Speckle-Tracking Echocardiography in Cardio-Oncology and Beyond

Speckle-tracking echocardiography has enabled clinicians to detect changes in myocardial function with more sensitivity than that afforded by traditional diastolic and systolic functional measurements, including left ventricular ejection fraction. Speckle-tracking echocardiography enables evaluation of myocardial strain in terms of strain (percent change in length of a myocardial segment relative to its length at baseline) and strain rate (strain per unit of time). Both measurements have potential for use in diagnosing and monitoring the cardiovascular side effects of cancer therapy. Regional and global strain measurements can independently predict outcomes not only in patients who experience cardiovascular complications of cancer and cancer therapy, but also in patients with a variety of other clinical conditions. This review and case series examine the clinical applications and overall usefulness of speckle-tracking echocardiography in cardio-oncology and, more broadly, in clinical cardiology.

Mechanical Stress Affects Circadian Rhythm in Skeletal Muscle (C2C12 Myoblasts) by Reducing Per/Cry Gene Expression and Increasing Bmal1 Gene Expression

BACKGROUND Circadian rhythm can modulate normal activity of humans in adapting to daily environment changes. Mechanical stress loading affects skeletal muscle development and bio-functions. This study aimed to investigate the effects of mechanical stress loading on circadian rhythm in skeletal muscle (C2C12 cells) and to explore the associated mechanism. MATERIAL AND METHODS C2C12 myoblasts were cultured and treated with mechanical stress loading. After mechanical stress loading for 6 h,12 h, and 24 h, we observed the C2C12 myoblasts and determined gene transcription and protein expression of Clock genes, including Clock, Bmal1, Per, and Cry using RT-PCR and western blot assay. RESULTS Mechanical stress loading triggered C2C12 cells growing by force direction and enhanced the cell proliferation at 6 h, 12 h, and 24 h. Gene transcription and protein expression of the core Clock-associated molecules, Clock and Bmal1, increased from start of loading to 12 h, and decreased from 12 h to 24 h. Gene transcription and protein expression of core Clock-associated molecules, Cry and Per, decreased in the first 12 h (from 6 h to 12 h) and increased in the last 12 h (from 12 h to 24 h). CONCLUSIONS Our study revealed that mechanical stress loading affected circadian rhythm in skeletal muscle (C2C12 myoblasts) through reducing Per/Cry and enhancing Clock/Bmal1 gene expression. This study provides insights for investigating circadian rhythm and associated bio-functions of humans.

Shear-Sensitive lncRNA AF131217.1 Inhibits Inflammation in HUVECs via Regulation of KLF4

Atherosclerosis is one of the most common vascular diseases, and inflammation participates in all stages of its progression. Laminar shear stress protects arteries from atherosclerosis and reduces endothelial inflammation. Long noncoding RNAs have emerged as critical regulators in many diseases, including atherosclerosis. However, the expression and functions of long noncoding RNAs subjected to laminar shear stress in endothelial cells remain unclear. This study aimed to reveal the mechanism by which shear stress-regulated long noncoding RNAs contribute to anti-inflammation. In this study, we identified a novel long noncoding RNA AF131217.1, which was upregulated after laminar shear stress treatment in human umbilical vein endothelial cells. Knockdown of AF131217.1 inhibited flow-mediated reduction of monocyte adhesion VCAM-1 (vascular cell adhesion molecule-1) and ICAM-1 (intercellular adhesion molecule-1) expression and inhibited flow-mediated enhancement of flow-responsive expression of KLF (Kruppel-like factor) 2 and eNOS (endothelial NO synthase). Furthermore, TNF-α (tumor necrosis factor-α) was used to induce an inflammatory response in human umbilical vein endothelial cells. Knockdown of AF131217.1 promoted ICAM-1 and VCAM-1 expression, as well as changes in monocyte adhesion and KLF2 and eNOS expression induced by TNF-α. Mechanistic investigations indicated that AF131217.1 acted as a competing endogenous RNA for miR-128-3p, leading to regulation of its target gene KLF4. In conclusion, our study demonstrates for the first time that laminar shear stress regulates the expression of AF131217.1 in human umbilical vein endothelial cells, and the AF131217.1/miR-128-3p/KLF4 axis plays a vital role in atherosclerosis development.

Longitudinal Deformation of Distal Edge in a New-Generation Stent Caused by Guidewire Entrapment

Longitudinal stent deformation, described in some older stent geometries, prompted design modifications such as reinforcing struts on the proximal end. However, distal edges of stents-also subject to longitudinal force-have not been reinforced. We report a case of guidewire entrapment that deformed the distal edge of a new-generation stent during percutaneous coronary intervention, and we describe our efforts to restore the stent to its initial length. This case highlights the risk of manipulating equipment beyond the position of a newly deployed stent, the ongoing potential for deformation of distal edges in newer stent platforms, and the advisability of treating distal lesions before proximal ones.

Left Circumflex Coronary Artery as the Culprit Vessel in ST-Segment-Elevation Myocardial Infarction

The prevalence of the left circumflex coronary artery (LCx) as the culprit vessel in ST-segment-elevation myocardial infarction (STEMI) is reportedly lowest among that of the 3 main epicardial arteries, and has not been described for non-STEMI (NSTEMI) and stable angina pectoris. We sought to define the distribution of culprit arteries in these clinical presentations and suggest mechanisms for the differences. We reviewed 189 coronary angiograms of patients with STEMI, 203 with NSTEMI, and 548 with stable angina (n=940), and compared distributions of stenotic and culprit coronary arteries (lesions prompting intervention). Obstructive coronary lesions (≥50% narrowing) were more prevalent in the left anterior descending coronary artery (LAD) (36%-38%) and similar in the LCx and right coronary artery (RCA) (27%-29%), regardless of clinical presentation (P <0.01). In NSTEMI and stable angina, culprit vessels and total obstructive disease had the same distribution. In STEMI, however, a culprit LCx was significantly less prevalent (17%) than was total obstructive disease (27%; P <0.01), or a culprit LAD (47%) or RCA (34%) (both P <0.001). In our computed tomographic angiographic model of coronary longitudinal strain (percentage of shortening), LCx strain was only 1.5% ± 2.4%, versus 9.5% ± 2.9% for LAD strain and 10.1% ± 3.9% for RCA strain. In STEMI, LCx plaques seem less prone to rupturing. Culprit and total disease distributions are similar in NSTEMI and angina, suggesting a different ischemic pathophysiology in these presentations. Lower LCx longitudinal strain might contribute to reduced plaque rupture in STEMI.

Fluid shear stress stimulates osteogenic differentiation of human periodontal ligament cells via the extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase signaling pathways

BACKGROUND

Fluid shear stress (FSS) is a major type of mechanical stress that is loaded on human periodontal ligament cells (hPDLCs) during mastication and orthodontic tooth movement. This study aims to clarify the effect of FSS on the osteogenic differentiation of hPDLCs and to further verify the involvement of mitogen-activated protein kinase (MAPK) signaling in this process.

METHODS

After isolation and characterization, hPDLCs were subjected to 2-hour FSS at 12 dynes/cm(2), and cell viability, osteogenic gene mRNA expression, alkaline phosphatase (ALP) activity, secretion of Type I collagen (COL-I), and calcium deposition were assayed. The levels of phosphorylated p38 and phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) in response to FSS were detected by Western blot, and the involvement of ERK1/2 and p38 MAPK signaling pathways in hPDLC osteogenesis under FSS was investigated using the specific MAPK inhibitors U0126 (2Z,3Z)-2,3-bis[amino(2-aminophenylthio)methylene]succinonitrile,ethanol) and SB203580 (4-[4-(4-fluorophenyl)-2-(4-[methylsulfinyl]phenyl)-1H-imidazol-5-yl]pyridine).

RESULTS

The application of FSS on hPDLCs induced an early morphologic change and rearrangement of filamentous actin. ALP activity, messenger RNA (mRNA) levels of osteogenic genes, COL-I, and osteoid nodules were significantly increased by FSS. Moreover, ERK1/2 and p38 were activated in different ways after FSS exposure. U0126 and SB203580 completely blocked the FSS-induced increases in ALP activity and osteogenic gene mRNA expression and osteoid nodules formation.

CONCLUSIONS

FSS is an effective approach for stimulating osteogenic differentiation of hPDLCs. The ERK1/2 and p38 MAPK signaling pathways are involved in this cellular process.

Segmental aortic stiffening contributes to experimental abdominal aortic aneurysm development

BACKGROUND

Stiffening of the aortic wall is a phenomenon consistently observed in age and in abdominal aortic aneurysm (AAA). However, its role in AAA pathophysiology is largely undefined.

METHODS AND RESULTS

Using an established murine elastase-induced AAA model, we demonstrate that segmental aortic stiffening precedes aneurysm growth. Finite-element analysis reveals that early stiffening of the aneurysm-prone aortic segment leads to axial (longitudinal) wall stress generated by cyclic (systolic) tethering of adjacent, more compliant wall segments. Interventional stiffening of AAA-adjacent aortic segments (via external application of surgical adhesive) significantly reduces aneurysm growth. These changes correlate with the reduced segmental stiffness of the AAA-prone aorta (attributable to equalized stiffness in adjacent segments), reduced axial wall stress, decreased production of reactive oxygen species, attenuated elastin breakdown, and decreased expression of inflammatory cytokines and macrophage infiltration, and attenuated apoptosis within the aortic wall, as well. Cyclic pressurization of segmentally stiffened aortic segments ex vivo increases the expression of genes related to inflammation and extracellular matrix remodeling. Finally, human ultrasound studies reveal that aging, a significant AAA risk factor, is accompanied by segmental infrarenal aortic stiffening.

CONCLUSIONS

The present study introduces the novel concept of segmental aortic stiffening as an early pathomechanism generating aortic wall stress and triggering aneurysmal growth, thereby delineating potential underlying molecular mechanisms and therapeutic targets. In addition, monitoring segmental aortic stiffening may aid the identification of patients at risk for AAA.

Adaptor protein p66(Shc) mediates hypertension-associated, cyclic stretch-dependent, endothelial damage

Increased cyclic stretch to the vessel wall, as observed in hypertension, leads to endothelial dysfunction through increased free radical production and reduced nitric oxide bioavailability. Genetic deletion of the adaptor protein p66(Shc) protects mice against age-related and hyperglycemia-induced endothelial dysfunction, as well as atherosclerosis and stroke. Furthermore, p66(Shc) mediates vascular dysfunction in hypertensive mice. However, the direct role of p66(Shc) in mediating mechanical force-induced free radical production is unknown; thus, we studied the effect of cyclic stretch on p66(Shc) activation in primary human aortic endothelial cells and aortic endothelial cells isolated from normotensive and hypertensive rats. Exposure of human aortic endothelial cells to cyclic stretch led to a stretch- and time-dependent p66(Shc) phosphorylation at Ser36 downstream of integrin α5β1 and c-Jun N-terminal kinase. In parallel, nicotinamide adenine dinucleotide phosphate oxidase activation, as well as production of reactive oxygen species, increased, whereas nitric oxide bioavailability decreased. Silencing of p66(Shc) blunted stretch-increased superoxide anion production and nicotinamide adenine dinucleotide phosphate oxidase activation and restored nitric oxide bioavailability. In line with the above, activation of p66(Shc) increased in isolated aortic endothelial cells of spontaneously hypertensive rats compared with normotensive ones. Pathological stretch by activating integrin α5β1 and c-Jun N-terminal kinase phosphorylates p66(Shc) at Ser36, augments reactive oxygen species production via nicotinamide adenine dinucleotide phosphate oxidase, and in turn reduces nitric oxide bioavailability. This novel molecular pathway may be relevant for endothelial dysfunction and vascular disease in hypertension.

Mechanical behavior of fully expanded commercially available endovascular coronary stents

The mechanical behavior of endovascular coronary stents influences their therapeutic efficacy. Through computational studies, researchers can analyze device performance and improve designs. We developed a 1-dimensional finite element method, net-based algorithm and used it to analyze the effects of radial loading and bending in commercially available stents. Our computational study included designs modeled on the Express, Cypher, Xience, and Palmaz stents.We found that stents that did not fully expand were less rigid than the fully expanded stents and, therefore, exhibited larger displacement. Stents with an open-cell design, such as Express-like or Xience-like stents, had a higher bending flexibility. Stents with in-phase circumferential rings, such as the Xience-like stent, had the smallest longitudinal extension when exposed to radial compression forces. Thus, the open-cell model that had in-phase circumferential rings connected by straight horizontal struts exhibited radial stiffness, bending flexibility, and the smallest change in stent length during radial forcing. The Palmaz-like stent was the most rigid of all. These findings are supported by clinical experience.Computer simulations of the mechanical properties of endovascular stents offer sophisticated insights into the mechanical behavior of different stent designs and should be used whenever possible to help physicians decide which stent is best for treating a given lesion. Our 1-dimensional finite element method model is incomparably simpler, faster, and more accurate than the classical 3-dimensional approaches. It can facilitate stent design and may aid in stent selection in the clinical setting.

First human trial of KW39 slotted-tube stents: for percutaneous coronary intervention

The KW39 stent is a balloon-expandable, stainless-steel, slotted-tube stent, newly designed to adjust to the shape of the coronary arteries. We evaluated the clinical efficacy and safety of KW39 stent-based percutaneous coronary interventions in human native coronary arteries. A total of 105 patients (110 lesions), with a diagnosis of stable angina, acute coronary syndrome, or asymptomatic myocardial ischemia, were included in this prospective study. The primary endpoint was the target-lesion revascularization rate at the conclusion of a 6-month follow-up period. The secondary endpoints were the rates of technical and procedural success and the rate of major adverse cardiac events (defined as cardiac death, myocardial infarction, and target-lesion revascularization) in the course of the 6 months after stent placement. The 6-month target-lesion revascularization rate was 8.6%. The KW39 stent was highly satisfactory in regard to all secondary endpoint comparisons. Binary (>50%) in-stent restenosis was observed in 22 of 110 lesions (20%). The mean diameter stenosis at 6 months after percutaneous coronary intervention was 35.1% ± 14.4%, and the mean late lumen loss was 1.06 ± 0.48 mm. Stepwise multivariate analysis showed probable causal associations between adverse local environments for stent implantation and the subsequent need for target-lesion revascularization. We conclude that KW39 stent implantation was technically feasible and clinically safe in the patient population that we studied. The results of the safety endpoints, including cardiac death and acute myocardial infarction, were acceptable.

Cryoplasty for peripheral artery disease in an unselected patient population in a tertiary center

Endovascular treatment of peripheral artery occlusive disease has suboptimal long-term patency rates. The addition of cryoplasty to balloon angioplasty, which involves the application of cold thermal energy to atherosclerotic plaque, might improve outcomes and decrease the need for reintervention. At a single tertiary center, we retrospectively analyzed data from the angiograms and medical records of unselected patients who underwent cryoplasty for peripheral artery disease from January 2004 through November 2006. We calculated rates of freedom from amputation, freedom from intervention, and freedom from death and examined the data using the Kaplan-Meier method. Paired t tests were used to compare the ankle-brachial indices before and after cryoplasty. The study population comprised 99 patients who received treatment for 132 atherosclerotic lesions, including 62 lesions in the superficial femoral artery, 28 in the popliteal artery, and 25 in arteries below the knee; 71 patients completed follow-up (64 ± 57 wk). Short-term periprocedural success was achieved in 98.5% of the interventions. Dissections occurred in 12.2% of patients treated successfully without bail-out stenting or additional balloon inflations. At 6 months, more than 88% of the patients were alive and had not had an amputation. However, reintervention was required for 42% of patients. Mean ankle-brachial indices improved significantly after treatment (P < 0.0001). Our results show that cryoplasty for treatment of peripheral artery disease is safe and has a high rate of periprocedural success. However, long-term efficacy is compromised because of the frequent need for reintervention.

Right coronary artery distribution of myocardial bridging: an unusual case presenting with ST-Elevation myocardial infarction

Myocardial bridging has been observed to provoke symptoms in association with strenuous physical activity and hypertrophic cardiomyopathy; more recently, bridging has been thought to cause coronary vasospasm. Autopsy findings tend to reveal higher incidences of bridging than do angiography series, but both show an almost uniform predilection for left coronary artery distribution--especially in regard to bridging that manifests itself clinically. Herein, we report an unusual case of myocardial bridging with right coronary artery distribution and important clinical implications for physicians' management of similar cases in the future.

Shear force at the cell-matrix interface: enhanced analysis for microfabricated post array detectors

The interplay of mechanical forces between the extracellular environment and the cytoskeleton drives development, repair, and senescence in many tissues. Quantitative definition of these forces is a vital step in understanding cellular mechanosensing. Microfabricated post array detectors (mPADs) provide direct measurements of cell-generated forces during cell adhesion to extracellular matrix. A new approach to mPAD post labeling, volumetric imaging, and an analysis of post bending mechanics determined that cells apply shear forces and not point moments at the matrix interface. In addition, these forces could be accurately resolved from post deflections by using images of post tops and bases. Image analysis tools were then developed to increase the precision and throughput of post centroid location. These studies resulted in an improved method of force measurement with broad applicability and concise execution using a fully automated force analysis system. The new method measures cell-generated forces with less than 5% error and less than 90 seconds of computational time. Using this approach, we demonstrated direct and distinct relationships between cellular traction force and spread cell surface area for fibroblasts, endothelial cells, epithelial cells and smooth muscle cells.

Measuring cell viscoelastic properties using a force-spectrometer: influence of protein-cytoplasm interactions

Cell adhesive and rheological properties play a very important role in cell transmigration through the endothelial barrier, in particular in the case of inflammation (leukocytes) or cancer metastasis (cancer cells). In order to characterize cell viscoelastic properties, we have designed a force spectrometer (AFM) which can stretch cells thereby allowing measurement of their rheological properties. This custom-made force spectrometer allows two different visualizations, one lateral and one from below. It allows investigation of the effects of rheology involved during cell stretching. To test the ability of our system to characterize such viscoelastic properties, ICAM-1 transfected CHO cells were analyzed. Two forms of ICAM-1 were tested; wild type ICAM-1, which can interact with the cytoskeleton, and a mutant form which lacks the cytoplasmic domain, and is unable to associate with the cytoskeleton. Stretching experiments carried out on these cells show the formation of long filaments. Using a previous model of filament elongation, we could determine the viscoelastic properties of a single cell. As expected, different viscoelastic components were found between the wild type and the mutant, which reveal that the presence of interactions between ICAM-1 and the cytoskeleton increases the stiffness of the cell.

Localization of calcium and microfilament changes in mechanically stressed cells

We combined fluorescence labeling, digital image processing, and micromanipulation to investigate the intracellular events induced by inflicting a mechanical stress on rat basophilic leukemia cells. Our findings were as follows: 1. Most cells displayed a localized calcium rise in response to micropipet aspiration. This represented an average threefold increase as compared to resting level, and it was observed during the first 10 s following aspiration. A slow return to initial level occurred within about 3 min. Further, this calcium rise involved a mobilization of intracellular stores, since it was not prevented by adding a calcium chelator into the extracellular medium. 2. All micropipet-aspirated cells displayed a local accumulation of microfilaments, with a preferential localization in the cell protrusions or near the pipet tips. 3. No absolute correlation was found between the localization of calcium rise and cytoskeletal accumulation. 4. Cell deformability was decreased when intracellular calcium was maintained at a constant (high or low) level with ionomycin and/or EGTA. It is concluded that cells have a general ability to respond to mechanical stimulation by a coordinated set of events. More parameters must be studied before the mechanisms of cell shape regulation are fully understood.