MG53 Protects hUC-MSCs against Inflammatory Damage and Synergistically Enhances Their Efficacy in Neuroinflammation Injured Brain through Inhibiting NLRP3/Caspase-1/IL-1β Axis

Fisetin Promotes Functional Recovery after Spinal Cord Injury by Inhibiting Microglia/Macrophage M1 Polarization and JAK2/STAT3 Signaling Pathway

Spinal cord injury (SCI) is one of the most serious health problems, with no effective therapy. Recent studies indicate that Fisetin, a natural polyphenolic flavonoid, exhibits multiple functions, such as life-prolonging, antioxidant, antitumor, and neuroprotection. However, the restorative effects of Fisetin on SCI and the underlying mechanism are still unclear. In the present study, we found that Fisetin reduced LPS-induced apoptosis and oxidative damage in PC12 cells and reversed LPS-induced M1 polarization in BV2 cells. Additionally, Fisetin safely and effectively promoted the motor function recovery of SCI mice by attenuating neurological damage and promoting neurogenesis at the lesion. Moreover, Fisetin administration inhibited glial scar formation, modulated microglia/macrophage polarization, and reduced neuroinflammation. Network pharmacology, RNA-seq, and molecular biology revealed that Fisetin inhibited the activation of the JAK2/STAT3 signaling pathway. Notably, Colivelin TFA, an activator of JAK2/STAT3 signaling, attenuated Fis-mediated neuroinflammation inhibition and therapeutic effects on SCI mice. Collectively, Fisetin promotes functional recovery after SCI by inhibiting microglia/macrophage M1 polarization and the JAK2/STAT3 signaling pathway. Thus, Fisetin may be a promising therapeutic drug for the treatment of SCI.

MG53 binding to CAV3 facilitates activation of eNOS/NO signaling pathway to enhance the therapeutic benefits of bone marrow-derived mesenchymal stem cells in diabetic wound healing

Impaired wound healing in diabetes results from a complex interplay of factors that disrupt epithelialization and wound closure. MG53, a tripartite motif (TRIM) family protein, plays a key role in repairing cell membrane damage and facilitating tissue regeneration. In this study, bone marrow-derived mesenchymal stem cells (BMSCs) were transduced with lentiviral vectors overexpressing MG53 to investigate their efficacy in diabetic wound healing. Using a db/db mouse wound model, we observed that BMSCs-MG53 significantly enhanced diabetic wound healing. This improvement was associated with marked increase in re-epithelialization and vascularization. BMSCs-MG53 promoted recruitment and survival of BMSCs, as evidenced by an increase in MG53/Ki67-positive BMSCs and their improved response to scratch wounding. The combination therapy also promoted angiogenesis in diabetic wound tissues by upregulating the expression of angiogenic growth factors. MG53 overexpression accelerated the differentiation of BMSCs into endothelial cells, manifested as the formation of mature vascular network structure and a remarkable increase in DiI-Ac-LDL uptake. Our mechanistic investigation revealed that MG53 binds to caveolin-3 (CAV3) and subsequently increases phosphorylation of eNOS, thereby activating eNOS/NO signaling. Notably, CAV3 knockdown reversed the promoting effects of MG53 on BMSCs endothelial differentiation. Overall, our findings support the notion that MG53 binds to CAV3, activates eNOS/NO signaling pathway, and accelerates the therapeutic effect of BMSCs in the context of diabetic wound healing. These insights hold promise for the development of innovative strategies for treating diabetic-related impairments in wound healing.

MG53 protects against Coxsackievirus B3-induced acute viral myocarditis in mice by inhibiting NLRP3 inflammasome-mediated pyroptosis via the NF-κB signaling pathway

Pyroptosis, a novel programmed cell death mediated by NOD-like receptor protein 3 (NLRP3) inflammasome, is a critical pathogenic process in acute viral myocarditis (AVMC). Mitsugumin 53 (MG53) is predominantly expressed in myocardial tissues and has been reported to exert cardioprotective effects through multiple pathways. Herein, we aimed to investigate the biological function of MG53 in AVMC and its underlying regulatory mechanism in pyroptosis. BALB/c mice and HL-1 cells were infected with Coxsackievirus B3 (CVB3) to establish animal and cellular models of AVMC. As inflammation progressed in the myocardium, we found a progressive decrease in myocardial MG53 expression, accompanied by a significant enhancement of cardiomyocyte pyroptosis. MG53 overexpression significantly alleviated myocardial inflammation, apoptosis, fibrosis, and mitochondrial damage, thereby improving cardiac dysfunction in AVMC mice. Moreover, MG53 overexpression inhibited NLRP3 inflammasome-mediated pyroptosis, reduced pro-inflammatory cytokines (IL-1β/18) release, and suppressed NF-κB signaling pathway activation both in vivo and in vitro. Conversely, MG53 knockdown reduced cell viability, facilitated cell pyroptosis, and increased pro-inflammatory cytokines release in CVB3-infected HL-1 cells by promoting NF-κB activation. These effects were partially reversed by applying the NF-κB inhibitor BAY 11-7082. In conclusion, our results suggest that MG53 acts as a negative regulator of NLRP3 inflammasome-mediated pyroptosis in CVB3-induced AVMC, partially by inhibiting the NF-κB signaling pathway. MG53 is a promising candidate for clinical applications in AVMC treatment.

Glucose-modified BSA/procyanidin C1 NPs penetrate the blood-brain barrier and alleviate neuroinflammation in Alzheimer's disease models

Alzheimer's disease (AD) is a chronic neurodegenerative disease with high prevalence, long duration and poor prognosis. The blood-brain barrier (BBB) is a physiologic barrier in the central nervous system, which hinders the entry of most drugs into the brain from the blood, thus affecting the efficacy of drugs for AD. Natural products are recognized as one of the promising and unique therapeutic approaches to treat AD. To improve the efficiency and therapeutic effect of the drug across the BBB, a natural polyphenolic compound, procyanidin C-1 (C1) was encapsulated in glucose-functionalized bovine serum albumin (BSA) nanoparticles to construct Glu-BSA/C1 NPs in our study. Glu-BSA/C1 NPs exhibited good stability, slow release, biocompatibility and antioxidant properties. In addition, Glu-BSA/C1 NPs penetrated the BBB, accumulated in the brain by targeting Glut1, and maintained the BBB integrity both in vitro and in vivo. Moreover, Glu-BSA/C1 NPs alleviated memory impairment of 5 × FAD mice by reducing Aβ deposition and Tau phosphorylation and promoting neurogenesis. Mechanistically, Glu-BSA/C1 NPs significantly activated the PI3K/AKT pathway and inhibited the NLRP3/Caspase-1/IL-1β pathway thereby suppressing neuroinflammation. Taken together, Glu-BSA/C1 NPs could penetrate the BBB and mitigate neuroinflammation in AD, which provides a new therapeutic approach targeting AD.

MG53/TRIM72: multi-organ repair protein and beyond

MG53, a member of the tripartite motif protein family, possesses multiple functionalities due to its classic membrane repair function, anti-inflammatory ability, and E3 ubiquitin ligase properties. Initially recognized for its crucial role in membrane repair, the therapeutic potential of MG53 has been extensively explored in various diseases including muscle injury, myocardial damage, acute lung injury, and acute kidney injury. However, further research has revealed that the E3 ubiquitin ligase characteristics of MG53 also contribute to the pathogenesis of certain conditions such as diabetic cardiomyopathy, insulin resistance, and metabolic syndrome. Moreover, recent studies have highlighted the anti-tumor effects of MG53 in different types of cancer, such as small cell lung cancer, liver cancer, and colorectal cancer; these effects are closely associated with their E3 ubiquitin ligase activities. In summary, MG53 is a multifunctional protein that participates in important physiological and pathological processes of multiple organs and is a promising therapeutic target for various human diseases. MG53 plays a multi-organ protective role due to its membrane repair function and its exertion of anti-tumor effects due to its E3 ubiquitin ligase properties. In addition, the controversial aspect of MG53's E3 ubiquitin ligase properties potentially causing insulin resistance and metabolic syndrome necessitates further cross-validation for clarity.

It's a TRIM-endous view from the top: the varied roles of TRIpartite Motif proteins in brain development and disease

The tripartite motif (TRIM) protein family members have been implicated in a multitude of physiologies and pathologies in different tissues. With diverse functions in cellular processes including regulation of signaling pathways, protein degradation, and transcriptional control, the impact of TRIM dysregulation can be multifaceted and complex. Here, we focus on the cellular and molecular roles of TRIMs identified in the brain in the context of a selection of pathologies including cancer and neurodegeneration. By examining each disease in parallel with described roles in brain development, we aim to highlight fundamental common mechanisms employed by TRIM proteins and identify opportunities for therapeutic intervention.

Is MG53 a potential therapeutic target for cancer?

Cancer treatment still encounters challenges, such as side effects and drug resistance. The tripartite-motif (TRIM) protein family is widely involved in regulation of the occurrence, development, and drug resistance of tumors. MG53, a member of the TRIM protein family, shows strong potential in cancer therapy, primarily due to its E3 ubiquitin ligase properties. The classic membrane repair function and anti-inflammatory capacity of MG53 may also be beneficial for cancer prevention and treatment. However, MG53 appears to be a key regulatory factor in impaired glucose metabolism and a negative regulatory mechanism in muscle regeneration that may have a negative effect on cancer treatment. Developing MG53 mutants that balance the pros and cons may be the key to solving the problem. This article aims to summarize the role and mechanism of MG53 in the occurrence, progression, and invasion of cancer, focusing on the potential impact of the biological function of MG53 on cancer therapy.

MG53 ameliorates nerve injury induced neuropathic pain through the regulation of Nrf2/HO-1 signaling in rats

Neuropathic pain is one of the most common types of chronic pain, and it arises as a direct consequence of a lesion or disease that affects the somatosensory system. Mitsugumin53 (MG53), which is a member of the TRIM family of proteins and is known as TRIM72, exerts protective effects on muscle, lung, kidney, brain, and other cells or tissues. Recently, increasing evidence has indicated that MG53 plays a vital role in regulating neuroinflammation and oxidative stress. However, the relationship between MG53 and neuropathic pain is unclear. In this study, we aimed to explore the role of MG3 in neuropathic pain after chronic constriction injury (CCI) to the sciatic nerve in rats. To explore the mechanism of MG53 regulating the development of neuropathic pain, the rats was injected (intrathecal injection) of recombinant human MG53 (rhMG53) protein and/or nuclear factor erythroid 2-related factor 2 (Nrf2) siRNA after CCI. Mechanical allodynia or thermal hyperalgesia was assessed by the 50% paw withdrawal threshold (PWT) or the paw withdrawal latency (PWL). The target molecules was detected using western blotting (WB), immunofluorescence (IF), quantitative real-time polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), biochemical evaluations, and Dihydroethidium (DHE) staining. The results indicated that the expression level of MG53 in the spinal cord was increased after CCI in rats. Moreover, intrathecal injection with rhMG53 protein notably alleviated CCI-induced mechanical allodynia, thermal hyperalgesia, neuroinflammation，oxidative stress and the increased level of reactive oxygen species (ROS) via activation of the Nrf2/heme oxygenase-1 (HO-1) signaling pathway. However, administration of Nrf2 siRNA abrogated the analgesic, anti-inflammatory and antioxidant effects of rhMG53 in CCI model rats. Our study demonstrated that MG53 improved neuropathic pain, neuroinflammation, and oxidative stress via activation of the Nrf2/HO-1 signaling pathway in the spinal cord of CCI model rats, which suggested that MG53 may serve as a new target for the treatment of neuropathic pain.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

TRIM72 Alleviates Muscle Inflammation in mdx Mice via Promoting Mitophagy-Mediated NLRP3 Inflammasome Inactivation

Chronic muscle inflammation exacerbates the pathogenesis of Duchenne muscular dystrophy (DMD), which is characterized by progressive muscle degeneration and weakness. NLRP3 (nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3) inflammasome plays a key role in the inflammatory process, and its abnormal activation leads to a variety of inflammatory or immune diseases. TRIM72 (MG53) is a protective myokine for tissue repair and regeneration. However, little is known about the potential impact of TRIM72 in the crosstalk between mitophagy and inflammatory process of DMD. Here, 10-week-old male mdx mice were injected intramuscularly with adeno-associated virus (AAV-TRIM72) to overexpress TRIM72 protein for 6 weeks. Then, skeletal muscle samples were collected, and relevant parameters were measured by histopathological analysis and molecular biology techniques. C2C12 cell line was transfected with lentivirus (LV-TRIM72) to overexpress or siRNA (si-TRIM72) to suppress the TRIM72 expression for the following experiment. Our data firstly showed that the TRIM72 expression was decreased in skeletal muscles of mdx mice. Then, we observed the increased NLRP3 inflammasome and impaired mitophagy in mdx mice compared with wild type mice. In mdx mice, administration of AAV-TRIM72 alleviated the accumulation of NLRP3 inflammasome and the consequent IL-18 and IL1β maturation by inducing autophagy, while this protective effect was reversed by chloroquine. Mitochondrial reactive oxygen species (mtROS), as a recognized activator for NLRP3 inflammasome, was attenuated by TRIM72 through the induction of mitophagy in C2C12 cells. Additionally, we proposed that the TRIM72 overexpression might promote mitophagy through both the early stage by PI3K-AKT pathway and the late stage by autolysosome fusion. In conclusion, the current study suggests that TRIM72 prevents DMD inflammation via decreasing NLRP3 inflammasomes and enhancing mitophagy. Collectively, our study provides insight into TRIM72 as a promising target for therapeutic intervention for DMD.

Tripartite motif 72 inhibits apoptosis and mitochondrial dysfunction in neural stem cells induced by anesthetic sevoflurane by activating PI3K/AKT pathway

Anesthetics exposure induces neurocognitive deficits during brain development and impairs self-renewal and differentiation of neural stem cells (NSCs). Tripartite motif 72 (TRIM72, also known as mitsugumin 53, MG53) is involved in tissue repair and plasma membrane damage repair. The neuroprotective effect of TRIM72 against sevoflurane-induced neurotoxicity of NSCs was investigated in this study. First, human NSCs were exposed to different concentrations of sevoflurane. Results showed that TRIM72 was downregulated in sevoflurane-treated NSCs. Exposure to sevoflurane reduced cell viability in NSCs. Second, sevoflurane-treated NSCs were stimulated with recombinant human TRIM72 (rhTRIM72). Treatment with rhTRIM72 enhanced the cell viability in sevoflurane-treated NSCs. Moreover, treatment with a rhTRIM72-attenuated sevoflurane-induced increase in caspase-3 activity in NSCs. Third, JC-1 aggregates were deceased and JC-1 monomer was increased in sevoflurane-treated NSCs, which were reversed by rhTRIM72. Furthermore, rhTRIM72 also weakened sevoflurane-induced decrease in superoxide dismutase and glutathione peroxidase and increase in malondialdehyde and reactive oxygen species in NSCs. Finally, reduced phosphorylation levels of protein kinase B (AKT) and phosphatidylinositol 3-kinase (PI3K) in sevoflurane-treated NSCs were upregulated by rhTRIM72. In conclusion, TRIM72 inhibited cell apoptosis and reduced the mitochondria membrane potential of sevoflurane-treated NSCs through activation of the PI3K/AKT pathway.

Fucoidan ameliorates LPS-induced neuronal cell damage and cognitive impairment in mice

The incidence of cognitive impairment is rising globally, but there is no effective therapy. Recent studies showed that fucoidan (Fuc), a sulfated polysaccharide enriched in brown algae, is widely used due to its anti-inflammatory, antioxidant, and prebiotic effects. However, the effects and mechanisms of Fuc on lipopolysaccharide (LPS)-induced neuronal cell damage and cognitive impairment in mice need to be explored further. In the present study, we found that Fuc treatment protected HT22 cells from LPS-induced damage by inhibiting the activation of NLRP3 inflammasomes. Fuc exerted neuroprotective effects in mice with LPS-induced cognitive impairment by ameliorating neuroinflammation, promoting neurogenesis, and reducing blood-brain barrier and intestinal barrier permeability. Mechanistically, Fuc supplement significantly restructured the gut microbiota composition, which may be related to glucose and fructose metabolism. In conclusion, Fuc ameliorated LPS-induced neuronal cell damage and cognitive impairment in mice, suggesting that Fuc may be a medicinal and food homologous functional agent to improve cognitive function.

Protective role of MG53 against ischemia/reperfusion injury on multiple organs: A narrative review

Ischemia/reperfusion (I/R) injury is a common clinical problem after coronary angioplasty, cardiopulmonary resuscitation, and organ transplantation, which can lead to cell damage and death. Mitsugumin 53 (MG53), also known as Trim72, is a conservative member of the TRIM family and is highly expressed in mouse skeletal and cardiac muscle, with minimal amounts in humans. MG53 has been proven to be involved in repairing cell membrane damage. It has a protective effect on I/R injury in multiple oxygen-dependent organs, such as the heart, brain, lung, kidney, and liver. Recombinant human MG53 also plays a unique role in I/R, sepsis, and other aspects, which is expected to provide new ideas for related treatment. This article briefly reviews the pathophysiology of I/R injury and how MG53 mitigates multi-organ I/R injury.

MG53 protein rejuvenates hUC-MSCs and facilitates their therapeutic effects in AD mice by activating Nrf2 signaling pathway

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) transplantation is a promising therapy for Alzheimer's disease (AD). However, hUC-MSCs cultured in vitro easily exhibit replicative senescence, which restricts their application. Although MG53 protein demonstrates multiple roles for a variety of cells and tissues repair, it remains unknown whether MG53 could rejuvenate senescent hUC-MSCs and enhance their efficacy in AD model. Here, we firstly presented that MG53 reinstated senescent hUC-MSCs via the activation of the Nrf2 signaling pathway by increasing cell proliferation and migration, ameliorating senescence and oxidative stress, and decreasing the release of senescence-associated secretory phenotype. In vivo studies showed that MG53 treatment improved the therapeutic effect of senescent hUC-MSCs in AD mice. Furthermore, MG53 combined with young hUC-MSCs transplantation alleviated cognitive deficit and depression-like behavior in AD mice, reduced Aβ deposition and Tau phosphorylation, promoted neurogenesis, and inhibited glia cells activation and oxidative stress by activating the Nrf2 signaling. Moreover, these neuroprotective effects mediated by MG53 and hUC-MSCs were partly reversed by Brusatol, a specific inhibitor of Nrf2 signaling. Taken together, our study revealed that MG53 could rejuvenate senescent hUC-MSCs and facilitate their efficacy in AD mice at least partly through activating Nrf2 signaling pathway, which suggest that the combined therapy of MG53 and hUC-MSCs may be a novel and effective strategy for AD.

TLR4-IN-C34 Inhibits Lipopolysaccharide-Stimulated Inflammatory Responses via Downregulating TLR4/MyD88/NF-κB/NLRP3 Signaling Pathway and Reducing ROS Generation in BV2 Cells

TLR4 signal activated by lipopolysaccharide (LPS) is involved in the pathological process of the central nervous system (CNS) diseases and the suppression of TLR4 signal may become an effective treatment. TLR4-IN-C34, a TLR4 inhibitor, is expected to become a candidate compound with anti-neuroinflammatory response. In the present study, the anti-neuroinflammatory effects and possible mechanism of TLR4-IN-C34 were investigated in BV2 microglia cells stimulated by LPS. The results showed that TLR4-IN-C34 decreased the levels of pro-inflammatory factors and chemokines including NO, TNF-α, IL-1β, IL-6, and MCP-1 in the supernatant of LPS-stimulated BV2 cells. Further research indicated that TLR4-IN-C34 suppressed the expression or phosphorylation levels of inflammatory proteins regarding TLR4/MyD88/NF-κB/NLRP3 signaling pathway. In addition, TLR4-IN-C34 reduced ROS production in BV2 cells after LPS treatment. In conclusion, our findings suggest that anti-neuroinflammatory activity of TLR4-IN-C34 may be interrelated to the inhibition of TLR4/MyD88/NF-κB/NLRP3 signaling pathway and reduction of ROS generation.

Sodium alginate/collagen/stromal cell-derived factor-1 neural scaffold loaded with BMSCs promotes neurological function recovery after traumatic brain injury

Stem cell therapy is promising for neural repair in devastating traumatic brain injury (TBI). However, the low survival and differentiation rates of transplanted stem cells are main obstacles to efficient stem cell therapy in TBI. Stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 are key factors that regulate the survival, recruitment, and differentiation of stem cells. Herein, we synthesized a sodium alginate (SA)/collagen type I (Col)/SDF-1 hydrogel and investigated whether the SA/Col/SDF-1 hydrogel loaded with bone marrow-derived mesenchymal stem cells (BMSCs) had therapeutic effects on a TBI model. Our results showed that the SA/Col/SDF-1 scaffold could stably release SDF-1 and provide biocompatible and biodegradable microenvironment for the survival, migration, and neuronal differentiation of BMSCs in vitro. In a rat model of TBI, the SA/Col/SDF-1 hydrogel loaded with BMSCs significantly ameliorated motor and cognition dysfunction and relieved anxiety and depressive-like behaviors. In addition, the BMSCs/SA/Col/SDF-1 scaffold reduced brain lesions and neuronal cell death and mitigated neuroinflammation. Further studies demonstrated that the BMSCs/SA/Col/SDF-1 hydrogel promoted the migration of BMSCs in the lesions and partly enhanced neurogenesis by activating the SDF-1/CXCR4-mediated FAK/PI3K/AKT pathway. Taken together, our results indicate that the SA/Col/SDF-1 scaffold loaded with BMSCs exerts neuroreparative effects in a TBI rat model, and thus, it may serve as an alternative neural regeneration scaffold for brain injury repair. STATEMENT OF SIGNIFICANCE: Hydrogel facilitates the biological behaviors of transplanted stem cells for tissue regeneration. In this study, we synthesized sodium alginate (SA)/collagen type I (Col)/ scaffold to simultaneously deliver stromal cell derived factor-1 (SDF-1) and bone marrow mesenchymal stem cells (BMSCs) in a rat model of traumatic brain injury (TBI). We found that the SA/Col/SDF-1 hydrogel could continuously release SDF-1 and was conducive to the survival, migration and neuronal differentiation of BMSCs in vitro. In addition, the SA/Col/SDF-1 hydrogel loaded with BMSCs significantly ameliorated neurological deficits, mitigated neuroinflammation, promoted the recruitment of BMSCs and enhanced neurogenesis in TBI partly by activating the SDF-1/CXCR4-mediated FAK/PI3K/AKT pathway. Our results may serve as an alternative neural regeneration strategy for brain injury.

Muscle multiorgan crosstalk with MG53 as a myokine for tissue repair and regeneration

Through stress and injury to tissues, the cell membrane is damaged and can lead to cell death and a cascade of inflammatory events. Soluble factors that mitigate and repair membrane injury are important to normal homeostasis and are a potential therapeutic intervention for regenerative medicine. A myokine is a type of naturally occurring factors that come from muscle and have impact on remote organs. MG53, a tripartite motif-containing family protein, is such a myokine which has protective effects on lungs, kidneys, liver, heart, eye, and brain. Three mechanisms of action for the beneficial regenerative medicine potential of MG53 have been identified and consist of 1) repair of acute injury to the cellular membrane, 2) anti-inflammatory effects associated with chronic injuries, and 3) rejuvenation of stem cells for tissue regeneration. As such, MG53 has the potential to be a novel and effective regeneration medicine therapeutic.

PDGF-BB/SA/Dex injectable hydrogels accelerate BMSC-mediated functional full thickness skin wound repair by promoting angiogenesis

Wound healing is a well-orchestrated dynamic and interactive process, which needs a favorable microenvironment and suitable angiogenesis. Platelet derived growth factor-BB (PDGF-BB) plays a crucial role in wound healing. However, the short half-life of PDGF-BB limits its efficacy. In the present study, we successfully synthesized an injectable hydrogel with sodium alginate (SA) and dextran (Dex) as a delivery system to simultaneously deliver PDGF-BB and bone marrow-derived mesenchymal stem cells (BMSCs) in the wound. Our work demonstrates that the PDGF-BB protein enhanced the survival, migration and endothelial cell (EC) differentiation of BMSCs in vitro. The PDGF-BB/SA/Dex hydrogels could sustainably release PDGF-BB with excellent biocompatibility in vitro and in vivo. Besides, these composite hydrogels loaded with BMSCs could accelerate wound healing by improving epithelialization and collagen deposition. In addition, the PDGF-BB/SA/Dex hydrogels promoted the EC-differentiation of transplanted BMSCs and proliferation of hair follicle stem cells in the wound. Furthermore, the expressions of angiogenesis-specific markers, PDGFR-β, p-PI3K, p-Akt, and p-eNOS, were obviously increased in the PDGF-BB/SA/Dex/BMSCs group. In conclusion, the PDGF-BB/SA/Dex injectable hydrogels could accelerate BMSC-mediated skin wound healing by promoting angiogenesis via the activation of the PDGF-BB/PDGFR-β-mediated PI3K/Akt/eNOS pathway, which may provide a new therapeutic strategy for stem cell therapy in wound healing.

MG53 inhibits angiogenesis through regulating focal adhesion kinase signalling

Mitsugumin 53 (MG53), which is expressed predominantly in striated muscle, has been demonstrated to be a myokine/cardiokine secreted from striated muscle under specific conditions. The important roles of MG53 in non-striated muscle tissues have also been examined in multiple disease models. However, no previous study has implicated MG53 in the control of endothelial cell function. In order to explore the effects of MG53 on endothelial cells, human umbilical vein endothelial cells (HUVECs) were stimulated with recombinant human MG53 (rhMG53). Then, rhMG53 uptake, focal adhesion kinase (FAK)/Src/Akt/ERK1/2 signalling pathway activation, cell migration and tube formation were determined in vitro. The efficacy of rhMG53 in regulating angiogenesis was also detected in postnatal mouse retinas. The results demonstrated that rhMG53 directly entered into endothelial cells in a cholesterol-dependent manner. The uptake of rhMG53 directly bound to FAK in endothelial cells, which resulted in a significant decrease in FAK phosphorylation at Y397. Accompanied by the dephosphorylation of FAK, rhMG53 uncoupled FAK-Src interaction and reduced the phosphorylation of Src at Y416. Consequently, the activation of FAK/Src downstream signalling pathways, such as Akt and ERK1/2, was also significantly inhibited by rhMG53. Furthermore, rhMG53 remarkably decreased HUVEC migration and tube formation in vitro and postnatal mouse retinal angiogenesis in vivo. Taken together, these data indicate that rhMG53 inhibits angiogenesis through regulating FAK/Src/Akt/ERK1/2 signalling pathways. This may provide a novel molecular mechanism for the impaired angiogenesis in ischaemic diseases.