Mangiferin enhances endochondral ossification-based bone repair in massive bone defect by inducing autophagy through activating AMP-activated protein kinase signaling pathway

Exploring calcium-free alternatives in endochondral bone repair tested on In vivo trials - A review

Bone repair via endochondral ossification is a complex process for the critical size reparation of bone defects. Tissue engineering strategies are being developed as alternative treatments to autografts or allografts. Most approaches to bone regeneration involve the use of calcium composites. However, exploring calcium-free alternatives in endochondral bone repair has emerged as a promising way to contribute to bone healing. By analyzing researches from the last ten years, this review identifies the potential benefits of such alternatives compared to traditional calcium-based approaches. Understanding the impact of calcium-free alternatives on endochondral bone repair can have profound implications for orthopedic and regenerative medicine. This review evaluates the efficacy of calcium-free alternatives in endochondral bone repair through in vivo trials. The findings may guide future research to develop innovative strategies to improve endochondral bone repair without relying on calcium. Exploring alternative approaches may lead to the discovery of novel therapies that improve bone healing outcomes.

Natural polysaccharides protect against diet-induced obesity by improving lipid metabolism and regulating the immune system

Unhealthy dietary patterns-induced obesity and obesity-related complications pose a great threat to human health all over the world. Accumulating evidence suggests that the pathophysiology of obesity and obesity-associated metabolic disorders is closely associated with dysregulation of lipid and energy metabolism, and metabolic inflammation. In this review, three potential anti-obesity mechanisms of natural polysaccharides are introduced. Firstly, natural polysaccharides protect against diet-induced obesity directly by improving lipid and cholesterol metabolism. Since the immunity also affects lipid and energy metabolism, natural polysaccharides improve lipid and energy metabolism by regulating host immunity. Moreover, diet-induced mitochondrial dysfunction, prolonged endoplasmic reticulum stress, defective autophagy and microbial dysbiosis can disrupt lipid and/or energy metabolism in a direct and/or inflammation-induced manner. Therefore, natural polysaccharides also improve lipid and energy metabolism and suppress inflammation by alleviating mitochondrial dysfunction and endoplasmic reticulum stress, promoting autophagy and regulating gut microbiota composition. Specifically, this review comprehensively summarizes underlying anti-obesity mechanisms of natural polysaccharides and provides a theoretical basis for the development of functional foods. For the first time, this review elucidates anti-obesity mechanisms of natural polysaccharides from the perspectives of their hypolipidemic, energy-regulating and immune-regulating mechanisms.

CpG ODN/Mangiferin Dual Delivery through Calcium Alginate Hydrogels Inhibits Immune-Mediated Osteoclastogenesis and Promotes Alveolar Bone Regeneration in Mice

The immune system plays an important role in the skeletal system during bone repair and regeneration. The controlled release of biological factors from the immune system could facilitate and optimize the bone remodeling process through the regulation of the activities of bone cells. This study aimed to determine the effect of the controlled delivery of immunomodulatory biologicals on bone regeneration. Immunostimulatory cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODN) and glucosylxanthone Mangiferin (MAG)-embedded microbeads were incubated with P. gingivalis-challenged splenocytes, or co-cultured with RAW264.7 cells. The effect of CpG ODN/MAG-containing microbeads on bone regeneration was then tested in vivo in a mouse alveolar bone defect model. The results demonstrated that MAG significantly antagonized P. gingivalis proliferation and reduced the live/dead cell ratio. After the addition of CpG ODN + MAG microbeads, anti-inflammatory cytokines IL-10 and IL-4 were upregulated on day 2 but not day 4, whereas pro-inflammatory cytokine IL-1β responses showed no difference at both timepoints. RANKL production by splenocytes and TRAP+ cell formation of RAW264.7 cells were inhibited by the addition of CpG ODN + MAG microbeads. Alveolar bony defects, filled with CpG ODN + MAG microbeads, showed significantly increased new bone after 4 weeks. In summary, this study evaluated a new hydrogel-based regimen for the local delivery and controlled release of biologicals to repair and regenerate alveolar bony defects. The combined CpG ODN + MAG treatment may promote alveolar bone regeneration through the anti-microbial/anti-inflammatory effects and the inhibition of RANKL-mediated osteoclastogenesis.

Mechanism of Schwann cells in diabetic peripheral neuropathy: A review

Diabetic peripheral neuropathy (DPN) is the most common neuropathy in the world, mainly manifested as bilateral symmetry numbness, pain or paresthesia, with a high rate of disability and mortality. Schwann cells (SCs), derived from neural ridge cells, are the largest number of glial cells in the peripheral nervous system, and play an important role in DPN. Studies have found that SCs are closely related to the pathogenesis of DPN, such as oxidative stress, endoplasmic reticulum stress, inflammation, impaired neurotrophic support and dyslipidemia. This article reviews the mechanism of SCs in DPN.

A high-concentrate diet induces inflammatory injury via regulating Ca2+/CaMKKβ-mediated autophagy in mammary gland tissue of dairy cows

Introduction

Calmodulin-dependent protein kinase β (CaMKKβ) is closely related to Ca²⁺ concentration. An increase in Ca²⁺ concentration in the cytoplasm activates CaMKKβ, and activated CaMKKβ affects the activities of AMPK and mTOR and induces autophagy. A high-concentrate diet leads to Ca²⁺ disorder in mammary gland tissue.

Objectives

Therefore, this study mainly investigated the induction of mammary gland tissue autophagy by a high-concentrate diet and the specific mechanism of lipopolysaccharide (LPS)-induced autophagy in bovine mammary epithelial cells (BMECs).

Material and Methods

Twelve mid-lactation Holstein dairy cows were fed with a 40% concentrate diet (LC) and a 60% concentrate diet (HC) for 3 weeks. At the end of the trial, rumen fluid, lacteal vein blood, and mammary gland tissue were collected. The results showed that the HC diet significantly decreased rumen fluid pH, with a pH lower than 5.6 for more than 3 h, indicating successfully induction of subacute rumen acidosis (SARA). The mechanism of LPS-induced autophagy in BMECs was studied in vitro. First, the cells were divided into a Ctrl group and LPS group to study the effects of LPS on the concentration of Ca²⁺ and autophagy in BMECs. Then, cells were pretreated with an AMPK inhibitor (compound C) or CaMKKβ inhibitor (STO-609) to investigate whether the CaMKKβ-AMPK signaling pathway is involved in LPS-induced BMEC autophagy.

Results

The HC diet increased the concentration of Ca²⁺ in mammary gland tissue and pro-inflammatory factors in plasma. The HC diet also significantly increased the expression of CaMKKβ, AMPK, and autophagy-related proteins, resulting in mammary gland tissue injury. In vitro cell experiments showed that LPS increased intracellular Ca²⁺ concentration and upregulated protein expression of CaMKKβ, AMPK, and autophagy-related proteins. Compound C pretreatment decreased the expression of proteins related to autophagy and inflammation. In addition, STO-609 pretreatment not only reversed LPS-induced BMECs autophagy but also inhibited the protein expression of AMPK, thereby alleviating the inflammatory response in BMECs. These results suggest that inhibition of the Ca²⁺/CaMKKβ-AMPK signaling pathway reduces LPS-induced autophagy, thereby alleviating inflammatory injury of BMECs.

Conclusion

Therefore, SARA may increase the expression of CaMKKβ by increasing Ca²⁺ levels and activate autophagy through the AMPK signaling pathway, thereby inducing inflammatory injury in mammary gland tissue of dairy cows.

Close-to-native bone repair via tissue-engineered endochondral ossification approaches

In order to solve the clinical challenges related to bone grafting, several tissue engineering (TE) strategies have been proposed to repair critical-sized defects. Generally, the classical TE approaches are designed to promote bone repair via intramembranous ossification. Although promising, strategies that direct the osteogenic differentiation of mesenchymal stem/stromal cells are usually characterized by a lack of functional vascular supply, often resulting in necrotic cores. A less explored alternative is engineering bone constructs through a cartilage-mediated approach, resembling the embryological process of endochondral ossification. The remodeling of an intermediary hypertrophic cartilaginous template triggers vascular invasion and bone tissue deposition. Thus, employing this knowledge can be a promising direction for the next generation of bone TE constructs. This review highlights the most recent biomimetic strategies for applying endochondral ossification in bone TE while discussing the plethora of cell types, culture conditions, and biomaterials essential to promote a successful bone regeneration process.

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

Mangiferin is a xanthone glucoside extracted from multiple plants, which has been shown to inhibit bone resorption and alleviate osteoporosis. However, the effect of purified Mangiferin on osteoporosis and its specific mechanisms is unknown. This study aimed to explore whether Mangiferin can promote osteogenic differentiation and alleviate osteoporosis in ovariectomized (OVX) mice and explore the potential mechanisms. Different concentrations and durations of Mangiferin were applied to MC3T3-E1 cells. The optimal concentration and duration of Mangiferin were determined by evaluating the cell viability via cell count kit-8 (CCK-8). The gene and protein expressions of AXL, ERK5, and osteogenic differentiation markers, including BMP2, Collagen1, OPN, Osterix, and Runx2, were detected using western blotting, qRT-PCR, immunofluorescence, and flow cytometry. Mangiferin was administered to OVX mice, and the severity of osteoporosis was evaluated by H and E staining, immunohistochemistry (IHC), microscopic computed-tomography (micro-CT) scanning, western blotting, and immunofluorescence of bone tissue. We found that Mangiferin promoted osteogenic differentiation in a dose-dependent manner at concentrations less than 30 μM. The 30 μM Mangiferin significantly upregulated the expression of AXL, ERK5, and osteogenic differentiation, including the ALP activity, percentage of alizarin red, and the levels of osteogenic differentiation markers. However, these expression levels decreased when AXL was knocked down in MC3T3-E1 cells and it could not be rescued by Mangiferin. Mangiferin relieved osteoporosis in OVX mice without causing severe organ damage. This study concluded that Mangiferin promoted osteogenic differentiation of MC3T3-E1 cells and alleviated osteoporosis in OVX mice. The potential mechanism was via the AXL/ERK5 pathway.

Long non-coding RNA HCAR promotes endochondral bone repair by upregulating VEGF and MMP13 in hypertrophic chondrocyte through sponging miR-15b-5p

Endochondral bone formation is an important route for bone repair. Although emerging evidence has revealed the functions of long non-coding RNAs (lncRNAs) in bone and cartilage development, the effect of lncRNAs in endochondral bone repair is still largely unknown. Here, we identified a lncRNA, named Hypertrophic Chondrocyte Angiogenesis-related lncRNA (HCAR), and proved it to promote the endochondral bone repair by upregulating the expression of matrix metallopeptidase 13 (Mmp13) and vascular endothelial growth factor α (Vegfa) in hypertrophic chondrocytes. Lnc-HCAR knockdown in hypertrophic chondrocytes restrained the cartilage matrix remodeling and decrease the CD31^hiEmcn^hi vessels number in a bone repair model. Mechanistically, we proved that lnc-HCAR was mainly enriched in the cytoplasm using fluorescence in situ hybridization (FISH) assay, and it acted as a molecular sponge for miR-15b-5p. Further, in hypertrophic chondrocytes, lnc-HCAR competitively bound to miR-15b-5p to increase Vegfa and Mmp13 expression. Our results proved that lncRNA is deeply involved in endochondral bone repair, which will provide a new theoretical basis for future strategies for promoting fracture healing.

Phytochemicals Mediate Autophagy Against Osteoarthritis by Maintaining Cartilage Homeostasis

Osteoarthritis (OA) is a common degenerative joint disease and is a leading cause of disability and reduced quality of life worldwide. There are currently no clinical treatments that can stop or slow down OA. Drugs have pain-relieving effects, but they do not slow down the course of OA and their long-term use can lead to serious side effects. Therefore, safe and clinically appropriate long-term treatments for OA are urgently needed. Autophagy is an intracellular protective mechanism, and targeting autophagy-related pathways has been found to prevent and treat various diseases. Attenuation of the autophagic pathway has now been found to disrupt cartilage homeostasis and plays an important role in the development of OA. Therefore, modulation of autophagic signaling pathways mediating cartilage homeostasis has been considered as a potential therapeutic option for OA. Phytochemicals are active ingredients from plants that have recently been found to reduce inflammatory factor levels in cartilage as well as attenuate chondrocyte apoptosis by modulating autophagy-related signaling pathways, which are not only widely available but also have the potential to alleviate the symptoms of OA. We reviewed preclinical studies and clinical studies of phytochemicals mediating autophagy to regulate cartilage homeostasis for the treatment of OA. The results suggest that phytochemicals derived from plant extracts can target relevant autophagic pathways as complementary and alternative agents for the treatment of OA if subjected to rigorous clinical trials and pharmacological tests.

Bifidobacterium longum subsp. infantis YB0411 Inhibits Adipogenesis in 3T3-L1 Pre-adipocytes and Reduces High-Fat-Diet-Induced Obesity in Mice

Although the health benefits of probiotics have been widely known for decades, there has still been limited use of probiotic bacteria in anti-obesity therapy. Herein, we demonstrated the role of Bifidobacterium longum subsp. infantis YB0411 (YB, which was selected by an in vitro adipogenesis assay) in adipogenic differentiation in 3T3-L1 pre-adipocytes. We observed that YB-treatment effectively reduced triglyceride accumulation and the expression of CCAAT/enhancer-binding protein α, β, and δ (C/EBPα, C/EBPβ, and C/EBPδ), peroxisome proliferator-activated receptor γ (PPARγ), fatty acid-binding protein 4 (aP2), and acetyl-CoA carboxylase (ACC). YB-treatment also reduced the levels of core autophagic markers (p62 and LC3B) in 3T3-L1 pre-adipocytes. Small-interfering-RNA-mediated knockdown and competitive-chemical-inhibition assays showed that AMP-activated protein kinase (AMPK) commenced the anti-adipogenic effect of YB. In addition, YB supplement markedly reduced body weight and fat accretion in mice with high-fat-diet-induced obesity. Our findings suggest that YB may be used as a potential probiotic candidate to ameliorate obesity.

Laminin alpha 4 promotes bone regeneration by facilitating cell adhesion and vascularization

Selective cell retention (SCR) has been widely used as a bone tissue engineering technique for the real-time fabrication of bone grafts. The greater the number of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) retained in the scaffold, the better the osteoinductive and angiogenic properties of the scaffold's microenvironment. Improved bioscaffold properties in turn lead to improved bone graft survival, bone regeneration, and angiogenesis. Laminin plays a key role in cell-matrix adhesion, cell proliferation, and differentiation. We designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 (CBD-LN peptide) to supplement the functional surface of a collagen-based decalcified bone matrix (DBM) scaffold. This scaffold promoted MSCs and EPCs early cell adhesion through up-regulating the expression of integrin α5β1 and integrin αvβ3 respectively, thus accelerated the following cell spreading, proliferation, and differentiation. Interestingly, it promoted the retention of MSCs (CD90⁺/CD105⁺ cells) and EPCs (CD31⁺ cells) in the scaffold following the use of clinical SCR technology. Furthermore, the DBM/CBD-LN scaffold induced the formation of type H vessels through the activation of the HIF-1α signaling pathway. The DBM/CBD-LN scaffold displayed rapid bone formation and angiogenesis in vivo, suggesting that it might be used as a new biomaterial in bone tissue engineering. STATEMENT OF SIGNIFICANCE: Selective cell retention technology (SCR) has been utilized in clinical settings to manufacture bioactive bone grafts. Specifically, demineralized bone matrix (DBM) is a widely-used SCR clinical biomaterial but it displays poor adhesion performance and angiogenic activity. In this work, we designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 to supplement the functional surface of a collagen-based DBM scaffold. This bioscaffold promoted SCR-mediated MSCs and EPCs early cell adhesion, thus accelerated the following cell spreading, proliferation, and differentiation. Our results indicate this bioscaffold greatly induced osteogenesis and angiogenesis in vivo. In general, this bioscaffold has a good prospect for SCR application and may provide highly bioactive bone implant in clinical environment.

Turning Nature's own processes into design strategies for living bone implant biomanufacturing: a decade of Developmental Engineering

A decade after the term developmental engineering (DE) was coined to indicate the use of developmental processes as blueprints for the design and development of engineered living implants, a myriad of proof-of-concept studies demonstrate the potential of this approach in small animal models. This review provides an overview of DE work, focusing on applications in bone regeneration. Enabling technologies allow to quantify the distance between in vitro processes and their developmental counterpart, as well as to design strategies to reduce that distance. By embedding Nature's robust mechanisms of action in engineered constructs, predictive large animal data and subsequent positive clinical outcomes can be gradually achieved. To this end, the development of next generation biofabrication technologies should provide the necessary scale and precision for robust living bone implant biomanufacturing.

Bone defect reconstruction via endochondral ossification: A developmental engineering strategy

Traditional bone tissue engineering (BTE) strategies induce direct bone-like matrix formation by mimicking the embryological process of intramembranous ossification. However, the clinical translation of these clinical strategies for bone repair is hampered by limited vascularization and poor bone regeneration after implantation in vivo. An alternative strategy for overcoming these drawbacks is engineering cartilaginous constructs by recapitulating the embryonic processes of endochondral ossification (ECO); these constructs have shown a unique ability to survive under hypoxic conditions as well as induce neovascularization and ossification. Such developmentally engineered constructs can act as transient biomimetic templates to facilitate bone regeneration in critical-sized defects. This review introduces the concept and mechanism of developmental BTE, explores the routes of endochondral bone graft engineering, highlights the current state of the art in large bone defect reconstruction via ECO-based strategies, and offers perspectives on the challenges and future directions of translating current knowledge from the bench to the bedside.

YAP1 regulates chondrogenic differentiation of ATDC5 promoted by temporary TNF-α stimulation through AMPK signaling pathway

Local injection of tumor necrosis factor-alpha (TNF-α) at bone fracture sites during the early stage of the inflammatory response is reported to improve fracture repair in a murine model. However, the underlying mechanism is unclear. Endochondral bone formation, a process that is highly related to fracture repair, requires a certain amount of chondrocyte hypertrophy. This study aimed to investigate the effect of TNF-α on the differentiation of murine chondrogenic ATDC5 cells and the underlying mechanism. In this study, improved chondrogenic differentiation of ATDC5 cells was achieved by brief TNF-α stimulation. Moreover, the expression of Yes-associated protein 1 (YAP1) was suppressed after brief TNF-α stimulation. The expressions of inflammatory mediators and chondrogenic and hypertrophic-associated genes in ATDC5 cells triggered by TNF-α were suppressed in the YAP1 overexpression group but enhanced in the YAP1 knockdown group. Mechanistically, TNF-α-induced activation of the 5' AMP-activated protein kinase (AMPK) signaling pathway was regulated by YAP1, as revealed by the phosphorylated-AMPK/AMPK change ratios in the YAP1 overexpression and knockdown groups, respectively. Moreover, the potential for TNF-α to enhance chondrogenic differentiation could be partially reversed with an AMPK inhibitor. Taken together, we demonstrate, for the first time, that YAP1 modulates the ability of TNF-α to enhance chondrocyte differentiation partly through AMPK signaling.

Progress of orthopaedic research in China over the last decade

Objective

To summarize the representative scientific achievements in the past decade, and discuss the future challenges and directions for orthopaedic research in China.

Methods

In this review, we used the data provided by National Natural Science Foundation of China (NSFC) for analysis.

Results

Over the last decade, NSFC has initiated various research programs with a total funding of over 1149 million RMB to support orthopaedic exploration. Under the strong support of NSFC, great progresses have been made in basic research, talent training, platform construction and the clinical translation in the field of orthopaedics in China.

Conclusion

In general, since the establishment of the Department of Health Sciences of NSFC 10 years ago, both the amount of funding and the scale of researchers in the field of orthopaedic research have increased substantially. Despite of several shortcomings in orthopaedic research, with continuous support from NSFC both in funding and in policy, we believe that the orthopaedic research in China will surely make steady and significant progress.

The translational potential of this article

This article summarizes the representative scientific achievements in the past decade and puts forward the future challenges and directions for orthopaedic research in China.

Mangiferin induces the expression of a thermogenic signature via AMPK signaling during brown-adipocyte differentiation

Mangiferin (MF) from Mangifera indica has been serendipitously found to ameliorate obesity and is used as an antioxidant, anti-inflammatory, antimicrobial, and anticancer agent. Nonetheless, the mechanism of MF-induced brown-adipose-tissue activation has not been studied. Therefore, we investigated the effect of MF on thermogenic features during brown-adipocyte differentiation. Treatment with MF improved the expression of a brown-fat signature and of mitochondrial-mass-related genes, thus resulting in UCP1 induction. MF also raised the expression of other thermogenic regulators, including peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), PR domain-containing protein 16 (PRDM16), and peroxisome proliferator-activated receptors alpha and gamma (PPAR-α and -γ). MF promoted mitochondrial biogenesis, judging by increased expression of cell death-inducing DNA fragmentation factor α-like effector A (CIDEA), mitochondrial transcription factor A (TFAM), iodothyronine deiodinase 2 (DIO2), cytochrome c oxidase subunit 7A (COX7A), cyclooxygenase 2 (COX2), sirtuin 1 (SIRT1), and nuclear respiratory factor 1 (NRF1). MF treatment increased the mitochondrial DNA amount and improved mitochondrial respiratory function by increasing the oxygen consumption rate during brown-adipocyte differentiation. A gene knockdown assay involving small interfering RNA and competitive inhibition with dorsomorphin revealed that MF may promote thermogenesis in brown preadipocytes via activation of AMPK signaling. Collectively, our findings suggest that MF may be a novel pharmaceutical agent that can ameliorate obesity via activation of brown adipose tissue.

AdipoRon promotes diabetic fracture repair through endochondral ossification-based bone repair by enhancing survival and differentiation of chondrocytes

Diabetic bone defects may exhibit impaired endochondral ossification (ECO) leading to delayed bone repair. AdipoRon, a receptor agonist of adiponectin polymers, can ameliorate diabetes and related complications, as well as overcome the disadvantages of the unstable structure of artificial adiponectin polymers. Here, the effects of AdipoRon on the survival and differentiation of chondrocytes in a diabetic environment were explored focusing on related mechanisms in gene and protein levels. In vivo, AdipoRon was applied to diet-induced-obesity (DIO) mice, a model of obesity and type 2 diabetes, with femoral fracture. Sequential histological evaluations and micro-CT were examined for further verification. We found that AdipoRon could ameliorate cell viability, apoptosis, and reactive oxygen species (ROS) production and promote mRNA expression of chondrogenic markers and cartilaginous matrix production of ATDC5 cells in high glucose medium via activating ERK1/2 pathway. Additionally, DIO mice with intragastric AdipoRon administration had more neocartilage and accelerated new bone formation. These data suggest that AdipoRon could stimulate bone regeneration via ECO in diabetes.

Mangiferin Prevents TBHP-Induced Apoptosis and ECM Degradation in Mouse Osteoarthritic Chondrocytes via Restoring Autophagy and Ameliorates Murine Osteoarthritis

Osteoarthritis (OA) is an age-related degenerative disease with complicated pathology involving chondrocyte apoptosis and extracellular matrix (ECM) degradation. Previous studies have shown that moderate autophagy has a protective effect against apoptosis in chondrocyte. Mangiferin is a natural polyphenol and exerts multiple pharmacological effects on different diseases in various preclinical studies. In this study, we investigated the effects of mangiferin on OA and delineated a potential molecular mechanism. In vitro, mangiferin treatment inhibited the expression of proapoptotic proteins induced by tert-butyl hydroperoxide (TBHP), increased the expression of antiapoptotic Bcl-2, and prevented ECM degradation by inhibiting the production of matrix-degrading enzyme. Mechanistically, mangiferin enhanced autophagy by activating the AMP-activated protein kinase (AMPK) signaling pathway. On the contrary, inhibition of autophagy partly abolished the protective effects of mangiferin on antiapoptosis and ECM synthesis in TBHP-treated chondrocyte. Correspondingly, the protective effect of mangiferin was also found in a mouse OA model. In conclusion, our results suggested that mangiferin serves as a potentially applicable candidate for treating OA.

Dasatinib Promotes Chondrogenic Differentiation of Human Mesenchymal Stem Cells via the Src/Hippo-YAP Signaling Pathway

Mesenchymal stem cells (MSCs) are progenitors of chondrocytes and could be used as a potential therapy for cartilage defects in diarthrodial joints. However, promoting chondrogenic differentiation of MSCs remains a daunting challenge. As a small molecular drug, dasatinib can promote MSC differentiation, although the exact mechanisms of chondrogenic differentiation are unclear. In this study, the differentiation of MSCs into osteoblasts, adipocytes, and chondrocytes was assessed by the protein and mRNA levels of osteoblast- and chondrocyte-related proteins using western blotting and real-time polymerase chain reaction, respectively. MSCs were induced to differentiate into chondrocytes or osteoblasts with or without dasatinib in vitro. The effects of dasatinib on cartilage regeneration were also assessed in vivo in a rabbit model of full-thickness cartilage defects using methacrylate gelatin hydrogel as scaffolds. Dasatinib promoted chondrogenic differentiation and inhibited osteogenic differentiation of MSCs. Furthermore, dasatinib significantly inhibited the expression of YAP and TAZ and the phosphorylation of Src, but it enhanced serine phosphorylation of YAP during the chondrogenic differentiation of MSCs in vitro. Inhibition of the Hippo pathway using XMU-MP-1 dramatically suppressed the serine phosphorylation of YAP and chondrogenic differentiation of MSCs. Moreover, we confirmed that the sustained release of dasatinib from the hydrogel promoted rabbit cartilage repair. The results demonstrated that dasatinib might promote chondrogenic differentiation of MSCs via the Src/Hippo-YAP signaling pathway and that hydrogel sustained-release dasatinib had a certain effect on the repair of cartilage defects.

STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy

Schwann cells are the main supportive cells of the peripheral nerves. Schwann cells suffer inhibition of autophagy under hyperglycemia treatment in diabetic peripheral neuropathy (DPN). However, the exact mechanism is still not fully elucidated. We first observed the decrease of autophagy markers (LC3-II/LC3-I, P62) in the sciatic nerves of diabetic mice vs. normal mice, accompanied with the loss of myelinated nerve fibers and abnormal myelin sheath. In line with this, LC3-II/LC3-I and P62 were also significantly reduced in high glucose-treated rat Schwann cell 96 (RSC96) cells compared with normal glucose-treated cells. Furthermore, we found that trichostatin A [an inhibitor of histone deacetylase (HDAC)] evidently improved LC3-II/LC3-I in high glucose-treated RSC96 cells, without an effect on P62 expression. Again, HDAC1 and HDAC5 were revealed to be increased in RSC96 cells stimulated with high glucose. Inhibition of HDAC1 but not HDAC5 by small hairpin RNA vector enhanced LC3-II/LC3-I in high glucose-cultured RSC96 cells. In addition, LC3-II conversion regulators [autophagy-related protein (Atg)3, Atg5, and Atg7] were detected in high glucose-treated and HDAC1-knockdown RSC96 cells, and Atg3 was proven to be the key target of HDAC1. The presuppression of Atg3 offset the improvement of LC3-II/LC3-I resulting from HDAC1 inhibition in high glucose-treated RSC96 cells. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway was activated in RSC96 cells treated with high glucose, which was indicated by increased STAT3 phosphorylation. Blocking STAT3 phosphorylation by chemical inhibitor AG490 induced HDAC1 down-regulation followed by increases in Atg3 and LC3-II/LC3-I. Interestingly, we also found that AG490 treatment enhanced P62 expression in high glucose-stimulated RSC96 cells. Taken together, our findings demonstrate that hyperglycemia inhibits LC3-II/LC3-I in an HDAC1-Atg3-dependent manner and decreases P62 expression in an HDAC-independent manner via the JAK-STAT3 signaling pathway in the Schwann cells of DPN.-Du, W., Wang, N., Li, F. Jia, K., An, J., Liu, Y., Wang, Y., Zhu, L., Zhao, S. Hao, J. STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy.

Ceria nanoparticles enhance endochondral ossification-based critical-sized bone defect regeneration by promoting the hypertrophic differentiation of BMSCs via DHX15 activation

Central ischemic necrosis is one of the biggest obstacles in the clinical application of traditional tissue-engineered bone (TEB) in critical-sized bone defect regeneration. Because of its ability to promote vascular invasion, endochondral ossification-based TEB has been applied for bone defect regeneration. However, inadequate chondrocyte hypertrophy can hinder vascular invasion and matrix mineralization during endochondral ossification. In light of recent studies suggesting that ceria nanoparticles (CNPs) improve the blood vessel distribution within TEB, we modified TEB scaffold surfaces with CNPs and investigated the effect and mechanism of CNPs on endochondral ossification-based bone regeneration. The CNPs used in this study were synthesized by the microemulsion method and modified with alendronate-anchored polyethylene glycol 600. We showed that CNPs accelerated new bone formation and enhanced endochondral ossification-based bone regeneration in both a subcutaneous ectopic osteogenesis model and a mouse model of critical-sized bone defects. Mechanistically, CNPs significantly promoted endochondral ossification-based bone regeneration by ensuring sufficient hypertrophic differentiation via the activation of the RNA helicase, DEAH (Asp-Glu-Ala-His) box helicase 15, and its downstream target, p38 MAPK. These results suggested that CNPs could be applied as a biomaterial to improve the efficacy of endochondral ossification-based bone regeneration in critical-sized bone defects.-Li, J., Kang, F., Gong, X., Bai, Y., Dai, J., Zhao, C., Dou, C., Cao, Z., Liang, M., Dong, R., Jiang, H., Yang, X., Dong, S. Ceria nanoparticles enhance endochondral ossification-based critical-sized bone defect regeneration by promoting the hypertrophic differentiation of BMSCs via DHX15 activation.