Exosomes derived from human platelet-rich plasma prevent apoptosis induced by glucocorticoid-associated endoplasmic reticulum stress in rat osteonecrosis of the femoral head via the Akt/Bad/Bcl-2 signal pathway

An Ultrashort Peptide-Based Supramolecular Hydrogel Mimicking IGF-1 to Alleviate Glucocorticoid-Induced Sarcopenia

Sarcopenia is a common disease in older people due to aging, and it can also occur in midlife because of diseases including cancer. Sarcopenia, characterized by rapid loss of muscle mass and accelerated loss of function, can lead to adverse outcomes such as frailty, falls, and even mortality. The development of pharmacological and therapeutic approaches to treat sarcopenia remains challenging. The growth status and quantity of myoblasts are the key factors directly affecting muscle formation. Therefore, enhancing the function of myoblasts is crucial for the treatment of sarcopenia. In our study, we introduced an insulin-like growth factor-I (IGF-1) mimicking supramolecular nanofibers/hydrogel formed by Nap-FFGSSSR that effectively promoted proliferation and significantly reduced dexamethasone-induced apoptosis of myoblasts, assisted myoblasts to differentiate into myotubes, and prevented the fibrosis of muscle tissue and the deposition of collagen, ultimately achieving outstanding effects in the treatment of sarcopenia. The RNA-sequencing results revealed that our nanofibers possessed similar bioactivity to the growth factor IGF-1, which increased the phosphorylation of Akt by activating the insulin signaling pathway. We prepared novel supramolecular nanomaterials to reverse glucocorticoid-induced myoblast dysfunction, which was promising for the treatment of muscular atrophy. In addition, we envisioned the generation of biofunctional nanomaterials by molecular self-assembly for the treatment of chronic diseases in middle-aged and older people.

Metabonomic study of the intervention effects of Parthenolide on anti-thyroid cancer activity

Thyroid cancer is the most common endocrine malignant tumor in the world, and its incidence is increasing. Although the mortality rate of thyroid cancer is low, its persistence/recurrence rate is high. In addition, some patients with thyroid cancer fail to respond to radiation. Therefore, it is urgent need to develop a novel treatment for thyroid cancer. Parthenolide (PTL), a traditional Chinese medicine Tanacetum parthenium extract, has shown encouraging effects in anti-tumor, anti-inflammatory and anti-malaria. However, it is unclear whether PTL has an anti-thyroid cancer effect and its possible mechanism of action. In the recent years, metabonomics has been widely used in tumors research to explore the pharmacological mechanism of drugs, but few studies used metabonomics to investigate the pharmacological effects of PTL in thyroid tumors. In order to comprehensively reveal the mechanism and effects of PTL on anti-thyroid tumors, metabonomics combined cell biological research methods were conducted. The results showed that PTL promote apoptosis of thyroid cancer cells (TPC-1) in a concentration-dependent manner. The metabolic differences between the PTL group and the control group were compared by metabonomics, and 31 potential metabolites were identified. These metabolites were mainly involved in the tricarboxylic acid cycle, amino acid metabolism, choline metabolism and lipid metabolism. These results implied that PTL may inhibit the proliferation and development of thyroid carcinoma by accelerating oxidation emergency response, inhibiting adenosine triphosphate (ATP) synthesis and metabolic imbalance. The results of this study revealed that PTL can be an effective and potential drug for the treatment of thyroid cancer.

Extracellular vesicles isolated from human olfactory ensheathing cells enhance the viability of neural progenitor cells

OBJECTIVE

Acquired neurological diseases such as severe traumatic brain or spinal cord injury (SCI) cause irreversible disability. Olfactory ensheathing cell (OEC) transplantation has been trialed as a promising SCI treatment. Extracellular vesicles (EVs), which regulate cell-cell interactions, have recently garnered extensive research interests and emerged as a non-cell-based therapy in neurological disorders, including in SCI animal models. However, there have been no reports of human OEC-EVs and their beneficial effects on neuron regeneration. Here, we investigated the effects of EVs isolated from human OEC on the viability of neuronal cells.

METHODS

EVs were isolated from primary human OECs (hOECs) by serial ultracentrifugation. The hOEC-EVs were characterized by transmission electron microscopy, western blotting, and nanoparticle tracking analyses. We conducted CCK8 and lactate dehydrogenase assays to assess the cell proliferation and cytotoxicity of neural progenitor cells (NPCs) exposed to hOEC-EVs. Tert-butyl hydroperoxide (t-BHP) was utilized to mimic oxidative stress-induced cytotoxicity in NPCs.

RESULTS

The modal diameter of hOEC-derived EVs was 113.2 nm. Expressions of EV markers such as CD9, CD63, and CD81 were detected by western blotting. hOEC-derived EVs enhanced the proliferation of NPCs and ameliorated cell cytotoxicity mediated by t-BHP.

DISCUSSION

Our findings reveal a role for hOEC-derived EVs in NPC proliferation and oxidative stress-induced neuronal toxicity model. These results may be useful for developing non-cell therapy OEC-EV-based treatment in acquired nervous system disease.

Extracellular vesicles from human urine-derived stem cells inhibit glucocorticoid-induced osteonecrosis of the femoral head by transporting and releasing pro-angiogenic DMBT1 and anti-apoptotic TIMP1

Osteonecrosis of the femoral head (ONFH) frequently occurs after glucocorticoid (GC) treatment. Extracellular vesicles (EVs) are important nano-sized paracrine mediators of intercellular crosstalk. This study aimed to determine whether EVs from human urine-derived stem cells (USC-EVs) could protect against GC-induced ONFH and focused on the impacts of USC-EVs on angiogenesis and apoptosis to explore the mechanism by which USC-EVs attenuated GC-induced ONFH. The results in vivo showed that the intravenous administration of USC-EVs at the early stage of GC exposure could rescue angiogenesis impairment, reduce apoptosis of trabecular bone and marrow cells, prevent trabecular bone destruction and improve bone microarchitecture in the femoral heads of rats. In vitro, USC-EVs reversed the GC-induced suppression of endothelial angiogenesis and activation of apoptosis. Deleted in malignant brain tumors 1 (DMBT1) and tissue inhibitor of metalloproteinases 1 (TIMP1) proteins were enriched in USC-EVs and essential for the USC-EVs-induced pro-angiogenic and anti-apoptotic effects in GC-treated cells, respectively. Knockdown of TIMP1 attenuated the protective effects of USC-EVs against GC-induced ONFH. Our study suggests that USC-EVs are a promising nano-sized agent for the prevention of GC-induced ONFH by delivering pro-angiogenic DMBT1 and anti-apoptotic TIMP1. STATEMENT OF SIGNIFICANCE: This study demonstrates that the intravenous injection of extracellular vesicles from human urine-derived stem cells (USC-EVs) at the early stage of glucocorticoid (GC) exposure efficiently protects the rats from the GC-induced osteonecrosis of the femoral head (ONFH). Moreover, this study identifies that the promotion of angiogenesis and inhibition of apoptosis by transferring pro-angiogenic DMBT1 and anti-apoptotic TIMP1 proteins contribute importantly to the USC-EVs-induced protective effects against GC-induced ONFH. This study suggests the promising prospect of USC-EVs as a new nano-sized agent for protecting against GC-induced ONFH, and the potential of DMBT1 and TIMP1 as the molecular targets for further augmenting the protective function of USC-EVs.

Mediating effects of platelet-derived extracellular vesicles on PM2.5-induced vascular endothelial injury

At present, PM_2.5 exposure has been considered as a major risk factor for cardiovascular disease. Most studies have focused on the toxic mechanism of PM_2.5 in direct contact with cells or biomolecules, only few studies have reported the toxic mechanism of PM_2.5 mediated by intercellular communication. Extracellular vesicles are the main carriers of intercellular communication and signal transduction in vivo, and play a vital role in the occurrence and development of cardiovascular disease. Therefore, the present research aimed to determine whether platelets-derived extracellular vesicles (P-EVs) secreted from PM_2.5-exposed platelets are transferred into the human umbilical vein endothelial cells (HUVECs) and mediated the PM_2.5-induced vascular endothelial injury by affecting normal cellular function. The result showed that P-EVs secreted from PM_2.5-exposed platelets significantly reduced the proliferation promoting effect of normal P-EVs on vascular endothelium by decreasing the effective factors promoting vascular endothelial growth. Meanwhile, the levels of intercellular adhesion molecules, proinflammatory factors (ICAM-1, IL-6, and TNF-α) and the ROS level of HUVECs were markedly elevated. In addition, the apoptotic rate was increased via up-regulating the protein level of cytochrome-C(Cyt C), Bax, cleaved caspase-3 and down-regulating Bcl-2 in HUVECs, indicating that mitochondrial apoptotic pathway was activated by P-EVs secreted from PM_2.5-exposed platelets. Further, the expression level of P-EVs targeted miRNAs in HUVECs was altered, indicating that miRNAs released from P-EVs were transferred to HUVECs and regulated the cellular function, while PM_2.5 could inhibit this regulatory effect. In summary, these results demonstrate that the P-EVs secreted from PM_2.5-exposed platelets can enter the HUVECs, which mediate the PM_2.5-induced vascular endothelial injury. These findings provide a new perspective and theoretical basis for further exploring the mechanism of cardiovascular damage caused by PM_2.5 exposure.

BMSC-derived exosomes alleviate smoke inhalation lung injury through blockade of the HMGB1/NF-κB pathway

AIMS

To investigate the role of bone marrow mesenchymal stem cell (BMSC)-derived exosomes in smoke inhalation lung injury.

MAIN METHODS

In this study, we initially isolated exosomes from BMSCs and identified them by western blot and transmission electron microscopy. BMSC-derived exosomes were then used to treat in vitro and in vivo models of smoke inhalation lung injury. Pathologic alterations in lung tissue, the levels of inflammatory factors and apoptosis-related factors, and the expression of HMGB1 and NF-κB were determined to evaluate the therapeutic effect of BMSC-derived exosomes.

KEY FINDINGS

We found that BMSC-derived exosomes could alleviate the injury caused by smoke inhalation. Smoke inhalation increased the levels of inflammatory factors and apoptosis-related factors and the expression of HMGB1 and NF-κB, and these increases were reversed by BMSC-derived exosomes. HMGB1 overexpression abrogated the exosome-induced decreases in inflammatory factors, apoptosis-related factors and NF-κB.

SIGNIFICANCE

Collectively, these results indicate that BMSC-derived exosomes can effectively alleviate smoke inhalation lung injury by inhibiting the HMGB1/NF-κB pathway, suggesting that exosome, a noncellular therapy, is a potential therapeutic strategy for inhalation lung injury.

Exosomes Isolated From Platelet-Rich Plasma and Mesenchymal Stem Cells Promote Recovery of Function After Muscle Injury

BACKGROUND

Clinical use of platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) has gained momentum as treatment for muscle injuries. Exosomes, or small cell-derived vesicles, could be helpful if they could deliver the same or better physiological effect without cell transplantation into the muscle.

HYPOTHESIS

Local delivery of exosomes derived from PRP (PRP-exos) or MSCs (MSC-exos) to injured muscles hastens recovery of contractile function.

STUDY DESIGN

Controlled laboratory study.

METHODS

In a rat model, platelets were isolated from blood, and MSCs were isolated from bone marrow and expanded in culture; exosomes from both were isolated through ultracentrifugation. The tibialis anterior muscles were injured in vivo using maximal lengthening contractions. Muscles were injected with PRP-exos or MSC-exos (immediately after injury and 5 and 10 days after injury); controls received an equal volume of saline. Histological and biochemical analysis was performed on tissues for all groups.

RESULTS

Injury resulted in a significant loss of maximal isometric torque (66% ± 3%) that gradually recovered over 2 weeks. Both PRP-exos and MSC-exos accelerated recovery, with similar faster recovery of contractile function over the saline-treated group at 5, 10, and 15 days after injury (P < .001). A significant increase in centrally nucleated fibers was seen with both types of exosome groups by day 15 (P < .01). Genes involved in skeletal muscle regeneration were modulated by different exosomes. Muscles treated with PRP-exos had increased expression of Myogenin gene (P < .05), whereas muscles treated with MSC-exos had reduced expression of TGF-β (P < .05) at 10 days after muscle injury.

CONCLUSION

Exosomes derived from PRP or MSCs can facilitate recovery after a muscle strain injury in a small-animal model likely because of factors that can modulate inflammation, fibrosis, and myogenesis.

CLINICAL RELEVANCE

Given their small size, low immunogenicity, and ease with which they can be obtained, exosomes could represent a novel therapy for many orthopaedic ailments.

Ryanodine receptor 1 mediated dexamethasone-induced chondrodysplasia in fetal rats

BACKGROUND

Osteoarthritis is caused by cartilage dysplasia and has fetal origin. Prenatal dexamethasone exposure (PDE) induced chondrodysplasia in fetal rats by inhibiting transforming growth factor β (TGFβ) signaling. This study aimed to determine the effect of dexamethasone on fetal cartilage development and illustrate the underlying molecular mechanism.

METHODS

Dexamethasone (0.2 mg/kg.d) was injected subcutaneously every morning in pregnant rats from gestational day (GD) 9 to GD21. Harvested fetal femurs and tibias at GD21 for immunofluorescence and gene expression analysis. Fetal chondrocytes were treated with dexamethasone (100, 250 and 500 nM), endoplasmic reticulum stress (ERS) inhibitor, and ryanodine receptor 1 (RYR1) antagonist for subsequent analyses.

RESULTS

In vivo, prenatal dexamethasone exposure (PDE) decreased the total length of the fetal cartilage, the proportion of the proliferation area and the cell density and matrix content in fetal articular cartilage. Moreover, PDE increased RYR1 expression and intracellular calcium levels and elevated the expression of ERS-related genes, while downregulated the TGFβ signaling pathway and extracellular matrix (ECM) synthesis in fetal chondrocytes. In vitro, we verified dexamethasone significantly decreased ECM synthesis through activating RYR 1 mediated-ERS.

CONCLUSIONS

PDE inhibited TGFβ signaling pathway and matrix synthesis through RYR1 / intracellular calcium mediated ERS, which ultimately led to fetal dysplasia. This study confirmed the molecular mechanism of ERS involved in the developmental toxicity of dexamethasone and suggested that RYR1 may be an early intervention target for fetal-derived adult osteoarthritis.

Magnetic Targeting of HU-MSCs in the Treatment of Glucocorticoid-Associated Osteonecrosis of the Femoral Head Through Akt/Bcl2/Bad/Caspase-3 Pathway

Purpose

Osteonecrosis of the femoral head (ONFH) is a chronic and irreversible disease that eventually develops into a joint collapse and results in joint dysfunction. Early intervention and treatment are essential for preserving the joints and avoiding hip replacement. In this study, a system of human umbilical mesenchymal stem cells-supermagnetic iron oxide nanoparticles (NPs) @polydopamine (SCIOPs) was constructed. The magnetic targeting system gathers in the lesion area, inhibits the apoptosis of bone cells, enhances osteogenic effect, and effectively treats ONFH under external magnetic field.

Materials and Methods

The supermagnetic iron oxide NPs @polydopamine (SPION@PDA NPs) were characterized by transmission electron microscopy and zeta potential, respectively. The effects of SPION@PDA NPs on the viability, proliferation, and differentiation of stem cells were detected by the CCK8 method, flow cytometry, and staining, respectively. The serum inflammatory indicators were detected by Luminex method. The bone mass of the femoral head was analyzed by micro computed tomography. The expression of apoptosis and osteoblast-related cytokines was detected by Western blotting. The osteogenesis of the femoral head was detected by histological and immunohistochemical sections.

Results

The SCIOPs decreased the pro-inflammatory factors, and the micro CT showed that the bone repair of the femoral head was enhanced after treatment. The hematoxylin and eosin sections also showed an increase in the osteogenesis in the femoral head. Western blotting results showed and increased expression of anti-apoptotic proteins Akt and Bcl-2, decreased expression of apoptotic proteins caspase-3 and Bad, and increased expression of osteogenic proteins Runx-2 and Osterix in the femoral head.

Conclusion

Under the effect of magnetic field and homing ability of stem cells, SCIOPs inhibited the apoptosis of osteoblasts, improved the proliferation ability of osteoblasts, and promoted bone repair in the femoral head through the Akt/Bcl-2/Bad/caspase-3 signaling pathway, thereby optimizing the tissue repair ability.

A Systems Biological Approach to Understanding the Mechanisms Underlying the Therapeutic Potential of Red Ginseng Supplements against Metabolic Diseases

Red ginseng has been widely used in health-promoting supplements in Asia and is becoming increasingly popular in Western countries. However, its therapeutic mechanisms against most diseases have not been clearly elucidated. The aim of the present study was to provide the biological mechanisms of red ginseng against various metabolic diseases. We used a systems biological approach to comprehensively identify the component-target and target-pathway networks in order to explore the mechanisms underlying the therapeutic potential of red ginseng against metabolic diseases. Of the 23 components of red ginseng with target, 5 components were linked with 37 target molecules. Systematic analysis of the constructed networks revealed that these 37 targets were mainly involved in 9 signaling pathways relating to immune cell differentiation and vascular health. These results successfully explained the mechanisms underlying the efficiency of red ginseng for metabolic diseases, such as menopausal symptoms in women, blood circulation, diabetes mellitus, and hyperlipidemia.

Engineered three-dimensional scaffolds for enhanced bone regeneration in osteonecrosis

Osteonecrosis, which is typically induced by trauma, glucocorticoid abuse, or alcoholism, is one of the most severe diseases in clinical orthopedics. Osteonecrosis often leads to joint destruction, and arthroplasty is eventually required. Enhancement of bone regeneration is a critical management strategy employed in osteonecrosis therapy. Bone tissue engineering based on engineered three-dimensional (3D) scaffolds with appropriate architecture and osteoconductive activity, alone or functionalized with bioactive factors, have been developed to enhance bone regeneration in osteonecrosis. In this review, we elaborate on the ideal properties of 3D scaffolds for enhanced bone regeneration in osteonecrosis, including biocompatibility, degradability, porosity, and mechanical performance. In addition, we summarize the development of 3D scaffolds alone or functionalized with bioactive factors for accelerating bone regeneration in osteonecrosis and discuss their prospects for translation to clinical practice.

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Engineered three-dimensional scaffolds boost bone regeneration in osteonecrosis.

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The ideal properties of three-dimensional scaffolds for osteonecrosis treatment are discussed.

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Bioactive factors-functionalized three-dimensional scaffolds are promising bone regeneration devices for osteonecrosis management.

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The challenges and opportunities of engineered three-dimensional scaffolds for osteonecrosis therapy are predicted.

PI3K/Akt signaling pathway is essential for de novo hair follicle regeneration

Background

Cultured epidermal stem cells (Epi-SCs) and skin-derived precursors (SKPs) were capable of reconstituting functional hair follicles after implantation, while the signaling pathways that regulate neogenic hair follicle formation are poorly investigated. In this study, we aimed to understand the interactions between Epi-SCs and SKPs during skin organoid formation and to uncover key signal pathways crucial for de novo hair follicle regeneration.

Methods

To track their fate after transplantation, Epi-SCs derived from neonatal C57BL/6 mice were labeled with tdTomato, and SKPs were isolated from neonatal C57BL/6/GFP mice. A mixture of Epi-SCs-tdTomato and SKPs-EGFP in Matrigel was observed under two-photon microscope in culture and after implantation into excisional wounds in nude mice, to observe dynamic migrations of the cells during hair follicle morphogenesis. Signaling communications between the two cell populations were examined by RNA-Seq analysis. Potential signaling pathways revealed by the analysis were validated by targeting the pathways using specific inhibitors to observe a functional loss in de novo hair follicle formation.

Results

Two-photon microscopy analysis indicated that when Epi-SCs and SKPs were mixed in Matrigel and cultured, they underwent dynamic migrations resulting in the formation of a bilayer skin-like structure (skin organoid), where Epi-SCs positioned themselves in the outer layer; when the mixture of Epi-SCs and SKPs was grafted into excisional wounds in nude mice, a bilayer structure resembling the epidermis and the dermis formed at the 5th day, and de novo hair follicles generated subsequently. RNA-Seq analysis of the two cell types after incubation in mixture revealed dramatic alterations in gene transcriptome, where PI3K-Akt signaling pathway in Epi-SCs was significantly upregulated; meanwhile, elevated expressions of several growth factors and cytokine potentially activating PI3K were found in SKPs, suggesting active reciprocal communications between them. In addition, inhibition of PI3K or Akt by specific inhibitors markedly suppressed the hair follicle regeneration mediated by Epi-SCs and SKPs.

Conclusions

Our data indicate that the PI3K-Akt signaling pathway plays a crucial role in de novo hair follicle regeneration, and the finding may suggest potential therapeutic applications in enhancing hair regeneration.

Exosomes in osteoarthritis and cartilage injury: advanced development and potential therapeutic strategies

Articular cartilage injury is a common clinical problem, which can lead to joint dysfunction, significant pain, and secondary osteoarthritis (OA) in which major surgical procedures are mandatory for treatment. Exosomes, as endosome-derived membrane-bound vesicles, participating in intercellular communications in both physiological and pathophysiological conditions, have been attached great importance in many fields. Recently, the significance of exosomes in the development of OA has been gradually concerned, while the therapeutic value of exosomes in cartilage repair and OA treatment has also been gradually revealed. The functional difference of different types and derivations of exosomes are determined by their specific contents. Herein, we provide comprehensive understanding on exosome and OA, including how exosomes participating in OA, the therapeutic value of exosomes for cartilage injury/OA, and related bioengineering strategies for future therapeutic design.

Dexamethasone causes calcium deposition and degeneration in human anterior cruciate ligament cells through endoplasmic reticulum stress

BACKGROUND

Dexamethasone is widely used in the treatment of joint diseases due to its anti-inflammatory properties. However, it can cause serious adverse effects. The anterior cruciate ligament (ACL) is an important stabilizer of the knee joint. However, the effect of dexamethasone treatment on the ACL is unclear.

OBJECTIVE

This study aims to explore the effects of dexamethasone on ACL tissues and cells through in vitro and in vivo experiments.

RESULTS

In vitro, we found that after treatment with dexamethasone, human ACL cell apoptosis was increased, type I collagen (COL1A1) content was decreased, mineralization related genes (ENPP1 and ANKH) and calcified nodules were increased, and endoplasmic reticulum stress (ERS) was enhanced. However, ERS inhibitors could significantly inhibit the increase in calcification and the decrease in COL1A1 induced by dexamethasone. In vivo, Wistar rats received the infra-articular injection with dexamethasone (0.5 mg/kg) for 8 weeks. We found that dexamethasone treatment decreased the COL1A1 content and increased the COL2A1 content in the ACL tissues of rats and that chondroid differentiation and mineralization occurred. Meanwhile, the expression of ERS-related proteins was increased.

CONCLUSION

Dexamethasone increased the calcification of ACL cells and caused ACL degeneration through ERS, suggesting that long-term treatment with dexamethasone may cause adverse effects on ACL tissue and increase the risk of long-term rupture.

The dual character of exosomes in osteoarthritis: Antagonists and therapeutic agents

Exosomes have gained increasing attention as they participate in cell cross-talk in pathological environments and are functional paracrine factors of therapeutic stem cells. Osteoarthritis (OA) is a common age-related degenerative joint disease, leading to a debilitating lifestyle for sufferers. However, currently no drugs on the market promote cartilage repair, and the patients usually have to undergo arthroplasty in the late stage of OA. Although significant progress has been made in the development of stem cells for the treatment of OA and cartilage injury, problems like immune rejection remain. Recently, increasing evidence has demonstrated that exosomes from the joint microenvironment ("negative" exosomes) could play vital and complicated roles in the progression of OA. Moreover, exosomes from therapeutic cells ("therapeutic" exosomes) have also shown enormous potential for OA therapy/cartilage repair. Here, we first discuss the definition and biological background of exosomes. Then, we critically examine the roles of the "negative" exosomes in OA-affected joint. Then, we will cover the potential of the "therapeutic" exosomes for OA therapy/cartilage repair. Next, the recent progress of tissue engineering with exosomes, especially for OA therapy/cartilage repair, will also be discussed. Finally, the limitations and opportunities of exosome-based OA therapy will be outlined. STATEMENT OF SIGNIFICANCE: As natural extracellular vesicles, exosomes participate in the intercellular communication. On the basis of biological characteristics of exosomes, exosomes have their two sides for osteoarthritis (OA). On the one hand, exosomes in the OA microenvironment are involved in pathology of OA. On the other hand, exosomes from therapeutic cells have the potential as advanced strategies for OA therapy. In addition, the development of tissue engineering technology is beneficial to the exosome-based OA therapy. According to the latest research status, exosomes are of great significance and interest for the personalized and precision treatment of OA in the future, despite the limitations and challenges.

The Use of Platelet-Rich Plasma for the Treatment of Osteonecrosis of the Femoral Head: A Systematic Review

Background

As a pathological process, osteonecrosis of the femoral head (ONFH) is characterized by the avascularity of the femoral head, cellular necrosis, microfracture, and the collapse of the articular surface. Currently, critical treatment for early-stage ONFH is limited to core decompression. However, the efficacy of core decompression remains controversial. To improve the core decompression efficacy, regenerative techniques such as the use of platelet-rich plasma (PRP) were proposed for early-stage ONFH. As a type of autologous plasma containing concentrations of platelets greater than the baseline, PRP plays an important role in tissue repair, regeneration, and the differentiation of mesenchymal stem cells (MSCs). In this review, we present a comprehensive overview of the operation modes, mechanism, and efficacy of PRP for early-stage ONFH treatment.

Methods

We searched for relevant studies in the PubMed, Web of Science, and Embase databases. By searching these electronic databases, the identification of either clinical or experimental studies evaluating PRP, MSC, core decompression, and ONFH was our goal.

Results

Seventeen studies of PRP and avascular necrosis of the femoral head were evaluated in our review. Ten studies related to the possible mechanism of PRP for treating ONFH were reviewed. Seven studies of the operation modes of PRP in treating ONFH were identified. We reviewed the efficacy of PRP in treating ONFH systematically and made an attempt to compare the PRP operation modes in 7 studies and other operation modes in past studies for early-stage ONFH treatment.

Conclusion

PRP treats ONFH mainly through three mechanisms: inducing angiogenesis and osteogenesis to accelerate bone healing, inhibiting inflammatory reactions in necrotic lesions, and preventing apoptosis induced by glucocorticoids. In addition, as an adjunctive therapy for core decompression, the use of PRP is recommended to improve the treatment of early-stage ONFH patients, especially when combined with stem cells and bone grafts, by inducing osteogenic activity and stimulating the differentiation of stem cells in necrotic lesions.

Exosomes derived from platelet-rich plasma activate YAP and promote the fibrogenic activity of Müller cells via the PI3K/Akt pathway

The purpose of this study was to investigate the role of exosomes derived from platelet-rich plasma (PRP-Exos) in the regulation of the fibrogenic activity of Müller cells and the underlying mechanism. We studied the effects of PRP-Exos on the fibrogenic activity of human retinal Müller cells (hMCs) in vitro. PRP-Exos were isolated from the plasma of diabetic rats (DM-PRP-Exos) and normal control rats (Nor-PRP-Exos) and then observed by transmission electron microscopy. After treatment with DM-PRP-Exos or Nor-PRP-Exos, the proliferation and migration of hMCs were measured in vitro. Western blotting was conducted to assess the levels of fibrogenic molecules and activation of Yes-associated protein (YAP) and the PI3K-Akt signalling pathway. In cultured hMCs, DM-PRP-Exos but not Nor-PRP-Exos effectively increased the proliferative and migratory activities and improved connective tissue growth factor (CTGF) and fibronectin expression. Genetic and pharmacological suppression of YAP could reduce the proliferative and migratory activities of hMCs induced by DM-PRP-Exo. Additionally, YAP knockdown inhibited the DM-PRP-Exo-induced up-regulation of CTGF and fibronectin. Furthermore, DM-PRP-Exo-induced PI3K-Akt signalling mediated YAP activation and the expression of CTGF and fibronectin. In summary, DM-PRP-Exos, through YAP activation, enhance both the proliferation and fibrogenic activity of Müller cells via the PI3K/Akt pathway.

Hypoxic mesenchymal stem cell-derived exosomes promote bone fracture healing by the transfer of miR-126

Increasing evidence has suggested that paracrine mechanisms might be involved in the underlying mechanism of mesenchymal stem cells (MSCs) transplantation, and exosomes are an important component of this paracrine role. However, MSCs are usually exposed to normoxia (21% O₂) in vitro but experience large differences in oxygen concentration in the body under hypoxia. Indeed, hypoxic precondition of MSCs can enhance their paracrine effects. The main purpose of this study was to determine whether exosomes derived from MSCs under hypoxia (Hypo-Exos) exhibit greater effects on bone fracture healing than those under normoxia (Exos). Using in vivo bone fracture model and in vitro experiments including cell proliferation assay, cell migration assay and so on, we confirmed that Hypo-Exos administration promoted angiogenesis, proliferation and migration to a greater extent when compared to Exos. Furthermore, utilizing a series in vitro and in vivo gain and loss of function experiments, we confirmed a functional role for exosomal miR-126 in the process of bone fracture healing. Meanwhile, we found that knockdown of hypoxia inducible factor 1 (HIF-1α) resulted in a significant decrease of miR-126 in MSCs and exosomes, thereby abolishing the effects of Hypo-Exos. In conclusion, our results demonstrated a mechanism by which Hypo-Exos promote bone fracture healing through exosomal miR-126. Moreover, hypoxia preconditioning mediated enhanced production of exosomal miR-126 through the activation of HIF-1α. Hypoxia preconditioning represents an effective and promising method for the optimization of the therapeutic actions of MSC-derived exosomes for bone fracture healing. STATEMENT OF SIGNIFICANCE: Studies have confirmed that transplantation of exosomes exhibit similar therapeutic effects and functional properties to directly-transplanted stem cells but have less significant adverse effects. However, during in vitro culture conditions, MSCs are usually exposed to normoxia (21% O₂) which is very different to the oxygen concentrations found in the body under natural physiological conditions. Our results demonstrated a mechanism by which Hypo-Exos promote bone fracture healing through exosomal miR-126 and the SPRED1/Ras/Erk signaling pathway. Moreover, hypoxia preconditioning mediated enhanced production of exosomal miR-126 through the activation of HIF-1α. Hypoxia preconditioning represents an effective and promising method for the optimization of the therapeutic actions of MSC-derived exosomes for bone fracture healing.

Identification of potential miRNA biomarkers for traumatic osteonecrosis of femoral head

Traumatic osteonecrosis of femoral head (TONFH) is a common orthopedic disease caused by physical injury in hip. However, the unclear pathogenesis mechanism of TONFH and lacking of simple noninvasive early diagnosis method cause the necessity of hip replacement for most patients with TONFH. In this study, we aimed to identify circulating microRNAs (miRNAs) by integrated bioinformatics analyses as potential biomarker of TONFH. mRNA expression profiles were downloaded from the Gene Expression Omnibus database. Then we combined two miRNA screen methods: Weighted gene co-expression network analysis and fold change based differentially expressed miRNAs analysis. As a result, we identified 14 key miRNAs as potential biomarkers for TONFH. Besides, 302 target genes of these miRNAs were obtained and the miRNA-mRNA interaction network was constructed. Furthermore, the results of Kyoto Encyclopedia of Gene and Genome pathway analysis, Gene Ontology function analysis, protein-protein interaction (PPI) network analysis and PPI network module analysis showed close correlation between these 14 key miRNAs and TONFH. Then we established receiver operating characteristic curves and identified 6-miRNA signature with highly diagnosis value including miR-93-5p (area under the curve [AUC] = 0.93), miR-1324 (AUC = 0.92), miR-4666a-3p (AUC = 0.92), miR-5011-3p (AUC = 0.92), and miR-320a (AUC = 0.89), miR-185-5p (AUC = 0.89). Finally, the results of quantitative real-time polymerase chain reaction confirmed the significantly higher expression of miR-93-5p and miR-320a in the serum of patients with ONFH. These circulating miRNAs could serve as candidate early diagnosis markers and potential treatment targets of TONFH.

Human umbilical cord mesenchymal stromal cells-derived extracellular vesicles exert potent bone protective effects by CLEC11A-mediated regulation of bone metabolism

Osteoporosis and osteoporotic fractures severely compromise quality of life in elderly people and lead to early death. Human umbilical cord mesenchymal stromal cell (MSC)-derived extracellular vesicles (hucMSC-EVs) possess considerable therapeutic effects in tissue repair and regeneration. Thus, in the present study, we investigated the effects of hucMSC-EVs on primary and secondary osteoporosis and explored the underlying mechanisms.

Methods: hucMSCs were isolated and cultured. EVs were obtained from the conditioned medium of hucMSCs and determined by using transmission electron microscopy, dynamic light scattering and Western Blot analyses. The effects of hucMSC-EVs on ovariectomy-induced postmenopausal osteoporosis and tail suspension-induced hindlimb disuse osteoporosis in mouse models were assessed by using microcomputed tomography, biomechanical, histochemical and immunohistochemical, as well as histomorphometric analyses. Proteomic analysis was applied between hucMSC-EVs and hucMSCs to screen the candidate proteins that mediate hucMSC-EVs function. The effects of hucMSC-EVs on osteogenic and adipogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs), and osteoclastogenesis of the macrophage cell line RAW264.7 in vitro were determined by using cytochemical staining and quantitative real-time PCR analysis. Subsequently, the roles of the key protein in hucMSC-EVs-induced regulation on BMSCs and RAW264.7 cells were evaluated.

Results: hucMSCs were able to differentiate into osteoblasts, adipocytes or chondrocytes and positively expressed CD29, CD44, CD73 and CD90, but negatively expressed CD34 and CD45. The morphological assessment revealed the typical cup- or sphere-shaped morphology of hucMSC-EVs with diameters predominantly ranging from 60 nm to 150 nm and expressed CD9, CD63, CD81 and TSG101. The systemic administration of hucMSC-EVs prevented bone loss and maintained bone strength in osteoporotic mice by enhancing bone formation, reducing marrow fat accumulation and decreasing bone resorption. Proteomic analysis showed that the potently pro-osteogenic protein, CLEC11A (C-type lectin domain family 11, member A) was very highly enriched in hucMSC-EVs. In addition, hucMSC-EVs enhanced the shift from adipogenic to osteogenic differentiation of BMSCs via delivering CLEC11A in vitro. Moreover, CLEC11A was required for the inhibitory effects of hucMSC-EVs on osteoclast formation.

Conclusion: Our results suggest that hucMSC-EVs serve as a critical regulator of bone metabolism by transferring CLEC11A and may represent a potential agent for prevention and treatment of osteoporosis.

Silencing MicroRNA-137-3p, which Targets RUNX2 and CXCL12 Prevents Steroid-induced Osteonecrosis of the Femoral Head by Facilitating Osteogenesis and Angiogenesis

The main pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH) includes decreased osteogenic capacity of bone marrow-derived mesenchymal stem cells (BMSCs) and damaged blood supply to the femoral head. MicroRNAs (miRNAs) have been shown to play prominent roles in SONFH development. However, there is no report that a specific miRNA targeting two genes in two different pathogenic pathways has been applied to this disease. The present study investigated the effects of transplantation of miR-137-3p-silenced BMSCs on the prevention and early treatment of SONFH. First, western blotting and dual luciferase assays were employed to verify that miR-137-3p directly targets Runx2 and CXCL12. Then, silencing of miR-137-3p was found to facilitate osteogenic differentiation of BMSCs, which was confirmed by alkaline phosphatase (ALP) staining, alizarin red staining and qRT-PCR. Silencing of miR-137-3p also promoted angiogenesis by human umbilical vein endothelial cells (HUVECs) in the presence or absence of glucocorticoids. Thereafter, overexpression of Runx2 and CXCL12 without the 3′ untranslated region (3′UTR) partially rescued the effects of miR-137-3p on osteogenesis and angiogenesis, respectively. This finding further supported the hypothesis that miR-137-3p exerts its functions partly by regulating the genes, Runx2 and CXCL12. We also demonstrated that SONFH was partially prevented by transplantation of miR-137-3p-silenced BMSCs into a rat model. Micro-CT and histology showed that the transplantation of miR-137-3p-silenced BMSCs significantly improved bone regeneration. Additionally, the results of enzyme-linked immunosorbent assays (ELISA) and flow cytometry suggested that stromal cell-derived factor-1α (SDF-1α) and endothelial progenitor cells (EPCs) participated in the process of vascular repair. Taken together, these findings show that silencing of miR-137-3p directly targets the genes, Runx2 and CXCL12, which can play critical roles in SONFH repair by facilitating osteogenic differentiation and mobilizing EPCs.

Type H blood vessels in bone modeling and remodeling

In the mammalian skeletal system, osteogenesis and angiogenesis are intimately linked during bone growth and regeneration in bone modeling and during bone homeostasis in bone remodeling. Recent studies have expanded our knowledge about the molecular and cellular mechanisms responsible for coupling angiogenesis and bone formation. Type H vessels, termed such because of high expression of Endomucin (Emcn) and CD31, have recently been identified and have the ability to induce bone formation. Factors including platelet-derived growth factor type BB (PDGF-BB), slit guidance ligand 3 (SLIT3), hypoxia-inducible factor 1-alpha (HIF-1α), Notch, and vascular endothelial growth factor (VEGF) are involved in the coupling of angiogenesis and osteogenesis. This review summarizes the current understanding of signaling pathways that regulate type H vessels and how type H vessels modulate osteogenesis. Further studies dissecting the regulation and function of type H vessels will provide new insights into the role of bone vasculature in the metabolism of the skeleton. We also discuss considerations for therapeutic approaches targeting type H vessels to promote fracture healing, prevent pathological bone loss, osteonecrosis, osteoarthritis, and bone metastases.

Exosomes derived from platelet-rich plasma present a novel potential in alleviating knee osteoarthritis by promoting proliferation and inhibiting apoptosis of chondrocyte via Wnt/β-catenin signaling pathway

Background

Platelet-rich plasma (PRP) provides a nonsurgical approach for treating osteoarthritis (OA). Exosomes that play vital roles in intercellular communication have been studied extensively. Here, we investigated the therapeutic potential and molecular mechanism of exosomes derived from PRP (PRP-Exos) in alleviating OA.

Methods

Exosomes derived from PRP(PRP-Exos) were isolated and purified using the exoEasy Maxi Kit and then identified and analyzed. Primary rabbit chondrocytes were isolated and treated with interleukin 1 beta (IL-1β) to establish the OA model in vitro. Proliferation, migration, and apoptosis assays were measured and compared between PRP-Exos and activated PRP (PRP-As) to evaluate the therapeutic effects on OA. The mechanism involving the Wnt/β-catenin signaling pathway was investigated by Western blot analysis. In vivo, we established animal knee OA model by surgery to compare the therapeutic effect of PRP-Exos and PRP-As.

Results

We successfully isolated and purified exosomes from PRP using the exoEasy Maxi Kit. We also isolated and identified chondrocytes from the New Zealand white rabbit and established the IL-1β-induced OA model; meanwhile, PRP-Exos and PRP-As both inhibited the release of tumor necrosis factor-α(TNF-α) and there was no statistically significant difference between the two. In proliferation, migration, scratch assay, the promoting effect of PRP-Exos was significantly more better than PRP-As. Furthermore, PRP-Exos could significantly decreased apoptotic rate of OA chondrocyte compared with PRP-As. In Western blot analysis, the expression of β-catenin, and RUNX2, Wnt5a were increased in IL-1β-treated chondrocytes, but PRP-Exos and PRP-As could both reverse these changes, and the reversal effect of the former was better than the latter. In vivo, we found that both PRP-Exos and PRP-As displayed the progression of OA, and the effect of PRP-Exos was obviously better than PRP-As by chondrocyte count and Osteoarthritis Research Society International (OARSI) scoring system.

Conclusion

The therapeutic effects of PRP-Exos on OA were similar or better compared with those of PRP-As in vitro or in vivo. PRP-Exos acting as carriers containing growth factors derived from PRP present a novel therapy for OA by activating the Wnt/β-catenin signaling pathway.

Exosomes derived from human CD34+ stem cells transfected with miR-26a prevent glucocorticoid-induced osteonecrosis of the femoral head by promoting angiogenesis and osteogenesis

Background

Damaged endothelial cells and downregulated osteogenic ability are two key pathogenic mechanisms of glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH). Recent studies suggested that transplantation of CD34⁺ stem cell-derived exosomes (CD34⁺-Exos) can treat ischemic diseases by promoting neovascularization and that miR-26a is an important positive regulator of osteogenesis. Moreover, the biological effect of exosomes is closely related to their cargo miRNAs. However, it is not clear whether increasing the abundance of miR-26a in CD34⁺-Exos will inhibit the progress of GC-induced ONFH.

Methods

MiR-26a was overexpressed in CD34⁺-Exos (miR-26a-CD34⁺-Exos) to increase their osteogenic potential. The angiogenic potential of miR-26a-CD34⁺-Exos was then examined through evaluations of migration and tube-forming capacities in vitro. In addition, in order to observe the osteogenic effect of miR-26a-CD34⁺-Exos on bone marrow stromal cells (BMSCs), Alizarin red staining, alkaline phosphatase (ALP) activity assays, and qPCR were carried out. Finally, miR-26a-CD34⁺-Exos were injected into a GC-induced ONFH rat model to prevent the progress of GC-induced ONFH. The biological effects of miR-26a-CD34⁺-Exos on the ONFH model were evaluated by micro-CT, angiography, and histological staining.

Results

Our data showed that miR-26a-CD34⁺-Exos enhanced human umbilical vein endothelial cell migration and tube-forming capacities. Furthermore, miR-26a-CD34⁺-Exos strengthened the osteogenic differentiation of BMSCs under the influence of GCs in vitro. Finally, the miR-26a-CD34⁺-Exos increased the vessel density and trabecular bone integrity of the femoral head in the GC-induced ONFH rat model, which inhibited the progress of ONFH.

Conclusions

MiR-26a-CD34⁺-Exos protect the femoral head from damage caused by GCs by strengthening angiogenesis and osteogenesis. The biological effect of miR-26a-CD34⁺-Exos make them suitable for application in the prevention of GC-induced ONFH.

The protective effects of hydrogen sulfide on the myocardial ischemia via regulating Bmal1

BACKGROUND

To investigate the effect of hydrogen peroxide (H₂S) on myocardial clock gene Bmal1 in ischemic cardiomyocytes.

MATERIALS & METHODS

Quantitative PCR (qPCR) was used to detect the expression of Bmal1 at the mRNA level in H9C2 rat cardiomyocytes. The protein expressions of Bax and Bcl-2, PI3K/Akt, caspase-3 were measured by western blotting. The levels of reactive oxygen species (ROS) were determined by ELISA.

RESULTS

The expression level of clock gene Bmal1 demonstrated a clock rhythm of periodic oscillation within 24 h. Compared with the control group, H₂S treatment maintained the rhythm of the clock gene in ischemic cardiomyocytes and increased the transcription and expression levels of Bmal1. H₂S increased cell survival by activating PI3K/Akt signaling pathway, inhibiting mitochondrial apoptosis signaling, and reducing intracellular oxidative stress. PI3K/Akt and Bmal1 were demonstrated to be involved in H₂S protection of cardiomyocyte ischemia. Knockout of Bmal1 gene affects the degree of phosphorylation of Akt and Erk proteins, and the level of ROS production, resulting in a decrease in the protective effects of H₂S.

CONCLUSION

The expression level of Bmal1 has effects on the function of cardiomyocytes such as ROS production. The potential mechanism by which H₂S regulates clock genes may be related to the effect of clock genes on protein phosphorylation levels in ischemic cardiomyocytes.

The neuroprotective effects of novel estrogen receptor GPER1 in mouse retinal ganglion cell degeneration

PURPOSE

To investigate the potential protective effect of novel G protein coupled estrogen receptor (GPER1) against the neurotoxicity induced by NMDA in the mouse retina.

METHODS

We induce retinal ganglion cells (RGCs) toxic injury through intravitreal injection of NMDA or acute ocular hypertension (AOH) induced by anterior chamber infusion with saline. Endogenous ligand 17-β-estradiol (E2), GPER1 agonist (G-1), and E2 with GPER1 antagonist (G-15) or classic estrogen receptor α and β (ERα and ERβ) antagonist tamoxifen (TAM) were subcutaneous administered before NMDA to identify the possible involved receptors. Immunofluorescence staining was performed to explore the survival of RGCs and Müller cell gliosis. TUNEL staining was used to evaluate the RGC apoptosis. The involved molecular pathway was detected via antibody array expression profiling.

RESULTS

Activation of estrogen receptor by E2 or G-1 could significantly rescue the RGCs injury in NMDA administration. The protective effect was carried exclusively by GPER1 activation. E2 application can still mimicked the protective function when estrogen receptor α and β (ERα and ERβ) blocked by tamoxifen (TAM), while the effects was blocked by GPER1 antagonist G-15. Moreover, the TUNEL positive RGCs and GFAP expression level were both attenuated in G-1 application and the effects could be reversed by G-15. In addition, application of the PI3K/Akt antagonist LY294002 counteracted the effect of G-1. And a number of apoptosis regulatory factors decreased dramatically in the G-1 group, including Bad, Caspase 3, Caspase 7, Smad2, P-53 and TAK1. Also, similar protective effect of G-1 was spotted in acute ocular hypertension (AOH) model.

CONCLUSION

Estrogen played a protective role via a novel estrogen receptor, GPER1, instead of classical receptors ERα or ERβ. Activation of GPER1 attenuated RGCs apoptosis and Müller cells gliosis, indicating GPER1 as a potential treatment target in RGCs degeneration diseases.

Exosomes derived from platelet-rich plasma mediate hyperglycemia-induced retinal endothelial injury via targeting the TLR4 signaling pathway

In this study, we aimed to investigate whether exosomes derived from platelet-rich plasma (PRP-Exos) can regulate hyperglycemia-induced retinal injury via targeting the TLR4 signaling pathway. We studied the effects of PRP-Exos on retinal endothelial injury in diabetic rats and human retinal endothelial cells (HRECs) in vitro. Isolated PRP-Exos were observed by transmission electron microscopy and flow cytometry. Samples were obtained from the retinas of rats and cultured HRECs after treatment to analyze reactive oxygen species levels. Immunofluorescence and Western blotting were conducted to assess the levels of adhesion molecules and the TLR4 signaling pathway. The content of CXCL10 in PRP-Exos was analyzed by Western blot. The plasma level of PRP-Exos was greatly increased in diabetic rats. In cultured HRECs, PRP-Exos induced the production of malonyldialdehyde(MDA) and reactive oxygen species(ROS) and inhibited the activity of superoxide dismutase(SOD). Further analysis showed that the activation of the TLR4 pathway by PRP-Exos played a pivotal role in regulating inflammation. The inhibition of the TLR4 pathway by TAK-242 had a robust protective effect on PRP-Exo-induced retinal endothelial injury in vitro and vivo. In addition, PRP-Exo-derived CXCL10 led to retinal endothelial injury, and antagonizing CXCL10 with a CXCL10-neutralizing antibody dramatically attenuated such injury. In summary, PRP-Exos mediate hyperglycemia-induced retinal endothelial injury by upregulating the TLR4 signaling pathway.

BMSC-derived exosomes carrying microRNA-122-5p promote proliferation of osteoblasts in osteonecrosis of the femoral head

Mesenchymal stem cells (MSCs) with multipotential differentiation capacity can differentiate into bone cells under specific conditions and can be used to treat osteonecrosis (ON) of the femoral head (ONFH) through cell transplantation. The current study aims to explore the role of bone marrow (BM) MSCs (BMSCs)-derived exosomes carrying microRNA-122-5p (miR-122-5p) in ONFH rabbit models.First, rabbit models with ONFH were established. ONFH-related miRNAs were screened using the Gene Expression Omnibus (GEO) database. A gain-of-function study was performed to investigate the effect of miR-122-5p on osteoblasts and BMSCs and effects of exosomes carrying miR-122-5p on ONFH. Co-culture experiments for osteoblasts and BMSCs were performed to examine the role of exosomal miR-122-5p in osteoblast proliferation and osteogenesis. The target relationship between miR-122-5p and Sprouty2 (SPRY2) was tested.MiR-122, significantly decreased in ONFH in the GSE89587 expression profile, was screened. MiR-122-5p negatively regulated SPRY2 and elevated the activity of receptor tyrosine kinase (RTK), thereby promoting the proliferation and differentiation of osteoblasts. In vivo experiments indicated that bone mineral density (BMD), trabecular bone volume (TBV), and mean trabecular plate thickness (MTPT) of femoral head were increased after over-expressing miR-122-5p in exosomes. Significant healing of necrotic femoral head was also observed.Exosomes carrying over-expressed miR-122-5p attenuated ONFH development by down-regulating SPRY2 via the RTK/Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Findings in the present study may provide miR-122-5p as a novel biomarker for ONFH treatment.

Icariin promotes angiogenesis in glucocorticoid-induced osteonecrosis of femoral heads: In vitro and in vivo studies

The injury and dysfunction of the femoral head microvascular endothelial cells are associated with the pathogenesis of glucocorticoid-induced osteonecrosis of the femoral head (ONFH). Reports indicate that icariin (ICA) can enhance vascular roles and also inhibit endothelial cell dysfunction. However, it still remains unclear whether ICA can promote angiogenesis in glucocorticoid-induced ONFH. In this study, we investigate this hypothesis through in vitro and in vivo experiments. Results showed that 0.1 mg/mL hydrocortisone significantly suppressed bone microvascular endothelial cells (BMECs) proliferation while ICA at 10^-5  mol/L reversed this inhibition. ICA significantly promoted BMECs migration, tube formation, the angiogenesis-related cytokines expression and the activation of Akt. Furthermore, ICA enhanced Bcl-2 expression but diminished Bax expression. According to in vivo results, rats with ICA treatment exhibited a lower ratio of empty lacunae, higher volume of blood vessels and more CD31-positive cells. This study revealed that ICA promotes angiogenesis of BMECs in vitro and improves femoral head blood vessel volume of rats treated with glucocorticoid, suggesting the efficacy of ICA in the prevention of glucocorticoid-induced ONFH.

Extracellular vesicles in bone and tooth: A state-of-art paradigm in skeletal regeneration

Bone and tooth, fundamental parts of the craniofacial skeleton, are anatomically and developmentally interconnected structures. Notably, pathological processes in these tissues underwent together and progressed in multilevels. Extracellular vesicles (EVs) are cell-released small organelles and transfer proteins and genetic information into cells and tissues. Although EVs have been identified in bone and tooth, particularly EVs have been identified in the bone formation and resorption, the concrete roles of EVs in bone and tooth development and diseases remain elusive. As such, we review the recent progress of EVs in bone and tooth to highlight the novel findings of EVs in cellular communication, tissue homeostasis, and interventions. This will enhance our comprehension on the skeletal biology and shed new light on the modulation of skeletal disorders and the potential of genetic treatment.

The Role of Exosomes in Bone Remodeling: Implications for Bone Physiology and Disease

Bone remodeling represents a physiological phenomenon of continuous bone tissue renewal that requires fine orchestration of multiple cell types, which is critical for the understanding of bone disease but not yet clarified in precise detail. Exosomes, which are cell-secreted nanovesicles drawing increasing attention for their broad biosignaling functions, can shed new light on how multiple heterogeneous cells communicate for the purpose of bone remodeling. In the healthy bone, exosomes transmit signals favoring both bone synthesis and resorption, regulating the differentiation, recruitment, and activity of most cell types involved in bone remodeling and even assuming an active role in extracellular matrix mineralization. Additionally, in the ailing bone, they actively participate in pathogenic processes constituting also potential therapeutic agents and drug vectors. The present review summarizes the current knowledge on bone exosomes and bone remodeling in health and disease.

Exosomes derived from Wharton's jelly of human umbilical cord mesenchymal stem cells reduce osteocyte apoptosis in glucocorticoid-induced osteonecrosis of the femoral head in rats via the miR-21-PTEN-AKT signalling pathway

Purpose: Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a common disease after long-term or high-dose glucocorticoid use. The pathogenesis of GIONFH is still controversial, and abnormal bone metabolism caused by glucocorticoids may be one of the important factors. Exosomes, owing to their positive effect on bone repair, show promising therapeutic effects on bone-related diseases. In this study, we hypothesised that exosomes reduce osteocyte apoptosis in rat GIONFH via the miR-21-PTEN-AKT signalling pathway. Methods: To evaluate the effects of exosomes in GIONFH, a dexamethasone-treated or exosome-treated in vitro cell model and a methylprednisolone-treated in vivo rat model were set up. In vitro, a CCK-8 assay and 5-ethynyl-2'-deoxyuridine staining were performed to evaluate the proliferation of osteocytes. Further, a terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, annexin V-fluorescein isothiocyanate-propidium iodide staining, and western blotting were conducted to evaluate the apoptosis of osteocytes. In vivo, we used micro-computed tomography and histological and immunohistochemical analyses to assess the effects of exosomes. Moreover, the mechanism of exosome action on osteocyte apoptosis through the miR-21-PTEN-AKT pathway was investigated by high-throughput RNA sequencing, fluorescence in situ hybridisation, luciferase reporter assays, and western blotting. Results: High-throughput RNA sequencing results showed that the AKT signalling pathway was up-regulated in the exosome group. Quantitative PCR and western blotting confirmed that the relative expression of genes in the AKT pathway was up-regulated. Western blotting revealed that AKT activated by exosomes inhibited osteocyte apoptosis. RNA fluorescence in situ hybridisation and luciferase reporter assays were performed to confirm the interaction between miR-21 and PTEN. According to the experiment in vivo, exosomes prevented GIONFH in a rat model as evidenced by micro-computed tomography scanning and histological and immunohistochemical analyses. Conclusions: Exosomes are effective at inhibiting osteocyte apoptosis (in MLO-Y4 cells) and at preventing rat GIONFH. These beneficial effects are mediated by the miR-21-PTEN-AKT signalling pathway.

circRNA_0006393 promotes osteogenesis in glucocorticoid‑induced osteoporosis by sponging miR‑145‑5p and upregulating FOXO1

Glucocorticoids are the most common cause of glucocorticoid‑induced osteoporosis (GIOP). Moreover, the role of circular RNAs (circRNAs) in the regulation of bone metabolism remains unclear. Therefore, in the present study, it was hypothesized that hsa_circ_0006393 may play an important role in GIOP. To investigate the role of circRNAs in GIOP, treatment with dexamethasone or transfection with a vector overexpressing hsa_circ_0006393 were performed using in vitro cell and in vivo mouse models. Reverse transcription‑quantitative PCR, fluorescence in situ hybridization and western blotting were performed to investigate the function of hsa_circ_0006393 in vitro. In addition, the effects of hsa_circ_0006393 on osteogenesis were investigated. Dual‑energy X‑ray absorptiometry analysis was performed to examine the osteogenic potential of hsa_circ_0006393 in vivo. Moreover, the mechanism underlying hsa_circ_0006393‑mediated bone metabolism regulation via the microRNA (miR)‑145‑5p/forkhead box O1 (FOXO1) pathway was investigated. The present results suggested that the expression level of hsa_circ_0006393 was decreased in patients with GIOP. Furthermore, the overexpression of hsa_circ_0006393 increased the expression level of genes associated with osteogenesis. Moreover, hsa_circ_0006393 was identified to be localized mainly in the cytoplasm and nucleus of bone marrow mesenchymal stem cells. miR‑145‑5p was found to be directly targeted by hsa_circ_0006393. Collectively, hsa_circ_0006393 increases the expression levels of osteogenic genes during bone remodeling by sponging miR‑145‑5p and upregulating FOXO1.

Exosomes from mesenchymal stem cells modulate endoplasmic reticulum stress to protect against nucleus pulposus cell death and ameliorate intervertebral disc degeneration in vivo

Objectives: Intervertebral disc degeneration (IDD) is widely accepted as a cause of low back pain and related degenerative musculoskeletal disorders. Nucleus pulposus (NP) cell apoptosis which is related to excessive endoplasmic reticulum (ER) stress in the intervertebral disc (IVD) could aggravate IDD progression. Many studies have shown the therapeutic potential of exosomes derived from bone marrow mesenchymal stem cells (MSC-exos) in degenerative diseases. We hypothesized that the delivery of MSC-exos could modulate ER stress and inhibit excessive NP cell apoptosis during IDD.

Methods: The ER stress levels were measured in normal or degenerative NP tissues for contrast. The effects of MSC-exos were testified in advanced glycation end products (AGEs) -induced ER stress in human NP cells. The mechanism involving AKT and ERK signaling pathways was investigated using RNA interference or signaling inhibitors. Histological or immunohistochemical analysis and TUNEL staining were used for evaluating MSC-exos therapeutic effects in vivo.

Results: The ER stress level and apoptotic rate was elevated in degenerative IVD tissues. MSC-exos could attenuate ER stress-induced apoptosis by activating AKT and ERK signaling. Moreover, delivery of MSC-exos in vivo modulated ER stress-related apoptosis and retarded IDD progression in a rat tail model.

Conclusions: These results highlight the therapeutic effects of exosomes in preventing IDD progression. Our work is the first to demonstrate that MSC-exos could modulate ER stress-induced apoptosis during AGEs-associated IVD degeneration.

Effects of transcription factor EB on oxidative stress and apoptosis induced by high glucose in podocytes

The aim of the present study was to investigate the effects of transcription factor EB (TFEB) overexpression on oxidative stress, mitochondrial function and apoptosis in podocytes induced with high glucose. High glucose-induced time-dependent changes in TFEB expression were identified and nuclear translocation of TFEB was observed in podocytes. Overexpression of TFEB markedly reduced high glucose-induced oxidative stress in podocytes, and increased the expression of superoxide dismutase 2 and heme oxygenase 1 antioxidant enzymes. It was further observed that TFEB overexpression could partially restore the expression of peroxisome proliferator-activated receptor-γ coactivator-1α, transcription factor A, mitochondrial, and cytochrome c oxidase subunit 4, thereby enhancing mitochondrial biosynthesis. Furthermore, overexpression of TFEB reduced mitochondrial swelling and fragmentation, restored mitochondrial membrane potential, and contributed to the restoration of mitochondrial function. By overexpressing TFEB, it was revealed that TFEB increased the ratios of phosphorylated (p)-Akt/Akt and p-Bad/Bad, and the expression of downstream Bcl-xl, and reduced the ratio of Bax/Bcl-2 and the expression of cleaved-caspase-3 compared with high glucose-treatment. Furthermore, when the Akt phosphorylation inhibitor Ly294002 was added, the improvement by TFEB to high glucose-induced apoptosis was significantly reduced. These findings suggest that overexpressing TFEB could reduce the production of reactive oxygen species in podocytes in a high glucose environment, relieve oxidative stress, promote mitochondrial biogenesis and renewal functions, and reduce high glucose-induced podocyte apoptosis by activating the Akt/Bad pathway.

[Effectiveness and mechanism of pure platelet-rich plasma on osteochondral injury of talus]

Objective

To explore the effectiveness and mechanism of pure platelet-rich plasma (P-PRP) on osteochondral injury of talus.

Methods

Thirty-six patients with osteochondral injury of talus selected between January 2014 and October 2017 according to criteria were randomly divided into control group (group A), leukocyte PRP (L-PRP) group (group B), and P-PRP group (group C), with 12 cases in each group. There was no significant difference in gender, age, disease duration, and Hepple classification among the three groups ( P>0.05). Patients in the groups B and C were injected with 2.5 mL L-PRP or P-PRP at the bone graft site, respectively. Patients in the group A were not injected with any drugs. The American Orthopaedic Foot and Ankle Society (AOFAS) score and visual analogue scale (VAS) score were used to evaluate the effectiveness before operation and at 3, 6, and 12 months after operation. Study on the therapeutic mechanism of P-PRP: MC3T3-E1 cells were randomly divided into control group (group A), L-PRP group (group B), and P-PRP group (group C). Groups B and C were cultured with culture medium containing 5% L-PRP or P-PRP respectively. Group A was cultured with PBS of the same content. MTT assay was used to detect cell proliferation; ELISA was used to detect the content of matrix metalloprotein 9 (MMP-9) protein in supernatant; alkaline phosphatase (ALP) activity was measured; and real-time fluorescence quantitative PCR (qRT-PCR) was used to detect the expression of osteopontin (OPN), collagen type Ⅰ, and MMP-9 in cells. Western blot was used to detect the expression of MMP-9 in supernatant and phosphoinositide 3-kinase (PI3K), phosphorylated protein kinase B (pAKT), and phosphorylated c-Jun (p-c-Jun) in cells.

Results

All patients were followed up 13-25 months, with an average of 18 months. No complication such as wound infection and internal fixation failure occurred. MRI showed that the degree of injury was similar between the three groups before operation, and patients in the three groups all recovered at 6 months after operation. Moreover, group C was superior to groups A and B. Compared with preoperation, AOFAS scores and VAS scores in the three groups were all significantly improved at each time point after operation ( P<0.05). AOFAS score of group C was significantly higher than that of groups A and B at 3, 6, and 12 months after operation ( P<0.05); there was no significant difference in VAS score between the three groups ( P>0.05). Study on the therapeutic mechanism of P-PRP: The absorbance ( A) value, ALP activity, the relative mRNA expression of OPN and collagen type Ⅰ in group C were significantly higher than those in groups A and B ( P<0.05), and those in group B were significantly higher than those in group A ( P<0.05). The relative expression of MMP-9 protein and mRNA and the content of MMP-9 protein detected by ELISA in group B were significantly higher than those in groups A and C, while those in group C were significantly lower than those in group A ( P<0.05). Western blot detection showed that the relative expression of PI3K, pAKT, and p-c-Jun protein in group B was significantly higher than those in groups A and C ( P<0.05), but there was no significant difference between groups A and C ( P>0.05).

Conclusion

P-PRP is superior to L-PRP for osteochondral injury of talus, which may be related to the inhibition of PI3K/AKT/AP-1 signaling pathway in the osteoblast, thereby reducing the secretion of MMP-9.

NADPH Oxidase Isoforms Are Involved in Glucocorticoid-Induced Preosteoblast Apoptosis

Oxidative stress induced by long-term glucocorticoid (GC) use weakens the repair capacity of bone tissue. Nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase (NOX) is a superoxide-generating enzyme that plays an important role in regulating bone metabolism. To clarify the role of nonphagocytic NOX isoforms in osteoblast reactive oxygen species (ROS) generation and apoptosis, dexamethasone was used to establish a high-dose GC environment in vitro. A dose-dependent increase in intracellular ROS generation was demonstrated, which was accompanied by increased osteoblastic MC3T3-E1 cell apoptosis. Addition of the ROS inhibitor NAC (N-acetyl-L-cysteine) or NOX inhibitor DPI (diphenyleneiodonium) reversed this effect, indicating that NOX-derived ROS can induce osteoblast apoptosis under high-dose dexamethasone stimulation. NOX1, NOX2, and NOX4 are NOX homologs recently identified in bone tissue. To clarify the NOX isoforms that play a role in osteoblast ROS generation, Nox1, Nox2, and Nox4 mRNA expression and NOX2 and NOX4 protein expression were analyzed. Nox1 and Nox4 mRNA expression was elevated in a dose-dependent manner after culture in 100 nM, 250 nM, 500 nM, or 1000 nM dexamethasone, and the increased expression of NOX1 mRNA was more significant compared with NOX4 mRNA. Small interfering RNAs (siRNAs) were used to confirm the role of NOX1 and NOX4 in ROS generation. To clarify the signaling pathway in ROS-induced osteoblast apoptosis, mitogen-activated protein kinase (MAPK) signaling molecules were analyzed. Phosphorylated ASK1 and p38 levels were significantly higher in the 1000 nM dexamethasone group, which NAC or DPI markedly attenuated. However, the total mRNA and protein levels of ASK1 and p38 between the dexamethasone group and control were not significantly different. This is related to ROS regulating the posttranslational modification of ASK1 and p38 in MC3T3-E1 cell apoptosis. Altogether, NOX1- and NOX4-derived ROS plays a pivotal role in high-dose dexamethasone-induced preosteoblast apoptosis by increasing phosphorylated ASK1 and p38 and may be an important mechanism in steroid-induced avascular necrosis of the femoral head (SANFH).

Glucocorticoid induces osteonecrosis of the femoral head in rats through GSK3β-mediated osteoblast apoptosis

OBJECTIVE

One of the important causes of glucocorticoids (GCs)-induced osteonecrosis of the femoral head (ONFH) is osteoblast apoptosis. Glycogen synthase kinase 3β (GSK3β) has been reported to be related to dexamethasone (Dex)-induced osteoblast apoptosis. This study aimed to determine whether GSK3β plays role in GC-induced ONFH and investigate the underlying mechanism.

METHODS

18 male Sprague-Dawley rats were divided into 3 groups. Rats from ONFH group underwent lipopolysaccharide and methylprednisolone injection. Lithium chloride (LiCl, a GSK3β inhibitor) group were fed with LiCl solution. The control group were untreated. Osteonecrosis, apoptosis and bone loss were evaluated by HE staining, TUNEL staining and micro-CT respectively. Protein expressions were examined by western blotting. In addition, primary osteoblast cells were transfected by GSK3β-siRNA and related signaling pathway and proteins were examined.

RESULTS

ONFH group showed a relative high percentage of empty lacunae and apoptotic cells, whilst LiCl treatment markedly decreased the percentage. LiCl treatment decreased GC-induced bone loss. Immunoblot analysis for GSK3β showed decreased level of Ser9-phosphorylated GSK3β in ONFH group compared with control group. Knockdown of GSK3β by siRNA in primary osteoblast cells attenuated DEX-induced apoptosis and loss of mitochondrial transmembrane potential (Δψm). GSK3β knockdown also reversed the release of cytochrome C (Cyt C) from mitochondria to the cytosol. GSK3β decreased apoptosis-related protein expression both in vitro and in vivo.

CONCLUSION

Our findings suggest that GC induces ONFH in rats through GSK3β-mediated osteoblast apoptosis, with involvement of mitochondrial apoptotic pathway.

2,5-Hexanedione mediates neuronal apoptosis through suppression of NGF via PI3K/Akt signaling in the rat sciatic nerve

Because precise mechanism for 2,5-hexanedione (HD)-induced neuronal apoptosis largely remains unknown, we explored the potential mechanisms both in vivo and in vitro Rats were intraperitoneally exposed to HD at different doses for 5 weeks, following which the expression levels of nerve growth factor (NGF), phosphorylation of Akt and Bad, dimerization of Bad and Bcl-xL, as well as the release of cytochrome c and the caspase-3 activity were measured. Moreover, these variables were also examined in vitro in HD-exposed VSC4.1 cells with or without a PI3K-specific agonist (IGF-1), and in HD-exposed VSC4.1 cells with or without a PI3K-specific inhibitor (LY294002) in the presence or absence of NGF. The data indicate that, as the concentration of HD increased, rats exhibited progressive gait abnormalities, and enhanced neuronal apoptosis in the rat sciatic nerve, compared with the results observed in the control group. Furthermore, HD significantly down-regulated NGF expression in the rat sciatic nerve. Moreover, suppression of NGF expression inhibited the phosphorylation of Akt and Bad. Meanwhile, an increase in the dimerization of Bad and Bcl-xL in mitochondria resulted in cytochrome c release and caspase-3 activation. In contrast, HD-induced apoptosis was eliminated by IGF-1. Additionally, NGF supplementation reversed the decrease in phosphorylation of Akt and Bad, as well as reversing the neuronal apoptosis in HD-exposed VSC4.1 cells. However, LY294002 blocked these effects of NGF. Collectively, our results demonstrate that mitochondrial-dependent apoptosis is induced by HD through NGF suppression via the PI3K/Akt pathway both in vivo and in vitro.

Extracellular vesicles in bone: "dogrobbers" in the "eternal battle field"

Throughout human life, bone is constantly in a delicate dynamic equilibrium of synthesis and resorption, hosting finely-tuned bone mineral metabolic processes for bone homeostasis by collaboration or symphony among several cell types including osteoclasts (OCs), osteoblasts (OBs), osteocytes (OYs), vascular endothelial cells (ECs) and their precursors. Beyond these connections, a substantial level of communication seems to occur between bone and other tissues, and together, they form an organic unit linked to human health and disease. However, the current hypothesis, which includes growth factors, hormones and specific protein secretion, incompletely explains the close connections among bone cells or between bone and other tissues. Extracellular vesicles (EVs) are widely-distributed membrane structures consisting of lipid bilayers, membrane proteins and intravesicular cargo (including proteins and nucleic acids), ranging from 30 nm to 1000 nm in diameter, and their characters have been highly conserved throughout evolution. EVs have targeting abilities and the potential to transmit multidimensional, abundant and complicated information, as powerful and substantial "dogrobbers" mediating intercellular communications. As research has progressed, EVs have gradually become thought of as "dogrobbers" in bone tissue-the "eternal battle field" -in a delicate dynamic balance of destruction and reconstruction. In the current review, we give a brief description of the major constituent cells in bone tissues and explore the progress of current research on bone-derived EVs. In addition, this review also discusses in depth not only potential directions for future research to breakthrough in this area but also problems existing in current research that need to be solved for a better understanding of bone tissues.

CircUSP45 inhibited osteogenesis in glucocorticoid-induced osteonecrosis of femoral head by sponging miR-127-5p through PTEN/AKT signal pathway: Experimental studies

PURPOSE

large doses of glucocorticoids (GCs) are the most common cause of glucocorticoid-induced osteonecrosis of femoral head (GIONFH). Although awareness of GIONFH among patients with GCs history has increased over recent years, several studies indicate that its mechanism remains unclear.

METHODS

To evaluate the function of circUSP45 in GIONFH, femoral heads in GIONFH patients or femoral heads in fracture patients were collected. In vitro, RT-PCR, FISH, RNA pull down and Western blotting assay were used to evaluate the function of circUSP45. In addition, we also verified the effects of circUSP45 on osteogenesis using alizarin red staining. In vivo, we used HE staining and microCT analysis to evaluate the bone mass. Moreover, the mechanism of circUSP45 regulating osteogenesis through the miR-127-5p/PTEN/AKT pathway was also investigated.

RESULTS

The results showed that expression of circUSP45 increased in GIONFH patients. The overexpression of circUSP45 decreases osteogenic gene expression and inhibits the proliferation of BMSCs. Furthermore, circUSP45 was located mainly in the cytoplasm and directly interacted with miR-127-5p. MiR-127-5p acts with its targets PTEN to regulate the osteogenesis. MicroCT and HE staining verify the function of circUSP45 in GIONFH rat model.

CONCLUSION

CircUSP45 decreases osteogenesis in bone GIONFH by sponging miR-127-5p through PTEN/AKT signal pathway.

Exosome as a Novel Shuttle for Delivery of Therapeutics across Biological Barriers

The effective delivery of target-specific siRNA to the brain by exploiting the exosomes derived from dendritic cells renders the paradigm shift for the prospective use of nanosized exosomes as a delivery system. Although the in vivo targeting strategies by other nanovesicles like liposomes exist, still this novel exosome-based delivery approach holds an inclusive dominance of in vivo security and reduced immunogenicity. Achieving promising exosome-based delivery strategies warrants more desirable exploration of their biology. Over the years, the invention of novel production, characterization, targeting strategies, and cargo loading techniques of exosome improved its ability to reach clinics. Essentially, exosome-based delivery of therapeutics assures to conquer the major hurdles, like delivery of cargos across impermeable biological barriers, like the blood-brain barrier, biocompatibility, increased solubility, metabolic stability, improved circulation time, target specific delivery, and pharmacokinetics, and thereby enhanced the efficacy of loaded therapeutic agents. In this article, we cover the current status of exosome as a delivery vehicle for therapeutics and the challenges that need to be overcome, and we also discuss future perspectives of this exciting field of research to transform it from bench to clinical reality.

Optimization of the Platelet-Rich Plasma Concentration for Mesenchymal Stem Cell Applications

IMPACT STATEMENT

In the current study, we screened the effects of different concentrations of platelet-rich plasma (PRP) on the mesenchymal stem cell (MSC) proliferation and differentiation. Our data demonstrated that concentrated PRP exerted different effects on cell proliferation and on the osteogenic, adipogenic, and chondrogenic differentiation of human bone marrow-derived MSCs. Meanwhile, we optimized PRP concentrations for each of these lineage differentiation and MSC expansion and, thus, suggested several promising clinical strategies for different kinds of diseases. These findings may help explain the controversial effects of PRP on MSCs and improve the progress in precise applications of PRP-based regenerative strategies.

Effect of platelet-rich plasma on proliferation and migration in human dermal fibroblasts

BACKGROUND

Platelet-rich plasma (PRP) is a blood fraction that contains high concentrations of several growth factors. PRP has been recently used in skin wound healing and rejuvenation. However, the precise molecular mechanisms underlying PRP-induced wound healing are unknown.

AIMS

This study aimed to evaluate the effects of PRP on extracellular matrix remodeling, which requires the activation of dermal fibroblasts.

METHODS

Cell proliferation and migration assay, enzyme-linked immunosorbent analysis, and Western blotting were performed on PRP-treated human skin fibroblasts.

RESULTS

Platelet numbers were enhanced by 4.6-fold in PRP compared to that in whole blood. PRP stimulated the proliferation and migration of human dermal fibroblasts and increased the expression of human procollagen I alpha 1, elastin, MMP-1, and MMP-2 in human dermal fibroblasts. PRP-treated human dermal fibroblasts also showed a dramatic reduction in the phosphorylation of c-Jun N-terminal kinase (JNK), whereas total JNK levels were not significantly reduced.

CONCLUSIONS

Collectively, PRP induced increased expression of type I collagen, elastin, MMP-1, and MMP-2, thereby accelerating wound healing. Our findings reveal basic mechanisms underlying PRP-mediated tissue remodeling. Thus, these results could be exploited for clinical dermatology and skin rejuvenation.

Extracellular Vesicles: Potential Participants in Circadian Rhythm Synchronization

The circadian rhythm (CR) is a set of autonomous endogenous oscillators. Exposure to the 24-hour day-night cycle synchronizes our CR system, maintaining homeostasis and human health. Several mechanisms for the CR system have been proposed, including those underlying the function (transcriptional-translational negative-feedback loops, or TTFLs), mechanisms regulating the TTFLs, and the mechanism by which the "server clock" is synchronized to environmental time. Several pathways downstream of the "server clock" perform well-characterized biological functions. However, the synchronization between the "server clock" (the endogenous master clock seated in the suprachiasmatic nucleus within the hypothalamus) and the "client clock" (imbedded in nearly every cell in the form of interlocking TTFLs) is difficult to explain with current theories. Extracellular vesicles (EVs), which are involved in intercellular communication and have recently been found to participate in regulation of the "client clock", might be the answer to this question. In this review, we summarize the current knowledge of CRs, TTFLs, and EVs, examine research findings about the functions of EVs in the CR system, and discuss the issues requiring attention in future research.

Dexmedetomidine alleviates cerebral ischemia-reperfusion injury by inhibiting endoplasmic reticulum stress dependent apoptosis through the PERK-CHOP-Caspase-11 pathway

Dexmedetomidine (Dex) has the neuroprotective effect on cerebral ischemia-reperfusion injury (CIRI). But the mechanism is not yet clear. In this study, we established a model of middle cerebral artery occlusion (MCAO) and treated primary cortical neurons with oxygen glucose deprivation (OGD), followed by Dex treatment. Neurological protection of Dex was then assessed by neurological deficit score, brain edema, TTC staining, TUNEL assay, Western blot analysis, immunohistochemistry, and RT-PCR. The results showed that Dex significantly reduced the neurological deficit score, brain edema and cerebral infarction area due to CIRI. After Dex treatment, the expression levels of ER stress-related apoptosis pathway proteins (GRP78, p-PERK, CHOP and Cleaved-caspase-3) were significantly decreased and the apoptosis of brain cells was also significantly reduced. Immunohistochemistry showed that expression and nuclear localization of CHOP decreased significantly after the application of Dex. The downstream apoptotic protein caspase-11 mediated by PERK-CHOP was also markedly inhibited by Dex. In conclusion, our results suggested that Dex reduced ER stress-induced apoptosis after CIRI. Its protective mechanism may be related to PERK-CHOP-Caspase-11 dependent signaling pathway.