CCL11, a novel mediator of inflammatory bone resorption

Chemokines in Physiological and Pathological Bone Remodeling

The bone matrix is constantly remodeled by bone-resorbing osteoclasts and bone-forming osteoblasts. These two cell types are fundamentally different in terms of progenitor cells, mode of action and regulation by specific molecules, acting either systemically or locally. Importantly, there is increasing evidence for an impact of cell types or molecules of the adaptive and innate immune system on bone remodeling. Understanding these influences is the major goal of a novel research area termed osteoimmunology, which is of key relevance in the context of inflammation-induced bone loss, skeletal metastases, and diseases of impaired bone remodeling, such as osteoporosis. This review article aims at summarizing the current knowledge on one particular aspect of osteoimmunology, namely the impact of chemokines on skeletal cells in order to regulate bone remodeling under physiological and pathological conditions. Chemokines have key roles in the adaptive immune system by controlling migration, localization, and function of immune cells during inflammation. The vast majority of chemokines are divided into two subgroups based on the pattern of cysteine residues. More specifically, there are 27 known C-C-chemokines, binding to 10 different C-C receptors, and 17 known C-X-C-chemokines binding to seven different C-X-C receptors. Three additional chemokines do not fall into this category, and only one of them, i.e., CX3CL1, has been shown to influence bone remodeling cell types. There is a large amount of published studies demonstrating specific effects of certain chemokines on differentiation and function of osteoclasts and/or osteoblasts. Chemokine signaling by skeletal cells or by other cells of the bone marrow niche regulates bone formation and resorption through autocrine and paracrine mechanisms. In vivo evidence from mouse deficiency models strongly supports the role of certain chemokine signaling pathways in bone remodeling. We will summarize these data in the present review with a special focus on the most established subsets of chemokines. In combination with the other review articles of this issue, the knowledge presented here confirms that there is a physiologically relevant crosstalk between the innate immune system and bone remodeling cell types, whose molecular understanding is of high clinical relevance.

Serum C-C Motif Ligand 11/eotaxin-1 May Serve as a Candidate Biomarker for Postmenopausal Osteoporosis

Background

The chemokine C-C motif ligand 11, also known as eotaxin-1, has been identified as a novel mediator of inflammatory bone resorption. However, little is known regarding a potential role for CCL11/Eotaxin-1 in postmenopausal osteoporosis.

Objective

The scope of this study was to explore the relationship between serum CCL11/Eotaxin-1 concentrations and disease progression of postmenopausal females with osteoporosis.

Methods

A total of 83 postmenopausal women diagnosed with osteoporosis were enrolled. Meanwhile, 82 postmenopausal women with normal bone mineral density (BMD) and 85 healthy controls inner child-bearing age were enrolled as control. The Dual-energy X-ray absorptiometry was used to examine the BMDs at the femoral neck, lumbar spine 1-4 and total hip of all participants. Serum CCL11/Eotaxin-1 levels were examined by enzyme-linked immunosorbent assay. We also included inflammation marker interleukin-6 (IL-6) as well as a serum marker of bone resorption C-telopeptide cross-linked collagen type 1 (CTX-1). The Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) were recorded to evaluate the clinical severity in POMP females.

Results

Serum CCL11/Eotaxin-1 levels were significantly elevated in postmenopausal osteoporotic patients PMOP patients compared with PMNOP and healthy controls. We observed a significant negative correlation of serum CCL11/Eotaxin-1 levels with lumbar spine, femoral neck and total hip BMD. Furthermore, serum CCL11/ Eotaxin-1 concentrations were also positively related to the VAS and ODI scores. Last, serum CCL11/ Eotaxin-1 concentrations were positively associated with IL-6 and CTX-1 levels. These correlations remain significant after adjusting for age and BMI. Multivariate linear regression analysis demonstrated that CCL11/Eotaxin-1 could serve as an independent marker.

Conclusions

Serum CCL 11/Eotaxin-1 may serve as a candidate biomarker for postmenopausal osteoporosis. Therapeutics targeting CCL11/Eotaxin-1 and its related signalling way to prevent and slow progression of PMOP deserve further study.

Effect of small molecular weight soybean protein-derived peptide supplementation on attenuating burn injury-induced inflammation and accelerating wound healing in a rat model

The populations most afflicted by burn injuries have limited abilities to support the significant specialized requirements and costs for acute and long-term burn injury care. This article describes the results of optimizing the use of readily absorbed small molecular weight soybean protein enzymolysis-derived peptide to attenuate rat burn injury-induced inflammation and accelerate wound healing. A major full-thickness 30% total body surface area burn-injury rat model was utilized and the systemic white blood cell (WBC) counts, the relative level of stimulation index of respiratory burst, and the inflammatory markers procalcitonin (PCT), tumor necrosis factor-α (TNF-α), chemokine (C–C motif) ligand 3 (CCL-3), chemokine (C–C motif) ligand 11 (CCL-11) and interleukin-10 (IL-10) were assessed. The burn injury-induced neutrophil and macrophage immune cell infiltration of the cutaneous tissues was detected by immunohistochemical analysis of the protein markers myeloperoxidase (MPO) and cluster of differentiation 68 (CD-68). The local induction of the burn injury-induced toll-like receptor 4/nuclear factor kappa-light-chain-enhancer of activated B (TLR4/NF-κB) signaling pathway in the effected cutaneous tissues was determined by the quantification of the protein expression of TLR4 and phosphorylated NF-κB/p65 using Western blots. In addition, burn wound size and healing rate were assessed biweekly for 8 weeks by imaging and measuring the burn wound surface area, and the angiogenesis protein marker of cluster of differentiation 31 (CD-31) expression in cutaneous tissues was also detected by immunohistochemical analysis. The results showed that nutrient supplementation with optimized readily absorbed small molecular weight soybean protein-derived peptide resulted in a dramatic anti-inflammatory effect as evidenced by the significant increase in the burn injury-induced systemic white blood cell counts and their relative level of stimulation index of respiratory burst, reduction in the burn injury-induced activation of NF-κB transcriptional signaling pathways, significant reduction in the local burn injury-induced cutaneous infiltration of neutrophils and macrophages at all measured time points, reduction in wound size and improved rate of burn injury wound healing with increased CD-31 protein expression. These results indicated that dietary supplementation with small molecular weight soybean-derived peptides could be used as an adjunct therapy in burn injury management to reduce inflammation and improve overall patient outcomes.

The populations most afflicted by burn injuries have limited abilities to support the significant specialized requirements and costs for acute and long-term burn injury care.

Chemokine analysis as a novel diagnostic modality in the early prediction of the outcome of non-union therapy: a matched pair analysis

BACKGROUND

Despite the regenerative capability of skeletal tissue fracture, non-union is common. Treatment of non-unions remains challenging, and early determination of the outcome is impossible. Chemokines play an important role in promoting the formation of new bone and remodeling existing bone. Despite their importance regarding the regulation of bone biology, the potential of chemokines as biological markers reflecting osseous regeneration is unknown. The purpose of this study was to determine (1) if serum chemokine expression levels correlate with the outcome of non-union surgery and (2) if chemokine expression analysis can be used to identify patients at risk for treatment failure.

METHODS

Non-union patients receiving surgical therapy in our institution between March 2012 and March 2014 were prospectively enrolled in a clinical observer study. Regular clinical and radiological follow-up was conducted for 12 months including collection of blood during the first 12 weeks. Based on the outcome, patients were declared as responders or non-responders to the therapy. To minimize biases, patients were matched (age, sex, body mass index (BMI)) and two groups of patients could be formed: responders (R, n = 10) and non-responders (NR, n = 10). Serum chemokine expression (CCL-2, CCL-3, CCL-4, CXCL-10, CCL-11, and interferon gamma (IFN-γ)) was analyzed using Luminex assays. Data was compared and correlated to the outcome.

RESULTS

CCL-3 expression in NR was significantly higher during the course of the study compared to R (p = 0.002), and the expression pattern of CCL-4 correlated with CCL-3 in both groups (NR: p < 0.001 and r = 0.63). IFN-γ expression in NR was continuously higher than in R (p < 0.001), and utilization of CCL-3 and IFN-γ serum expression levels 2 weeks after the treatment resulted in a predictive model that had an AUC of 0.92 (CI 0.74-1.00).

CONCLUSION

Serum chemokine expression analysis over time is a valid and promising diagnostic tool. The chemokine expression pattern correlates with the outcome of the Masquelet therapy of lower limb non-unions. Utilization of the serum analysis of CCL-3 and IFN-γ 2 weeks after the treatment resulted in an early predictive value regarding the differentiation between patients that are likely to heal and those that are prone to high risk of treatment failure.

Serum CCL11 level is associated with radiographic spinal damage in patients with ankylosing spondylitis

The clinical significance of C-C motif chemokine11 (CCL11) in bone metabolism in ankylosing spondylitis (AS) is not clearly elucidated. Thus, this cross-sectional study aimed to compare serum levels of CCL11 between patients with AS and healthy controls and to investigate the relationship between serum levels of CCL11 and radiographic spinal damage in patients with AS. We consecutively recruited 55 male patients with AS and 26 age- and sex-matched healthy controls. Serum levels of CCL11, tumor necrosis factor-α (TNF-α), interleukin-17, and Dickkopf-1 (DKK-1) were measured with commercially available enzyme-linked immunosorbent assay kits. Radiographs were scored according to the modified Stoke ankylosing spondylitis spine score (mSASSS), and syndesmophytes were defined as mSASSS ≥ 2. The serum levels of CCL11 in AS patients with syndesmophytes were significantly higher than those in AS patients without syndesmophytes (p = 0.007) and healthy controls (p = 0.006). In AS patients, the serum levels of CCL11 were significantly and positively correlated with mSASSS (p = 0.006), number of syndesmophytes (p = 0.029). After adjusting for confounding factors, elevated serum levels of CCL11 were associated with increased mSASSS (β = 0.007, p = 0.03) and higher risk for the presence of syndesmophytes (OR 2.34 per 50 pg/ml increase, p = 0.012) in AS patients. We found that the serum level of CCL11 was associated with structural damage in patients with AS, suggesting that CCL11 may serve as a promising biomarker for new bone formation in AS.