[Inflammation and bone : Osteoimmunological aspects]

Differential expression of genes associated with hypoxia pathway on bone marrow stem cells in osteoporosis patients with different bone mass index

Background

This study aimed to assess gene expression changes associated with hypoxia pathway on bone marrow stem cells (BMSCs) and explore effects of bone mass index (BMI) on hypoxia pathway of osteoporosis (OP) patients.

Methods

Human BMSCs were isolated from bone marrow. Subjects were divided into healthy control group and OP group which was further divided into BMI <25 OP subgroup and BMI ≥25 OP subgroup.

Results

The genes downregulated in OP patients were involved in hypoxia pathway. Furthermore, those genes were even downregulated in OP patients BMI ≥25 subgroup than OP patients BMI <25 subgroup. The genes were expressed in response to decreased oxygen levels, and their functions are related to photoperiodism, positive regulation of myoblast differentiation, and entrainment of circadian clock by gene ontology (GO) analysis.

Conclusions

The expression of genes associated with hypoxia pathway on BMSCs in OP patients are lower than healthy subjects, and the expression of genes related to carbohydrate metabolism are lower in overweight OP patients than in normal weight OP patients. These results need further research.

[Osteoporosis-frequent comorbidity in patients with rheumatism]

Osteoporosis is one of the most frequent comorbidities in inflammatory rheumatic diseases. The immune system is substantially involved in the regulation of bone homeostasis and chronic inflammatory diseases influence this equilibrium at several levels. Besides the immunologically mediated inflammatory activity, immobility and glucocorticoid treatment are further risk factors for osteoporosis. Diagnostic and therapeutic recommendations are based on the current guidelines for osteoporosis of the Governing Body on Osteoporosis (DVO). Monitoring of the risk factors and bone mineral density testing is meaningful in each patient with a newly diagnosed rheumatic disease. In the case of a T-score ≤-1.5 a specific drug treatment with bisphosphonates, teriparatide or denosumab should be started together with optimizing preventive measures, such as reduction of glucocorticoid dosage, calcium and vitamin D intake and life style modifications. The risk of osteonecrosis of the jaw (ONJ) in patients with osteoporosis is small; however, there appears to be a significant increase in multiple vertebral fractures after discontinuation of denosumab.

IL-21 Enhances the Degradation of Cartilage Through the JAK-STAT Signaling Pathway During Osteonecrosis of Femoral Head Cartilage

This study aims to investigate the role of interleukin-21 (IL-21) in the mechanism of osteonecrosis of the femoral head. The serum content of IL-21 in patients with osteonecrosis of the femoral head (ONFH) and with femoral neck fracture (FNF) was examined by an enzyme-linked immunosorbent assay (ELISA). The cartilage specimens were stained with safranin-O. The expression of IL-21, tumor necrosis factor-α (TNF-α), cyclooxygenase (COX-2), a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4), matrix metalloproteinase-13(MMP-13), and aggrecan in the cartilage was detected, by immunohistochemistry and western blot analysis. Moreover, chondrocytes were treated with IL-21 (100 ng/mL) or PBS to examine the mRNA content of TNF-α, COX-2, IL-1β and NOS-2 by RT-PCR, and the protein levels of ADAMTS-4, MMP-13, and aggrecan by western blot analysis. The activity of the JAK-STAT pathway was determined in vitro after stimulation with IL-21. IL-21 serum levels were obviously higher in the ONFH patients and positively correlated with the severity of ONFH. There were more cells positive for inflammatory cytokines, including IL-21, TNF-α, and COX-2, in the cartilage of the ONFH patients than the FNF patients. The level of certain relative biomarkers, such as ADAMTS-4 and MMP-13, was higher and aggrecan was lower in the ONFH patients. The mRNA contents of TNF-α, COX-2, IL-1β, and NOS-2, as well as the levels of ADAMTS-4, MMP-13, were enhanced, and aggrecan decreased after stimulation with IL-21. The protein content of p-STAT-1, as well as p-STAT-3, also increased after IL-21 stimulation, and the highest level appeared at 30 min. Furthermore, the protein level of ADAMTS-4 and MMP-13 and the mRNA level of TNF-α, COX-2, IL-1β, and NOS-2 significantly decreased after stimulation with AG-490. IL-21 enhances cartilage inflammation to promote cartilage degradation through the JAK-STAT signaling pathway in the cartilage of ONFH patients.

[Changes in laboratory parameters of peripheral blood reflect cell and protein content of the immune system in bone resorption]

The aim of this study was to investigate dynamic changes in the laboratory parameters of peripheral blood, reflecting cellular and protein composition of the immune system in bone resorption. The study involved 108 patients with degenerative-dystrophic and posttraumatic disorders of the hip joint before and after joint replacement surgery. Half of the cases resulted in bone resorption. Dynamic monitoring was performed up to 7.5 years. It included flow cytometry (Coulter Epics XL, USA) and enzyme immunoassay to determine the amount of immunocompetent cells, immunoglobulin class M, A, G, E, cytokines, acute phase proteins (C-reactive protein, fibrinogen, albumin, ceruloplasmin, haptoglobin), parameters of neutrophil functional activity (lactoferrin cationic protein, myeloperoxidase, superoxide anion production). The results of the study revealed the leading role of haptoglobin, albumin, and IL-1b in bone resorption. The use of multiple regression analysis made it possible to propose criteria for prediction of bone resorption. In particular, the Ig G concentration one month after operation at a value of 13 or less g/l with a probability of 86.8% suggests a high risk of bone tissue destruction in the operated area of the joint (diagnostic sensitivity and diagnostic specificity of 85.7% and 86.9%, respectively). Determination of the IL-1b level also has a good predictive power: its concentration exceeding 191.2 pg/ml six month after surgery with the probability of 87.4% suggests destruction of bone tissue in the operated area of the joint (diagnostic sensitivity and diagnostic specificity of 87.2% and 88.1%, respectively).

Hip Osteonecrosis Is Associated with Increased Plasma IL-33 Level

The recently discovered IL-33 as an IL-1 cytokine family member has been proved to be specifically released from osteonecrotic bones. We aimed to investigate the potential role of IL-33 in the development of osteonecrosis of femoral head (ONFH). Forty patients diagnosed with ONFH and forty age-, sex-, and body mass index- (BMI-) matched healthy subjects were included in this prospective study between March 2016 and September 2016. A commercially available ELISA kit was used to test the level of plasma IL-33. The IL-33 levels were compared among different ARCO stages, CJFH types, and etiology groups. Plasma IL-33 levels were significantly higher in the ONFH patients than that in the control subjects. The levels of IL-33 did not differ significantly among the ONFH patients with different ARCO stages. The IL-33 levels of patients with CJFH type L3 were significantly higher than that of patients with types L1 and L2. No significant differences were observed in IL-33 levels between steroid-induced, alcohol-induced, and idiopathic patients. Our findings seem to indicate that IL-33 effects may be detrimental during ONFH, which appeared to be associated with the prognosis of ONFH. The IL-33 deserves particular attention in the pathogenesis of ONFH.