Nintedanib ameliorates osteoarthritis in mice by inhibiting synovial inflammation and fibrosis caused by M1 polarization of synovial macrophages via the MAPK/PI3K-AKT pathway

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

Conformationally regulated "nanozyme-like" cerium oxide with multiple free radical scavenging activities for osteoimmunology modulation and vascularized osseointegration

Given post-operative aseptic loosening in orthopedic disease treatment, osteointegration occurs at the bone-implant interface as a holistic process, including immunoregulation (e.g., macrophage polarization), angiogenesis and osteogenesis in sequence. In order to achieve early rapid and satisfactory osseointegration, different nano-shaped (nanocone, nanopolyhedron and nanoflower abbr. NC, NP & NF) cerium oxide (CeO2-x) coatings, endowed with "nanozyme-like" activities for multiple free radical elimination and osteoimmunology regulation, were hydrothermally synthesized on titanium alloy (TC4). In vitro cell experiments showed that nano-CeO2-x coated TC4 not only induced polarization of RAW264.7 cells toward M2 phenotype, but also promoted angiogenesis and vascularization of endothelial cells along with differentiation and mineralization of osteogenic precursor cells. Improvements in M2-polarized macrophage, angiogenesis, and bone regeneration were further confirmed in a rat femoral condyle model. Among the above three nano-morphologies, NF exhibited the best osseoinetegration. RNA sequencing and mechanism exploration suggested that the inhibition of PI3K-AKT signaling pathway was essential for immunomodulatory capacity of NF. In conclusion, it provided promising insights into the immunomodulatory exploitation of orthopedic implants.

Immunomodulatory effects of curcumin on macrophage polarization in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by synovial inflammation, cartilage destruction, pannus formation and bone erosion. Various immune cells, including macrophages, are involved in RA pathogenesis. The heterogeneity and plasticity of macrophages render them pivotal regulators of both the induction and resolution of the inflammatory response. Predominantly, two different phenotypes of macrophages have been identified: classically activated M1 macrophages exacerbate inflammation via the production of cytokines, chemokines and other inflammatory mediators, while alternatively activated M2 macrophages inhibit inflammation and facilitate tissue repair. An imbalance in the M1/M2 macrophage ratio is critical during the initiation and progression of RA. Macrophage polarization is modulated by various transcription factors, epigenetic elements and metabolic reprogramming. Curcumin, an active component of turmeric, exhibits potent immunomodulatory effects and is administered in the treatment of multiple autoimmune diseases, including RA. The regulation of macrophage polarization and subsequent cytokine production as well as macrophage migration is involved in the mechanisms underlying the therapeutic effect of curcumin on RA. In this review, we summarize the underlying mechanisms by which curcumin modulates macrophage function and polarization in the context of RA to provide evidence for the clinical application of curcumin in RA treatment.