF, and LMI compared with healthy girls of the same age. Furthermore, factors such as lower BMI, lower muscle mass, and lower estimated bone mass were correlated with progressive scoliosis.

Macrophages produce proinflammatory cytokines in injured intervertebral discs (IVDs). We recently showed that macrophage‐derived inflammatory cytokines contribute to the production of pain‐related factors. However, the mechanism by which macrophages are recruited to injured IVDs has not been fully clarified. Here, we examined the expression dynamics of the chemokine CCL2 in a mouse IVD injury model and the mechanisms of its regulation. The percentage of macrophages increased from day 1 after injury and persisted up until day 28. At 1 and 3 days after injury, the expression of both Ccl2 messenger RNA (mRNA) and CCL2 protein was elevated in the IVD injury group, after which expression decreased to basal levels. Consistent with the increase in CCL2 expression, Ccr2 and Tnfa expression and various types of macrophages were also immediately elevated following disc injury. Further, tumor necrosis factor‐α (TNF‐α) stimulated Ccl2 mRNA and CCL2 protein expression in IVD cells in vitro. The expressions of M1 (Cd86 and Nos2) and M2a (Ym1) macrophage markers were all significantly elevated from  day 1 following injury in injured compared with control mice. Meanwhile, the expression of Cd206 (M2a and M2c marker) was significantly elevated on days 3, 7, 14, and 28 following injury. These results suggest that in IVD injury, TNF‐α stimulates CCL2, which, in turn, mediates the recruitment of macrophages with the recruited macrophages subsequently differentiating into M1 and M2 subtypes. CCL2 signaling may, therefore, play an important role in IVD pathology via macrophage recruitment. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:895‐901, 2020