Crosstalk between adipocytes and M2 macrophages compensates for osteopenic phenotype in the Lrp5-deficient mice

A loss-of-function mutation in the Lrp5 gene in mice leads to a low bone mass disorder due to the inhibition of the canonical Wnt signaling pathway; however, the role of bone marrow microenvironment in mice with this mutation remains unclear. In this study, we evaluated proliferation and osteogenic potential of mouse osteoblasts using the MTT assay and Alizarin red staining. The levels of alkaline phosphatase, tartrate-resistant acid phosphatase, and adiponectin in culture supernatants were measured using the enzyme-linked immunosorbent assay. Osteoclast bone resorbing activity was evaluated by toluidine staining and the number and area of bone resorption pits were determined. We observed increased osteogenesis in osteoblasts co-cultured with the BM-derived myeloid cells compared to the osteoblasts cultured alone. Mice with global Lrp5 deletion had a relatively higher bone density compared to the mice carrying osteoblast/osteocyte-specific Lrp5 deletion. An increased frequency of M2 macrophages and reduced expression of inflammatory cytokines were detected in the myeloid cells derived from the bone marrow of mice with global Lrp5 deletion. Higher adipogenic potential and elevated levels of adiponectin in the global Lrp5 deletion mice contributed to the preferential M2 macrophage polarization. Here, we identified a novel systemic regulatory mechanism of bone formation and degradation in mice with global Lrp5 deletion. This mechanism depends on a crosstalk between the adipocytes and M2 macrophages in the bone marrow and is responsible for partly rescuing osteopenia developed as a result of decreased Wnt signaling.

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Adrenomedullin 2 improves bone regeneration in type 1 diabetic rats by restoring imbalanced macrophage polarization and impaired osteogenesis

10.21203/rs.3.rs-130211/v1 ◽

2020 ◽

Author(s):

Feng Wang ◽

Lingchi Kong ◽

Wenbo Wang ◽

Li Shi ◽

Mengwei Wang ◽

...

Keyword(s):

Bone Marrow ◽

Bone Regeneration ◽

Macrophage Polarization ◽

Osteogenic Potential ◽

Enzyme Linked Immunosorbent Assay ◽

Diabetic Patients ◽

M2 Macrophage ◽

Alizarin Red ◽

M1 Macrophage

Abstract Background Both advanced glycation end products (AGEs) and AGE-mediated M1 macrophage polarization contribute to bone marrow mesenchymal stem cell (BMSC) dysfunction, leading to impaired bone regeneration in type 1 diabetes mellitus (T1DM). Adrenomedullin 2 (ADM2), an endogenous bioactive peptide belonging to the calcitonin gene-related peptide family, exhibits various biological activities associated with the inhibition of inflammation and reduction of insulin resistance. However, the effects and underlying mechanisms of ADM2 in AGE-induced macrophage M1 polarization, BMSC dysfunction, and impaired bone regeneration remain poorly understood. Methods The polarization of bone marrow-derived macrophages was verified by flow cytometry analysis. In addition, alkaline phosphatase (ALP) staining, ALP activity detection, and alizarin red staining were performed to assess the osteogenesis of BMSCs. Quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting, and immunofluorescence staining were used to assess polarization markers, PPARγ/IκBα/NF-κB signaling, and osteogenic markers. In vivo, a distraction osteogenesis (DO) rat model with T1DM was established, and the tibia samples were collected at different time points for radiological, biomechanical, and histological analyses, to verify the effects of ADM2 in terms of bone regeneration and M2 polarization under diabetic conditions. Results ADM2 treatment reversed the M1 macrophage polarization induced by AGEs towards the M2 phenotype, which was partially achieved by the PPARγ-mediated inhibition of NF-κB signaling. The PPARγ inhibitor GW9662 significantly attenuated the effects of ADM2. Besides, ADM2 treatment improved the AGE-impaired osteogenic potential of BMSCs in vitro. Furthermore, ADM2 accelerated bone regeneration, as revealed by improved radiological and histological manifestations and biomechanical parameters, accompanied by improved M2 macrophage polarization in diabetic DO rats, and these effects were partially blocked by GW9662 administration. Conclusions These results indicate that ADM2 enhances diabetic bone regeneration during DO, by attenuating AGE-induced imbalance in macrophage polarization, partly through PPARγ/IκBα/NF-κB signaling, and improving AGE-impaired osteogenic differentiation of BMSCs simultaneously. These findings reveal that ADM2 may serve as a potential bioactive factor for promoting bone regeneration under diabetic conditions, and imply that management of inflammation and osteogenesis, in parallel, might be a promising therapeutic strategy for diabetic patients during DO treatment.

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Adrenomedullin 2 improves bone regeneration in type 1 diabetic rats by restoring imbalanced macrophage polarization and impaired osteogenesis

Stem Cell Research & Therapy ◽

10.1186/s13287-021-02368-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Feng Wang ◽

Lingchi Kong ◽

Wenbo Wang ◽

Li Shi ◽

Mengwei Wang ◽

...

Keyword(s):

Bone Marrow ◽

Bone Regeneration ◽

Macrophage Polarization ◽

Osteogenic Potential ◽

Enzyme Linked Immunosorbent Assay ◽

Diabetic Patients ◽

M2 Macrophage ◽

Alizarin Red ◽

M1 Macrophage

Abstract Background Both advanced glycation end products (AGEs) and AGE-mediated M1 macrophage polarization contribute to bone marrow mesenchymal stem cell (BMSC) dysfunction, leading to impaired bone regeneration in type 1 diabetes mellitus (T1DM). Adrenomedullin 2 (ADM2), an endogenous bioactive peptide belonging to the calcitonin gene-related peptide family, exhibits various biological activities associated with the inhibition of inflammation and reduction of insulin resistance. However, the effects and underlying mechanisms of ADM2 in AGE-induced macrophage M1 polarization, BMSC dysfunction, and impaired bone regeneration remain poorly understood. Methods The polarization of bone marrow-derived macrophages was verified using flow cytometry analysis. Alkaline phosphatase (ALP) staining, ALP activity detection, and alizarin red staining were performed to assess the osteogenesis of BMSCs. Quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting, and immunofluorescence staining were used to assess polarization markers, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling, and osteogenic markers. In vivo, a distraction osteogenesis (DO) rat model with T1DM was established, and tibia samples were collected at different time points for radiological, biomechanical, and histological analyses, to verify the effects of ADM2 on bone regeneration and M2 polarization under diabetic conditions. Results ADM2 treatment reversed AGE-induced M1 macrophage polarization towards the M2 phenotype, which was partially achieved by the peroxisome proliferator-activated receptor γ (PPARγ)-mediated inhibition of NF-κB signaling. The PPARγ inhibitor GW9662 significantly attenuated the effects of ADM2. Besides, ADM2 treatment improved the AGE-impaired osteogenic potential of BMSCs in vitro. Furthermore, ADM2 accelerated bone regeneration, as revealed by improved radiological and histological manifestations and biomechanical parameters, accompanied by improved M2 macrophage polarization in diabetic DO rats, and these effects were partially blocked by GW9662 administration. Conclusions These results indicate that ADM2 enhances diabetic bone regeneration during DO, by attenuating AGE-induced imbalances in macrophage polarization, partly through PPARγ/NF-κB signaling, and improving AGE-impaired osteogenic differentiation of BMSCs simultaneously. These findings reveal that ADM2 may serve as a potential bioactive factor for promoting bone regeneration under diabetic conditions, and imply that management of inflammation and osteogenesis, in parallel, may present a promising therapeutic strategy for diabetic patients during DO treatment.

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Melatonin restores osteoporosis-impaired osteogenic potential of bone marrow mesenchymal stem cells and alleviates bone loss through the HGF/PTEN/Wnt/β-catenin axis

Therapeutic Advances in Chronic Disease ◽

10.1177/2040622321995685 ◽

2021 ◽

Vol 12 ◽

pp. 204062232199568

Author(s):

Jun Zhang ◽

Guoliang Jia ◽

Pan Xue ◽

Zhengwei Li

Keyword(s):

Bone Marrow ◽

Bone Loss ◽

Osteogenic Differentiation ◽

Cell Counting ◽

Luciferase Reporter ◽

Osteogenic Potential ◽

Enzyme Linked Immunosorbent Assay ◽

Tartrate Resistant Acid Phosphatase ◽

Micro Computed Tomography ◽

Alizarin Red

Background: Previous studies reported that melatonin exerts its effect on mesenchymal stem cell (MSC) survival and differentiation into osteogenic and adipogenic lineage. In the current study we aimed to explore the effect of melatonin on osteoporosis and relevant mechanisms. Methods: Real-time qualitative polymerase chain reaction (RT-qPCR) and Western blot analysis were conducted to determine expression of HGF, PTEN, and osteoblast differentiation-related genes in ovariectomy (OVX)-induced osteoporosis mice and the isolated bone marrow MSCs (BMSCs). Pre-conditioning with melatonin (1 μmol/l, 10 μmol/l and 100 μmol/l) was carried out in OVX mice BMSCs. Bone microstructure was analyzed using micro-computed tomography and the contents of alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase 5b (TRAP5b) were detected by enzyme-linked immunosorbent assay in serum. BMSC proliferation was measured by cell-counting kit (CCK)-8 assay. Alizarin red S (ARS) staining and ALP activity assay were performed to assess BMSC mineralization and calcification. The activity of the Wnt/β-catenin pathway was evaluated by dual-luciferase reporter assay. Results: Melatonin prevented bone loss in OVX mice. Melatonin increased ALP expression and reduced TRAP5b expression. HGF and β-catenin were downregulated, while PTEN was upregulated in the femur of OVX mice. Melatonin elevated HGF expression and then stimulated BMSC proliferation and osteogenic differentiation. Additionally, HGF diminished the expression of PTEN, resulting in activated Wnt/β-catenin pathway both in vitro and in vivo. Furthermore, melatonin was shown to ameliorate osteoporosis in OVX mice via the HGF/ PTEN/ Wnt/β-catenin axis. Conclusion: Melatonin could potentially enhance osteogenic differentiation of BMSCs and retard bone loss through the HGF/ PTEN/ Wnt/β-catenin axis.

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Lung Tumor Cell-Derived Exosomes Promote M2 Macrophage Polarization

Cells ◽

10.3390/cells9051303 ◽

2020 ◽

Vol 9 (5) ◽

pp. 1303 ◽

Cited By ~ 2

Author(s):

Alexandra Pritchard ◽

Sultan Tousif ◽

Yong Wang ◽

Kenneth Hough ◽

Saad Khan ◽

...

Keyword(s):

Bone Marrow ◽

Tumor Cells ◽

Bone Marrow Cells ◽

Lung Tumor ◽

Macrophage Polarization ◽

M2 Macrophage ◽

M2 Macrophages ◽

M2 Macrophage Polarization ◽

The Impact ◽

M2 Phenotype

Cellular cross-talk within the tumor microenvironment (TME) by exosomes is known to promote tumor progression. Tumor promoting macrophages with an M2 phenotype are suppressors of anti-tumor immunity. However, the impact of tumor-derived exosomes in modulating macrophage polarization in the lung TME is largely unknown. Herein, we investigated if lung tumor-derived exosomes alter transcriptional and bioenergetic signatures of M0 macrophages and polarize them to an M2 phenotype. The concentration of exosomes produced by p53 null H358 lung tumor cells was significantly reduced compared to A549 (p53 wild-type) lung tumor cells, consistent with p53-mediated regulation of exosome production. In co-culture studies, M0 macrophages internalized tumor-derived exosomes, and differentiated into M2 phenotype. Importantly, we demonstrate that tumor-derived exosomes enhance the oxygen consumption rate of macrophages, altering their bioenergetic state consistent with that of M2 macrophages. In vitro co-cultures of M0 macrophages with H358 exosomes demonstrated that exosome-induced M2 polarization may be p53 independent. Murine bone marrow cells and bone marrow-derived myeloid-derived suppressor cells (MDSCs) co-cultured with lewis lung carcinoma (LLC)-derived exosomes differentiated to M2 macrophages. Collectively, these studies provide evidence for a novel role for lung tumor-exosomes in M2 macrophage polarization, which then offers new therapeutic targets for immunotherapy of lung cancer.

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Montelukast, a Cysteinyl Leukotriene Receptor 1 Antagonist, Induces M2 Macrophage Polarization and Inhibits Murine Aortic Aneurysm Formation

BioMed Research International ◽

10.1155/2019/9104680 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 2

Author(s):

Yohei Kawai ◽

Yuji Narita ◽

Aika Yamawaki-Ogata ◽

Akihiko Usui ◽

Kimihiro Komori

Keyword(s):

Aortic Aneurysm ◽

Macrophage Polarization ◽

Enzyme Linked Immunosorbent Assay ◽

M2 Macrophage ◽

M2 Macrophages ◽

Gene Expressions ◽

Arginase 1 ◽

M2 Macrophage Polarization

Background. The pathogenesis of abdominal aortic aneurysm (AAA) is characterized by atherosclerosis with chronic inflammation in the aortic wall. Montelukast is a selective cys-LT 1 receptor antagonist that can suppress atherosclerotic diseases. We evaluated the in vitro properties of montelukast and its in vivo activities in an angiotensin II–infused apolipoprotein E–deficient (apoE−/−) AAA mouse model. Methods. The mouse monocyte/macrophage cell line J774A.1 was used in vitro. M1 macrophages were treated with montelukast, and gene expressions of inflammatory cytokines were measured. Macrophages were cultured with montelukast, then gene expressions of arginase-1 and IL (interleukin)-10 were assessed by quantitative polymerase chain reaction, arginase-1 was measured by fluorescence-activated cell sorting, and IL-10 concentration was analyzed by enzyme-linked immunosorbent assay. In vivo, one group (Mont, n=7) received oral montelukast (10 mg/kg/day) for 28 days, and the other group (Saline, n=7) was given normal Saline as a control for the same period. Aortic diameters, activities of matrix metalloproteinases (MMPs), cytokine concentrations, and the number of M2 macrophages were analyzed. Results. Relative to control, montelukast significantly suppressed gene expressions of MMP-2, MMP-9, and IL-1β, induced gene expressions of arginase-1 and IL-10, enhanced the expression of the arginase-1 cell surface protein, and increased the protein concentration of IL-10. In vivo, montelukast significantly decreased aortic expansion (Saline vs Mont; 2.44 ± 0.15 mm vs 1.59 ± 0.20 mm, P<.01), reduced MMP-2 activity (Saline vs Mont; 1240 μM vs 755 μM, P<.05), and induced infiltration of M2 macrophages (Saline vs Mont; 7.51 % vs 14.7 %, P<.05). Conclusion. Montelukast induces M2 macrophage polarization and prevents AAA formation in apoE−/− mice.

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Nucleolin Improves Heart Function During Recovery From Myocardial Infarction by Modulating Macrophage Polarization

Journal of Cardiovascular Pharmacology and Therapeutics ◽

10.1177/1074248421989570 ◽

2021 ◽

pp. 107424842198957

Author(s):

Yuting Tang ◽

Xiaofang Lin ◽

Cheng Chen ◽

Zhongyi Tong ◽

Hui Sun ◽

...

Keyword(s):

Myocardial Infarction ◽

Early Phase ◽

Heart Function ◽

Macrophage Polarization ◽

Late Phase ◽

Macrophage Infiltration ◽

Enzyme Linked Immunosorbent Assay ◽

M2 Macrophage ◽

M2 Macrophage Polarization ◽

Nucleolin Expression

Background: Nucleolin has multiple functions within cell survival and proliferation pathways. Our previous studies have revealed that nucleolin can significantly reduce myocardial ischemia-reperfusion injury by promoting myocardial angiogenesis and reducing myocardial apoptosis. In this study, we attempted to determine the role of nucleolin in myocardial infarction (MI) injury recovery and the underlying mechanism. Methods: Male BALB/c mice aged 6–8 weeks were used to set up MI models by ligating the left anterior descending coronary artery. Nucleolin expression in the heart was downregulated by intramyocardial injection of a lentiviral vector expressing nucleolin-specific small interfering RNA. Macrophage infiltration and polarization were measured by real-time polymerase chain reaction, flow cytometry, and immunofluorescence. Cytokines were detected by enzyme-linked immunosorbent assay. Results: Nucleolin expression in myocardium after MI induction decreased a lot at early phase and elevated at late phase. Nucleolin knockdown impaired heart systolic and diastolic functions and decreased the survival rate after MI. Macrophage infiltration increased in the myocardium after MI. Most macrophages belonged to the M1 phenotype at early phase (2 days) and the M2 phenotype increased greatly at late phase after MI. Nucleolin knockdown in the myocardium led to a decrease in M2 macrophage polarization with no effect on macrophage infiltration after MI. Furthermore, Notch3 and STAT6, key regulators of M2 macrophage polarization, were upregulated by nucleolin in RAW 264.7 macrophages. Conclusions: Lack of nucleolin impaired heart function during recovery after MI by reducing M2 macrophage polarization. This finding probably points to a new therapeutic option for ischemic heart disease.

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Analysis of the Influence of Jaw Periosteal Cells on Macrophages Phenotype Using an Innovative Horizontal Coculture System

Biomedicines ◽

10.3390/biomedicines9121753 ◽

2021 ◽

Vol 9 (12) ◽

pp. 1753

Author(s):

Fang He ◽

Felix Umrath ◽

Christiane von Ohle ◽

Siegmar Reinert ◽

Dorothea Alexander

Keyword(s):

Macrophage Polarization ◽

Maxillofacial Surgery ◽

Inflammatory Factors ◽

Osteogenic Potential ◽

Oral And Maxillofacial Surgery ◽

M2 Macrophage ◽

Macrophage Phenotype ◽

Flow Cytometric ◽

Coculture System ◽

Gene And Protein Expression

Jaw periosteum-derived mesenchymal stem cells (JPCs) represent a promising cell source for bone tissue engineering in oral and maxillofacial surgery due to their high osteogenic potential and good accessibility. Our previous work demonstrated that JPCs are able to regulate THP-1-derived macrophage polarization in a direct coculture model. In the present study, we used an innovative horizontal coculture system in order to understand the underlying paracrine effects of JPCs on macrophage phenotype polarization. Therefore, JPCs and THP-1-derived M1/M2 macrophages were cocultured in parallel chambers under the same conditions. After five days of horizontal coculture, flow cytometric, gene and protein expression analyses revealed inhibitory effects on costimulatory and proinflammatory molecules/factors as well as activating effects on anti-inflammatory factors in M1 macrophages, originating from multiple cytokines/chemokines released by untreated and osteogenically induced JPCs. A flow cytometric assessment of DNA synthesis reflected significantly decreased numbers of proliferating M1/M2 cells when cocultured with JPCs. In this study, we demonstrated that untreated and osteogenically induced JPCs are able to switch macrophage polarization from a classical M1 to an alternative M2-specific phenotype by paracrine secretion, and by inhibition of THP-1-derived M1/M2 macrophage proliferation.

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Macrophage Polarization in the Skin Lesion Caused by Neotropical Species of Leishmania sp

Journal of Immunology Research ◽

10.1155/2021/5596876 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Carmen M. Sandoval Pacheco ◽

Gabriela V. Araujo Flores ◽

Kadir Gonzalez ◽

Claudia M. de Castro Gomes ◽

Luiz F. D. Passero ◽

...

Keyword(s):

Cutaneous Leishmaniasis ◽

Macrophage Polarization ◽

Leishmania Species ◽

Skin Lesions ◽

Host Cells ◽

M2 Macrophage ◽

M2 Macrophages ◽

Intracellular Parasites ◽

Skin Biopsies ◽

Acquired Immune Responses

Macrophages play important roles in the innate and acquired immune responses against Leishmania parasites. Depending on the subset and activation status, macrophages may eliminate intracellular parasites; however, these host cells also can offer a safe environment for Leishmania replication. In this sense, the fate of the parasite may be influenced by the phenotype of the infected macrophage, linked to the subtype of classically activated (M1) or alternatively activated (M2) macrophages. In the present study, M1 and M2 macrophage subsets were analyzed by double-staining immunohistochemistry in skin biopsies from patients with American cutaneous leishmaniasis (ACL) caused by L. (L.) amazonensis, L. (V.) braziliensis, L. (V.) panamensis ,and L. (L.) infantum chagasi. High number of M1 macrophages was detected in nonulcerated cutaneous leishmaniasis (NUCL) caused by L. (L.) infantum chagasi ( M 1 = 112 ± 12 , M 2 = 43 ± 12 cells/mm2). On the other side, high density of M2 macrophages was observed in the skin lesions of patients with anergic diffuse cutaneous leishmaniasis (ADCL) ( M 1 = 195 ± 25 , M 2 = 616 ± 114 ), followed by cases of localized cutaneous leishmaniasis (LCL) caused by L. (L.) amazonensis ( M 1 = 97 ± 24 , M 2 = 219 ± 29 ), L. (V.) panamensis ( M 1 = 71 ± 14 , M 2 = 164 ± 14 ), and L. (V.) braziliensis ( M 1 = 50 ± 13 , M 2 = 53 ± 10 ); however, low density of M2 macrophages was observed in NUCL. The data presented herein show the polarization of macrophages in skin lesions caused by different Leishmania species that may be related with the outcome of the disease.

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The effect of the WKYMVm peptide on promoting mBMSC secretion of exosomes to induce M2 macrophage polarization through the FPR2 pathway

Journal of Orthopaedic Surgery and Research ◽

10.1186/s13018-021-02321-9 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Wenbo Zhao ◽

Junxian Hu ◽

Qingyi He

Keyword(s):

Western Blotting ◽

Macrophage Polarization ◽

Bone Defects ◽

The Other ◽

Formyl Peptide Receptor ◽

Cell Counting ◽

M2 Macrophage ◽

M2 Macrophages ◽

Lysosomal Activity ◽

M2 Macrophage Polarization

Abstract Background When multicystic vesicles (precursors of exosomes) are formed in cells, there are two results. One is decomposition by lysosomes, and the other is the generation of exosomes that are transported out through the transmembrane. On the other hand, M2 macrophages promote the formation of local vascularization and provide necessary support for the repair of bone defects. To provide a new idea for the treatment of bone defects, the purpose of our study was to investigate the effect of WKYMVm (Trp-Lys-Tyr-Met-Val-D-Met-NH2) peptide on the secretion of exosomes from murine bone marrow-derived MSCs (mBMSCs) and the effect of exosomes on the polarization of M2 macrophages. Methods The WKYMVm peptide was used to activate the formyl peptide receptor 2 (FPR2) pathway in mBMSCs. First, we used Cell Counting Kit-8 (CCK-8) to detect the cytotoxic effect of WKYMVm peptide on mBMSCs. Second, we used western blotting (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) to detect the expression of interferon stimulated gene 15 (ISG15) and transcription factor EB (TFEB) in mBMSCs. Then, we detected lysosomal activity using a lysozyme activity assay kit. Third, we used an exosome extraction kit and western blotting to detect the content of exosomes secreted by mBMSCs. Fourth, we used immunofluorescence and western blotting to count the number of polarized M2 macrophages. Finally, we used an inhibitor to block miRNA-146 in exosomes secreted by mBMSCs and counted the number of polarized M2 macrophages. Results We first found that the WKYMVm peptide had no toxic effect on mBMSCs at a concentration of 1 μmol/L. Second, we found that when the FPR2 pathway was activated by the WKYMVm peptide in mBMSCs, ISG15 and TFEB expression was decreased, leading to increased secretion of exosomes. We also found that lysosomal activity was decreased when the FPR2 pathway was activated by the WKYMVm peptide in mBMSCs. Third, we demonstrated that exosomes secreted by mBMSCs promote the polarization of M2 macrophages. Moreover, all these effects can be blocked by the WRWWWW (WRW4, H-Trp-Arg-Trp-Trp-Trp-Trp-OH) peptide, an inhibitor of the FPR2 pathway. Finally, we confirmed the effect of miRNA-146 in exosomes secreted by mBMSCs on promoting the polarization of M2 macrophages. Conclusion Our findings demonstrated the potential value of the WKYMVm peptide in promoting the secretion of exosomes by mBMSCs and eventually leading to M2 macrophage polarization. We believe that our study could provide a research basis for the clinical treatment of bone defects.

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Abstract 660: Macrophage Specific Deficiency of the Transient Receptor Potential Canonical 3 Channel Reduces Apoptosis and Necrosis in Advanced Atherosclerotic Plaques

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.660 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Sumeet A Solanki ◽

Guillermo Vazquez

Keyword(s):

Bone Marrow ◽

Transient Receptor Potential ◽

Receptor Potential ◽

Atherosclerotic Plaques ◽

M2 Macrophage ◽

M2 Macrophages ◽

M1 Macrophages ◽

Transient Receptor Potential Canonical ◽

Transient Receptor ◽

Apoptosis And Necrosis

Background: Macrophage apoptosis plays a critical role in progression of atherosclerosis. Previous studies suggest that M1 and M2 macrophage phenotypes dominate atherosclerosis. Recently, we showed that advanced lesions in the aortic root of Apoe -/- mice transplanted with bone marrow deficient in the calcium-permeable channel Transient Receptor Potential Canonical 3 (TRPC3) are characterized by reduced areas of necrosis and less apoptotic macrophages. However, the donor mice used in these studies had global deficiency of TRPC3, raising the question whether the observed phenotype was also contributed by TRPC3-deficient non-myeloid cells which could undermine the true impact of macrophage deletion of TRPC3. To address this important question, we generated mice with macrophage-specific loss of TRPC3 function (MacTrpc3 -/- ). Methods & results: 13 six week-old female Ldlr -/- mice were irradiated and transplanted with Ldlr -/- (control) or MacTrpc3 -/- Ldlr -/- (experimental) bone marrow and kept on high fat diet for 14 weeks. At the end of the diet period, aortic roots were sectioned and processed for atherosclerotic lesion analysis. Total lesion size (H&E), neutral lipid (Oil Red O) and macrophage content (CD68 staining) were not different between groups. However, we found a 1.7 fold decrease (P=0.01) in percent necrotic area in advanced lesions of MacTrpc3 -/- Ldlr -/- mice (23.12 ± 2.07%, n=10) compared to controls (39.63 ± 5.93%, n=10). Using in situ TUNEL we found that MacTrpc3 -/- Ldlr -/- lesions have less apoptotic cells compared to controls, and these overlapped with CD68 + areas. Using iNOS and mannose receptor as markers for M1 and M2 macrophages, respectively, we found that both subsets overlapped with CD68 + and TUNEL + positive areas, with no differences between groups (n=5). Previously, we showed that M1, but not M2 macrophages derived from MacTrpc3 -/- mice, had reduced apoptosis. This suggests that reduced plaque necrosis of MacTrpc3 -/- Ldlr -/- mice may be due to reduced apoptosis of M1 macrophages. In sum, these in vivo studies indicate that macrophage-specific deficiency of TRPC3 has a genuine beneficial effect on advanced atherosclerotic plaques, reducing apoptosis and necrosis, probably due to a selective effect of TRPC3 on M1 macrophages.

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