Binding-induced fibrillogenesis peptide inhibits RANKL-mediated osteoclast activation against osteoporosis

Self-assembled water soluble and bone-targeting phosphorylated quercetin ameliorates postmenopausal osteoporosis in ovariectomy mice

Natural compounds have shown promising application prospects in preventing or treating various diseases, including osteoporosis on account of their abundant sources, low price, multi-targeting and multiple biological effects. As a bioactive natural product, quercetin (Que) has previously demonstrated to ameliorate osteoporosis (OP), however, its poor bioavailability resulting from low water solubility, poor stability and lack of bone-targeting largely restricted its efficacy and clinical applications. Inspired by the bone-targeting capability of phosphate compounds, we reported a one-step procedure for synthesis of phosphorylated Que (p-Que) by direct phosphorylating phenol groups of Que for the first time. The phosphate groups on p-Que could not only improve the water dispersibility of Que, but also endow p-Que desirable bioavailability and bone-targeting feature. The results from biological assays suggested that p-Que could inhibit osteoclastogenesis and bone resorption and alleviate trabeculae loss in osteoporotic mice. In conclusion, this work demonstrated that phosphorylation strategy can effectively solve low water solubility, lack of bone-targeting capability and poor bioavailability of natural compounds, providing a novel and efficient approach for development of OP nanomedicines.

RNA interference-mediated osteoprotegerin silencing increases the receptor activator of nuclear factor-kappa B ligand/osteoprotegerin ratio and promotes osteoclastogenesis

BACKGROUND

In vivo degradation of bone scaffolds is significantly influenced by osteoclast (OC) activity, which is orchestrated by the interplay between receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG). The ratio of RANKL/OPG is a crucial determinant of OC-mediated bone resorption, which plays an integral role in bone remodeling and scaffold degradation. Elevated levels of RANKL relative to OPG enhance osteoclastogenesis, thereby accelerating the degradation process essential for integrating bone scaffolds into the host tissue.

AIM

To elucidate the effects of OPG gene silencing on osteoclastogenesis within rat bone marrow-derived mesenchymal stem cells (BMSCs). By investigating these effects, the study aimed to provide deeper insights into the regulatory mechanisms that influence bone scaffold degradation, potentially leading to improved bone repair and regeneration strategies.

METHODS

We employed recombinant lentiviral plasmids to silence the OPG gene in rat BMSCs to achieve the aims. The efficacy of gene silencing was assessed using quantitative reverse transcription polymerase chain reaction and western blot analysis to measure the expression levels of OPG and RANKL. Tartrate-resistant acid phosphatase staining was utilized to evaluate the formation of OCs. Additionally, co-immunoprecipitation assays were conducted to explore the interactions between RANKL and OPG proteins, further assessing the biochemical pathways involved in osteoclastogenesis.

RESULTS

The silencing of the OPG gene in BMSCs resulted in a significant increase in the RANKL/OPG ratio, evidenced by decreased expression levels of OPG and increased levels of RANKL. Enhanced osteoclastogenesis was observed through tartrate-resistant acid phosphatase staining, which indicated a substantial rise in OC formation in response to the altered RANKL/OPG balance. The co-immunoprecipitation assays provided concrete evidence of the direct interaction between RANKL and OPG proteins, substantiating their pivotal roles in regulating OC activity.

CONCLUSION

The findings from this study underscore the critical role of the RANKL/OPG axis in osteoclastogenesis. Silencing of the OPG gene in BMSCs effectively increases the RANKL/OPG ratio, promoting OC activity and potentially enhancing bone scaffold degradation. This regulatory mechanism offers a promising avenue for modulating bone remodeling processes, which is essential for effective bone repair and the successful integration of bone scaffolds into damaged sites. Future research might focus on optimizing the control of this axis to better facilitate bone tissue engineering and regenerative therapies.

In Situ Biomimetic Glycocalyx Layer Protects Endothelial Damage in Xenotransplantation

Xenotransplantation offers a transformative solution to the global organ shortage crisis. However, the survival of xenografts remains limited despite various proposed strategies. In this study, we present an endothelial cell protection strategy that extends graft survival through the in situ construction of biomimetic glycan-enriched nanofibers. These biomimetic glycan-enriched molecules specifically target integrin αvβ3 and form a polysaccharide-structured nanofiber network on the vascular endothelial surface. This network protects endothelial cells without compromising their normal physiological functions. The constructed biomimetic glycan-enriched layer significantly increased the xenograft survival by 1.64-fold compared to the untreated groups. This work introduces a novel strategy to enhance the survival of heart xenografts.

Lysyl oxidase nanozyme-loaded hydrogel for sustained release and promotion of diabetic bone defect regeneration

The process of regenerating bone injuries in diabetic presents significant challenges because lysine oxidase (LOX), a key catalytic enzyme for collagen cross-linking, is inhibited in hyperglycemia. The supplementation of LOX is constrained by inadequate sources and diminished enzymatic activity, necessitating the development of effective alternatives for enhancing bone regeneration in diabetes. Herein, we reported a lysyl oxidase nanozyme (LON), derived from the catalytic domain of LOX. LON formed a stable coordination structure with the active center Cu2+ through histidine imidazolyl nitrogen and quinone oxygen, which is consistent with the conformation of the LOX. Our findings suggested that LON demonstrated the capacity to substitute LOX in promoting collagen synthesis and biomineralization. To enable sustained LON delivery, it was incorporated into a GelMA hydrogel (GH), forming a sustained-release reservoir known as LON-GelMA hydrogel (LONGH). Mechanism of LONGH promoting bone healing to accelerate the crosslinking and maturation stage of collagen were also explored, and the 23 genes closely associated with collagen regeneration and osteogenesis were found to be upregulated. The present investigation outcomes reveal that the engineered LONGH hydrogel presents a novel, simple, and commercially viable approach for bone regeneration, offering significant potential for clinical applications.

Biomaterial Cues for Regulation of Osteoclast Differentiation and Function in Bone Regeneration

Tissue regeneration involves dynamic dialogue between and among different cells and their surrounding matrices. Bone regeneration is specifically governed by reciprocity between osteoblasts and osteoclasts within the bone microenvironment. Osteoclast-directed resorption and osteoblast-directed formation of bone are essential to bone remodeling, and the crosstalk between these cells is vital to curating a sequence of events that culminate in the creation of bone tissue. Among bone biomaterial strategies, many have investigated the use of different material cues to direct the development and activity of osteoblasts. However, less attention has been given to exploring features that similarly target osteoclast formation and activity, with even fewer strategies demonstrating or integrating biomaterial-directed modulation of osteoblast-osteoclast coupling. This review aims to describe various biomaterial cues demonstrated to influence osteoclastogenesis and osteoclast function, emphasizing those that enhance a material construct's ability to achieve bone healing and regeneration. Additionally discussed are approaches that influence the communication between osteoclasts and osteoblasts, particularly in a manner that takes advantage of their coupling. Deepening our understanding of how biomaterial cues may dictate osteoclast differentiation, function, and influence on the microenvironment may enable the realization of bone-replacement interventions with enhanced integrative and regenerative capacities.

Modified Zuo Gui Wan Ameliorates Ovariectomy-Induced Osteoporosis in Rats by Regulating the SCFA-GPR41-p38MAPK Signaling Pathway

Objective

Modified Zuo Gui Wan (MZGW) was a combination of Zuo Gui Wan and red yeast rice used for treating osteoporosis (OP), but its mechanism remains unclear. We aimed to validate the anti-OP effect of MZGW and explore its underlying mechanism.

Methods

An ovariectomy (OVX) rat model in vivo and a RANKL-induced osteoclasts (OCs) model in vitro were established. Key active ingredients in MZGW high dose (MZGW-H) group were detected by UPLC-MS/MS. Micro-CT scans and histomorphology analysis were performed in OVX rats. 16S rRNA gene sequencing was performed to investigate the relationship between the anti-OP effect of MZGW-H and intestinal flora. CCK-8 assay was applied to examine the optimal concentration of Modified Zuo Gui Wan drug serum (MZGW-DS) on osteoclasts. The qRT-PCR and Western blotting were utilized to explore the potential anti-OP pathway of MZGW, namely the SCFA-GPR41-p38MAPK signaling pathway. GPR41 was knocked down to further reverse to verify whether the pathway was the key pathway for MZGW-DS to exert its inhibitory effect on osteoclasts.

Results

The three main blood components, Ferulic acid, L-Ascorbic acid and Riboflavin, were examined mainly by UPLC-MS/MS. 16S rRNA gene sequencing showed that MZGW-H changed the metabolism of SCFAs. In vivo studies verified that MZGW-H ameliorated microstructure damage, improved histological changes and reduced TRAP, BALP, and BGP in OVX rats by regulating the SCFA-GPR41-p38MAPK signaling pathway. CCK-8 revealed that 5% MZGW-DS group was the most optimal concentration of MZGW-DS to inhibit osteoclast differentiation. In vitro, MZGW-DS was better than peripheral blood concentration of SCFAs in inhibiting osteoclasts. After the knockout of GPR41, MZGW-DS could not inhibit the expression of osteoclast-related protein (CTSK and NFATc1) via SCFA-GPR41-p38MAPK signaling pathway.

Conclusion

MZGW-H effectively ameliorates OVX-induced osteoporosis partially achieved by increasing SCFAs metabolism and modulating the SCFA-GPR41-p38MAPK signaling pathway.

Bioactive peptides and proteins for tissue repair: microenvironment modulation, rational delivery, and clinical potential

Bioactive peptides and proteins (BAPPs) are promising therapeutic agents for tissue repair with considerable advantages, including multifunctionality, specificity, biocompatibility, and biodegradability. However, the high complexity of tissue microenvironments and their inherent deficiencies such as short half-live and susceptibility to enzymatic degradation, adversely affect their therapeutic efficacy and clinical applications. Investigating the fundamental mechanisms by which BAPPs modulate the microenvironment and developing rational delivery strategies are essential for optimizing their administration in distinct tissue repairs and facilitating clinical translation. This review initially focuses on the mechanisms through which BAPPs influence the microenvironment for tissue repair via reactive oxygen species, blood and lymphatic vessels, immune cells, and repair cells. Then, a variety of delivery platforms, including scaffolds and hydrogels, electrospun fibers, surface coatings, assisted particles, nanotubes, two-dimensional nanomaterials, and nanoparticles engineered cells, are summarized to incorporate BAPPs for effective tissue repair, modification strategies aimed at enhancing loading efficiencies and release kinetics are also reviewed. Additionally, the delivery of BAPPs can be precisely regulated by endogenous stimuli (glucose, reactive oxygen species, enzymes, pH) or exogenous stimuli (ultrasound, heat, light, magnetic field, and electric field) to achieve on-demand release tailored for specific tissue repair needs. Furthermore, this review focuses on the clinical potential of BAPPs in facilitating tissue repair across various types, including bone, cartilage, intervertebral discs, muscle, tendons, periodontal tissues, skin, myocardium, nervous system (encompassing brain, spinal cord, and peripheral nerve), endometrium, as well as ear and ocular tissue. Finally, current challenges and prospects are discussed.

Novel osteogenic peptide from bovine bone collagen hydrolysate: Targeted screening, molecular mechanism, and stability analysis

This study aimed to screen for a novel osteogenic peptide based on the calcium-sensing receptor (CaSR) and explore its molecular mechanism and gastrointestinal stability. In this study, a novel osteogenic peptide (Phe-Ser-Gly-Leu, FSGL) derived from bovine bone collagen hydrolysate was successfully screened by molecular docking and synthesised by solid phase peptide synthesis for further analysis. Cell experiments showed that FSGL significantly enhanced the osteogenic activity of MC3T3-E1 cells by acting on CaSR, including proliferation (152.53%), differentiation, and mineralization. Molecular docking and molecular dynamics further demonstrated that FSGL was a potential allosteric activator of CaSR, that turned on the activation switch of CaSR by closing the Venus flytrap (VFT) domain and driving the two protein chains in the VFT domain to easily form dimers. In addition, 96.03% of the novel osteogenic peptide FSGL was stable during gastrointestinal digestion. Therefore, FSGL showed substantial potential for enhancing the osteogenic activity of osteoblasts. This study provided new insights for the application of CaSR in the targeted screening of osteogenic peptides to improve bone health.

Identification and functional analysis of genes mediating osteoclast-driven progression of osteoporosis

OBJECTIVE

The pathological mechanism of osteoporosis (OP) involves increased bone resorption mediated by osteoclasts and decreased bone formation mediated by osteoblasts, leading to an imbalance in bone homeostasis. Identifying key molecules in osteoclast-mediated OP progression is crucial for the prevention and treatment of OP.

METHODS

Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were performed on the OP patient datasets from the GEO database. The results were intersected with the differential expression results from the osteoclast differentiation dataset to identify key genes. These key genes were then subjected to disease relevance analysis, and consensus clustering was performed on OP patient samples based on their expression profiles. The subgroups were analyzed for differences, followed by GO, KEGG, GSEA, and GSVA analyses, and immune infiltration. Finally, osteoclast differentiation model was constructed. After validating the success of the model using TRAP and F-actin staining, the differential expression of key genes was validated in vitro via Western blot.

RESULTS

CTRL, ARHGEF5, PPAP2C, VSIG2, and PBLD were identified as key genes. These genes exhibited strong disease relevance (AUC > 0.9). Functional enrichment results also indicated their close association with OP and osteoclast differentiation. In vitro differential expression validation showed that during osteoclast differentiation, CTRL was downregulated, while ARHGEF5, PPAP2C, VSIG2, and PBLD were upregulated, with all differences being statistically significant (P < 0.05).

DISCUSSION

Currently, there are no studies on the effects of these five genes on osteoclast differentiation. Therefore, it is meaningful to design in vivo and in vitro perturbation experiments to observe the impact of each gene on osteoclast differentiation and OP progression.

CONCLUSION

CTRL, ARHGEF5, PPAP2C, VSIG2, and PBLD show high potential as molecular targets for basic and clinical research in osteoclast-mediated OP.

Elucidating causal relationships of diet-derived circulating antioxidants and the risk of osteoporosis: A Mendelian randomization study

Background

Osteoporosis (OP) is typically diagnosed by evaluating bone mineral density (BMD), and it frequently results in fractures. Here, we investigated the causal relationships between diet-derived circulating antioxidants and the risk of OP using Mendelian randomization (MR).

Methods

Published studies were used to identify instrumental variables related to absolute levels of circulating antioxidants like lycopene, retinol, ascorbate, and β-carotene, as well as antioxidant metabolites such as ascorbate, retinol, α-tocopherol, and γ-tocopherol. Outcome variables included BMD (in femoral neck, lumbar spine, forearm, heel, total body, total body (age over 60), total body (age 45-60), total body (age 30-45), total body (age 15-30), and total body (age 0-15)), fractures (in arm, spine, leg, heel, and osteoporotic fractures), and OP. Inverse variance weighted or Wald ratio was chosen as the main method for MR analysis based on the number of single nucleotide polymorphisms (SNPs). Furthermore, we performed sensitivity analyses to confirm the reliability of the findings.

Results

We found a causal relationship between absolute retinol levels and heel BMD (p = 7.6E-05). The results of fixed effects IVW showed a protective effect of absolute retinol levels against heel BMD, with per 0.1 ln-transformed retinol being associated with a 28% increase in heel BMD (OR: 1.28, 95% CI: 1.13-1.44). In addition, a sex-specific effect of the absolute circulating retinol levels on the heel BMD has been observed in men. No other significant causal relationship was found.

Conclusion

There is a positive causal relationship between absolute retinol levels and heel BMD. The implications of our results should be taken into account in future studies and in the creation of public health policies and OP prevention tactics.

Inflammatory microenvironment regulation and osteogenesis promotion by bone-targeting calcium and magnesium repletion nanoplatform for osteoporosis therapy

Osteoporosis is the most common bone metabolic disease that affects the health of middle-aged and elderly people, which is hallmarked by imbalanced bone remodeling and a deteriorating immune microenvironment. Magnesium and calcium are pivotal matrix components that participate in the bone formation process, especially in the immune microenvironment regulation and bone remodeling stages. Nevertheless, how to potently deliver magnesium and calcium to bone tissue remains a challenge. Here, we have constructed a multifunctional nanoplatform composed of calcium-based upconversion nanoparticles and magnesium organic frameworks (CM-NH2-PAA-Ald, denoted as CMPA), which features bone-targeting and pH-responsive properties, effectively regulating the inflammatory microenvironment and promoting the coordination of osteogenic functions for treating osteoporosis. The nanoplatform can efficaciously target bone tissue and gradually degrade in response to the acidic microenvironment of osteoporosis to release magnesium and calcium ions. This study validates that CMPA possessing favorable biocompatibility can suppress inflammation and facilitate osteogenesis to treat osteoporosis. Importantly, high-throughput sequencing results demonstrate that the nanoplatform exerts a good inflammatory regulation effect through inhibition of the nuclear factor kappa-B signaling pathway, thereby normalizing the osteoporotic microenvironment. This collaborative therapeutic strategy that focuses on improving bone microenvironment and promoting osteogenesis provides new insight for the treatment of metabolic diseases such as osteoporosis.

The critical role of toll-like receptor 4 in bone remodeling of osteoporosis: from inflammation recognition to immunity

Osteoporosis is a common chronic metabolic bone disorder. Recently, increasing numbers of studies have demonstrated that Toll-like receptor 4 (TLR4, a receptor located on the surface of osteoclasts and osteoblasts) plays a pivotal role in the development of osteoporosis. Herein, we performed a comprehensive review to summarize the findings from the relevant studies within this topic. Clinical data showed that TLR4 polymorphisms and aberrant TLR4 expression have been associated with the clinical significance of osteoporosis. Mechanistically, dysregulation of osteoblasts and osteoclasts induced by abnormal expression of TLR4 is the main molecular mechanism underlying the pathological processes of osteoporosis, which may be associated with the interactions between TLR4 and NF-κB pathway, proinflammatory effects, ncRNAs, and RUNX2. In vivo and in vitro studies demonstrate that many promising substances or agents (i.e., methionine, dioscin, miR-1906 mimic, artesunate, AEG-1 deletion, patchouli alcohol, and Bacteroides vulgatus) have been able to improve bone metabolism (i.e., inhibits bone resorption and promotes bone formation), which may partially attribute to the inhibition of TLR4 expression. The present review highlights the important role of TLR4 in the clinical significance and the pathogenesis of osteoporosis from the aspects of inflammation and immunity. Future therapeutic strategies targeting TLR4 may provide a new insight for osteoporosis treatment.