Genetic and Pharmacological Inhibition of Astrocytic Mysm1 Alleviates Depressive-Like Disorders by Promoting ATP Production.

Major depressive disorder (MDD) is a leading cause of disability worldwide. A comprehensive understanding of the molecular mechanisms of this disorder is critical for the therapy of MDD. In this study, it is observed that deubiquitinase Mysm1 is induced in the brain tissues from patients with major depression and from mice with depressive behaviors. The genetic silencing of astrocytic Mysm1 induced an antidepressant-like effect and alleviated the osteoporosis of depressive mice. Furthermore, it is found that Mysm1 knockdown led to increased ATP production and the activation of p53 and AMP-activated protein kinase (AMPK). Pifithrin α (PFT α) and Compound C, antagonists of p53 and AMPK, respectively, repressed ATP production and reversed the antidepressant effect of Mysm1 knockdown. Moreover, the pharmacological inhibition of astrocytic Mysm1 by aspirin relieved depressive-like behaviors in mice. The study reveals, for the first time, the important function of Mysm1 in the brain, highlighting astrocytic Mysm1 as a potential risk factor for depression and as a valuable target for drug discovery to treat depression.

Ectoderm-derived frontal bone mesenchymal stem cells promote traumatic brain injury recovery by alleviating neuroinflammation and glutamate excitotoxicity partially via FGF1.

BACKGROUND: Traumatic brain injury (TBI) leads to cell and tissue impairment, as well as functional deficits. Stem cells promote structural and functional recovery and thus are considered as a promising therapy for various nerve injuries. Here, we aimed to investigate the role of ectoderm-derived frontal bone mesenchymal stem cells (FbMSCs) in promoting cerebral repair and functional recovery in a murine TBI model. METHODS: A murine TBI model was established by injuring C57BL/6 N mice with moderate-controlled cortical impact to evaluate the extent of brain damage and behavioral deficits. Ectoderm-derived FbMSCs were isolated from the frontal bone and their characteristics were assessed using multiple differentiation assays, flow cytometry and microarray analysis. Brain repairment and functional recovery were analyzed at different days post-injury with or without FbMSC application. Behavioral tests were performed to assess learning and memory improvements. RNA sequencing analysis, immunofluorescence staining, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) were used to examine inflammation reaction and neural regeneration. In vitro co-culture analysis and quantification of glutamate transportation were carried out to explore the possible mechanism of neurogenesis and functional recovery promoted by FbMSCs. RESULTS: Ectoderm-derived FbMSCs showed fibroblast like morphology and osteogenic differentiation capacity. FbMSCs were CD105, CD29 positive and CD45, CD31 negative. Different from mesoderm-derived MSCs, FbMSCs expressed the ectoderm-specific transcription factor Tfap2ß. TBI mice showed impaired learning and memory deficits. Microglia and astrocyte activation, as well as neural damage, were significantly increased post-injury. FbMSC application ameliorated the behavioral deficits of TBI mice and promoted neural regeneration. RNA sequencing analysis showed that signal pathways related to inflammation decreased, whereas those related to neural activation increased. Immunofluorescence staining and qRT-PCR data revealed that microglial activation and astrocyte polarization to the A1 phenotype were suppressed by FbMSC application. In addition, FGF1 secreted from FbMSCs enhanced glutamate transportation by astrocytes and alleviated the cytotoxic effect of excessive glutamate on neurons. CONCLUSIONS: Ectoderm-derived FbMSC application significantly alleviated neuroinflammation, brain injury, and excitatory toxicity to neurons, improved cognition and behavioral deficits in TBI mice. Therefore, ectoderm-derived FbMSCs could be ideal therapeutic candidates for TBI which mostly affect cells from the same embryonic origins as FbMSCs.

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

OBJECTIVE: Accumulating evidence indicates that microRNAs (miRNAs) play crucial roles in osteogenic differentiation. However, the associated mechanisms remain elusive. This paper is aimed at exploring the role of miR-129-5p in regulating bone marrow mesenchymal stem cell (BMSC) differentiation and bone regeneration in vivo and in vitro. METHODS: BMSCs were transduced by miR-129-5p mimic, miR-129-5p inhibitor, and negative control lentivirus. The ability of BMSC differentiation to osteoblast was tested by alkaline phosphatase (ALP) and alizarin red staining (ARS). The expression of osteogenic genes (Runx2, Bmp2, and OCN) was examined via quantitative RT-PCR and western blot. A mouse model of calvaria defect was investigated by Micro-CT, immunohistochemistry, and histological examination. The luciferase reporter gene assay was performed to confirm the binding between Dkk3 and miR-129-5p. For the transfection experiments, lipofectamine 3000 was used to transfect pcDNA-Dkk3 into BMSCs to overexpress Dkk3. Coimmunoprecipitation and immunofluorescent localization assay were included for exploring the role of Dkk3 and ß-catenin. RESULTS: miR-129-5p was induced in BMSCs and MSC cell line C3H10T1/2 cells under osteogenic medium. Overexpression of miR-129-5p significantly promoted osteogenic differentiation of BMSCs in vitro. Moreover, BMSCs transduced with miR-129-5p mimic exhibited better bone regeneration compared with BMSCs transduced with control counterpart in vivo. Luciferase and western blot data showed that Dickkopf3 (Dkk3) is a target gene of miR-129-5p and the expression of Dkk3 was inhibited in BMSCs transduced with miR-129-5p mimic but enhanced in BMSCs transduced with miR-129-5p inhibitor. In addition, Dkk3 interacted with ß-catenin directly. CONCLUSIONS: miR-129-5p promotes osteogenic differentiation of BMSCs and bone regeneration, and miR-129-5p/Dkk3 axis may be new potential targets for the treatment of bone defect and bone loss.

KLF2 Protects against Osteoarthritis by Repressing Oxidative Response through Activation of Nrf2/ARE Signaling In Vitro and In Vivo.

Osteoarthritis (OA) is a multifactorial and inflammatory disease characterized by cartilage destruction that can cause disability among aging patients. There is currently no effective treatment that can arrest or reverse OA progression. Kruppel-like factor 2 (KLF2), a member of the zinc finger family, has emerged as a transcription factor involved in a wide variety of inflammatory diseases. Here, we identified that KLF2 expression is downregulated in IL-1ß-treated human chondrocytes and OA cartilage. Genetic and pharmacological overexpression of KLF2 suppressed IL-1ß-induced apoptosis and matrix degradation through the suppression of reactive oxygen species (ROS) production. In addition, KLF2 overexpression resulted in increased expression of heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) through the enhanced nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). Further, Nrf2 inhibition abrogated the chondroprotective effects of KLF2. Safranin O/fast green and TUNEL staining demonstrated that adenovirus-mediated overexpression of KLF2 in joint cartilage protects rats against experimental OA by inhibiting cartilage degradation and chondrocyte apoptosis. Immunohistochemical staining revealed that KLF2 overexpression significantly decreases MMP13 expression caused by OA progression in vivo. This in vitro and in vivo study is the first to investigate the antioxidative effect and mechanisms of KLF2 in OA pathogenesis. Our results collectively provide new insights into OA pathogenesis regulated by KLF2 and a rationale for the development of effective OA intervention strategies.

Silencing of carboxypeptidase E inhibits cell proliferation, tumorigenicity, and metastasis of osteosarcoma cells.

Carboxypeptidase E (CPE), a prohormone processing enzyme, has been implicated in the progression of multiple malignancies. However, the biological role and molecular mechanisms of CPE in osteosarcoma remain elusive. In this study, we assessed the effects of CPE on cell proliferation, tumorigenicity, migration, and invasion in osteosarcoma. Our results showed that silencing of CPE significantly inhibited cell proliferation, caused cell cycle arrest at G0/G1 phase, decreased the expression levels of cell cycle protein, cyclin D1, and inhibited tumorigenicity in vivo. Additionally, CPE downregulation repressed the migratory and invasive capacities of osteosarcoma cells in vitro. Furthermore, overexpression of CPE-ΔN (a splice variant of CPE) enhanced the cell growth, migration, and invasion of osteosarcoma cells. It is possible that both CPE forms are involved in the tumorigenesis and development of osteosarcoma, and therefore CPE may provide a promising biological target for osteosarcoma therapy.