Shock wave induced endothelial damage--in situ analysis by confocal laser scanning microscopy

Proinflammatory Reaction and Cytoskeletal Alterations in Endothelial Cells after Shock Wave Exposure

BACKGROUND

Although the effects on human organs by shock waves (SWs) induced by medical treatments or high-energy trauma are well recognized, little is known about the effects on the cellular level. Since blood vessel injury is a common finding after SW exposure, we assessed the in vitro effects of SWs on human umbilical vein endothelial cells (HUVECs).

METHODS

An in vitro trauma model was used to expose HUVEC monolayers to focused SWs or to shock waves plus cavitation (SWC), a subsequent phenomenon that is often considered the main cause of SW vascular injury.

RESULTS

SWs alone did not cause any changes in the studied variables. In contrast, HUVEC monolayers exposed to SWC exhibited discrete central lesions with extensive cell death. Cells peripheral to the main lesion area displayed disassembly of dense peripheral bands and formation of actin stress fibers, indicating increased intercellular gaps. Expression of P-selectin was enhanced 11-fold compared with controls, whereas expression of E-selectin and intercellular adhesion molecule 1 was enhanced 8-fold (p < .05) and 1.5-fold (p < .01), respectively. The latter responses were preceded by nuclear translocation of nuclear factor kappaB subunit p65 by 16% (p < .01). When compared with mechanically produced lesions used as controls, SWC lesions exhibited an impaired regeneration rate of the endothelial cell layer (p < .001). Redistribution of centrosomes toward the lesion borders was less effective in the SWC samples compared with the mechanically produced lesions (p < .01).

CONCLUSIONS

SWC lesions were associated with a switch to an endothelial proinflammatory phenotype, with an impaired regeneration rate and changes in cytoskeletal functions.

Métodos físicos utilizados para oclusão de varizes dos membros inferiores

A terapia das varizes dos membros inferiores tem sido realizada classicamente por cirurgia e escleroterapia, sendo a escolha basicamente dependente do seu calibre. Entretanto, a associação de técnicas costuma ser uma necessidade para a obtenção de bons resultados. Os meios físicos surgiram no final da década de 50 e continuaram a progredir com grande diversidade quanto à natureza, princípio físico e efeitos. A complexidade tecnológica é bastante variável. Eletrocoagulação, laser, luz intensa pulsada, crioesclerose endovascular, ultra-som e microondas são meios físicos potencialmente viáveis para esta condição. Entretanto, com algumas exceções, pouco tem sido descrito fora dos centros de pesquisa, e a participação como opção terapêutica ainda necessita de uma melhor definição do papel. O artigo tem como objetivo descrever os métodos físicos empregados ou em estudo para a terapia de varizes.

Effects of radial shock waves on membrane permeability and viability of chondrocytes and structure of articular cartilage in equine cartilage explants

OBJECTIVE

To investigate in vitro effects of radial shock waves on membrane permeability, viability, and structure of chondrocytes and articular cartilage.

SAMPLE POPULATION

Cartilage explants obtained from the third metacarpal and metatarsal bones of 6 horses.

PROCEDURE

Equine cartilage was subjected to radial shock waves and then maintained as explants in culture for 48 hours. Treatment groups consisted of a negative control group; application of 500, 2,000, and 4,000 impulses by use of a convex handpiece (group A); and application of 500, 2,000, and 4,000 impulses by use of a concave handpiece (group B). Effects on explant structure were evaluated by use of environmental scanning electron microscopy (ESEM). Membrane permeability was determined by release of lactate dehydrogenase (LDH). Chondrocyte viability was assessed by use of vital cell staining. Comparisons of LDH activity and nonviable cell percentages were performed by ANOVA.

RESULTS

Cell membrane permeability increased significantly after application of 2,000 and 4,000 impulses in groups A and B. A significant decrease in cell viability was observed for application of 4,000 impulses in explants of group A. There was no detectable damage to integrity of cartilage explants observed in any treatment group by use of ESEM.

CONCLUSIONS AND CLINICAL RELEVANCE

Radial shock waves do not appear to structurally damage articular cartilage but do impact chondrocyte viability and membrane permeability. Caution should be exercised when extremely high periarticular pulse doses are used until additional studies can determine the long-term outcome of these effects and appropriate periarticular treatment regimens can be validated.

Bioeffect of ultrasound on endothelial cells in vitro

The effects of low-intensity ultrasound (US) on biological systems have been investigated extensively; however, the effects of ultrasound stimulation on endothelial cells were rarely studied. In this study, 1 MHz, pulsed 1:4, and four different spatial-average temporal-peak intensities (0.5, 1.0, 1.6, and 2W/cm2) of ultrasound were used to stimulate endothelial cells for 10 min per day. The results showed that ultrasound (intensity 1.6-2.0W/cm2) treatment after 6 days enhanced the nitric oxide (NO) and Ca2+ release from the endothelial cells but did not promote cell growth. In addition, ultrasound stimulation changed the cellular morphology and orientation, and increased extracellular matrix secretion from endothelial cells.

Effects of Extracorporeal Shock Wave Therapy on Bone

Extracorporeal shock waves have been used for 30 years to fragment uroliths for nonsurgical treatment for urolithiasis in humans. Applied to bone, shock waves delivered at the appropriate energy and pulse number, can stimulate osteogenesis. In Europe, shock waves are routinely used to treat nonunions in humans despite poor understanding of the mechanism of action. Shock wave therapy has also been used clinically in horses. Preliminary experimental studies indicate that shock wave therapy does not damage soft tissue in the distal aspect of the equine limb and can stimulate osteogenesis throughout the depth of the near cortex of the metacarpus and metatarsus.

Mechanisms of shock wave induced endothelial cell injury

BACKGROUND AND OBJECTIVES

Medical procedures, for example, laser angioplasty and extracorporeal lithotripsy as well as high-energy trauma expose human tissues to shock waves (SWs) that may cause tissue injury. The mechanisms for this injury, often affecting blood vessel walls, are poorly understood. Here we sought to assess the role of two suggested factors, viz., cavitation or reactive oxygen species (ROS).

STUDY DESIGN/MATERIALS AND METHODS

A laser driven flyer-plate model was used to expose human umbilical cord vein endothelial cell (HUVEC) monolayers to SWs or to SWs plus cavitation (SWC). Cell injury was quantified with morphometry, trypan blue staining, and release of (51)Cr from labeled HUVECs.

RESULTS

HUVECs, exposed to SWs only, could not be distinguished from controls in morphological appearance or ability to exclude trypan blue. Yet, release of (51)Cr, indicated a significant cell injury (P < 0.05). HUVEC cultures exposed to SWC, exhibited cell detachment and cell membrane damage detectable with trypan blue. Release of (51)Cr was fourfold compared to SW samples (P < 0.01). Signs of cell injury were evident at 15 minutes and did not change over the next 4 hours. No protective effects of ROS scavengers were demonstrated.

CONCLUSIONS

Independent of ROS, SWC generated an immediate cell injury, which can explain, for example, vessel wall perturbation described in relation to SW treatments and trauma.

Shock wave therapy (Orthotripsy) in musculoskeletal disorders

Extracorporeal shock wave therapy, which now is used routinely for urolithiasis, has gained increasing acceptance in Europe for some musculoskeletal problems and has led to the inception of clinical studies in the United States. The authors have reviewed the available literature to assess the biologic effects of shock waves on human musculoskeletal tissues, the credibility of published studies on therapeutic applications, and the potential for more widespread application of this modality to various skeletal and near-skeletal disorders. The primary advantage of extracorporeal shock wave therapy is its noninvasive nature and seemingly minimal complications when applied to musculoskeletal tissues.

Absence of spinal response to extracorporeal shock waves on the endogenous opioid systems in the rat

Extracorporeal shock wave therapy (ESWT) seems to be a new therapeutic strategy for chronic pain due to tendopathies. Neurophysiological mechanisms of action for pain relief following ESWT are still unknown. The aim of this study was to investigate if the analgesic effect of ESWT is caused by modulation of the endogenous spinal opioid system. Rats were treated with two different energy flux densities (0.04 and 0.11mJ/mm(2)) and immunohistochemical analysis of met-enkephalin (MRGL) and dynorphin (Dyn) was performed at 4 or 72 h after ESWT. ESWT had no modulatory influence on the expression of the spinal opioid systems. Different energy doses or repetitive treatment did not alter MRGL or Dyn immunoreactivity in the spinal cord. Furthermore, a delayed effect of ESWT at 72 h after treatment was not detectable. We conclude from these findings that the analgesic effects of ESWT treatment are not supported by endogenous opioids.

Erosion of artificial endothelia in vitro by pulsed ultrasound: acoustic pressure, frequency, membrane orientation and microbubble contrast agent dependence

The erosion of cells from fibroblast monolayers simulating the vascular endothelium by 20 micros pulses of ultrasound at 500 Hz PRF was studied in relation to the peak negative acoustic pressure (P-; 0.0-2.5 MPa), ultrasound (US) frequency (1.0, 2.1 or 3.5 MHz), orientation of the monolayer (i.e., simulating the sites of ultrasound entry/exit from a blood vessel) and the presence or absence of a microbubble contrast agent (3 Vol% Albunex). The a priori hypotheses were that erosion of the monolayers would: 1. arise due to insonation treatment, 2. arise as a consequence of cavitation activity and, thus, increase with increasing P- at constant frequency, and decrease with increasing frequency at constant P-, 3. be significantly increased by the presence of a microbubble contrast agent, and 4. have a weak dependence on monolayer orientation. The data support these hypotheses. Under the most severe exposure conditions used, most of the affected cells appeared to have been lysed; however, a substantial number of viable cells were dislodged from the monolayer surface.

[Physical parameters of extracorporeal shock waves]

Prerequisites for the successful investigation of the mechanism of action of ESWT (extracorporeal shockwave therapy) and the establishment of treatment standards, are the ability to measure, and a knowledge of, the physical parameters involved. The most accurate measurements are obtained with laser hydrophones. Various parameters (amplitude, rise time, pulse width, pressure pulse decay, rarification phase) of a typical shock wave can thus be determined. These can then be used to calculate energy flux density, focal extent, focal volume and as well as focal energy, effective energy in a defined area, and effective biological energy. These parameters can be utilized to work out a theoretical treatment protocol.

Shock waves in vascular diseases: an in-vitro study

Three human aortic specimens were used for this in-vitro study on the effects of shock waves on the arterial wall. Specimen one was from a normal (for age) healthy aorta. The full abdominal length was used (including mesenteric and renal arteries and the aortoiliac bifurcation), divided into six pieces (3 cm). The pieces were placed and fixed into degassed water. Shock waves (SW) were focused onto the aortic wall by means of a B-mode ultrasound imager. An SW generator (Minilith SL1, Storz Medical AG, Kreuzlingen, Switzerland) was used for setting of energy flux density between 0.03 and 0.5 mJ/mm2. The six aortic pieces (excluding piece 1, placed in water and left untreated as control) were treated with SW at increasing energy levels. A second aortic specimen of a man with arteriosclerotic plaques was also used and the experiment repeated at energy levels 1, 5, and 8. Another specimen of normal thoracic aorta was exposed at energy levels 1 and 8 only. Energy levels delivered onto the aortic walls were selected from theoretically destructive levels to minimal levels known not to alter vascular tissues. High-resolution ultrasounds of the aortic segments were performed with a 10 MHz high-resolution, broad-band (ATL 3000, USA) probe in water before and after SW application to detect structural changes in the wall after SW. Histology was performed with a standard hematoxylin-eosin staining.

RESULTS

The aortic pieces did not show macroscopic damages at visual examination, and at the ultrasound examination no visible changes were observed even at higher levels of SW energy. Also no effects were seen by histology. In conclusion, no damaging effects were observed, visually, by ultrasound, or by histology. At these energy levels SW appear to be safe and do not produce any damage to the aortic wall. Therefore, SW could be considered a safe, nondamaging procedure for potential treatment (ie, thrombolysis) in which vessel walls could be involved. Theoretically it is possible that functional changes could be observed in vivo including cell permeability modifications and other alterations (including changes in the potential of the cells in SW fields to modify themselves and to divide). At the energy levels described in this study SW could, theoretically be, safely used for vascular applications (ie, treating venous and arterial thrombi or in arterial plaques modification) without altering major, structural, arterial wall characteristics. Lesions or alterations that have a different density from the normal wall (thrombi or plaques) could be differently sensitive to the same dosage of SW. These differences in acoustic impedance characteristics could be used for potential treatments with SW without damaging the arterial wall.