Publications by authors named "Timothy A Hacker"

84 Publications

Murine cardiac fibrosis localization using adaptive Bayesian cardiac strain imaging in vivo.

Sci Rep 2022 May 20;12(1):8522. Epub 2022 May 20.

Medical Physics, University of Wisconsin (UW)-Madison, Madison, USA.

An adaptive Bayesian regularized cardiac strain imaging (ABR-CSI) algorithm for in vivo murine myocardial function assessment is presented. We report on 31 BALB/CJ mice (n = 17 females, n = 14 males), randomly stratified into three surgical groups: myocardial infarction (MI, n = 10), ischemia-reperfusion (IR, n = 13) and control (sham, n = 8) imaged pre-surgery (baseline- BL), and 1, 2, 7 and 14 days post-surgery using a high frequency ultrasound imaging system (Vevo 2100). End-systole (ES) radial and longitudinal strain images were used to generate cardiac fibrosis maps using binary thresholding. Percentage fibrotic myocardium (PFM) computed from regional fibrosis maps demonstrated statistically significant differences post-surgery in scar regions. For example, the MI group had significantly higher PFM (%) values in the anterior mid region (p = 0.006) at Day 14 (n = 8, 42.30 ± 14.57) compared to BL (n = 12, 1.32 ± 0.85). A random forest classifier automatically detected fibrotic regions from ground truth Masson's trichrome stained histopathology whole slide images. Both PFM (r = 0.70) and PFM (r = 0.60) results demonstrated strong, positive correlation with PFM (p < 0.001).
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http://dx.doi.org/10.1038/s41598-022-12579-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9122999PMC
May 2022

RBM20 phosphorylation and its role in nucleocytoplasmic transport and cardiac pathogenesis.

FASEB J 2022 05;36(5):e22302

Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Wisconsin, USA.

Arginine-serine (RS) domain(s) in splicing factors are critical for protein-protein interaction in pre-mRNA splicing. Phosphorylation of RS domain is important for splicing control and nucleocytoplasmic transport in the cell. RNA-binding motif 20 (RBM20) is a splicing factor primarily expressed in the heart. A previous study using phospho-antibody against RS domain showed that RS domain can be phosphorylated. However, its actual phosphorylation sites and function have not been characterized. Using middle-down mass spectrometry, we identified 16 phosphorylation sites, two of which (S638 and S640 in rats, or S637 and S639 in mice) were located in the RSRSP stretch in the RS domain. Mutations on S638 and S640 regulated splicing, promoted nucleocytoplasmic transport and protein-RNA condensates. Phosphomimetic mutations on S638 and S640 indicated that phosphorylation was not the major cause for RBM20 nucleocytoplasmic transport and condensation in vitro. We generated a S637A knock-in (KI) mouse model (Rbm20 ) and observed the reduced RBM20 phosphorylation. The KI mice exhibited aberrant gene splicing, protein condensates, and a dilated cardiomyopathy (DCM)-like phenotype. Transcriptomic profiling demonstrated that KI mice had altered expression and splicing of genes involving cardiac dysfunction, protein localization, and condensation. Our in vitro data showed that phosphorylation was not a direct cause for nucleocytoplasmic transport and protein condensation. Subsequently, the in vivo results reveal that RBM20 mutations led to cardiac pathogenesis. However, the role of phosphorylation in vivo needs further investigation.
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http://dx.doi.org/10.1096/fj.202101811RRDOI Listing
May 2022

Population-based high-throughput toxicity screen of human iPSC-derived cardiomyocytes and neurons.

Cell Rep 2022 04;39(1):110643

Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan; Department of Medicine and Stem Cell and Regenerative Medicine Center, University of Wisconsin-Madison, Madison, WI 53705, USA; Institute of Medical Genomics and Proteomics and Institute of Clinical Medicine, National Taiwan University, Taipei 106, Taiwan. Electronic address:

In this study, we establish a population-based human induced pluripotent stem cell (hiPSC) drug screening platform for toxicity assessment. After recruiting 1,000 healthy donors and screening for high-frequency human leukocyte antigen (HLA) haplotypes, we identify 13 HLA-homozygous "super donors" to represent the population. These "super donors" are also expected to represent at least 477,611,135 of the global population. By differentiating these representative hiPSCs into cardiomyocytes and neurons we show their utility in a high-throughput toxicity screen. To validate hit compounds, we demonstrate dose-dependent toxicity of the hit compounds and assess functional modulation. We also show reproducible in vivo drug toxicity results using mouse models with select hit compounds. This study shows the feasibility of using a population-based hiPSC drug screening platform to assess cytotoxicity, which can be used as an innovative tool to study inter-population differences in drug toxicity and adverse drug reactions in drug discovery applications.
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http://dx.doi.org/10.1016/j.celrep.2022.110643DOI Listing
April 2022

Sex differences in right ventricular adaptation to pressure overload in a rat model.

J Appl Physiol (1985) 2022 Mar 3;132(3):888-901. Epub 2022 Feb 3.

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.

With severe right ventricular (RV) pressure overload, women demonstrate better clinical outcomes compared with men. The mechanoenergetic mechanisms underlying this protective effect, and their dependence on female endogenous sex hormones, remain unknown. To investigate these mechanisms and their impact on RV systolic and diastolic functional adaptation, we created comparable pressure overload via pulmonary artery banding (PAB) in intact male and female Wistar rats and ovariectomized (OVX) female rats. At 8 wk after surgery, right heart catheterization demonstrated increased RV energy input [indexed pressure-volume area (iPVA)] in all PAB groups, with the greatest increase in intact females. PAB also increased RV energy output [indexed stroke or external work (iEW)] in all groups, again with the greatest increase in intact females. In contrast, PAB only increased RV contractility-indexed end-systolic elastance (i)] in females. Despite these sex-dependent differences, no statistically significant effects were observed in the ratio of RV energy output to input (mechanical efficiency) or in mechanoenergetic cost to pump blood with pressure overload. These metrics were similarly unaffected by loss of endogenous sex hormones in females. Also, despite sex-dependent differences in collagen content and organization with pressure overload, decreases in RV compliance and relaxation time constant (tau Weiss) were not determined to be sex dependent. Overall, despite sex-dependent differences in RV contractile and fibrotic responses, RV mechanoenergetics for this degree and duration of pressure overload are comparable between sexes and suggest a homeostatic target. Sex differences in right ventricular mechanical efficiency and energetic adaptation to increased right ventricular afterload were measured. Despite sex-dependent differences in contractile and fibrotic responses, right ventricular mechanoenergetic adaptation was comparable between the sexes, suggesting a homeostatic target.
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http://dx.doi.org/10.1152/japplphysiol.00175.2021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8934674PMC
March 2022

Bayesian Regularized Strain Imaging for Assessment of Murine Cardiac Function In vivo.

Annu Int Conf IEEE Eng Med Biol Soc 2021 11;2021:2883-2886

A cardiac strain imaging framework with adaptive Bayesian regularization (ABR) is proposed for in vivo assessment of murine cardiac function. The framework uses ultrasound (US) radio-frequency data collected with a high frequency (f = 30MHz) imaging system and a multi-level block matching algorithm with ABR to derive inter-frame cardiac displacements. Lagrangian cardiac strain (radial, e and longitudinal, e) tensors were derived by segmenting the myocardial wall starting at the ECG R-wave and accumulating interframe deformations over a cardiac cycle. In vivo feasibility was investigated through a longitudinal study with two mice (one ischemia-perfusion (IR) injury and one sham) imaged at five sessions (pre-surgery (BL) and 1,2,7 and 14 days post-surgery). End-systole (ES) strain images and segmental strain curves were derived for quantitative evaluation. Both mice showed periodic variation of e and e strain at BL with segmental synchroneity. Infarcted regions of IR mouse at Day 14 were associated with reduced or sign reversed ES e and e values while the sham mouse had similar or higher strain than at BL. Infarcted regions identified in vivo were associated with increased collagen content confirmed with Masson's Trichrome stained ex vivo heart sections.Clinical Relevance-Higher quality cardiac strain images derived with RF data and Bayesian regularization can potentially improve the sensitivity and accuracy of non-invasive assessment of cardiovascular disease models.
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http://dx.doi.org/10.1109/EMBC46164.2021.9630712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8908881PMC
November 2021

Long-term in vivo operation of implanted cardiac nanogenerators in swine.

Nano Energy 2021 Dec 11;90(Pt A). Epub 2021 Sep 11.

Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.

Implantable nanogenerators (i-NG) provide power to cardiovascular implantable electronic devices (CIEDs) by harvesting biomechanical energy locally eliminating the need for batteries. However, its long-term operation and biological influences on the heart have not been tested. Here, we evaluate a soft and flexible i-NG system engineered for long-term in vivo cardiac implantation. It consisted of i-NG, leads, and receivers, and was implanted on the epicardium of swine hearts for 2 months. The i-NG system generated electric current throughout the testing period. Biocompatibility and biosafety were established based on normal blood and serum test results and no tissue reactions. Heart function was unchanged over the testing period as validated by normal electrocardiogram (ECG), transthoracic ultrasound, and invasive cardiac functional measures. This research demonstrates the safety, long term operation and therefore the feasibility of using i-NGs to power the next generation CIEDs.
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http://dx.doi.org/10.1016/j.nanoen.2021.106507DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8562697PMC
December 2021

Malonate Promotes Adult Cardiomyocyte Proliferation and Heart Regeneration.

Circulation 2021 05 5;143(20):1973-1986. Epub 2021 Mar 5.

Department of Cell and Regenerative Biology (J.B., R.J.S., E.B.B., W.G.P., Z.Z., A.I.M.), University of Wisconsin-Madison School of Medicine and Public Health.

Background: Neonatal mouse cardiomyocytes undergo a metabolic switch from glycolysis to oxidative phosphorylation, which results in a significant increase in reactive oxygen species production that induces DNA damage. These cellular changes contribute to cardiomyocyte cell cycle exit and loss of the capacity for cardiac regeneration. The mechanisms that regulate this metabolic switch and the increase in reactive oxygen species production have been relatively unexplored. Current evidence suggests that elevated reactive oxygen species production in ischemic tissues occurs as a result of accumulation of the mitochondrial metabolite succinate during ischemia via succinate dehydrogenase (SDH), and this succinate is rapidly oxidized at reperfusion. Mutations in SDH in familial cancer syndromes have been demonstrated to promote a metabolic shift into glycolytic metabolism, suggesting a potential role for SDH in regulating cellular metabolism. Whether succinate and SDH regulate cardiomyocyte cell cycle activity and the cardiac metabolic state remains unclear.

Methods: Here, we investigated the role of succinate and SDH inhibition in regulation of postnatal cardiomyocyte cell cycle activity and heart regeneration.

Results: Our results demonstrate that injection of succinate into neonatal mice results in inhibition of cardiomyocyte proliferation and regeneration. Our evidence also shows that inhibition of SDH by malonate treatment after birth extends the window of cardiomyocyte proliferation and regeneration in juvenile mice. Remarkably, extending malonate treatment to the adult mouse heart after myocardial infarction injury results in a robust regenerative response within 4 weeks after injury via promoting adult cardiomyocyte proliferation and revascularization. Our metabolite analysis after SDH inhibition by malonate induces dynamic changes in adult cardiac metabolism.

Conclusions: Inhibition of SDH by malonate promotes adult cardiomyocyte proliferation, revascularization, and heart regeneration via metabolic reprogramming. These findings support a potentially important new therapeutic approach for human heart failure.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.120.049952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8131241PMC
May 2021

Cardiac MyBP-C phosphorylation regulates the Frank-Starling relationship in murine hearts.

J Gen Physiol 2021 07;153(7)

Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO.

The Frank-Starling relationship establishes that elevated end-diastolic volume progressively increases ventricular pressure and stroke volume in healthy hearts. The relationship is modulated by a number of physiological inputs and is often depressed in human heart failure. Emerging evidence suggests that cardiac myosin-binding protein-C (cMyBP-C) contributes to the Frank-Starling relationship. We measured contractile properties at multiple levels of structural organization to determine the role of cMyBP-C and its phosphorylation in regulating (1) the sarcomere length dependence of power in cardiac myofilaments and (2) the Frank-Starling relationship in vivo. We compared transgenic mice expressing wild-type cMyBP-C on the null background, which have ∼50% phosphorylated cMyBP-C (Controls), to transgenic mice lacking cMyBP-C (KO) and to mice expressing cMyBP-C that have serine-273, -282, and -302 mutated to aspartate (cMyBP-C t3SD) or alanine (cMyBP-C t3SA) on the null background to mimic either constitutive PKA phosphorylation or nonphosphorylated cMyBP-C, respectively. We observed a continuum of length dependence of power output in myocyte preparations. Sarcomere length dependence of power progressively increased with a rank ordering of cMyBP-C KO = cMyBP-C t3SA < Control < cMyBP-C t3SD. Length dependence of myofilament power translated, at least in part, to hearts, whereby Frank-Starling relationships were steepest in cMyBP-C t3SD mice. The results support the hypothesis that cMyBP-C and its phosphorylation state tune sarcomere length dependence of myofibrillar power, and these regulatory processes translate across spatial levels of myocardial organization to control beat-to-beat ventricular performance.
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http://dx.doi.org/10.1085/jgp.202012770DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927661PMC
July 2021

Volumetric Capnography Monitoring and Effects of Epinephrine on Volume of Carbon Dioxide Elimination during Resuscitation after Cardiac Arrest in a Swine Pediatric Ventricular Fibrillatory Arrest.

J Pediatr Intensive Care 2021 Mar 1;10(1):31-37. Epub 2020 Jun 1.

Division of Pediatric Critical Care Medicine, Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States.

The aim of this study was to examine the use of volumetric capnography monitoring to assess cardiopulmonary resuscitation (CPR) effectiveness by correlating it with cardiac output (CO), and to evaluate the effect of epinephrine boluses on both end-tidal carbon dioxide (EtCO ) and the volume of CO elimination (VCO ) in a swine ventricular fibrillation cardiac arrest model. Planned secondary analysis of data collected to investigate the use of noninvasive monitors in a pediatric swine ventricular fibrillation cardiac arrest model was performed. Twenty-eight ventricular fibrillatory arrests with open cardiac massage were conducted. During CPR, EtCO and VCO had strong correlation with CO, measured as a percentage of baseline pulmonary blood flow, with correlation coefficients of 0.83 (  < 0.001) and 0.53 (  = 0.018), respectively. However, both EtCO and VCO had weak and nonsignificant correlation with diastolic blood pressure during CPR 0.30 (  = 0.484) (95% confidence interval [CI], -0.51-0.83) and 0.25 (  = 0.566) (95% CI, -0.55-0.81), respectively. EtCO and VCO increased significantly after the first epinephrine bolus without significant change in CO. The correlations between EtCO and VCO and CO were weak 0.20 (  = 0.646) (95% CI, -0.59-0.79), and 0.27 (  = 0.543) (95% CI, -0.54-0.82) following epinephrine boluses. Continuous EtCO and VCO monitoring are potentially useful metrics to ensure effective CPR. However, transient epinephrine administration by boluses might confound the use of EtCO and VCO to guide chest compression.
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http://dx.doi.org/10.1055/s-0040-1712531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7870341PMC
March 2021

Estrogen receptor-α prevents right ventricular diastolic dysfunction and fibrosis in female rats.

Am J Physiol Heart Circ Physiol 2020 12 16;319(6):H1459-H1473. Epub 2020 Oct 16.

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.

Although women are more susceptible to pulmonary arterial hypertension (PAH) than men, their right ventricular (RV) function is better preserved. Estrogen receptor-α (ERα) has been identified as a likely mediator for estrogen protection in the RV. However, the role of ERα in preserving RV function and remodeling during pressure overload remains poorly understood. We hypothesized that loss of functional ERα removes female protection from adverse remodeling and is permissive for the development of a maladapted RV phenotype. Male and female rats with a loss-of-function mutation in ERα (ERαMut) and wild-type (WT) littermates underwent RV pressure overload by pulmonary artery banding (PAB). At 10 wk post-PAB, WT and ERαMut demonstrated RV hypertrophy. Analysis of RV pressure waveforms demonstrated RV-pulmonary vascular uncoupling and diastolic dysfunction in female, but not male, ERαMut PAB rats. Similarly, female, but not male, ERαMut exhibited increased RV fibrosis, comprised primarily of thick collagen fibers. There was an increased protein expression ratio of TIMP metallopeptidase inhibitor 1 (Timp1) to matrix metalloproteinase 9 (Mmp9) in female ERαMut compared with WT PAB rats, suggesting less collagen degradation. RNA-sequencing in female WT and ERαMut RV revealed kallikrein-related peptidase 10 (Klk10) and Jun Proto-Oncogene (Jun) as possible mediators of female RV protection during PAB. In summary, ERα in females is protective against RV-pulmonary vascular uncoupling, diastolic dysfunction, and fibrosis in response to pressure overload. ERα appears to be dispensable for RV adaptation in males. ERα may be a mediator of superior RV adaptation in female patients with PAH. Using a novel loss-of-function mutation in estrogen receptor-α (ERα), we demonstrate that female, but not male, ERα mutant rats display right ventricular (RV)-vascular uncoupling, diastolic dysfunction, and fibrosis following pressure overload, indicating a sex-dependent role of ERα in protecting against adverse RV remodeling. TIMP metallopeptidase inhibitor 1 (Timp1), matrix metalloproteinase 9 (Mmp9), kallikrein-related peptidase 10 (), and Jun Proto-Oncogene () were identified as potential mediators in ERα-regulated pathways in RV pressure overload.
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http://dx.doi.org/10.1152/ajpheart.00247.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7792707PMC
December 2020

Single-dose mRNA therapy via biomaterial-mediated sequestration of overexpressed proteins.

Sci Adv 2020 07 1;6(27). Epub 2020 Jul 1.

Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53705, USA.

Nonviral mRNA delivery is an attractive therapeutic gene delivery strategy, as it achieves efficient protein overexpression in vivo and has a desirable safety profile. However, mRNA's short cytoplasmic half-life limits its utility to therapeutic applications amenable to repeated dosing or short-term overexpression. Here, we describe a biomaterial that enables a durable in vivo response to a single mRNA dose via an "overexpress and sequester" mechanism, whereby mRNA-transfected cells locally overexpress a growth factor that is then sequestered within the biomaterial to sustain the biologic response over time. In a murine diabetic wound model, this strategy demonstrated improved wound healing compared to delivery of a single mRNA dose alone or recombinant protein. In addition, codelivery of anti-inflammatory proteins using this biomaterial eliminated the need for mRNA chemical modification for in vivo therapeutic efficacy. The results support an approach that may be broadly applicable for single-dose delivery of mRNA without chemical modification.
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http://dx.doi.org/10.1126/sciadv.aba2422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458450PMC
July 2020

Bimodal right ventricular dysfunction after postnatal hyperoxia exposure: implications for the preterm heart.

Am J Physiol Heart Circ Physiol 2019 12 8;317(6):H1272-H1281. Epub 2019 Nov 8.

Department of Medicine, School of Medicine and Public Health, University of Madison-Wisconsin, Madison, Wisconsin.

Rats exposed to postnatal hyperoxia develop right ventricular (RV) dysfunction, mild pulmonary hypertension, and dysregulated cardiac mitochondrial biogenesis when aged to one year, with the degree of cardiac dysfunction and pulmonary hypertension similar to that previously described in young adults born preterm. Here, we sought to understand the impact of postnatal hyperoxia exposure on RV hemodynamic and mitochondrial function across the life span. In Methods, pups from timed-pregnant Sprague-Dawley rats were randomized to normoxia or hyperoxia [fraction of inspired oxygen (), 0.85] exposure for the first 14 days of life, a commonly used model of chronic lung disease of prematurity. RV hemodynamic and mitochondrial function were assessed by invasive measurement of RV pressure-volume loops and by high-resolution respirometry at (P21), P90, and P365. In Results, at P21, hyperoxia-exposed rats demonstrated severe pulmonary hypertension and RV dysfunction, accompanied by depressed mitochondrial oxidative capacity. However, significant upregulation of mitochondrial biogenesis at P21 as well as improved afterload led to complete RV hemodynamic and mitochondrial recovery at P90. Mitochondrial DNA mutations were significantly higher by P90 and associated with significant late RV mitochondrial and hemodynamic dysfunction at P365. In conclusion, there appears to be a "honeymoon period" where cardiac hemodynamic and mitochondrial function normalizes following postnatal hyperoxia exposure, only to decline again with ongoing aging. This finding may have significant implications if a long-term pulmonary vascular screening program were to be developed for children or adults with a history of severe prematurity. Further investigation into the mechanisms of recovery are warranted. Premature birth is associated with increased risk for cardiac dysfunction and failure throughout life. Here, we identify bimodal right ventricular dysfunction after postnatal hyperoxia exposure. Mitochondrial biogenesis serves as an early adaptive feature promoting recovery of cardiac hemodynamic and mitochondrial function. However, the accumulation of mitochondrial DNA mutations results in late mitochondrial and right ventricular dysfunction. This bimodal right ventricular dysfunction may have important implications for the development of screening programs in the preterm population.
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http://dx.doi.org/10.1152/ajpheart.00383.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6962619PMC
December 2019

Ultrasonography of the Adult Male Urinary Tract for Urinary Functional Testing.

J Vis Exp 2019 08 14(150). Epub 2019 Aug 14.

Department of Urology, University of Wisconsin-Madison; U54 George M. O'Brien Center, University of Wisconsin-Madison;

The incidence of clinical benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS) is increasing due to the aging population, resulting in a significant economic and quality of life burden. Transgenic and other mouse models have been developed to recreate various aspects of this multifactorial disease; however, methods to accurately quantitate urinary dysfunction and the effectiveness of new therapeutic options are lacking. Here, we describe a method that can be used to measure bladder volume and detrusor wall thickness, urinary velocity, void volume and void duration, and urethral diameter. This would allow for the evaluation of disease progression and treatment efficacy over time. Mice were anesthetized with isoflurane, and the bladder was visualized by ultrasound. For non-contrast imaging, a 3D image was taken of the bladder to calculate volume and evaluate shape; the bladder wall thickness was measured from this image. For contrast-enhanced imaging, a catheter was placed through the dome of the bladder using a 27-gauge needle connected to a syringe by PE50 tubing. A bolus of 0.5 mL of contrast was infused into the bladder until a urination event occurred. Urethral diameter was determined at the point of the Doppler velocity sample window during the first voiding event. Velocity was measured for each subsequent event yielding a flow rate. In conclusion, high frequency ultrasound proved to be an effective method for assessing bladder and urethral measurements during urinary function in mice. This technique may be useful in the assessment of novel therapies for BPH/LUTS in an experimental setting.
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http://dx.doi.org/10.3791/59802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7328372PMC
August 2019

MicroRNA let-7-TGFBR3 signalling regulates cardiomyocyte apoptosis after infarction.

EBioMedicine 2019 Aug 7;46:236-247. Epub 2019 Aug 7.

Institute of Biomedical Science, Academia Sinica, Taipei, Taiwan; Department of Medicine, University of Wisconsin-Madison, Madison, WI, United States; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, United States; Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan; Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan; Division of Cardiovascular Surgery, Department of Surgery, National Taiwan University Hospital, Taipei 100, Taiwan. Electronic address:

Background: Myocardial infarction (MI) is a life-threatening disease, often leading to heart failure. Defining therapeutic targets at an early time point is important to prevent heart failure.

Methods: MicroRNA screening was performed at early time points after MI using paired samples isolated from the infarcted and remote myocardium of pigs. We also examined the microRNA expression in plasma of MI patients and pigs. For mechanistic studies, AAV9-mediated microRNA knockdown and overexpression were administrated in mice undergoing MI.

Findings: MicroRNAs let-7a and let-7f were significantly downregulated in the infarct area within 24 h post-MI in pigs. We also observed a reduction of let-7a and let-7f in plasma of MI patients and pigs. Inhibition of let-7 exacerbated cardiomyocyte apoptosis, induced a cardiac hypertrophic phenotype, and resulted in worsened left ventricular ejection fraction. In contrast, ectopic let-7 overexpression significantly reduced those phenotypes and improved heart function. We then identified TGFBR3 as a target of let-7, and found that induction of Tgfbr3 in cardiomyocytes caused apoptosis, likely through p38 MAPK activation. Finally, we showed that the plasma TGFBR3 level was elevated after MI in plasma of MI patients and pigs.

Interpretation: Together, we conclude that the let-7-Tgfbr3-p38 MAPK signalling plays an important role in cardiomyocyte apoptosis after MI. Furthermore, microRNA let-7 and Tgfbr3 may serve as therapeutic targets and biomarkers for myocardial damage. FUND: Ministry of Science and Technology, National Health Research Institutes, Academia Sinica Program for Translational Innovation of Biopharmaceutical Development-Technology Supporting Platform Axis, Thematic Research Program and the Summit Research Program, Taiwan.
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http://dx.doi.org/10.1016/j.ebiom.2019.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6712055PMC
August 2019

Significant reduction of ischemia-reperfusion cell death in mouse myocardial infarcts using the immediate-acting PrC-210 ROS-scavenger.

Pharmacol Res Perspect 2019 08 12;7(4):e00500. Epub 2019 Jul 12.

Wisconsin Institutes for Medical Research University of Wisconsin-Madison Madison Wisconsin.

Managing myocardial infarction (MI) to reduce cardiac cell death relies primarily on timely reperfusion of the affected coronary site, but reperfusion itself induces cell death through a toxic, ROS-mediated process. In this study, we determined whether the PrC-210 aminothiol ROS-scavenger could prevent ROS-induced damage in post-MI hearts. In a series of both in vitro and in vivo experiments, we show that: (a) in vitro, PrC-210 was the most potent and effective ROS-scavenger when functionally compared to eight of the most commonly studied antioxidants in the MI literature, (b) in vitro PrC-210 ROS-scavenging efficacy was both immediate (seconds) and long-lasting (hours), which would make it effective in both (1) (), as post-MI or cardiac surgery hearts are reperfused with PrC-210-containing blood, and (2) (s) as hearts are bathed with systemic PrC-210 after MI or surgery, (c) systemic PrC-210 caused a significant 36% reduction of mouse cardiac muscle death following a 45-minute cardiac IR insult; in a striking coincidence, the PrC-210 36% reduction in cardiac muscle death equals the 36% of the MI-induced cardiac cell death estimated 6 years ago by Ovize and colleagues to result from "reperfusion injury," (d) hearts in PrC-210-treated mice performed better than controls after heart attacks when functionally analyzed using echocardiography, and (e) the PrC-210 ROS-scavenging mechanism of action was corroborated by its ability to prevent >85% of the direct, HO-induced killing of neonate cardiomyocytes in cell culture. PrC-210 does not cause the nausea, emesis, nor hypotension that preclude clinical use of the WR-1065/amifostine aminothiol. PrC-210 is a highly effective ROS-scavenger that significantly reduces IR injury-associated cardiac cell death.
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http://dx.doi.org/10.1002/prp2.500DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6625532PMC
August 2019

Epigenetic Priming of Human Pluripotent Stem Cell-Derived Cardiac Progenitor Cells Accelerates Cardiomyocyte Maturation.

Stem Cells 2019 07 14;37(7):910-923. Epub 2019 May 14.

Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) exhibit a fetal phenotype that limits in vitro and therapeutic applications. Strategies to promote cardiomyocyte maturation have focused interventions on differentiated hPSC-CMs, but this study tests priming of early cardiac progenitor cells (CPCs) with polyinosinic-polycytidylic acid (pIC) to accelerate cardiomyocyte maturation. CPCs were differentiated from hPSCs using a monolayer differentiation protocol with defined small molecule Wnt temporal modulation, and pIC was added during the formation of early CPCs. pIC priming did not alter the expression of cell surface markers for CPCs (>80% KDR+/PDGFRα+), expression of common cardiac transcription factors, or final purity of differentiated hPSC-CMs (∼90%). However, CPC differentiation in basal medium revealed that pIC priming resulted in hPSC-CMs with enhanced maturity manifested by increased cell size, greater contractility, faster electrical upstrokes, increased oxidative metabolism, and more mature sarcomeric structure and composition. To investigate the mechanisms of CPC priming, RNAseq revealed that cardiac progenitor-stage pIC modulated early Notch signaling and cardiomyogenic transcriptional programs. Chromatin immunoprecipitation of CPCs showed that pIC treatment increased deposition of the H3K9ac activating epigenetic mark at core promoters of cardiac myofilament genes and the Notch ligand, JAG1. Inhibition of Notch signaling blocked the effects of pIC on differentiation and cardiomyocyte maturation. Furthermore, primed CPCs showed more robust formation of hPSC-CMs grafts when transplanted to the NSGW mouse kidney capsule. Overall, epigenetic modulation of CPCs with pIC accelerates cardiomyocyte maturation enabling basic research applications and potential therapeutic uses. Stem Cells 2019;37:910-923.
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http://dx.doi.org/10.1002/stem.3021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599574PMC
July 2019

Beneficial effects of mesenchymal stem cell delivery via a novel cardiac bioscaffold on right ventricles of pulmonary arterial hypertensive rats.

Am J Physiol Heart Circ Physiol 2019 05 1;316(5):H1005-H1013. Epub 2019 Mar 1.

Department of Biomedical Engineering, University of Wisconsin , Madison, Wisconsin.

Right ventricular failure (RVF) is a common cause of death in patients suffering from pulmonary arterial hypertension (PAH). The current treatment for PAH only moderately improves symptoms, and RVF ultimately occurs. Therefore, it is necessary to develop new treatment strategies to protect against right ventricle (RV) maladaptation despite PAH progression. In this study, we hypothesize that local mesenchymal stem cell (MSC) delivery via a novel bioscaffold can improve RV function despite persistent PAH. To test our hypothesis, we induced PAH in adult rats with SU5416 and chronic hypoxia exposure; treated with rat MSCs delivered by intravenous injection, intramyocardial injection, or epicardial placement of a bioscaffold; and then examined treatment effectiveness by in vivo pressure-volume measurement, echocardiography, histology, and immunohistochemistry. Our results showed that compared with other treatment groups, only the MSC-seeded bioscaffold group resulted in RV functional improvement, including restored stroke volume, cardiac output, and improved stroke work. Diastolic function indicated by end-diastolic pressure-volume relationship was improved by the local MSC treatments or bioscaffold alone. Cardiomyocyte hypertrophy and RV fibrosis were both reduced, and von Willebrand factor expression was restored by the MSC-seeded bioscaffold treatment. Overall, our study suggests a potential new regenerative therapy to rescue the pressure-overload failing RV with persistent pulmonary vascular disease, which may improve quality of life and/or survival of PAH patients. NEW & NOTEWORTHY We explored the effects of mesenchymal stem cell-seeded bioscaffold on right ventricles (RVs) of rats with established pulmonary arterial hypertension (PAH). Some beneficial effects were observed despite persistent PAH, suggesting that this may be a new therapy for RV to improve quality of life and/or survival of PAH patients.
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http://dx.doi.org/10.1152/ajpheart.00091.2018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6580387PMC
May 2019

Two-site regional oxygen saturation and capnography monitoring during resuscitation after cardiac arrest in a swine pediatric ventricular fibrillatory arrest model.

J Clin Monit Comput 2020 Feb 28;34(1):63-70. Epub 2019 Feb 28.

Division of Pediatric Critical Care Medicine, Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.

Abstarct: To investigate the use of two-site regional oxygen saturations (rSO) and end tidal carbon dioxide (EtCO) to assess the effectiveness of resuscitation and return of spontaneous circulation (ROSC). Eight mechanically ventilated juvenile swine underwent 28 ventricular fibrillatory arrests with open cardiac massage. Cardiac massage was administered to achieve target pulmonary blood flow (PBF) as a percentage of pre-cardiac arrest baseline. Non-invasive data, including, EtCO, cerebral rSO (C-rSO) and renal rSO (R-rSO) were collected continuously. Our data demonstrate the ability to measure both rSO and EtCO during CPR and after ROSC. During resuscitation EtCO had a strong correlation with goal CO with r = 0.83 (p < 0.001) 95% CI [0.67-0.92]. Both C-rSO and R-rSO had moderate and statistically significant correlation with CO with r = 0.52 (p = 0.003) 95% CI (0.19-0.74) and 0.50 (p = 0.004) 95% CI [0.16-0.73]. The AUCs for sudden increase of EtCO, C-rSO, and R-rSO at ROSC were 0.86 [95% CI, 0.77-0.94], 0.87 [95% CI, 0.8-0.94], and 0.98 [95% CI, 0.96-1.00] respectively. Measurement of continuous EtCO and rSO may be used during CPR to ensure effective chest compressions. Moreover, both rSO and EtCO may be used to detect ROSC in a swine pediatric ventricular fibrillatory arrest model.
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http://dx.doi.org/10.1007/s10877-019-00291-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7223879PMC
February 2020

Pulmonary vascular mechanical consequences of ischemic heart failure and implications for right ventricular function.

Am J Physiol Heart Circ Physiol 2019 05 15;316(5):H1167-H1177. Epub 2019 Feb 15.

Department of Biomedical Engineering, University of Wisconsin-Madison College of Engineering , Madison, Wisconsin.

Left heart failure (LHF) is the most common cause of pulmonary hypertension, which confers an increase in morbidity and mortality in this context. Pulmonary vascular resistance has prognostic value in LHF, but otherwise the mechanical consequences of LHF for the pulmonary vasculature and right ventricle (RV) remain unknown. We sought to investigate mechanical mechanisms of pulmonary vascular and RV dysfunction in a rodent model of LHF to address the knowledge gaps in understanding disease pathophysiology. LHF was created using a left anterior descending artery ligation to cause myocardial infarction (MI) in mice. Sham animals underwent thoracotomy alone. Echocardiography demonstrated increased left ventricle (LV) volumes and decreased ejection fraction at 4 wk post-MI that did not normalize by 12 wk post-MI. Elevation of LV diastolic pressure and RV systolic pressure at 12 wk post-MI demonstrated pulmonary hypertension (PH) due to LHF. There was increased pulmonary arterial elastance and pulmonary vascular resistance associated with perivascular fibrosis without other remodeling. There was also RV contractile dysfunction with a 35% decrease in RV end-systolic elastance and 66% decrease in ventricular-vascular coupling. In this model of PH due to LHF with reduced ejection fraction, pulmonary fibrosis contributes to increased RV afterload, and loss of RV contractility contributes to RV dysfunction. These are key pathologic features of human PH secondary to LHF. In the future, novel therapeutic strategies aimed at preventing pulmonary vascular mechanical changes and RV dysfunction in the context of LHF can be tested using this model. In this study, we investigate the mechanical consequences of left heart failure with reduced ejection fraction for the pulmonary vasculature and right ventricle. Using comprehensive functional analyses of the cardiopulmonary system in vivo and ex vivo, we demonstrate that pulmonary fibrosis contributes to increased RV afterload and loss of RV contractility contributes to RV dysfunction. Thus this model recapitulates key pathologic features of human pulmonary hypertension-left heart failure and offers a robust platform for future investigations.
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http://dx.doi.org/10.1152/ajpheart.00319.2018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6580389PMC
May 2019

A Large Animal Model of Right Ventricular Failure due to Chronic Thromboembolic Pulmonary Hypertension: A Focus on Function.

Front Cardiovasc Med 2018 9;5:189. Epub 2019 Jan 9.

Department of Biomedical Engineering, Univeristy of Wisconsin-Madison, Madison, WI, United States.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating disease that progresses to right ventricular (RV) failure and death if left untreated. Little is known regarding the progression of RV failure in this disease, greatly limiting effective prognoses, and therapeutic interventions. Large animal models enable the use of clinical techniques and technologies to assess progression and diagnose failure, but the existing large animal models of CTEPH have not been shown to replicate the functional consequences of the RV, i.e., RV failure. Here, we created a canine embolization model of CTEPH utilizing only microsphere injections, and we used a combination of right heart catheterization (RHC), echocardiography (echo), and magnetic resonance imaging (MRI) to quantify RV function. Over the course of several months, CTEPH led to a 6-fold increase in pulmonary vascular resistance (PVR) in four adult, male beagles. As evidenced by decreased cardiac index (0.12 ± 0.01 v. 0.07 ± 0.01 [L/(minkg)]; < 0.05), ejection fraction (0.48 ± 0.02 v. 0.31 ± 0.02; < 0.05), and ventricular-vascular coupling ratio (0.95 ± 0.09 v. 0.45 ± 0.05; < 0.05), as well as decreased tricuspid annular plane systolic excursion (TAPSE) (1.37 ± 0.06 v. 0.86 ± 0.05 [cm]; < 0.05) and increased end-diastolic volume index (2.73 ± 0.06 v. 2.98 ± 0.02 [mL/kg]; < 0.05), the model caused RV failure. The ability of this large animal CTEPH model to replicate the hemodynamic consequences of the human disease suggests that it could be utilized for future studies to gain insight into the pathophysiology of CTEPH development, following further optimization.
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http://dx.doi.org/10.3389/fcvm.2018.00189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6333696PMC
January 2019

Loss of Gut Microbiota Alters Immune System Composition and Cripples Postinfarction Cardiac Repair.

Circulation 2019 01;139(5):647-659

Program in Molecular Medicine, National Yang Ming University and Academia Sinica, Taipei, Taiwan (T.W.H.T., P.C.C.H.).

Background: The impact of gut microbiota on the regulation of host physiology has recently garnered considerable attention, particularly in key areas such as the immune system and metabolism. These areas are also crucial for the pathophysiology of and repair after myocardial infarction (MI). However, the role of the gut microbiota in the context of MI remains to be fully elucidated.

Methods: To investigate the effects of gut microbiota on cardiac repair after MI, C57BL/6J mice were treated with antibiotics 7 days before MI to deplete mouse gut microbiota. Flow cytometry was applied to examine the changes in immune cell composition in the heart. 16S rDNA sequencing was conducted as a readout for changes in gut microbial composition. Short-chain fatty acid (SCFA) species altered after antibiotic treatment were identified by high-performance liquid chromatography. Fecal reconstitution, transplantation of monocytes, or dietary SCFA or Lactobacillus probiotic supplementation was conducted to evaluate the cardioprotective effects of microbiota on the mice after MI.

Results: Antibiotic-treated mice displayed drastic, dose-dependent mortality after MI. We observed an association between the gut microbiota depletion and significant reductions in the proportion of myeloid cells and SCFAs, more specifically acetate, butyrate, and propionate. Infiltration of CX3CR1+ monocytes to the peri-infarct zone after MI was also reduced, suggesting impairment of repair after MI. Accordingly, the physiological status and survival of mice were significantly improved after fecal reconstitution, transplantation of monocytes, or dietary SCFA supplementation. MI was associated with a reorganization of the gut microbial community such as a reduction in Lactobacillus. Supplementing antibiotic-treated mice with a Lactobacillus probiotic before MI restored myeloid cell proportions, yielded cardioprotective effects, and shifted the balance of SCFAs toward propionate.

Conclusions: Gut microbiota-derived SCFAs play an important role in maintaining host immune composition and repair capacity after MI. This suggests that manipulation of these elements may provide opportunities to modulate pathological outcome after MI and indeed human health and disease as a whole.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.118.035235DOI Listing
January 2019

Animal Models and Cardiac Extracellular Matrix Research.

Authors:
Timothy A Hacker

Adv Exp Med Biol 2018;1098:45-58

Cardiovascular Research Center, Department of Medicine, University of Wisconsin, Madison, WI, USA.

Cardiovascular disease has been the leading cause of death worldwide for the last 15 years, accounting for 15 million deaths per year. While interventions are saving more lives, more than 20% of survivors will end up in heart failure. Cell-based and other types of therapy for advanced heart and vascular disease may offer new hope for those afflicted. Although a variety of cell types are under investigation, common issues include cell survival, retention, engraftment, and proliferation. Cardiac extracellular matrix (C-ECM) has compelling features that offer advantages to not only aid cell survival, retention, engraftment, and proliferation but likely has independent therapeutic (paracrine) and mechanical effects. Animal studies and clinical trials are underway to characterize the role of C-ECM and demonstrate efficacy for acute and chronic heart disease. This chapter reviews animal models used to enhance our knowledge of C-ECMs in heart disease and its use in the treatment of heart disease.
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http://dx.doi.org/10.1007/978-3-319-97421-7_3DOI Listing
February 2019

Cardiovascular function and structure are preserved despite induced ablation of BMP1-related proteinases.

Cell Mol Bioeng 2018 Aug 5;11(4):255-266. Epub 2018 Jun 5.

Department of Biomedical Engineering, University of Wisconsin-Madison College of Engineering, Madison, WI 53706 USA.

Introduction: Bone morphogenetic protein 1 (BMP1) is part of an extracellular metalloproteinase family that biosynthetically processes procollagen molecules. BMP1- and tolloid-like (TLL1) proteinases mediate the cleavage of carboxyl peptides from procollagen molecules, which is a crucial step in fibrillar collagen synthesis. Ablating the genes that encode BMP1-related proteinases ( and ) post-natally results in brittle bones, periodontal defects, and thin skin in conditional knockout (BT) mice. Despite the importance of collagen to cardiovascular tissues and the adverse effects of and ablation in other tissues, the impact of and ablation on cardiovascular performance is unknown. Here, we investigated the role of - and -ablation in cardiovascular tissues by examining ventricular and vascular structure and function in BT mice.

Methods: Ventricular and vascular structure and function were comprehensively quantified in BT mice (n=9) and in age- and sex-matched controls (n=9). Echocardiography, cardiac catheterization, and biaxial arterial mechanical testing were performed to assess tissue function, and histological staining was used to measure collagen protein content.

Results: - and -ablation resulted in maintained hemodynamics and cardiovascular function, preserved biaxial arterial compliance, and comparable ventricular and vascular collagen protein content.

Conclusions: Maintained ventricular and vascular structure and function despite post-natal ablation of and suggests that there is an as-yet unidentified compensatory mechanism in cardiovascular tissues. In addition, these findings suggest that proteinases derived from and post-natally have less of an impact on cardiovascular tissues compared to skeletal, periodontal, and dermal tissues.
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http://dx.doi.org/10.1007/s12195-018-0534-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6094387PMC
August 2018

Real-Time in Vivo Photoacoustic Imaging in the Assessment of Myocardial Dynamics in Murine Model of Myocardial Ischemia.

Ultrasound Med Biol 2018 10 29;44(10):2155-2164. Epub 2018 Jul 29.

Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, USA; Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA. Electronic address:

Photoacoustic imaging (PAI) is an evolving real-time imaging modality that combines the higher contrast of optical imaging with the higher spatial resolution of ultrasound imaging. We utilized dual-wavelength PAI for the diagnosis and monitoring of myocardial ischemia by assessing variations in blood oxygen saturation estimated in a murine model. The use of high-frequency ultrasound in conjunction with PAI enabled imaging of anatomic and functional changes associated with ischemia. Myocardial ischemia was established in eight mice by ligating the left anterior descending artery (LAD). Longitudinal results reveal that PAI is sensitive to acute myocardial ischemia, with a rapid decline in blood oxygen saturation (p ˂ 0.001) observed after LAD ligation (30 min: 33.05 ± 6.80%, 80 min: 36.59 ± 5.22%, 120 min: 36.70 ± 9.46%, 24 h: 40.55 ± 13.04%) compared with baseline (87.83 ± 5.73%). Variation in blood oxygen saturation was found to be linearly correlated with ejection fraction (%), fractional shortening (%) and stroke volume (µL), with Pearson's correlation coefficient values of 0.66, 0.67 and 0.77, respectively (p ˂ 0.001). Our results indicate that PAI has the potential for real-time diagnosis and monitoring of acute myocardial ischemia.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2018.05.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135705PMC
October 2018

Increased transport of acetyl-CoA into the endoplasmic reticulum causes a progeria-like phenotype.

Aging Cell 2018 Oct 27;17(5):e12820. Epub 2018 Jul 27.

Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin.

The membrane transporter AT-1/SLC33A1 translocates cytosolic acetyl-CoA into the lumen of the endoplasmic reticulum (ER), participating in quality control mechanisms within the secretory pathway. Mutations and duplication events in AT-1/SLC33A1 are highly pleiotropic and have been linked to diseases such as spastic paraplegia, developmental delay, autism spectrum disorder, intellectual disability, propensity to seizures, and dysmorphism. Despite these known associations, the biology of this key transporter is only beginning to be uncovered. Here, we show that systemic overexpression of AT-1 in the mouse leads to a segmental form of progeria with dysmorphism and metabolic alterations. The phenotype includes delayed growth, short lifespan, alopecia, skin lesions, rectal prolapse, osteoporosis, cardiomegaly, muscle atrophy, reduced fertility, and anemia. In terms of homeostasis, the AT-1 overexpressing mouse displays hypocholesterolemia, altered glycemia, and increased indices of systemic inflammation. Mechanistically, the phenotype is caused by a block in Atg9a-Fam134b-LC3β and Atg9a-Sec62-LC3β interactions, and defective reticulophagy, the autophagic recycling of the ER. Inhibition of ATase1/ATase2 acetyltransferase enzymes downstream of AT-1 restores reticulophagy and rescues the phenotype of the animals. These data suggest that inappropriately elevated acetyl-CoA flux into the ER directly induces defects in autophagy and recycling of subcellular structures and that this diversion of acetyl-CoA from cytosol to ER is causal in the progeria phenotype. Collectively, these data establish the cytosol-to-ER flux of acetyl-CoA as a novel event that dictates the pace of aging phenotypes and identify intracellular acetyl-CoA-dependent homeostatic mechanisms linked to metabolism and inflammation.
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http://dx.doi.org/10.1111/acel.12820DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6156544PMC
October 2018

In vivo imaging of inflammation and oxidative stress in a nonhuman primate model of cardiac sympathetic neurodegeneration.

NPJ Parkinsons Dis 2018 13;4:22. Epub 2018 Jul 13.

1Preclinical Parkinson's Research Program, Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI USA.

Loss of cardiac postganglionic sympathetic innervation is a characteristic pathology of Parkinson's disease (PD). It progresses over time independently of motor symptoms and is not responsive to typical anti-parkinsonian therapies. Cardiac sympathetic neurodegeneration can be mimicked in animals using systemic dosing of the neurotoxin 6-hydroxydopamine (6-OHDA). As in PD, 6-OHDA-induced neuronal loss is associated with increased inflammation and oxidative stress. To assess the feasibility of detecting changes over time in cardiac catecholaminergic innervation, inflammation, and oxidative stress, myocardial positron emission tomography with the radioligands [C]-hydroxyephedrine (MHED), [C]PBR28 (PBR28), and [Cu]diacetyl-((4))-methylthiosemicarbazone (ATSM) was performed in 6-OHDA-intoxicated adult, male rhesus macaques ( = 10; 50 mg/kg i.v.). The peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone, which is known to have anti-inflammatory and anti-oxidative stress properties, was administered to five animals (5 mg/kg, PO); the other five were placebo-treated. One week after 6-OHDA, cardiac MHED uptake was significantly reduced in both groups (placebo, 86% decrease; pioglitazone, 82%); PBR28 and ATSM uptake increased in both groups but were attenuated in pioglitazone-treated animals (PBR28 Treatment × Level ANOVA  < 0.002; ATSM Mann-Whitney  = 0.032). At 12 weeks, partial recovery of MHED uptake was significantly greater in the pioglitazone-treated group, dependent on left ventricle circumferential region and axial level (Treatment × Region × Level ANOVA  = 0.034); 12-week MHED uptake significantly correlated with tyrosine hydroxylase immunoreactivity across cardiac anatomy ( < 0.000002). PBR28 and ATSM uptake returned to baseline levels by 12 weeks. These radioligands thus hold potential as in vivo biomarkers of mechanisms of cardiac neurodegeneration and neuroprotection.
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http://dx.doi.org/10.1038/s41531-018-0057-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045637PMC
July 2018

Transgenic overexpression of the SUR2A-55 splice variant in mouse heart reduces infract size and promotes protective mitochondrial function.

Heliyon 2018 Jul 4;4(7):e00677. Epub 2018 Jul 4.

Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States.

ATP-sensitive potassium channels found in both the sarcolemma (sarcK) and mitochondria (mitoK) of cardiomyocytes are important mediators of cardioprotection during ischemic heart disease. Sulfonylurea receptor isoforms (SUR2), encoded by , an ATP-binding cassette family member, form regulatory subunits of the sarcK channel and are also thought to regulate mitoK channel activity. A short-form splice variant of SUR2 (SUR2A-55) was previously shown to target mitochondria and display diaxoxide and ATP insensitive K activity when co-expressed with the inward rectifier channels Kir6.2 and Kir6.1. We hypothesized that mice with cardiac specific overexpression of SUR2A-55 would mediate cardioprotection from ischemia by altering mitoK properties. Mice overexpressing SUR2A-55 (TG) in cardiomyocytes were generated and showed no significant difference in echocardiographic measured chamber dimension, percent fractional shortening, heart to body weight ratio, or gross histologic features compared to normal mice at 11-14 weeks of age. TG had improved hemodynamic functional recovery and smaller infarct size after ischemia reperfusion injury compared to WT mice in an isolated hanging heart model. The mitochondrial membrane potential of TG mice was less sensitive to ATP, diazoxide, and Ca loading. These data suggest that the SUR2A-55 splice variant favorably affects mitochondrial function leading to cardioprotection. These data support a role for the regulation of mitoK activity by SUR2A-55.
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http://dx.doi.org/10.1016/j.heliyon.2018.e00677DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037880PMC
July 2018

Does prenatal alcohol exposure cause a metabolic syndrome? (Non-)evidence from a mouse model of fetal alcohol spectrum disorder.

PLoS One 2018 28;13(6):e0199213. Epub 2018 Jun 28.

UNC Nutritional Research Institute and Department of Nutrition, University of North Carolina-Chapel Hill, Kannapolis, North Carolina, United States of America.

Although prenatal alcohol exposure (PAE) reduces offspring growth, it may increase obesity risk at adolescence. Animal models of PAE display glucose intolerance and increased adiposity, suggesting that PAE causes metabolic reprogramming. We tested this hypothesis in a mouse model of binge PAE, wherein pregnant C57Bl/6J females received 3 g/kg alcohol (ETOH) daily from gestational day 12.5 to 17.5; maltodextrin (MD) and medium chain triglycerides (MCT) served as isocaloric nutritional controls, and sham (H2O) treatment controlled for gavage stress. Our comprehensive assessment quantified body composition, energy expenditure, glucose tolerance, and cardiovascular function in offspring at age 17 weeks. Although ETOH pups were initially lighter than all other groups, they did not have a unique obesogenic phenotype. Instead, a similar obesogenic phenotype emerged in all three caloric groups (MCT, MD, ETOH), such that caloric groups had greater post-weaning weight gain (both sexes), reduced gonadal fat weight (males), and reduced glucose clearance (males) compared against H2O offspring. PAE did not affect body composition, respiratory exchange ratio, metabolic adaption to high-fat or low-fat diet, eating behavior, and blood pressure, and ETOH values did not differ from those obtained from isocaloric controls. Exposure to a higher alcohol dose (4.5 g/kg) or a high-fat (60%) diet did not exacerbate differences in body composition or glucose tolerance. "PAE-specific" effects on postnatal growth, glucose tolerance, adiposity, or hypertension only emerged when PAE offspring were compared just against H2O controls, or against MD controls. We conclude that prior reports of obesity and glucose intolerance in adult PAE offspring reflect the contribution of added gestational calories, and not alcohol's pharmacologic action. Results suggest that the increased adiposity risk in FASD is not caused by metabolic reprogramming, and instead originates from behavioral, medication, and/or dietary practices. This study highlights the importance of appropriate dietary controls in nutritional studies of PAE.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199213PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023152PMC
April 2019

Multiscale structure-function relationships in right ventricular failure due to pressure overload.

Am J Physiol Heart Circ Physiol 2018 09 8;315(3):H699-H708. Epub 2018 Jun 8.

Department of Biomedical Engineering, University of Wisconsin-Madison College of Engineering , Madison, Wisconsin.

Right ventricular (RV) failure (RVF) is the major cause of death in pulmonary hypertension. Recent studies have characterized changes in RV structure in RVF, including hypertrophy, fibrosis, and abnormalities in mitochondria. Few, if any, studies have explored the relationships between these multiscale structural changes and functional changes in RVF. Pulmonary artery banding (PAB) was used to induce RVF due to pressure overload in male rats. Eight weeks postsurgery, terminal invasive measurements demonstrated RVF with decreased ejection fraction (70 ± 10 vs. 45 ± 15%, sham vs. PAB, P < 0.005) and cardiac output (126 ± 40 vs. 67 ± 32 ml/min, sham vs. PAB, P < 0.05). At the organ level, RV hypertrophy was directly correlated with increased contractility, which was insufficient to maintain ventricular-vascular coupling. At the tissue level, there was a 90% increase in fibrosis that had a direct correlation with diastolic dysfunction measured by reduced chamber compliance ( r = 0.43, P = 0.008). At the organelle level, transmission electron microscopy demonstrated an abundance of small-sized mitochondria. Increased mitochondria was associated with increased ventricular oxygen consumption and reduced mechanical efficiency ( P < 0.05). These results demonstrate an association between alterations in mitochondria and RV oxygen consumption and mechanical inefficiency in RVF and a link between fibrosis and in vivo diastolic dysfunction. Overall, this work provides key insights into multiscale RV remodeling in RVF due to pressure overload. NEW & NOTEWORTHY This study explores the functional impact of multiscale ventricular remodeling in right ventricular failure (RVF). It demonstrates correlations between hypertrophy and increased contractility as well as fibrosis and diastolic function. This work quantifies mitochondrial ultrastructural remodeling in RVF and demonstrates increased oxygen consumption and mechanical inefficiency as features of RVF. Direct correlation between mitochondrial changes and ventricular energetics provides insight into the impact of organelle remodeling on organ level function.
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http://dx.doi.org/10.1152/ajpheart.00047.2018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6172642PMC
September 2018
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