SUMOylation of NaV1.2 channels regulates the velocity of backpropagating action potentials in cortical pyramidal neurons.

Voltage-gated sodium channels located in axon initial segments (AIS) trigger action potentials (AP) and play pivotal roles in the excitability of cortical pyramidal neurons. The differential electrophysiological properties and distributions of NaV1.2 and NaV1.6 channels lead to distinct contributions to AP initiation and propagation. While NaV1.6 at the distal AIS promotes AP initiation and forward propagation, NaV1.2 at the proximal AIS promotes the backpropagation of APs to the soma. Here, we show the small ubiquitin-like modifier (SUMO) pathway modulates Na+ channels at the AIS to increase neuronal gain and the speed of backpropagation. Since SUMO does not affect NaV1.6, these effects were attributed to SUMOylation of NaV1.2. Moreover, SUMO effects were absent in a mouse engineered to express NaV1.2-Lys38Gln channels that lack the site for SUMO linkage. Thus, SUMOylation of NaV1.2 exclusively controls INaP generation and AP backpropagation, thereby playing a prominent role in synaptic integration and plasticity.

Evaluation of global gene expression in regenerate tissues during Masquelet treatment.

The Masquelet induced-membrane (IM) technique is indicated for large segmental bone defects. Attributes of the IM and local milieu that contribute to graft-to-bone union are unknown. Using a rat model, we compared global gene expression profiles in critically sized femoral osteotomies managed using a cement spacer as per Masquelet to those left empty. At the end of the experiment, IM and bone adjacent to the spacer were collected from the Masquelet side. Nonunion tissue in the defect and bone next to the empty defect were collected from the contralateral side. Tissues were subjected to RNA isolation, sequencing, and differential expression analysis. Cell type enrichment analysis suggested the IM and the bone next to the polymethylmethacrylate (PMMA) spacer were comparatively enriched for osteoblastic genes. The nonunion environment was comparatively enriched for innate and adaptive immune cell markers, but only macrophages were evident in the Masquelet context. iPathwayGuide was utilized to identify cell signaling pathways and protein interaction networks enriched in the Masquelet environment. For IM vs nonunion false-discovery rate correction of P values rendered overall pathway differences nonsignificant, and so only protein interaction networks are presented. For the bone comparison, substantial enrichment of pathways and networks known to contribute to osteogenic mechanisms was revealed. Our results suggest that the PMMA spacer affects the cut bone ends that are in contact with it and at the same time induces the foreign body reaction and formation of the IM. B cells in the empty defect suggest a chronic inflammatory response to a large segmental osteotomy.

Impact of Baseline Left Ventricular Diastolic Dysfunction in Patients With Severe Aortic Stenosis Undergoing Transcatheter Aortic Valve Implantation.

We sought to assess the impact of diastolic dysfunction (DD) grade, as per the 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging guidelines, on survival of patients with severe aortic stenosis (AS) who underwent transcatheter aortic valve implantation (TAVI). We included consecutive patients with severe AS who underwent TAVI in our institution. DD grading was determined retrospectively according to the 2016 ASE DD guidelines and categorized to grade I-III and indeterminate grade I-II DD. Comparison of 1-year survival according to DD grade was performed by Kaplan-Meier analysis, and evaluation of DD at 1 year was performed in a subset of patients. Among 606 TAVI patients, 394 (65%) had sufficient data for DD grading. Seventy-seven (20%) had grade I DD, 191 (48%) had grade II, 60 (15%) had grade III, and 66 (17%) had an indeterminate grade between I and II. Baseline characteristics indicate higher rates of atrial fibrillation, brain natriuretic peptide level, pulmonary artery systolic pressure, and indexed left ventricular mass as DD grade increases (all p ≤0.01). In conclusion, comparison of 1-year survival revealed a higher rate of mortality in patients with grade III DD that remained statistically significant following adjustment in a multivariate Cox proportional hazard model. DD grade after TAVI improved in patients with grades II and III. Severe AS patients with grade III DD have higher risk for 1-year mortality after TAVI compared with milder degrees of DD. Further research is warranted to explore a potential benefit for aortic valve therapy at an earlier stage of the disease process.

Usefulness of Longitudinal Strain to Assess Remodeling of Right and Left Cardiac Chambers Following Transcatheter Aortic Valve Implantation.

Remodeling after transcatheter aortic valve implantation (TAVI) has been well characterized for the left ventricle (LV) but not for the other cardiac chambers. We aimed to describe conventional indices of cardiac remodeling and novel longitudinal strain (LS) in all 4 cardiac chambers post-TAVI and to explore gender remodeling disparities. Consecutive patients with significant aortic stenosis who underwent TAVI were included if echocardiograms in sinus rhythm before and 1-year postprocedure were available. Speckle tracking analysis was performed retrospectively to evaluate size and function of the 4 cardiac chambers. Baseline and 1-year data were compared. From a total of 612 patients who underwent TAVI, 213 were included in this study (82 ± 9 years old, 42% men). Although no significant size or function changes were seen for right cardiac chambers at follow-up, significant improvements were seen for ejection fraction (EF) and LS in both the LV and left atrium (LA) (p < 0.05 for both). The absolute percentage of LV and LA function improvement was higher for LS than for EF (p < 0.05). Women had smaller LV and right ventricular (RV) size, whereas parameters of LV and RV function were higher. All 1-year remodeling parameters were similar for men and women. Conventional LV remodeling parameters (LV mass) failed to improve 1 year after TAVI. However, novel strain-derived parameters of size and function showed remodeling of left chambers but not of RV or right atrium. The degree of LV and LA remodeling by LS is almost twice that of EF. Remodeling was similar for both genders.

Interobserver Variability in Applying American Society of Echocardiography/European Association of Cardiovascular Imaging 2016 Guidelines for Estimation of Left Ventricular Filling Pressure.

BACKGROUND: Assessment of left ventricular (LV) filling pressure is among the important components of a comprehensive echocardiographic report. Previous studies noted wide limits of agreement using 2009 American Society of Echocardiography/European Association of Echocardiography guidelines, but reproducibility of 2016 guidelines update in estimating LV filling pressure is unknown. METHODS: Echocardiographic and hemodynamic data were obtained from 50 patients undergoing cardiac catheterization for clinical indications. Clinical and echocardiographic findings but not invasive hemodynamics were provided to 4 groups of observers, including experienced echocardiographers and cardiology fellows. Invasively acquired LV filling pressure was the gold standard. RESULTS: In group I of 8 experienced echocardiographers from the guidelines writing committee, sensitivity for elevated LV filling pressure was 92% for all observers, and specificity was 93±6%. Fleiss κ-value for the agreement in group I was 0.80. In group II of 4 fellows in training, sensitivity was 91±2%, and specificity was 95±2%. Fleiss κ-value for the agreement in group II was 0.94. In group III of 9 experienced echocardiographers who had not participated in drafting the guidelines, sensitivity was 88±5%, and specificity was 91±7%. Fleiss κ-value for the agreement in group III was 0.76. In group IV of 7 other fellows, sensitivity was 91±3%, and specificity was 92±5%. Fleiss κ-value for the agreement in group IV was 0.89. CONCLUSIONS: There is a good level of agreement and accuracy in the estimation of LV filling pressure using the American Society of Echocardiography/European Association of Cardiovascular Imaging 2016 recommendations update, irrespective of the experience level of the observer.

Impact of right ventricular function on outcome of severe aortic stenosis patients undergoing transcatheter aortic valve replacement.

BACKGROUND: Right ventricular (RV) dysfunction was shown to be associated with adverse outcomes in a variety of cardiac patients and is considered a risk factor for adverse outcome according to the updated Valve Academic Research Consortium criteria. OBJECTIVE: Our goal was to assess the impact of RV function at baseline on 1-year mortality among patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR). METHODS: All patients with severe AS treated with TAVR from May 2007 to March 2015 at our center were included in the present study, and baseline and procedural characteristics were recorded for each patient. The patients were categorized according to RV function at baseline as assessed by current guidelines, and a comparison of mortality rates up to 1 year was performed. RESULTS: Among 650 patients, 606 had adequate echocardiogram quality and 146 (24%) had RV dysfunction. There were significant differences between the 2 groups, as patients with RV dysfunction were younger (81±9 vs 84±7 years, P=.01) and were more likely to be male (65% vs 42%, P<.001). In addition, patients with RV dysfunction had higher rates of prior myocardial infarction (26% vs 16%, P=.02) and atrial fibrillation (51% vs 39%, P=.02). Echocardiographic parameters demonstrated higher rates of left ventricular ejection fraction <40% (40% vs 18%, P<.001), tricuspid regurgitation above moderate (16% vs 9%, P=.04), and higher pulmonary artery systolic pressure (50±17 vs 44±16 mm Hg, P<.001) among patients with severe AS and RV dysfunction compared with patients with normal RV function. Despite the unfavorable cardiac function, patients with severe AS undergoing TAVR have similar functional class (P=.22) and mortality rates at 1year (27% vs 23%, log-rank P=.45). CONCLUSIONS: Patients with severe AS and RV dysfunction have similar 1-year mortality and functional class after TAVR to patients with normal RV function. The presence of RV dysfunction does not correlate with outcome in patients with severe AS.

Synergistic enhancement of ectopic bone formation by supplementation of freshly isolated marrow cells with purified MSC in collagen-chitosan hydrogel microbeads.

PURPOSE: Bone marrow-derived mesenchymal stem cells (MSC) can differentiate osteogenic lineages, but their tissue regeneration ability is inconsistent. The bone marrow mononuclear cell (BMMC) fraction of adult bone marrow contains a variety of progenitor cells that may potentiate tissue regeneration. This study examined the utility of BMMC, both alone and in combination with purified MSC, as a cell source for bone regeneration. METHODS: Fresh BMMC, culture-expanded MSC, and a combination of BMMC and MSC were encapsulated in collagen-chitosan hydrogel microbeads for pre-culture and minimally invasive delivery. Microbeads were cultured in growth medium for 3 days, and then in either growth or osteogenic medium for 17 days prior to subcutaneous injection in the rat dorsum. RESULTS: MSC remained viable in microbeads over 17 days in pre-culture, while some of the BMMC fraction were nonviable. After 5 weeks of implantation, microCT and histology showed that supplementation of BMMC with MSC produced a strong synergistic effect on the volume of ectopic bone formation, compared to either cell source alone. Microbeads containing only fresh BMMC or only cultured MSC maintained in osteogenic medium resulted in more bone formation than their counterparts cultured in growth medium. Histological staining showed evidence of residual microbead matrix in undifferentiated samples and indications of more advanced tissue remodeling in differentiated samples. CONCLUSIONS: These data suggest that components of the BMMC fraction can act synergistically with predifferentiated MSC to potentiate ectopic bone formation. The microbead system may have utility in delivering desired cell populations in bone regeneration applications.

A Summary of the American Society of Echocardiography Foundation Value-Based Healthcare: Summit 2014: The Role of Cardiovascular Ultrasound in the New Paradigm.

Value-Based Healthcare: Summit 2014 clearly achieved the three goals set forth at the beginning of this document. First, the live event informed and educated attendees through a discussion of the evolving value-based healthcare environment, including a collaborative effort to define the important role of cardiovascular ultrasound in that environment. Second, publication of these Summit proceedings in the Journal of the American Society of Echocardiography will inform a wider audience of the important insights gathered. Third, moving forward, the ASE will continue to build a ''living resource'' on its website, http://www.asecho.org, for clinicians, researchers, and administrators to use in advocating for the value of cardiovascular ultrasound in the new value-based healthcare environment. The ASE looks forward to incorporating many of the Summit recommendations as it works with its members, legislators, payers, hospital administrators, and researchers to demonstrate and increase the value of cardiovascular ultrasound. All Summit attendees shared in the infectious enthusiasm generated by this proactive approach to ensuring cardiovascular ultrasound's place as ''The Value Choice'' in cardiac imaging.

Prevalence and impact of pulmonary hypertension on patients with aortic stenosis who underwent transcatheter aortic valve replacement.

Limited amount of data suggest that patients with aortic stenosis and pulmonary hypertension (PH) who undergo transcatheter aortic valve replacement (TAVR) experience decrease in PH postprocedure. Inconsistent use of systolic pulmonary artery pressure cut-off values in previous studies limits our ability to draw meaningful conclusions regarding the prognostic role of PH in assessment of TAVR candidates. A total of 415 consecutive patients who underwent TAVR were included in the present study. Two groups were compared based on receiver-operating characteristics curve analysis for the best SPAP value to predict outcome, yielding 2 study groups of no/mild PH (≤50 mm Hg; n = 172, 41%) versus moderate/severe PH (>50 mm Hg; n = 243, 59%). Demographics and co-morbidities were comparable between the 2 groups; however, right-sided cardiac failure (35% vs 19.8%, p = 0.02) and mitral regurgitation (18.4% vs 8.6%, p = 0.007) were more frequent in patients with moderate/severe PH. Procedural characteristics and complications were comparable between the groups. Although there was an early overall decrease in SPAP postprocedure, only 26% of moderate/severe patients with PH experienced a significant decrease in SPAP (>10 mm Hg). The 30-day (14.5% vs 7.4%, p = 0.02) and 1-year mortality (30.8% vs 21%, p = 0.02) was higher in moderate/severe patients with PH. In multivariate analysis, systolic pulmonary artery pressure and chronic lung disease were identified as independent predictors for mortality at 1 year. PH is a frequent co-morbidity in patients with severe aortic stenosis who underwent TAVR. Significantly elevated pulmonary artery pressures at baseline may serve as a poor prognostic factor when performing preprocedural assessment of the patients.

Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.

The rapid technological developments of the past decade and the changes in echocardiographic practice brought about by these developments have resulted in the need for updated recommendations to the previously published guidelines for cardiac chamber quantification, which was the goal of the joint writing group assembled by the American Society of Echocardiography and the European Association of Cardiovascular Imaging. This document provides updated normal values for all four cardiac chambers, including three-dimensional echocardiography and myocardial deformation, when possible, on the basis of considerably larger numbers of normal subjects, compiled from multiple databases. In addition, this document attempts to eliminate several minor discrepancies that existed between previously published guidelines.

Prevalence and predictors of left atrial thrombus in patients with atrial fibrillation: is transesophageal echocardiography necessary before cardioversion?

BACKGROUND: Systemic embolization threatens patients with atrial fibrillation (AF). The risk is enhanced at the time of cardioversion. Transesophageal echocardiography (TEE) prior to cardioversion to screen for left atrial thrombus (LAT), a marker of high risk for embolization, is recommended for many patients with AF. OBJECTIVE: To determine clinical and echocardiographic factors associated with LAT formation in AF. METHODS: Data from 600 consecutive patients with AF undergoing TEE prior to cardioversion for the detection of LAT were analyzed. Clinical, laboratory, and echocardiographic parameters were abstracted from the clinical record. RESULTS: TEE identified LAT in 70 (11.6%) and dense (LA) spontaneous echo contrast (SEC) in 156 (26%). Baseline characteristics and echocardiographic parameters of patients with or without LAT are compared. A prior myocardial infarction, 21 (29.4 %) vs. 31 (5.8), (p < 0.001); hypertension, 60 (85.7%) vs. 386 (72.8), (p 0.02); CHADS(2) ≥ 2, 56 (80%) vs. 308 (58.1%), (p < 0.001) prevalence was higher in patients with LAT. Patients with LAT had lower ejection fraction 38.2 ± 15.6 vs. 46.2 ± 14.5, (p < 0.001); higher LA diameter 4.98 ± 0.7 vs. 4.52 ± 0.7, (p <0.001); dense LA SEC 44 (62.8) vs. 112 (21.1), (p < 0.001); and low LA appendage emptying velocity 21.7 ± 12.9 vs. 37.5 ± 19.4, (p < 0.001). Multivariate analysis was done, and it revealed that low LA emptying velocity had the strongest independent association with LAT (HR 0.89 [CI 0.83-0.96], p value <0.001. CONCLUSION: LAT is not an uncommon finding of AF patients prior to cardioversion. The current practice of TEE examination may be justified since neither clinical nor routine 2D echo examinations reliably identify LAT.

Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.

The rapid technological developments of the past decade and the changes in echocardiographic practice brought about by these developments have resulted in the need for updated recommendations to the previously published guidelines for cardiac chamber quantification, which was the goal of the joint writing group assembled by the American Society of Echocardiography and the European Association of Cardiovascular Imaging. This document provides updated normal values for all four cardiac chambers, including three-dimensional echocardiography and myocardial deformation, when possible, on the basis of considerably larger numbers of normal subjects, compiled from multiple databases. In addition, this document attempts to eliminate several minor discrepancies that existed between previously published guidelines.

Coronary blood flow in patients with severe aortic stenosis before and after transcatheter aortic valve implantation.

Patients with severe aortic stenosis and no obstructed coronary arteries are reported to have reduced coronary flow. Doppler evaluation of proximal coronary flow is feasible using transesophageal echocardiography. The present study aimed to assess the change in coronary flow in patients with severe aortic stenosis undergoing transcatheter aortic valve implantation (TAVI). The left main coronary artery was visualized using transesophageal echocardiography in 90 patients undergoing TAVI using the Edwards SAPIEN valve. The peak systolic and diastolic velocities of the coronary flow and the time-velocity integral were obtained before and after TAVI using pulse-wave Doppler. Mean aortic gradients decreased from 47.1 ± 15.7 mm Hg before TAVI to 3.6 ± 2.6 mm Hg after TAVI (p <0.001). The aortic valve area increased from 0.58 ± 0.17 to 1.99 ± 0.35 cm(2) (p <0.001). The cardiac output increased from 3.4 ± 1.1 to 3.8 ± 1.0 L/min (p <0.001). Left ventricular end-diastolic pressure (LVEDP) decreased from 19.8 ± 5.4 to 17.3 ± 4.1 mm Hg (p <0.001). The following coronary flow parameters increased significantly after TAVI: peak systolic velocity 24.2 ± 9.3 to 30.5 ± 14.9 cm/s (p <0.001), peak diastolic velocity 49.8 ± 16.9 to 53.7 ± 22.3 cm/s (p = 0.04), total velocity-time integral 26.7 ± 10.5 to 29.7 ± 14.1 cm (p = 0.002), and systolic velocity-time integral 6.1 ± 3.7 to 7.7 ± 5.0 cm (p = 0.001). Diastolic time-velocity integral increased from 20.6 ± 8.7 to 22.0 ± 10.1 cm (p = 0.04). Total velocity-time integral increased >10% in 43 patients (47.2%). Pearson's correlation coefficient revealed the change in LVEDP as the best correlate of change in coronary flow (R = -0.41, p = 0.003). In conclusion, TAVI resulted in a significant increase in coronary flow. The change in coronary flow was associated mostly with a decrease in LVEDP.

Megakaryocytes are mechanically responsive and influence osteoblast proliferation and differentiation.

Maintenance of bone mass and geometry is influenced by mechanical stimuli. Paradigms suggest that osteocytes embedded within the mineralized matrix and osteoblasts on the bone surfaces are the primary responders to physical forces. However, other cells within the bone marrow cavity, such as megakaryocytes (MKs), are also subject to mechanical forces. Recent studies have highlighted the potent effects of MKs on osteoblast proliferation as well as bone formation in vivo. We hypothesize that MKs are capable of responding to physical forces and that the interactions between these cells and osteoblasts can be influenced by mechanical stimulation. In this study, we demonstrate that two MK cell lines respond to fluid shear stress in culture. Furthermore, using laser capture microdissection, we isolated MKs from histologic sections of murine tibiae that were exposed to compressive loads in vivo. C-fos, a transcription factor shown to be upregulated in response to load in various tissue types, was increased in MKs from loaded relative to non-loaded limbs at a level comparable to that of osteocytes from the same limbs. We also developed a co-culture system to address whether mechanical stimulation of MKs in culture would impact osteoblast proliferation and differentiation. The presence of MKs in co-culture, but not conditioned media, had dramatic effects on proliferation of preosteoblast MC3T3-E1 cells in culture. Our data suggests a minimal decrease in proliferation as well as an increase in mineralization capacity of osteoblasts co-cultured with MKs exposed to shear compared to co-cultures with unstimulated MKs.

Biomechanics and mechanobiology in functional tissue engineering.

The field of tissue engineering continues to expand and mature, and several products are now in clinical use, with numerous other preclinical and clinical studies underway. However, specific challenges still remain in the repair or regeneration of tissues that serve a predominantly biomechanical function. Furthermore, it is now clear that mechanobiological interactions between cells and scaffolds can critically influence cell behavior, even in tissues and organs that do not serve an overt biomechanical role. Over the past decade, the field of "functional tissue engineering" has grown as a subfield of tissue engineering to address the challenges and questions on the role of biomechanics and mechanobiology in tissue engineering. Originally posed as a set of principles and guidelines for engineering of load-bearing tissues, functional tissue engineering has grown to encompass several related areas that have proven to have important implications for tissue repair and regeneration. These topics include measurement and modeling of the in vivo biomechanical environment; quantitative analysis of the mechanical properties of native tissues, scaffolds, and repair tissues; development of rationale criteria for the design and assessment of engineered tissues; investigation of the effects biomechanical factors on native and repair tissues, in vivo and in vitro; and development and application of computational models of tissue growth and remodeling. Here we further expand this paradigm and provide examples of the numerous advances in the field over the past decade. Consideration of these principles in the design process will hopefully improve the safety, efficacy, and overall success of engineered tissue replacements.