The role of myeloid derived suppressor cells in musculoskeletal disorders

Circulating receptor activator of nuclear factor kappa-B ligand (RANKL) levels predict response to immune checkpoint inhibitors in advanced non-small cell lung cancer (NSCLC)

BACKGROUND

Receptor activator of nuclear factor kappa-B ligand (RANKL) can directly promote tumor growth and indirectly support tumor immune evasion by altering the tumor microenvironment and immune cell responses. This study aimed to assess the prognostic significance of soluble RANKL in patients with advanced non-small cell lung cancer (NSCLC) receiving programmed cell death 1 (PD1)/programmed death-ligand 1 (PDL1) checkpoint inhibitor therapy.

METHODS

Plasma RANKL levels were measured in 100 patients with advanced NSCLC without bone metastases undergoing monotherapy with PD1/PDL1 checkpoint inhibitors. To establish the optimal cut-off value, we used the Cutoff Finder package in R. Survival curves for four distinct patient groups, according to their RANKL and PDL1 levels (high or low), were generated using the Kaplan-Meier method and compared with the log-rank test. The Cox regression model calculated HRs and 95% CIs for overall survival (OS) and progression-free survival (PFS).

RESULTS

The optimal RANKL cut-off was established at 280.4 pg/mL, categorizing patients into groups with high or low RANKL levels. A significant association was observed between increased RANKL concentrations and decreased survival rates at 24 months, only within the subgroup expressing high levels of PDL1 (p=0.002). Additionally, low RANKL levels in conjunction with elevated PDL1 expression correlated with improved PFS (median 22 months, 95% CI 6.70 to 50 vs median 4 months, 95% CI 3.0 to 7.30, p=0.009) and OS (median 26 months, 95% CI 20 to not reached vs median 7 months, 95% CI 6 to 13, p=0.003), indicating RANKL's potential as an indicator of adverse prognosis in these patients. Multivariate analysis identified RANKL as an independent negative prognostic factor for both PFS and OS, regardless of other clinicopathological features.

CONCLUSION

These results highlight the prognostic and predictive value of RANKL specifically in patients with high PDL1 expression.

Association between periodontitis and inflammatory comorbidities: The common role of innate immune cells, underlying mechanisms and therapeutic targets

Periodontitis, which is related to various systemic diseases, is a chronic inflammatory disease caused by periodontal dysbiosis of the microbiota. Multiple factors can influence the interaction of periodontitis and associated inflammatory disorders, among which host immunity is an important contributor to this interaction. Innate immunity can be activated aberrantly because of the systemic inflammation induced by periodontitis. This aberrant activation not only exacerbates periodontal tissue damage but also impairs systemic health, triggering or aggravating inflammatory comorbidities. Therefore, innate immunity is a potential therapeutic target for periodontitis and associated inflammatory comorbidities. This review delineates analogous aberrations of innate immune cells in periodontitis and comorbid conditions such as atherosclerosis, diabetes, obesity, and rheumatoid arthritis. The mechanisms behind these changes in innate immune cells are discussed, including trained immunity and clonal hematopoiesis of indeterminate potential (CHIP), which can mediate the abnormal activation and myeloid-biased differentiation of hematopoietic stem and progenitor cells. Besides, the expansion of myeloid-derived suppressor cells (MDSCs), which have immunosuppressive and osteolytic effects on peripheral tissues, also contributes to the interaction between periodontitis and its inflammatory comorbidities. The potential treatment targets for relieving the risk of both periodontitis and systemic conditions are also elucidated, such as the modulation of innate immunity cells and mediators, the regulation of trained immunity and CHIP, as well as the inhibition of MDSCs' expansion.

Exosomes as a potential therapeutic approach in osteoimmunology

Exosomes are natural extracellular vesicles that play a key role in inter- and intracellular communication. Currently they are considered as a promising therapeutic strategy for the treatment of various diseases. In osteoimmunology, exosomes can serve as biomarkers of bone homeostasis disorders and, at the same time, promising therapeutic agents with high stability in the biological environment, low immunogenicity and good bioavailability. In this review, we attempted to examine exosomes as natural mediators of intercellular communication, playing an essential role in the interaction of the immune system and bone tissue, based on an analysis of the PubMed database up to October 2023.

Periprosthetic Joint Infections of the Knee Lastingly Impact the Bone Homeostasis

After periprosthetic joint infection (PJI)-dependent revision surgery, a significantly elevated number of patients suffer from prosthesis failure due to aseptic loosening and require additional revision surgery despite clearance of the initial infection. The mechanisms underlying this pathology are not well understood, as it has been assumed that the bone stock recovers after revision surgery. Despite clinical evidence suggesting decreased osteogenic potential in PJI, understanding of the underlying biology remains limited. In this study, we investigated the impact of PJI on bone homeostasis in a two-stage exchange approach at explantation and reimplantation. Sixty-four human tibial and femoral specimens (20 control, 20 PJI septic explantation, and 24 PJI prosthesis reimplantation samples) were analyzed for their bone microstructure, cellular composition, and expression of relevant genetic markers. Samples were analyzed using X-ray microtomography, Alcian blue and tartrate-resistant acid phosphatase staining, and RT-qPCR. In patients with PJI, bone volume (BV/TV; 0.173 ± 0.026; p < 0.001), trabecular thickness (164.262 ± 18.841 μm; p < 0.001), and bone mineral density (0.824 ± 0.017 g/cm2 ; p = 0.049) were reduced; trabecular separation (1833.939 ± 178.501 μm; p = 0.005) was increased. While prevalence of osteoclasts was elevated (N.Oc/BS: 0.663 ± 0.102, p < 0.001), osteoblast cell numbers were lower at explantation (N.Ob/BS: 0.149 ± 0.021; p = 0.047). Mean expression of bone homeostasis markers osteocalcin, osteopontin, Runx2, TSG-6, and FGF-2 was significantly reduced at prosthesis explantation. Despite partial recovery, all analyzed parameters were still significantly impacted at reimplantation. In contrast, mean expression of osteoclastogenesis-stimulating cytokine IL-17a was significantly increased at both explantation and reimplantation. In this study, we found a strong and lasting impact of PJI on the bone homeostasis on a molecular, cellular, and microstructural level. These changes may be responsible for the increased risk of prosthesis failure due to aseptic loosening. Our data suggest there is significant potential in modulating bone homeostasis to improve prosthesis fixation and long-term clinical outcome in affected patients. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).