The plate body: 3D ultrastructure of a facultative organelle of alveolar epithelial type II cells involved in SP-A trafficking.

Plate bodies are facultative organelles occasionally described in the adult lungs of various species, including sheep and goat. They consist of multiple layers of plate-like cisterns with an electron dense middle bar. The present study was performed to elucidate the three-dimensional (3D) characteristics of this organelle and its presumed function in surfactant protein A (SP-A) biology. Archived material of four adult goat lungs and PFA-fixed lung samples of two adult sheep lungs were used for the morphological and immunocytochemical parts of this study, respectively. 3D imaging was performed by electron tomography and focused ion beam scanning electron microscopy (FIB-SEM). Immuno gold labeling was used to analyze whether plate bodies are positive for SP-A. Transmission electron microscopy revealed the presence of plate bodies in three of four goat lungs and in both sheep lungs. Electron tomography and FIB-SEM characterized the plate bodies as layers of two up to over ten layers of membranous cisterns with the characteristic electron dense middle bar. The membranes of the plates were in connection with the rough endoplasmic reticulum and showed vesicular inclusions in the middle of the plates and a vesicular network at the sides of the organelle. Immuno gold labeling revealed the presence of SP-A in the vesicular network of plate bodies but not in the characteristic plates themselves. In conclusion, the present study clearly proves the connection of plate bodies with the rough endoplasmic reticulum and the presence of a vesicular network as part of the organelle involved in SP-A trafficking.

Spermidine supplementation and voluntary activity differentially affect obesity-related structural changes in the mouse lung.

Obesity is associated with lung function impairment and respiratory diseases; however, the underlying pathophysiological mechanisms are still elusive, and therapeutic options are limited. This study examined the effects of prolonged excess fat intake on lung mechanics and microstructure and tested spermidine supplementation and physical activity as intervention strategies. C57BL/6N mice fed control diet (10% fat) or high-fat diet (HFD; 60% fat) were left untreated or were supplemented with 3 mM spermidine, had access to running wheels for voluntary activity, or a combination of both. After 30 wk, lung mechanics was assessed, and left lungs were analyzed by design-based stereology. HFD exerted minor effects on lung mechanics and resulted in higher body weight and elevated lung, air, and septal volumes. The number of alveoli was higher in HFD-fed animals. This was accompanied by an increase in epithelial, but not endothelial, surface area. Moreover, air-blood barrier and endothelium were significantly thicker. Neither treatment affected HFD-related body weights. Spermidine lowered lung volumes as well as endothelial and air-blood barrier thicknesses toward control levels and substantially increased the endothelial surface area under HFD. Activity resulted in decreased volumes of lung, septa, and septal compartments but did not affect vascular changes in HFD-fed mice. The combination treatment showed no additive effect. In conclusion, excess fat consumption induced alveolar capillary remodeling indicative of impaired perfusion and gas diffusion. Spermidine alleviated obesity-related endothelial alterations, indicating a beneficial effect, whereas physical activity reduced lung volumes apparently by other, possibly systemic effects.

A transmural gradient of myocardial remodeling in early-stage heart failure with preserved ejection fraction in the pig.

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction. This study aimed to analyze whether early HFpEF is already associated with ultrastructural alterations and whether they differ quantitatively among the layers of the left ventricular wall. HFpEF was induced in pigs by deoxy-corticosterone acetate (DOCA) treatment along with a high-salt/high lipid diet over 3 months and compared with weight-matched normal pigs (n = 5 each). Samples of the left ventricle were taken and processed for light and electron microscopy. Interstitial fibrosis, subcellular composition of cardiomyocytes and mean cardiomyocyte diameter were evaluated by stereology in subendocardial, midmyocardial and subepicardial regions. DOCA enhanced the mean cardiomyocyte diameter in all locations of the ventricle wall to the same degree. The subcellular composition did not differ between the locations and was not altered by DOCA. The volume fraction of interstitium was smaller in the subendocardium of DOCA group than of control group. Within the interstitium, the volume fraction of collagen fibrils (between cardiomyocytes) was increased in the subendocardial and midmyocardial wall layers of the DOCA group but not in the subepicardial layer. Although the capillary length density and average supply area were not altered in response to DOCA in any of the wall layers, the volume fraction of blood vessels related to the interstitial space was enhanced in the subendocardium of the DOCA group but not in the other wall layers. In conclusion, cardiomyocyte changes due to DOCA were similar in subepicardial, midmyocardial and subendocardial regions but DOCA-induced changes in the interstitium appeared to be more pronounced in the subendocardial ventricular wall layers. This suggests a pivotal role of the subendocardial interstitium in the pathogenesis of HFpEF.

Early-stage heart failure with preserved ejection fraction in the pig: a cardiovascular magnetic resonance study.

BACKGROUND: The hypertensive deoxy-corticosterone acetate (DOCA)-salt-treated pig (hereafter, DOCA pig) was recently introduced as large animal model for early-stage heart failure with preserved ejection fraction (HFpEF). The aim of the present study was to evaluate cardiovascular magnetic resonance (CMR) of DOCA pigs and weight-matched control pigs to characterize ventricular, atrial and myocardial structure and function of this phenotype model. METHODS: Five anesthetized DOCA and seven control pigs underwent 3 T CMR at rest and during dobutamine stress. Left ventricular/atrial (LV/LA) function and myocardial mass (LVMM), strains and torsion were evaluated from (tagged) cine imaging. 4D phase-contrast measurements were used to assess blood flow and peak velocities, including transmitral early-diastolic (E) and myocardial tissue (E') velocities and coronary sinus blood flow. Myocardial perfusion reserve was estimated from stress-to-rest time-averaged coronary sinus flow. Global native myocardial T1 times were derived from prototype modified Look-Locker inversion-recovery (MOLLI) short-axis T1 maps. After in-vivo measurements, transmural biopsies were collected for stereological evaluation including the volume fractions of interstitium (VV(int/LV)) and collagen (VV(coll/LV)). Rest, stress, and stress-to-rest differences of cardiac and myocardial parameters in DOCA and control animals were compared by t-test. RESULTS: In DOCA pigs LVMM (p < 0.001) and LV wall-thickness (end-systole/end-diastole, p = 0.003/p = 0.007) were elevated. During stress, increase of LV ejection-fraction and decrease of end-systolic volume accounted for normal contractility reserves in DOCA and control pigs. Rest-to-stress differences of cardiac index (p = 0.040) and end-diastolic volume (p = 0.042) were documented. Maximal (p = 0.042) and minimal (p = 0.012) LA volumes in DOCA pigs were elevated at rest; total LA ejection-fraction decreased during stress (p = 0.006). E' was lower in DOCA pigs, corresponding to higher E/E' at rest (p = 0.013) and stress (p = 0.026). Myocardial perfusion reserve was reduced in DOCA pigs (p = 0.031). T1-times and VV(int/LV) did not differ between groups, whereas VV(coll/LV) levels were higher in DOCA pigs (p = 0.044). CONCLUSIONS: LA enlargement, E' and E/E' were the markers that showed the most pronounced differences between DOCA and control pigs at rest. Inadequate increase of myocardial perfusion reserve during stress might represent a metrics for early-stage HFpEF. Myocardial T1 mapping could not detect elevated levels of myocardial collagen in this model. TRIAL REGISTRATION: The study was approved by the local Bioethics Committee of Vienna, Austria (BMWF-66.010/0091-II/3b/2013).

Assessment of cardiac fibrosis: a morphometric method comparison for collagen quantification.

Fibrotic remodeling of the heart is a frequent condition linked to various diseases and cardiac dysfunction. Collagen quantification is an important objective in cardiac fibrosis research; however, a variety of different histological methods are currently used that may differ in accuracy. Here, frequently applied collagen quantification techniques were compared. A porcine model of early stage heart failure with preserved ejection fraction was used as an example. Semiautomated threshold analyses were imprecise, mainly due to inclusion of noncollagen structures or failure to detect certain collagen deposits. In contrast, collagen assessment by automated image analysis and light microscopy (LM)-stereology was more sensitive. Depending on the quantification method, the amount of estimated collagen varied and influenced intergroup comparisons. PicroSirius Red, Masson's trichrome, and Azan staining protocols yielded similar results, whereas the measured collagen area increased with increasing section thickness. Whereas none of the LM-based methods showed significant differences between the groups, electron microscopy (EM)-stereology revealed a significant collagen increase between cardiomyocytes in the experimental group, but not at other localizations. In conclusion, in contrast to the staining protocol, section thickness and the quantification method being used directly influence the estimated collagen content and thus, possibly, intergroup comparisons. EM in combination with stereology is a precise and sensitive method for collagen quantification if certain prerequisites are considered. For subtle fibrotic alterations, consideration of collagen localization may be necessary. Among LM methods, LM-stereology and automated image analysis are appropriate to quantify fibrotic changes, the latter depending on careful control of algorithm and comparable section staining.NEW & NOTEWORTHY Direct comparison of frequently applied histological fibrosis assessment techniques revealed a distinct relation of measured collagen and utilized quantification method as well as section thickness. Besides electron microscopy-stereology, which was precise and sensitive, light microscopy-stereology and automated image analysis proved to be appropriate for collagen quantification. Moreover, consideration of collagen localization might be important in revealing minor fibrotic changes.