Prospective Review of Mesenchymal Stem Cells Differentiation into Osteoblasts

The Myofibroblast Fate of Therapeutic Mesenchymal Stromal Cells: Regeneration, Repair, or Despair?

Mesenchymal stromal cells (MSCs) can be isolated from various tissues of healthy or patient donors to be retransplanted in cell therapies. Because the number of MSCs obtained from biopsies is typically too low for direct clinical application, MSC expansion in cell culture is required. However, ex vivo amplification often reduces the desired MSC regenerative potential and enhances undesired traits, such as activation into fibrogenic myofibroblasts. Transiently activated myofibroblasts restore tissue integrity after organ injury by producing and contracting extracellular matrix into scar tissue. In contrast, persistent myofibroblasts cause excessive scarring-called fibrosis-that destroys organ function. In this review, we focus on the relevance and molecular mechanisms of myofibroblast activation upon contact with stiff cell culture plastic or recipient scar tissue, such as hypertrophic scars of large skin burns. We discuss cell mechanoperception mechanisms such as integrins and stretch-activated channels, mechanotransduction through the contractile actin cytoskeleton, and conversion of mechanical signals into transcriptional programs via mechanosensitive co-transcription factors, such as YAP, TAZ, and MRTF. We further elaborate how prolonged mechanical stress can create persistent myofibroblast memory by direct mechanotransduction to the nucleus that can evoke lasting epigenetic modifications at the DNA level, such as histone methylation and acetylation. We conclude by projecting how cell culture mechanics can be modulated to generate MSCs, which epigenetically protected against myofibroblast activation and transport desired regeneration potential to the recipient tissue environment in clinical therapies.

KLF9 regulates osteogenic differentiation of mesenchymal stem cells

Osteoporosis is a progressive skeletal disease which is characterized by reduced bone mass and degradation of bone microstructure. Mesenchymal stem cells (MSCs) have the potential to inhibit osteoporosis since they are multipotent stem cells that can differentiate into multiple types of cells including osteoblasts. Hence the mechanism of osteogenic differentiation of MSCs deserves comprehensive study. Here we report that KLF9 is a novel regulator in osteogenic differentiation of MSCs. We observed that depletion of KLF9 can largely compromise the osteogenic differentiation ability of MSCs. In addition, we revealed that inhibition of the PI3K-Akt pathway could also affect osteogenic differentiation since KLF9 depletion inhibits PI3K expression. Finally, we discovered that KLF9 expression can be induced by dexamethasone which is an essential component in osteogenic induction medium. Taken together, our study provides new insights into the regulatory role of KLF9 in osteogenic differentiation of MSCs.

Non-coding RNA in exosomes: Regulating bone metastasis of lung cancer and its clinical application prospect

Lung cancer is a highly prevalent malignancy with poor prognosis and rapid progression. It most frequently metastasizes to the bone, where it can pose a severe threat to the patient's survival. Once metastasized, the disease is often incurable and can result in severe complications such as hypercalcemia, bone pain, fractures, spinal cord compression, and subsequent paralysis. Exosomes are bilayer vesicle nanoparticles secreted by most of the extracellular vesicles, which can be found in almost all organisms and play an essential role in intercellular communication. Through their ability to regulate related bone cells, exosomes carry bioactive molecules, including proteins, lipids, and non-coding RNAs (ncRNAs), that can be extremely important in bone remodeling. Studies have been conducted on the role play by proteins, lncRNA, and microRNA-all ncRNAs-carried by exosomes in the bone metastases of lung cancer. In this review, the latest progress of the regulatory mechanism of ncRNAs carried by exosomes in lung cancer bone metastasis has been reviewed. The clinical use of exosomes as a promising biomarker, drug transporter, and therapeutic target was highlighted to offer a novel diagnostic and treatment approach for patients with lung cancer bone metastases.

Enhancement of Local Osseointegration and Implant Stability of Titanium Implant in Osteoporotic Rats by Biomimetic Multilayered Structures Containing Catalpol

This study examined the surface modification of titanium (Ti) implants to enhance early-stage osseointegration, which reduced the failure rate of internal fixation in osteoporotic fractures that inherently decrease in bone mass and strength. We employed a layer-by-layer electroassembly technique to deposit catalpol-containing hyaluronic acid/chitosan multilayers onto the surface of Ti implants. To evaluate the in vitro osteoinductive effects of catalpol-coated Ti implants, the robust osteoblast differentiation capacity of the murine preosteoblast cell line, MC3T3-E1, was employed. Furthermore, the performance of these implants was evaluated in vivo through femoral intramedullary implantation in Sprague-Dawley rats. The engineered implant effectively regulated catalpol release, promoting increased bone formation during the initial stages of implantation. The in vitro findings demonstrated that catalpol-coated Ti surfaces boosted ALP activity, cell proliferation as measured by CCK-8, and osteogenic protein expression via WB analysis, surpassing the uncoated Ti group (P < 0.05). In vivo micro-computed tomography (CT) and histological analyses revealed that catalpol-coated Ti significantly facilitated the formation and remodeling of new bone in osteoporotic rats at 14 days post-implantation. This study outlines a comprehensive and straightforward methodology for the fabrication of biofunctional Ti implants to address osteoporosis.

Stem Cells and Acellular Preparations in Bone Regeneration/Fracture Healing: Current Therapies and Future Directions

Bone/fracture healing is a complex process with different steps and four basic tissue layers being affected: cortical bone, periosteum, fascial tissue surrounding the fracture, and bone marrow. Stem cells and their derivatives, including embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells, hematopoietic stem cells, skeletal stem cells, and multipotent stem cells, can function to artificially introduce highly regenerative cells into decrepit biological tissues and augment the healing process at the tissue level. Stem cells are molecularly and functionally indistinguishable from standard human tissues. The widespread appeal of stem cell therapy lies in its potential benefits as a therapeutic technology that, if harnessed, can be applied in clinical settings. This review aims to establish the molecular pathophysiology of bone healing and the current stem cell interventions that disrupt or augment the bone healing process and, finally, considers the future direction/therapeutic options related to stem cells and bone healing.

Osteoporosis: interferon-gamma-mediated bone remodeling in osteoimmunology

As the world population ages, osteoporosis, the most common disease of bone metabolism, affects more than 200 million people worldwide. The etiology is an imbalance in bone remodeling process resulting in more significant bone resorption than bone remodeling. With the advent of the osteoimmunology field, the immune system's role in skeletal pathologies is gradually being discovered. The cytokine interferon-gamma (IFN-γ), a member of the interferon family, is an important factor in the etiology and treatment of osteoporosis because it mediates bone remodeling. This review starts with bone remodeling process and includes the cellular and key signaling pathways of bone remodeling. The effects of IFN-γ on osteoblasts, osteoclasts, and bone mass are discussed separately, while the overall effects of IFN-γ on primary and secondary osteoporosis are summarized. The net effect of IFN-γ on bone appears to be highly dependent on the environment, dose, concentration, and stage of cellular differentiation. This review focuses on the mechanisms of bone remodeling and bone immunology, with a comprehensive discussion of the relationship between IFN-γ and osteoporosis. Finding the paradoxical balance of IFN-γ in bone immunology and exploring the potential of its clinical application provide new ideas for the clinical treatment of osteoporosis and drug development.

mir-150-5p inhibits the osteogenic differentiation of bone marrow-derived mesenchymal stem cells by targeting irisin to regulate the p38/MAPK signaling pathway

PURPOSE

To study the effect of miR-150-5p on the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs), and further explore the relationship between its regulatory mechanism and irisin.

METHODS

We isolated mouse BMSCs, and induced osteogenic differentiation by osteogenic induction medium. Using qPCR to detect the expression of osteogenic differentiation-related genes, western blot to detect the expression of osteogenic differentiation-related proteins, and luciferase reporter system to verify that FNDC5 is the target of miR-150-5p. Irisin intraperitoneal injection to treat osteoporosis in mice constructed by subcutaneous injection of dexamethasone.

RESULTS

Up-regulation of miR-150-5p inhibited the proliferation of BMSCs, and decreased the content of osteocalcin, ALP activity, calcium deposition, the expression of osteogenic differentiation genes (Runx2, OSX, OCN, OPN, ALP and BMP2) and protein (BMP2, OCN, and Runx2). And down-regulation of miR-150-5p plays the opposite role of up-regulation of miR-150-5p on osteogenic differentiation of BMSCs. Results of luciferase reporter gene assay showed that FNDC5 gene was the target gene of miR-150-5p, and miR-150-5p inhibited the expression of FNDC5 in mouse BMSCs. The expression of osteogenic differentiation genes and protein, the content of osteocalcin, ALP activity and calcium deposition in BMSCs co-overexpressed by miR-150-5p and FNDC5 was significantly higher than that of miR-150-5p overexpressed alone. In addition, the overexpression of FNDC5 reversed the blocked of p38/MAPK pathway by the overexpression of miR-150-5p in BMSCs. Irisin, a protein encoded by FNDC5 gene, improved symptoms in osteoporosis mice through intraperitoneal injection, while the inhibitor of p38/MAPK pathway weakened this function of irisin.

CONCLUSION

miR-150-5p inhibits the osteogenic differentiation of BMSCs by targeting irisin to regulate the/p38/MAPK signaling pathway, and miR-150-5p/irisin/p38 pathway is a potential target for treating osteoporosis.

Freeze casting of hydroxyapatite-titania composites for bone substitutes

Hydroxyapatite (HA) is commonly used as a bone substitute material, but it lacks mechanical strength when compared to native bone tissues. To improve the efficacy of HA as a bone substitute by improving the mechanical strength and cell growth attributes, porous composite scaffolds of HA and titania (HA-TiO2 ) were fabricated through a freeze-casting process. Three different compositions by weight percent, 25-75 HA-TiO2 , 50-50 HA-TiO2 , and 75-25 HA-TiO2 , were custom-made for testing. After sintering at 1250°C, these composite scaffolds exhibited improved mechanical properties compared to porous HA scaffolds. Substrate mixing was observed, which helped reduce crystal size and introduced new phases such as β-TCP and CaTiO3 , which also led to improved mechanical properties. The composition of 50-50 HA-TiO2 had the highest ultimate compressive strength of 3.12 ± 0.36 MPa and elastic modulus 63.29 ± 28.75 MPa. Human osteoblast cell proliferation assay also increased on all three different compositions when compared to porous HA at 14 days. These results highlight the potential of freeze casting composites for the fabrication of bone substitutes, which provide enhanced mechanical strength and biocompatibility while maintaining porosity.

Uncovering hidden treasures: Mapping morphological changes in the differentiation of human mesenchymal stem cells to osteoblasts using deep learning

Deep Learning (DL) is becoming an increasingly popular technology being employed in life sciences research due to its ability to perform complex and time-consuming tasks with significantly greater speed, accuracy, and reproducibility than human researchers - allowing them to dedicate their time to more complex tasks. One potential application of DL is to analyze cell images taken by microscopes. Quantitative analysis of cell microscopy images remain a challenge - with manual cell characterization requiring excessive amounts of time and effort. DL can address these issues, by quickly extracting such data and enabling rigorous, empirical analysis of images. Here, DL is used to quantitively analyze images of Mesenchymal Stem Cells (MSCs) differentiating into Osteoblasts (OBs), tracking morphological changes throughout this transition. The changes in morphology throughout the differentiation protocol provide evidence for a distinct path of morphological transformations that the cells undergo in their transition, with changes in perimeter being observable before changes in eceentricity. Subsequent differentiation experiments can be quantitatively compared with our dataset to concretely evaluate how different conditions affect differentiation and this paper can also be used as a guide for researchers on how to utilize DL workflows in their own labs.

Evaluate the effects of low-intensity pulsed ultrasound on dental implant osseointegration under type II diabetes

Objective: The objective of this study is to assess the impact of low-intensity pulsed ultrasound (LIPUS) therapy on the peri-implant osteogenesis in a Type II diabetes mellitus (T2DM) rat model. Methods: A total of twenty male Sprague-Dawley (SD) rats were randomly allocated into four groups: Control group, T2DM group, Control-LIPUS group, and T2DM-LIPUS group. Implants were placed at the rats' bilateral maxillary first molar sites. The LIPUS treatment was carried out on the rats in Control-LIPUS group and T2DM-LIPUS group, immediately after the placement of the implants, over three consecutive weeks. Three weeks after implantation, the rats' maxillae were extracted for micro-CT, removal torque value (RTV), and histologic analysis. Results: Micro-CT analysis showed that T2DM rats experienced more bone loss around implant cervical margins compared with the non-T2DM rats, while the LIPUS treated T2DM rats showed similar bone heights to the non-T2DM rats. Bone-implant contact ratio (BIC) were lower in T2DM rats but significantly improved in the LIPUS treated T2DM rats. Bone formation parameters including bone volume fraction (BV/TV), trabecular thickness (Tb.Th), bone mineral density (BMD) and RTV were all positively influenced by LIPUS treatment. Histological staining further confirmed LIPUS's positive effects on peri-implant new bone formation in T2DM rats. Conclusion: As an effective and safe treatment in promoting osteogenesis, LIPUS has a great potential for T2DM patients to attain improved peri-implant osteogenesis. To confirm its clinical efficacy and to explore the underlying mechanism, further prospective cohort studies or randomized controlled trials are needed in the future.

Photobiomodulation therapy's impact on angiogenesis and osteogenesis in orthodontic tooth movement: in vitro and in vivo study

BACKGROUND

This study explores the effectiveness of Photobiomodulation Therapy (PBMT) in enhancing orthodontic tooth movement (OTM), osteogenesis, and angiogenesis through a comprehensive series of in vitro and in vivo investigations. The in vitro experiments involved co-culturing MC3T3-E1 and HUVEC cells to assess PBMT's impact on cell proliferation, osteogenesis, angiogenesis, and associated gene expression. Simultaneously, an in vivo experiment utilized an OTM rat model subjected to laser irradiation at specific energy densities.

METHODS

In vitro experiments involved co-culturing MC3T3-E1 and HUVEC cells treated with PBMT, enabling a comprehensive assessment of cell proliferation, osteogenesis, angiogenesis, and gene expression. In vivo, an OTM rat model was subjected to laser irradiation at specified energy densities. Statistical analyses were performed to evaluate the significance of observed differences.

RESULTS

The results revealed a significant increase in blood vessel formation and new bone generation within the PBMT-treated group compared to the control group. In vitro, PBMT demonstrated positive effects on cell proliferation, osteogenesis, angiogenesis, and gene expression in the co-culture model. In vivo, laser irradiation at specific energy densities significantly enhanced OTM, angiogenesis, and osteogenesis.

CONCLUSIONS

This study highlights the substantial potential of PBMT in improving post-orthodontic bone quality. The observed enhancements in angiogenesis and osteogenesis suggest a pivotal role for PBMT in optimizing treatment outcomes in orthodontic practices. The findings position PBMT as a promising therapeutic intervention that could be seamlessly integrated into orthodontic protocols, offering a novel dimension to enhance overall treatment efficacy. Beyond the laboratory, these results suggest practical significance for PBMT in clinical scenarios, emphasizing its potential to contribute to the advancement of orthodontic treatments. Further exploration of PBMT in orthodontic practices is warranted to unlock its full therapeutic potential.

Mesenchymal stem cells and cancer-associated fibroblasts as a therapeutic strategy for breast cancer

Breast cancer is the most common type of cancer and the leading cause of death among women. Recent evidence suggests that mesenchymal stromal/stem cells and cancer-associated fibroblasts (CAFs) have an essential role in cancer progression, invasion and therapy resistance. Therefore, they are considered as highly promising future therapeutic targets against breast cancer. The intrinsic tumour tropism and immunomodulatory capacities of mesenchymal stromal/stem cells are of special relevance for developing mesenchymal stromal/stem cells-based anti-tumour therapies that suppress primary tumour growth and metastasis. In addition, the utilization of therapies that target the stromal components of the tumour microenvironment in combination with standard drugs is an innovative tool that could improve patients' response to therapies and their survival. In this review, we discuss the currently available information regarding the possible use of mesenchymal stromal/stem cells-derived anti-tumour therapies, as well as the utilization of therapies that target CAFs in breast cancer microenvironment. Finally, these data can serve as a guide map for future research in this field, ultimately aiding the effective transition of these results into the clinic. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Osteoblast Biospecific Extraction Conjugated with HPLC Analysis for Screening Bone Regeneration Active Components from Moutan Cortex

INTRODUCTION

The function of promoting bone regeneration of Moutan Cortex (MC), a traditional Chinese medicine, has been widely known but, the effective components of MC in promoting osteoblast-mediated bone regeneration were still unclear.

OBJECTIVE

The method of osteoblast membrane bio-specific extraction conjugated with HPLC analysis was established to screen bone regeneration active components from MC.

METHODS

The fingerprints, washing eluate and desorption eluate of MC extract were analyzed by the established HPLC-DAD method. The established MC3T3-E1 cells membrane chromatography method was used for the bio-specific extraction of MC. The isolated compounds were identified by MS spectrometry. The effects and possible mechanisms of the isolated compounds were evaluated by molecular docking, ALP activity, cell viability by MTT Assay and proteins expression by Western Blot Analysis.

RESULTS

The active compound responsible for bone regeneration from MC was isolated using the established method of osteoblast membrane bio-specific extraction conjugated with HPLC analysis, and it was identified as 1,2,3,4,6-penta-O-β-galloyl-D-glucose (PGG) by MS spectrometry. It was further demonstrated through molecular docking that PGG could fit well into the functional ALP, BMP2, and Samd1 binding pocket. The proliferation of osteoblasts was promoted, the level of ALP was increased, and the protein expression of BMP2 and Smad1 was increased as shown by further pharmacological verification.

CONCLUSION

It was concluded that PGG, the bone regeneration active compound from MC, could stimulate the proliferation of osteoblasts to promote osteoblast differentiation, and its mechanism might be related to the BMP/Smad1 pathway.

BMP-2 promotes fracture healing by facilitating osteoblast differentiation and bone defect osteogenesis

OBJECTIVE

To investigate the role of bone morphogenetic protein-2 (BMP-2) in promoting fracture healing in animal models.

METHODS

Mouse models with muscle bag heterotopic osteogenesis (HO) were divided into a HO control group (not implanted with 250 μg rhBMP-2 bone repairing material), and a HO observation group (implanted with 250 μg rhBMP-2 bone repairing material); while rat models with bone defect (BD) were divided into a BD control group (not implanted with 250 μg rhBMP-2 bone repairing material) and a BD observation group (implanted with 250 μg rhBMP-2 bone repairing material). At 4 weeks after HO establishment, the new bone formation at the operation site was observed through visual inspections and X-ray scanning. The content of serum alkaline phosphatase (ALP) was detected by automatic biochemical analyzer. The formation of new bone at the operative sites was observed by Hematoxylin and eosin staining and Masson staining. At 0, 2, 4 and 8 weeks after operation, the growth of the defect area and its surrounding callus were observed by X-ray scanning. At 4 and 8 weeks after bone defect establishment in the mouse models, the histological changes and osteogenesis of the bone defect site were observed.

RESULTS

The heterotopic osteogenesis experiment showed that at 4 weeks after operation, the mass at the muscle bag in the HO observation group became larger in contrast to the HO control group. X-ray scanning showed that there was obvious irregular bone shadow at the back muscle bag of mice from the HO observation group. The content of serum ALP in the HO observation group was significantly higher than that in the HO control group (all P<0.05). The muscle pocket in the HO observation group showed higher ectopic osteogenic activity comparing with the HO control group. Histological staining showed that bone tissue structure was visible in the newly regenerated bone, forming bone trabeculae and bone marrow tissue. Under the microscope, a large number of osteoblasts arranged neatly in a cubic shape presented at the edge of the new bone, and there were bone lacunae formed, and the bone tissue was in a relatively mature stage. In the rat bone defect models, X-ray scanning showed that the high-density development area was further increased. There was a large amount of callus formation in the bone defect area of the BD observation group, while the BD control group still had no high-density development. At 8 weeks after operation, the high-density development area decreased, indicating that there was partial absorption of callus, while there was still no high-density development in the BD control group. The callus of the bone defect area in the BD observation group was reduced and the defect area was gradually repaired, while the bone defect in the BD control group was still obvious and the bone repair was not completed.

CONCLUSIONS

BMP-2 could promote osteoblast differentiation and bone defect osteogenesis in vivo. Thus, it is worthy of clinical application.

Microarray illustrates enhanced mechanistic action towards osteogenesis for magnesium aluminate spinel ceramic-based polyphasic composite scaffold with mesenchymal stem cells and bone morphogenetic protein 2

Spinel (magnesium aluminate MgAl2 O4 ) ceramic-based polyphasic composite scaffold has been recently reported for craniofacial bone tissue engineering. Improving the osteogenic effects of such composite scaffolds with bone morphogenetic proteins (BMP2) is an intensely researched area. This study investigated the gene interactions of this scaffold with BMP2 and mesenchymal stem cells (MSCs). Human bone marrow MSCs were cultured in 3 groups: Group 1-Control (BMSCs), Group 2-BMSC with BMP2, and Group 3-BMSC with scaffold and BMP2. After RNA isolation, gene expression analysis was done by microarray. Differentially expressed genes (DEGs) (-1.0 > fold changes>1 and p value <.05) were studied for their function and gene ontologies using Database for Annotation, Visualization and Integrated Discovery (DAVID). They were further studied by protein-protein interaction network analysis using STRING and MCODE Cytoscape plugin database. Group 3 showed up regulation of 3222 genes against 2158 of Group 2. Group 3 had five annotation clusters with enrichment scores from 2.08 to 3.93. Group 2 had only one cluster. Group 3 showed activation of all major osteogenic pathways: TGF, BMP2, WNT, SMAD, and Notch gene signaling with effects of calcium and magnesium released from the scaffold. Downstream effect of all these caused significant activation of RUNX2, the key transcriptional regulator of osteogenesis in Group 3. STRING and MCODE Cytoscape plugin demonstrated the interactions. The enhanced MSC differentiation for osteogenesis with the addition of BMP2 to the polyphasic composite scaffold proposed promising clinical applications for bone tissue engineering.

The Effect of the Hip Flexion Angle in Osteonecrosis of the Femoral Head Based on China-Japan Friendship Hospital Classification - A Finite Element Study

OBJECTIVE

The alteration in the mechanical environment of the necrotic area is the primary cause of the collapse observed in osteonecrosis of the femoral head (ONFH). This study aims to evaluate the biomechanical implications of the China-Japan Friendship Hospital (CJFH) classification system and hip flexion angles on the necrotic area in ONFH using finite element analysis (FEA). The goal is to provide valuable guidance for hip preservation treatments and serve as a reference for clinical diagnosis and therapeutic interventions.

METHODS

Hip tomography CT scan data from a healthy volunteer was used to create a 3D model of the left hip. The model was preprocessed and imported into Solidworks 2018, based on the CJFH classification. Material parameters and boundary conditions were applied to each fractal model in ANSYS 21.0. Von Mises stresses were calculated, and maximum deformation values were obtained to evaluate the biomechanical effects of the load on the necrotic area and post-necrotic femur, as well as assess each fractal model's collapse risk.

RESULTS

(1) At the same hip flexion angle, maximum deformation followed this order: M Type < C Type < L Type. The L3 type necrotic area experienced the most significant deformation at 0, 60, and 110° angles (1.121, 1.7913, and 1.8239 mm respectively). (2) Under the same CJFH classification, maximum deformation values increased with hip flexion angle (0 < 60 < 110°), suggesting a higher risk of collapse at larger angles. (3) Von Mises stress results showed that the maximum stress was not located in the necrotic area but near the inner and outer edge of the femoral neck, indicating decreased stiffness and strength of the subchondral bone after osteonecrosis.

CONCLUSION

The study found that femoral head collapse risk was higher when the necrotic area was located in the lateral column under the same stress load and flexion angle. Mechanical properties of the necrotic area changed, resulting in decreased bone strength and stiffness. Large-angle hip flexion is more likely to cause excessive deformation of the necrotic area; thus, ONFH patients should reduce or avoid large-angle hip flexion during weight-bearing training in rehabilitation activities.

Toxoplasma gondii excretory/secretory proteins promotes osteogenic differentiation of bone marrow mesenchymal stem cells via aerobic glycolysis mediated by Wnt/β‑catenin signaling pathway

Toxoplasma gondii excretory/secretory proteins (TgESPs) are a group of proteins secreted by the parasite and have an important role in the interaction between the host and Toxoplasma gondii (T. gondii). They can participate in various biological processes in different cells and regulate cellular energy metabolism. However, the effect of TgESPs on energy metabolism and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) has remained elusive. In the present study, TgESPs were extracted from the T. gondii RH strain and used to treat BMSCs to observe the effect of TgESPs on energy metabolism and osteogenic differentiation of BMSCs and to explore the molecular mechanisms involved. The osteogenic differentiation and energy metabolism of BMSCs were evaluated using Alizarin Red S staining, qRT-PCR, western blot, immunofluorescence and Seahorse extracellular flux assays. The results indicated that TgESPs activated the Wnt/β‑catenin signaling pathway to enhance glycolysis and lactate production in BMSCs, and promoted cell mineralization and expression of osteogenic markers. In conclusion, the present study uncovered the potential mechanism by which TgESPs regulate BMSCs, which will provide a theoretical reference for the study of the function of TgESPs in the future.

Guizhi Shaoyao Zhimu granules attenuate bone destruction in mice with collagen-induced arthritis by promoting mitophagy of osteoclast precursors to inhibit osteoclastogenesis

BACKGROUND

Guizhi Shaoyao Zhimu decoction, a traditional Chinese medicine formula used empirically for the treatment of rheumatoid arthritis (RA), has been shown to alleviate bone destruction in rats with collagen-induced arthritis (CIA).

PURPOSE

The aim of this study is to characterize the effects of Guizhi Shaoyao Zhimu granules (GSZGs) on bone destruction in RA and the underlying mechanism.

STUDY DESIGN

A CIA arthritis model using DBA/1 mice. The animals were divided into a normal group; CIA model group; low, medium, and high-dose GSZG groups (3, 6, and 9 g/kg/day); and a methotrexate group (1.14 mg/kg/w). In vitro, a cytokine induced osteoclastogenesis model was established.

METHODS

After 28 days of treatment, the paw volume was measured, bone destruction was examined by micro-CT, and the generation of osteoclasts in bone tissue was evaluated via tartrate-resistant acid phosphatase (TRAP) staining. Furthermore, the inhibitory effect and underlying mechanism of action of GSZG on RANKL-induced osteoclastogenesis were investigated in vitro.

RESULTS

The in vivo analyses demonstrated that the paw volume and degree of bone erosion of mice in the medium- and high-dose GSZG groups were significantly decreased compared to the CIA model group. In addition, GSZG treatment suppressed the excessive generation of osteoclasts in the bone tissue of CIA mice. In vitro, GSZG inhibited RANKL-induced osteoclastogenesis and osteoclast-mediated bone resorption. Specifically, it only inhibited the generation of osteoclast precursors (OCPs); it had no significant effect on the fusion of OCPs or maturation of osteoclasts. Finally, we showed that the inhibitory effect of GSZG on osteoclastogenesis was related to the promotion of PTEN-induced kinase protein 1 (PINK1)/Parkin pathway-mediated mitophagy of osteoclast precursors, which was verified using a PINK1 knockdown small interfering RNA in OCPs.

CONCLUSION

These findings indicate that GSZG is a candidate for the treatment of bone destruction in RA and provide a more detailed elucidation of the mechanism of GSZG anti-RA bone erosion, i.e., inhibition of the ROS/NF-κB axis through the PINK1/Parkin-mediated mitochondrial autophagic pathway to inhibit osteoclast precursor production, compared to the published literature.

Angiogenesis after ischemic stroke

Owing to its high disability and mortality rates, stroke has been the second leading cause of death worldwide. Since the pathological mechanisms of stroke are not fully understood, there are few clinical treatment strategies available with an exception of tissue plasminogen activator (tPA), the only FDA-approved drug for the treatment of ischemic stroke. Angiogenesis is an important protective mechanism that promotes neural regeneration and functional recovery during the pathophysiological process of stroke. Thus, inducing angiogenesis in the peri-infarct area could effectively improve hemodynamics, and promote vascular remodeling and recovery of neurovascular function after ischemic stroke. In this review, we summarize the cellular and molecular mechanisms affecting angiogenesis after cerebral ischemia registered in PubMed, and provide pro-angiogenic strategies for exploring the treatment of ischemic stroke, including endothelial progenitor cells, mesenchymal stem cells, growth factors, cytokines, non-coding RNAs, etc.

Senescent mesenchymal stem/stromal cells in pre-metastatic bone marrow of untreated advanced breast cancer patients

Breast cancer is the predominant form of carcinoma among women worldwide, with 70% of advanced patients developing bone metastases, with a high mortality rate. In this sense, the bone marrow (BM) mesenchymal stem/stromal cells (MSCs) are critical for BM/bone homeostasis, and failures in their functionality, transform the BM into a pre-metastatic niche (PMN). We previously found that BM-MSCs from advanced breast cancer patients (BCPs, infiltrative ductal carcinoma, stage III-B) have an abnormal profile. This work aims to study some of the metabolic and molecular mechanisms underlying MSCs shift from a normal to an abnormal profile in this group of patients. A comparative analysis was undertaken, which included self-renewal capacity, morphology, proliferation capacity, cell cycle, reactive oxygen species (ROS) levels, and senescence-associated β‑galactosidase (SA‑β‑gal) staining of BM-derived MSCs isolated from 14 BCPs and 9 healthy volunteers (HVs). Additionally, the expression and activity of the telomerase subunit TERT, as well as telomere length, were measured. Expression levels of pluripotency, osteogenic, and osteoclastogenic genes (OCT-4, SOX-2, M-CAM, RUNX-2, BMP-2, CCL-2, M-CSF, and IL-6) were also determined. The results showed that MSCs from BCPs had reduced ,self-renewal and proliferation capacity. These cells also exhibited inhibited cell cycle progression and phenotypic changes, such as an enlarged and flattened appearance. Additionally, there was an increase in ROS and senescence levels and a decrease in the functional capacity of TERT to preserve telomere length. We also found an increase in pro-inflammatory/pro-osteoclastogenic gene expression and a decrease in pluripotency gene expression. We conclude that these changes could be responsible for the abnormal functional profile that MSCs show in this group of patients.

Ubiquitin-specific proteases: Vital regulatory molecules in bone and bone-related diseases

Stabilization of bone structure and function involves multiple cell-to-cell and molecular interactions, in which the regulatory functions of post-translational modifications such as ubiquitination and deubiquitination shouldn't be underestimated. As the largest family of deubiquitinating enzymes, the ubiquitin-specific proteases (USPs) participate in the development of bone homeostasis and bone-related diseases through multiple classical osteogenic and osteolytic signaling pathways, such as BMP/TGF-β pathway, NF-κB/p65 pathway, EGFR-MAPK pathway and Wnt/β-catenin pathway. Meanwhile, USPs may also broadly regulate regulate hormone expression level, cell proliferation and differentiation, and may further influence bone homeostasis from gene fusion and nuclear translocation of transcription factors. The number of patients with bone-related diseases is currently enormous, making exploration of their pathogenesis and targeted therapy a hot topic. Pathological increases in the levels of inflammatory mediators such as IL-1β and TNF-α lead to inflammatory bone diseases such as osteoarthritis, rheumatoid arthritis and periodontitis. While impaired body metabolism greatly increases the probability of osteoporosis. Abnormal physiological activity of bone-associated cells results in a variety of bone tumors. The regulatory role of USPs in bone-related disease has received particular attention from academics in recent studies. In this review, we focuse on the roles and mechanisms of USPs in bone homeostasis and bone-related diseases, with the expectation of informing targeted therapies in the clinic.

Thermodynamic 2D Silicene for Sequential and Multistage Bone Regeneration

Bone healing is a multistage process involving the recruitment of cells, revascularization, and osteogenic differentiation, all of which are modulated in the temporal sequence to maximize cascade bone regeneration. However, insufficient osteoblast cells, poor blood supply, and limited bone induction at the site of critical‐sized bone defect broadly impede bone repair. 2D SiO2‐silicene@2,2′‐,azobis(2‐[2‐imidazolin‐2‐yl] propane) (SNSs@AIPH) with inherent thermodynamic property and osteoinductive activity is therefore designed and engineered for sequentially efficient bone repair. By means of controllable NIR‐II irradiation, the integrated SNSs@AIPH stimulates the generation of appropriate intracellular reactive oxygen species, which accelerates early bone marrow mesenchymal stem cells (BMSCs) proliferation and angiogenesis remarkably. Importantly, as silicon‐based 2D nanoparticles, the engineered SNSs@AIPH with high biocompatibility features distinct bioactivity to significantly promote BMSCs osteogenesis differentiation by activating TGFβ and BMP pathways. In a rat cranial defect model, SNSs@AIPH‐NIR‐II leads to a comparable increase of BMSCs proliferation and local vascularization at an early stage, followed by significant osteogenic differentiation, synergically resulting in a highly effective bone repair. Collectively, the fascinating characteristics and exceptional bone repair efficiency of NIR‐II‐mediated SNSs@AIPH allow it to be a promising bionic‐oriented strategy for bone regeneration, broadening a new perspective in the application of cell‐instructive biomaterials in bone tissue engineering.

Thermodynamic 2D Silicene for Sequential and Multistage Bone Regeneration

Bone healing is a multistage process involving the recruitment of cells, revascularization, and osteogenic differentiation, all of which are modulated in the temporal sequence to maximize cascade bone regeneration. However, insufficient osteoblast cells, poor blood supply, and limited bone induction at the site of critical-sized bone defect broadly impede bone repair. 2D SiO2 -silicene@2,2'-,azobis(2-[2-imidazolin-2-yl] propane) (SNSs@AIPH) with inherent thermodynamic property and osteoinductive activity is therefore designed and engineered for sequentially efficient bone repair. By means of controllable NIR-II irradiation, the integrated SNSs@AIPH stimulates the generation of appropriate intracellular reactive oxygen species, which accelerates early bone marrow mesenchymal stem cells (BMSCs) proliferation and angiogenesis remarkably. Importantly, as silicon-based 2D nanoparticles, the engineered SNSs@AIPH with high biocompatibility features distinct bioactivity to significantly promote BMSCs osteogenesis differentiation by activating TGFβ and BMP pathways. In a rat cranial defect model, SNSs@AIPH-NIR-II leads to a comparable increase of BMSCs proliferation and local vascularization at an early stage, followed by significant osteogenic differentiation, synergically resulting in a highly effective bone repair. Collectively, the fascinating characteristics and exceptional bone repair efficiency of NIR-II-mediated SNSs@AIPH allow it to be a promising bionic-oriented strategy for bone regeneration, broadening a new perspective in the application of cell-instructive biomaterials in bone tissue engineering.

Downregulation of the RNA-binding protein PUM2 facilitates MSC-driven bone regeneration and prevents OVX-induced bone loss

BACKGROUND

Although mRNA dysregulation can induce changes in mesenchymal stem cell (MSC) homeostasis, the mechanisms by which post-transcriptional regulation influences MSC differentiation potential remain understudied. PUMILIO2 (PUM2) represses translation by binding target mRNAs in a sequence-specific manner.

METHODS

In vitro osteogenic differentiation assays were conducted using human bone marrow-derived MSCs. Alkaline phosphatase and alizarin red S staining were used to evaluate the osteogenic potential of MSCs. A rat xenograft model featuring a calvarial defect to examine effects of MSC-driven bone regeneration. RNA-immunoprecipitation (RNA-IP) assay was used to determine the interaction between PUM2 protein and Distal-Less Homeobox 5 (DLX5) mRNA. Ovariectomized (OVX) mice were employed to evaluate the effect of gene therapy for postmenopausal osteoporosis.

RESULTS

Here, we elucidated the molecular mechanism of PUM2 in MSC osteogenesis and evaluated the applicability of PUM2 knockdown (KD) as a potential cell-based or gene therapy. PUM2 level was downregulated during MSC osteogenic differentiation, and PUM2 KD enhanced MSC osteogenic potential. Following PUM2 KD, MSCs were transplanted onto calvarial defects in 12-week-old rats; after 8 weeks, transplanted MSCs promoted bone regeneration. PUM2 KD upregulated the expression of DLX5 mRNA and protein and the reporter activity of its 3'-untranslated region. RNA-IP revealed direct binding of PUM2 to DLX5 mRNA. We then evaluated the potential of adeno-associated virus serotype 9 (AAV9)-siPum2 as a gene therapy for osteoporosis in OVX mice.

CONCLUSION

Our findings suggest a novel role for PUM2 in MSC osteogenesis and highlight the potential of PUM2 KD-MSCs in bone regeneration. Additionally, we showed that AAV9-siPum2 is a potential gene therapy for osteoporosis.

Synergistic Effect of QNZ, an Inhibitor of NF-κB Signaling, and Bone Morphogenetic Protein 2 on Osteogenic Differentiation in Mesenchymal Stem Cells through Fibroblast-Induced Yes-Associated Protein Activation

Biomaterials carrying recombinant human bone morphogenetic protein 2 (BMP2) have been developed to enhance bone regeneration in the treatment of bone defects. However, various reports have shown that in the bone repair microenvironment, fibroblasts can inhibit BMP2-induced osteogenic differentiation in mesenchymal stem cells (MSCs). Thus, factors that can target fibroblasts and improve BMP2-mediated osteogenesis should be explored. In this project, we focused on whether or not an inhibitor of the NF-κB signaling pathway, QNZ (EVP4593), could play a synergistic role with BMP2 in osteogenesis by regulating the activity of fibroblasts. The roles of QNZ in regulating the proliferation and migration of fibroblasts were examined. In addition, the effect of QNZ combined with BMP2 on the osteogenic differentiation of MSCs was evaluated both in vitro and in vivo. Furthermore, the detailed mechanisms by which QNZ improved BMP2-mediated osteogenesis through the modulation of fibroblasts were analyzed and revealed. Interestingly, we found that QNZ inhibited the proliferation and migration of fibroblasts. Thus, QNZ could relieve the inhibitory effects of fibroblasts on the homing and osteogenic differentiation of mesenchymal stem cells. Furthermore, biomaterials carrying both QNZ and BMP2 showed better osteoinductivity than did those carrying BMP2 alone both in vitro and in vivo. It was found that the mechanism of QNZ involved reactivating YAP activity in mesenchymal stem cells, which was inhibited by fibroblasts. Taken together, our results suggest that QNZ may be a candidate factor for assisting BMP2 in inducing osteogenesis. The combined application of QNZ and BMP2 in biomaterials may be promising for the treatment of bone defects in the future.

Progress of Wnt Signaling Pathway in Osteoporosis

Osteoporosis, one of the serious health diseases, involves bone mass loss, bone density diminishing, and degeneration of bone microstructure, which is accompanied by a tendency toward bone fragility and a predisposition to fracture. More than 200 million people worldwide suffer from osteoporosis, and the cost of treating osteoporotic fractures is expected to reach at least $25 billion by 2025. The generation and development of osteoporosis are regulated by genetic factors and regulatory factors such as TGF-β, BMP, and FGF through multiple pathways, including the Wnt signaling pathway, the Notch signaling pathway, and the MAPK signaling pathway. Among them, the Wnt signaling pathway is one of the most important pathways. It is not only involved in bone development and metabolism but also in the differentiation and proliferation of chondrocytes, mesenchymal stem cells, osteoclasts, and osteoblasts. Dkk-1 and SOST are Wnt inhibitory proteins that can inhibit the activation of the canonical Wnt signaling pathway and block the proliferation and differentiation of osteoblasts. Therefore, they may serve as potential targets for the treatment of osteoporosis. In this review, we analyzed the mechanisms of Wnt proteins, β-catenin, and signaling molecules in the process of signal transduction and summarized the relationship between the Wnt signaling pathway and bone-related cells. We hope to attract attention to the role of the Wnt signaling pathway in osteoporosis and offer new perspectives and approaches to making a diagnosis and giving treatment for osteoporosis.

Regenerative Medicine and Rehabilitation Therapy in the Canine

Regenerative medicine is used in the canine to optimize tissue healing and treat osteoarthritis and soft tissue injuries. Rehabilitation therapy is also often implemented in the treatment and management of musculoskeletal conditions in the canine. Initial experimental studies have shown that regenerative medicine and rehabilitation therapy may work safely and synergistically to enhance tissue healing. Although additional study is required to define optional rehabilitation therapy protocols after regenerative medicine therapy in the canine, certain fundamental principles of rehabilitation therapy still apply to patients treated with regenerative medicine.

Combined computational analysis and cytology show limited depth osteogenic effect on bone defects in negative pressure wound therapy

Background: The treatment of bone defects remains a clinical challenge. The effect of negative pressure wound therapy (NPWT) on osteogenesis in bone defects has been recognized; however, bone marrow fluid dynamics under negative pressure (NP) remain unknown. In this study, we aimed to examine the marrow fluid mechanics within trabeculae by computational fluid dynamics (CFD), and to verify osteogenic gene expression, osteogenic differentiation to investigate the osteogenic depth under NP. Methods: The human femoral head is scanned using micro-CT to segment the volume of interest (VOI) trabeculae. The VOI trabeculae CFD model simulating the bone marrow cavity is developed by combining the Hypermesh and ANSYS software. The effect of trabecular anisotropy is investigated, and bone regeneration effects are simulated under NP scales of -80, -120, -160, and -200 mmHg. The working distance (WD) is proposed to describe the suction depth of the NP. Finally, gene sequence analysis, cytological experiments including bone mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation are conducted after the BMSCs are cultured under the same NP scale. Results: The pressure, shear stress on trabeculae, and marrow fluid velocity decrease exponentially with an increase in WD. The hydromechanics of fluid at any WD inside the marrow cavity can be theoretically quantified. The NP scale significantly affects the fluid properties, especially those fluid close to the NP source; however, the effect of the NP scale become marginal as WD deepens. Anisotropy of trabecular structure coupled with the anisotropic hydrodynamic behavior of bone marrow; An NP of -120 mmHg demonstrates the majority of bone formation-related genes, as well as the most effective proliferation and osteogenic differentiation of BMSCs compared to the other NP scales. Conclusion: An NP of -120 mmHg may have the optimal activated ability to promote osteogenesis, but the effective WD may be limited to a certain depth. These findings help improve the understanding of fluid mechanisms behind NPWT in treating bone defects.

Regulation of bone health through physical exercise: Mechanisms and types

Osteoporosis, characterized by bone mineral density reduction, bone mass loss, increased bone fragility, and propensity to fractures, is a common disease in older individuals and one of the most serious health problems worldwide. The imbalance between osteoblasts and osteoclasts results in the predominance of bone resorption and decreased bone formation. In recent years, it has been found that regular and proper exercise not only helps prevent the occurrence of osteoporosis but also adds benefits to osteoporosis therapy; accordingly, bone homeostasis is closely associated with mechanical stress and the intricate crosstalk between osteoblasts and osteoclasts. In this review, we summarize the mechanisms of exercise on osteoporosis and provide new proposals for the prevention and treatment of osteoporosis.

Comparative Efficiency of Gene-Activated Matrices Based on Chitosan Hydrogel and PRP Impregnated with BMP2 Polyplexes for Bone Regeneration

Gene therapy is one of the most promising approaches in regenerative medicine. Gene-activated matrices provide stable gene expression and the production of osteogenic proteins in situ to stimulate osteogenesis and bone repair. In this study, we developed new gene-activated matrices based on polylactide granules (PLA) impregnated with BMP2 polyplexes and included in chitosan hydrogel or PRP-based fibrin hydrogel. The matrices showed high biocompatibility both in vitro with mesenchymal stem cells and in vivo when implanted intramuscularly in rats. The use of porous PLA granules allowed the inclusion of a high concentration of polyplexes, and the introduction of the granules into hydrogel provided the gradual release of the plasmid constructs. All gene-activated matrices showed transfecting ability and ensured long-term gene expression and the production of target proteins in vitro. At the same time, the achieved concentration of BMP-2 was sufficient to induce osteogenic differentiation of MSCs. When implanted into critical-size calvarial defects in rats, all matrices with BMP2 polyplexes led to new bone formation. The most significant effect on osteoinduction was observed for the PLA/PRP matrices. Thus, the developed gene-activated matrices were shown to be safe and effective osteoplastic materials. PLA granules and PRP-based fibrin hydrogel containing BMP2 polyplexes were shown to be the most promising for future applications in bone regeneration.

Exosomes in bone remodeling and breast cancer bone metastasis

Exosomes are endosome-derived microvesicles that carry cell-specific biological cargo, such as proteins, lipids, and noncoding RNAs (ncRNAs). They play a key role in bone remodeling by enabling the maintenance of a balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Recent evidence indicates that exosomes disrupt bone remodeling that occurs during breast cancer (BC) progression. The bone is a preferred site for BC metastasis owing to its abundant osseous reserves. In this review, we aimed to highlight the roles of exosomes derived from bone cells and breast tumor in bone remodeling and BC bone metastasis (BCBM). We also briefly outline the mechanisms of action of ncRNAs and proteins carried by exosomes secreted by bone and BCBM. Furthermore, this review highlights the potential of utilizing exosomes as biomarkers or delivery vehicles for the diagnosis and treatment of BCBM.

Ubiquitin modification in osteogenic differentiation and bone formation: From mechanisms to clinical significance

The ubiquitin-proteasome system is an important pathway for mediating posttranslational modification and protein homeostasis and exerts a wide range of functions in diverse biological processes, including stem cell differentiation, DNA repair, and cell cycle regulation. Many studies have shown that ubiquitination modification plays a critical role in regulating the osteogenic differentiation of stem cells and bone formation through various mechanisms. This review summarizes current progress on the effects and mechanisms of ubiquitin modification on transcription factors and signaling pathways involved in osteogenic differentiation. Moreover, the review highlights the latest advances in the clinical application of drugs in bone tissue engineering. A thorough understanding of ubiquitin modifications may provide promising therapeutic targets for stem cell-based bone tissue engineering.

Effectiveness and Mechanisms of Low-Intensity Pulsed Ultrasound on Osseointegration of Dental Implants and Biological Functions of Bone Marrow Mesenchymal Stem Cells

Dental implant restoration is the preferred choice for patients with dentition defects or edentulous patients, and obtaining stable osseointegration is the determining factor for successful implant healing. The risk of implant failure during the healing stage is still an urgent problem in clinical practice due to differences in bone quality at different implant sites and the impact of some systemic diseases on bone tissue metabolism. Low-intensity pulsed ultrasound (LIPUS) is a noninvasive physical intervention method widely recognized in the treatment of bone fracture and joint damage repair. Moreover, many studies indicated that LIPUS could effectively promote the osseointegration of dental implants and improve the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). This review is aimed at investigating the research progress on the use of LIPUS in dental implant medicine from three aspects: (1) discuss the promoting effects of LIPUS on osseointegration and peri-implant bone regeneration, (2) summarize the effects and associated mechanisms of LIPUS on the biological functions of BMSCs, and (3) introduce the application and prospects of LIPUS in the clinical work of dental implantation. Although many challenges need to be overcome in the future, LIPUS is bound to be an efficient and convenient therapeutic method to improve the dental implantation success rate and expand clinical implant indications.

Negative pressure wound therapy improves bone regeneration by promoting osteogenic differentiation via the AMPK-ULK1-autophagy axis

Deficient bone regeneration causes bone defects or nonunion in a substantial proportion of trauma patients that urges for novel therapies. To develop a reliable therapy, we investigated the effect of negative pressure wound therapy (NPWT) on bone regeneration in vivo in a rat calvarial defect model. Negative pressure (NP) treatment in vitro was mimicked to test its effect on osteoblast differentiation in rat mesenchymal stem cells (MSCs) and MC3T3-E1 cells. Transcriptomic analyses, pharmaceutical interventions, and shRNA knockdowns were conducted to explore the underlying mechanism and their clinical relevance was investigated in samples from patients with nonunion. The potential application of a combined therapy of MSCs in hydrogels with negative pressure was tested in the rat critical-size calvarial defect model. We found that NPWT promoted bone regeneration in vivo and NP treatment induced osteoblast differentiation in vitro. NP induced osteogenesis via activating macroautophagy/autophagy by AMPK-ULK1 signaling that was impaired in clinical samples from patients with nonunion. More importantly, the combined therapy involving MSCs in hydrogels with negative pressure significantly improved bone regeneration in rat critical-size calvarial defect model. Thus, our study identifies a novel AMPK-ULK1-autophagy axis by which negative pressure promotes osteoblast differentiation of MSCs and bone regeneration. NPWT treatment can potentially be adopted for therapy of bone defects.Abbreviations: ADP, adenosine diphosphate; AICAR/Aic, acadesine; ALP, alkaline phosphatase; ALPL, alkaline phosphatase, biomineralization associated; AMP, adenosine monophosphate; AMPK, AMP-activated protein kinase; ARS, alizarin red S staining; ATG7, autophagy related 7; ATP, adenosine triphosphate; BA1, bafilomycin A₁; BGLAP/OCN, bone gamma-carboxyglutamate protein; BL, BL-918; BS, bone surface; BS/TV, bone surface per tissue volume; BV/TV, bone volume per tissue volume; C.C, compound C; CCN1, cellular communication network factor 1; COL1A1, collagen type I alpha 1 chain; COL4A3, collagen type IV alpha 3 chain; COL4A4, collagen type IV alpha 4 chain; COL18A1, collagen type XVIII alpha 1 chain; CQ, chloroquine; GelMA, gelatin methacryloyl hydrogel; GO, Gene Ontology; GSEA, gene set enrichment analysis; HIF1A, hypoxia inducible factor 1 subunit alpha; HPLC, high-performance liquid chromatography; ITGAM/CD11B, integrin subunit alpha M; ITGAX/CD11C, integrin subunit alpha X; ITGB1/CdD9, integrin subunit beta 1; KEGG, Kyoto Encyclopedia of Genes and Genomes; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; micro-CT, microcomputed tomography; MSCs, mesenchymal stem cells; MTOR, mechanistic target of rapamycin kinase; NP, negative pressure; NPWT, negative pressure wound therapy; PRKAA1/AMPKα1, protein kinase AMP-activated catalytic subunit alpha 1; PRKAA2, protein kinase AMP-activated catalytic subunit alpha 2; PTPRC/CD45, protein tyrosine phosphatase receptor type C; ROS, reactive oxygen species; RUNX2, RUNX family transcription factor 2; SBI, SBI-0206965; SPP1/OPN, secreted phosphoprotein 1; THY1/CD90, Thy-1 cell surface antigen; SQSTM1, sequestosome 1; TGFB3, transforming growth factor beta 3; ULK1/Atg1, unc-51 like autophagy activating kinase 1.

Meta-Analysis of Mechanism of Influence of CRY2 on the Differentiation of Mouse Osteoblast through the Regulation of Wnt/Β-Catenin Signaling Pathway

Noncoding RNAs were discovered to control a variety of developmental mechanisms, including osteogenesis. According to emerging evidence, cryptochrome circadian-regulating (CRY) proteins have emerged as essential controllers of osteoblast differentiation. The linked processes, on the other hand, are still unknown. The specific process that underpins osteoblast differentiation and proliferation is yet unknown. This research gives a meta-analysis of CRY2's impact on mouse osteoblast differentiation via the control of the WNT/β-catenin signaling pathways. Western blot and quantitative real-time PCR were used to identify Cry2 expression levels, components in the osteoblast-associated signaling pathway, and osteoblast transcription markers. The osteogenic condition was measured utilizing alkaline phosphatase (ALP) and alizarin red (AR) staining, whereas cell growth rates were measured using CCK8 assays. An ectopic bone formation experiment was used to determine the osteogenic potential of osteoblasts. Cry2 stimulates the osteogenic development of mouse osteoblasts through canonical Wnt/β-catenin signaling, according to the findings.

Hu’po Anshen Decoction Accelerated Fracture-Healing in a Rat Model of Traumatic Brain Injury Through Activation of PI3K/AKT Pathway

Hu’po Anshen decoction (HPASD) is a traditional Chinese medicine formula comprising five herbal medicines for the treatment of concussion and fracture healing, but its pharmacological mechanism is still unclear. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC/Q-TOF MS) was used to analyze the main active components of HPASD. Rats were randomly assigned to fracture group, fracture combined with traumatic brain injury (TBI) group (FBI) and FBI combined with HPASD treatment group (FBIH). Rats in the FBIH group were given oral doses of HPASD (2.4 g/kg, 4.8 g/kg and 9.6 g/kg) for 14 or 21 consecutive days. The fracture callus formation and fracture sites were determined by radiographic analysis and micron-scale computed tomography (micro-CT) analysis. Hematoxylin and eosin (H&E) staining and a three-point bending test were applied to assess histological lesions and biomechanical properties, respectively. The levels of cytokines-/protein-related to bone formation and differentiation as well as PI3K/AKT pathway-related proteins were determined by Enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription-polymerase chain reaction (qRT-PCR), or western blot assays, respectively. UPLC-Q/TOF-MS-based serum metabolomic analysis was also performed to investigate the therapeutic effects of HPASD in the treatment of FBI. UPLC/Q-TOF MS analysis showed the chemical components in HPASD, including flavonoids, amino acids, saponins, and phenylpropanoid constituents, etc. HPASD dose-dependently promoted callus formation, increased bone density, improved mechanical parameters and morphological scores, and facilitated the expressions of VEGF, PDGF, bFGF, VEGFA, CoL1A1, RUNX2, BMP2, and Aggrecan, inhibited the expression of MMP13, and activated PI3K/AKT pathway. Metabolomics analysis revealed abnormalities of malate-aspartate shuttle and glucose-alanine. HPASD accelerates fracture healing by promoting bone formation and regulating the malate-aspartate shuttle and glucose-alanine cycle, which might be associated with the activation of the PI3K/AKT pathway.

Nanoclay-reinforced HA/alginate scaffolds as cell carriers and SDF-1 delivery-platforms for bone tissue engineering

Bone tissue engineering has come on the scene to overcome the difficulties of the current treatment strategies. By combining biomaterials, active agents and growth factors, cells and nanomaterials, tissue engineering makes it possible to create new structures that enhance bone regeneration. Herein, hyaluronic acid and alginate were used to create biologically active hydrogels, and montmorillonite nanoclay was used to reinforce and stabilize them. The developed scaffolds were found to be biocompatible and osteogenic with mMSCs in vitro, especially those reinforced with the nanoclay, and allowed mineralization even in the absence of differentiation media. Moreover, an in vivo investigation was performed to establish the potential of the hydrogels to mend bone and act as cell-carriers and delivery platforms for SDF-1. Scaffolds embedded with SDF-1 exhibited the highest percentages of bone regeneration as well as of angiogenesis, which confirms the suitability of the scaffolds for bone. Although there are a number of obstacles to triumph over, these bioengineered structures showed potential as future bone regeneration treatments.

Manufacturing artificial bone allografts: a perspective

Bone grafts have traditionally come from four sources: the patients' own tissue (autograft), tissue from a living or cadaveric human donor (allograft), animal donors (xenograft) and synthetic artificial biomaterials (ceramics, cement, polymers, and metal). However, all of these have advantages and drawbacks. The most commercially successful bone grafts so far are allografts, which hold 57% of the current bone graft market; however, disease transmission and scarcity are still significant drawbacks limiting their use. Tissue-engineered grafts have great potential, in which human stem cells and synthetical biomaterials are combined to produce bone-like tissue in vitro, but this is yet to be approved for widespread clinical practice. It is hypothesised that artificial bone allografts can be mass-manufactured to replace conventional bone allografts through refined bone tissue engineering prior to decellularisation. This review article aims to review current literature on (1) conventional bone allograft preparation; (2) bone tissue engineering including the use of synthetic biomaterials as bone graft substitute scaffolds, combined with osteogenic stem cells in vitro; (3) potential artificial allograft manufacturing processes, including mass production of engineered bone tissue, osteogenic enhancement, decellularisation, sterilisation and safety assurance for regulatory approval. From these assessments, a practical route map for mass production of artificial allografts for clinical use is proposed.

Periodic Heat Stress Licenses EMSC Differentiation into Osteoblasts via YAP Signaling Pathway Activation

Background

The repair and regeneration of large bone defects represent highly challenging tasks in bone tissue engineering. Although recent studies have shown that osteogenesis is stimulated by periodic heat stress, the thermal regulation of osteogenic differentiation in ectomesenchymal stem cells (EMSCs) is not well studied.

Methods and Results

In this study, the direct effects of periodic heat stress on the differentiation of EMSCs into osteoblasts were investigated. EMSCs derived from rat nasal respiratory mucosa were seeded onto culture plates, followed by 1 h of heat stress at 41°C every 7 days during osteogenic differentiation. Based on the results of the present study, periodic heating increases alkaline phosphatase (ALP) activity, upregulates osteogenic-related proteins, and promotes EMSC mineralization. In particular, increased YAP nuclear translocation and YAP knockdown inhibited osteogenic differentiation induced by heat stress. Furthermore, the expression and activity of transglutaminase 2 (TG2) were significantly increased after YAP nuclear translocation.

Conclusion

Together, these results indicate that YAP plays a key role in regulating cellular proteostasis under stressful cellular conditions by modulating the TG2 response.

Characterization of Biological Properties of Dental Pulp Stem Cells Grown on an Electrospun Poly(l-lactide-co-caprolactone) Scaffold

Poly(l-lactide-co-caprolactone) (PLCL) electrospun scaffolds with seeded stem cells have drawn great interest in tissue engineering. This study investigated the biological behavior of human dental pulp stem cells (hDPSCs) grown on a hydrolytically-modified PLCL nanofiber scaffold. The hDPSCs were seeded on PLCL, and their biological features such as viability, proliferation, adhesion, population doubling time, the immunophenotype of hDPSCs and osteogenic differentiation capacity were evaluated on scaffolds. The results showed that the PLCL scaffold significantly supported hDPSC viability/proliferation. The hDPSCs adhesion rate and spreading onto PLCL increased with time of culture. hDPSCs were able to migrate inside the PLCL electrospun scaffold after 7 days of seeding. No differences in morphology and immunophenotype of hDPSCs grown on PLCL and in flasks were observed. The mRNA levels of bone-related genes and their proteins were significantly higher in hDPSCs after osteogenic differentiation on PLCL compared with undifferentiated hDPSCs on PLCL. These results showed that the mechanical properties of a modified PLCL mat provide an appropriate environment that supports hDPSCs attachment, proliferation, migration and their osteogenic differentiation on the PLCL scaffold. The good PLCL biocompatibility with dental pulp stem cells indicates that this mat may be applied in designing a bioactive hDPSCs/PLCL construct for bone tissue engineering.

Enhancing fracture repair: cell-based approaches

Fracture repair is based both on the macrolevel modulation of fracture fragments and the subsequent cellular activity. Surgeons have also long recognized other influences on cellular behavior: the effect of the fracture or subsequent surgery on the available pool of cells present locally in the periosteum, the interrelated effects of fragment displacement, and construct stiffness on healing potential, patient pathophysiology and systemic disease conditions (such as diabetes), and external regulators of the skeletal repair (such as smoking or effect of medications). A wide variety of approaches have been applied to enhancing fracture repair by manipulation of cellular biology. Many of these approaches reflect our growing understanding of the cellular physiology that underlies skeletal regeneration. This review focuses on approaches to manipulating cell lineages, influencing paracrine and autocrine cell signaling, or applying other strategies to influence cell surface receptors and subsequent behavior. Scientists continue to evolve new approaches to pharmacologically enhancing the fracture repair process.

Recent Advances in Enhancement Strategies for Osteogenic Differentiation of Mesenchymal Stem Cells in Bone Tissue Engineering

Although bone is an organ that displays potential for self-healing after damage, bone regeneration does not occur properly in some cases, and it is still a challenge to treat large bone defects. The development of bone tissue engineering provides a new approach to the treatment of bone defects. Among various cell types, mesenchymal stem cells (MSCs) represent one of the most promising seed cells in bone tissue engineering due to their functions of osteogenic differentiation, immunomodulation, and secretion of cytokines. Regulation of osteogenic differentiation of MSCs has become an area of extensive research over the past few years. This review provides an overview of recent research progress on enhancement strategies for MSC osteogenesis, including improvement in methods of cell origin selection, culture conditions, biophysical stimulation, crosstalk with macrophages and endothelial cells, and scaffolds. This is favorable for further understanding MSC osteogenesis and the development of MSC-based bone tissue engineering.

Cell Culture in Microfluidic Droplets

Cell manipulation in droplets has emerged as one of the great successes of microfluidic technologies, with the development of single-cell screening. However, the droplet format has also served to go beyond single-cell studies, namely by considering the interactions between different cells or between cells and their physical or chemical environment. These studies pose specific challenges linked to the need for long-term culture of adherent cells or the diverse types of measurements associated with complex biological phenomena. Here we review the emergence of droplet microfluidic methods for culturing cells and studying their interactions. We begin by characterizing the quantitative aspects that determine the ability to encapsulate cells, transport molecules, and provide sufficient nutrients within the droplets. This is followed by an evaluation of the biological constraints such as the control of the biochemical environment and promoting the anchorage of adherent cells. This first part ends with a description of measurement methods that have been developed. The second part of the manuscript focuses on applications of these technologies for cancer studies, immunology, and stem cells while paying special attention to the biological relevance of the cellular assays and providing guidelines on improving this relevance.

Linagliptin in Combination With Metformin Ameliorates Diabetic Osteoporosis Through Modulating BMP-2 and Sclerostin in the High-Fat Diet Fed C57BL/6 Mice

BACKGROUND

Diabetic osteoporosis is a poorly managed serious skeletal complication, characterized by high fracture risk, increased bone resorption, reduced bone formation, and disrupted bone architecture. There is a need to investigate drugs that can improve bone health along with managing glycemic control. DPP-4 inhibitors and metformin have proven benefits in improving bone health. Here, we investigated the effects of linagliptin, a DPP inhibitor, and metformin alone and in combination to treat diabetic osteoporosis in high-fat-fed mice.

METHODS

C57BL/6 mice were kept on the high-fat diet (HFD) for 22 weeks to induce diabetic osteoporosis. Linagliptin (10mg/Kg), metformin (150mg/Kg), and their combination were orally administered to the diabetic mice from the 18^th-22^nd week. Femur and tibial bone microarchitecture together with bone mineral density (BMD) were evaluated using µCT and histopathological changes were assessed. Further, bone turnover biomarkers namely bone morphogenetic protein-2 (BMP-2), sclerostin, tartrate-resistant acid phosphatase (TRAP), osteocalcin, alkaline phosphatase (ALP), calcium, and pro-inflammatory cytokines were assessed. Additionally, metabolic parameters including body weight, fasting blood glucose (FBG), glucose & insulin tolerance, lipids profile, and leptin were measured.

RESULTS

HFD feeding resulted in impaired bone microarchitecture, reduced BMD, distorted bone histology, and altered bone turnover biomarkers as indicated by the significant reduction in bone ALP, BMP-2, osteocalcin, and an increase in sclerostin, TRAP, and serum calcium. Interestingly, treatment with linagliptin and its combination with metformin significantly reverted the impaired bone architecture, BMD, and positively modulated bone turnover biomarkers, while metformin alone did not exhibit any significant improvement. Further, HFD induced diabetes and metabolic abnormalities (including an increase in body weight, FBG, impaired glucose and insulin tolerance, leptin, triglycerides, cholesterol), and pro-inflammatory cytokines (TNF-alpha and IL-1β) were successfully reversed by treatment with linagliptin, metformin, and their combination.

CONCLUSION

Linagliptin and its combination with metformin successfully ameliorated diabetic osteoporosis in HFD-fed mice possibly through modulation of BMP-2 and sclerostin. The study provides the first evidence for the possible use of linagliptin and metformin combination for managing diabetic osteoporosis.

Enhanced bone formation in rat critical-size tibia defect by a novel quercetin-containing alpha-calcium sulphate hemihydrate/nano-hydroxyapatite composite

We developed an innovative method to include quercetin into alpha-calcium sulphate hemihydrate/nano-hydroxyapatite (α-CSH/n-HA), to prepare a novel quercetin-containing α-CSH/n-HA composite (Q-α-CSH/n-HA). The physicochemical properties, and ability of Q-α-CSH/n-HA to promote cell proliferation, migration, and osteogenic differentiation of bone marrow stem cells (BMSCs) in vitro were examined. Further, the potential of Q-α-CSH/n-HA to promote bone defect repair was studied using a Sprague-Dawley rat model of critical tibial defects. Imaging was conducted by radiography and micro-CT, and bone defect repairs were observed by histopathological staining. Addition of quercetin clearly increased the porosity of the degraded composite, which elevated the cell proliferation rate, migration ability, osteogenesis differentiation, and mineralisation of BMSCs. Further, quercetin-containing composite increased the expression levels of OSX, RUNX2, OCN, ALP, BMP-2, OPN, BSP, SMAD2, and TGF-β in BMSCs, while it downregulated TNF-α. X-ray and micro-CT imaging showed that the quercetin-containing composite significantly enhanced bone defect repair and new bone in formation. Haematoxylin and eosin, Goldner, and Safranin O staining also showed that quercetin significantly increased new bone generation and promoted composite degradation and absorption. Moreover, immunofluorescence assay revealed that quercetin significantly increased the number of RUNX2/OSX/OCN-positive cells. Overall, our data demonstrate that Q-α-CSH/n-HA has excellent biocompatibility, bone conductivity, and osteo-induction performance in vitro and mediates enhanced overall repair effects and bone reconstruction in vivo, indicating that it is a promising artificial bone graft to promote bone regeneration.

Bio-functionalization and in-vitro evaluation of titanium surface with recombinant fibronectin and elastin fragment in human mesenchymal stem cell

Titanium is a biomaterial that meets a number of important requirements, including excellent mechanical and chemical properties, but has low bioactivity. To improve cellular response onto titanium surfaces and hence its osseointegration, the titanium surface was bio-functionalized to mimic an extracellular matrix (ECM)-like microenvironment that positively influences the behavior of stem cells. In this respect, fibronectin and elastin are important components of the ECM that regulate stem cell differentiation by supporting the biological microenvironment. However, each native ECM is unsuitable due to its high production cost and immunogenicity. To overcome these problems, a recombinant chimeric fibronectin type III_9-10 and elastin-like peptide fragments (FN9-10_ELP) was developed herein and applied to the bio-functionalized of the titanium surface. An evaluation of the biological activity and cellular responses with respect to bone regeneration indicated a 4-week sustainability on the FN9-10_ELP functionalized titanium surface without an initial burst effect. In particular, the adhesion and proliferation of human mesenchymal stem cells (hMSCs) was significantly increased on the FN9-10_ELP coated titanium compared to that observed on the non-coated titanium. The FN9-10_ELP coated titanium induced osteogenic differentiation such as the alkaline phosphatase (ALP) activity and mineralization activity. In addition, expressions of osteogenesis-related genes such as a collagen type I (Col I), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), osteocalcin (OCN), bone sialo protein (BSP), and PDZ-binding motif (TAZ) were further increased. Thus, in vitro the FN9-10_ELP functionalization titanium not only sustained bioactivity but also induced osteogenic differentiation of hMSCs to improve bone regeneration.

Polypeptides IGF-1C and P24 synergistically promote osteogenic differentiation of bone marrow mesenchymal stem cells in vitro through the p38 and JNK signaling pathways

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein 2 (BMP-2) both promote osteogenesis of bone marrow mesenchymal stem cells (BMSCs). IGF-1C, the C domain peptide of IGF-1, and P24, a BMP-2-derived peptide, both have similar biological activities as their parent growth factors. This study aimed to investigate the effects and mechanisms of polypeptides IGF-1C and P24 on the osteogenic differentiation of BMSCs.

METHODS

The optimum concentrations of IGF-IC and P24 were explored. The effects of the two polypeptides on BMSC proliferation and osteogenic differentiation were examined using a CCK-8 assay, flow cytometry, alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qPCR, and Western blotting. In addition, specific pathway inhibitors were utilized to explore whether the p38 and JNK pathways were involved in this process.

RESULTS

The optimal concentration of both polypeptides was 50 μg/ml. IGF-1C and P24 synergistically promoted BMSC proliferation, increased ALP activity and calcified nodule formation, upregulated the mRNA and protein levels of Osx, Runx2, Ocn, Opn, and Col1a1, and improved the phosphorylation levels of p38 and JNK proteins. Inhibition of the pathways significantly reduced p38 and JNK activation and blocked Runx2 expression while inhibiting ALP activity and calcified nodule formation.

CONCLUSIONS

These findings suggest that IGF-1C and P24 synergistically promote the osteogenesis of BMSCs through activation of the p38 and JNK signaling pathways.

N2-Polarized Neutrophils Guide Bone Mesenchymal Stem Cell Recruitment and Initiate Bone Regeneration: A Missing Piece of the Bone Regeneration Puzzle

The role of neutrophils in bone regeneration remains elusive. In this study, it is shown that intramuscular implantation of interleukin-8 (IL-8) (commonly recognized as a chemotactic cytokine for neutrophils) at different levels lead to outcomes resembling those of fracture hematoma at various stages. Ectopic endochondral ossification is induced by certain levels of IL-8, during which neutrophils are recruited to the implanted site and are N2-polarized, which then secrete stromal cell-derived factor-1α (SDF-1α) for bone mesenchymal stem cell (BMSC) chemotaxis via the SDF-1/CXCR4 (C-X-C motif chemokine receptor 4) axis and its downstream phosphatidylinositol 3'-kinase (PI3K)/Akt pathway and β-catenin-mediated migration. Neutrophils are pivotal for recruiting and orchestrating innate and adaptive immunocytes, as well as BMSCs at the initial stage of bone healing and regeneration. The results in this study delineate the mechanism of neutrophil-initiated bone regeneration and interaction between neutrophils and BMSCs, and innate and adaptive immunities. This work lays the foundation for research in the fields of bone regenerative therapy and biomaterial development, and might inspire further research into novel therapeutic options.

Dynamics of Renewal of Cell Populations of the Bone Tissue on the Surface of Titanium Implants with Bioactive Coating during Fracture Modeling in Rats

Localization of PCNA, CD44, osteocalcin, Mdm2, p53, and caspase-3 on the surface of implant with calcium phosphate and hydroxyapatite coating was studied by immunocytochemical method in a model of femur fracture in rats. PCNA⁺, Ost⁺, CD44⁺, and Mdm²⁺ cells were found in the periosteum, in the layer of the outer surrounding plates, and in the connective tissue of the Haversian canals. Cell density increased on day 7 after fracture and then decreased by day 30. The number of p53⁺ and CASP3⁺ cells reached a maximum on day 14 (they were predominantly located in the periosteum and bone plates adjacent to it) and decreased by day 30. Calcium phosphate coating stimulated proliferative activity of cells at the early stages of the regeneration phase and apoptotic death at the later stages. Components of coating can be viewed as a positioning clue for differentiation of mesenchymal stromal cells. The effectiveness of reparative osteogenesis is determined by the balance of proliferative and destructive factors at the site of the fracture healing. This process can be optimized with various nanostructured materials with osteoinductive properties, in particular bioresorbable calcium phosphate coatings on titanium implants. However, the influence of these components on the state of cambial cells, their differentiation, and positioning in the repair zone is unknown.