FAK mediates BMP9-induced osteogenic differentiation via Wnt and MAPK signaling pathway in synovial mesenchymal stem cells

Nf2-FAK signaling axis is critical for cranial bone ossification and regeneration

Skeletal mesenchymal stem cells (MSCs) possess self-renewal capacities and play a leading role in the craniofacial system. However, their engagement in controlling cranial bone development and regeneration remains largely unidentified. Herein, we discovered the neurofibromin 2 (Nf2)-encoded regulator Merlin, demonstrating indispensableness in the craniofacial system. Mice lacking Nf2 in MSCs exhibit malformed cranial bones, diminished proliferation, increased apoptosis, and more severe osteogenesis impairment. Mechanically, we substantiate that Nf2 physically interacts with focal adhesion kinase (FAK) to preferentially mediate Erk1/2 and PI3K catalytic p110 subunit/Akt signaling. Meanwhile, Nf2-FAK disturbance in MSCs results in deficient migration, cytoskeletal organization and focal adhesion dynamics, and develops retarded regeneration of cranial bone defects. Collectively, our findings underscore an unrecognized scaffolding role for Nf2-FAK as upstream element in regulating PI3K/Akt and Erk1/2 action in osteoblasts, and illuminate its essentialness in coordinating cell migration, osteogenic lineage development, cranial bone ossification and regeneration.

Multifunctional hydrogel scaffolds based on polysaccharides and polymer matrices promote bone repair: A review

With the advancement of medical technology, the utilization of bioactive materials to promote bone repair has emerged as a significant research area. Hydrogels, as biomaterials, play a crucial role in bone tissue engineering. These hydrogels exhibit high biocompatibility, providing in vivo ecological conditions conducive to cell survival, and offer substantial advantages in facilitating bone repair. Different matrices of hydrogels serve distinct functions. In recent years, numerous researchers have developed a variety of novel hydrogel materials utilizing diverse matrices. These materials not only enhance the osteogenic induction capacity of hydrogels but also improve their efficacy as scaffolds in the treatment of complex bone defects, such as those resulting from trauma, tumor resection, or large bone defects due to infection. This article primarily analyzes the role of hydrogels that utilize polysaccharides and polymers as matrices in bone tissue repair, focusing on the creation of an optimal microenvironment to promote bone regeneration. These investigations deepen the understanding of the mechanisms underlying the action of hydrogels and establish a foundation for future advancements in the biomedical field.

miR-378a-3p Regulates the BMP2-Smad Pathway to Promote Chondrogenic Differentiation of Synovium-Derived Mesenchymal Stem Cells

This study aims to elucidate the role of miR-378a-3p in facilitating the proliferation and differentiation of synovium-derived mesenchymal stem cells (SMSCs) into chondrocytes. The effects of overexpressing miR-378a-3p on SMSCs were investigated through histological analysis, quantitative PCR, and western blotting. Then we identified binding sites of miR-378a-3p with BMP2 through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses and predictions from the RegRNA 2.0 database. Subsequently, BMP2 was confirmed as the target by which miR-378a-3p promotes the chondrogenic differentiation of SMSCs using a luciferase reporter gene assay and an miR-378a-3p RNA interference plasmid. Finally, by constructing a rat model with articular cartilage damage, we detected the reparative effects of miR-378a-3p overexpression on cartilage damage. Additionally, we verified the mechanism by which miR-378a-3p promotes chondrogenic differentiation in SMSCs. MiR-378a-3p enhances the proliferation and differentiation of SMSCs into chondrocytes by modulating the BMP2-Smad signaling pathway, thereby facilitating repair processes for articular cartilage injuries in rats. Notably, knockdown of BMP2 diminished the reparative efficacy of miR-378a-3p on articular cartilage damage. Upregulation of miR-378a-3p promotes chondrogenic differentiation in SMSCs through activation of the BMP2-Smad pathway, positioning it as a potential therapeutic target for osteoarthritis.

Proteomic profile of tissue-derived extracellular vesicles from benign odontogenic lesions

BACKGROUND

Benign odontogenic lesions (BOLs) can cause severe jaw bone defects and compromise the quality of life of patients. Extracellular vesicles (EVs) are well-established and versatile players in mediating pathophysiological events. EVs in the interstitial space (tissue-derived EVs or Ti-EVs) possess higher specificity and sensitivity in disease-related biomarker discovery. However, the role of Ti-EV-loaded proteins in mediating the development of BOLs has remained untapped. Herein, we aim to explore the contribution of Ti-EV-loaded proteins to the development of BOLs.

METHODS

Samples were obtained from 3 with dental follicle, 3 with dentigerous cyst (DC), 7 with odontogenic keratocyst (OKC), and 3 patients with ameloblastoma (AM). Tissue-derived EVs were then extracted, purified, and validated using ultracentrifugation, transmission electron microscopy, and western blotting. Proteins from Ti-EVs were analyzed using LC-ESI tandem mass spectroscopy and differentially expressed proteins were screened, which was then validated by immunohistochemistry and immunofluorescence assays.

RESULTS

The protein profile of Ti-EVs in each group was mapped by LC-MS analysis. The top 10 abundant proteins in BOL-derived Ti-EVs were COL6A3, COL6A1, ALB, HIST1H4A, HBB, ACTB, HIST1H2BD, ANXA2, COL6A2 and FBN1. Additionally, unique proteins in the Ti-EVs from various lesions were identified. Moreover, focal adhesion kinase (FAK) and myeloid differentiation primary response 88 (MyD88) showed higher expressions in Ti-EVs derived from OKC and AM, which were confirmed by immunohistochemistry and immunofluorescence staining.

CONCLUSIONS

Ti-EVs containing FAK and MyD88 might be related to the development of OKC and AM, which can be potential therapeutic targets.

Mechanism and application of feedback loops formed by mechanotransduction and histone modifications

Mechanical stimulation is the key physical factor in cell environment. Mechanotransduction acts as a fundamental regulator of cell behavior, regulating cell proliferation, differentiation, apoptosis, and exhibiting specific signature alterations during the pathological process. As research continues, the role of epigenetic science in mechanotransduction is attracting attention. However, the molecular mechanism of the synergistic effect between mechanotransduction and epigenetics in physiological and pathological processes has not been clarified. We focus on how histone modifications, as important components of epigenetics, are coordinated with multiple signaling pathways to control cell fate and disease progression. Specifically, we propose that histone modifications can form regulatory feedback loops with signaling pathways, that is, histone modifications can not only serve as downstream regulators of signaling pathways for target gene transcription but also provide feedback to regulate signaling pathways. Mechanotransduction and epigenetic changes could be potential markers and therapeutic targets in clinical practice.

Focal adhesion kinase (FAK): its structure, characteristics, and signaling in skeletal system

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and distributes important regulatory functions in skeletal system. Mesenchymal stem cell (MSC) possesses significant migration and differentiation capacity, is an important source of distinctive bone cells production and a prominent bone development pathway. MSC has a wide range of applications in tissue bioengineering and regenerative medicine, and is frequently employed for hematopoietic support, immunological regulation, and defect repair, although current research is insufficient. FAK has been identified to cross-link with many other keys signaling pathways in bone biology and is considered as a fundamental "crossroad" on the signal transduction pathway and a "node" in the signal network to mediate MSC lineage development in skeletal system. In this review, we summarized the structure, characteristics, cellular signaling, and the interactions of FAK with other signaling pathways in the skeletal system. The discovery of FAK and its mediated molecules will lead to a new knowledge of bone development and bone construction as well as considerable potential for therapeutic use in the treatment of bone-related disorders such as osteoporosis, osteoarthritis, and osteosarcoma.

Periplaneta americana extract promotes osteoblast differentiation of human alveolar bone marrow mesenchymal stem cells

OBJECTIVES

This study aims to investigate the effects of Traditional Chinese medicine, Periplaneta americana extract (PAE), on osteoblast differentiation of human alveolar bone marrow-derived mesenchymal stem cells (hABMMSCs).

MATERIALS AND METHODS

Human alveolar bone marrow-derived mesenchymal stem cells were treated with different concentrations of PAE. Cell Counting Kit-8 (CCK-8) assay and transwell migration assay were conducted to evaluate cell proliferation and migration, respectively. Alkaline phosphatase (ALP) staining, ALP activity assay, and Alizarin red S staining were performed to detect osteogenesis in hABMMSCs. In addition, real-time quantitative polymerase chain reaction (RT-qPCR) and western blot (WB) assay were performed to evaluate expression levels of osteogenic markers. Finally, RNA sequencing analysis and WB were carried out to elucidate the underlying mechanism.

RESULTS

A total of 0.1 mg/ml PAE promoted cell proliferation and migration. PAE also increased ALP activity and mineralized nodule formation of hABMMSCs. In addition, PAE upregulated the expression of osteogenesis-related genes (RUNX2, COL1A1, and BGLAP). RNA-sequencing analysis revealed that PAE activated the focal adhesion signaling pathway. Treatment with Defactinib, an inhibitor of FAK, attenuated the effects induced by PAE.

CONCLUSIONS

PAE could enhance osteoblast differentiation of hABMMSCs through focal adhesion signaling pathway, suggesting a therapeutic potential for the alveolar bone defect.

Icariin promotes the proliferation and osteogenic differentiation of bone-derived mesenchymal stem cells in patients with osteoporosis and T2DM by upregulating GLI-1

BACKGROUND

The function of mesenchymal stem cells (MSCs) from patients with osteoporosis (OP) is impaired and worsens in patients with type 2 diabetes mellitus (T2DM). Icariin (ICA) is the major active flavonoid glucoside isolated from traditional Chinese herbal Epimedium pubescens, and confirmed able to improve bone mass of OP patients.

OBJECTIVE

To investigate the effect of ICA on the proliferation and osteogenic differentiation of bone-derived MSCs (BMSCs) from patients with OP and T2DM and uncover the potential mechanism.

METHODS

BMSCs were treated with ICA, and proliferation and osteogenic potency were evaluated using the 2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and detection of osteogenic markers (ALP, RUNX2, SPP1, COL1A1, and mineralized nodules) was performed. RNA sequencing and bioinformatic analysis were performed to identify differentially expressed genes (DEGs) after ICA treatment and screen proliferation- and osteogenic differentiation-related processes. Gene gain and loss were performed to confirm the role of the key candidate gene.

RESULTS

ICA significantly promoted the proliferation and osteogenic differentiation of BMSCs. A total of 173 DEGs were identified after ICA treatment. Six DEGs (GLI-1, IGF2, BMP6, WNT5A, PTHLH, and MAPK14) enriched in both proliferation- and osteogenic differentiation-related processes were screened; GLI-1 had the highest validated |log2FC| value. Overexpression of GLI-1 enhanced the proliferation and osteogenic differentiation of BMSCs, and knockdown of GLI-1 weakened the positive effect of ICA on BMSCs.

CONCLUSION

ICA promoted the proliferation and osteogenic differentiation of impaired BMSCs by upregulating GLI-1.

Role of p53 in promoting BMP9‑induced osteogenic differentiation of mesenchymal stem cells through TGF‑β1

Known as a tumour suppressor gene, p53 also plays a key role in controlling the differentiation of mesenchymal stem cells (MSCs). Bone morphogenetic protein 9 (BMP9) has been identified as a potent factor in inducing osteogenic differentiation of MSCs, but its relationship with p53 remains unclear. The present study revealed that TP53 was expressed at higher levels in MSCs from patients with osteoporosis and was associated with the top 10 core central genes found in the current osteoporosis genetic screen. p53 was expressed in C2C12, C3H10T1/2, 3T3-L1, MEFs, and MG-63 cell lines, and could be upregulated by BMP9, as measured by western blotting and reverse-transcription quantitative PCR (RT-qPCR). Furthermore, overexpression of p53 increased the mRNA and protein levels of osteogenic marker Runx2 and osteopontin, as evaluated by western blotting and RT-qPCR in BMP9-induced MSCs, whereas the p53 inhibitor pifithrin (PFT)-α attenuated these effects. The same trend was found in alkaline phosphatase activities and matrix mineralization, as measured by alkaline phosphatase staining and alizarin red S staining. Moreover, p53 overexpression reduced adipo-differentiation markers of PPARγ and lipid droplet formation, as measured by western blotting, RT-qPCR and oil red O staining, respectively, whereas PFT-α facilitated adipo-differentiation in MSCs. In addition, p53 promoted TGF-β1 expression and inhibition of TGF-β1 by LY364947 partially attenuated the effects of p53 on promoting BMP9-induced MSC osteo-differentiation and inhibiting adipo-differentiation. The inhibitory effect of PFT-α on osteogenic markers and the promoting effect on adipogenic markers can be reversed when combined with TGF-β1. TGF-β1 may enhance the promotion of osteo-differentiation of MSCs by p53 through inhibition of adipo-differentiation. Collectively, by promoting BMP9-induced MSCs bone differentiation and inhibiting adipose differentiation, p53 may be a novel therapeutic target for bone-related diseases.

Biophysical cues to improve the immunomodulatory capacity of mesenchymal stem cells: The progress and mechanisms

Mesenchymal stem cells (MSCs) can maintain immune homeostasis and many preclinical trials with MSCs have been carried out around the world. In vitro culture of MSCs has been found to result in the decline of immunomodulatory capacity, migration and proliferation. To address these problems, simulating the extracellular environment for preconditioning of MSCs is a promising and inexpensive method. Biophysical cues in the external environment that MSCs are exposed to have been shown to affect MSC migration, residency, differentiation, secretion, etc. We review the main ways in which MSCs exert their immunomodulatory ability, and summarize recent advances in mechanical preconditioning of MSCs to enhance immunomodulatory capacity and related mechanical signal sensing and transduction mechanisms.

Roles of focal adhesion proteins in skeleton and diseases

The skeletal system, which contains bones, joints, tendons, ligaments and other elements, plays a wide variety of roles in body shaping, support and movement, protection of internal organs, production of blood cells and regulation of calcium and phosphate metabolism. The prevalence of skeletal diseases and disorders, such as osteoporosis and bone fracture, osteoarthritis, rheumatoid arthritis, and intervertebral disc degeneration, increases with age, causing pain and loss of mobility and creating a huge social and economic burden globally. Focal adhesions (FAs) are macromolecular assemblies that are composed of the extracellular matrix (ECM), integrins, intracellular cytoskeleton and other proteins, including kindlin, talin, vinculin, paxillin, pinch, Src, focal adhesion kinase (FAK) and integrin-linked protein kinase (ILK) and other proteins. FA acts as a mechanical linkage connecting the ECM and cytoskeleton and plays a key role in mediating cell-environment communications and modulates important processes, such as cell attachment, spreading, migration, differentiation and mechanotransduction, in different cells in skeletal system by impacting distinct outside-in and inside-out signaling pathways. This review aims to integrate the up-to-date knowledge of the roles of FA proteins in the health and disease of skeletal system and focuses on the specific molecular mechanisms and underlying therapeutic targets for skeletal diseases.

Matricellular Protein SMOC2 Potentiates BMP9-Induced Osteogenic Differentiation in Mesenchymal Stem Cells through the Enhancement of FAK/PI3K/AKT Signaling

Mesenchymal stem cells (MSCs) can self-renew and differentiate into multiple lineages, making MSC transplantation a promising option for bone regeneration. Both matricellular proteins and growth factors play an important role in regulating stem cell fate. In this study, we investigated the effects of matricellular protein SMOC2 (secreted modular calcium-binding protein 2) on bone morphogenetic protein 9 (BMP9) in mouse embryonic fibroblasts (MEFs) and revealed a possible molecular mechanism underlying this process. We found that SMOC2 was detectable in MEFs and that exogenous SMOC2 expression potentiated BMP9-induced osteogenic markers, matrix mineralization, and ectopic bone formation, whereas SMOC2 knockdown inhibited these effects. BMP9 increased the levels of p-FAK and p-AKT, which were either enhanced or reduced by SMOC2 and FAK silencing, respectively. BMP9-induced osteogenic markers were increased by SMOC2, and this increase was partially abolished by silencing FAK or LY290042. Furthermore, we found that general transcription factor 2I (GTF2I) was enriched at the promoter region of SMOC2 and that integrin β1 interacted with SMOC2 in BMP9-treated MEFs. Our findings demonstrate that SMOC2 can promote BMP9-induced osteogenic differentiation by enhancing the FAK/PI3K/AKT pathway, which may be triggered by facilitating the interaction between SMOC2 and integrin β1.

The potential regulatory role of BMP9 in inflammatory responses

Inflammation is a protective response of the body to pathogens and injury. Hence, it is particularly important to explore the pathogenesis and key regulatory factors of inflammation. BMP9 is a unique member of the BMP family, which is widely known for its strong osteogenic potential and insensitivity to the inhibition of BMP3. Recently, several studies have reported an underlying pivotal link between BMP9 and inflammation. What is clear, though not well understood, is that BMP9 plays a role in inflammation in a carefully choreographed manner in different contexts. In this review, we have summarized current studies focusing on BMP9 and inflammation in various tissues and the latest advances in BMP9 expression, signal transduction, and crystal structure to better understand the relationship between BMP9 and inflammation. In addition, we also briefly summarized the inflammatory characteristics of some TGF-β superfamily members to provide better insights and ideas for the study of BMP9 and inflammation.

miR-129-5p Promotes Osteogenic Differentiation of BMSCs and Bone Regeneration via Repressing Dkk3

Objective

Accumulating evidence indicates that microRNAs (miRNAs) play crucial roles in osteogenic differentiation. However, the associated mechanisms remain elusive. This paper is aimed at exploring the role of miR-129-5p in regulating bone marrow mesenchymal stem cell (BMSC) differentiation and bone regeneration in vivo and in vitro.

Methods

BMSCs were transduced by miR-129-5p mimic, miR-129-5p inhibitor, and negative control lentivirus. The ability of BMSC differentiation to osteoblast was tested by alkaline phosphatase (ALP) and alizarin red staining (ARS). The expression of osteogenic genes (Runx2, Bmp2, and OCN) was examined via quantitative RT-PCR and western blot. A mouse model of calvaria defect was investigated by Micro-CT, immunohistochemistry, and histological examination. The luciferase reporter gene assay was performed to confirm the binding between Dkk3 and miR-129-5p. For the transfection experiments, lipofectamine 3000 was used to transfect pcDNA-Dkk3 into BMSCs to overexpress Dkk3. Coimmunoprecipitation and immunofluorescent localization assay were included for exploring the role of Dkk3 and β-catenin.

Results

miR-129-5p was induced in BMSCs and MSC cell line C3H10T1/2 cells under osteogenic medium. Overexpression of miR-129-5p significantly promoted osteogenic differentiation of BMSCs in vitro. Moreover, BMSCs transduced with miR-129-5p mimic exhibited better bone regeneration compared with BMSCs transduced with control counterpart in vivo. Luciferase and western blot data showed that Dickkopf3 (Dkk3) is a target gene of miR-129-5p and the expression of Dkk3 was inhibited in BMSCs transduced with miR-129-5p mimic but enhanced in BMSCs transduced with miR-129-5p inhibitor. In addition, Dkk3 interacted with β-catenin directly.

Conclusions

miR-129-5p promotes osteogenic differentiation of BMSCs and bone regeneration, and miR-129-5p/Dkk3 axis may be new potential targets for the treatment of bone defect and bone loss.

Intra-articular injection of human synovium-derived mesenchymal stem cells in beagles with surgery-induced osteoarthritis

BACKGROUND

Recently, cell-based tissue engineering approaches using mesenchymal stem cells (MSCs) have been used to treat osteoarthritis (OA). However, the efficacy of human synovium-derived MSCs (hSD-MSCs) has not yet been tested in a canine model of OA. The purpose of this study was to investigate the therapeutic effects of intra-articular hSD-MSC injections in a canine OA model.

METHODS

Sixty beagles underwent surgical manipulation to induce OA and received intra-articular injection 4 weeks after surgery. The dogs were divided into five groups (n = 12) according to the injection material: G1, sham group; G2, control group injected with phosphate-buffered saline; G3, G4, and G5, experimental groups injected with different hSD-MSC dosages (G3, 2.4 × 10⁶ cells; G4, 4.8 × 10⁶ cells; G5, 9.6 × 10⁶ cells). Magnetic resonance imaging (MRI) and histopathological and immunohistochemical examinations were performed 6 and 24 weeks after injection.

RESULTS

MRI revealed significant improvements in synovitis 24 weeks after injection in the hSD-MSC-injected groups (G3-G5). Histopathologic analyses showed that cartilage structure and proteoglycan staining were also significantly improved in these groups (G3-G5) 6 weeks after injection and improved further after 24 weeks. Immunohistochemical analysis revealed significant differences in the levels of collagen types I and II between the hSD-injected groups (G3-G5), indicating a similar extracellular matrix (ECM) composition to naïve articular cartilage.

CONCLUSION

Our study demonstrated for the first time that intra-articular hSD-MSC injection ameliorates the progression of canine OA by restoring cartilage, promoting ECM synthesis, and inhibiting the inflammatory response.

The Crosstalk between FAK and Wnt Signaling Pathways in Cancer and Its Therapeutic Implication

Focal adhesion kinase (FAK) and Wnt signaling pathways are important contributors to tumorigenesis in several cancers. While most results come from studies investigating these pathways individually, there is increasing evidence of a functional crosstalk between both signaling pathways during development and tumor progression. A number of FAK-Wnt interactions are described, suggesting an intricate, context-specific, and cell type-dependent relationship. During development for instance, FAK acts mainly upstream of Wnt signaling; and although in intestinal homeostasis and mucosal regeneration Wnt seems to function upstream of FAK signaling, FAK activates the Wnt/β-catenin signaling pathway during APC-driven intestinal tumorigenesis. In breast, lung, and pancreatic cancers, FAK is reported to modulate the Wnt signaling pathway, while in prostate cancer, FAK is downstream of Wnt. In malignant mesothelioma, FAK and Wnt show an antagonistic relationship: Inhibiting FAK signaling activates the Wnt pathway and vice versa. As the identification of effective Wnt inhibitors to translate in the clinical setting remains an outstanding challenge, further understanding of the functional interaction between Wnt and FAK could reveal new therapeutic opportunities and approaches greatly needed in clinical oncology. In this review, we summarize some of the most relevant interactions between FAK and Wnt in different cancers, address the current landscape of Wnt- and FAK-targeted therapies in different clinical trials, and discuss the rationale for targeting the FAK-Wnt crosstalk, along with the possible translational implications.

Steering cell behavior through mechanobiology in 3D: A regenerative medicine perspective

Mechanobiology, translating mechanical signals into biological ones, greatly affects cellular behavior. Steering cellular behavior for cell-based regenerative medicine approaches requires a thorough understanding of the orchestrating molecular mechanisms, among which mechanotransducive ones are being more and more elucidated. Because of their wide use and highly mechanotransduction dependent differentiation, this review focuses on mesenchymal stromal cells (MSCs), while also briefly relating the discussed results to other cell types. While the mechanotransduction pathways are relatively well-studied in 2D, much remains unknown of the role and regulation of these pathways in 3D. Ultimately, cells need to be cultured in a 3D environment to create functional de novo tissue. In this review, we explore the literature on the roles of different material properties on cellular behavior and mechanobiology in 2D and 3D. For example, while stiffness plays a dominant role in 2D MSCs differentiation, it seems to be of subordinate importance in 3D MSCs differentiation, where matrix remodeling seems to be key. Also, the role and regulation of some of the main mechanotransduction players are discussed, focusing on MSCs. We have only just begun to fundamentally understand MSCs and other stem cells behavior in 3D and more fundamental research is required to advance biomaterials able to replicate the stem cell niche and control cell activity. This better understanding will contribute to smarter tissue engineering scaffold design and the advancement of regenerative medicine.

A Composite Tissue Engineered Bone Material Consisting of Bone Mesenchymal Stem Cells, Bone Morphogenetic Protein 9 (BMP9) Gene Lentiviral Vector, and P3HB4HB Thermogel (BMSCs-LV-BMP9-P3HB4HB) Repairs Calvarial Skull Defects in Rats by Expression of Osteogenic Factors

Background

Bone tissue engineering has been proven to be an appropriate approach for treating bone defects. This study aimed to investigate the effects and mechanism of a composite tissue engineered bone material consisting of bone mesenchymal stem cells (BMSCs), bone morphogenetic protein (BMP9) gene lentiviral vector, and P3HB4HB thermogel (BMSCs-LV-BMP9-P3HB4HB) on calvarial skull defects in rats.

Material/Methods

LV-BMP9 viral vector was structured and infected to BMSCs-P3HB4HB composite scaffold, which was named as BMSCs-P3HB4HB composite bone repair material. Adipogenic differentiation was determined by oil-red O (ORO) and alkaline phosphatase (ALP) staining. Osteogenic differentiation was measured using Alizarin red staining. Cell viability was examined using Cell-Counting Kit-8 (CCK-8) assay. Protein expression of osteogenic factors, including BMP9, runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), osteopontin (OPN), and osterix (OSX), was detected with Western blot assay and immunohistochemistry. mRNA of these osteogenic factors was examined by RT-PCR. Histological changes were examined with hematoxylin and eosin (H&E) and Masson’s trichrome staining. Bone repair was measured using micro-computed tomography (micro-CT).

Results

BMSCs and LV-BMP9-infected BMSCs demonstrated adipogenic and osteogenic differentiation potential. BMSCs-P3HB4HB scaffold demonstrated good cell-tissue compatibility. BMSCs-LV-BMP9-P3HB4HB exhibited significantly higher osteogenic ability and cell viability of BMSCs compared to BMSCs-LV-P3HB4HB (p<0.05). BMSCs-LV-BMP9-P3HB4HB significantly promoted osteogenic factors (RUNX2, OCN, OPN, and OSX) expression compared to the BMSCs-LV-P3HB4HB group (p<0.05) in both BMSCs and in calvarial defect rats. BMSCs-LV-BMP9-P3HB4HB demonstrated stronger repair ability. BMSCs-LV-BMP9-P3HB4HB significantly alleviated pathological injury and increased collagen fiber production compared to the BMSCs-LV-P3HB4HB group (p<0.05).

Conclusions

BMSCs-LV-BMP9-P3HB4HB composite bone repair material can effectively repair injured skull tissues of calvarial defect rats through triggering osteogenic factors expression. The present generated bone repair material may have applications in tissue engineering in regeneration of bone defects.

From the Performance to the Essence: The Biological Mechanisms of How Tantalum Contributes to Osteogenesis

Despite the brilliant bioactive performance of tantalum as an orthopedic biomaterial verified through laboratory researches and clinical practice in the past decades, scarce evidences about the essential mechanisms of how tantalum contributes to osteogenesis were systematically discussed. Up to now, a few studies have uncovered preliminarily the biological mechanism of tantalum in osteogenic differentiation and osteogenesis; it is of great necessity to map out the panorama through which tantalum contributes to new bone formation. This minireview summarized current advances to demonstrate the probable signaling pathways and underlying molecular cascades through which tantalum orchestrates osteogenesis, which mainly contain Wnt/β-catenin signaling pathway, BMP signaling pathway, TGF-β signaling pathway, and integrin signaling pathway. Limits of subsistent studies and further work are also discussed, providing a novel vision for the study and application of tantalum.

Protocadherins at the Crossroad of Signaling Pathways

Protocadherins (Pcdhs) are cell adhesion molecules that belong to the cadherin superfamily, and are subdivided into clustered (cPcdhs) and non-clustered Pcdhs (ncPcdhs) in vertebrates. In this review, we summarize their discovery, expression mechanisms, and roles in neuronal development and cancer, thereby highlighting the context-dependent nature of their actions. We furthermore provide an extensive overview of current structural knowledge, and its implications concerning extracellular interactions between cPcdhs, ncPcdhs, and classical cadherins. Next, we survey the known molecular action mechanisms of Pcdhs, emphasizing the regulatory functions of proteolytic processing and domain shedding. In addition, we outline the importance of Pcdh intracellular domains in the regulation of downstream signaling cascades, and we describe putative Pcdh interactions with intracellular molecules including components of the WAVE complex, the Wnt pathway, and apoptotic cascades. Our overview combines molecular interaction data from different contexts, such as neural development and cancer. This comprehensive approach reveals potential common Pcdh signaling hubs, and points out future directions for research. Functional studies of such key factors within the context of neural development might yield innovative insights into the molecular etiology of Pcdh-related neurodevelopmental disorders.

BMP9 is a potential therapeutic agent for use in oral and maxillofacial bone tissue engineering

Oral and maxillofacial surgery is often challenging due to defective bone healing owing to the microbial environment of the oral cavity, the additional involvement of teeth and esthetic concerns. Insufficient bone volume as a consequence of aging and some oral and maxillofacial surgical procedures, such as tumor resection of the jaw, may further impact facial esthetics and cause the failure of certain procedures, such as oral and maxillofacial implantation. Bone morphogenetic protein (BMP) 9 (BMP9) is one of the most effective BMPs to induce the osteogenic differentiation of different stem cells. A large cross-talk network that includes the BMP9, Wnt/β, Hedgehog, EGF, TGF-β and Notch signaling pathways finely regulates osteogenesis induced by BMP9. Epigenetic control during BMP9-induced osteogenesis is mainly dependent on histone deacetylases (HDACs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), which adds another layer of complexity. As a result, all these factors work together to orchestrate the molecular and cellular events underlying BMP9-related tissue engineering. In this review, we summarize our current understanding of the SMAD-dependent and SMAD-independent BMP9 pathways, with a particular focus on cross-talk and cross-regulation between BMP9 and other major signaling pathways in BMP9-induced osteogenesis. Furthermore, recently discovered epigenetic regulation of BMP9 pathways and the molecular and cellular basis of the application of BMP9 in tissue engineering in current oral and maxillofacial surgery and other orthopedic-related clinical settings are also discussed.

Bioinformatics analysis of the biological changes involved in the osteogenic differentiation of human mesenchymal stem cells

The mechanisms underlying the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) remain unclear. In the present study, we aimed to identify the key biological processes during osteogenic differentiation. To this end, we downloaded three microarray data sets from the Gene Expression Omnibus (GEO) database: GSE12266, GSE18043 and GSE37558. Differentially expressed genes (DEGs) were screened using the limma package, and enrichment analysis was performed. Protein-protein interaction network (PPI) analysis and visualization analysis were performed with STRING and Cytoscape. A total of 240 DEGs were identified, including 147 up-regulated genes and 93 down-regulated genes. Functional enrichment and pathways of the present DEGs include extracellular matrix organization, ossification, cell division, spindle and microtubule. Functional enrichment analysis of 10 hub genes showed that these genes are mainly enriched in microtubule-related biological changes, that is sister chromatid segregation, microtubule cytoskeleton organization involved in mitosis, and spindle microtubule. Moreover, immunofluorescence and Western blotting revealed dramatic quantitative and morphological changes in the microtubules during the osteogenic differentiation of human adipose-derived stem cells. In summary, the present results provide novel insights into the microtubule- and cytoskeleton-related biological process changes, identifying candidates for the further study of osteogenic differentiation of the mesenchymal stem cells.

The mechanism of miR-889 regulates osteogenesis in human bone marrow mesenchymal stem cells

Background

Bone marrow mesenchymal stem cells (BMMSCs) can be used for bone regeneration in the specified condition. Osteogenic differentiation of BMMSCs is controlled by microRNAs (miRNAs) and other factors. This study was aimed to identify the role and mechanism of miR-889 in regulating the osteogenic differentiation of BMMSCs.

Methods

Osteoporosis patients and normal control bone tissues were collected and used PCR techniques to identify the change of miR-889 and WNT7A. Moreover, the dynamic change of miR-889 and WNT7A during osteogenic differentiation of BMMSCs was also measured. Bioinformatic analysis was performed to identify the target genes and potential pathways of miR-889. Then, we constructed miR-889 mimic and inhibitor, ALP staining, ARS, osteoblastic-related protein, and Wnt β-catenin signaling pathway-related protein were also measured. WNT7A siRNA was also used to verify the function of miR-889.

Results

In the present study, we showed that miR-889 expression was upregulated in osteoporosis patients than healthy control. However, the miR-889 expression was downregulated during osteogenic differentiation. Bioinformatics analysis found that miR-889 targets 666 genes and mainly through Wnt β-catenin signaling pathway. Administrated miR-889 mimic, the ALP activity, and calcium deposition were decreased than the control group, while miR-889 inhibitor shown the opposite trend. And miR-889 could bind the 3′UTR of WNT7A. We further used WNT7A siRNA to explore the function of miR-889, and the results revealed that co-cultured with miR-889 inhibitor and WNT7A siRNA was associated with a reduction of ALP activity and calcium deposition and osteoblastic-related proteins than miR-889 inhibitor alone.

Conclusion

Our results revealed that miR-889 plays a negative role in inducing osteogenic differentiation of BMSCs through Wnt β-catenin signaling pathway.

Effects of hypoxia‑inducible factor‑1α on the proliferation and apoptosis of human synovial mesenchymal stem cells

Hypoxia is a constant feature of the synovial microenvironment. How synovial mesenchymal stem cells (SMSCs) proliferate and differentiate in a hypoxic environment over a long period of time has aroused the interest of researchers. The aim of the present study was to explore the effects of hypoxia‑inducible factor‑1α (HIF‑1α) on the proliferation and apoptosis of human SMSCs. SMSCs were harvested and cultured under different concentration of oxygen, normoxia (21% O2), hypoxia (5% O2) and severe hypoxia (0.5% O2) to determine its effect on the expression of HIF‑1α. Then, the cells were collected and cell proliferation and apoptosis were detected at severe hypoxia (0.5% O2) and hypoxia (5% O2) conditions following HIF‑1α siRNA transfection. There were no significant changes in cellular proliferation or apoptosis when cultured in normoxia (21% O2), hypoxia (5% O2) or severe hypoxia (0.5% O2). However, the mRNA and protein expression of HIF‑1α were markedly upregulated in the hypoxic conditions. Further experiments suggested that the proliferation of SMSCs was obviously suppressed and apoptosis was markedly increased under severe hypoxic (0.5%) and hypoxic (5% O2) conditions following HIF‑1α siRNA transfection. In conclusion, HIF‑1α effectively improved the tolerance of SMSCs to hypoxia, which may promote cellular proliferation and prevent the apoptosis of SMSCs under hypoxic conditions.