Sequential CCL2 Expression Profile After Disc Injury in Mice

BMC Musculoskelet Disord

et al. 2021

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Background Intervertebral disc (IVD) degeneration is a major cause of low back pain (LBP). Following disc injury, nerve growth factor (NGF) concentrations rise in IVDs, and anti-NGF therapy has been shown to attenuate LBP in humans. Increased levels of tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) in degenerative IVDs and in in vitro studies suggest that these factors promote NGF production. However, whether these factors regulate NGF in vivo remains unclear. Thus, we studied NGF regulation in a mouse model of IVD injury. Methods After inducing IVD injury, we examined mRNA levels of Tnfa, Tgfb, and Ngf in IVDs from control and IVD-injured mice across 7 days. To do this, we used magnetic cell separation to isolate CD11b ( +) (macrophage-rich) and CD11b (-) (IVD cell-rich) cell fractions from injured IVDs. To study the effect of TNF-α on Ngf expression, we examined Ngf expression in injured IVDs from C57BL/6 J and Tnfa-knockout (KO) mice (C57BL/6 J background). To study the effect of TGF-β on Ngf expression, C57/BL6J mice were given an intraperitoneal injection of either the TGF-β inhibitor SB431542 or DMSO solution (vehicle) one and two days before harvesting IVDs. Results mRNA expression of Tnfa, Tgfb, and Ngf was significantly increased in injured IVDs. Tnfa was predominantly expressed in the CD11b ( +) fraction, and Tgfb in the CD11b (-) fraction. Ngf expression was comparable between CD11b ( +) and CD11b (-) fractions, and between wild-type and Tnfa-KO mice at post-injury day (PID) 1, 3, and 7. SB431542 suppressed TGF-β-mediated Ngf expression and NGF production in vitro. Further, administration of SB431542 significantly reduced Ngf expression in IVDs such that levels were below those observed in vehicle-treated animals at PID3 and PID7. Conclusion A TGF-β inhibitor reduced Ngf expression in a mouse model of IVD injury, suggesting that TGF-β may regulate NGF expression in vivo.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

TGF-β regulates nerve growth factor expression in a mouse intervertebral disc injury model

Yokozeki

Uchida

BMC Musculoskelet Disord

et al. 2021

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“…We examined the expression of Cd11b (macrophage marker), Cd206 (M2 maker), and Tgfb genes, which encode CD11b, CD206, and TGF-β protein, respectively, based on previous reports [9,13,21]. Primers were generated according to our previous report [9,13,21]. The delta-delta Ct method and the housekeeping gene Gapdh were used to determine relative mRNA expression levels of the genes of interest.…”

Section: 3mentioning

confidence: 99%

“…Various kinds of macrophages, including resident macrophages and recruited macrophages, are present in degenerated IVDs [7][8][9][10]. Recruited macrophages differentiate into proinflammatory phenotype M1 macrophages, which are thought to induce inflammation in IVDs [7].…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, tissue-specific macrophages, known as resident macrophages, exist in a variety of tissues [10][11][12][13][14]. Recent studies have demonstrated that resident macrophages exist in mouse and human IVDs [9,10,13]. Resident macrophages exhibit M2 phenotype and play an important role in promoting regeneration, inflammation resolution, and remodeling [15].…”

Section: Introductionmentioning

confidence: 99%

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Reduced TGF-β Expression and CD206-Positive Resident Macrophages in the Intervertebral Discs of Aged Mice

Yokozeki

BioMed Research International

Miyagi

et al. 2021

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Age is a key factor in intervertebral disc (IVD) degeneration; however, the changes that occur in IVDs with age are not fully understood. Tissue-resident macrophages are critical for tissue homeostasis and are regulated by transforming growth factor- (TGF-) β. We examined changes in the proportion of resident macrophages in young versus aged mice and the role of TGF-β in regulating resident macrophages in IVDs. IVDs were harvested from 4-month (young) and 18-month-old (aged) C57BL/6J mice. The proportion of macrophages in IVDs was determined using flow cytometry ( n = 5 for each time point) and the expression of Cd11b, Cd206, and Tgfb genes, which encode CD11b, CD206, and TGF-β protein, respectively, using real-time PCR. To study the role of TGF-β in the polarization of resident macrophages, resident macrophages isolated from IVDs from young and aged mice were treated with recombinant TGF-β with and without a TGF-β inhibitor (SB431542). Additionally, SB431542 was intraperitoneally injected into young and aged mice, and Cd206 expression was examined using real-time PCR ( n = 10 for each time point). The proportion of CD11b+ and CD11b+ CD206+ cells was significantly reduced in aged versus young mice, as was Cd11b, Cd206, and Tgfb expression. TGF-β/IL10 stimulation significantly increased the expression of Cd206, an M2 macrophage marker, in disc macrophages from both young and aged mice. Meanwhile, administration of a TGF-β inhibitor significantly reduced Cd206 expression compared to vehicle control in both groups. Conclusion. Resident macrophages decrease with age in IVDs, which may be associated with the concomitant decrease in TGF-β. Our findings provide new insight into the mechanisms of age-related IVD pathology.

Investigation of resident and recruited macrophages following disc injury in mice

Journal Orthopaedic Research

Uchida

Miyagi

et al. 2020

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.