Mangiferin promotes osteogenic differentiation and alleviates osteoporosis in the ovariectomized mouse via the AXL/ERK5 pathway

Evaluation of the effects of Mangiferin on human lymphocytes of healthy individuals and the balance of Th1 and Th2

Mangiferin is a xanthone glycoside that can be found abundantly in different parts of plants, with fruits like figs containing significant amounts. This study aimed to examine the immunomodulatory effects of Mangiferin on helper T lymphocytes. They were exposed to different concentrations of Mangiferin (10, 30, and 100 μM) and dexamethasone (0.1 mM) in the presence of phytohemagglutinin (PHA). The levels of cell proliferation, nitric oxide (NO), malondialdehyde (MDA), and glutathione (GSH) were determined using biochemical techniques. In addition, the levels of messenger RNA for interferon-γ (IFN-γ), interleukin-4 (IL-4), and IL-10 were measured through real-time PCR. The values for IFN-γ/IL-4 (Th1/Th2), IFN-γ/IL-10 (Th1/Treg), and IL-4/IL-10 (Th2/Treg) ratios were calculated by dividing their respective values. In the PHA-stimulated group, there was a notable decrease in IFN-γ/IL-4 and GSH levels, while other factors showed a significant increase compared to the control. Mangiferin significantly reduced cell proliferation, MDA/GSH ratio, MDA, and NO production. Additionally, Mangiferin demonstrated a concentration-dependent decrease in IFN-γ and IL-4 levels and an increase in IL-10 levels compared to the PHA group. The two higher concentrations of Mangiferin notably decreased the IFN-γ, IFN-γ/IL-10, and IL-4/IL-10 ratio values. Mangiferin exhibits more specific anti-oxidant, anti-inflammatory, and immunomodulatory activities compared to dexamethasone.

Enhanced Long-Term Antibacterial and Osteogenic Properties of Silver-Loaded Titanium Dioxide Nanotube Arrays for Implant Applications

Objective

This study explored constructing silver-loaded titanium dioxide nanotube (TiO2 NT) arrays on titanium surfaces using anodic oxidation combined with ion implantation. We assessed the cytocompatibility, antibacterial properties, and osteogenic potential of these silver-loaded TiO2 NT arrays, along with the underlying mechanisms.

Methods

We utilized anodization to create TiO2 NT arrays and employed ion implantation to load silver ions, categorizing samples into groups NT-Ag-II-L, NT-Ag-II-M, and NT-Ag-II-H based on different Ag ion dosages. Characterization was performed via scanning electron microscopy (SEM). We evaluated cell compatibility and assessed the antimicrobial performance and Ag ion release profiles. The osteogenic ability of the samples was measured, and the effects on ERK5 and osteogenesis-related factors were analyzed. To clarify the role of ERK5 in osteogenesis, we inhibited the ERK5 pathway using BIX02188 and subsequently re-evaluated osteogenic capacity in co-cultured cells.

Results

SEM analysis showed that in the NT-Ag-II-M group, Ag ions exhibited a flake-like distribution atop the TiO2 NTs, while NT-Ag-II-L and NT-Ag-II-H groups presented clustered grid structures. Energy-filtered transmission electron microscopy (EFTEM) confirmed orderly Ag ion arrangements within the lumens of the nanotubes. Notably, the silver-loaded TiO2 NT arrays did not inhibit MC3T3-E1 cell proliferation and enhanced early cellular adhesion. All samples displayed significant antimicrobial activity initially, which decreased after seven days; however, Ag ion release decreased gradually over the first 14 days before stabilizing. Additionally, the samples increased alkaline phosphatase activity, collagen secretion, and extracellular matrix mineralization, up-regulating ERK5 and other osteogenic factors. Inhibition of the ERK5 pathway suppressed the osteogenic capabilities of the samples.

Conclusion

Anodization and ion implantation successfully produced silver-loaded TiO2 NT arrays on titanium surfaces, demonstrating no cytotoxicity, sustained antimicrobial properties, and enhanced osteogenic potential. The antimicrobial effect relates to silver ion release, whereas osteogenesis is promoted by ERK5 signaling triggered by silver ions.

Mangiferin- and GNPs/ECPP-loaded platform of UH with dual bi-directional dynamic modulation of stem cells/macrophages and osteoblasts/osteoclasts for the prevention of aseptic loosening

Aseptic inflammation and osteolysis triggered by the phagocytosis of implant wear particles by macrophages are important reasons for aseptic loosening (AL) in total joint replacement, which ultimately leads to implant failure. Therefore, the development of implants with long-term effectiveness in preventing AL is a pressing issue. In contrast to the conventional idea of reducing the occurrence of AL through anti-inflammatory treatment, we prepared implants based on a novel concept: to prevent AL by returning the dynamic balance of osteogenesis/osteolysis through dynamic modulation, which is expected to completely resolve the problem of AL. In this study, a natural polyphenol, mangiferin (MAN), and a composite filler (GNPs/ECPP) were loaded into ultrahigh-molecular-weight polyethylene (UH) to construct a hip implant component with the ability to prevent AL. This modified implant was able to improve the oxidation resistance and wear resistance of implants, which could reduce the production of wear particles, recruit BMSCs as well as promote their proliferation/osteogenic differentiation and inhibit macrophage activity and RANKL-induced macrophage osteoclast differentiation in vitro. These effects suggest that this modified implant has achieved the dual bi-directional dynamic modulation of stem cells/macrophages and osteoblasts/osteoclasts for the prevention of aseptic loosening. Notably, in vivo experiments for implantation of wear-particle-coated titanium rods demonstrated that wear particles from the prepared implant significantly promoted the osseointegration capacity of implanted prosthesis (titanium rod) and effectively inhibited peri-prosthesis osteolysis. This work provides a new concept and presents a promising way for the development of durable implant components with long-term protection against AL.

Heraclenin promotes the osteogenic differentiation of bone marrow stromal cells by activating the RhoA/ROCK pathway

BACKGROUND

Osteoporosis is a devastating skeletal disease, the pathogenesis of which is related to abnormal bone metabolism, featured by the imbalance between osteoblastic bone formation and osteoclastic bone resorption. Stem cell-based therapies have been demonstrated to improve osteoporosis treatment. Previously, the linear furanocoumarin heraclenin was reported to enhance osteoblast differentiation and mineralization in mouse mesenchymal stem cells (MSCs), suggesting its potential for osteogenic differentiation and bone regeneration. Our study was designed to confirm the promotive role of heraclenin on osteogenic differentiation of human bone MSCs (BMSCs) and explore the underlying mechanisms.

METHODS

Human BMSCs were treated for 24, 48, and 72h with heraclenin (5, 10, 20, 40, and 80 μM), and cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. To further evaluate the cytotoxicity of heraclenin, cell suspension obtained from BMSCs treated with heraclenin (5, 10, and 20 μM) for 72h was subjected to a MUSE™ cell analyzer for cell viability and count assay. BMSCs were incubated in osteogenic induction medium for 7 days. Then, osteogenic differentiation and mineralization of BMSCs were assessed through alkaline phosphatase (ALP) and Alizarin Red S staining. The expression of osteogenesis markers including ALP, osteocalcin (OCN), osterix (OSX), and runt-related transcription factor 2 (RUNX2) was detected via reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting. The effects of heraclenin on the RhoA/ROCK pathway were estimated through western blotting. Y-27632, the ROCK inhibitor, was used to confirm the role of the RhoA/ROCK pathway in heraclenin-mediated osteogenic differentiation of BMSCs.

RESULTS

Heraclenin (5-80 μM) was non-toxic on human BMSCs. Heraclenin treatment (5-20 μM) dose-dependently enhanced ALP activity and calcium deposition. Furthermore, heraclenin promoted ALP, OCN, OSX, and RUNX2 mRNA and protein expression. Mechanically, heraclenin treatment increased RhoA and ROCK1 mRNA expression, stimulated the translocation of ROCK from the cytosolic to the membrane fraction, and elevated the protein levels of phosphorylated cofilin (p-cofilin) and active RhoA. Additionally, treatment with Y-27632 overturned the promotion of heraclenin on ALP activity, calcium deposition, the expression of osteogenesis markers, and the RhoA/ROCK signaling pathway.

CONCLUSION

Heraclenin facilitates the osteogenic differentiation of human BMSCs through the activation of the RhoA/ROCK pathway.

Bone and Extracellular Signal-Related Kinase 5 (ERK5)

Bones are vital for anchoring muscles, tendons, and ligaments, serving as a fundamental element of the human skeletal structure. However, our understanding of bone development mechanisms and the maintenance of bone homeostasis is still limited. Extracellular signal-related kinase 5 (ERK5), a recently identified member of the mitogen-activated protein kinase (MAPK) family, plays a critical role in the pathogenesis and progression of various diseases, especially neoplasms. Recent studies have highlighted ERK5's significant role in both bone development and bone-associated pathologies. This review offers a detailed examination of the latest research on ERK5 in different tissues and diseases, with a particular focus on its implications for bone health. It also examines therapeutic strategies and future research avenues targeting ERK5.

A novel mechanism of Vildagliptin in regulating bone metabolism and mitigating osteoporosis

Osteoporosis has become a global social problem with the tendency toward the aging population. The challenge in managing osteoporosis is to develop new anti-osteoporosis drugs that target bone anabolism. The purpose of this study was to uncover the novel mechanism of Vildagliptin on bone metabolism. We revealed that Vildagliptin significantly promoted osteogenic differentiation of precursor osteoblasts and bone marrow mesenchymal stem cells (BMSCs). At the same time, it significantly enhanced the polarization of RAW264.7 macrophages to the M2 type and the secretion of osteogenic factors BMP2 and TGF-β1. This was confirmed by the increased osteogenic differentiation observed in the osteoblast-RAW264.7 co-culture system. Moreover, Vildagliptin significantly enhanced the transformation of BMSCs into the osteogenic morphology in the osteoblast-BMSC co-culture system. Finally, Vildagliptin also inhibited osteoclastic differentiation of RAW 264.7 cells. The potential mechanism underlying these effects involved targeting the GAS6/AXL/ERK5 pathway. In the in vivo study, Vildagliptin significantly alleviated postmenopausal osteoporosis in ovariectomized mice. These findings represent the first comprehensive revelation of the regulatory effect of Vildagliptin on bone metabolism. Specifically, Vildagliptin demonstrates the ability to promote bone anabolism and inhibit bone resorption by simultaneously targeting osteoblasts, BMSCs, and osteoclasts. The bone-protective effects of Vildagliptin were further confirmed in a postmenopausal osteoporosis model. The clinical significance of this study lies in laying a theoretical foundation for bone protection therapy in type-2 diabetes patients with compromised bone conditions or postmenopausal osteoporosis.