310 results found
Khokhlova A, Solovyova O, Kohl P, et al., 2022, Single cardiomyocytes from papillary muscles show lower preload-dependent activation of force compared to cardiomyocytes from the left ventricular free wall., J Mol Cell Cardiol, Vol: 166, Pages: 127-136
Efficient pumping of the healthy left ventricle (LV) requires heterogeneities in mechanical function of individual cardiomyocytes (CM). Deformation of sub-endocardial (Endo) tissue is greater than that of sub-epicardial (Epi) regions. Papillary muscles (PM), often considered to be part of Endo tissue, show lower beat-by-beat length variation than Epi (or Endo) regions, even though they contribute to the shift in atrio-ventricular valve plane, which is essential for LV pump function. Thus far, no comparative assessment of CM mechanics for PM and LV free wall has been published. Here, we investigate contractility and cytosolic calcium concentration ([Ca2+]c) transients in rabbit single CM, freshly isolated from PM, Endo and Epi regions of the LV (free wall tissue was further subdivided into near-basal [Base], equatorial [Centre], and near-apical [Apex] parts). Functional parameters were measured in the absence of external mechanical loads (non-loaded), or during afterloaded (auxotonic) CM contractions, initiated from different levels of preload (diastolic axial stretch), using the carbon fibre technique. We note significant differences in time-course and amplitudes of sarcomere shortening between PM, Endo and Epi CM. In non-loaded CM, sarcomere shortening between regions compares as follows: Endo > Epi and Endo > PM. During afterloaded contractions, the slope of auxotonic tension-length relation and the Frank-Starling gain index (preload-dependent increase in tension and shortening) follow the sequence of Endo > Epi > PM. In terms of apico-basal gradients, time-to-peak sarcomere shortening was greater in Apex compared to Centre and Base in non-loaded CM only. Thus, CM from PM show the least pronounced preload-dependent activation of force across the LV regions assessed, while CM from Endo regions show the strongest response. This is in keeping with prior in situ observations on the smaller extent of PM shortening and their thus lower functional r
Emig R, Hoess P, Cai H, et al., 2022, Benchmarking of Cph1 Mutants and DrBphP for Light-Responsive Phytochrome-Based Hydrogels with Reversibly Adjustable Mechanical Properties., Adv Biol (Weinh)
In the rapidly expanding field of molecular optogenetics, the performance of the engineered systems relies on the switching properties of the underlying genetically encoded photoreceptors. In this study, the bacterial phytochromes Cph1 and DrBphP are engineered, recombinantly produced in Escherichia coli, and characterized regarding their switching properties in order to synthesize biohybrid hydrogels with increased light-responsive stiffness modulations. The R472A mutant of the cyanobacterial phytochrome 1 (Cph1) is identified to confer the phytochrome-based hydrogels with an increased dynamic range for the storage modulus but a different light-response for the loss modulus compared to the original Cph1-based hydrogel. Stiffness measurements of human atrial fibroblasts grown on these hydrogels suggest that differences in the loss modulus at comparable changes in the storage modulus affect cell stiffness and thus underline the importance of matrix viscoelasticity on cellular mechanotransduction. The hydrogels presented here are of interest for analyzing how mammalian cells respond to dynamic viscoelastic cues. Moreover, the Cph1-R472A mutant, as well as the benchmarking of the other phytochrome variants, are expected to foster the development and performance of future optogenetic systems.
Kohl P, Greiner J, Rog-Zielinska EA, 2022, Electron microscopy of cardiac 3D nanodynamics: form, function, future, NATURE REVIEWS CARDIOLOGY, ISSN: 1759-5002
Duerschmied D, Hilgendorf I, Kohl P, et al., 2022, SFB1425-The heterocellular nature of cardiac lesions: Identities, interactions, implications, KARDIOLOGE, Vol: 16, Pages: 128-135, ISSN: 1864-9718
Kohl P, 2022, Ask not what The Journal can do for you, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 600, Pages: 1537-1538, ISSN: 0022-3751
Rog-Zielinska EA, Kohl P, 2022, Cardiomyocyte t-tubular fluid pumping, Publisher: CELL PRESS, Pages: 155A-155A, ISSN: 0006-3495
Simon-Chica A, Fernandez MC, Wuelfers EM, et al., 2022, Novel insights into the electrophysiology of murine cardiac macrophages: relevance of voltage-gated potassium channels, Cardiovascular Research, Vol: 118, Pages: 798-813, ISSN: 0008-6363
AimsMacrophages (MΦ), known for immunological roles, such as phagocytosis and antigen presentation, have been found to electrotonically couple to cardiomyocytes (CM) of the atrioventricular node via Cx43, affecting cardiac conduction in isolated mouse hearts. Here, we characterize passive and active electrophysiological properties of murine cardiac resident MΦ, and model their potential electrophysiological relevance for CM.Methods and resultsWe combined classic electrophysiological approaches with 3D florescence imaging, RNA-sequencing, pharmacological interventions, and computer simulations. We used Cx3creYFP/+1 mice wherein cardiac MΦ are fluorescently labelled. FACS-purified fluorescent MΦ from mouse hearts were studied by whole-cell patch-clamp. MΦ electrophysiological properties include: membrane resistance 2.2±0.1 GΩ (all data mean±SEM), capacitance 18.3±0.1 pF, resting membrane potential −39.6±0.3 mV, and several voltage-activated, outward or inwardly rectifying potassium currents. Using ion channel blockers (barium, TEA, 4-AP, margatoxin, XEN-D0103, and DIDS), flow cytometry, immuno-staining, and RNA-sequencing, we identified Kv1.3, Kv1.5, and Kir2.1 as channels contributing to observed ion currents. MΦ displayed four patterns for outward and two for inward-rectifier potassium currents. Additionally, MΦ showed surface expression of Cx43, a prerequisite for homo- and/or heterotypic electrotonic coupling. Experimental results fed into development of an original computational model to describe cardiac MΦ electrophysiology. Computer simulations to quantitatively assess plausible effects of MΦ on electrotonically coupled CM showed that MΦ can depolarize resting CM, shorten early and prolong late action potential duration, with effects depending on coupling strength and individual MΦ electrophysiological properties, in particular resting membrane potential and presence/absence of
Greiner J, Schiatti T, Kaltenbacher W, et al., 2022, Consecutive-Day Ventricular and Atrial Cardiomyocyte Isolations from the Same Heart: Shifting the Cost-Benefit Balance of Cardiac Primary Cell Research, CELLS, Vol: 11
Yamaguchi Y, Allegrini B, Rapetti-Mauss R, et al., 2021, Hereditary Xerocytosis: Differential Behavior of PIEZO1 Mutations in the N-Terminal Extracellular Domain Between Red Blood Cells and HEK Cells, FRONTIERS IN PHYSIOLOGY, Vol: 12, ISSN: 1664-042X
Emig R, Zgierski-Johnston CM, Timmermann V, et al., 2021, Passive myocardial mechanical properties: meaning, measurement, models., Biophys Rev, Vol: 13, Pages: 587-610, ISSN: 1867-2450
Passive mechanical tissue properties are major determinants of myocardial contraction and relaxation and, thus, shape cardiac function. Tightly regulated, dynamically adapting throughout life, and affecting a host of cellular functions, passive tissue mechanics also contribute to cardiac dysfunction. Development of treatments and early identification of diseases requires better spatio-temporal characterisation of tissue mechanical properties and their underlying mechanisms. With this understanding, key regulators may be identified, providing pathways with potential to control and limit pathological development. Methodologies and models used to assess and mimic tissue mechanical properties are diverse, and available data are in part mutually contradictory. In this review, we define important concepts useful for characterising passive mechanical tissue properties, and compare a variety of in vitro and in vivo techniques that allow one to assess tissue mechanics. We give definitions of key terms, and summarise insight into determinants of myocardial stiffness in situ. We then provide an overview of common experimental models utilised to assess the role of environmental stiffness and composition, and its effects on cardiac cell and tissue function. Finally, promising future directions are outlined.
Abu Nahia K, Migdal M, Quinn TA, et al., 2021, Genomic and physiological analyses of the zebrafish atrioventricular canal reveal molecular building blocks of the secondary pacemaker region, Cellular and Molecular Life Sciences, Vol: 78, Pages: 6669-6687, ISSN: 1420-682X
The atrioventricular canal (AVC) is the site where key structures responsible for functional division between heart regions are established, most importantly, the atrioventricular (AV) conduction system and cardiac valves. To elucidate the mechanism underlying AVC development and function, we utilized transgenic zebrafish line sqet31Et expressing EGFP in the AVC to isolate this cell population and profile its transcriptome at 48 and 72 hpf. The zebrafish AVC transcriptome exhibits hallmarks of mammalian AV node, including the expression of genes implicated in its development and those encoding connexins forming low conductance gap junctions. Transcriptome analysis uncovered protein-coding and noncoding transcripts enriched in AVC, which have not been previously associated with this structure, as well as dynamic expression of epithelial-to-mesenchymal transition markers and components of TGF-β, Notch, and Wnt signaling pathways likely reflecting ongoing AVC and valve development. Using transgenic line Tg(myl7:mermaid) encoding voltage-sensitive fluorescent protein, we show that abolishing the pacemaker-containing sinoatrial ring (SAR) through Isl1 loss of function resulted in spontaneous activation in the AVC region, suggesting that it possesses inherent automaticity although insufficient to replace the SAR. The SAR and AVC transcriptomes express partially overlapping species of ion channels and gap junction proteins, reflecting their distinct roles. Besides identifying conserved aspects between zebrafish and mammalian conduction systems, our results established molecular hallmarks of the developing AVC which underlies its role in structural and electrophysiological separation between heart chambers. This data constitutes a valuable resource for studying AVC development and function, and identification of novel candidate genes implicated in these processes.
Ravens U, Kohl P, 2021, Mechanoelectric feedback in the human heart: A causal affair, HEART RHYTHM, Vol: 18, Pages: 1414-1415, ISSN: 1547-5271
Rog-Zielinska E, Kohl P, 2021, Nanoscopic t-tubular deformation during cardiac mechanical cycle, Publisher: SPRINGER, Pages: 45-45, ISSN: 0175-7571
Jakob D, Klesen A, Darkow E, et al., 2021, Heterogeneity and Remodeling of Ion Currents in Cultured Right Atrial Fibroblasts From Patients With Sinus Rhythm or Atrial Fibrillation, FRONTIERS IN PHYSIOLOGY, Vol: 12
Jakob D, Klesen A, Allegrini B, et al., 2021, Piezol and BKca channels in human atrial fibroblasts: Interplay and remodelling in atrial fibrillation, JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY, Vol: 158, Pages: 49-62, ISSN: 0022-2828
Darkow E, Nguyen TT, Stolina M, et al., 2021, Small Conductance Ca2+-Activated K+ (SK) Channel mRNA Expression in Human Atrial and Ventricular Tissue: Comparison Between Donor, Atrial Fibrillation and Heart Failure Tissue, FRONTIERS IN PHYSIOLOGY, Vol: 12
Emig R, Knodt W, Krussig MJ, et al., 2021, Piezo1 Channels Contribute to the Regulation of Human Atrial Fibroblast Mechanical Properties and Matrix Stiffness Sensing, CELLS, Vol: 10
Rog-Zielinska EA, Scardigli M, Peyronnet R, et al., 2021, Beat-by-Beat Cardiomyocyte T-Tubule Deformation Drives Tubular Content Exchange, CIRCULATION RESEARCH, Vol: 128, Pages: 203-215, ISSN: 0009-7330
Wuelfers EM, Greiner J, Giese M, et al., 2021, Quantitative collagen assessment in right ventricular myectomies form patients with tetralogy of Fallot, EUROPACE, Vol: 23, Pages: I38-I47, ISSN: 1099-5129
Rog-Zielinska EA, Moss R, Kaltenbacher W, et al., 2021, Nano-scale morphology of cardiomyocyte t-tubule/sarcoplasmic reticulum junctions revealed by ultra-rapid high-pressure freezing and electron tomography, JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY, Vol: 153, Pages: 86-92, ISSN: 0022-2828
Quinn TA, Kohl P, 2021, CARDIAC MECHANO-ELECTRIC COUPLING: ACUTE EFFECTS OF MECHANICAL STIMULATION ON HEART RATE AND RHYTHM, PHYSIOLOGICAL REVIEWS, Vol: 101, Pages: 37-92, ISSN: 0031-9333
Müllenbroich MC, Kelly A, Acker C, et al., 2021, Novel Optics-Based Approaches for Cardiac Electrophysiology: A Review., Front Physiol, Vol: 12, ISSN: 1664-042X
Optical techniques for recording and manipulating cellular electrophysiology have advanced rapidly in just a few decades. These developments allow for the analysis of cardiac cellular dynamics at multiple scales while largely overcoming the drawbacks associated with the use of electrodes. The recent advent of optogenetics opens up new possibilities for regional and tissue-level electrophysiological control and hold promise for future novel clinical applications. This article, which emerged from the international NOTICE workshop in 2018, reviews the state-of-the-art optical techniques used for cardiac electrophysiological research and the underlying biophysics. The design and performance of optical reporters and optogenetic actuators are reviewed along with limitations of current probes. The physics of light interaction with cardiac tissue is detailed and associated challenges with the use of optical sensors and actuators are presented. Case studies include the use of fluorescence recovery after photobleaching and super-resolution microscopy to explore the micro-structure of cardiac cells and a review of two photon and light sheet technologies applied to cardiac tissue. The emergence of cardiac optogenetics is reviewed and the current work exploring the potential clinical use of optogenetics is also described. Approaches which combine optogenetic manipulation and optical voltage measurement are discussed, in terms of platforms that allow real-time manipulation of whole heart electrophysiology in open and closed-loop systems to study optimal ways to terminate spiral arrhythmias. The design and operation of optics-based approaches that allow high-throughput cardiac electrophysiological assays is presented. Finally, emerging techniques of photo-acoustic imaging and stress sensors are described along with strategies for future development and establishment of these techniques in mainstream electrophysiological research.
Haerdtner C, Kornemann J, Krebs K, et al., 2020, Inhibition of macrophage proliferation dominates plaque regression in response to cholesterol lowering, BASIC RESEARCH IN CARDIOLOGY, Vol: 115, ISSN: 0300-8428
Al-Shammari H, Latif N, Sarathchandra P, et al., 2020, Expression and function of mechanosensitive ion channels in human valve interstitial cells., PLoS One, Vol: 15, Pages: e0240532-e0240532, ISSN: 1932-6203
BACKGROUND: The ability of heart valve cells to respond to their mechanical environment represents a key mechanism by which the integrity and function of valve cusps is maintained. A number of different mechanotransduction pathways have been implicated in the response of valve cells to mechanical stimulation. In this study, we explore the expression pattern of several mechanosensitive ion channels (MSC) and their potential to mediate mechanosensitive responses of human valve interstitial cells (VIC). METHODS: MSC presence and function were probed using the patch clamp technique. Protein abundance of key MSC was evaluated by Western blotting in isolated fibroblastic VIC (VICFB) and in VIC differentiated towards myofibroblastic (VICMB) or osteoblastic (VICOB) phenotypes. Expression was compared in non-calcified and calcified human aortic valves. MSC contributions to stretch-induced collagen gene expression and to VIC migration were assessed by pharmacological inhibition of specific channels. RESULTS: Two MSC types were recorded in VICFB: potassium selective and cation non-selective channels. In keeping with functional data, the presence of both TREK-1 and Kir6.1 (potassium selective), as well as TRPM4, TRPV4 and TRPC6 (cationic non-selective) channels was confirmed in VIC at the protein level. Differentiation of VICFB into VICMB or VICOB phenotypes was associated with a lower expression of TREK-1 and Kir6.1, and a higher expression of TRPV4 and TRPC6. Differences in MSC expression were also seen in non-calcified vs calcified aortic valves where TREK-1, TRPM4 and TRPV4 expression were higher in calcified compared to control tissues. Cyclic stretch-induced expression of COL I mRNA in cultured VICFB was blocked by RN-9893, a selective inhibitor of TRPV4 channels while having no effect on the stretch-induced expression of COL III. VICFB migration was blocked with the non-specific MSC blocker streptomycin and by GSK417651A an inhibitor of TRPC6/3. CONCLUSION: Aortic VIC ex
Zgierski-Johnston CM, Ayub S, Fernandez MC, et al., 2020, Cardiac pacing using transmural multi-LED probes in channelrhodopsin-expressing mouse hearts, PROGRESS IN BIOPHYSICS & MOLECULAR BIOLOGY, Vol: 154, Pages: 51-61, ISSN: 0079-6107
MacDonald EA, Madl J, Greiner J, et al., 2020, Sinoatrial node structure, mechanics, electrophysiology and the chronotropic response to stretch in rabbit and mouse, Frontiers in Physiology, Vol: 11, Pages: 1-15, ISSN: 1664-042X
The rhythmic electrical activity of the heart’s natural pacemaker, the sinoatrial node (SAN), determines cardiac beating rate (BR). SAN electrical activity is tightly controlled by multiple factors, including tissue stretch, which may contribute to adaptation of BR to changes in venous return. In most animals, including human, there is a robust increase in BR when the SAN is stretched. However, the chronotropic response to sustained stretch differs in mouse SAN, where it causes variable responses, including decreased BR. The reasons for this species difference are unclear. They are thought to relate to dissimilarities in SAN electrophysiology (particularly action potential morphology) between mouse and other species and to how these interact with subcellular stretch-activated mechanisms. Furthermore, species-related differences in structural and mechanical properties of the SAN may influence the chronotropic response to SAN stretch. Here we assess (i) how the BR response to sustained stretch of rabbit and mouse isolated SAN relates to tissue stiffness, (ii) whether structural differences could account for observed differences in BR responsiveness to stretch, and (iii) whether pharmacological modification of mouse SAN electrophysiology alters stretch-induced chronotropy. We found disparities in the relationship between SAN stiffness and the magnitude of the chronotropic response to stretch between rabbit and mouse along with differences in SAN collagen structure, alignment, and changes with stretch. We further observed that pharmacological modification to prolong mouse SAN action potential plateau duration rectified the direction of BR changes during sustained stretch, resulting in a positive chronotropic response akin to that of other species. Overall, our results suggest that structural, mechanical, and background electrophysiological properties of the SAN influence the chronotropic response to stretch. Improved insight into the biophysical determinants of st
Darkow E, Rog-Zielinska EA, Madl J, et al., 2020, The lectin LecA sensitizes the human stretch-activated channel TREK-1 but not piezo1 and binds selectively to cardiac non-myocytes, Frontiers in Physiology, Vol: 11, Pages: 1-16, ISSN: 1664-042X
The healthy heart adapts continuously to a complex set of dynamically changing mechanical conditions. The mechanical environment is altered by, and contributes to, multiple cardiac diseases. Mechanical stimuli are detected and transduced by cellular mechano-sensors, including stretch-activated ion channels (SAC). The precise role of SAC in the heart is unclear, in part because there are few SAC-specific pharmacological modulators. That said, most SAC can be activated by inducers of membrane curvature. The lectin LecA is a virulence factor of Pseudomonas aeruginosa and essential for P. aeruginosa-induced membrane curvature, resulting in formation of endocytic structures and bacterial cell invasion. We investigate whether LecA modulates SAC activity. TREK-1 and Piezo1 have been selected, as they are widely expressed in the body, including cardiac tissue, and they are “canonical representatives” for the potassium selective and the cation non-selective SAC families, respectively. Live cell confocal microscopy and electron tomographic imaging were used to follow binding dynamics of LecA, and to track changes in cell morphology and membrane topology in human embryonic kidney (HEK) cells and in giant unilamellar vesicles (GUV). HEK cells were further transfected with human TREK-1 or Piezo1 constructs, and ion channel activity was recorded using the patch-clamp technique. Finally, freshly isolated cardiac cells were used for studies into cell type dependency of LecA binding. LecA (500 nM) binds within seconds to the surface of HEK cells, with highest concentration at cell-cell contact sites. Local membrane invaginations are detected in the presence of LecA, both in the plasma membrane of cells (by 17 min of LecA exposure) as well as in GUV. In HEK cells, LecA sensitizes TREK-1, but not Piezo1, to voltage and mechanical stimulation. In freshly isolated cardiac cells, LecA binds to non-myocytes, but not to ventricular or atrial cardiomyocytes. This cell type speci
Bers DM, Kohl P, Chen-Izu Y, 2020, Mechanics and energetics in cardiac arrhythmias and heart failure, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 598, Pages: 1275-1277, ISSN: 0022-3751
Kopton RA, Buchmann C, Moss R, et al., 2020, Electromechanical Assessment of Optogenetically Modulated Cardiomyocyte Activity, JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, ISSN: 1940-087X
Izu LT, Kohl P, Boyden PA, et al., 2020, Mechano-electric and mechano-chemo-transduction in cardiomyocytes, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 598, Pages: 1285-1305, ISSN: 0022-3751
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