Publications by authors named "Sergey V Buravkov"

9 Publications

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Ultrastructural Analysis of Volumetric Histotripsy Bio-effects in Large Human Hematomas.

Ultrasound Med Biol 2021 Sep 9;47(9):2608-2621. Epub 2021 Jun 9.

Laboratory for Industrial and Medical Ultrasound, Physics Faculty, M. V. Lomonosov Moscow State University, Moscow, Russian Federation; Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA.

Large-volume soft tissue hematomas are a serious clinical problem, which, if untreated, can have severe consequences. Current treatments are associated with significant pain and discomfort. It has been reported that in an in vitro bovine hematoma model, pulsed high-intensity focused ultrasound (HIFU) ablation, termed histotripsy, can be used to rapidly and non-invasively liquefy the hematoma through localized bubble activity, enabling fine-needle aspiration. The goals of this study were to evaluate the efficiency and speed of volumetric histotripsy liquefaction using a large in vitro human hematoma model. Large human hematoma phantoms (85 cc) were formed by recalcifying blood anticoagulated with citrate phosphate dextrose/saline-adenine-glucose-mannitol solution. Typical boiling histotripsy pulses (10 or 2 ms) or hybrid histotripsy pulses using higher-amplitude and shorter pulses (0.4 ms) were delivered at 1% duty cycle while continuously translating the HIFU focus location. Histotripsy exposures were performed under ultrasound guidance with a 1.5-MHz transducer (8-cm aperture, F# = 0.75). The volume of liquefied lesions was determined by ultrasound imaging and gross inspection. Untreated hematoma samples and samples of the liquefied lesions aspirated using a fine needle were analyzed cytologically and ultrastructurally with scanning electron microscopy. All exposures resulted in uniform liquid-filled voids with sharp edges; liquefaction speed was higher for exposures with shorter pulses and higher shock amplitudes at the focus (up to 0.32, 0.68 and 2.62 mL/min for 10-, 2- and 0.4-ms pulses, respectively). Cytological and ultrastructural observations revealed completely homogenized blood cells and fibrin fragments in the lysate. Most of the fibrin fragments were less than 20 μm in length, but a number of fragments were up to 150 μm. The lysate with residual debris of that size would potentially be amenable to fine-needle aspiration without risk for needle clogging in clinical implementation.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2021.05.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8355095PMC
September 2021

Treating Porcine Abscesses with Histotripsy: A Pilot Study.

Ultrasound Med Biol 2021 03 26;47(3):603-619. Epub 2020 Nov 26.

Department of Radiology, University of Washington, Seattle, Washington, USA.

Infected abscesses are walled-off collections of pus and bacteria. They are a common sequela of complications in the setting of surgery, trauma, systemic infections and other disease states. Current treatment is typically limited to antibiotics with long-term catheter drainage, or surgical washout when inaccessible to percutaneous drainage or unresponsive to initial care efforts. Antibiotic resistance is also a growing concern. Although bacteria can develop drug resistance, they remain susceptible to thermal and mechanical damage. In particular, short pulses of focused ultrasound (i.e., histotripsy) generate mechanical damage through localized cavitation, representing a potential new paradigm for treating abscesses non-invasively, without the need for long-term catheterization and antibiotics. In this pilot study, boiling and cavitation histotripsy treatments were applied to subcutaneous and intramuscular abscesses developed in a novel porcine model. Ultrasound imaging was used to evaluate abscess maturity for treatment monitoring and assessment of post-treatment outcomes. Disinfection was quantified by counting bacteria colonies from samples aspirated before and after treatment. Histopathological evaluation of the abscesses was performed to identify changes resulting from histotripsy treatment and potential collateral damage. Cavitation histotripsy was more successful in reducing the bacterial load while having a smaller treatment volume compared with boiling histotripsy. The results of this pilot study suggest focused ultrasound may lead to a technology for in situ treatment of acoustically accessible abscesses.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2020.10.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7855811PMC
March 2021

Pilot in vivo studies on transcutaneous boiling histotripsy in porcine liver and kidney.

Sci Rep 2019 12 27;9(1):20176. Epub 2019 Dec 27.

Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA.

Boiling histotripsy (BH) is a High Intensity Focused Ultrasound (HIFU) method for precise mechanical disintegration of target tissue using millisecond-long pulses containing shocks. BH treatments with real-time ultrasound (US) guidance allowed by BH-generated bubbles were previously demonstrated ex vivo and in vivo in exposed porcine liver and small animals. Here, the feasibility of US-guided transabdominal and partially transcostal BH ablation of kidney and liver in an acute in vivo swine model was evaluated for 6 animals. BH parameters were: 1.5 MHz frequency, 5-30 pulses of 1-10 ms duration per focus, 1% duty cycle, peak acoustic powers 0.9-3.8 kW, sonication foci spaced 1-1.5 mm apart in a rectangular grid with 5-15 mm linear dimensions. In kidneys, well-demarcated volumetric BH lesions were generated without respiratory gating and renal medulla and collecting system were more resistant to BH than cortex. The treatment was accelerated 10-fold by using shorter BH pulses of larger peak power without affecting the quality of tissue fractionation. In liver, respiratory motion and aberrations from subcutaneous fat affected the treatment but increasing the peak power provided successful lesion generation. These data indicate BH is a promising technology for transabdominal and transcostal mechanical ablation of tumors in kidney and liver.
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http://dx.doi.org/10.1038/s41598-019-56658-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6934604PMC
December 2019

Inactivation of Planktonic Escherichia coli by Focused 1-MHz Ultrasound Pulses with Shocks: Efficacy and Kinetics Upon Volume Scale-Up.

Ultrasound Med Biol 2018 09 23;44(9):1996-2008. Epub 2018 Jun 23.

Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA.

This study addresses inactivation of E. coli in either 5- or 10-mL volumes, which were 50- to 100-fold greater than used in an earlier study (Brayman et al. 2017). Cells were treated with 1-MHz pulsed high-intensity focused ultrasound (10 cycles, 2-kHz repetition frequency, +65/-12.8 MPa focal pressures). The surviving fraction was assessed by coliform assay, and inactivation demonstrated curvilinear kinetics. The reduction of surviving fraction to 50% required 2.5 or 6 min in 5- or 10-mL samples, respectively. Exposure of 5 mL for 20 min reduced the surviving fraction to ∼1%; a similar exposure of 10-mL samples reduced the surviving fraction to ∼10%. Surviving cells from 5-min exposures appeared normal under light microscopy, with minimal debris; after 20 min, debris dominated. Transmission electron microscopy images of insonated samples showed some undamaged cells, a few damaged but largely intact cells and comminuted debris. Cellular damage associated with substantive but incomplete levels of inactivation can be variable, ranging from membrane holes tens of nanometers in diameter to nearly complete comminution.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2018.05.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135241PMC
September 2018

Molecular Bases of Brain Preconditioning.

Front Neurosci 2017 25;11:427. Epub 2017 Jul 25.

Department of Physiology and General Pathology, Medical Faculty, Lomonosov Moscow State UniversityMoscow, Russia.

Preconditioning of the brain induces tolerance to the damaging effects of ischemia and prevents cell death in ischemic penumbra. The development of this phenomenon is mediated by mitochondrial adenosine triphosphate-sensitive potassium ([Formula: see text]) channels and nitric oxide signaling (NO). The aim of this study was to investigate the dynamics of molecular changes in mitochondria after ischemic preconditioning (IP) and the effect of pharmacological preconditioning (PhP) with the [Formula: see text]-channels opener diazoxide on NO levels after ischemic stroke in rats. Immunofluorescence-histochemistry and laser-confocal microscopy were applied to evaluate the cortical expression of electron transport chain enzymes, mitochondrial [Formula: see text]-channels, neuronal and inducible NO-synthases, as well as the dynamics of nitrosylation and nitration of proteins in rats during the early and delayed phases of IP. NO cerebral content was studied with electron paramagnetic resonance (EPR) spectroscopy using spin trapping. We found that 24 h after IP in rats, there is a two-fold decrease in expression of mitochondrial [Formula: see text]-channels ( = 0.012) in nervous tissue, a comparable increase in expression of cytochrome c oxidase ( = 0.008), and a decrease in intensity of protein S-nitrosylation and nitration ( = 0.0004 and = 0.001, respectively). PhP led to a 56% reduction of free NO concentration 72 h after ischemic stroke simulation ( = 0.002). We attribute this result to the restructuring of tissue energy metabolism, namely the provision of increased catalytic sites to mitochondria and the increased elimination of NO, which prevents a decrease in cell sensitivity to oxygen during subsequent periods of severe ischemia.
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http://dx.doi.org/10.3389/fnins.2017.00427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524930PMC
July 2017

IFN-gamma priming of adipose-derived stromal cells at "physiological" hypoxia.

J Cell Physiol 2018 Feb 11;233(2):1535-1547. Epub 2017 Aug 11.

Cell Physiology Laboratory, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.

Multipotent mesenchymal stromal cells (MSCs) are considered cue regulators of tissue remodeling. Their activity is strongly governed by local milieu, where O level is most important. The elevation of inflammatory mediators and acute O lowering may additionally modulate MSC activity. In present paper the priming effects of IFN-gamma on adipose tissue-derived MSCs (ASCs) at tissue-related O level (5%) and acute hypoxic stress (0.1% O ) were assessed as alterations of ASCs' CFU-F, proliferation, migration, osteo-commitment. IFN-gamma priming provoked ROS elevation, cell growth slowdown, attenuation of both spontaneous and induced osteodifferentiation of tissue O -adapted ASCs. The prominent changes in ASC cytoskeleton-related gene transcription was detected. IFN-gamma exposure shifted the ASC paracrine profile, suppressing the production of VEGF and IL-8, while MCP-1 and IL-6 were stimulated. Conditioned medium of IFN-gamma-primed ASCs did not activate vessel growth in the CAM assay, but induced endothelial cell migration in "wound closure." Short-term hypoxia suppressed CFU-F number, IFN-gamma-induced elevation of IL-6 and endothelial cell migration, while it abolished IFN-gamma-provoked VEGF inhibition. After N-acetyl cysteine treatment ROS level was partly abolished providing additional enhancement of IL-6 and suppression of IL-8 and VEGF production. These findings demonstrated that paracrine activity of ASCs in part may be governed by ROS level. Thus, this study first demonstrated that IFN-gamma priming itself and in combination with acute O deprivation could supply dual effects on ASC functions providing both stimulatory and hampering effects. The equilibrium of these factors is a substantial requirement for the execution of MSC remodeling functions.
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http://dx.doi.org/10.1002/jcp.26046DOI Listing
February 2018

Acute Hypoxic Stress Affects Migration Machinery of Tissue O-Adapted Adipose Stromal Cells.

Stem Cells Int 2016 28;2016:7260562. Epub 2016 Dec 28.

Institute of Biomedical Problems, Russian Academy of Science, Khoroshevskoe Shosse 76A, Moscow 123007, Russia; Lomonosov Moscow State University, Faculty of Fundamental Medicine, Lomonosovsky Prospect 31-5, Moscow 117192, Russia.

The ability of mesenchymal stromal (stem) cells (MSCs) to be mobilised from their local depot towards sites of injury and to participate in tissue repair makes these cells promising candidates for cell therapy. Physiological O tension in an MSC niche in vivo is about 4-7%. However, most in vitro studies of MSC functional activity are performed at 20% O. Therefore, this study focused on the effects of short-term hypoxic stress (0.1% O, 24 h) on adipose tissue-derived MSC motility at tissue-related O level. No significant changes in integrin expression were detected after short-term hypoxic stress. However, O deprivation provoked vimentin disassembly and actin polymerisation and increased cell stiffness. In addition, hypoxic stress induced the downregulation of , and expression, the products of which are known to be involved in leading edge formation and cell translocation. These changes were accompanied by the attenuation of targeted and nontargeted migration of MSCs after short-term hypoxic exposure, as demonstrated in scratch and transwell migration assays. These results indicate that acute hypoxic stress can modulate MSC function in their native milieu, preventing their mobilisation from sites of injury.
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http://dx.doi.org/10.1155/2016/7260562DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5225392PMC
December 2016

Human adipose-tissue derived stromal cells in combination with hypoxia effectively support ex vivo expansion of cord blood haematopoietic progenitors.

PLoS One 2014 28;10(4):e0124939. Epub 2015 Apr 28.

Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.

The optimisation of haematopoietic stem and progenitor cell expansion is on demand in modern cell therapy. In this work, haematopoietic stem/progenitor cells (HSPCs) have been selected from unmanipulated cord blood mononuclear cells (cbMNCs) due to adhesion to human adipose-tissue derived stromal cells (ASCs) under standard (20%) and tissue-related (5%) oxygen. ASCs efficiently maintained viability and supported further HSPC expansion at 20% and 5% O2. During co-culture with ASCs, a new floating population of differently committed HSPCs (HSPCs-1) grew. This suspension was enriched with СD34+ cells up to 6 (20% O2) and 8 (5% O2) times. Functional analysis of HSPCs-1 revealed cobble-stone area forming cells (CAFCs) and lineage-restricted colony-forming cells (CFCs). The number of CFCs was 1.6 times higher at tissue-related O2, than in standard cultivation (20% O2). This increase was related to a rise in the number of multipotent precursors - BFU-E, CFU-GEMM and CFU-GM. These changes were at least partly ensured by the increased concentration of MCP-1 and IL-8 at 5% O2. In summary, our data demonstrated that human ASCs enables the selection of functionally active HSPCs from unfractionated cbMNCs, the further expansion of which without exogenous cytokines provides enrichment with CD34+ cells. ASCs efficiently support the viability and proliferation of cord blood haematopoietic progenitors of different commitment at standard and tissue-related O2 levels at the expense of direct and paracrine cell-to-cell interactions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0124939PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4412539PMC
December 2015

Mechanical characteristics of mesenchymal stem cells under impact of silica-based nanoparticles.

Nanoscale Res Lett 2014 5;9(1):284. Epub 2014 Jun 5.

Department of Molecular and Cell Biomedicine, State Scientific Center of Russian Federation Institute of Biomedical Problems of the Russian Academy of Sciences, Khoroshevskoyoe shosse, 76a, Moscow 123007, Russia ; Faculty of Fundamental Medicine, Lomonosov Moscow State University, Moscow 119192, Russia.

Silica-based nanoparticles (NPs) pose great potential for medical and biological applications; however, their interactions with living cells have not been investigated in full. The objective of this study was to analyze the mechanical characteristics of mesenchymal stem cells when cultured in the presence of silica (Si) and silica-boron (SiB) nanoparticles. Cell stiffness was measured using atomic force microscopy; F-actin structure was evaluated using TRITC-phalloidin by confocal microscopy. The obtained data suggested that the cell stiffness increased within the following line: 'Control' - 'Si' - 'SiB' (either after 1-h cultivation or 24-h incubation). Moreover, the cell stiffness was found to be higher after 1-h cultivation as compared to 24-h cultivation. This result shows that there is a two-phase process of particle diffusion into cells and that the particles interact directly with the membrane and, further, with the submembranous cytoskeleton. Conversely, the intensity of phalloidin fluorescence dropped within the same line: Control - Si - SiB. It could be suggested that the effects of silica-based particles may result in structural reorganization of cortical cytoskeleton with subsequent stiffness increase and concomitant F-actin content decrease (for example, in recruitment of additional actin-binding proteins within membrane and regrouping of actin filaments).
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http://dx.doi.org/10.1186/1556-276X-9-284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055799PMC
June 2014
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