Identifying the causal relationship between immune factors and osteonecrosis: a two-sample Mendelian randomization study.

A wealth of evidence intimates a profound connection between the immune system and osteonecrosis, albeit the specific immune factors underlying this connection remain largely veiled. A bidirectional Mendelian randomization (MR) study was conducted based on genome-wide association study summary data to identify causal links between 731 immune factors and osteonecrosis including drug-induced osteonecrosis. Preliminary MR analysis was accomplished utilizing the inverse-variance weighted method under a multiplicative random effects model, and heterogeneity and potential horizontal pleiotropy were evaluated through Cochrane's Q-test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis. Upon false discovery rate correction, the gene-predicted level of one immune factor (CD62L - monocyte %monocyte) exhibited a significant positive correlation with osteonecrosis, while eight immune traits associated with monocytes, dendritic cells, and NK cells demonstrated significant causal effects with drug-induced osteonecrosis. Reverse MR revealed no significant correlations. This MR research provides genetic evidence for the causal associations between a broad spectrum of immune factors and osteonecrosis. Such a study aids in unraveling the intricate interaction patterns between the immune and skeletal systems, elucidating the pathogenesis of osteonecrosis, and identifying potential novel therapeutic approaches.

Pathological mechanism of joint destruction in haemophilic arthropathy.

Haemophilic arthropathy (HA), caused by intra-articular haemorrhage, is one of the most common complications in patients with haemophilia. Factor replacement therapy provides missing coagulation factors to prevent children with haemophilia from joint bleeding and decreases their risk for HA. However, haemophilia patients in developing countries are still suffering from HA due to insufficient replacement therapy. Symptoms such as pain and activity limitations caused by HA seriously affect the functional abilities and quality of life of patients with HA, causing a high disability rate in the haemophilia cohort. The pathological mechanism of HA is complicated because the whole pathological mainly involves hypertrophic synovitis, osteopenia, cartilage and bone destruction, and these pathological changes occur in parallel and interact with each other. Inflammation plays an important role in the whole complex pathological process, and iron, cytokines, growth factors and other factors are involved. This review summarizes the pathological mechanism of HA to provide background for clinical and basic research.

CD4+ T Cell Profile and Activation Response in Sickle Cell Disease Patients with Osteonecrosis.

Recent evidence suggests that abnormalities involving CD4+T lymphocytes are associated with the pathophysiology of osteonecrosis (ON); however, few studies have addressed the CD4+T cells in ON related to sickle cell disease (SCD/ON). In addition, T cells producing multiple cytokines simultaneously are often present in the inflammatory milieu and may be implicated in the immune response observed in SCD/ON. In the present study, we aimed to characterize the functional status of CD4+T cells in SCD by simultaneously determining the frequency of IFN-γ +, IL-4+, and IL-17+ CD4+T in cell cultures under exogenous stimuli. Peripheral blood mononuclear cells (PB-MNCs) from 9 steady-state SCD patients, 15 SCD/ON patients, and 19 healthy controls had functional status of CD4+T cells analyzed. Bone marrow mononuclear cells (BM-MNCs) from 24 SCD/ON patients (SCD BM) and 18 patients with ON not related to SCD (non-SCD BM) were also analyzed. We found that PB-MNC of SCD patients with or without ON presented significantly reduced TCD4+, TCD8+, and TCD4+ naïve cell frequencies and increased frequency of circulating CD4+T cells able to simultaneously produce IFN-γ +/IL4+ and IL-17+/IL4+ compared to healthy controls. Conversely, the polyclonal stimulation of BM-MNC induced an increased frequency of CD4+IFN-γ + and CD4+IL-17+ in SCD BM compared to non-SCD BM. The increased proportion of CD4+ T cells able to produce a broad spectrum of proinflammatory cytokines after a strong stimulus indicates that the immune system in SCD/ON patients presents an expressive pool of partially differentiated cells ready to take on effector function. It is possible that this increased subpopulation may extend to inflammatory sites of target organs and may contribute to the maintenance of inflammation and the pathophysiology of osteonecrosis in sickle cell disease.

Determination of the molecular mechanism by which macrophages and γδ-T cells contribute to ZOL-induced ONJ.

OBJECTIVE: This study aims to explore the molecular mechanism of macrophages and γδ-T cells in the ZOL drug-induced osteonecrosis of jaws based on the IFN-γ involved osteoblast differentiation signaling pathway. RESULTS: The number and apoptotic rate of CD11b+Gr1hi cells and γδ-T cells in the ONJ group were significantly higher. The TNF-α, IL-1ß, IFN-γ, CCL3, CCL4, IL-12 and IL-13 levels were significantly higher in the ONJ group. The expression of CTSK and FGFR3 was lower in the ONJ group, but was higher in the NF-κB and ERBB2IP group. CONCLUSION: The proliferation of macrophages and γδ-T cells promote the inflammation in ZOL-induced jaw necrosis. METHODS: A total of 20 patients with osteonecrosis of the jaw from January 2016 to March 2018 were collected and assigned into the observation group, while 20 healthy subjects were assigned into the control group. Furthermore, 40 SD rats were selected and assigned into observation group, while 10 non-treatment SD rats were selected and assigned as controls. The distribution and proportion of CD11b+Gr1hi cells and γδ-T cells in the necrotic tissues of the jaw were analyzed. Then, the TNF-α, IL-1ß, IFN-γ, CCL3, CCL4, IL-12 and IL-13 levels were measured. Afterwards, the expression of CTSK, FGFR3, NF-κB and ERBB2IP in the necrotic tissues of the jaw in the animal models were analyzed.

Role of dendritic cell-mediated immune response in oral homeostasis: A new mechanism of osteonecrosis of the jaw.

Dendritic cells are an important link between innate and adaptive immune response. The role of dendritic cells in bone homeostasis, however, is not understood. Osteoporosis medications that inhibit osteoclasts have been associated with osteonecrosis, a condition limited to the jawbone, thus called medication-related osteonecrosis of the jaw. We propose that disruption of the local immune response renders the oral microenvironment conducive to osteonecrosis. We tested whether zoledronate (Zol) treatment impaired dendritic cell (DC) functions and increased bacterial load in alveolar bone in vivo and whether DC inhibition alone predisposed the animals to osteonecrosis. We also analyzed the role of Zol in impairment of differentiation and function of migratory and tissue-resident DCs, promoting disruption of T-cell activation in vitro. Results demonstrated a Zol induced impairment in DC functions and an increased bacterial load in the oral cavity. DC-deficient mice were predisposed to osteonecrosis following dental extraction. Zol treatment of DCs in vitro caused an impairment in immune functions including differentiation, maturation, migration, antigen presentation, and T-cell activation. We conclude that the mechanism of Zol-induced osteonecrosis of the jaw involves disruption of DC immune functions required to clear bacterial infection and activate T cell effector response.

The Role of Immune Regulatory Cells in Nontraumatic Osteonecrosis of the Femoral Head: A Retrospective Clinical Study.

The immunologic factors have been implicated in the pathogenesis of osteonecrosis. We aimed to investigate the potential role of immune regulatory cells in the development of osteonecrosis of femoral head (ONFH). Sixty-seven patients diagnosed with ONFH and fifty-eight age-, height-, and weight-matched healthy subjects were included in this retrospective study between September 2015 and September 2018. The flow cytometry was used to test the count, percentage, and ratio of T and B lymphocyte subsets in peripheral blood. The T and B lymphocyte levels were compared among different ARCO stages, CJFH types, and etiology groups. The total lymphocyte count, CD3+T cells, Ts cells (CD3+CD8+), B-1 cell count, and B-1 cells (CD5+CD19+) were significantly higher in the patients with ONFH than those in the control subjects. The percentage of T lymphocytes in the patients with ARCO IV stage was significantly smaller than that in the ONFH patients with ARCO II and III stages. The percentage of inhibitory T lymphocytes in patients with CJFH type L3 was significantly smaller than that in the patients with types L1 and L2. In terms of the different ONFH etiologies, the total lymphocyte count and Ts cells (CD3+CD8+) were significantly lower in the ONFH patients induced by excessive alcohol intake than those in the idiopathic ONFH patients. Our results seem to indicate that immune regulatory cells, such as T and B lymphocytes, play an important role in the pathogenesis of ONFH. The development and progression of ONFH may be associated with immune system imbalance.

A high-fat diet aggravates osteonecrosis through a macrophage-derived IL-6 pathway.

Inflammation plays an important role in osteonecrosis. Obesity, a risk factor for osteonecrosis, leads to a chronic inflammatory status. We hypothesized that inflammation mediated the effects of obesity on osteonecrosis and tested our hypothesis in a mouse model of osteonecrosis. We fed mice with a high-fat diet (HFD) for 12 weeks before osteonecrosis induction by methylprednisolone and examined bone structure and IL-6 expression. Then we investigated the effects of IL-6 deletion in mice with osteonecrosis on the HFD. Next, we isolated bone marrow cells and determined the cell types responsible for HFD-induced IL-6 secretion. Finally, we investigated the roles of macrophages and macrophage-driven IL-6 in HFD-mediated effects on osteonecrosis and osteogenesis of bone marrow stromal cells (BMSCs). The HFD lead to exacerbated destruction of the femoral head in mice with osteonecrosis and increased IL-6 expression in macrophages. Il-6 knockout or macrophage depletion suppressed the effects of the HFD on bone damage. When co-cultured with macrophages isolated from HFD-fed mice with osteonecrosis, BMSCs showed reduced viability and suppressed osteogenic differentiation. Our results suggest that macrophage-driven IL-6 bridges obesity and osteonecrosis and inhibition of IL-6 or depletion of macrophage may represent a therapeutic strategy for obesity-associated osteonecrosis.

Current Understanding of the Pathophysiology of Osteonecrosis of the Jaw.

PURPOSE OF REVIEW: Osteonecrosis of the jaw (ONJ) is a rare and severe necrotic bone disease reflecting a compromise in the body's osseous healing mechanisms and unique to the craniofacial region. Antiresorptive and antiangiogenic medications have been suggested to be associated with the occurrence of ONJ; yet, the pathophysiology of this disease has not been fully elucidated. This article raises the current theories underlying the pathophysiology of ONJ. RECENT FINDINGS: The proposed mechanisms highlight the unique localization of ONJ. The evidence-based mechanisms of ONJ pathogenesis include disturbed bone remodeling, inflammation or infection, altered immunity, soft tissue toxicity, and angiogenesis inhibition. The role of dental infections and the oral microbiome is central to ONJ, and systemic conditions such as rheumatoid arthritis and diabetes mellitus contribute through their impact on immune resiliency. Current experimental studies on mechanisms of ONJ are summarized. The definitive pathophysiology is as yet unclear. Recent studies are beginning to clarify the relative importance of the proposed mechanisms. A better understanding of osteoimmunology and the relationship of angiogenesis to the development of ONJ is needed along with detailed studies of the impact of drug holidays on the clinical condition of ONJ.

TGF­ß1 expression in adults with non­traumatic osteonecrosis of the femoral head.

Non-traumatic osteonecrosis of the femoral head (NONFH) is a common clinical osteoarthropathy. The present study aimed to investigate the association between transforming growth factor ß1 (TGF­ß1) and NONFH. Femoral head specimens were collected from patients with NONFH. Patients with traumatic osteonecrosis served as the control. Hematoxylin and eosin (H&E) staining was used to visualize the bone tissue architecture. Immunohistochemistry and densitometry were performed to quantify TGF­ß1 expression in tissues. Flow cytometry was used to detect cluster of differentiation (CD)3+, CD4+ and CD8+ cells, and the ratio of CD4+ to CD8+ T cells in the peripheral blood. H&E staining revealed osteonecrosis, disintegration of osteocytes with karyopyknosis and karyorrhexis, loss of osteocyte lacunae, aberrantly arranged circumferential lamellae, as well as dissolution of the lamellae and subtle osteogenesis in the experimental group, as opposed to the control group. Immunohistochemistry revealed that the expression of TGF­ß1 was significantly reduced in the experimental group (P<0.01). Further, the NONFH group had a decrease in the CD3+ and CD4+ cell populations (P<0.05 and P<0.01, respectively), an increase in the CD8+ cell population (P<0.05), as well as a reduction in the ratio of CD4+ to CD8+ cells (P<0.01). The present study indicated that TGF­ß1 expression was reduced in NONFH. This was associated with impaired repairing capacity of the femoral head and dysregulated subsets of T­lymphocytes and possible immune functions.

Update on the pathogenesis and treatment of childhood-onset systemic lupus erythematosus.

PURPOSE OF REVIEW: This article will provide an update of studies published in the last year regarding epidemiology, pathogenesis, major disease manifestations and outcomes, and therapies in childhood-onset systemic lupus erythematosus (cSLE). RECENT FINDINGS: Recent studies on cSLE epidemiology supported previous findings that cSLE patients have more severe disease and tend to accumulate damage rapidly. Lupus nephritis remains frequent and is still a significant cause of morbidity and mortality. In the past year unfortunately there were no new reproducible, biomarker studies to help direct therapy of renal disease. However, some progress was made in neuropsychiatric disease assessment, with a new and promising automated test to screen for cognitive dysfunction reported. There were no prospective interventional treatment trials designed for patients with cSLE published in the last year, but some studies involving children are currently active and might improve the therapeutic options for patients with cSLE. SUMMARY: There is a need to get a better understanding of pathogenesis and identify new biomarkers in cSLE to more accurately predict outcomes. New insights into characterization of different clinical manifestations may enable to optimize individual interventions and influence the prognosis.

In vivo monitoring of activated macrophages and neutrophils in response to ischemic osteonecrosis in a mouse model.

Ischemic osteonecrosis (IO) is caused by disruption of the blood supply to bone. It is a debilitating condition with pathological healing characterized by excessive bone resorption and delayed osteogenesis. Although the majority of research has focused on the role of osteoblasts and osteoclasts in the disease progression, we hypothesize that innate immune cells, macrophages and neutrophils, play a significant role. With the recent development of real-time imaging probes for neutrophils and macrophages, the purpose of this study was to investigate the kinetic immune cell response in a mouse model of IO. Our results show that induction of IO leads to a significant accumulation of activated neutrophils and macrophages at the affected tissue by 48 h after surgery. Additionally, the accumulation of these immune cells remained elevated in comparison to sham controls for up to 6 weeks, indicative of chronic inflammation. Immunohistochemistry confirmed the immune cell infiltration into the necrotic bone marrow and the increased presence of TNFα-positive cells, demonstrating, for the first time, a direct response of these cells to ischemia induced necrotic bone. These new findings support a hypothesis that IO is an osteoimmunologic condition where innate immune cells play a significant role in the chronic inflammation.

From mishap to model: The origins and utility of experimental autoimmune encephalomyelitis.

This special edition of the Biomedical Journal focuses on experimental autoimmune encephalomyelitis, and includes three reviews showing how this model has greatly facilitated our understanding of the pathophysiology of multiple sclerosis. We also highlight a small single center study which suggests that the use of calcium bone substitutes during core decompression surgery may do more harm than good. Finally, we see how policy changes affect the management of fungal infections in immunocompromised patients and we learn about antibiotic resistance among strains of Streptococcus agalactiae circulating in Taiwan.

Long-term survival and late effects among one-year survivors of second allogeneic hematopoietic cell transplantation for relapsed acute leukemia and myelodysplastic syndromes.

We analyzed the outcomes of patients who survived disease-free for 1 year or more after a second allogeneic hematopoietic cell transplantation (HCT) for relapsed acute leukemia or myelodysplastic syndromes between 1980 and 2009. A total of 1285 patients received a second allogeneic transplant after disease relapse; among these, 325 were relapse free at 1 year after the second HCT. The median time from first to second HCT was 17 and 24 months for children and adults, respectively. A myeloablative preparative regimen was used in the second transplantation in 62% of children and 45% of adult patients. The overall 10-year conditional survival rates after second transplantation in this cohort of patients who had survived disease-free for at least 1 year was 55% in children and 39% in adults. Relapse was the leading cause of mortality (77% and 54% of deaths in children and adults, respectively). In multivariate analyses, only disease status before second HCT was significantly associated with higher risk for overall mortality (hazard ratio, 1.71 for patients with disease not in complete remission before second HCT, P < .01). Chronic graft-versus-host disease (GVHD) developed in 43% and 75% of children and adults after second transplantation. Chronic GVHD was the leading cause of nonrelapse mortality, followed by organ failure and infection. The cumulative incidence of developing at least 1 of the studied late effects within 10 years after second HCT was 63% in children and 55% in adults. The most frequent late effects in children were growth disturbance (10-year cumulative incidence, 22%) and cataracts (20%); in adults they were cataracts (20%) and avascular necrosis (13%). Among patients with acute leukemia and myelodysplastic syndromes who receive a second allogeneic HCT for relapse and survive disease free for at least 1 year, many can be expected to survive long term. However, they continue to be at risk for relapse and nonrelapse morbidity and mortality. Novel approaches are needed to minimize relapse risk and long-term transplantation morbidity in this population.

[Cytokines level in patients with drug-induced jaw necrosis].

The study included 15 patients with purulent inflammatory diseases of maxillofacial area and 25 patients with facial bone necrosis induced by synthetic drugs. Pro- and anti-inflammatory cytokines levels in saliva and wound fluid were analyzed in two groups. The results proved cytokines to play important role in jaw necrosis induced by drugs containing red phosphorus.

Avascular necrosis of bone after allogeneic hematopoietic cell transplantation in children and adolescents.

We conducted a nested case-control study within a cohort of 6244 patients to assess risk factors for avascular necrosis (AVN) of bone in children and adolescents after allogeneic transplantation. Eligible patients were ≤21 years of age, received their first allogeneic transplant between 1990 and 2008 in the United States, and had survived ≥ 6 months from transplantation. Overall, 160 patients with AVN and 478 control subjects matched by year of transplant, length of follow-up and transplant center were identified. Patients and control subjects were confirmed via central review of radiology, pathology, and/or surgical procedure reports. Median time from transplant to diagnosis of AVN was 14 months. On conditional logistic regression, increasing age at transplant (≥5 years), female gender, and chronic graft-versus-host disease (GVHD) were significantly associated with increased risks of AVN. Compared with patients receiving myeloablative regimens for malignant diseases, lower risks of AVN were seen in patients with nonmalignant diseases and those who had received reduced-intensity conditioning regimens for malignant diseases. Children at high risk for AVN include those within the age group where rapid bone growth occurs as well as those who experience exposure to myeloablative conditioning regimens and immunosuppression after hematopoietic cell transplantation for the treatment of GVHD. More research is needed to determine whether screening strategies specifically for patients at high risk for developing AVN with early interventions may mitigate the morbidity associated with this complication.

Fracture union following internal fixation in the HIV population.

INTRODUCTION: HIV is thought to be associated with increased rates of fracture non-union. We report on a prospective cohort of 96 HIV positive patients with 107 fractures that required internal fixation. The CD4 count was measured and patients were reviewed until eventual clinical or radiological union or non-union was established. RESULTS: Four percent of fractures (4 out of 100) failed to unite. Three patients required one further procedure to induce union, and two developed avascular necrosis. The CD4 count was not related to fracture union. CONCLUSION: Contrary to previous assumptions, this study suggests that HIV infection does not increase rates of non-union in surgically managed fractures.

Atraumatic osteonecrosis of the humeral head after influenza A-(H1N1) v-2009 vaccination.

In the recent pandemic influenza A-(H1N1) v-2009 vaccination campaign, adjuvanted vaccines have been used because of their antigen-sparing effect. According to available reports, the rate of severe vaccination reactions has not increased, as compared with previous seasonal influenza vaccinations. Here we describe an adult female patient who was vaccinated with an AS03 adjuvanted split-virus vaccine injected into the left arm. She experienced a prolonged and painful local reaction for 4 weeks. During this time, persistent incapacitating pain shifted into the left shoulder. Magnetic resonance imaging (MRI) at the injection site detected atraumatic humeral head osteonecrosis in conjunction with bursitis of the rotator cuff region. Clinical and laboratory examination revealed no other underlying disease. Using analgetic medication and physical therapy, resting pain completely remitted within the following 14 weeks. Pain on exertion declined within the following 6 months. Atraumatic osteonecrosis, a relatively rare disorder which initially presents non-specific clinical symptoms, has never been associated with parenteral influenza vaccination. Although the available data cannot establish a causal relationship, our patient's clinical course - with a continuous transition from increased local post-vaccination reactions to symptoms of a severe shoulder lesion with osteonecrosis - raises the question of a pathogenetic link. Considering the vascular pathogenesis of osteonecrosis, we hypothesize that our patient's enhanced local immunologic reaction may have led to regional vasculitis as the cause of bone destruction. As mild forms of osteonecrosis may have escaped previous clinical attention, it is the purpose of our report to increase awareness of this exceptional event as a possible side effect of parenteral adjuvanted vaccination.

Current concepts on the pathogenesis and natural history of steroid-induced osteonecrosis.

The pathophysiology of non-traumatic osteonecrosis is more complex than that of traumatic osteonecrosis, and corticosteroid-induced osteonecrosis presents the greatest challenge because of the multiple effects of corticosteroids on multi-system pathways; these pathways include the effects of corticosteroids on osteoblast differentiation, osteoblast and osteoclast apoptosis, lipid metabolism, coagulation pathways, and calcium metabolism. These pathways are frequently interrelated with each other, which makes the pathogenesis even more difficult to understand. Host factors and underlying disease have been shown to play a significant role in the risk of developing osteonecrosis, and our understanding of the pathogenesis must be able to explain why some patients are at greater risk than others. Identification of genetic variants that convey additional risk will also help to personalize the way we deliver care, both in the prevention and treatment of osteonecrosis. Further understanding of the intricate immunologic and genetic pathways contributing to osteonecrosis is at the forefront of research and may soon lead to viable and less invasive non-surgical therapeutic strategies.

Skeletal manifestations of systemic autoimmune diseases.

PURPOSE OF REVIEW: There is an increased risk of osteoporotic fractures and osteonecrosis often at a young age among patients with certain systemic autoimmune diseases. The loss of bone mineral density and bone integrity seen with these diseases often cannot be explained by traditional risk factors alone. In this review, we focus on rheumatoid arthritis and systemic lupus erythematosus, two systemic autoimmune diseases in which skeletal manifestations have been well described. RECENT FINDINGS: There is recent evidence that autoimmunity and its associated inflammation and vitamin D deficiency play key roles in the pathogenesis of adverse skeletal effects. SUMMARY: Understanding these processes carries implications for the prevention and treatment of osteoporosis and osteonecrosis among patients with autoimmune diseases.

Effects of antiresorptive agents on osteomyelitis: novel insights into the pathogenesis of osteonecrosis of the jaw.

The effects of antiresorptive agents (e.g., alendronate [Aln], osteoprotegerin [OPG]) on bone infection are unknown. Thus, their effects on implant-associated osteomyelitis (OM) were investigated in mice using PBS (placebo), gentamycin, and etanercept (TNFR:Fc) controls. None of the drugs affected humoral immunity, angiogenesis, or chronic infection. However, the significant (P < 0.05 vs. PBS) inhibition of cortical osteolysis and decreased draining lymph node size in Aln- and OPG-treated mice was associated with a significant (P < 0.05) increase in the incidence of high-grade infections during the establishment of OM. In contrast, the high-grade infections in TNFR:Fc-treated mice were associated with immunosuppression, as evidenced by the absence of granulomas and presence of Gram(+) biofilm in the bone marrow. Collectively, these findings indicate that although antiresorptive agents do not exacerbate chronic OM, they can increase the bacterial load during early infection by decreasing lymphatic drainage and preventing the removal of necrotic bone that harbors the bacteria.