BMSCs and Osteoblast-Engineered ECM Synergetically Promotes Osteogenesis and Angiogenesis in an Ectopic Bone Formation Model

Preclinical Evaluation of Bioactive Small Intestinal Submucosa-PMMA Bone Cement for Vertebral Augmentation

In vertebroplasty and kyphoplasty, bioinert poly(methyl methacrylate) (PMMA) bone cement is a conventional filler employed for quick stabilization of osteoporotic vertebral compression fractures (OVCFs). However, because of the poor osteointegration, excessive stiffness, and high curing temperature of PMMA, the implant loosens, the adjacent vertebrae refracture, and thermal necrosis of the surrounding tissue occurs frequently. This investigation addressed these issues by incorporating the small intestinal submucosa (SIS) into PMMA (SIS-PMMA). In vitro analyses revealed that this new SIS-PMMA bone cement had improved porous structure, as well as reduced compressive modulus and polymerization temperature compared with the original PMMA. Furthermore, the handling properties of SIS-PMMA bone cement were not significantly different from PMMA. The in vitro effect of PMMA and SIS-PMMA was investigated on MC3T3-E1 cells via the Transwell insert model to mimic the clinical condition or directly by culturing cells on the bone cement samples. The results indicated that SIS addition substantially enhanced the proliferation and osteogenic differentiation of MC3T3-E1 cells. Additionally, the bone cement's biomechanical properties were also assessed in a decalcified goat vertebrae model with a compression fracture, which indicated the SIS-PMMA had markedly increased compressive strength than PMMA. Furthermore, it was proved that the novel bone cement had good biosafety and efficacy based on the International Standards and guidelines. After 12 weeks of implantation, SIS-PMMA indicated significantly more osteointegration and new bone formation ability than PMMA. In addition, vertebral bodies with cement were also extracted for the uniaxial compression test, and it was revealed that compared with the PMMA-implanted vertebrae, the SIS-PMMA-implanted vertebrae had greatly enhanced maximum strength. Overall, these findings indicate the potential of SIS to induce efficient fixation between the modified cement surface and the host bone, thereby providing evidence that the SIS-PMMA bone cement is a promising filler for clinical vertebral augmentation.

Zuo Gui Wan Promotes Osteogenesis via PI3K/AKT Signaling Pathway: Network Pharmacology Analysis and Experimental Validation

OBJECTIVE

Osteogenesis is vitally important for bone defect repair, and Zuo Gui Wan (ZGW) is a classic prescription in traditional Chinese medicine (TCM) for strengthening bones. However, the specific mechanism by which ZGW regulates osteogenesis is still unclear. The current study is based on a network pharmacology analysis to explore the potential mechanism of ZGW in promoting osteogenesis.

METHODS

A network pharmacology analysis followed by experimental validation was applied to explore the potential mechanisms of ZGW in promoting the osteogenesis of bone marrow mesenchymal stem cells (BMSCs).

RESULTS

In total, 487 no-repeat targets corresponding to the bioactive components of ZGW were screened, and 175 target genes in the intersection of ZGW and osteogenesis were obtained. And 28 core target genes were then obtained from a PPI network analysis. A GO functional enrichment analysis showed that the relevant biological processes mainly involve the cellular response to chemical stress, metal ions, and lipopolysaccharide. Additionally, KEGG pathway enrichment analysis revealed that multiple signaling pathways, including the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) signaling pathway, were associated with ZGW-promoted osteogensis. Further experimental validation showed that ZGW could increase alkaline phosphatase (ALP) activity as well as the mRNA and protein levels of ALP, osteocalcin (OCN), and runt related transcription factor 2 (Runx 2). What's more, Western blot analysis results showed that ZGW significantly increased the protein levels of p-PI3K and p-AKT, and the increases of these protein levels significantly receded after the addition of the PI3K inhibitor LY294002. Finally, the upregulated osteogenic-related indicators were also suppressed by the addition of LY294002.

CONCLUSION

ZGW promotes the osteogenesis of BMSCs via PI3K/AKT signaling pathway.

Galangin mitigates glucocorticoid-induced osteoporosis by activating autophagy of BMSCs via triggering the PKA/CREB signaling pathway

Glucocorticoid-induced osteoporosis (GIOP), one of the most common and serious adverse effects associated with glucocorticoid administration, manifests as decreased bone formation and increased bone resorption, eventually culminating in bone loss. Galangin (GAL) is a flavonoid extracted from the medicinal herbal galangal that possesses a variety of pharmacological activities and can inhibit osteoclastogenesis. However, the effects of GAL on GIOP remain unclear. Our study aims to explore the effects of GAL on GIOP in mice and the underlying mechanism. Our results show that GAL markedly mitigates the severity of dexamethasone (Dex)-induced osteoporosis in mice and potentiates osteogenic differentiation in mouse bone marrow-derived mesenchymal stem cells (BMSCs). Furthermore, GAL also significantly counteracts Dex-mediated suppression of osteogenic differentiation and autophagy in human BMSCs. GAL augments PKA/CREB-mediated autophagic flux in BMSCs and the bones of osteoporotic mice. GAL-mediated osteogenic differentiation in Dex-treated BMSCs is significantly decreased by the PKA inhibitor H89 and autophagy inhibitor 3-methyladenine. Collectively, our data indicate that GAL can ameliorate GIOP, partly by augmenting the mineralization of BMSCs by potentiating PKA/CREB-mediated autophagic flux, highlighting its potential therapeutic use in treating glucocorticoid-related osteoporosis.

Leukemia Inhibitory Factor Facilitates Self-Renewal and Differentiation and Attenuates Oxidative Stress of BMSCs by Activating PI3K/AKT Signaling

Objective. Transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) remains a hopeful therapeutic approach for bone defect reconstruction. Herein, we investigated the effects and mechanisms of leukemia inhibitory factor (LIF) in the function and viability of hypoxic BMSCs as well as bone defect repair. Methods. The effects of LIF on apoptosis (flow cytometry, TUNEL staining), mitochondrial activity (JC-1 staining), proliferation (colony formation, EdU staining), and differentiation (CD105, CD90, and CD29 via flow sorting) were examined in hypoxic BMSCs. LIF, LIFR, gp130, Keap1, Nrf2, antioxidant enzymes (SOD1, catalase, GPx-3), bone-specific matrix proteins (ALP, BSP, OCN), PI3K, and Akt were detected via immunoblotting or immunofluorescent staining. BMSCs combined with biphasic calcium phosphate scaffolds were implanted into calvarial bone defect mice, and the therapeutic effect of LIF on bone defect was investigated. Results. Hypoxic BMSCs had increased apoptosis and oxidative stress and reduced mitochondrial activity. Additionally, LIF, LIFR, and gp130 were upregulated and PI3K/Akt activity was depressed in hypoxic BMSCs. Upregulated LIF alleviated apoptosis and oxidative stress and heightened mitochondrial activity and PI3K/Akt signaling in hypoxic BMSCs. Additionally, LIF overexpression promoted self-renewal and osteogenic differentiation of BMSCs with hypoxic condition. Mechanically, LIF facilitated self-renewal and differentiation as well as attenuated oxidative stress of BMSCs through enhancing PI3K/AKT signaling activity. Implantation of LIF-overexpressed BMSC-loaded BCP scaffolds promoted osteogenesis as well as alleviated oxidative stress and apoptosis through PI3K/Akt signaling. Conclusion. Our findings demonstrate that LIF facilitates self-renewal and differentiation and attenuates oxidative stress of BMSCs by PI3K/AKT signaling.

Advances of Stimulus-Responsive Hydrogels for Bone Defects Repair in Tissue Engineering

Bone defects, as one of the most urgent problems in the orthopedic clinic, have attracted much attention from the biomedical community and society. Hydrogels have been widely used in the biomedical field for tissue engineering research because of their excellent hydrophilicity, biocompatibility, and degradability. Stimulus-responsive hydrogels, as a new type of smart biomaterial, have more advantages in sensing external physical (light, temperature, pressure, electric field, magnetic field, etc.), chemical (pH, redox reaction, ions, etc.), biochemical (glucose, enzymes, etc.) and other different stimuli. They can respond to stimuli such as the characteristics of the 3D shape and solid-liquid phase state, and exhibit special properties (injection ability, self-repair, shape memory, etc.), thus becoming an ideal material to provide cell adhesion, proliferation, and differentiation, and achieve precise bone defect repair. This review is focused on the classification, design concepts, and research progress of stimulus-responsive hydrogels based on different types of external environmental stimuli, aiming at introducing new ideas and methods for repairing complex bone defects.