Human microphysiological models of airway and alveolar epithelia.

Human organ-on-a-chip models are powerful tools for preclinical research that can be used to study the mechanisms of disease and evaluate new targets for therapeutic intervention. Lung-on-a-chip models have been one of the most well-characterized designs in this field and can be altered to evaluate various types of respiratory disease and to assess treatment candidates prior to clinical testing. These systems are capable of overcoming the flaws of conventional two-dimensional (2-D) cell culture and in vivo animal testing due to their ability to accurately recapitulate the in vivo microenvironment of human tissue with tunable material properties, microfluidic integration, delivery of precise mechanical and biochemical cues, and designs with organ-specific architecture. In this review, we first describe an overview of currently available lung-on-a-chip designs. We then present how recent innovations in human stem cell biology, tissue engineering, and microfabrication can be used to create more predictive human lung-on-a-chip models for studying respiratory disease. Finally, we discuss the current challenges and future directions of lung-on-a-chip designs for in vitro disease modeling with a particular focus on immune and multiorgan interactions.

Landscape of glycolytic metabolites and their regulating proteins in myocardium from human heart failure with preserved ejection fraction.

AIMS: Heart failure (HF) with preserved ejection fraction (HFpEF) reflects half of all clinical HF yet has few therapies. Obesity and diabetes are now common comorbidities which have focused attention towards underlying myocardial metabolic defects. The profile of a major metabolic pathway, glycolytic intermediates and their regulating enzymes and ancillary pathways, remains unknown. METHODS AND RESULTS: Endomyocardial biopsies from HFpEF (n = 37) and non-failing controls (n = 21) were assayed by non-targeted or targeted metabolomics and immunoblot to determine glycolytic and ancillary pathway metabolites and protein expression of their regulating enzymes. Glucose and GLUT1 expression were higher in HFpEF, but prominent glycolytic metabolites: glucose-6-phosphate, fructose-1,6-biphosphate (F1,6bP), and 3-phosphoglycerate were reduced by -78%, -91%, and -73%, respectively, versus controls. Expression of their corresponding synthesizing enzymes hexokinase, phospho-fructokinase, and phosphoglycerate kinase were also significantly lower (all p < 0.0005). Pentose phosphate and hexosamine biosynthetic pathway metabolites were reduced while glycogen content increased. Despite proximal reduction in key glycolytic intermediates, pyruvate increased but mitochondrial pyruvate transporter (MPC1) expression was reduced. Pyruvate dehydrogenase converting pyruvate to acetyl-CoA was more activated but some Krebs cycle intermediates were reduced. This HFpEF glycolytic profile persisted after adjusting for body mass index (BMI), diabetes, age, and sex, or in subgroup analysis with controls and HFpEF matched for BMI and diabetes/insulin history. In HFpEF, BMI but not glycated haemoglobin negatively correlated with F1,6bP (p = 7e-5, r = -0.61) and phosphoenolpyruvate (p = 0.006, r = -0.46). CONCLUSIONS: Human HFpEF myocardium exhibits reduced glycolytic and ancillary pathway intermediates and expression of their synthesizing proteins. This combines features reported in HF with reduced ejection fraction and obesity/diabetes that likely exacerbate metabolic inflexibility.

ATP Citrate Lyase Supports Cardiac Function and NAD+/NADH Balance And Is Depressed in Human Heart Failure.

BACKGROUND: ATP-citrate lyase (ACLY) converts citrate into acetyl-CoA and oxaloacetate in the cytosol. It plays a prominent role in lipogenesis and fat accumulation coupled to excess glucose, and its inhibition is approved for treating hyperlipidemia. In RNAseq analysis of human failing myocardium, we found ACLY gene expression is reduced; however the impact this might have on cardiac function and/or metabolism has not been previously studied. As new ACLY inhibitors are in development for cancer and other disorders, such understanding has added importance. METHODS: Cardiomyocytes, ex-vivo beating hearts, and in vivo hearts with ACLY inhibited by selective pharmacologic (BMS303141, ACLYi) or genetic suppression, were studied. Regulation of ACLY gene/protein expression, and effects of ACLYi on function, cytotoxicity, tricarboxylic acid (TCA)-cycle metabolism, and redox and NAD+/NADH balance were assessed. Mice with cardiac ACLY knockdown induced by AAV9-acly-shRNA or cardiomyocyte tamoxifen-inducible Acly knockdown were studied. RESULTS: Acly gene expression was reduced more in obese patients with heart failure and preserved EF (HFpEF) than HF with reduced EF. In vivo pressure-overload and in vitro hormonal stress increased ACLY protein expression, whereas it declined upon fatty-acid exposure. Acute ACLYi (1-hr) dose-dependently induced cytotoxicity in adult and neonatal cardiomyocytes, and caused substantial reduction of systolic and diastolic function in myocytes and ex-vivo beating hearts. In the latter, ATP/ADP ratio also fell and lactate increased. U13C-glucose tracing revealed an ACLYdependent TCA-bypass circuit in myocytes, where citrate generated in mitochondria is transported to the cytosol, metabolized by ACLY and then converted to malate to re-enter mitochondria,bypassing several NADH-generating steps. ACLYi lowered NAD+/NADH ratio and restoring this balance ameliorated cardiomyocyte toxicity. Oxidative stress was undetected with ACLYi. Adult hearts following 8-weeks of reduced cardiac and/or cardiomyocyte ACLY downregulation exhibited ventricular dilation and reduced function that was prevented by NAD augmentation. Cardiac dysfunction from ACLY knockdown was worse in hearts subjected to sustained pressureoverload, supporting a role in stress responses. CONCLUSIONS: ACLY supports normal cardiac function through maintenance of the NAD+/NADH balance and is upregulated by hemodynamic and hormonal stress, but depressed by lipid excess. ACLY levels are most reduced in human HFpEF with obesity potentially worsening cardio-metabolic reserve.

Myocardial ultrastructure of human heart failure with preserved ejection fraction.

Over half of patients with heart failure have a preserved ejection fraction (>50%, called HFpEF), a syndrome with substantial morbidity/mortality and few effective therapies1. Its dominant comorbidity is now obesity, which worsens disease and prognosis1-3. Myocardial data from patients with morbid obesity and HFpEF show depressed myocyte calcium-stimulated tension4 and disrupted gene expression of mitochondrial and lipid metabolic pathways5,6, abnormalities shared by human HF with a reduced EF but less so in HFpEF without severe obesity. The impact of severe obesity on human HFpEF myocardial ultrastructure remains unexplored. Here we assessed the myocardial ultrastructure in septal biopsies from patients with HFpEF using transmission electron microscopy. We observed sarcomere disruption and sarcolysis, mitochondrial swelling with cristae separation and dissolution and lipid droplet accumulation that was more prominent in the most obese patients with HFpEF and not dependent on comorbid diabetes. Myocardial proteomics revealed associated reduction in fatty acid uptake, processing and oxidation and mitochondrial respiration proteins, particularly in very obese patients with HFpEF.

Depressed Proximal Glycolysis in Myocardium Of Human Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) accounts for >50% of all heart failure world-wide and remains a major unmet medical need. The most effective recently approved treatments were first developed for diabetes, suggesting metabolic defects are paramount. Myocardial metabolomics in human HFpEF has identified reduced fatty acid and branched chain amino acid catabolism, but the status of glycolysis is unknown. Here we performed targeted metabolomics and protein analysis of glycolytic pathway enzymes in myocardial biopsies of patients with HFpEF versus HF with reduced ejection fraction (HFrEF0 or non-failing controls. Glucose was increased in HFpEF myocardium, but immediate downstream glycolytic metabolites (glucose-6 phosphate, fructose 1,6 diphosphate), were more reduced in HFpEF than the other groups, as were their associated synthetic enzymes hexokinase and phosphofructokinase. Pyruvate was also reduced in HFpEF versus controls. These changes were either not present or substantially less so in HFrEF. Suppression of proximal glycolysis was also coupled to lower metabolites and proteins in the pentose phosphate pathway but was independent of diabetes or obesity. These findings support marked metabolic inflexibility in HFpEF and identifies very proximal blockade in glucose metabolism. Efforts to improve metabolic use of carbohydrates in HFpEF will likely need to target these proximal glycolytic enzymes.

Multiomics analysis reveals the biological effects of live Roseburia intestinalis as a high-butyrate-producing bacterium in human intestinal epithelial cells.

Butyrate-producing bacteria play a key role in human health, and recent studies have triggered interest in their development as next-generation probiotics. However, there remains limited knowledge not only on the identification of high-butyrate-producing bacteria in the human gut but also in the metabolic capacities for prebiotic carbohydrates and their interaction with the host. Herein, it was discovered that Roseburia intestinalis produces higher levels of butyrate and digests a wider variety of prebiotic polysaccharide structures compared with other human major butyrate-producing bacteria (Eubacterium rectale, Faecalibacterium prausnitzii, and Roseburia hominis). Moreover, R. intestinalis extracts upregulated the mRNA expression of tight junction proteins (TJP1, OCLN, and CLDN3) in human intestinal epithelial cells more than other butyrate-producing bacteria. R. intestinalis was cultured with human intestinal epithelial cells in the mimetic intestinal host-microbe interaction coculture system to explore the health-promoting effects using multiomics approaches. Consequently, it was discovered that live R. intestinalis only enhances purine metabolism and the oxidative pathway, increasing adenosine triphosphate levels in human intestinal epithelial cells, but that heat-killed bacteria had no effect. Therefore, this study proposes that R. intestinalis has potentially high value as a next-generation probiotic to promote host intestinal health.

Unveiling the inhibition mechanism of Clostridioides difficile by Bifidobacterium longum via multiomics approach.

Antibiotic-induced gut microbiota disruption constitutes a major risk factor for Clostridioides difficile infection (CDI). Further, antibiotic therapy, which is the standard treatment option for CDI, exacerbates gut microbiota imbalance, thereby causing high recurrent CDI incidence. Consequently, probiotic-based CDI treatment has emerged as a long-term management and preventive option. However, the mechanisms underlying the therapeutic effects of probiotics for CDI remain uninvestigated, thereby creating a knowledge gap that needs to be addressed. To fill this gap, we used a multiomics approach to holistically investigate the mechanisms underlying the therapeutic effects of probiotics for CDI at a molecular level. We first screened Bifidobacterium longum owing to its inhibitory effect on C. difficile growth, then observed the physiological changes associated with the inhibition of C. difficile growth and toxin production via a multiomics approach. Regarding the mechanism underlying C. difficile growth inhibition, we detected a decrease in intracellular adenosine triphosphate (ATP) synthesis due to B. longum-produced lactate and a subsequent decrease in (deoxy)ribonucleoside triphosphate synthesis. Via the differential regulation of proteins involved in translation and protein quality control, we identified B. longum-induced proteinaceous stress. Finally, we found that B. longum suppressed the toxin production of C. difficile by replenishing proline consumed by it. Overall, the findings of the present study expand our understanding of the mechanisms by which probiotics inhibit C. difficile growth and contribute to the development of live biotherapeutic products based on molecular mechanisms for treating CDI.

Investigation of metabolic crosstalk between host and pathogenic Clostridioides difficile via multiomics approaches.

Clostridioides difficile is a gram-positive anaerobic bacterium that causes antibiotic-associated infections in the gut. C. difficile infection develops in the intestine of a host with an imbalance of the intestinal microbiota and, in severe cases, can lead to toxic megacolon, intestinal perforation, and even death. Despite its severity and importance, however, the lack of a model to understand host-pathogen interactions and the lack of research results on host cell effects and response mechanisms under C. difficile infection remain limited. Here, we developed an in vitro anaerobic-aerobic C. difficile infection model that enables direct interaction between human gut epithelial cells and C. difficile through the Mimetic Intestinal Host-Microbe Interaction Coculture System. Additionally, an integrative multiomics approach was applied to investigate the biological changes and response mechanisms of host cells caused by C. difficile in the early stage of infection. The C. difficile infection model was validated through the induction of disaggregation of the actin filaments and disruption of the intestinal epithelial barrier as the toxin-mediated phenotypes following infection progression. In addition, an upregulation of stress-induced chaperones and an increase in the ubiquitin proteasomal pathway were identified in response to protein stress that occurred in the early stage of infection, and downregulation of proteins contained in the electron transfer chain and ATP synthase was observed. It has been demonstrated that host cell energy metabolism is inhibited through the glycolysis of Caco-2 cells and the reduction of metabolites belonging to the TCA cycle. Taken together, our C. difficile infection model suggests a new biological response pathway in the host cell induced by C. difficile during the early stage of infection at the molecular level under anaerobic-aerobic conditions. Therefore, this study has the potential to be applied to the development of future therapeutics through basic metabolic studies of C. difficile infection.

Pharmacological TRPC6 inhibition improves survival and muscle function in mice with Duchenne muscular dystrophy.

Gene mutations causing loss of dystrophin result in the severe muscle disease known as Duchenne muscular dystrophy (DMD). Despite efforts at genetic repair, DMD therapy remains largely palliative. Loss of dystrophin destabilizes the sarcolemmal membrane, inducing mechanosensitive cation channels to increase calcium entry and promote cell damage and, eventually, muscle dysfunction. One putative channel is transient receptor potential canonical 6 (TRPC6); we have shown that TRPC6 contributed to abnormal force and calcium stress-responses in cardiomyocytes from mice lacking dystrophin that were haplodeficient for utrophin (mdx/utrn+/- [HET] mice). Here, we show in both the HET mouse and the far more severe homozygous mdx/utrn-/- mouse that TRPC6 gene deletion or its selective pharmacologic inhibition (by BI 749327) prolonged survival 2- to 3-fold, improving skeletal and cardiac muscle and bone defects. Gene pathways reduced by BI 749327 treatment most prominently regulated fat metabolism and TGF-ß1 signaling. These results support the testing of TRPC6 inhibitors in human trials for other diseases as a novel DMD therapy.

Carbon-nanotube/silver networks in nitrile butadiene rubber for highly conductive flexible adhesives.

An adhesive with high conductivity, flexibility, cyclability, oxidation resistance, and good adhesion is developed using microscale silver flakes, multiwalled carbon nanotubes decorated with nanoscale silver particles, and nitrile butadiene rubber. Light-emitting-diode chips are attached to the conductive, flexible adhesive pattern on a poly(ethylene terephthalate) substrate as a visual demonstration. The brightness is invariant during bending tests.