Morphometric Remodeling Research Articles

Reduction of Cardiac Fibrosis by Interference With YAP-Dependent Transactivation.

Conversion of cardiac stromal cells into myofibroblasts is typically associated with hypoxia conditions, metabolic insults, and/or inflammation, all of which are predisposing factors to cardiac fibrosis and heart failure. We hypothesized that this conversion could be also mediated by response of these cells to mechanical cues through activation of the Hippo transcriptional pathway. The objective of the present study was to assess the role of cellular/nuclear straining forces acting in myofibroblast differentiation of cardiac stromal cells under the control of YAP (yes-associated protein) transcription factor and to validate this finding using a pharmacological agent that interferes with the interactions of the YAP/TAZ (transcriptional coactivator with PDZ-binding motif) complex with their cognate transcription factors TEADs (TEA domain transcription factors), under high-strain and profibrotic stimulation. We employed high content imaging, 2-dimensional/3-dimensional culture, atomic force microscopy mapping, and molecular methods to prove the role of cell/nuclear straining in YAP-dependent fibrotic programming in a mouse model of ischemia-dependent cardiac fibrosis and in human-derived primitive cardiac stromal cells. We also tested treatment of cells with Verteporfin, a drug known to prevent the association of the YAP/TAZ complex with their cognate transcription factors TEADs. Our experiments suggested that pharmacologically targeting the YAP-dependent pathway overrides the profibrotic activation of cardiac stromal cells by mechanical cues in vitro, and that this occurs even in the presence of profibrotic signaling mediated by TGF-β1 (transforming growth factor beta-1). In vivo administration of Verteporfin in mice with permanent cardiac ischemia reduced significantly fibrosis and morphometric remodeling but did not improve cardiac performance. Our study indicates that preventing molecular translation of mechanical cues in cardiac stromal cells reduces the impact of cardiac maladaptive remodeling with a positive effect on fibrosis.

Therapeutic benefits of intravenous cardiosphere-derived cell therapy in rats with pulmonary hypertension.

Pulmonary arterial hypertension (PAH) is a progressive condition characterized by occlusive pulmonary arteriopathy, in which survival remains poor despite pharmacologic advances. The aim of this study was to evaluate the ability of cardiosphere-derived cells (CDCs), cardiac progenitor cells with potent anti-inflammatory and immunomodulatory properties, to attenuate hemodynamic and morphometric remodeling of the right ventricle (RV) and pulmonary arterioles in rats with established monocrotaline (MCT)-induced PAH. Animals were divided into 3 groups: 1) Control (CTL), 2) PAH in which CDCs were centrally infused (CDC) and 3) PAH in which saline was given (Sham). Significant increments in RV systolic pressure (RVSP) and RV hypertrophy were noted in Sham animals compared to CTL. In CDC rats at day 35, RSVP fell (- 38%; p< 0.001) and RV hypertrophy decreased (-26%; p< 0.01). TAPSE and cardiac output were preserved in all 3 groups at day 35. Pulmonary arteriolar wall thickness was greater in Sham rats compared to CTL, and reduced in CDC animals for vessels 20–50 μm (P<0.01; back to CTL levels) and 50–80μm (P<0.01) in diameter. The macrophage population was increased in Sham animals compared to CTL (P< 0.001), but markedly reduced in CDC rats. In conclusion, infusion of CDCs markedly attenuated several key pathophysiologic features of PAH. As adjunctive therapy to PAH-specific agents, CDCs have the potential to impact on the pathobiology of adverse pulmonary arteriolar remodeling, by acting on multiple mechanisms simultaneously.

The mitochondrial dynamism-mitophagy-cell death interactome: multiple roles performed by members of a mitochondrial molecular ensemble.

Mitochondrial research is experiencing a renaissance, in part, because of the recognition that these endosymbiotic descendants of primordial protobacteria seem to be pursuing their own biological agendas. Not only is mitochondrial metabolism required to produce most of the biochemical energy that supports their eukaryotic hosts (us) but mitochondria can actively (through apoptosis and programmed necrosis) or passively (through reactive oxygen species toxicity) drive cellular dysfunction or demise. The cellular mitochondrial collective autoregulates its population through biogenic renewal and mitophagic culling; mitochondrial fission and fusion, 2 components of mitochondrial dynamism, are increasingly recognized as playing central roles as orchestrators of these processes. Mitochondrial dynamism is rare in striated muscle cells, so cardiac-specific genetic manipulation of mitochondrial fission and fusion factors has proven useful for revealing noncanonical functions of mitochondrial dynamics proteins. Here, we review newly described functions of mitochondrial fusion/fission proteins in cardiac mitochondrial quality control, cell death, calcium signaling, and cardiac development. A mechanistic conceptual paradigm is proposed in which cell death and selective organelle culling are not distinct processes, but are components of a unified and integrated quality control mechanism that exerts different effects when invoked to different degrees, depending on pathophysiological context. This offers a plausible explanation for seemingly paradoxical expression of mitochondrial dynamics and death factors in cardiomyocytes wherein mitochondrial morphometric remodeling does not normally occur and the ability to recover from cell suicide is severely limited.

Diaphragm remodeling and compensatory respiratory mechanics in a canine model of Duchenne muscular dystrophy

Ventilatory insufficiency remains the leading cause of death and late stage morbidity in Duchenne muscular dystrophy (DMD). To address critical gaps in our knowledge of the pathobiology of respiratory functional decline, we used an integrative approach to study respiratory mechanics in a translational model of DMD. In studies of individual dogs with the Golden Retriever muscular dystrophy (GRMD) mutation, we found evidence of rapidly progressive loss of ventilatory capacity in association with dramatic morphometric remodeling of the diaphragm. Within the first year of life, the mechanics of breathing at rest, and especially during pharmacological stimulation of respiratory control pathways in the carotid bodies, shift such that the primary role of the diaphragm becomes the passive elastic storage of energy transferred from abdominal wall muscles, thereby permitting the expiratory musculature to share in the generation of inspiratory pressure and flow. In the diaphragm, this physiological shift is associated with the loss of sarcomeres in series (∼ 60%) and an increase in muscle stiffness (∼ 900%) compared with those of the nondystrophic diaphragm, as studied during perfusion ex vivo. In addition to providing much needed endpoint measures for assessing the efficacy of therapeutics, we expect these findings to be a starting point for a more precise understanding of respiratory failure in DMD.

Abstract 18862: Wall Shear Stress in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) leads to morphometric remodeling of the pulmonary arteries. Computational fluid dynamics (CFD) modeling has the potential to reveal continuum metrics associated with the stress acting on the vascular endothelium in a non- invasive manner. We hypothesized that the PA endothelium of PAH patients will be subject to abnormal wall shear stress (WSS), and thus investigated the relationship of spatially averaged WSS (SAWSS) with invasive measurements of pulmonary vascular resistance (PVR) and compliance (C). Methods: Computed tomography angiography (CTA) and RHC were used to acquire images and hemodynamic data in 19 PH patients. Each patient’s pulmonary vascular tree was reconstructed from CT images up to 6 generations. The inlets and outlets were extended to 10 times their hydraulic diameters and a volumetric mesh created within element dimensions determined by a systematic mesh convergence study. Each CFD model was simulated using a structured tree outflow boundary condition. Constant flow rate simulations were performed using the numerical solver Fluent (ANSYS Inc., Lebanon, NH) after adjusting for patient-specific scaling parameters. Finally, SAWSS on the surface of the pulmonary arterial endothelium was obtained during post-processing. Correlations between SAWSS and hemodynamics were made. Results: Figure 1 shows a power-regression correlation between SAWSS and PVR, and linear-regression correlation between SAWSS and C. SAWSS decreases for increasing PVR and decreasing C. Conclusions: Pulmonary arterial WSS obtained by our CFD model can be used as a physiologically relevant quantitative metric of PAH severity, which likely precedes vascular and ventricular remodeling. Its application as a non-invasive surrogate for disease progression and evaluation of response to PH specific therapies needs further investigation.

PULMONARY ARTERIAL WALL SHEAR STRESS AND ITS IMPACT ON RIGHT VENTRICULAR FUNCTION IN PULMONARY ARTERIAL HYPERTENSION: PRELIMINARY ASSESSMENT BY COMPUTATIONAL FLUID DYNAMICS

Pulmonary arterial hypertension (PAH) can lead to substantial morphometric remodeling of the pulmonary arteries. Previous studies have established coupling relationships between right ventricular (RV) function and pulmonary arterial hemodynamics. Our objective is to develop and validate a

Effect of chang run tong on the biomechanical and morphometric remodeling of colon and rectum in streptozotocin-induced diabetic rats

The present study investigates the effect of Chang Run Tong (CRT) on the biomechanical and morphometrical remodeling of colon and rectum in streptozotocin-induced diabetic rats. The colonic and rectal segments were obtained from diabetic (DM), CRT-treated diabetic (T1, high dosage: 50 g/kg/day; T2, low dosage: 25 g/kg/day) and normal (Con) rats. The experimental period was 60 d. The blood glucose level and body weight were measured. The circumferential length, wall thickness, and opening angle were measured from the segments in the no-load and zero-stress states. The residual strain was computed from the morphometry data. The step-wise distension was done on the colonic segment (from 0 to 20 cmH2O). The circumferential and longitudinal stresses and strains were computed. The blood glucose level was significantly higher and the body weight was significantly lower in the DM, T1, and T2 groups compared to those in the Con group (p ＜ 0.01, p ＜ 0.001). The glucose level did not differ among the DM, T1, and T2 groups. The wet weight per unit length to body weight ratio, wall thickness, cross-sectional wall area, opening angle, and absolute value of residual strain of colonic and rectal segments in the DM group were significantly higher than those in the Con group (p ＜ 0.05 and p ＜ 0.01), and those in the T1 group, but not those in the T2 group, were significantly lower than those in the DM group (p ＜ 0.05, p ＜ 0.01). Furthermore, the circumferential and longitudinal stiffness of the colonic wall in the DM group was higher than those in the Con group. T1, but not T2, treatment could significantly decrease the colonic wall stiffness in both directions (p ＜ 0.01). CRT (high dose) treatment could partly restore the morphometric and biomechanical remodeling of the lower gastrointestinal tract in diabetic rats.

Spontaneous and Bolus-induced Motility in the Chronically Obstructed Guinea-Pig Small Intestine In vitro

Partial obstruction of the small intestine results in dysmotility and morphometric changes proximal to the site of obstruction. However, our understanding of the relation between the morphometric remodeling and change in the motility pattern during chronic obstruction is sparse. The aim of this study was to investigate the effect of partial chronic intestinal obstruction on motility, morphology, and collagen content proximal and distal to the site of obstruction. Twenty guinea-pigs with partial intestinal obstruction and eight sham-operated controls lived for four weeks. Spontaneous and bolus-induced motility was recorded in isolated intestinal segments proximal and distal to the site of obstruction using a perfused low-compliance pressure-measuring system in vitro. After the motility experiments, the specimens were fixed at 2 kPa luminal distension pressure and sampled for histomorphometric determination of luminal radius, layer thickness, and wall thickness. Total wall collagen was also determined. The area under the curve (AUC) of spontaneous contractions and the amplitude, frequency, and AUC for the bolus-induced motility were higher in the proximal segments of the banded animals compared to distal segments and to the intestinal segments in the control animals (P < 0.05). The radius-to-thickness ratio was lowest in the proximal segments of the obstructed animals (P < 0.01). The collagen content was three times higher proximal to the site of obstruction when compared to distal locations and to the controls (P < 0.01). The AUC at 2 ml bolus injections plotted against the radius-to-thickness ratio showed a strong association (r = 0.97 for control, and r = 0.99 for obstruction, P < 0.01). No correlation was found between the collagen content and AUC. In conclusion, partial intestinal obstruction in guinea pigs caused pronounced changes in morphology and motility. An association was found between the radius-to-thickness ratio and bolus-induced motility.

Morphological Changes of the Left Atrial Appendage After Catheter Ablation of Atrial Fibrillation

The left atrial appendage (LAA) has been proven to be the most important site of thrombus formation in patients with atrial fibrillation (AF). However, the information regarding the morphometric alteration of the LAA related to the outcome of AF ablation is still lacking. Thus, we evaluated the long-term changes of the LAA morphology in patients undergoing catheter ablation of AF using magnetic resonance angiography (MRA). Group 1 included 15 controls without any AF history. Group 2 included 40 patients with drug-refractory paroxysmal AF. They were divided into two subgroups: group 2a included 30 patients without AF recurrence after pulmonary vein (PV) ablation. Group 2b included 10 patients with late recurrence of AF. The LAA morphology before and after (20 +/- 11 months) ablation was evaluated by three-dimensional MRA. The group 2 patients had a larger baseline LAA size (including the LAA orifice, neck, and length) and less eccentric LAA orifice and neck. After the AF ablation, there was a significant reduction in the LAA size in the group 2a patients, and the morphology of the LAA neck became more eccentric during the follow-up period. In group 2b, the LAA size increased and no significant change in the eccentricity of the orifice and neck could be noted. The morphometric remodeling of the LAA in the AF patients could be reversed after a successful ablation of the AF. Progressive dilation of the LAA was noted in the patients with AF recurrence. These structural changes in the LAA may play a role in reducing the potential risk of cerebrovascular accidents.

Coronary arterial tree remodeling in right ventricular hypertrophy.

We investigated coronary vascular adaptations occurring in right ventricular hypertrophy (RVH). Six pigs had RVH induced by pulmonary artery stenosis for 5 wk. Three pigs served as controls. At autopsy we made silicone elastomer casts of the right coronary arteries (RCA) and collected morphometric data. We organized the segments and their diameters and lengths into a framework of a modified Strahler's ordering scheme in which the order number of an offspring is increased only if its diameter is greater than the diameters of its parents by a specific amount. The segments of the same order arranged in series are combined into elements. In RVH the total number of orders of vessels was larger than the control by 1; the total number of elements in each order increased greatly, whereas the diameters and lengths of each order decreased somewhat. The total RCA resistance decreased in RVH mainly because the total cross-sectional area (CSA) of every order was increased. Because the diameters of the resistance vessels decreased, this decrease in total RCA resistance was due to a numerical increase in resistance vessels. These findings indicate that new flow channels have been established. In contrast, the RCA was remodeled in that the lumen diameter increased. Pressure-flow curves showed a decrease of coronary resistance in RVH, in agreement with the morphometric findings. We conclude that there is significant remodeling of the coronary arterial vasculature in RVH, and any future analysis of coronary hemodynamics of the right ventricle in hypertrophy must take the morphometric remodeling into account.

The Effect of Radial Keratotomy on the Corneal Endothelium

Morphometric analysis of the corneal endothelium was performed on 11 eyes of patients who underwent anterior radial keratotomy with the contralateral eye serving as the controls. We analyzed cell density, variation in cell size (polymegethism), and cell shape (pleomorphism) by computer analysis of central and midperipheral specular micrograms one year after surgery. The central endothelial density decreased from 2,503 to 2,419 cells/mm2 (3.3% decrease). The coefficient of variation in cell size (polymegethism) was 0.290 preoperatively and 0.309 postoperatively centrally. Central hexagonality was reduced centrally from 61.4% preoperatively to 56.8% in the operated on eye. These differences were not statistically significant (P greater than .05). In a separate subgroup of six patients, midperipheral specular microscopy under and between incisions disclosed a similar pattern of mild cell density decrease and morphometric remodeling one year after surgery. No morphometric characteristic was significantly different from the central control values (P greater than .05), suggesting that the corneal endothelial monolayer had stabilized one year after radial keratotomy.