Biology subjects

Vang, L.

Publications and source records attributed to Vang, L..

5 recordsLinked to original sources

bioRxiv2022

Cardiovascular Hemodynamics in Mice with Tumor Necrosis Factor Receptor - Associated Factor 2 Mediated Cytoprotection in the Heart

Many studies in mice have demonstrated that cardiac-specific innate immune signaling pathways can be reprogrammed to modulate inflammation in response to myocardial injury and improve outcomes. While the echocardiography standard parameters of left ventricular (LV) ejection fraction, fractional shortening, and end-diastolic diameter, and others, are used to assess cardiac function, their dependency on loading conditions somewhat limit their utility in completely reflecting the contractile function and global cardiovascular efficiency of the heart. A true measure of global cardiovascular efficiency should include of the interaction between the ventricle and the aorta (ventriculo-vascular coupling, VVC) as well as measures of aortic impedance and pulse wave velocity. We measured cardiac Doppler velocities, blood pressures, along with VVC, aortic impedance, and pulse wave velocity to evaluate global cardiac function in mouse model of cardiac-restricted low levels TRAF2 overexpression that conferred cytoprotection in the heart. While previous studies reported that response to myocardial infraction and reperfusion was improved in the TRAF2 overexpressed mice, we found that TRAF2 mice had significantly lower cardiac systolic velocities and accelerations, diastolic atrial velocity, lower aortic pressures and rate-pressure product, lower LV contractility and relaxation, and lower stroke work when compared to littermate control mice. Also, we found significantly longer aortic ejection time, isovolumic contraction and relaxation times, and significantly higher mitral early/atrial ratio, myocardial performance index, and ventricular vascular coupling in the TRAF2 overexpression mice compared to their littermate controls. We found no significant differences in the aortic impedance and pulse wave velocity. While the reported tolerance to ischemic insults in TRAF2 overexpression mice may suggest enhanced cardiac reserve, our results indicate a diminished cardiac function in these mice.

biophysics↗

bioRxiv2022

MICOS Complex and Mitochondria Morphology Changes Across Aging in Cardiac Muscle

ABSTRACTWith sparse treatment options, cardiac disease remains a significant cause of death among humans. As a person ages, mitochondria break down and the heart becomes less efficient. Heart failure is linked to many mitochondria-associated processes, including endoplasmic reticulum stress, mitochondrial bioenergetics, insulin signaling, autophagy, and oxidative stress. The roles of key mitochondrial complexes that dictate the ultrastructure, such as the mitochondrial contact site and cristae organizing system (MICOS), in aging cardiac muscle are poorly understood. To better understand the cause of age-related alteration in mitochondrial structure in cardiac muscle, we used transmission electron microscopy (TEM) and serial block facing-scanning electron microscopy (SBF-SEM) to quantitatively analyze the 3D networks in cardiac muscle samples of male mice at aging intervals of 3 months, 1 year, and 2 years. Here, we present the loss of cristae morphology, the inner folds of the mitochondria, across age. In conjunction with this, the 3D volume of mitochondria decreased. These findings mimicked observed phenotypes in murine cardiac fibroblasts with CRISPR/Cas9 knockout of Mitofilin, Chchd3, Chchd6 (some members of the MICOS complex), and Opa1, which showed poorer oxidative consumption rate and mitochondria with decreased mitochondrial length and volume. In combination, these data show the need to explore if loss of the MICOS complex in the heart may be involved in age-associated mitochondrial and cristae structural changes.

biophysics↗

bioRxiv2022

3D Reconstructions of Mouse Skeletal Muscle and Heart Muscle Reveal a Decrease in the MICOS Complex and Altered Mitochondrial Networks

BackgroundDuring aging, muscle gradually undergoes loss of function including sarcopenia, losing mass, strength, endurance, and oxidative capacity. While mitochondrial aging is associated with decreased mitochondrial capacity, the genes associated with morphological changes in mitochondria during aging still require further elucidation. Furthermore, it is not completely understood how 3D mitochondrial structures are altered during aging in skeletal muscle and cardiac tissues. MethodsWe measured changes in mitochondrial morphology and mitochondrial complexity during the aging of murine gastrocnemius, soleus, and cardiac tissues using serial block face- scanning electron microscopy and 3D reconstruction. Lipidomic and metabolomic analysis elucidated concomitant changes associated with aging. We also used qPCR, transmission electron microscopy quantification, Seahorse Analyzer, and metabolomics to evaluate changes in mitochondria morphology and function upon loss of the MICOS complex. ResultsWe identified significant changes in 3D mitochondrial size and network configuration in murine gastrocnemius, soleus, and cardiac tissue during aging. These changes were concomitant with loss of mitochondria contact site and cristae organizing system (MICOS) gene expression during aging. Mitochondrial morphology was similar between aged mice and young mice. We show an age-related loss of the MICOS complex (Chchd3, chchd6, and Mitofilin) while their knockout results in alterations in mitochondrial morphology. Given the critical role of mitochondria in maintaining cellular metabolism, we perform cellular metabolic profiling of young and aged tissues. Metabolomics and lipidomics showed profound alterations, including in membrane integrity, that support our observations of age-related changes in these muscle tissues. DiscussionIn tandem, our data suggest a relationship between the MICOS complex and aging, which could be linked to disease states with further 3D reconstruction studies. Our study highlights the importance of understanding tissue-dependent 3D mitochondrial phenotypical changes which occur across aging with evolutionary conservation between Drosophila and murine models. Graphical Abstract

biophysics↗

bioRxiv2021

Practices for Measuring 3D Organelle Morphology and Generating Surfaces with Amira

Analysis of 3D structures is of paramount importance in cellular biology. Although light microscopy and transmission electron microscopy (TEM) have remained staples for imaging cellular structures, they lack the ability to image in 3D. However, recent technological advances, such as serial block-face scanning electron microscopy (SBF-SEM) and focused ion beam scanning electron microscopy (FIB-SEM), have allowed researchers to observe cellular ultrastructure in 3D. Here, we propose a standardized protocol using the visualization software Amira to quantify organelle morphologies in 3D; this method allows researchers to produce accurate and reproducible measurements of cellular structure characteristics. We demonstrate this applicability by utilizing SBF-SEM and Amira to quantify mitochondria and endoplasmic reticulum (ER) structures. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/461807v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@1c40041org.highwire.dtl.DTLVardef@ecde92org.highwire.dtl.DTLVardef@10870daorg.highwire.dtl.DTLVardef@1290c3b_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2021

Systematic Transmission Electron Microscopy-Based Identification of Cellular Degradation Machinery

Many interconnected degradation machineries including autophagosomes, lysosomes, and endosomes work in tandem to conduct autophagy, an intracellular degradation system that is crucial for cellular homeostasis. Altered autophagy contributes to the pathophysiology of various diseases, including cancers and metabolic diseases. Although many studies have investigated autophagy to elucidate disease pathogenesis, identification of specific components of the autophagy machinery has been challenging. The goal of this paper is to describe an approach to reproducibly identify and distinguish subcellular structures involved in macro autophagy. We provide methods that help avoid common pitfalls, including a detailed explanation for distinguishing lysosomes and lipid droplets and discuss differences between autophagosomes and inclusion bodies. These methods are based on using transmission electron microscopy (TEM), capable of generating nanometer-scale micrographs of cellular degradation components in a fixed sample. We also utilize serial block face-scanning electron microscopy (SBF-SEM) to offer a protocol for visualizing 3D morphology of degradation machinery. In addition to TEM and 3D reconstruction, we discuss other imaging techniques, such as immunofluorescence and immunogold labeling that can be utilized to reliably and accurately classify cellular organelles. Our results show how these methods may be used to accurately quantify the cellular degradation machinery under various conditions, such as treatment with the endoplasmic reticulum stressor thapsigargin or ablation of the dynamin-related protein 1.

biophysics↗