Role of inflammation in the aging bones. Life Sci. 2015;123:25-34. [PMID: 25510309 DOI: 10.1016/j.lfs.2014.11.011]

BDNF alleviates senescence and enhances osteogenic differentiation in bone marrow mesenchymal stem cells via the TrkB/PI3K/AKT pathway

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) are stem cells that reside in bone marrow and have multidirectional differentiation potential. BMSCs have been used to treat bone injury. However, long-term passage leads to the aging of BMSCs and the weakening of osteogenic differentiation. Furthermore, brain-derived neurotrophic factor (BDNF) may enhance the antiaging ability of BMSCs. The purpose of this study was to investigate the role of BDNF in the senescence and osteogenic differentiation of human BMSCs (hBMSCs).

METHODS

The senescence of hBMSCs was induced by successive passages. The mRNA and protein expression levels were measured using RTqPCR and Western blotting. Alkaline phosphatase (ALP) and alizarin red S (ARS) staining were used to identify osteogenic differentiation in the cells.

RESULTS

After long-term passage, the hBMSCs morphologically gradually expanded and appeared flat, cell viability decreased, the number of fibroblast-like colony-forming units (CFU-Fs) decreased, and the number of β-galactosidase (SA-β-gal)-positive cells and the mRNA expression levels of the senescence-related genes p53, p21 and p16 increased. The activity of ALP, the level of calcium salt deposition and the protein levels of runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), osteopontin (OPN) and BDNF were significantly decreased. Subsequent research indicated that the senescence and inhibition of the osteogenic differentiation of hBMSCs induced by long-term culture were caused by low expression of BDNF. From a mechanistic standpoint, BDNF can activate the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway by upregulating the expression of tropomyosin receptor kinase B (TrkB), thereby improving the senescence and inhibition of the osteogenic differentiation of hBMSCs caused by long-term passage.

CONCLUSION

BDNF improves the senescence and inhibition of the osteogenic differentiation of hBMSCs caused by long-term passage via regulation of the TrkB/PI3K/AKT signaling axis.

Immunomodulation in Bone Tissue Engineering: Recent Advancements in Scaffold Design and Biological Modifications for Enhanced Regeneration

Bone defects, whether caused by trauma, cancer, infectious diseases, or surgery, can significantly impair people's quality of life. Although autografts are the gold standard for treating bone defects, they often fall short in adequately forming bone tissue. The field of bone tissue engineering has made strides in using scaffolds with various biomaterials, stem cells, and growth factors to enhance bone healing. However, some biological structures do not yield satisfactory therapeutic outcomes for new bone formation. Recent studies have shed light on the crucial role of immunomodulation, specifically the interaction between the implanted scaffold and host immune systems, in bone regeneration. Immune cells, particularly macrophages, are pivotal in the inflammatory response, angiogenesis, and osteogenesis. This review delves into the immune system's mechanism toward foreign bodies and the recent advancements in scaffolds' physical and biological properties that foster bone regeneration by modulating macrophage polarization to an anti-inflammatory phenotype and enhancing the osteoimmune microenvironment.

Aging alters the effect of adiponectin receptor signaling on bone marrow-derived mesenchymal stem cells

Adiponectin receptor signaling represents a promising therapeutic target for age-related conditions such as osteoporosis and diabetes. However, the literature presents conflicting evidence regarding the role of adiponectin signaling in bone homeostasis and fracture repair across different health states, ages, and disease conditions. These inconsistencies may arise from the complex endocrine and paracrine feedback mechanisms regulating adiponectin, as well as the variability in adiponectin isoforms and receptor expressions. In this study, we observed differential expression of adiponectin receptors in the bone marrow (BM) of aged mice, characterized by elevated levels of adiponectin receptor 2 and reduced levels of receptor 1, as corroborated by both single-cell sequencing and in vivo staining. Additionally, circulating levels of adiponectin and its local expression were significantly higher in aged mice compared to younger counterparts. Treatment with adiponectin receptor agonist, AdipoRon, enhanced bone regeneration and repair in young mice by promoting osteogenesis and reducing osteoclastogenesis. Conversely, in aged mice, AdipoRon treatment led to cellular senescence, delayed bone repair, and inhibited osteogenic activity. Notably, the adiponectin receptor 1-Wnt and adiponectin receptor 2-MAPK and mTOR signaling pathways were differentially activated in AdipoRon-treated BM mesenchymal stem cells from young and aged mice. Additionally, the NF-κB, and AKT pathways were consistently downregulated in BM macrophages of both age groups following AdipoRon administration. In conclusion, aging significantly modulates the impact of adiponectin receptor signaling on BM mesenchymal stem cells. This modulation is potentially attributable to changes in receptor transcription and distribution, as well as differential activation of downstream signaling pathways.

Comprehensive analysis of ferroptosis-related genes reveals potential therapeutic targets in osteoporosis patients: a computational analysis and in vitro experiments

Background

Ferroptosis-related genes have been reported to play important roles in many diseases, but their molecular mechanisms in osteoporosis have not been elucidated.

Methods

Based on two independent GEO datasets (GSE35956 and GSE35958), and GSE35959 as the validation dataset, we comprehensively elucidated the pathological mechanism of ferroptosis-related genes in osteoporosis by GO analyses, KEGG analyses and a PPI network. Then, We used Western Blot (WB) and Quantitative real-time polymerase chain reaction (qPCR) to verify the expression level of KMT2D, a ferroptosis-related hub gene, in clinical samples. Subsequently, we predicted the upstream miRNA of KMT2D gene and analyzed the mechanism of KMT2D in osteoporosis, the potential prognostic value and its immune invasion of KMT2D in pan-cancer.

Results

This study identified KMT2D and MYCN, TP63, RELA, SOX2, and CDKN1A as key ferroptosis-related genes in osteoporotic cell aging. The independent dataset validated that the expression level of KMT2D was significantly upregulated in osteoporosis samples. The experimental verification results of qPCR and WB indicate that KMT2D is highly expressed in patients with osteoporosis. Further analysis revealed that the hsa-miR-204-5p-KMT2D axis may play an important role in the aging of osteoporotic cells. The analysis of KMT2D reveals that KMT2D may mainly play a role in the aging of osteoporotic cells through epigenetics and the value in pan-cancer.

Conclusion

The study provides a theoretical basis for the treatment of osteoporosis.

MBG/BSA Bone Grafts Immunomodulate Bone Regeneration by Releasing Bioactive Ions in Inflammatory Bone Defects

Since the diseases that cause bone defects are mostly inflammatory diseases, the current bone grafts are unable to effectively regulate osteoimmune activity, leading to the impaired osteogenesis and unfavorable bone regeneration. In this study, inspired by bone composition, biomimetic mesoporous bioactive glass nanoparticle (MBG)/bovine serum albumin (BSA) bone grafts are designed for inflammatory bone defects. Systematically, MBG/BSA bone grafts are evaluated for characterization, bioactivity, anti-inflammatory, antioxidant activity, and osteogenic activity. MBG/BSA bone grafts are proved to be biocompatible and can release bioactive ions including calcium and silicon in a sustained manner. Furthermore, MBG/BSA reprograms the macrophage phenotype toward anti-inflammation that is beneficial for bone regeneration. The antioxidative activity is also validated under inflammation and the mechanism may be via the interleukin-4 (IL-4)/Signal transducer and activator of transcription 6 (STAT6) pathway. The osteogenic differentiation and mineralization are also facilitated due to the improved immunoregulation of MBG/BSA. Overall, this work suggests that the MBG/BSA bone grafts with improved immunomodulatory properties are an ideal material for inflammatory bone regeneration application.

Pharmacological inactivation of a non-canonical gp130 signaling arm attenuates chronic systemic inflammation and multimorbidity induced by a high-fat diet

Interleukin-6 (IL-6) is a major pro-inflammatory cytokine that demonstrates a robust correlation with age and body mass index (BMI) as part of the senescence-associated secretory phenotype. IL-6 cytokines also play a crucial role in metabolic homeostasis and regenerative processes primarily via the canonical STAT3 pathway. Thus, selective modulation of IL-6 signaling may offer a unique opportunity for therapeutic interventions. Our recent studies identified a novel non-canonical signaling pathway that involves prolonged activation of SRC family of kinases (SFKs) by IL-6/gp130, where genetic or pharmacological inhibition of this pathway was protective in several acute injury models. This study was designed to assess the effect of a small molecule (R159) that inhibits the non-canonical signaling in a mouse model of multimorbidity induced by chronic inflammation. Aged mice were fed a high-fat diet (HFD) to exacerbate chronic inflammation and inflammaging-related conditions, and R159 significantly decreased systemic inflammatory responses in adipose tissue and liver. R159 was protective against trabecular bone and articular cartilage loss and markedly prevented neurogenesis decline. Moreover, R159 reduced weight gain induced by HFD and increased physical activity levels. These findings suggest that selective pharmacological inhibition of SFK signaling downstream of IL6/gp130 offers a promising strategy to alleviate systemic chronic inflammation and relevant multimorbidity.

Dietary inflammatory index is not associated with bone mineral density in functionally able community-dwelling older adults

BACKGROUND

Osteoporosis poses a significant health and quality-of-life burden on older adults, particularly with associated fractures after a fall. A notable increase in pro-inflammatory cytokines associated with aging contributes to a decline in bone mineral density (BMD). Certain food components have been shown to influence an individual's inflammatory state and may contribute to optimal bone health as a modifiable risk factor, particularly later in life. This study aims to explore the relationship between the dietary inflammatory index (DII) and dietary intake with BMD in community-dwelling older adults.

METHODS

Heathy community-dwelling older adults aged 65-85 years. DII scores were calculated using 24-h dietary recalls, and lumbar spine (L1-L4) and femoral neck (ward's triangle) BMD was assessed via dual-energy x-ray absorptiometry.

RESULTS

A total of 94 participants were recruited (72.9 ± 4.9 years, 76.6% female) with 61.7% identified having an anti-inflammatory diet (average DII = - 0.50 ± 1.6), 88.3% were physically active, 47.8% were osteopenic and 27.7% osteoporotic. There was no significant difference between DII scores, nutrient or food group intake in groups stratified by BMD T-Score except for lean meats and alternatives food group (p = 0.027). Multiple regression analysis found no associations between DII and lumbar spine (unadjusted model β = 0.020, p = 0.155) or femoral neck BMD (unadjusted model β = - 0.001, p = 0.866).

CONCLUSION

Most of this cohort of functionally able community-dwelling older adults followed an anti-inflammatory diet. DII and dietary intake were not associated with BMD. This research underlines the complex interplay between modifiable and non-modifiable risk factors on the BMD of older, physically active adults.

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

A novel multifunctional nanocomposite hydrogel orchestrates the macrophage reprogramming-osteogenesis crosstalk to boost bone defect repair

Repairing bone defects is a complex cascade reaction process, as immune system regulation, vascular growth, and osteogenic differentiation are essential. Thus, developing a tissue-engineered biomaterial that caters to the complex healing process of bone regeneration remains a major clinical challenge. In the study, Ca2+-TA-rGO (CTAG)/GelMA hydrogels were synthesized by binding Ca2+ using metal chelation to graphene oxide (GO) nanosheets reduced by tannic acid (TA-rGO) and doping them into gelatin methacrylate (GelMA) hydrogels. TA and rGO exhibited biocompatibility and immunomodulatory properties in this composite, while Ca2+ promoted bone formation and angiogenesis. This novel nanocomposite hydrogel demonstrated good mechanical properties, degradability, and conductivity, and it could achieve slow Ca2+ release during bone regeneration. Both in vitro and in vivo experiments revealed that CTAG/GelMA hydrogel modulated macrophage reprogramming and induced a shift from macrophages to healing-promoting M2 macrophages during the inflammatory phase, promoted vascular neovascularization, and facilitated osteoblast differentiation during bone formation. Moreover, CTAG/GelMA hydrogel could downregulate the NF-κB signaling pathway, offering new insights into regulating macrophage reprogramming-osteogenic crosstalk. Conclusively, this novel multifunctional nanocomposite hydrogel provides a multistage treatment for bone and orchestrates macrophage reprogramming-osteogenic crosstalk to boost bone repair.

"A Friend Among Strangers" or the Ambiguous Roles of Runx2

The transcription factor Runx2 plays a crucial role in regulating osteogenic differentiation and skeletal development. This factor not only controls the expression of genes involved in bone formation, but also interacts with signaling pathways such as the Notch pathway, which are essential for body development. However, studies have produced conflicting results regarding the relationship between Runx2 and the Notch pathway. Some studies suggest a synergistic interaction between these molecules, while others suggest an inhibitory one, for example, the interplay between Notch signaling, Runx2, and vitamin D3 in osteogenic differentiation and bone remodeling. The findings suggest a complex relationship between Notch signaling and osteogenic differentiation, with ongoing research needed to clarify the mechanisms involved and resolve existing contradictions regarding role of Notch in this process. Additionally, there is increasing evidence of contradictory roles for Runx2 in various tissues and organs, both under normal conditions and in pathological states. This diversity of roles makes Runx2 a potential therapeutic target, offering new directions for research. In this review, we have discussed the mechanisms of osteogenic differentiation and the important role of Runx2 in this process. We have also examined its relationship with different signaling pathways. However, there are still many uncertainties and inconsistencies in our current understanding of these interactions. Additionally, given that Runx2 is also involved in numerous other events in various tissues, we have tried to comprehensively examine its functions outside the skeletal system.

Chitosan-based biomaterials promote bone regeneration by regulating macrophage fate

The development of various osteogenic biomaterials has not only promoted the development of bone tissue engineering but also provided more possibilities for bone defect repair. However, most previous studies have focused on the interaction of biomaterials on endogenous or exogenous stem cells involved in the bone regeneration process while neglecting the effect of changes in the immune microenvironment of bone defect sites on bone regeneration after biomaterial implantation into the host. With the development of bone immunology, the role of various immune cells, especially macrophages, in bone regeneration has gradually attracted the attention of researchers. An increasing number of studies have begun to target macrophages to better promote bone regeneration by modulating the fate of macrophages in a spatiotemporally ordered manner to mimic the changes in the immune microenvironment of bone defect sites during the natural repair process of bone tissue. Chitosan is one of the most abundant natural polysaccharides in the world. In recent years, various chitosan-based biomaterials have been widely used in macrophage fate modulation and bone regeneration. In this review, we review the interaction between macrophages and scaffold materials, general information about chitosan, the modulation of macrophage fate by chitosan-based biomaterials, and their application in bone regeneration.

Biodegradable Zn-2Cu-0.5Zr alloy promotes the bone repair of senile osteoporotic fractures via the immune-modulation of macrophages

Delayed bone-healing of senile osteoporotic fractures remains a clinical challenge due to the alterations caused by aging in bone and immune systems. The novel biomaterials that address the deficiencies in both skeletal cells and immune systems are required to effectively treat the bone injuries of older patients. Zinc (Zn) has shown promise as a biodegradable material for use in orthopedic implants. To address the bone-healing deficiencies in elderly patients with bone injuries, we developed a biodegradable Zn-based alloy (Zn-2Cu-0.5Zr) with enhanced mechanical properties, including a yield strength of 198.7 MPa and ultimate tensile strength of 217.6 MPa, surpassing those of pure Zn and Zn-2Cu alloys. Cytotoxicity tests conducted on bone marrow mesenchymal stem cells (BMSCs) and MC3T3-E1 cells demonstrated that the extracts from Zn-2Cu-0.5Zr alloy exhibited no observable cytotoxic effects. Furthermore, the extracts of Zn-2Cu-0.5Zr alloy exhibited significant anti-inflammatory effects through regulation of inflammation-related cytokine production and modulation of macrophage polarization. The improved immune-osteo microenvironment subsequently contributed to osteogenic differentiation of BMSCs. The potential therapeutic application of Zn-2Cu-0.5Zr in senile osteoporotic fracture was tested using a rat model of age-related osteoporosis. The Zn-2Cu-0.5Zr alloy met the requirements for load-bearing applications and accelerated the healing process in a tibial fracture in aged rats. The imaging and histological analyses showed that it could accelerate the bone-repair process and promote the fracture healing in senile osteoporotic rats. These findings suggest that the novel Zn-2Cu-0.5Zr alloy holds potential for influencing the immunomodulatory function of macrophages and facilitating bone repair in elderly individuals with osteoporosis.

Distinct mechanisms of iron and zinc metal ions on osteo-immunomodulation of silicocarnotite bioceramics

The immunomodulatory of implants have drawn more and more attention these years. However, the immunomodulatory of different elements on the same biomaterials have been rarely investigated. In this work, two widely used biosafety elements, iron and zinc added silicocarnotite (Ca5(PO4)2SiO4, CPS) were applied to explore the routine of elements on immune response. The immune reactions over time of Fe-CPS and Zn-CPS were explored at genetic level and protein level, and the effects of their immune microenvironment with different time points on osteogenesis were also investigated in depth. The results confirmed that both Fe-CPS and Zn-CPS had favorable ability to secret anti-inflammatory cytokines. The immune microenvironment of Fe-CPS and Zn-CPS also could accelerate osteogenesis and osteogenic differentiation in vitro and in vivo. In terms of mechanism, RNA-seq analysis and Western-blot experiment revealed that PI3K-Akt signaling pathway and JAK-STAT signaling pathways were activated of Fe-CPS to promote macrophage polarization from M1 to M2, and its immune microenvironment induced osteogenic differentiation through the activation of Hippo signaling pathway. In comparison, Zn-CPS inhibited polarization of M1 macrophage via the up-regulation of Rap1 signaling pathway and complement and coagulation cascade pathway, while its osteogenic differentiation related pathway of immune environment was NF-κB signaling pathway.

The roles of stress-induced premature senescence and Akt/FoxO1 signaling in periapical lesions

OBJECTIVES

There is little knowledge about oxidative stress-induced senescence involvement in apical periodontitis. Here, we explored its molecular mechanism in periapical lesions.

METHODS

Ten cases of radicular cysts and five cases of periapical granulomas were randomly selected. Immunohistochemical analysis was performed to detect the expression and correlation between Senescence-associated factor polymerase I and transcript release factor (PTRF) and Akt/FoxO1 signaling. Human periodontal ligament cells (hPDLCs) pretreated with LY294002 were exposed to H2O2-induced oxidative stress conditions and then cell proliferation, senescence, apoptosis, and associated signaling were evaluated by EdU labeling, β-galactosidase assay, RT-qPCR, and western blot analysis, respectively.

RESULTS

Polymerase I and transcript release factor and Akt/FoxO1 signaling were more frequently expressed in the radicular cyst than in periapical granulomas. Notably, cells in radicular cysts showed Akt activation, FoxO1 phosphorylation, and cytoplasmic translocation. In vitro, prominent H2O2-induced senescence was observed in hPDLCs. LY294002, a PI3K inhibitor, attenuated the expression levels of senescence (Klotho, P16INK4), apoptosis (Bad, Fas), phosphorylated Akt, and phosphorylated FoxO1; however, did not affect cell proliferation.

CONCLUSIONS

Our data indicated that senescence is present in clinical periapical lesions, and Akt/FoxO1 signaling is involved in the H2O2-induced cellular senescence, which could serve as a potential therapeutic target.

Inactivation of a non-canonical gp130 signaling arm attenuates chronic systemic inflammation and multimorbidity induced by a high-fat diet

Interleukin-6 (IL-6) is a major pro-inflammatory cytokine for which the levels in plasma demonstrate a robust correlation with age and body mass index (BMI) as part of the senescence-associated secretory phenotype. IL-6 cytokines also play a crucial role in metabolic homeostasis and regenerative processes, primarily via the canonical STAT3 pathway. Thus, selective modulation of IL-6 signaling may offer a unique opportunity for therapeutic interventions. Recently, we discovered that a non-canonical signaling pathway downstream of tyrosine (Y) 814 within the intracellular domain of gp130, the IL-6 co-receptor, is responsible for the recruitment and activation of SRC family of kinases (SFK). Mice with constitutive genetic inactivation of gp130 Y814 (F814 mice) show accelerated resolution of inflammatory response and superior regenerative outcomes in skin wound healing and posttraumatic models of osteoarthritis. The current study was designed to explore if selective genetic or pharmacological inhibition of the non-canonical gp130-Y814/SFK signaling reduces systemic chronic inflammation and multimorbidity in a high-fat diet (HFD)-induced model of accelerated aging. F814 mice showed significantly reduced inflammatory response to HFD in adipose and liver tissue, with significantly reduced levels of systemic inflammation compared to wild type mice. F814 mice were also protected from HFD-induced bone loss and cartilage degeneration. Pharmacological inhibition of gp130-Y814/SFK in mice on HFD mirrored the effects observed in F814 mice on HFD; furthermore, this pharmacological treatment also demonstrated a marked increase in physical activity levels and protective effects against inflammation-associated suppression of neurogenesis in the brain tissue compared to the control group. These findings suggest that selective inhibition of SFK signaling downstream of gp130 receptor represents a promising strategy to alleviate systemic chronic inflammation. Increased degenerative changes and tissue senescence are inevitable in obese and aged organisms, but we demonstrated that the systemic response and inflammation-associated multi-morbidity can be therapeutically mitigated.

Mesoporous bioactive glass scaffolds for the delivery of bone marrow stem cell-derived osteoinductive extracellular vesicles lncRNA promote senescent bone defect repair by targeting the miR-1843a-5p/Mob3a/YAP axis

Bone repair in elderly patients poses a huge challenge due to the age-related progressive decline in regenerative abilities attributed to the senescence of bone marrow stem cells (BMSCs). Bioactive scaffolds have been applied in bone regeneration due to their various biological functions. In this study, we aimed to fabricate functionalized bioactive scaffolds through loading osteoinductive extracellular vesicles (OI-EVs) based on mesoporous bioactive glass (MBG) scaffolds (1010 particles/scaffold) and to investigate its effects on osteogenesis and senescence of BMSCs. The results suggested that OI-EVs upregulate the proliferative and osteogenic capacities of senescent BMSCs. More importantly, The results showed that loading OI-EVs into MBG scaffolds achieved better bone regeneration. Furthermore, OI-EVs and BMSCs RNAs bioinformatics analysis indicated that OI-EVs play roles through transporting pivotal lncRNA acting as a "sponge" to compete with Mob3a for miR-1843a-5p to promote YAP dephosphorylation and nuclear translocation, ultimately resulting in elevated proliferation and osteogenic differentiation and reduced senescence-related phenotypes. Collectively, these results suggested that the OI-EVs lncRNA ceRNA regulatory networks might be the key point for senescent osteogenesis. More importantly, the study indicated the feasibility of loading OI-EVs into scaffolds and provided novel insights into biomaterial design for facilitating bone regeneration in the treatment of senescent bone defects. STATEMENT OF SIGNIFICANCE: Constructing OI-EVs/MBG delivering system and verification of its bone regeneration enhancement in senescent defect repair. Aging bone repair poses a huge challenge due to the age-related progressive degenerative decline in regenerative abilities attributed to the senescence of BMSCs. OI-EVs/MBG delivering system were expected as promising treatment for senescent bone repair, which could provide an effective strategy for bone regeneration in elderly patients. Clarification of potential OI-EVs lncRNA ceRNA regulatory mechanism in senescent bone regeneration OI-EVs play important roles through transferring lncRNA-ENSRNOG00000056625 sponging miR-1843a-5p that targeted Mob3a to activate YAP translocation into nucleus, ultimately alleviate senescence, promote proliferation and osteogenic differentiation in O-BMSCs, which provides theoretical basis for EVs-mediated therapy in future clinical works.

Naringin-induced M2 macrophage polarization facilitates osteogenesis of BMSCs and improves cranial bone defect healing in rat

Osteoimmunology has uncovered the critical role of the immune microenvironment in the bone healing process, with macrophages playing a central part in generating immune responses via chemokine production. Naringin, a flavanone glycoside extracted from various plants, has been shown to promote osteoblast differentiation, thereby enhancing bone formation and mitigating osteoporosis progression. Current research on the osteogenic mechanism primarily focuses on the direct impact of naringin on mesenchymal stem cells, while its indirect immunoregulatory effects remain elusive. In this study, we investigated the bone defect-enhancing effects of varying naringin concentrations in vivo using a cranial bone defect model in Sprague-Dawley rats. We assessed the osteoimmune modulation capacity of naringin by exposing lipopolysaccharide (LPS)-induced RAW 264.7 macrophages to different doses of naringin. To further elucidate the underlying osteogenic enhancement mechanism, Bone Marrow Stromal Cells (BMSCs) derived from mice were treated with conditioned media from naringin-treated macrophages. Our findings indicated that naringin promotes M2 phenotype polarization in macrophages, as evidenced by the downregulation of pro-inflammatory cytokines Inducible Nitric Oxide Synthase (iNOS), interleukin (IL)-1β, and Tumor Necrosis Factor (TNF)-α, and the upregulation of anti-inflammatory cytokine Transforming growth factor (TGF)-β. Transcriptome analysis revealed that differentially expressed genes were significantly enriched in osteoblast differentiation and anti-inflammatory response pathways in naringin-pretreated macrophages, with the cytokines signaling pathway being upregulated. The conditioned media from naringin-treated macrophages stimulated the expression of osteogenic-related genes Alkaline phosphatase (Alp), osteocalcin (Ocn), osteopontin (Opn), and Runt-related transcription factor (Runx) 2, as well as protein expression in BMSCs. In conclusion, naringin alleviates macrophage inflammation by promoting M2 phenotype polarization, which in turn enhances the osteogenic differentiation of BMSCs, contributing to its bone healing effects in vivo. These results suggest that naringin holds significant potential for improving bone defect healing through osteoimmune modulation.

Phytic acid improves osteogenesis and inhibits the senescence of human bone marrow mesenchymal stem cells under high-glucose conditions via the ERK pathway

Hyperglycaemia causes impairment of osteogenic differentiation and accelerates stem cell senescence, resulting in weakened osteogenesis and disordered bone metabolism. Phytic acid (PA) is an antioxidant that is reportedly beneficial to bone homeostasis. The present study aims to clarify how PA affects the osteogenic capacity and cellular senescence of bone marrow mesenchymal stem cells (BMSCs) exposed to high-glucose environments, as well as the potential molecular mechanisms. Our results indicate that osteogenic differentiation in BMSCs cultivated in high-glucose conditions is enhanced by PA, as evidenced by increased alkaline phosphatase activity and staining, Alizarin Red S staining, osteogenic marker in in vitro studies, and increased osteogenesis in animal experiments. PA also prevented high-glucose-induced senescence of BMSCs, as evidenced by the repression of reactive oxygen species production, senescence-associated β-galactosidase staining, and P21 and P53 expression. Furthermore, it was found that PA rescued the high-glucose-inhibited expression of phosphorylated extracellular regulated protein kinases (p-ERK). The inhibition of ERK pathway by the specific inhibitor PD98059 blocked the PA-enhanced osteogenesis of BMSCs and promoted cell senescence. Our results revealed that PA enhances osteogenic differentiation and inhibits BMSC senescence in a high-glucose environment. In addition, the activation of the ERK pathway seems to mediate the beneficial effects of PA. The findings provide novel insights that could facilitate bone regeneration in patients with diabetes.

Effects of emulsified and non-emulsified palm tocotrienol on bone and joint health in ovariectomised rats with monosodium iodoacetate-induced osteoarthritis

Postmenopausal women are susceptible to osteoporosis and osteoarthritis. Tocotrienol, a bone-protective nutraceutical, is reported to prevent osteoarthritis in male rats. However, its efficacy on joint health in oestrogen deficiency has not been validated. Besides, data on the use of emulsification systems in enhancing bioavailability and protective effects of tocotrienol are limited. Ovariectomised adult female Sprague-Dawley rats (3 months old) were treated with refined olive oil, emulsified (EPT, 100 mg/kg/day with 25% vitamin E content), non-emulsified palm tocotrienol (NEPT, 100 mg/kg/day with 50% vitamin E content) and calcium carbonate (1% w/v in drinking water) plus glucosamine sulphate (250 mg/kg/day) for 10 weeks. Osteoarthritis was induced with monosodium iodoacetate four weeks after ovariectomy. Baseline control was sacrificed upon receipt, while the sham group was not ovariectomised and treated with refined olive oil. EPT and NEPT prevented femoral metaphyseal and subchondral bone volume decline caused by ovariectomy. EPT decreased subchondral trabecular separation compared to the negative control. EPT preserved stiffness and Young's Modulus at the femoral mid-shaft of the rats. Circulating RANKL was reduced post-treatment in the EPT group. Joint width was reduced in all the treatment groups vs the negative control. The EPT group's grip strength was significantly improved over the negative control and NEPT group. EPT also preserved cartilage histology based on several Mankin's subscores. EPT performed as effectively as NEPT in preventing osteoporosis and osteoarthritis in ovariectomised rats despite containing less vitamin E content. This study justifies clinical trials for the use of EPT in postmenopausal women with both conditions.

Complex Spatio-Temporal Interplay of Distinct Immune and Bone Cell Subsets during Bone Fracture Healing

BACKGROUND

The healing of a bone injury is a highly complex process involving a multitude of different tissue and cell types, including immune cells, which play a major role in the initiation and progression of bone regeneration.

METHODS

We histologically analyzed the spatio-temporal occurrence of cells of the innate immune system (macrophages), the adaptive immune system (B and T lymphocytes), and bone cells (osteoblasts and osteoclasts) in the fracture area of a femoral osteotomy over the healing time. This study was performed in a bone osteotomy gap mouse model. We also investigated two key challenges of successful bone regeneration: hypoxia and revascularization.

RESULTS

Macrophages were present in and around the fracture gap throughout the entire healing period. The switch from initially pro-inflammatory M1 macrophages to the anti-inflammatory M2 phenotype coincided with the revascularization as well as the appearance of osteoblasts in the fracture area. This indicates that M2 macrophages are necessary for the restoration of vessels and that they also play an orchestrating role in osteoblastogenesis during bone healing. The presence of adaptive immune cells throughout the healing process emphasizes their essential role for regenerative processes that exceeds a mere pathogen defense. B and T cells co-localize consistently with bone cells throughout the healing process, consolidating their crucial role in guiding bone formation. These histological data provide, for the first time, comprehensive information about the complex interrelationships of the cellular network during the entire bone healing process in one standardized set up. With this, an overall picture of the spatio-temporal interplay of cellular key players in a bone healing scenario has been created.

CONCLUSIONS

A spatio-temporal distribution of immune cells, bone cells, and factors driving bone healing at time points that are decisive for this process-especially during the initial steps of inflammation and revascularization, as well as the soft and hard callus phases-has been visualized. The results show that the bone healing cascade does not consist of five distinct, consecutive phases but is a rather complex interrelated and continuous process of events, especially at the onset of healing.

A novel porous hydroxyapatite scaffold (pHAMG) enhances angiogenesis and osteogenesis around dental implants by regulating the immune microenvironment

OBJECTIVE

The purpose was to evaluate whether a novel porous hydroxyapatite (HA) scaffold with a 25-30-µm groove structure (pHAMG) may improve bone osteogenesis, angiogenesis, and bone integration of titanium dental implants in animal models.

METHODS

The pHAMG was prepared by chemical precipitation method and its elemental composition and crystal structure were evaluated. The ability of the scaffolds to induce ectopic osteogenesis and the ability of scaffolds combined with titanium dental implants to induce orthotopic peri-implant angiogenesis, osteogenesis, and osteointegration were tested after implantation into the femur muscle pocket in rats and the mandibular defects in beagle dogs, respectively. The elemental composition was evaluated by SEM-EDS; the expression of the relevant osteogenic/inflammation marker and the anti-/pro-inflammation markers was evaluated by immunostaining and immunofluorescence, respectively.

RESULTS

In animal experiments with ectopic and peri-implant osteogenesis, pHAMG resulted in significantly larger neovascularization by hematoxylin-eosin staining, as well as deposition of collagen fibers by Masson staining than HA. Meanwhile, microgrooves in pHAMG upregulate more bone morphogenetic protein (BMP) 2 and interleukin-4 (IL-4) and -10 (IL-10) and downregulate more IL-1β and tumor necrosis factor-α (TNF-α) than that in HA. The pHAMG showed greater expression of arginase (Arg)-1 and lower expression of inducible nitric oxide synthase (iNOS) than HA.

CONCLUSION

The novel pHAMG can better repair bone defects in ectopic and orthotopic model. It also transfers macrophages to anti-inflammatory phenotypes, promoting angiogenic and osteogenesis in scaffolds, and bone integration in implants.

CLINICAL RELEVANCE

The novel pHAMG induce greater osteogenesis and angiogenesis which could be utilized in the clinical treatment.

Reduced angiogenesis and delayed endochondral ossification in CD163-/- mice highlights a role of M2 macrophages during bone fracture repair

While recent studies showed that macrophages are critical for bone fracture healing, and lack of M2 macrophages have been implicated in models of delayed union, functional roles for specific M2 receptors have yet to be defined. Moreover, the M2 scavenger receptor CD163 has been identified as a target to inhibit sepsis following implant-associated osteomyelitis, but potential adverse effects on bone healing during blockage therapy have yet to be explored. Thus, we investigated fracture healing in C57BL/6 versus CD163-/- mice using a well-established closed, stabilized, mid-diaphyseal femur fracture model. While gross fracture healing in CD163-/- mice was similar to that of C57BL/6, plain radiographs revealed persistent fracture gaps in the mutant mice on Day 14, which resolved by Day 21. Consistently, 3D vascular micro-CT demonstrated delayed union on Day 21, with reduced bone volume (74%, 61%, and 49%) and vasculature (40%, 40%, and 18%) compared to C57BL/6 on Days 10, 14, and 21 postfracture, respectively (p < 0.01). Histology confirmed large amounts of persistent cartilage in CD163-/- versus C57BL/6 fracture callus on Days 7 and 10 that resolves over time, and immunohistochemistry demonstrated deficiencies in CD206+ M2 macrophages. Torsion testing of the fractures confirmed the delayed early union in CD163-/- femurs, which display decreased yield torque on Day 21, and a decreased rigidity with a commensurate increase in rotation at yield on Day 28 (p < 0.01). Collectively, these results demonstrate that CD163 is required for normal angiogenesis, callus formation, and bone remodeling during fracture healing, and raise potential concerns about CD163 blockade therapy.

The synergistic effects of polyphenols and intestinal microbiota on osteoporosis

Osteoporosis is a common metabolic disease in middle-aged and elderly people. It is characterized by a reduction in bone mass, compromised bone microstructure, heightened bone fragility, and an increased susceptibility to fractures. The dynamic imbalance between osteoblast and osteoclast populations is a decisive factor in the occurrence of osteoporosis. With the increase in the elderly population in society, the incidence of osteoporosis, disability, and mortality have gradually increased. Polyphenols are a fascinating class of compounds that are found in both food and medicine and exhibit a variety of biological activities with significant health benefits. As a component of food, polyphenols not only provide color, flavor, and aroma but also act as potent antioxidants, protecting our cells from oxidative stress and reducing the risk of chronic disease. Moreover, these natural compounds exhibit anti-inflammatory properties, which aid in immune response regulation and potentially alleviate symptoms of diverse ailments. The gut microbiota can degrade polyphenols into more absorbable metabolites, thereby increasing their bioavailability. Polyphenols can also shape the gut microbiota and increase its abundance. Therefore, studying the synergistic effect between gut microbiota and polyphenols may help in the treatment and prevention of osteoporosis. By delving into how gut microbiota can enhance the bioavailability of polyphenols and how polyphenols can shape the gut microbiota and increase its abundance, this review offers valuable information and references for the treatment and prevention of osteoporosis.

An Integrated Approach to Skeletal Muscle Health in Aging

A decline in muscle mass and function represents one of the most problematic changes associated with aging, and has dramatic effects on autonomy and quality of life. Several factors contribute to the inexorable process of sarcopenia, such as mitochondrial and autophagy dysfunction, and the lack of regeneration capacity of satellite cells. The physiologic decline in muscle mass and in motoneuron functionality associated with aging is exacerbated by the sedentary lifestyle that accompanies elderly people. Regular physical activity is beneficial to most people, but the elderly need well-designed and carefully administered training programs that improve muscle mass and, consequently, both functional ability and quality of life. Aging also causes alteration in the gut microbiota composition associated with sarcopenia, and some advances in research have elucidated that interventions via the gut microbiota-muscle axis have the potential to ameliorate the sarcopenic phenotype. Several mechanisms are involved in vitamin D muscle atrophy protection, as demonstrated by the decreased muscular function related to vitamin D deficiency. Malnutrition, chronic inflammation, vitamin deficiencies, and an imbalance in the muscle-gut axis are just a few of the factors that can lead to sarcopenia. Supplementing the diet with antioxidants, polyunsaturated fatty acids, vitamins, probiotics, prebiotics, proteins, kefir, and short-chain fatty acids could be potential nutritional therapies against sarcopenia. Finally, a personalized integrated strategy to counteract sarcopenia and maintain the health of skeletal muscles is suggested in this review.

Plasma inflammation-related biomarkers are associated with intrinsic capacity in community-dwelling older adults

BACKGROUND

How inflammation relates to intrinsic capacity (IC), the composite of physical and mental capacities, remains undefined. Our study aimed to investigate the cross-sectional and longitudinal associations between plasma inflammation-related biomarkers and IC in older adults.

METHODS

This secondary analysis of the Multidomain Alzheimer Preventive Trial (MAPT) included 1238 community-dwelling older individuals with IC assessments from 12 to 60 months. Plasma C-reactive protein (CRP), interleukin-6 (IL-6), tumour necrosis factor receptor-1 (TNFR-1), monocyte chemoattractant protein-1 (MCP-1) and growth differentiation factor-15 (GDF-15) were measured at 12 months. IC was operationalized as a score ranging from 0 to 100, derived from four domains: cognition, Mini-Mental State Examination; locomotion, Short Physical Performance Battery; psychological, Geriatric Depression Scale; and vitality, handgrip strength. A five-domain IC score (plus sensory) was investigated in a subsample (n = 535) with a 1-year follow-up as an exploratory outcome.

RESULTS

The mean age of the 1238 participants was 76.2 years (SD = 4.3); 63.7% were female. Their initial four-domain IC scores averaged 78.9 points (SD = 9.3), with a yearly decline of 1.17 points (95% CI = -1.30 to -1.05; P < 0.001). We observed significant associations of lower baseline IC with higher CRP, IL-6, TNFR-1 and GDF-15, after controlling age, sex, MAPT group allocation and educational level [CRP: adjusted β (95% CI) = -1.56 (-2.64 to -0.48); P = 0.005; IL-6: adjusted β = -3.16 (-4.82 to -1.50); P < 0.001; TNFR-1: adjusted β = -6.86 (-10.25 to -3.47); P < 0.001; GDF-15: adjusted β = -7.07 (-10.02 to -4.12); P < 0.001]. Higher TNFR-1, MCP-1 and GDF-15 were associated with faster decline in four-domain IC over 4 years [TNFR-1: adjusted β (95% CI) = -1.28 (-2.29 to -0.27); P = 0.013; MCP-1: adjusted β = -1.33 (-2.24 to -0.42); P = 0.004; GDF-15: adjusted β = -1.42 (-2.26 to -0.58); P = 0.001]. None of the biomarkers was significantly associated with the five-domain IC decline.

CONCLUSIONS

Inflammation was associated with lower IC in older adults. Among all plasma biomarkers, TNFR-1 and GDF-15 were consistently associated with IC at the cross-sectional and longitudinal levels.

Insight into the effect of biomaterials on osteogenic differentiation of mesenchymal stem cells: A review from a mitochondrial perspective

Bone damage may be triggered by a variety of factors, and the damaged area often requires a bone graft. Bone tissue engineering can serve as an alternative strategy for repairing large bone defects. Mesenchymal stem cells (MSCs), the progenitor cells of connective tissue, have become an important tool for tissue engineering due to their ability to differentiate into a variety of cell types. The precise regulation of the growth and differentiation of the stem cells used for bone regeneration significantly affects the efficiency of this type of tissue engineering. During the process of osteogenic induction, the dynamics and function of localized mitochondria are altered. These changes may also alter the microenvironment of the therapeutic stem cells and result in mitochondria transfer. Mitochondrial regulation not only affects the induction/rate of differentiation, but also influences its direction, determining the final identity of the differentiated cell. To date, bone tissue engineering research has mainly focused on the influence of biomaterials on phenotype and nuclear genotype, with few studies investigating the role of mitochondria. In this review, we provide a comprehensive summary of researches into the role of mitochondria in MSCs differentiation and critical analysis regarding smart biomaterials that are able to "programme" mitochondria modulation was proposed. STATEMENT OF SIGNIFICANCE: : • This review proposed the precise regulation of the growth and differentiation of the stem cells used to seed bone regeneration. • This review addressed the dynamics and function of localized mitochondria during the process of osteogenic induction and the effect of mitochondria on the microenvironment of stem cells. • This review summarized biomaterials which affect the induction/rate of differentiation, but also influences its direction, determining the final identity of the differentiated cell through the regulation of mitochondria.

Inflammation produced by senescent osteocytes mediates age-related bone loss

Purpose

The molecular mechanisms of age-related bone loss are unclear and without valid drugs yet. The aims of this study were to explore the molecular changes that occur in bone tissue during age-related bone loss, to further clarify the changes in function, and to predict potential therapeutic drugs.

Methods

We collected bone tissues from children, middle-aged individuals, and elderly people for protein sequencing and compared the three groups of proteins pairwise, and the differentially expressed proteins (DEPs) in each group were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). K-means cluster analysis was then used to screen out proteins that continuously increased/decreased with age. Canonical signaling pathways that were activated or inhibited in bone tissue along with increasing age were identified by Ingenuity Pathway Analysis (IPA). Prediction of potential drugs was performed using the Connectivity Map (CMap). Finally, DEPs from sequencing were verified by Western blot, and the drug treatment effect was verified by quantitative real-time PCR.

Results

The GO and KEGG analyses show that the DEPs were associated with inflammation and bone formation with aging, and the IPA analysis shows that pathways such as IL-8 signaling and acute-phase response signaling were activated, while glycolysis I and EIF2 signaling were inhibited. A total of nine potential drugs were predicted, with rapamycin ranking the highest. In cellular experiments, rapamycin reduced the senescence phenotype produced by the H₂O₂-stimulated osteocyte-like cell MLO-Y4.

Conclusion

With age, inflammatory pathways are activated in bone tissue, and signals that promote bone formation are inhibited. This study contributes to the understanding of the molecular changes that occur in bone tissue during age-related bone loss and provides evidence that rapamycin is a drug of potential clinical value for this disease. The therapeutic effects of the drug are to be further studied in animals.

A Review of 3D Polymeric Scaffolds for Bone Tissue Engineering: Principles, Fabrication Techniques, Immunomodulatory Roles, and Challenges

Over the last few years, biopolymers have attracted great interest in tissue engineering and regenerative medicine due to the great diversity of their chemical, mechanical, and physical properties for the fabrication of 3D scaffolds. This review is devoted to recent advances in synthetic and natural polymeric 3D scaffolds for bone tissue engineering (BTE) and regenerative therapies. The review comprehensively discusses the implications of biological macromolecules, structure, and composition of polymeric scaffolds used in BTE. Various approaches to fabricating 3D BTE scaffolds are discussed, including solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, electrospinning, and sol-gel techniques. Rapid prototyping technologies such as stereolithography, fused deposition modeling, selective laser sintering, and 3D bioprinting are also covered. The immunomodulatory roles of polymeric scaffolds utilized for BTE applications are discussed. In addition, the features and challenges of 3D polymer scaffolds fabricated using advanced additive manufacturing technologies (rapid prototyping) are addressed and compared to conventional subtractive manufacturing techniques. Finally, the challenges of applying scaffold-based BTE treatments in practice are discussed in-depth.

Exosome-based bone-targeting drug delivery alleviates impaired osteoblastic bone formation and bone loss in inflammatory bowel diseases

Systematic bone loss is commonly complicated with inflammatory bowel diseases (IBDs) with unclear pathogenesis and uncertain treatment. In experimental colitis mouse models established by dextran sulfate sodium and IL-10 knockout induced with piroxicam, bone mass and quality are significantly decreased. Colitis mice demonstrate a lower bone formation rate and fewer osteoblasts in femur. Bone marrow mesenchymal stem/stromal cells (BMSCs) from colitis mice tend to differentiate into adipocytes rather than osteoblasts. Serum from patients with IBD promotes adipogenesis of human BMSCs. RNA sequencing reveals that colitis downregulates Wnt signaling in BMSCs. For treatment, exosomes with Golgi glycoprotein 1 inserted could carry Wnt agonist 1 and accumulate in bone via intravenous administration. They could alleviate bone loss, promote bone formation, and accelerate fracture healing in colitis mice. Collectively, BMSC commitment in inflammatory microenvironment contributes to lower bone quantity and quality and could be rescued by redirecting differentiation toward osteoblasts through bone-targeted drug delivery.

Inflammatory profile of incident cases of late-onset compared with young-onset rheumatoid arthritis: A nested cohort study

Objectives

To describe the characteristics of patients between late-onset rheumatoid arthritis (LORA) with young-onset (YORA), and analyze their association with cumulative inflammatory burden.

Methods

We performed a nested cohort study in a prospective cohort comprising 110 patients with rheumatoid arthritis (RA) and 110 age- and sex-matched controls. The main variable was cumulative inflammatory activity according to the 28-joint Disease Activity Score with erythrocyte sedimentation rate (DAS28-ESR). High activity was defined as DAS28 ≥ 3.2 and low activity as DAS28 < 3.2. The other variables recorded were inflammatory cytokines, physical function, and comorbid conditions. Two multivariate models were run to identify factors associated with cumulative inflammatory activity.

Results

A total of 22/110 patients (20%) met the criteria for LORA (≥ 60 years). Patients with LORA more frequently had comorbid conditions than patients with YORA and controls. Compared with YORA patients, more LORA patients had cumulative high inflammatory activity from onset [13 (59%) vs. 28 (31%); p = 0.018] and high values for CRP (p = 0.039) and IL-6 (p = 0.045). Cumulative high inflammatory activity in patients with RA was associated with LORA [OR (95% CI) 4.69 (1.49-10.71); p = 0.008], smoking [OR (95% CI) 2.07 (1.13-3.78); p = 0.017], anti-citrullinated peptide antibody [OR (95% CI) 3.24 (1.15-9.13); p = 0.025], average Health Assessment Questionnaire (HAQ) score [OR (95% CI) 2.09 (1.03-14.23); p = 0.034], and physical activity [OR (95% CI) 0.99 (0.99-0.99); p = 0.010]. The second model revealed similar associations with inflammatory activity in patients with LORA.

Conclusion

Control of inflammation after diagnosis is poorer and comorbidity more frequent in patients with LORA than in YORA patients and healthy controls.

Functional Heterogeneity Within Osteoclast Populations-a Critical Review of Four Key Publications that May Change the Paradigm of Osteoclasts

PURPOSE OF REVIEW

In this review, we critically evaluate the literature for osteoclast heterogeneity, including heterogeneity in osteoclast behavior, which has hitherto been unstudied and has only recently come to attention. We give a critical review centered on four recent high-impact papers on this topic and aim to shed light on the elusive biology of osteoclasts and focus on the variant features of osteoclasts that diverge from the classical viewpoint.

RECENT FINDINGS

Osteoclasts originate from the myeloid lineage and are best known for their unique ability to resorb bone. For decades, osteoclasts have been defined simply as multinucleated cells positive for tartrate-resistant acid phosphatase activity and quantified relative to the bone perimeter or surface in histomorphometric analyses. However, several recent, high-profile studies have demonstrated the existence of heterogeneous osteoclast populations, with variable origins and functions depending on the microenvironment. This includes long-term persisting osteoclasts, inflammatory osteoclasts, recycling osteoclasts (osteomorphs), and bone resorption modes. Most of these findings have been revealed through murine studies and have helped identify new targets for human studies. These studies have also uncovered distinct sets of behavioral patterns in heterogeneous osteoclast cultures. The underlying osteoclast heterogeneity likely drives differences in bone remodeling, altering patient risk for osteoporosis and fracture. Thus, identifying the underlying key features of osteoclast heterogeneity may help in better targeting bone diseases.

The promising roles of macrophages in geriatric hip fracture

As aging becomes a global burden, the incidence of hip fracture (HF), which is the most common fracture in the elderly population and can be fatal, is rapidly increasing, and its extremely high fatality rate places significant medical and financial burdens on patients. Fractures trigger a complex set of immune responses, and recent studies have shown that with aging, the immune system shows decreased activity or malfunctions in a process known as immune senescence, leading to disease and death. These phenomena are the reasons why elderly individuals typically exhibit chronically low levels of inflammation and increased rates of infection and chronic disease. Macrophages, which are key players in the inflammatory response, are critical in initiating the inflammatory response, clearing pathogens, controlling the innate and adaptive immune responses and repairing damaged tissues. Tissue-resident macrophages (TRMs) are widely present in tissues and perform immune sentinel and homeostatic functions. TRMs are combinations of macrophages with different functions and phenotypes that can be directly influenced by neighboring cells and the microenvironment. They form a critical component of the first line of defense in all tissues of the body. Immune system disorders caused by aging could affect the biology of macrophages and thus the cascaded immune response after fracture in various ways. In this review, we outline recent studies and discuss the potential link between monocytes and macrophages and their potential roles in HF in elderly individuals.

Pharmacological Approaches to Decelerate Aging: A Promising Path

Biological aging or senescence is a course in which cellular function decreases over a period of time and is a consequence of altered signaling mechanisms that are triggered in stressed cells leading to cell damage. Aging is among the principal risk factors for many chronic illnesses such as cancer, cardiovascular disorders, and neurodegenerative diseases. Taking this into account, targeting fundamental aging mechanisms therapeutically may effectively impact numerous chronic illnesses. Selecting ideal therapeutic options in order to hinder the process of aging and decelerate the progression of age-related diseases is valuable. Along therapeutic options, life style modifications may well render the process of aging. The process of aging is affected by alteration in many cellular and signaling pathways amid which mTOR, SIRT1, and AMPK pathways are the most emphasized. Herein, we have discussed the mechanisms of aging focusing mainly on the mentioned pathways as well as the role of inflammation and autophagy in aging. Moreover, drugs and natural products with antiaging properties are discussed in detail.

NAP1L2 drives mesenchymal stem cell senescence and suppresses osteogenic differentiation

Senescence of bone marrow mesenchymal stem cells (BMSCs) impairs stemness and osteogenic differentiation, but the key regulators for senescence and the related osteogenesis are not well defined. Herein, we screened the gene expression profiles of human BMSCs from young and old donors and identified that elevation of the nucleosome assembly protein 1‐like 2 (NAP1L2) expression was correlated with BMSC senescence and impaired osteogenesis. Elevated NAP1L2 expression was observed in replicative cell senescence and induced cell senescence in vitro, and in age‐related senescent human and mouse BMSCs in vivo, concomitant with significantly augmented chromatin accessibility detected by ATAC‐seq. Loss‐ and gain‐of‐functions of NAP1L2 affected activation of NF‐κB pathway, status of histone 3 lysine 14 acetylation (H3K14ac), and chromatin accessibility on osteogenic genes in BMSCs. Mechanistic studies revealed that NAP1L2, a histone chaperone, recruited SIRT1 to deacetylate H3K14ac on promoters of osteogenic genes such as Runx2, Sp7, and Bglap and suppressed the osteogenic differentiation of BMSCs. Importantly, molecular docking analysis showed a possible bond between NAP1L2 and an anti‐aging reagent, the nicotinamide mononucleotide (NMN), and indeed, administration of NMN alleviated senescent phenotypes of BMSCs. In vivo and clinical evidence from aging mice and patients with senile osteoporosis also confirmed that elevation of NAP1L2 expression was associated with suppressed osteoblastogenesis. Taken together, our findings suggest that NAP1L2 is a regulator of both BMSC cell senescence and osteogenic differentiation, and provide a new theoretical basis for aging‐related disease.

Anti-Inflammatory and Anti-Catabolic Effects of Creatine Supplementation: A Brief Review

It is well established that creatine supplementation, primarily when combined with resistance training, significantly increases measures of muscle mass and performance (primarily strength). Emerging research also indicates that creatine supplementation may have favorable effects on measures of bone biology. These anabolic adaptations may be related to creatine influencing cellular hydration status, high-energy phosphate metabolism, growth factors, muscle protein kinetics, and the bone remodeling process. Accumulating research also suggests that creatine supplementation has anti-inflammatory and anti-catabolic properties, which may help create a favorable environment for muscle and bone accretion and recovery from exercise. Creatine supplementation has the ability to decrease markers of inflammation and possibly attenuate cancerous tumor growth progression. From a musculoskeletal perspective, there is some evidence to show that creatine supplementation reduces measures of muscle protein catabolism (primarily in males) and bone resorption when combined with resistance training. The purpose of this brief review is to summarize the current body of literature examining the potential anti-inflammatory and anti-catabolic effects of creatine supplementation across various research populations.

Osteoimmune reaction caused by novel silicocarnotite bioceramic promoting osteogenesis through MAPK pathway

The host immune response to implant is a key factor in determining the fate of bone grafts, which is thought to be a regulator of tissue regeneration. Figuring out the...

The Cross-Talk between Myeloid and Mesenchymal Stem Cells of Human Bone Marrow Represents a Biomarker of Aging That Regulates Immune Response and Bone Reabsorption

One of the mechanisms that characterizes the aging process of different organs is the accumulation of fat. Different authors have demonstrated that adipose tissue replaces the loss of other cell types, deriving from mesenchymal cells. During aging, there is substitution or trans-differentiation of mesenchymal cells with other cells having the same embryological origin. Newly formed adipocytes were also observed in the trabecular matrix of elderly people’s bones, associated with myeloid cells. In this study, we have investigated the relationship between immature myeloid-derived suppressor cells (I-MDSCs) and mesenchymal stem cells (MSCs) in bone marrow (BM) samples harvested from 57 patients subjected to different orthopedic surgeries. Patients aged from 18 to 92 years were considered in order to compare the cellular composition of bone marrow of young and elderly people, considered a biomarker of immunity, inflammation, and bone preservation. The I-MDSC percentage was stable during aging, but in elderly people, it was possible to observe a strong basal immunosuppression of autologous and heterologous T cells’ proliferation. We hypothesized that this pattern observed in elders depends on the progressive accumulation in the BM of activating stimuli, including cell–cell contact, or the production of different cytokines and proteins that induce the differentiation of bone marrow mesenchymal stem cells in adipocytes. The collected data provided underline the importance of specific biomarkers of aging that promote a reduction in immune response and incremented inflammatory pathways, leading to bone reabsorption in elderly people.

Aging-Related Cellular, Structural and Functional Changes in the Lymph Nodes: A Significant Component of Immunosenescence? An Overview

Aging affects all tissues and organs. Aging of the immune system results in the severe disruption of its functions, leading to an increased susceptibility to infections, an increase in autoimmune disorders and cancer incidence, and a decreased response to vaccines. Lymph nodes are precisely organized structures of the peripheral lymphoid organs and are the key sites coordinating innate and long-term adaptive immune responses to external antigens and vaccines. They are also involved in immune tolerance. The aging of lymph nodes results in decreased cell transport to and within the nodes, a disturbance in the structure and organization of nodal zones, incorrect location of individual immune cell types and impaired intercellular interactions, as well as changes in the production of adequate amounts of chemokines and cytokines necessary for immune cell proliferation, survival and function, impaired naïve T- and B-cell homeostasis, and a diminished long-term humoral response. Understanding the causes of these stromal and lymphoid microenvironment changes in the lymph nodes that cause the aging-related dysfunction of the immune system can help to improve long-term immune responses and the effectiveness of vaccines in the elderly.

Methylsulfonylmethane Increases the Alveolar Bone Density of Mandibles in Aging Female Mice

Methylsulfonylmethane (MSM) is a naturally occurring anti-inflammatory compound that effectively treats multiple degenerative diseases such as osteoarthritis and acute pancreatitis. Our previous studies have demonstrated the ability of MSM to differentiate stem cells from human exfoliated deciduous (SHED) teeth into osteoblast-like cells. This study examined the systemic effect of MSM in 36-week-old aging C57BL/6 female mice in vivo by injecting MSM for 13 weeks. Serum analyses showed an increase in expression levels of bone formation markers [osteocalcin (OCN) and procollagen type 1 intact N-terminal propeptide (P1NP)] and a reduction in bone resorption markers [tartrate-resistant acid phosphatase (TRAP) and C-terminal telopeptide of type I collag (CTX-I)] in MSM-injected animals. Micro-computed tomographic images demonstrated an increase in trabecular bone density in mandibles. The trabecular bone density tended to be higher in the femur, although the increase was not significantly different between the MSM- and phosphate-buffered saline (PBS)-injected mice. In mandibles, an increase in bone density with a corresponding decrease in the marrow cavity was observed in the MSM-injected mice. Furthermore, immunohistochemical analyses of the mandibles for the osteoblast-specific marker - OCN, and the mesenchymal stem cell-specific marker - CD105 showed a significant increase and decrease in OCN and CD105 positive cells, respectively. Areas of bone loss were observed in the inter-radicular region of mandibles in control mice. However, this loss was considerably decreased due to stimulation of bone formation in response to MSM injection. In conclusion, our study has demonstrated the ability of MSM to induce osteoblast formation and function in vivo, resulting in increased bone formation in the mandible. Hence, the application of MSM and stem cells of interest may be the right combination in alveolar bone regeneration under periodontal or other related diseases that demonstrate bone loss.

Inflammation and sarcopenia: A focus on circulating inflammatory cytokines

Sarcopenia is an aged-related syndrome that is progressive and can be accelerated by other concomitant disease states. Sarcopenia, characterized by loss of skeletal muscle mass, reduced muscle strength, and/or reduced physical performance, is one of the main reasons for limitation of daily activities in the elderly. It is associated with an increased incidence of many adverse events, such as dysfunction, falls, weakness, hospitalization, disability and even death. Sarcopenia justifies one of the most widely accepted theories that low-grade chronic inflammation associated with aging, known as inflammatory aging, is important to the pathogenesis of many age-related diseases. Currently, the diagnosis of sarcopenia is based on a comprehensive assessment of three aspects: muscle mass, muscle strength and physical performance. The measurement of muscle mass is complicated, as the measurement of muscle strength and gait speed is easily affected by the physical conditions of the subjects. This makes the measurements inaccurate and prospective, and it is difficult to achieve continuous, purposeful monitoring. In addition, serum levels of inflammatory cytokines change as inflammatory states develop in the elderly population. This manuscript focuses on the correlation between serum inflammatory cytokines and sarcopenia in recent years, plus the possible underlying mechanisms.

ROS-Responsive Boronate-Stabilized Polyphenol-Poloxamer 188 Assembled Dexamethasone Nanodrug for Macrophage Repolarization in Osteoarthritis Treatment

Osteoarthritis (OA) is a disabling joint disease associated with chronic inflammation. The polarization of macrophages plays the key role in inflammatory microenvironment of joint which is a therapeutic target for OA treatment. Herein, a boronate-stabilized polyphenol-poloxamer assembled dexamethasone nanodrug with reactive oxygen species (ROS)-responsive drug release behavior and ROS scavenging ability is prepared. Thanks to that, the nanodrug can efficiently inhibit the ROS and nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages and modulate macrophages M2 polarization at a much lower concentration than free drug dexamethasone. Furthermore, the monosodium iodoacetate-induced OA mice treated with this nanodrug is very similar with the normal mice with the evaluation of body weight and scores including clinical arthritis scores, claw circumference, and kinematics score. The inflammation associated angiogenesis is also reduced which revealed by ⁶⁸ Ga-labeled arginine-glycine-aspartic acid peptide micro-positron emission tomography imaging. Cartilage degradation and bone erosion in the joints are also inhibited by the nanodrug, along with the inhibition of proinflammatory cytokines. In addition, the biosafety of this nanodrug is also verified. This nanodrug with excellent immunomodulation properties can be used not only for OA therapy but also for other inflammatory diseases associated with excess oxidative stress and macrophage polarization.

The multifaceted roles of macrophages in bone regeneration: A story of polarization, activation and time

To present knowledge, macrophages are found in all tissues of the human body. They are a cell population with high plasticity which come with a multitude of functions which appear to be adapted to the respective tissue niche and micro-environment in which they reside. Bone harbors multiple macrophage subpopulations, with the osteoclasts as classical representative of a bone resorbing cells and osteomacs as a bone tissue resident macrophage first described by the expression of F4/80. Both subtypes are found throughout all phases in bone healing. In vivo data on bone regeneration have demonstrated their essential role in initiating the healing cascade (inflammatory phase) but also of the later phases of healing (e.g. endochondral and intramembranous bone formation). To participate in such diverse processes macrophages have to be highly plastic in their functionality. Thus, the widely used M1/M2 paradigm to distinguish macrophage subpopulations may not mirror the comprehensive role of the dynamics of macrophage plasticity. From a clinical perspective it is especially relevant to distinguish what drives macrophages in impaired healing scenarios, implant loosening or infections, where their specific role of a misbalanced inflammatory setting is so far only partially known. With this review we aim at illustrating current knowledge and gaps of knowledge on macrophage plasticity and function during the cascades of regeneration and reconstitution of bone tissue. We propose aspects of the known biological mechanisms of macrophages and their specific subsets that might serve as targets to control their function in impaired healing and eventually support a scar-free regeneration. STATEMENT OF SIGNIFICANCE: Macrophages are essential for successful regeneration. In scar-free healing such as in bone, a complete failure of healing was shown if macrophages were depleted; the M1/M2 switch appears to be key to the progression from pro-inflammation to regeneration. However, experimental data illustrate that the classical M1/M2 paradigm does not completely mirror the complexity of observed macrophage functions during bone healing and thus demands a broader perspective. Within this review we discuss the high degree of plasticity of macrophages and the relevant contribution of the different and more specific M2 subtypes (M2a-M2f) during (bone) regeneration. It summarizes the versatile roles of macrophages in skeletal regeneration and thereby highlights potential target points for immunomodulatory approaches to enable or even foster bone repair.

An in situ tissue engineering scaffold with growth factors combining angiogenesis and osteoimmunomodulatory functions for advanced periodontal bone regeneration

Background

The regeneration of periodontal bone defect remains a vital clinical challenge. To date, numerous biomaterials have been applied in this field. However, the immune response and vascularity in defect areas may be key factors that are overlooked when assessing the bone regeneration outcomes of biomaterials. Among various regenerative therapies, the up-to-date strategy of in situ tissue engineering stands out, which combined scaffold with specific growth factors that could mimic endogenous regenerative processes.

Results

Herein, we fabricated a core/shell fibrous scaffold releasing basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) in a sequential manner and investigated its immunomodulatory and angiogenic properties during periodontal bone defect restoration. The in situ tissue engineering scaffold (iTE-scaffold) effectively promoted the angiogenesis of periodontal ligament stem cells (PDLSCs) and induced macrophage polarization into pro-healing M2 phenotype to modulate inflammation. The immunomodulatory effect of macrophages could further promote osteogenic differentiation of PDLSCs in vitro. After being implanted into the periodontal bone defect model, the iTE-scaffold presented an anti-inflammatory response, provided adequate blood supply, and eventually facilitated satisfactory periodontal bone regeneration.

Conclusions

Our results suggested that the iTE-scaffold exerted admirable effects on periodontal bone repair by modulating osteoimmune environment and angiogenic activity. This multifunctional scaffold holds considerable promise for periodontal regenerative medicine and offers guidance on designing functional biomaterials.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00992-4.

3D Cocultures of Osteoblasts and Staphylococcus aureus on Biomimetic Bone Scaffolds as a Tool to Investigate the Host-Pathogen Interface in Osteomyelitis

Osteomyelitis (OM) is an infectious disease of the bone primarily caused by the opportunistic pathogen Staphylococcus aureus (SA). This Gram-positive bacterium has evolved a number of strategies to evade the immune response and subvert bone homeostasis, yet the underlying mechanisms remain poorly understood. OM has been modeled in vitro to challenge pathogenetic hypotheses in controlled conditions, thus providing guidance and support to animal experimentation. In this regard, traditional 2D models of OM inherently lack the spatial complexity of bone architecture. Three-dimensional models of the disease overcome this limitation; however, they poorly reproduce composition and texture of the natural bone. Here, we developed a new 3D model of OM based on cocultures of SA and murine osteoblastic MC3T3-E1 cells on magnesium-doped hydroxyapatite/collagen I (MgHA/Col) scaffolds that closely recapitulate the bone extracellular matrix. In this model, matrix-dependent effects were observed in proliferation, gene transcription, protein expression, and cell–matrix interactions both of the osteoblastic cell line and of bacterium. Additionally, these had distinct metabolic and gene expression profiles, compared to conventional 2D settings, when grown on MgHA/Col scaffolds in separate monocultures. Our study points to MgHA/Col scaffolds as biocompatible and bioactive matrices and provides a novel and close-to-physiology tool to address the pathogenetic mechanisms of OM at the host–pathogen interface.

Advancing application of mesenchymal stem cell-based bone tissue regeneration

Reconstruction of bone defects, especially the critical-sized defects, with mechanical integrity to the skeleton is important for a patient's rehabilitation, however, it still remains challenge. Utilizing biomaterials of human origin bone tissue for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural bone tissue with regard to its properties. However, not only efficacious and safe but also cost-effective and convenient are important for regenerative biomaterials to achieve clinical translation and commercial success. Advances in our understanding of regenerative biomaterials and their roles in new bone formation potentially opened a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multicomponent construction of native extracellular matrix (ECM) for cell accommodation, the ECM-mimicking biomaterials and the naturally decellularized ECM scaffolds were used to create new tissues for bone restoration. On the other hand, with the going deep in understanding of mesenchymal stem cells (MSCs), they have shown great promise to jumpstart and facilitate bone healing even in diseased microenvironments with pharmacology-based endogenous MSCs rescue/mobilization, systemic/local infusion of MSCs for cytotherapy, biomaterials-based approaches, cell-sheets/-aggregates technology and usage of subcellular vesicles of MSCs to achieve scaffolds-free or cell-free delivery system, all of them have been shown can improve MSCs-mediated regeneration in preclinical studies and several clinical trials. Here, following an overview discussed autogenous/allogenic and ECM-based bone biomaterials for reconstructive surgery and applications of MSCs-mediated bone healing and tissue engineering to further offer principles and effective strategies to optimize MSCs-based bone regeneration.

Abnormal macrophage polarization impedes the healing of diabetes-associated tooth sockets

Patients with poorly controlled type 2 diabetes mellitus (T2DM) often experience delayed tooth extraction socket (TES) healing. Delayed healing is often associated with an aberrant inflammatory response orchestrated by either M1 pro-inflammatory or M2 anti-inflammatory macrophages. However, the precise mechanism for the attenuated TES healing remains unclear. Here we used diet-induced T2DM mice as a model to study TES. Compared with the control group, the T2DM group showed delayed TES healing and diminished expression of osteogenic and angiogenic genetic profiles. Meanwhile, we detected a more inflammatory profile, with more M1 macrophages and TNF-α expression and less M2 macrophages and PPARγ expression, in TES in the T2DM group when compared to control mice. In vitro co-culture models showed that M1 macrophages inhibited the osteogenic capacity of bone marrow stromal cells and the angiogenic capacity of endothelial cells while M2 macrophages showed an opposite effect. In addition, we constructed a gelatin/β-TCP scaffold with IL-4 to induce macrophage transformation towards M2 polarization. In vitro analyses of the hybrid scaffold revealed sustained release of IL-4 and a phenotype switch to M2 macrophages. Finally, we demonstrated that sustained IL-4 release significantly increased expression of osteogenic and angiogenic genetic profiles and improved TES healing in T2DM mice. Together, we report that increased M1 and decreased M2 macrophage polarization may be responsible for delayed TES healing in T2DM patients through abnormal expression of TNF-α and PPARγ. This imbalance negatively influences osteogenesis and angiogenesis, two of the most important biological factors in bone wound healing. Enhancing M2 macrophage polarization with IL-4 delivery system may represent a potential strategy for promoting the healing of TES in T2DM patients.

Effects of Creatine Supplementation on Properties of Muscle, Bone, and Brain Function in Older Adults: A Narrative Review

Aging is associated with reductions in muscle and bone mass and brain function, which may be counteracted by several lifestyle factors, of which exercise appears to be most beneficial. However, less than 20% of older adults (> 55 years of age) adhere to performing the recommended amount of resistance training (≥ 2 days/week) and less than 12% regularly meet the aerobic exercise guidelines (≥ 150 min/week of moderate to vigorous intensity aerobic exercise) required to achieve significant health benefits. Therefore, from a healthy aging and clinical perspective, it is important to determine whether other lifestyle interventions (independent of exercise) can have beneficial effects on aging muscle quality and quantity, bone strength, and brain function. Creatine, a nitrogen containing organic compound found in all cells of the body, has the potential to have favorable effects on muscle, bone, and brain health (independent of exercise) in older adults. The purpose of this narrative review is to examine and summarize the small body of research investigating the effects of creatine supplementation alone on measures of muscle mass and performance, bone mineral and strength, and indices of brain health in older adults.

Bone Mineral Density in Severely Obese Women: Health Risk and Health Protective Risk Factors in Three Different Bone Sites

Factors associated with bone mineral density (BMD) are poorly known in severely obese individuals i.e., a body mass index (BMI) > 35 kg/m2. The objectives of this study were to describe the bone health profile of severely obese Brazilian women, to identify the health risk and health protective factors for BMD in this group and to assess whether these factors vary according to three different bone sites. BMD was assessed using dual-energy X-ray absorptiometry (DXA). This study analyzed baseline data from 104 women who had an average BMI of 43.7 ± 4.5 kg/m2 and presented the following BMD status: 1.283 ± 0.094 g/cm2 for total body, 1.062 ± 0.159 g/cm2 for vertebral column and 1.195 ± 0.134 g/cm2 for hip. They took part in the "Effect of nutritional intervention and olive oil in severe obesity" randomized clinical trial (DieTBra Trial). The risk factors negatively associated with lower BMD were age ≥50 years for the three bone sites i.e., total body, vertebral column and hip. Smoking for total body BMD (p = 0.045); BMI ≥ 50kg/m2 for vertebral column and hip; menopause for hip; high C-reactive protein (CRP) levels (p = 0.049), insufficient zinc (p = 0.010) and previous fracture for vertebral column (p = 0.007). The protective factors positively associated with BMD were physical activity (≥150 min/week (p = 0.001)) for hip; type 2 diabetes mellitus (DM2) (p < 0.0001) total body and adequate vitamin D levels from food consumption (p = 0.039) for vertebral column. A BMI ≥ 50 kg/m2 was a risk factor for lower BMD. The findings showed that protective and risk factors varied by bone site. The original study is registered with ClinicalTrials.gov. (protocol number: NCT02463435).