A hiPSC-derived lineage-specific vascular smooth muscle cell-on-a-chip identifies aortic heterogeneity across segments.

Aortic aneurysm (AA), a potentially lethal condition with the characteristic of aortic dilatation, can only be treated by surgical or endovascular procedures. The underlying mechanisms of AA are unclear and early preventive treatment is still insufficient due to segmental aortic heterogeneity and the limitations of current disease models. Here, we firstly established a comprehensive lineage-specific vascular smooth muscle cell (SMC)-on-a-chip model using human induced pluripotent stem cells to yield cell lineages representing different segments of the aorta and tested the constructed organ-on-a-chip model under various tensile stress conditions. Bulk RNA sequencing, RT-qPCR, immunofluorescence, western blot and FACS analyses were performed to discover the segmental aortic heterogeneity of response for tensile stress and drug testing. The appropriate stretching frequency for all lineages of SMCs was 1.0 Hz, paraxial mesoderm (PM) SMCs were more sensitive to tensile stress than lateral mesoderm (LM) SMCs and neural crest (NC) SMCs. These differences may be related to the different transcriptional profiles of the tension-stressed distinct lineage-specific vascular SMCs, specifically in relation to the PI3K-Akt signaling pathway. Also, the organ-on-a-chip displayed contractile physiology, perfect fluid coordination, and was conducive to drug testing, displaying heterogeneous segmental aortic responses. Compared with LM-SMCs and NC-SMCs, PM-SMCs were more sensitive to ciprofloxacin. The model is evaluated as a novel and suitable supplement to AA animal models for determining differential physiology and drug response in different parts of the aorta. Furthermore, this system could pave the way for disease modeling, drug testing, and the personalized treatment of patients with AA in the future.

Nicotinamide Mononucleotide Alleviates Angiotensin II-Induced Human Aortic Smooth Muscle Cell Senescence in a Microphysiological Model.

ABSTRACT: The occurrence and development of aortic aneurysms are accompanied by senescence of human aortic smooth muscle cells (HASMCs). Because the mechanism of HASMC senescence has not been fully elucidated, the efficacy of various antisenescence treatments varies. Decreased nicotinamide adenine dinucleotide (NAD + ) levels are one of the mechanisms of cell senescence, and there is a lack of evidence on whether increasing NAD + levels could alleviate HASMC senescence and further retard the progression of aortic aneurysms.We constructed an HASMC-based organ-on-a-chip microphysiological model. RNA sequencing was performed on cell samples from the vehicle control and angiotensin II groups to explore biological differences. We detected cellular senescence markers and NAD + levels in HASMC-based organ-on-a-chip. Subsequently, we pretreated HASMC using the synthetic precursor of NAD + , nicotinamide mononucleotide, and angiotensin II treatment, and used rhythmic stretching to investigate whether nicotinamide mononucleotide could delay HASMC senescence.The HASMC-based organ-on-a-chip model can simulate the biomechanical microenvironment of HASMCs in vivo, and the use of angiotensin II in the model replicated senescence in HASMCs. The senescence of HASMCs was accompanied by downregulation of the expression level of nicotinamide phosphoribosyltransferase and NAD + . Pretreatment with nicotinamide mononucleotide significantly increased the NAD + level and alleviated the senescence of HASMCs, but did not change the expression level of nicotinamide phosphoribosyltransferase.Our study provides a complementary research platform between traditional cell culture and animal experiments to explore HASMC senescence in aortic aneurysms. Furthermore, it provides evidence for NAD + boosting therapy in the clinical treatment of aortic aneurysms.

PM2.5 exposure exacerbates mice thoracic aortic aneurysm and dissection by inducing smooth muscle cell apoptosis via the MAPK pathway.

Air pollution is a major public health concern worldwide. Exposure to fine particulate matter (PM2.5) is closely associated with cardiovascular diseases. However, the effect of PM2.5 exposure on thoracic aortic aneurysm and dissection (TAAD) has not been fully elucidated. Diesel exhaust particulate (DEP) is an important component of PM2.5, which causes health effects and is closely related to the incidence of cardiovascular disease. In the current study, we found that DEP exposure increased the incidence of aortic dissection (AD) in ß-aminopropionitrile (BAPN)-induced thoracic aortic aneurysm (TAA). In addition, exposure to PM2.5 increased the diameter of the thoracic aorta in mice models. The number of apoptotic cells increased in the aortic wall of PM2.5-treated mice, as did the protein expression level of BAX/Bcl2 and cleaved caspase3/caspase3. Using a rhythmically stretching aortic mechanical simulation model, fluorescent staining indicated that PM2.5 administration could induce mitochondrial dysfunction and increase reactive oxygen species (ROS) levels in human aortic smooth muscle cells (HASMCs). Furthermore, ERK1/2 mitogen-activated protein kinase (MAPK) signaling pathways participated in the apoptosis of HASMCs after PM2.5 exposure. Therefore, we concluded that PM2.5 exposure could exacerbate the progression of TAAD, which could be induced by the increased apoptosis in HASMCs through the ERK1/2 MAPK signaling pathway.

Ciprofloxacin exacerbates dysfunction of smooth muscle cells in a microphysiological model of thoracic aortic aneurysm.

Ciprofloxacin use may be associated with adverse aortic events. However, the mechanism underlying the effect of ciprofloxacin on the progression of thoracic aortic aneurysm (TAA) is not well understood. Using an in vitro microphysiological model, we treated human aortic smooth muscle cells (HASMCs) derived from patients with bicuspid aortic valve- or tricuspid aortic valve-associated (BAV- or TAV-associated) TAAs with ciprofloxacin. TAA C57BL/6 mouse models were utilized to verify the effects of ciprofloxacin exposure. In the microphysiological model, real-time PCR, Western blotting, and RNA sequencing showed that ciprofloxacin exposure was associated with a downregulated contractile phenotype, an upregulated inflammatory reaction, and extracellular matrix (ECM) degradation in the normal HASMCs derived from the nondiseased aorta. Ciprofloxacin induced mitochondrial dysfunction in the HASMCs and further increased apoptosis by activating the ERK1/2 and P38 mitogen-activated protein kinase pathways. These adverse effects appeared to be more severe in the HASMCs derived from BAV- and TAV-associated TAAs than in the normal HASMCs when the ciprofloxacin concentration exceeded 100 µg/mL. In the aortic walls of the TAA-induced mice, ECM degradation and apoptosis were aggravated after ciprofloxacin exposure. Therefore, ciprofloxacin should be used with caution in patients with BAV- or TAV-associated TAAs.

Construction of a high-throughput aorta smooth muscle-on-a-chip for thoracic aortic aneurysm drug screening.

Thoracic aortic aneurysm (TAA), in which arteries enlarge asymptomatically over time until dissection or rupture occurs, is a serious health risk. The mainstay of TAA treatment remains surgical repair due to the lack of effective drugs. The complex etiology and pathogenesis of TAA, including hemodynamic alterations and genetic factors, lead to inaccuracies in preclinical models for drug screening. Previously, our group designed an aorta smooth muscle-on-a-chip to emulate human aorta physiology and pathophysiology and screened three promising therapeutic drugs targeting mitochondrial dynamics in TAA. On this foundation, we updated the one-channel chip to an eighteen-well chip platform with four polydimethylsiloxane layers. Benefiting from this high-throughput chip, we rapidly screened multiple drugs simultaneously using distinct cell lines in vitro. In addition, we observed the abnormal activation of hypoxia-inducible factor 1-alpha (HIF-1alpha) in aortas from TAA patients by Western blot and bioinformatics analyses. Intriguingly, this phenomenon was replicated only when smooth muscle cells (SMCs) were strained on the chip. We then screened seven specific HIF-1alpha inhibitors and selected the two most effective drugs (2-methoxyestradiol and digoxin) by quantitative PCR and colorimetric methods. The results demonstrated that these two drugs can improve respiratory chain function and rescue the SMC contractile phenotype, showing applicability for the clinical treatment of TAA. This high-throughput aorta smooth muscle-on-a-chip will become a potential preclinical model for TAA drug screening.

Construction of a Human Aorta Smooth Muscle Cell Organ-On-A-Chip Model for Recapitulating Biomechanical Strain in the Aortic Wall.

Conventional two-dimensional cell culture techniques and animal models have been used in the study of human thoracic aortic aneurysm and dissection (TAAD). However, human TAAD sometimes cannot be characterized by animal models. There is an apparent species gap between clinical human studies and animal experiments that may hinder the discovery of therapeutic drugs. In contrast, the conventional cell culture model is unable to simulate in vivo biomechanical stimuli. To this end, microfabrication and microfluidic techniques have developed greatly in recent years, providing novel techniques for establishing organoids-on-a-chip models that replicate the biomechanical microenvironment. In this study, a human aorta smooth muscle cell organ-on-a-chip (HASMC-OOC) model was developed to simulate the pathophysiological parameters of aortic biomechanics, including the amplitude and frequency of cyclic strain experienced by human aortic smooth muscle cells (HASMCs) that play a vital role in TAAD. In this model, the morphology of HASMCs became elongated in shape, aligned perpendicularly to the strain direction, and presented a more contractile phenotype under strain conditions than under static conventional conditions. This was consistent with the cell orientation and phenotype in native human aortic walls. Additionally, using bicuspid aortic valve-related TAAD (BAV-TAAD) and tricuspid aortic valve-related TAAD (TAV-TAAD) patient-derived primary HASMCs, we established BAV-TAAD and TAV-TAAD disease models, which replicate HASMC characteristics in TAAD. The HASMC-OOC model provides a novel in vitro platform that is complementary to animal models for further exploring the pathogenesis of TAAD and discovering therapeutic targets.

Mechanical characterization and material modeling of ascending aortic aneurysm with different bicuspid aortic cusp fusion morphologies.

Bicuspid aortic valve (BAV) is frequently associated with ascending thoracic aortic aneurysm (ATAA). Impact of cusp fusion patterns on biomechanics and microstructure of the ATAA remains unknown. This study aims to investigate biaxial mechanical properties of the ATAAs with right-left (RL) and right-noncoronary (RN) cusp fusion patterns. Fresh ATAA samples (n = 26) were obtained from patients who underwent surgical aneurysm repair. Biaxial extension tests were performed to characterize mechanical behaviors of the RL and RN BAV-ATAAs. A material model was fitted to biaxial experimental data to obtain model parameters. Histological and mass fraction analyses were employed to investigate the underlying microstructure and dry weight percentages of elastin and collagen in the ATAA tissue. The RL and RN BAV-ATAAs exhibited nonlinear and anisotropic mechanical responses to biaxial loading. Tissue stiffness of the RN BAV-ATAAs was significantly higher than that of the RL BAV-ATAAs in the circumferential (2679 ± 755 vs 1942 ± 578 kPa, mean ± SD, p = 0.04) and longitudinal (2535 ± 630 vs 1709 ± 512 kPa, mean ± SD, p = 0.02) directions under the equibiaxial stresses. Laminar structure of elastic fibers was disrupted in both RL and RN BAV-ATAAs. Notably, interstitial fibrosis and thinner elastic fibers were identified in the RN BAV-ATAAs. Mass fraction of collagen was significantly higher for the RN BAV-ATAAs than that of the RL BAV-ATAAs. The tissue stiffness in the circumferential direction was significantly increased and strongly correlated with the mass fractions of collagen for both RL and RN BAV-ATAAs. Our results suggest that elastic properties of the RN BAV-ATAAs are more deteriorated than those of the RL BAV-ATAAs. Changes in biomechanical properties may have great impact on ascending aortic dilation.

Patient-derived microphysiological model identifies the therapeutic potential of metformin for thoracic aortic aneurysm.

BACKGROUND: Thoracic aortic aneurysm (TAA) is the permanent dilation of the thoracic aortic wall that predisposes patients to lethal events such as aortic dissection or rupture, for which effective medical therapy remains scarce. Human-relevant microphysiological models serve as a promising tool in drug screening and discovery. METHODS: We developed a dynamic, rhythmically stretching, three-dimensional microphysiological model. Using patient-derived human aortic smooth muscle cells (HAoSMCs), we tested the biological features of the model and compared them with native aortic tissues. Drug testing was performed on the individualized TAA models, and the potentially effective drug was further tested using ß-aminopropionitrile-treated mice and retrospective clinical data. FINDINGS: The HAoSMCs on the model recapitulated the expressions of many TAA-related genes in tissue. Phenotypic switching and mitochondrial dysfunction, two disease hallmarks of TAA, were highlighted on the microphysiological model: the TAA-derived HAoSMCs exhibited lower alpha-smooth muscle actin expression, lower mitochondrial membrane potential, lower oxygen consumption rate and higher superoxide accumulation than control cells, while these differences were not evidently reflected in two-dimensional culture flasks. Model-based drug testing demonstrated that metformin partially recovered contractile phenotype and mitochondrial function in TAA patients' cells. Mouse experiment and clinical investigations also demonstrated better preserved aortic microstructure, higher nicotinamide adenine dinucleotide level and lower aortic diameter with metformin treatment. INTERPRETATION: These findings support the application of this human-relevant microphysiological model in studying personalized disease characteristics and facilitating drug discovery for TAA. Metformin may regulate contractile phenotypes and metabolic dysfunctions in diseased HAoSMCs and limit aortic dilation. FUNDING: This work was supported by grants from National Key R&D Program of China (2018YFC1005002), National Natural Science Foundation of China (82070482, 81771971, 81772007, 51927805, and 21734003), the Science and Technology Commission of Shanghai Municipality (20ZR1411700, 18ZR1407000, 17JC1400200, and 20YF1406900), Shanghai Municipal Science and Technology Major Project (2017SHZDZX01), and Shanghai Municipal Education Commission (Innovation Program 2017-01-07-00-07-E00027). Y.S.Z. was not supported by any of these funds; instead, the Brigham Research Institute is acknowledged.

Gender differences in the dissection properties of ascending thoracic aortic aneurysms.

OBJECTIVES: Presentation, management and outcomes in the aortic dissection (AD) of ascending thoracic aortic aneurysm (ATAA) differ in gender and age. The purpose of this study is to investigate the dissection properties of male and female ATAAs. METHODS: Peeling tests were performed to quantitatively determine the delamination strength and dissection energy of 41 fresh ATAA samples (22 males and 19 females) in relatively young (≤65 years) and elderly (>65 years) patients. The delamination strength of the ATAAs was further correlated with patient ages for males and females. The histological investigation was employed to characterize the dissected morphology. RESULTS: For elderly patients, circumferential and longitudinal delamination strengths of the female ATAAs were statistically significantly lower than those of the males (circumferential: 31 ± 6 vs 42 ± 6 mN/mm, P < 0.01; longitudinal: 35 ± 7 vs 49 ± 10 mN/mm, P = 0.02). No significant differences were found in the delamination strength between males and females for relatively young patients. The circumferential and longitudinal delamination strengths were significantly decreased and strongly correlated with patient ages for females. However, these correlations were not present in males. Dissection routes propagated in the aortic media to create ruptured surfaces for all specimens. Peeling tests of the male ATAAs generate rougher surfaces than females. CONCLUSIONS: There is a higher propensity of AD occurrence for the elderly females as compared to males with matched ages. Surgeons should be cognizant of the risk of AD onset later in life, especially in females.

A pre-screening strategy to assess resected tumor margins by imaging cytoplasmic viscosity and hypoxia.

To assure complete tumor removal, frozen section analysis is the most common procedure for intraoperative pathological assessment of resected tumor margins. However, during one operation, multiple biopsies may be sent for examination, but only few of them are made into cryosections because of the complex preparation protocols and time-consuming pathological analysis, which potentially increases the risk of overlooking tumor involvement. Here, we propose a fluorescence-based pre-screening strategy that allows high-throughput, convenient, and fast gross assessment of resected tumor margins. A dual-activatable cationic fluorescent molecular rotor was developed to specifically illuminate live tumor cells' cytoplasm by emitting two different fluorescence signals in response to elevations in hypoxia-induced nitroreductase (a biochemical marker) and cytoplasmic viscosity (a biophysical marker), two characteristics of cancer cells. The ability of the fluorescent molecular rotor in detecting tumor cells was evaluated in mouse and human specimens of multiple tissues by comparing with hematoxylin and eosin staining. Importantly, the fluorescent molecular rotor achieved 100 % specificity in discriminating lung and liver cancers from normal tissue, allowing pre-screening of the tumor-free surgical margins and promoting clinical decision. Altogether, this type of fluorescent molecular rotor and the proposed strategy may serve as a new option to facilitate intraoperative assessment of resected tumor margins.

Aorta smooth muscle-on-a-chip reveals impaired mitochondrial dynamics as a therapeutic target for aortic aneurysm in bicuspid aortic valve disease.

Background: Bicuspid aortic valve (BAV) is the most common congenital cardiovascular disease in general population and is frequently associated with the development of thoracic aortic aneurysm (TAA). There is no effective strategy to intervene with TAA progression due to an incomplete understanding of the pathogenesis. Insufficiency of NOTCH1 expression is highly related to BAV-TAA, but the underlying mechanism remains to be clarified. Methods: A comparative proteomics analysis was used to explore the biological differences between non-diseased and BAV-TAA aortic tissues. A microfluidics-based aorta smooth muscle-on-a-chip model was constructed to evaluate the effect of NOTCH1 deficiency on contractile phenotype and mitochondrial dynamics of human aortic smooth muscle cells (HAoSMCs). Results: Protein analyses of human aortic tissues showed the insufficient expression of NOTCH1 and impaired mitochondrial dynamics in BAV-TAA. HAoSMCs with NOTCH1-knockdown exhibited reduced contractile phenotype and were accompanied by attenuated mitochondrial fusion. Furthermore, we identified that mitochondrial fusion activators (leflunomide and teriflunomide) or mitochondrial fission inhibitor (Mdivi-1) partially rescued the disorders of mitochondrial dynamics in HAoSMCs derived from BAV-TAA patients. Conclusions: The aorta smooth muscle-on-a-chip model simulates the human pathophysiological parameters of aorta biomechanics and provides a platform for molecular mechanism studies of aortic disease and related drug screening. This aorta smooth muscle-on-a-chip model and human tissue proteomic analysis revealed that impaired mitochondrial dynamics could be a potential therapeutic target for BAV-TAA. Funding: National Key R and D Program of China, National Natural Science Foundation of China, Shanghai Municipal Science and Technology Major Project, Shanghai Science and Technology Commission, and Shanghai Municipal Education Commission.

To function properly, the heart must remain a one-way system, pumping out oxygenated blood into the aorta ­ the largest artery in the body ­ so it can be distributed across the organism. The aortic valve, which sits at the entrance of the aorta, is a key component of this system. Its three flaps (or 'cusps') are pushed open when the blood exits the heart, and they shut tightly so it does not flow back in the incorrect direction. Nearly 1.4% of people around the world are born with 'bicuspid' aortic valves that only have two flaps. These valves may harden or become leaky, forcing the heart to work harder. This defect is also associated with bulges on the aorta which progressively weaken the artery, sometimes causing it to rupture. Open-heart surgery is currently the only way to treat these bulges (or 'aneurysms'), as no drug exists that could slow down disease progression. This is partly because the biological processes involved in the aneurysms worsening and bursting open is unclear. Recent studies have highlighted that many individuals with bicuspid aortic valves also have lower levels of a protein known as NOTCH1, which plays a key signalling role for cells. Problems in the mitochondria ­ the structures that power up a cell ­ are also observed. However, it is not known how these findings are connected or linked with the aneurysms developing. To answer this question, Abudupataer et al. analyzed the proteins present in diseased and healthy aortic muscle cells, confirming a lower production of NOTCH1 and impaired mitochondria in diseased tissues. They also created an 'aorta-on-a-chip' model where aortic muscle cells were grown in the laboratory under conditions resembling those found in the body ­ including the rhythmic strain that the aorta is under because of the heart beating. Abudupataer et al. then reduced NOTCH1 levels in healthy samples, which made the muscle tissue less able to contract and reduced the activity of the mitochondria. Applying drugs that tweak mitochondrial activity helped tissues from patients with bicuspid aortic valves to work better. These compounds could potentially benefit individuals with deficient aortic valves, but experiments in animals and clinical trials would be needed first to confirm the results and assess safety. The aorta-on-a-chip model developed by Abudupataer et al. also provides a platform to screen for drugs and examine the molecular mechanisms at play in aortic diseases.

Engineering a Human Pluripotent Stem Cell-Based in vitro Microphysiological System for Studying the Metformin Response in Aortic Smooth Muscle Cells.

Aortic aneurysm is a common cardiovascular disease characterised by continuous dilation of the aorta, and this disease places a heavy burden on healthcare worldwide. Few drugs have been suggested to be effective in controlling the progression of aortic aneurysms. Preclinical drug responses from traditional cell culture and animals are usually controversial. An effective in vitro model is of great demand for successful drug screening. In this study, we induced an in vitro microphysiological system to test metformin, which is a potential drug for the treatment of aortic aneurysms. Human pluripotent stem cell-derived aortic smooth muscle cells (hPSC-HASMCs) were cultured on an in vitro microphysiological system, which could replicate the cyclic stretch of the human native aortic wall. By using this system, we found that HASMCs were more likely to present a physiologically contractile phenotype compared to static cell cultures. Moreover, we used hPSC-HASMCs in our microphysiological system to perform metformin drug screening. The results showed that hPSC-HASMCs presented a more contractile phenotype via NOTCH 1 signalling while being treated with metformin. This result indicated that metformin could be utilised to rescue hPSC-HASMCs from phenotype switching during aortic aneurysm progression. This study helps to elucidate potential drug targets for the treatment of aortic aneurysms.

99m Tc-labeled Duramycin for detecting and monitoring cardiomyocyte death and assessing atorvastatin cardioprotection in acute myocardial infarction.

This study aimed to dynamically monitor myocardial cell death using 99m Tc-Duramycin single-photon emission computed tomography/computed tomography (micro-SPECT/CT) imaging in acute myocardial infarction (AMI) and the anti-apoptosis effect of atorvastatin for cardioprotection. Mice were randomized into three groups: AMI group, AMI with atorvastatin treatment (T-AMI) group, and sham group. Three groups of model mice were randomly selected at day 1 (D1), day 3 (D3), and day 7 (D7) day after surgery with 99m Tc-Duramycin micro-SPECT/CT imaging. The lesion-to-normal myocardial tissue ratio (L/N) average values were 2.62 on D1, 3.89 on D3, and 1.20 on D7 for the uptake of 99m Tc-duramycin in the infarcted region in the AMI group. The sham group presented no positive imaging in myocardium, and the L/N average values were 1.09, 1.14, and 1.10 on D1, D3, and D7, respectively. Meanwhile, 99m Tc-linear-duramycin imaging showed no radioactive uptake in the infarction region. The T-AMI group imaging showed tracer uptake decreased obviously compared to the uptake in the infarcted region in AMI mice. 99m Tc-Duramycin SPECT/CT imaging allowed non-invasive monitoring of myocardial cell death in a mouse model of AMI and an assessment of atorvastatin anti-apoptosis effect for cardioprotection by in vivo molecular imaging.

Using Multilayered Hydrogel Bioink in Three-Dimensional Bioprinting for Homogeneous Cell Distribution.

During the extrusion-based three-dimensional bioprinting process, liquid-like bioinks with low viscosity can protect cells from membrane damage induced by shear stress and improve the survival of the encapsulated cells. However, rapid gravity-driven cell sedimentation in the reservoir could lead to an inhomogeneous cell distribution in bioprinted structures and therefore hinder the application of liquid-like bioinks. Here, we developed a novel multilayered modified strategy for liquid-like bioinks (e.g., gelatin methacryloyl with low viscosity) to prevent the sedimentation of encapsulated cells. Multiple liquid interfaces were manipulated in the multilayered bioink to provide interfacial retention. Consequently, the cell sedimentation action going across adjacent layers in the multilayered system was retarded in the bioink reservoir. It was found that the interfacial retention was much higher than the sedimental pull of cells, demonstrating a critical role of the interfacial retention in preventing cell sedimentation and promoting a more homogeneous dispersion of cells in the multilayered bioink.

Histamine deficiency facilitates coronary microthrombosis after myocardial infarction by increasing neutrophil-platelet interactions.

Neutrophil-platelet interactions are responsible for thrombosis as well as inflammatory responses following acute myocardial infarction (AMI). While histamine has been shown to play a crucial role in many physiological and pathological processes, its effects on neutrophil-platelet interactions in thromboinflammatory complications of AMI remain elusive. In this study, we show a previously unknown mechanism by which neutrophil-derived histamine protects the infarcted heart from excessive neutrophil-platelet interactions and redundant arterial thrombosis. Using histamine-deficient (histidine decarboxylase knockout, HDC-/- ) and wild-type murine AMI models, we demonstrate that histamine deficiency increases the number of microthrombosis after AMI, in accordance with depressed cardiac function. Histamine-producing myeloid cells, mainly Ly6G+ neutrophils, directly participate in arteriole thrombosis. Histamine deficiency elevates platelet activation and aggregation by enhancing Akt phosphorylation and leads to dysfunctional characteristics in neutrophils which was confirmed by high levels of reactive oxygen species production and CD11b expression. Furthermore, HDC-/- platelets were shown to elicit neutrophil extracellular nucleosomes release, provoke neutrophil-platelet interactions and promote HDC-expressing neutrophils recruitment in arteriole thrombosis in vivo. In conclusion, we provide evidence that histamine deficiency promotes coronary microthrombosis and deteriorates cardiac function post-AMI, which is associated with the enhanced platelets/neutrophils function and neutrophil-platelet interactions.

Bioprinting a 3D vascular construct for engineering a vessel-on-a-chip.

The organ-on-a-chip model mimics the structural and functional features of human tissues or organs and has great importance in translational research. For vessel-on-a-chip model, conventional fabrication techniques are unable to efficiently imitate the intimal-medial unit of the vessel wall. Bioprinting technology, which can precisely control the organization of cells, biomolecules, and the extracellular matrix, has the potential to fabricate three-dimensional (3D) tissue constructs with spatial heterogeneity. In this study, we applied the gelatin-methacryloyl-based bioprinting technology to print 3D construct containing endothelial cells (ECs) and smooth muscle cells (SMCs) on a microfluidic chip. Compared with traditional culture system, EC-SMC coculturing chip model upregulated αSMA and SM22 protein expression of the SMC to a greater degree and maintains the contractile phenotype of the SMC, which mimics the natural vascular microenvironment. This strategy enabled us to establish an in vitro vascular model for studies of the physiologic and pathologic process in vascular wall.

Histamine deficiency delays ischaemic skeletal muscle regeneration via inducing aberrant inflammatory responses and repressing myoblast proliferation.

Histidine decarboxylase (HDC) catalyses the formation of histamine from L-histidine. Histamine is a biogenic amine involved in many physiological and pathological processes, but its role in the regeneration of skeletal muscles has not been thoroughly clarified. Here, using a murine model of hindlimb ischaemia, we show that histamine deficiency in Hdc knockout (Hdc-/- ) mice significantly reduces blood perfusion and impairs muscle regeneration. Using Hdc-EGFP transgenic mice, we demonstrate that HDC is expressed predominately in CD11b+ Gr-1+ myeloid cells but not in skeletal muscles and endothelial cells. Large amounts of HDC-expressing CD11b+ myeloid cells are rapidly recruited to injured and inflamed muscles. Hdc-/- enhances inflammatory responses and inhibits macrophage differentiation. Mechanically, we demonstrate that histamine deficiency decreases IGF-1 (insulin-like growth factor 1) levels and diminishes myoblast proliferation via H3R/PI3K/AKT-dependent signalling. These results indicate a novel role for HDC-expressing CD11b+ myeloid cells and histamine in myoblast proliferation and skeletal muscle regeneration.

Hydrogel Bioink with Multilayered Interfaces Improves Dispersibility of Encapsulated Cells in Extrusion Bioprinting.

One of the challenges for extrusion bioprinting using low-viscosity bioinks is the fast gravity-driven sedimentation of cells. Cells in a hydrogel bioink that features low viscosity tend to settle to the bottom of the bioink reservoir, and as such, their bioprintability is hindered by association with the inhomogeneous cellularized structures that are deposited. This is particularly true in cases where longer periods are required to print complex or larger tissue constructs. Increasing the bioink's viscosity efficiently retards sedimentation but gives rise to cell membranolysis or functional disruption due to increased shear stress on the cells during the extrusion process. Inspired by the rainbow cocktail, we report the development of a multilayered modification strategy for gelatin methacryloyl (GelMA) bioink to manipulate multiple liquid interfaces, providing interfacial retention to retard cell sedimentation in the bioink reservoir. Indeed, the interfacial tension in our layer-by-layer bioink system, characterized by the pendant drop method, was found to be exponentially higher than the sedimental pull (ΔGravity-Buoyancy = ∼10-9 N) of cells, indicating that the interfacial retention is crucial for preventing cell sedimentation across the adjacent layers. It was demonstrated that the encapsulated cells displayed better dispersibility in constructs bioprinted using the multilayered GelMA bioink system than that of pristine GelMA where the index of homogeneity of the cell distribution in the multilayered bioink was 4 times that of the latter.

Correction to: SPECT/CT imaging of apoptosis in aortic aneurysm with radiolabeled duramycin.

The original version of this article unfortunately contains errors in Figure 4. An incorrect Figure 4D is published which is actually a repetition of Figure 2C (i.e., apoptosis rate in control vs. H2O2-treated group). The correct Figure 4D should be the aortic diameter of control vs. experimental groups. Also, the order of part figures (a\b\c\d) in Figure 4E is incorrect. The correct Figure 4 is given below.

Excessive Neutrophil Extracellular Trap Formation Aggravates Acute Myocardial Infarction Injury in Apolipoprotein E Deficiency Mice via the ROS-Dependent Pathway.

Genetically human apolipoprotein E (APOE) ε32 is associated with a decreased risk of ischemic heart disease. ApoE deficiency in mice impairs infarct healing after myocardial infarction (MI). After the ischemic injury, a large number of neutrophils are firstly recruited into the infarct zone and then degrade dead material and promote reparative phase transformation. The role of ApoE in inflammation response in the early stage of MI remains largely unclear. In this study, we investigated the effect of ApoE deficiency on neutrophils' function and myocardial injury after myocardial infarction. By left coronary artery ligation in ApoE -/- and wild-type (WT) mice, we observed increased infarct size and neutrophil infiltration in ApoE -/- mice. Within the infarct zone, more neutrophil extracellular traps (NETs) were observed in ApoE -/- mice, while increased ex vivo NET formation was detected in ApoE -/- mouse-derived neutrophils through the NADPH oxidase-ROS-dependent pathway. Suppressing overproduced NETs reduced myocardial injury in ApoE -/- mice after ligation. In general, our findings reveal a critical role of apolipoprotein E in regulating Ly6G+ neutrophil activation and NET formation, resulting in limiting myocardial injury after myocardial infarction. In such a process, apolipoprotein E regulates NET formation via the ROS-MAPK-MSK1 pathway.