Biomimetic Nano-Degrader Based CD47-SIRPα Immune Checkpoint Inhibition Promotes Macrophage Efferocytosis for Cardiac Repair.

CD47-SIRPα axis is an immunotherapeutic target in tumor therapy. However, current monoclonal antibody targeting CD47-SIRPα axis is associated with on-target off-tumor and antigen sink effects, which significantly limit its potential clinical application. Herein, a biomimetic nano-degrader is developed to inhibit CD47-SIRPα axis in a site-specific manner through SIRPα degradation, and its efficacy in acute myocardial infarction (AMI) is evaluated. The nano-degrader is constructed by hybridizing liposome with red blood cell (RBC) membrane (RLP), which mimics the CD47 density of senescent RBCs and possesses a natural high-affinity binding capability to SIRPα on macrophages without signaling capacity. RLP would bind with SIRPα and induce its lysosomal degradation through receptor-mediated endocytosis. To enhance its tissue specificity, Ly6G antibody conjugation (aRLP) is applied, enabling its attachment to neutrophils and accumulation within inflammatory sites. In the myocardial infarction model, aRLP accumulated in the infarcted myocardium blocks CD47-SIRPα axis and subsequently promoted the efferocytosis of apoptotic cardiomyocytes by macrophage, improved heart repair. This nano-degrader efficiently degraded SIRPα in lysosomes, providing a new strategy for immunotherapy with great clinical transformation potential.

Genetically Engineered Macrophages Co-Loaded with CD47 Inhibitors Synergistically Reconstruct Efferocytosis and Improve Cardiac Remodeling Post Myocardial Ischemia Reperfusion Injury.

Efferocytosis, mediated by the macrophage receptor MerTK (myeloid-epithelial-reproductive tyrosine kinase), is a significant contributor to cardiac repair after myocardial ischemia-reperfusion (MI/R) injury. However, the death of resident cardiac macrophages (main effector cells), inactivation of MerTK （main effector receptor), and overexpression of "do not eat me" signals (brake signals, such as CD47), collectively lead to the impediment of efferocytosis in the post-MI/R heart. To date, therapeutic strategies targeting individual above obstacles are relatively lacking, let alone their effectiveness being limited due to constraints from the other concurrent two. Herein, inspired by the application research of chimeric antigen receptor macrophages (CAR-Ms) in solid tumors, a genetically modified macrophage-based synergistic drug delivery strategy that effectively challenging the three major barriers in an integrated manner is developed. This strategy involves the overexpression of exogenous macrophages with CCR2 (C-C chemokine receptor type 2) and cleavage-resistant MerTK, as well as surface clicking with liposomal PEP-20 (a CD47 antagonist). In MI/R mice model, this synergistic strategy can effectively restore cardiac efferocytosis after intravenous injection, thereby alleviating the inflammatory response, ultimately preserving cardiac function. This therapy focuses on inhibiting the initiation and promoting active resolution of inflammation, providing new insights for immune-regulatory therapy.

Biomimetic and NOS-Responsive Nanomotor Deeply Delivery a Combination of MSC-EV and Mitochondrial ROS Scavenger and Promote Heart Repair and Regeneration.

Mesenchymal stem cell-derived extracellular vesicle (MSC-EV) is shown to promote cardiac repair, however, it still falls short in initiating myocardia proliferation restart. In this regard, ROS-induced DNA damage and responses are the culprit of cellcycle arrest. Here, this work constructs a hybrid cell-derived extracellular vesicle that is composed of MSC and macrophage membranes and encompasses MitoN, a ROS scavenger, to boost the healing of the heart. The MitoN, a NAD(P)H mimic, could target the mitochondrial to eliminate the ROS resuming the arrested cell cycle. The hybrid extracellular vesicle (N@MEV) could respond to the inflammatory signals generated during myocardial injury and thus enable superior targeting and enrichment to the location of the damage. L-arginine, which could be catalyzed by NOS and ROS into NO and SO provide a driving force, is immobilized within the vesicle (NA@MEV) to further enhance the N@MEV's potential to penetrate the cardiac stroma. In combination with multiple mechanisms, NA@MEV increased heart function 1.3-fold EF% versus MSC-EV in mouse myocardial injury model. A more in-depth mechanistic study found that the NA@MEV could modulate M2 macrophage; promote angiogenesis; reduce DNA damage and response, and thereby restart cardiomyocyte proliferation. Thus, this combined therapy shows synthetic effects in heart repair and regeneration.

Targeted immunomodulation therapy for cardiac repair by platelet membrane engineering extracellular vesicles via hitching peripheral monocytes.

Immune regulation therapies have been considered promising in the treatment of myocardial ischemia reperfusion (MI/R) injury. Mesenchymal stem cells derived extracellular vesicles (MSC-EVs) are of great potential for immune modulation by reprogramming macrophages but their therapeutic efficacy is hindered by insufficient targeting ability in vivo. Herein, we introduced the platelet membrane modified EVs (P-EVs) based on membrane fusion method to mimic the binding ability of platelets to monocytes. In the mouse model of MI/R injury, the intravenously injected P-EVs were mainly carried by circulating monocytes into the ischemic myocardium. In the inflammatory microenvironment, those monocytes subsequently differentiated into macrophages with enhanced phagocytosis, which probably promoted in-situ endocytosis of the superficial P-EVs by monocytes differentiated macrophages in large quantities. Then, the P-EVs successfully escaped from the macrophage lysosome and released the functional microRNAs (miRNAs) into the cytosol which facilitated the inflammatory macrophages (M1 phenotype) reprogramming to reparative macrophages (M2 phenotype). Finally, the immune microenvironment was regulated to realize cardiac repair. Thus, we supposed that the most likely delivery method was that monocytes mediated P-EVs migration into ischemic myocardium where P-EVs were mainly in-situ endocytosed by monocytes derived macrophages, which holds potential for immunoregulation on MI/R and other immune-related diseases in the future.

Platelet-Like Fusogenic Liposome-Mediated Targeting Delivery of miR-21 Improves Myocardial Remodeling by Reprogramming Macrophages Post Myocardial Ischemia-Reperfusion Injury.

Inflammatory modulations focusing on macrophage phenotype are promising candidates to promote better cardiac healing post myocardial ischemia-reperfusion (MI/R) injury. However, the peak of monocyte/macrophage recruitment is later than the time when enhanced permeability and retention effect disappears, which greatly increases the difficulty of reprogramming macrophages through systemic administration. Meanwhile, the inability of nanomaterials to release their contents to specific intracellular locations through reasonable cellular internalization pathways is another obstacle to achieving macrophage reprogramming. Here, inspired by the increase in circulating platelet-monocyte aggregates in patients' post-MI/R and the high efficiency of fusogenic liposomes to deliver contents to the cytoplasm of target cells, a platelet-like fusogenic liposome (PLPs) is constructed. Under the coating of PLPs, mesoporous silica nanospheres with a payload of miR-21, an anti-inflammatory agent, can be specifically delivered to inflammatory monocytes in the blood circulation of MI/R induced mice. Then it directly enters the cytoplasm of monocytes through membrane fusion, thereby realizing the reparative reprogramming of the inflamed macrophages derived from it. In vivo administration of the resulting formula can effectively preserve the cardiac function of mice undergone MI/R. Minimal invasiveness and biological safety make this nano-platform a promising approach of immunotherapy.

Nonhypertensive male with multiple paragangliomas of the heart and neck: A case report.

BACKGROUND: Paraganglioma is a rare disease that can be lethal if undiagnosed. Thus, quick recognition is very important. Cardiac paragangliomas are found in patients who have hypertension. The classic symptoms are the triad of headaches, palpitations, and profuse sweating. We describe a very rare case of multiple paragangliomas of the heart and bilateral carotid artery without hypertension and outline the management strategies for this disease. CASE SUMMARY: A 46-year-old man presented with the chief complaint of recently recurrent chest pain with a history of hemangioma of the bilateral carotid artery that had been surgically removed. He was found to have an intracardiac mass in the right atrioventricular groove and underwent successful excision. The final pathology demonstrated that the intracardiac mass was a cardiac paraganglioma, and the patient had an increased level of normetanephrine in the blood. The pathology and immunohistochemistry results showed that the bilateral carotid masses were also paragangliomas. During the 3 mo follow-up period, the patient did not experience recurrence of chest pain. CONCLUSION: To our knowledge, this is the first case of multiple paragangliomas of the heart and neck without hypertension. This rare disease can be lethal if left undiagnosed. Thus, quick recognition is very important. The key to the diagnosis of cardiac paraganglioma is the presence of typical symptoms, including headaches, palpitations, profuse sweating, hypertension, and chest pain. Radiology can demonstrate the intracardiac mass. It is important to determine the levels of normetanephrine in the blood. The detection of genetic mutations is also recommended. Surgical resection is necessary to treat the disease and obtain pathological evidence.

Monocyte mimics improve mesenchymal stem cell-derived extracellular vesicle homing in a mouse MI/RI model.

Stem cell-derived extracellular vesicles (EVs) have been demonstrated to be effective in heart repair and regeneration post infarction. However, the poor homing efficiency and low yields of these therapeutics remain the major obstacles before they can be used in the clinic. To improve the delivery efficiency of EVs to ischemia-injured myocardium, we modified mesenchymal stem cell (MSC)-derived EVs with monocyte mimics through the method of membrane fusion. Monocyte mimic-bioinspired MSC-EVs (Mon-Exos) exhibited enhanced targeting efficiency to injured myocardium by mimicking the recruitment feature of monocytes after MI/RI, thus contributing to these exclusive adhesive molecules on monocyte mimics, particularly the Mac1/LFA1-ICAM-1 interaction. Through this strategy, Mon-Exos were shown to promote endothelial maturation during angiogenesis and modulate macrophage subpopulations after MI/RI, consistent with MSC-Exos biofunctions, and eventually improve therapeutic outcomes in cardiac function and pathohistology changes after treatments in a mouse MI/RI model. Ultimately, this strategy might provide us with a better way to assess the effects of stem cell EVs and offer additional techniques to help clinicians better manage regenerative therapeutics for ischemic heart diseases.

The preservation effect of coronary collateral circulation on left ventricular function in chronic total occlusion and its association with the expression of vascular endothelial growth factor A.

BACKGROUND: Patients with coronary chronic total occlusion (CTO) typically have collateralization of the distal vessel, and these collaterals can contribute to the relief of ischemia and anginal symptoms and to the preservation of ventricular function. OBJECTIVES: To investigate the preservation effect of coronary collateral circulation on left ventricular (LV) function in coronary CTO, and to explore the potential mechanism behind the development of coronary collateral circulation. MATERIAL AND METHODS: A total of 102 consecutive patients with coronary CTO were divided into 2 groups: the left ventricular ejection fraction (LVEF)-preserved group (LVEF ≥ 50%; n = 46) and the LVEF-decreased group (LVEF < 50%; n = 56). Clinical, angiographic and laboratory data was collected for all patients. The association between LVEF and coronary collateral circulation in coronary CTO patients was analyzed with multivariate logistic regression analysis, and the serum levels of VEGF-A and the mRNA expression levels of the VEGF-A gene were compared between different grades of coronary collateral circulation. RESULTS: Multivariate analysis revealed that Rentrop grades 2-3 and coexisting collateral pathways were independent predictors of LVEF preservation in coronary CTO patients. Patients with Rentrop grades 2-3 had smaller left ventricular end diastolic diameters (LVDd) and left ventricular end systolic diameters (LVSd), and they had larger LVEFs than the patients with Rentrop grades 0-1. Patients with Rentrop grades 2-3 also had higher serum levels of VEGF-A and higher mRNA expression levels of the VEGF-A gene in their peripheral blood mononuclear cells (PBMCs) than patients with Rentrop grades 0-1. Patients with coexisting collateral pathways had higher serum levels of VEGF-A and higher mRNA expression levels of the VEGF-A gene in PBMCs than patients without coexisting collateral pathways. CONCLUSIONS: Coronary collateral circulation is significantly associated with LVEF preservation, and VEGF-A might promote the formation of coronary collateral circulation.

M2 macrophage-derived exosomes carry microRNA-148a to alleviate myocardial ischemia/reperfusion injury via inhibiting TXNIP and the TLR4/NF-κB/NLRP3 inflammasome signaling pathway.

BACKGROUND: Reperfusion may cause injuries to the myocardium in ischemia situation. Emerging studies suggest that exosomes may serve as key mediators in myocardial ischemia/reperfusion (MI/R) injury. OBJECTIVE: The study was conducted to figure out the mechanism of M2 macrophage-derived exosomes (M2-exos) in MI/R injury with the involvement of microRNA-148a (miR-148a). METHODS AND RESULTS: M2 macrophages were prepared and M2-exos were collected and identified. Neonatal rat cardiomyocytes (NCMs) were extracted for in vitro hypoxia/reoxygenation (H/R) model establishment, while rat cardiac tissues were separated for in vivo MI/R model establishment. Differentially expressed miRNAs in NCMs and H/R-treated NCMs after M2-exos treatment were evaluated using microarray analysis. The target relation between miR-148a and thioredoxin-interacting protein (TXNIP) was identified using dual luciferase reporter gene assay. Gain- and loss- of function studies of miR-148a and TXNIP were performed to figure out their roles in MI/R injury. Meanwhile, the activation of the TLR4/NF-κB/NLRP3 inflammasome signaling pathway and pyroptosis of NCMs were evaluated. M2 macrophages carried miR-148a into NCMs. Over-expression of miR-148a enhanced viability of H/R-treated NCMs, reduced infarct size in vivo, and alleviated dysregulation of cardiac enzymes and Ca2+ overload in both models. miR-148a directly bound to the 3'-untranslated region (3'UTR) of TXNIP. Over-expressed TXNIP triggered the TLR4/NF-κB/NLRP3 signaling pathway activation and induced cell pyroptosis of NCMs, and the results were reproduced in in vivo studies. CONCLUSION: This study demonstrated that M2-exos could carry miR-148a to mitigate MI/R injury via down-regulating TXNIP and inactivating the TLR4/NF-κB/NLRP3 inflammasome signaling pathway. This study may offer new insights into MI/R injury treatment.

Co-loading antioxidant N-acetylcysteine attenuates cytotoxicity of iron oxide nanoparticles in hypoxia/reoxygenation cardiomyocytes.

PURPOSE: Myocardial delivery of magnetic iron oxide nanoparticles (MNPs) might produce iron overload-induced myocardial injury, and the oxidative stress was regarded as the main mechanism. Therefore, we speculated antioxidant modification might be a reasonable strategy to mitigate the toxicity of MNPs. METHODS AND RESULTS: Antioxidant N-acetylcysteine (NAC) was loaded into magnetic mesoporous silica coated Fe3O4 nanoparticles. Neonatal rat hypoxia/reoxygenation (H/R) cardiomyocytes were incubated with nanoparticles for 24 hrs. NAC can effectively mitigate iron-induced oxidative injury of cardiomyocytes, evidenced by reduced production of MDA, 8-iso-PGF2α, and 8-OHDG and maintained concentrations of SOD, CAT, GSH-Px, and GSH in ELISA and biochemical tests; downregulated expression of CHOP, GRP78, p62, and LC3-II proteins in Western Blot, and less cardiomyocytes apoptosis in flow cytometric analysis. CONCLUSIONS: NAC modifying could suppress the toxic effects of Fe3O4 nanoparticles in H/R cardiomyocytes model in vitro, indicating a promising strategy to improve the safety of iron oxide nanoparticles.

Modification with CREKA Improves Cell Retention in a Rat Model of Myocardial Ischemia Reperfusion.

Poor cell homing limits the efficacy of cardiac cellular therapy. The homing peptide, cysteine-arginine-glutamic acid-lysine-alanine (CREKA), targets fibrin effectively which is involved in the repair process of tissue injury. Here, we assessed if CREKA-modified stem cells had enhanced fibrin-mediated homing ability resulting in better functional recovery and structural preservation in a rat myocardial injury model. CREKA-modified mesenchymal stem cells (CREKA-MSCs) were obtained via membrane fusion with CREKA-modified liposomes. The fibrin targeting ability of CREKA-MSCs was examined both in vitro and in vivo. Under both static and flow conditions in vitro, CREKA significantly enhanced MSCs binding ability to fibrin clots (2.6- and 2.3-fold, respectively). CREKA-MSCs showed 6.5-fold higher accumulation than unmodified MSCs in injured rat myocardium one day after administration, resulting in better structural preservation and functional recovery. Fibrin is, therefore, a novel target for enhancing homing of transplanted cells to injured myocardium, and the delivery system of fibrin-targeting is on behalf of a universalizable platform technology for regenerative medicine. Stem Cells 2019;37:663-676.

Mineralocorticoid receptor deficiency improves the therapeutic effects of mesenchymal stem cells for myocardial infarction via enhanced cell survival.

The poor survival of stem cells seriously limits their therapeutic efficacy for myocardial infarction (MI). Mineralocorticoid receptor (MR) activation plays an important role in the pathogenesis of multiple cardiovascular diseases. Here, we examined whether MR silencing in bone marrow derived mesenchymal stem cells (MSCs) could improve MSCs' survival and enhance their cardioprotective effects in MI. MSCs from male Sprague-Dawley rats were transfected with adenoviral small interfering RNA to silence MR (siRNA-MR). MR silencing decreased hypoxia-induced MSCs' apoptosis, as demonstrated by Annexin V/7-AAD staining. The mechanisms contributing to the beneficial effects of MR depletion were associated with inhibiting intracellular reactive oxygen species production and increased Bcl-2/Bax ratio. In vivo study, 1 × 106 of MSCs with or without siRNA-MR were injected into rat hearts immediately after MI. Depletion of MR could improve the MSCs' survival significantly in infarcted myocardium, associated with more cardiac function improvement and smaller infarct size. Capillary density were also significantly higher in siRNA group with increased expression of vascular endothelial growth factor. Our study demonstrated that silencing MR promoted MSCs' survival and repair efficacy in ischaemic hearts. MR might be a potential target for enhancing the efficacy of cell therapy in ischaemic heart disease.

Uniform magnetic targeting of magnetic particles attracted by a new ferromagnetic biological patch.

A new non-toxic ferromagnetic biological patch (MBP) was designed in this paper. The MBP consisted of two external layers that were made of transparent silicone, and an internal layer that was made of a mixture of pure iron powder and silicon rubber. Finite-element analysis showed that the local inhomogeneous magnetic field (MF) around the MBP was generated when MBP was placed in a uniform MF. The local MF near the MBP varied with the uniform MF and shape of the MBP. Therefore, not only could the accumulation of paramagnetic particles be adjusted by controlling the strength of the uniform MF, but also the distribution of the paramagnetic particles could be improved with the different shape of the MBP. The relationship of the accumulation of paramagnetic particles or cells, magnetic flux density, and fluid velocity were studied through in vitro experiments and theoretical considerations. The accumulation of paramagnetic particles first increased with increment in the magnetic flux density of the uniform MF. But when the magnetic flux density of the uniform MF exceeded a specific value, the magnetic flux density of the MBP reached saturation, causing the accumulation of paramagnetic particles to fall. In addition, the adsorption morphology of magnetic particles or cells could be improved and the uniform distribution of magnetic particles could be achieved by changing the shape of the MBP. Also, MBP may be used as a new implant to attract magnetic drug carrier particles in magnetic drug targeting. Bioelectromagnetics. 39:98-107, 2018. © 2017 Wiley Periodicals, Inc.

Bone marrow CD34+ cell subset under induction of moderate stiffness of extracellular matrix after myocardial infarction facilitated endothelial lineage commitment in vitro.

BACKGROUND: The stiffness of the myocardial extracellular matrix (ECM) and the transplanted cell type are vitally important in promoting angiogenesis. However, the combined effect of the two factors remains uncertain. The purpose of this study is to investigate in vitro the combined effect of myocardial ECM stiffness postinfarction with a bone marrow-derived cell subset expressing or not expressing CD34 on endothelial lineage commitment. METHODS: Myocardial stiffness of the infarct zone was determined in mice at 1 h, 24 h, 7 days, 14 days, and 28 days after coronary artery ligation. Polyacrylamide (PA) gel substrates of different stiffnesses were prepared to mechanically mimic the myocardial ECM after infarction. Mouse bone marrow-derived CD34+ and CD34- cells were seeded on the flexible PA gels. The double-positive expression for DiI-acetylated low-density lipoprotein (acLDL) uptake and fluorescein isothiocyanate-Ulex europaeus agglutinin-1 (FITC-UEA-1) binding, the endothelial lineage antigens CD31, von Willebrand factor (vWF), Flk-1, and VE-cadherin, as well as cytoskeleton were measured by immunofluorescent staining on day 7. Cell apoptosis was evaluated by both immunofluorescent staining and flow cytometry at 24 h after culture. RESULTS: We found that the numbers of the CD34+ cell subset adherent to the flexible substrates (4-72 kPa) was much larger than that of the CD34- subset. More double-positive cells for DiI-acLDL uptake/FITC-UEA-1 binding were seen on the 42-kPa (moderately stiff) substrate, corresponding to the stiffness of myocardial ECM at 7-14 days postinfarction, compared with those on substrates of other stiffnesses. Similarly, the moderately stiff substrate showed benefits in promoting the positive expressions of the endothelial lineage markers CD31, vWF, Flk-1, and VE-cadherin. In addition, the cytoskeleton F-actin network within CD34+ cells was organized more significantly at the leading edge of the adherent cells on the moderately stiff (42 kPa) or stiff (72 kPa) substrates as compared with those on the soft (4 kPa and 15 kPa) substrates. Moreover, the moderately stiff or stiff substrates showed a lower percentage of cell apoptosis than the soft substrates. CONCLUSIONS: Infarcted myocardium-like ECM of moderate stiffness (42 kPa) more beneficially regulated the endothelial lineage commitment of a bone marrow-derived CD34+ subset. Thus, the combination of a CD34+ subset with a "suitable" ECM stiffness might be an optimized strategy for cell-based cardiac repair.

Histamine promotes the differentiation of macrophages from CD11b+ myeloid cells and formation of foam cells through a Stat6-dependent pathway.

BACKGROUND AND AIMS: The enzyme histidine decarboxylase (Hdc), which generates histamine, is highly expressed in CD11b+Gr-1+ myeloid cells that play a critical role in infection, inflammation and tumorigenesis. The aim of this study was to explore the role of Hdc-expressing CD11b+ myeloid cells or histamine in atherogenesis. METHODS: Hdc-EGFP bacterial artificial chromosome (BAC) transgenic reporter mice (Hdc-EGFP) were used to track Hdc expression during the development of atherosclerosis. The expression of EGFP fluorescence was examined by immunofluorescence staining in a variety of adult tissues. Wild-type (WT), Apoe knockout (Apoe-/-), Hdc knockout (Hdc-/-), and Stat6 knockout (Stat6-/-) mice were used. Serum concentration of histamine was determined with ELISA. Changes in subsets of immune cells were evaluated by flow cytometry (FACS). Non-invasive tracking of the expression of CD11b+ myeloid cells was tested using 125I-anti-CD11b SPECT/CT imaging in the early stages of atherogenesis. Microarray analysis and RT-PCR were applied to detect gene expressions while Western blot was used to assess protein levels. RESULTS: Using Hdc-EGFP transgenic mice, we demonstrated that Hdc+CD11b+ myeloid cells increase in the circulation in response to hypercholesterolemia and contribute to foam cell formation in atherosclerosis. Histamine deficiency in Hdc knockout (Hdc-/-) mice repressed the differentiation of CD11b+Ly6Chigh classically activated M1-type macrophages and CD11b+CD11c+ dendritic cells (DCs), which was associated with downregulation of signal transducer and activator of transcription 6 (Stat6) expression. Furthermore, the results of in vivo and in vitro studies demonstrated that histamine could promote macrophage differentiation and foam cell formation via the Stat6 signal. CONCLUSIONS: Modulation of histamine and Stat6-signaling may represent an attractive therapeutic strategy for the prevention or treatment of atherosclerosis.

Targeted delivery of thymosin beta 4 to the injured myocardium using CREKA-conjugated nanoparticles.

PURPOSE: Thymosin beta 4 (Tß4) has multiple beneficial facets for myocardial injury, but its efficiency is limited by the low local concentration within the infarct. Here, we established a Tß4 delivery system for cardiac repair based on the interaction between the abundant fibrin in the infarct zone and the fibrin-targeting moiety clot-binding peptide cysteine-arginine-glutamic acid-lysine-alanine (CREKA). METHODS AND RESULTS: CREKA and Tß4 were conjugated to nanoparticles (CNP-Tß4). In vitro binding test revealed that CNP-Tß4 had a significant binding ability to the surface of fibrin clots when compared to the control clots (NP-Tß4). Based on the validation of fibrin expression in the early stage of ischemia injury, CNP-Tß4 was intravenously administered to mice with acute myocardial ischemia-reperfusion injury. CNP-Tß4 revealed a stronger fibrin-targeting ability than the NP-Tß4 group and accumulated mainly in the infarcted area and colocalized with fibrin. Subsequently, treatment with CNP-Tß4 resulted in a better therapeutic effect. CONCLUSION: CRKEA modification favored Tß4 accumulation and retention in the infarcted region, leading to augmented functional benefits. Fibrin-targeting delivery system represents a generalizable platform technology for regenerative medicine.

Small molecule antidepressant amitriptyline protects hypoxia/reoxygenation-induced cardiomyocyte apoptosis through TrkA signaling pathway.

Hypoxia/reoxygenation (H/R) induced cardiomyocytes apoptosis is a major factor leading to cardiovascular diseases. In this study, we investigated the protective effect of small molecule antidepressant amitriptyline (AMP) in regulating H/R-induced apoptosis in neonatal mouse cardiomyocyte in culture. Cardiomyocytes of C57BL/6J mice were treated with H/R condition in vitro. Various concentration of AMP was added into culture 2h prior to H/R conditioning. Cardiomyocyte apoptosis was evaluated by TUNEL assay. AMP induced downstream signaling pathway proteins, including tropomyosin receptor kinase A receptor (TrkA), phosphor-TrkA (p-TrkA), protein kinase B (Akt) and phosphor-Akt (p-Akt) were probed by western blot. TrkA phosphorylation was then blocked by K252a to investigate whether TrkA was functionally involved in the protection of AMP in H/R-injured cardiomyocyte. We found that H/R condition induced significant cardiomyocyte death and apoptosis, whereas AMP pretreatment considerably rescued cardiomyocyte death and apoptosis. Western blot analysis showed AMP activated TrkA signaling pathway through the phosphorylation of TrkA/Akt proteins. We also found that application of K252a inhibited the phosphorylation of TrkA/Akt signaling pathway, and subsequently abolished the protective effect of AMP in H/R-induced apoptosis in cardiomyocyte. Thus, our study revealed that AMP, through the activation of TrkA/Akt signaling pathway, plays a protective role in regulating H/R-induced apoptosis in cardiomyocyte.

Nucleosome Assembly Protein 1-Like 1 (Nap1l1) Regulates the Proliferation of Murine Induced Pluripotent Stem Cells.

BACKGROUND/AIMS: To investigate whether nucleosome assembly protein 1-like 1 (Nap1l1) regulates the proliferation of induced pluripotent stem cells (iPSC) and the potential mechanisms. METHODS: Nap1l1-knockdown-iPSC and Nap1l1-overexpression-iPSC were constructed by transfection of lentiviral particles. The proliferation of iPSC was detected by MTT analysis, and cell cycle was analyzed by flow cytometry. RESULTS: Nap1l1 overexpression promoted iPSC proliferation and induced G2/M transition compared to their control iPSC while Nap1l1-knockdown-iPSC dramatically displayed the reduced proliferation and accumulated G2/M phase cells. Further analysis showed that Nap1l1 overexpression in iPSC increased the expression of cyclin B1, downregulated the expression of p21 and p27, while knockdown of Nap1l1 showed the opposite effects. In addition, overexpression of Nap1l1 promoted the phosphorylation of AKT and ERK in iPSC, while knockdown of Nap1l1 inhibited the effects. However, these effects displayed in Nap1l1-overexpression-iPSC were greatly suppressed by the inhibition of AKT or ERK signaling. CONCLUSIONS: The results indicate that Nap1l1 promotes the proliferation of iPSC attributable to G2/M transition caused by downregulation of p27 and p21, and upregulation of cyclin B1, the activation of AKT or ERK is involved in the process. The present study has revealed a novel molecular mechanism involved in the proliferation of iPSC.