Tendon biomechanical properties and fibril organization are altered in patients with diabetes compared to healthy individuals, yet few biomarkers have been associated with in vivo tendon properties. We investigated the relationships between in vivo imaging-based tendon properties, serum variables, and patient characteristics across healthy controls (n = 14, age: 45 +/- 5 years, body mass index [BMI]: 24 +/- 1, hemoglobin A1c [HbA1c]: 5.3 +/- 0.1%), prediabetes (n = 14, age: 54 +/- 5 years, BMI: 29 +/- 2; HbA1c: 5.7 +/- 0.1), and type 2 diabetes (n = 13, age: 55 +/- 3 years, BMI: 33 +/- 2, HbA1c: 6.7 +/- 0.3). We used ultrasound speckle-tracking and measurements from magnetic resonance imaging (MRI) to estimate the patellar tendon in vivo tangent modulus. Analysis of plasma c-peptide, interleukin-1 beta (IL-1 beta), IL-6, IL-8, tumor necrosis factor-alpha (TNF-alpha), adiponectin, leptin, insulin-like growth factor 1 (IGF-1), and C-reactive protein (CRP) was completed. We built regression models incorporating statistically significant covariates and indicators for the clinically defined groups. We found that tendon cross-sectional area normalized to body weight (BWN CSA) and modulus were lower in patients with type 2 diabetes than in healthy controls (p < 0.05). Our regression analysis revealed that a model that included BMI, leptin, high-density lipoprotein (HDL), low-density lipoprotein (LDL), age, and group explained similar to 70% of the variability in BWN CSA (R-2 = 0.70, p < 0.001). For modulus, including the main effects LDL, groups, HbA1c, age, BMI, cholesterol, IGF-1, c-peptide, leptin, and IL-6, accounted for similar to 54% of the variability in modulus (R-2 = 0.54, p < 0.05). While BWN CSA and modulus were lower in those with diabetes, group was a poor predicter of tendon properties when considering the selected covariates. These data highlight the multifactorial nature of tendon changes with diabetes and suggest that blood variables could be reliable predictors of tendon properties.

Aortic valve (AV) disease is a common valvular lesion in the United States, present in about 5

Cranial dura mater is a dense interwoven vascularized connective tissue that helps regulate neurocranial remodeling by responding to strains from the growing brain. Previous ex vivo experimentation has failed to account for the role of prestretch in the mechanical behavior of the dura. Here we aim to estimate the prestretch in mouse cranial dura mater and determine its dependency on direction and age. We performed transverse and longitudinal incisions in parietal dura excised from newborn (day ∼ 4) and mature (12 weeks) mice and calculated the ex vivo normalized incision opening (measured width over length). Then, similar incisions were simulated under isotropic stretching within Abaqus/Standard. Finally, prestretch was estimated by comparing the ex vivo and in silico normalized openings. There were no significant differences between the neonatal and adult mice when comparing cuts in the same direction, but adult mice were found to have significantly greater stretch in the anterior–posterior direction than in the medial–lateral direction, while neonatal dura was essentially isotropic. Additionally, our simulations show that increasing curvature impacts the incision opening, indicating that flat in silico models may overestimate prestretch.

Background: Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, increases thromboembolic stroke risk five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function remain unknown. We tested the hypothesis that increased expression of PPP1R12C, the PP1 regulatory subunit targeting atrial myosin light chain 2 (MLC2a), causes hypophosphorylation of MLC2a and results in atrial hypocontractility. Methods: Right atrial appendage tissues were isolated from human AF patients versus sinus rhythm (SR) controls. Western blots, co-immunoprecipitation, and phosphorylation studies were performed to examine how the PP1c-PPP1R12C interaction causes MLC2a de-phosphorylation. In vitro studies of pharmacologic MRCK inhibitor (BDP5290) in atrial HL-1 cells were performed to evaluate PP1 holoenzyme activity on MLC2a. Cardiac-specific lentiviral PPP1R12C overexpression was performed in mice to evaluate atrial remodeling with atrial cell shortening assays, echocardiography, and AF inducibility with EP studies. Results: In human patients with AF, PPP1R12C expression was increased two-fold versus SR controls with > 40% reduction in MLC2a phosphorylation. 12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies utilizing drug BDP5290, which inhibits T560-PPP1R12C phosphorylation, demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Lenti-12C mice demonstrated a 150% increase in LA size versus controls, with reduced atrial strain and atrial ejection fraction. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusions: AF patients exhibit increased levels of PPP1R12C protein compared to controls. PPP1R12C overexpression in mice increases PP1c targeting to MLC2a and causes MLC2a dephosphorylation, which reduces atrial contractility and increases AF inducibility. These findings suggest that PP1 regulation of sarcomere function at MLC2a is a key regulator of atrial contractility in AF.

BACKGROUND:Cardiomyopathy (CMP) is the most common cause of mortality in Duchenne muscular dystrophy (DMD), though the age of onset and clinical progression vary. We applied a novel 4D (3D + time) strain analysis method using cine cardiovascular magnetic resonance (CMR) imaging data to determine if localized strain metrics derived from 4D image analysis would be sensitive and specific for characterizing DMD CMP. METHODS:We analyzed short-axis cine CMR image stacks from 43 DMD patients (median age: 12.23 yrs [10.6-16.5]; [interquartile range]) and 25 male healthy controls (median age: 16.2 yrs [13.3-20.7]). A subset of 25 male DMD patients age-matched to the controls (median age: 15.7 yrs [14.0-17.8]) was used for comparative metrics. CMR images were compiled into 4D sequences for feature-tracking strain analysis using custom-built software. Unpaired t-test and receiver operator characteristic area under the curve (AUC) analysis were used to determine statistical significance. Spearman's rho was used to determine correlation. RESULTS:DMD patients had a range of CMP severity: 15 (35% of total) had left ventricular ejection fraction (LVEF) > 55% with no findings of myocardial late gadolinium enhancement (LGE), 15 (35%) had findings of LGE with LVEF > 55% and 13 (30%) had LGE with LVEF < 55%. The magnitude of the peak basal circumferential strain, basal radial strain, and basal surface area strain were all significantly decreased in DMD patients relative to healthy controls (p < 0.001) with AUC values of 0.80, 0.89, and 0.84 respectively for peak strain and 0.96, 0.91, and 0.98 respectively for systolic strain rate. Peak basal radial strain, basal radial systolic strain rate, and basal circumferential systolic strain rate magnitude values were also significantly decreased in mild CMP (No LGE, LVEF > 55%) compared to a healthy control group (p < 0.001 for all). Surface area strain significantly correlated with LVEF and extracellular volume (ECV) respectively in the basal (rho = - 0.45, 0.40), mid (rho = - 0.46, 0.46), and apical (rho = - 0.42, 0.47) regions. CONCLUSION:Strain analysis of 3D cine CMR images in DMD CMP patients generates localized kinematic parameters that strongly differentiate disease from control and correlate with LVEF and ECV.

A multimodal approach using both four-dimensional ultrasound (4DUS) and regional proteomics can help enhance our investigations of murine cardiomyopathy models. We present unique 4DUS-derived strain maps that provide a framework for both cross-sectional and longitudinal analysis of spatiotemporal cardiac function. We further detail and demonstrate an innovative 4DUS-proteomics z-score-based linear regression method, aimed at characterizing relationships between regional cardiac dysfunction and underlying mechanisms of disease.

OBJECTIVES:Systemic dehydration decreases total body blood volume; however, hemodynamic alterations at the level of local organs, such as the larynx, remain unclear. Here we sought to quantify superior thyroid artery (STA) blood flow after dehydration and rehydration using in vivo magnetic resonance angiography (MRA) and ultrasound imaging in a rat model. METHODS:Male Sprague-Dawley rats (N = 17) were included in this prospective, repeated measures design. Rats first underwent MRA to determine baseline STA cross-sectional area, followed by high-frequency in vivo ultrasound imaging to measure STA blood velocity at baseline. Next, rats were systemically dehydrated (water withholding), followed by rehydration (water ad-lib). Ultrasound imaging was repeated immediately after dehydration and following rehydration. The STA blood velocity and STA cross-sectional area were used to compute STA blood flow. Three rats served as temporal controls for ultrasound imaging. To determine if the challenges to hydration status affected the STA cross-sectional area, four rats underwent only MRA at baseline, dehydration, and rehydration. RESULTS:Systemic dehydration resulted in 10.5% average body weight loss. Rehydration resulted in average body weight gain of 10.9%. Statistically significant reductions were observed in STA mean blood flow rate after dehydration. Rehydration reversed these changes to pre-dehydration levels. No significant differences were observed in STA cross-sectional area with dehydration or rehydration. CONCLUSION:Systemic dehydration decreased blood flow in the superior thyroid artery. Rehydration restored blood flow in the STA. Change in hydration status did not alter the STA cross-sectional area. These preliminary findings demonstrate the feasibility of using ultrasound and MRA to quantify hemodynamic changes and visualize laryngeal blood vessels. LEVEL OF EVIDENCE:NA Laryngoscope, 134:779-785, 2024.

AIM:Retrospective studies suggest that mild traumatic brain injury (mTBI) in pediatric patients may lead to an increased risk of cardiac events. However, the exact functional and temporal dynamics and the associations between heart and brain pathophysiological trajectories are not understood. METHODS:A single impact to the left somatosensory cortical area of the intact skull was performed on juvenile mice (17 days postnatal). Cerebral 3D photoacoustic imaging was used to measure the oxygen saturation (sO2 ) in the impacted area 4 h after mTBI followed by 2D and 4D echocardiography at days 7, 30, 90, and 190 post-impact. At 8 months, we performed a dobutamine stress test to evaluate cardiac function. Lastly, behavioral analyses were conducted 1 year after initial injury. RESULTS:We report a rapid and transient decrease in cerebrovascular sO2 and increased hemoglobin in the impacted left brain cortex. Cardiac analyses showed long-term diastolic dysfunction and a diminished systolic strain response under stress in the mTBI group. At the molecular level, cardiac T-p38MAPK and troponin I expression was pathologic modified post-mTBI. We found linear correlations between brain sO2 measured immediately post-mTBI and long-term cardiac strain after 8 months. We report that initial cerebrovascular hypoxia and chronic cardiac dysfunction correlated with long-term behavioral changes hinting at anxiety-like and memory maladaptation. CONCLUSION:Experimental juvenile mTBI induces time-dependent cardiac dysfunction that corresponds to the initial neurovascular sO2 dip and is associated with long-term behavioral modifications. These imaging biomarkers of the heart-brain axis could be applied to improve clinical pediatric mTBI management.

BACKGROUND: Atrial fibrillation (AF)—the most common sustained cardiac arrhythmia—increases thromboembolic stroke risk 5-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function remain unknown. We tested the hypothesis that increased expression of PPP1R12C (protein phosphatase 1 regulatory subunit 12C)—the PP1 (protein phosphatase 1) regulatory subunit targeting MLC2a (atrial myosin light chain 2)—causes hypophosphorylation of MLC2a and results in atrial hypocontractility. METHODS: Right atrial appendage tissues were isolated from human patients with AF versus sinus rhythm controls. Western blots, coimmunoprecipitation, and phosphorylation studies were performed to examine how the PP1c (PP1 catalytic subunit)-PPP1R12C interaction causes MLC2a dephosphorylation. In vitro studies of pharmacological MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) inhibitor (BDP5290) in atrial HL-1 cells were performed to evaluate PP1 holoenzyme activity on MLC2a. Cardiac-specific lentiviral PPP1R12C overexpression was performed in mice to evaluate atrial remodeling with atrial cell shortening assays, echocardiography, and AF inducibility with electrophysiology studies. RESULTS: In human patients with AF, PPP1R12C expression was increased 2-fold versus sinus rhythm controls ( P =2.0×10 −2 ; n=12 and 12 in each group) with >40% reduction in MLC2a phosphorylation ( P =1.4×10 −6 ; n=12 and 12 in each group). PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF ( P =2.9×10 −2 and 6.7×10 −3 , respectively; n=8 and 8 in each group). In vitro studies utilizing drug BDP5290, which inhibits T560-PPP1R12C phosphorylation, demonstrated increased PPP1R12C binding with both PP1c and MLC2a and dephosphorylation of MLC2a. Mice treated with lentiviral PPP1R12C vector demonstrated a 150% increase in left atrial size versus controls ( P =5.0×10 −6 ; n=12, 8, and 12), with reduced atrial strain and atrial ejection fraction. Pacing-induced AF in mice treated with lentiviral PPP1R12C vector was significantly higher than in controls ( P =1.8×10 −2 and 4.1×10 −2 , respectively; n=6, 6, and 5). CONCLUSIONS: Patients with AF exhibit increased levels of PPP1R12C protein compared with controls. PPP1R12C overexpression in mice increases PP1c targeting to MLC2a and causes MLC2a dephosphorylation, which reduces atrial contractility and increases AF inducibility. These findings suggest that PP1 regulation of sarcomere function at MLC2a is a key determinant of atrial contractility in AF.

Epidemiological studies have shown a relationship between hand exertion and risk of developing distal upper extremity musculoskeletal disorders (DUEMSDs). Recently, fatigue-failure models were proposed for estimating the risk of DUEMSD development. However, models that incorporate tendon strain are primarily based on in-vitro data and may be better informed using in-vivo data. This methodological pilot study aimed to establish an approach for correlating grip force and spatiotemporal strains of the flexor digitorum superficialis (FDS) tendon using ultrasound imaging. Three image texture correlation techniques to measure in-vivo strains were explored and compared: digital image correlation, direct deformation estimation, and StrainNet, a novel deep learning neural network for strain prediction. StrainNet resulted in more accurate strain measurements than conventional image assessment tools, enabled continuous prediction of FDS tendon strain, and allowed for comparison of median bulk tissue strain during isometric contraction to grip force. Future work will study more participants and viscoelastic behavior.

Purpose Z-spectrum imaging, defined as the consecutive collection of images after saturating over a range of frequency offsets, has been recently proposed as a method to measure the fat-water fraction by the simultaneous detection of fat and water resonances. By incorporating a binomial pulse irradiated at each offset before the readout, the spectral selectivity of the sequence can be further amplified, making it possible to monitor the subtle proton resonance frequency shift that follows a change in temperature. Methods We tested the hypothesis in aqueous and cream phantoms and in healthy mice, all under thermal challenge. The binomial module consisted of 2 sinc-shaped pulses of opposite phase separated by a delay. Such a delay served to spread out off-resonance spins, with the resulting excitation profile being a periodic function of the delay and the chemical shift. Results During heating experiments, the water resonance shifted downfield, and by fitting the curve to a sine function it was possible to quantify the change in temperature. Results from Z-spectrum imaging correlated linearly with data from conventional MRI techniques like T-1 mapping and phase differences from spoiled GRE. Conclusion Because the measurement is performed solely on magnitude images, the technique is independent of phase artifacts and is therefore applicable in mixed tissues (e.g., fat). We showed that Z-spectrum imaging can deliver reliable temperature change measurement in both muscular and fatty tissues.

Introduction: Atrial fibrillation (AF) is the most common sustained arrhythmia, with an estimated prevalence in the U.S. of 6.1 million . AF increases the risk of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. We have recently identified protein phosphatase 1 subunit 12c (PPP1R12C) as a key molecule targeting myosin light chain phosphorylation in AF. Objective We hypothesize that the overexpression of PPP1R12C causes hypophosphorylation of atrial myosin light chain 2 (MLC2a), thereby decreasing atrial contractility in AF. Methods and Results Left and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluate the role of the PP1c-PPP1R12C interaction in MLC2a de-phosphorylation, we utilized Western blots, co-immunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12CPP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A) PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusion The overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, associated with a reduction in atrial contractility and increase in AF inducibility. All these discoveries suggest that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

Introduction: Progression to heart failure is a known consequence of longstanding hypertrophic cardiomyopathy (HCM); however, routine function markers such as ejection fraction (EF) are often inadequate to predict dysfunction progression. The objective of this abstract was to create a novel metric, the Hybrid Strain Index (HSI), that can provide better characterization of heart failure progression. We hypothesized that longitudinal changes in a mouse model with known cardiac dysfunction could be more accurately differentiated with HSI than EF. Methods: Longitudinal 4D ultrasound (4DUS) data from mice with hypertrophic cardiomyopathy secondary to cardiac deletion of the carnitine palmitoyltransferase 2 enzyme ( Cpt2 M-/- ; n=12) and littermate controls (n=14) were analyzed using a custom MATLAB toolbox that derived both global volumetric (e.g., EF) and regional kinematic (e.g., circumferential and longitudinal strain) measurements. The circumferential and longitudinal regions most sensitive to disease progression were identified as the base (E θθ ) and posterior-wall (E LL ), respectively. The HSI metric was then calculated as the L2 norm of those peak-strain values. Results: To identify the earliest age of deviation between Cpt2 M-/- and controls, 95% confidence intervals from linear regression through HSI values intersected at 5.7 weeks old, compared to 7.1 weeks old using EF, suggesting HSI provides earlier sensitivity to cardiac dysfunction. Additionally, area-under-curve (AUC) measurements from ROC analysis of each metric, regardless of age, showed greater differentiation between cohorts using HSI (AUC = 0.91) than EF (AUC = 0.84). This further suggests enhanced diagnostic value of HSI compared to EF in the setting of cardiac dysfunction. Conclusions: The proposed HSI metric demonstrated greater sensitivity to detecting cardiac dysfunction and disease progression, compared to EF, in a mouse model of hypertrophic cardiomyopathy ( Cpt2 M-/- ).

Objective: Aortic valve (AoV) disease affects up to 5% of Americans over 65 years age. While AoV disease is frequently diagnosed using 3D transesophageal echocardiography, these same methods are not available for small animals, hindering the ability to track disease progression. A recently developed small animal imaging technique, four-dimensional ultrasound (4DUS), has opened the possibility of direct AoV visualization in mice. Methods: Data Acquisition: 4DUS imaging (Vevo 3100; FUJIFILM VisualSonics) was performed on the AoVs of 16 C57BL/6J mice, consisting of ten wild-type (n=5 each, male and female, 3 months old), and three osteogenesis imperfecta mice with three littermate controls (12 months old). Data Analysis: AoV data was loaded into a custom MATLAB toolbox for analysis. Data was oriented orthogonal to the aortic annulus, stabilized against intra-thoracic motion, and boundary-tracked using discrete points along both the AoV wall and the leaflet free edge. Results: This method allows for volumetric visualization of the valve across the cardiac cycle, shown here in open (Figure 1B) and closed (1C) states. Analysis-derived surfaces composing the three AoV leaflets are extracted and provide 3D visualizations of leaflet dynamics, as shown in the open (Figure 1D) and closed (1E) states with calculated displacement from end-diastole overlaid. Peak average displacements of each leaflet in the mouse displayed here were RCC: 0.38mm (yellow star), LCC: 0.35mm, and NCC: 0.31mm. Conclusions: We demonstrate the ability to reliably capture gated, volumetric in vivo data of the murine AoV, which were previously only reported through 1D and 2D measures. The technique detailed here allows for robust assessment of leaflet dynamics in 3D, thus providing a foundation for longitudinal characterization of murine models of aortic valve disease.

Introduction: Cardiomyopathy (CM) is the most common cause of mortality in Duchenne muscular dystrophy (DMD). Because CM progression is variable, there is a critical need for biomarkers to detect early onset or rapid progression. Our objective was to evaluate localized kinematic parameters that correlate with function utilizing spatiotemporal analysis of 4D (3D plus time) cardiac magnetic resonance (CMR). We hypothesized that novel regional strain metrics would correlate with left ventricular ejection fraction (LVEF), providing insight for future DMD CM characterization studies . Methods: Sequential short axis cine CMR images of DMD patients (n=10) with a range of CM severity were compiled into 4D sequences. Epi- and endocardial borders were then segmented across one cardiac cycle for kinematic analysis. We evaluated Green-Lagrange circumferential strain (ε cc ) at 60 equally spaced short axis slices and across 60 time points to generate a spatiotemporal map. We also evaluated a novel “hybrid strain index” combining basal ε cc with posterior free-wall longitudinal strain. Spearman’s rho was used to determine statistical correlation. Results: DMD subjects had a median age of 11 years (8-24); 3 had LVEF<55% and 7 had late gadolinium enhancement. Regional peak averages of ε cc decreased with LVEF for basal ( rho =-0.94, p <.001) and mid-LV ( rho =-0.84, p =.004) but not at the apex ( rho =-0.55, p =.106). The hybrid strain index also decreased with LVEF ( rho =0.89, p <.001). Qualitative spatiotemporal ε cc maps of mild, moderate, and severe DMD cases demonstrate stark differences in regional wall motion (Figure 1). Conclusion: 4D spatiotemporal analysis of CMR images in DMD patients allows for robust comparison of regional kinematic parameters that correlate with LVEF. Figure 1: 4D CMR spatiotemporal analysis of DMD cardiomyopathy. A,B) Schematic of circumferential strain (ε cc ). C,D,E) Example mild, moderate, and severe patient spatiotemporal ε cc maps.

Introduction: While effective for out-of-hospital cardiac arrest, therapeutic hypothermia can be difficult to timely implement clinically. No drugs exist for improving neurologically intact survival. We have developed a novel peptide (TAT-PHLPP) that inhibits PH domain and Leucine rich repeat Protein Phosphatases (PHLPP), leading to Akt activation and mimicking of the protective effects of therapeutic hypothermia without the need of physical cooling. Hypothesis: We hypothesize that when administered intravenously during CPR, TAT-PHLPP improves neurologically intact survival. Methods: We conducted parallel studies in mouse and swine models. In C57BL6 mice (n = 72), we induced a 8 or 12-min asystolic cardiac arrest with KCl, followed by initiation of CPR and blinded randomized administration of TAT-PHLPP (7.5 mg/kg) or saline placebo. The primary outcomes were 4-h and 5-day survival, mean arterial blood pressure (MAP) and cerebral blood flow (CBF). We assessed PHLPP-NHERF1 binding and glucose utilization (via pyruvate dehydrogenase (PDH) phosphorylation and ATP generation). In 16 swine, we induced 5 min of VF followed by ACLS with vest CPR and administered two doses of TAT-PHLPP or saline. Survival (24 h) and neurological function were assessed. Plasma biomarkers taurine and glutamate levels in mice were measured and validated in CA patients (n=68) with a shockable rhythm at the time of hospital arrival, 6, 24, 48, and 72 h post-hospital arrival. Results: In mice, compared to saline, TAT-PHLPP significantly improved 4-h and 5-day survival, increased post-ROSC MAP and CBF, inhibited PHLPP-NHERF1 binding, increased p-Akt, decreased p-PDH (increased activity) at 15 min post-ROSC, enhanced ATP generation in both heart and brain, and reduced plasma taurine and glutamate levels. In swine, TAT-PHLPP improved 24 h neurologically intact survival (1/9 in control vs. 6/7 with peptide, p < 0.01). In patients, taurine levels were higher in non-survivors (n=44) than survivors (n=24) at 6 h of post-hospital arrival (65.9 ± 34.8 vs. 45.6 ±23.7, p< 0.001). Conclusions: TAT-PHLPP has high translational potential as a first-of-class biologic treatment to reproduce critical outcomes of therapeutic hypothermia and improve cardiac arrest survival.

The main objective of the study was to determine if rodent housing conditions, specifically housing climate, could impact the in vivo performance of poly(lactide-co-glycolide) (PLGA) microspheres through temperature modification of the subcutaneous space. Vivitrol (R), a once monthly naltrexone injectable suspension, was chosen as a model PLGA microparticle formulation for this study. Two lots of Vivitrol were used to ascertain any potential differences that may exist between the batches and if in vitro characterization techniques could delineate any variation(s). The pharmacokinetics of the naltrexone-PLGA microparticles were determined in the rodent model under two different housing climates (20 vs. 25 degrees C). The results demonstrate that such difference in housing temperature resulted in a change in subcutaneous temperature but actually within a narrow range (36.31-36.77 degrees C) and thus minimally influenced the in vivo performance of subcutaneously injected microparticles. The shake-flask method was used to characterize the in vitro release at 35, 36, and 37 degrees C and demonstrated significant differences in the in vitro release profiles across this range of temperatures. Minimal differences in the in vitro characterization of the two lots were found. While these results did not provide statistical significance, the local in vivo temperature may be a parameter that should be considered when evaluating microparticle performance. The IVIVCs demonstrate that in vitro release at 37 degrees C may not accurately represent the in vivo conditions (i.e., subcutaneous space in rodents), and in certain instances lower in vitro release temperatures may more accurately represent the in vivo microenvironment and provide better correlations. Future studies will determine the extent temperature and specifically co-housing, may have on the relative impact of the in vivo performance of injectable polymeric microparticles based upon the significant differences observed in the in vitro release profiles across the range of 35-37 degrees C.

Mouse models of cardiac disease have become essential tools in the study of pathological mechanisms, but the small size of rodents makes it challenging to quantify heart function with noninvasive imaging. Building off recent developments in high-frequency four-dimensional ultrasound (4DUS) imaging, we have applied this technology to study cardiac dysfunction progression in a murine model of metabolic cardiomyopathy. Cardiac knockout of carnitine palmitoyltransferase 2 (Cpt2(M)(-/-)) in mice hinders cardiomyocyte bioenergetic metabolism of long-chain fatty acids, and leads to progressive cardiac hypertrophy and heart failure. The proposed analysis provides a standardized approach to measure localized wall kinematics and simultaneously extracts metrics of global cardiac function, LV morphometry, regional circumferential strain, and regional longitudinal strain from an interpolated 4-D mesh of the endo- and epicardial boundaries. Comparison of metric changes due to aging suggests that circumferential strain at the base and longitudinal strain along the posterior wall are most sensitive to disease progression. We further introduce a novel hybrid strain index (HSI) that incorporates information from these two regions and may have greater utility to characterize disease progression relative to other extracted metrics. Potential applications to additional disease models are discussed that could further demonstrate the utility of metrics derived from 4DUS imaging and strain mapping. NEW & NOTEWORTHY High-frequency four-dimensional ultrasound can be used in conjunction with standardized analysis procedures to simultaneously extract left-ventricular global function, morphometry, and regional strain metrics. Furthermore, a novel hybrid strain index (HSI) formula demonstrates greater performance compared with all other metrics in characterizing disease progression in a model of metabolic cardiomyopathy.