Binding of wheat germ agglutinin in the matrix of rat tracheal cartilage

Novel Fluorescence-Based Methods to Determine Infarct and Scar Size in Murine Models of Reperfused Myocardial Infarction

Determination of infarct and scar size following myocardial infarction (MI) is commonly used to evaluate the efficacy of potential cardioprotective treatments in animal models. However, histological methods to determine morphological features in the infarcted heart have barely improved since implementation while still consuming large parts of the tissue and offering little options for parallel analyses. We aim to develop a new fluorescence technology for determining infarct area and area at risk that is comparable to 2,3,5-triphenyltetrazolium chloride (TTC) staining but allows for multiple analyses on the same heart tissue. For early and late time points following MI, we compared classical histochemical approaches with fluorescence staining methods. Reperfused MI was induced in male mice, the hearts were extracted 24 h, 7-, 21-, or 28-days later and fluorescently stained by combining Hoechst and phalloidin. This approach allowed for clear visualization of the infarct area, the area at ischemic risk and the remote area not affected by MI. The combined fluorescence staining correlated with the classic TTC/Evans Blue staining 24 h after MI (r = 0.8334). In later phases (>7 d) post-MI, wheat germ agglutinin (WGA) is equally accurate as classical Sirius Red (r = 0.9752), Masson's (r = 0.9920) and Gomori's Trichrome (r = 0.8082) staining for determination of scar size. Additionally, feasibility to co-localize fluorescence-stained immune cells in specific regions of the infarcted myocardium was demonstrated with this protocol. In conclusion, this new procedure for determination of post-MI infarct size is not inferior to classical TTC staining, yet provides substantial benefits, including the option for unbiased software-assisted analysis while sparing ample residual tissue for additional analyses. Overall, this enhances the data quality and reduces the required animal numbers consistent with the 3R concept of animal experimentation.

Performance of xenogeneic pulmonary visceral pleura as bioprosthetic heart valve cusps in swine

Objective

Bovine pericardium is common biological material for bioprosthetic heart valve. There remains a significant need, however, to improve bioprosthetic valves for longer-term outcomes. This study aims to evaluate the chronic performance of bovine pulmonary visceral pleura (PVP) as bioprosthetic valve cusps.

Methods

The PVP was extracted from the bovine lung and fixed in 0.625% glutaraldehyde overnight at room temperature. The PVP valve cusps for the bioprosthetic valve were tailored using a laser cutter. Three leaflets were sewn onto a nitinol stent. Six PVP bioprosthetic valves were loaded into the test chamber of the heart valve tester to complete 100 million cycles. Six other PVP bioprosthetic valves were transcardially implanted to replace pulmonary artery valve of six pigs. Fluoroscopy and intracardiac echocardiography were used for in vivo assessments. Thrombosis, calcification, inflammation, and fibrosis were evaluated in the terminal study. Histologic analyses were used for evaluations of any degradation or calcification.

Results

All PVP bioprosthetic valves completed 100 million cycles without significant damage or tears. In vivo assessments showed bioprosthetic valve cusps open and coaptation at four months post-implant. No calcification and thrombotic deposits, inflammation, and fibrosis were observed in the heart or pulmonary artery. The histologic analyses showed complete and compact elastin and collagen fibers in the PVP valve cusps. Calcification-specific stains showed no calcific deposit in the PVP valve cusps.

Conclusions

The accelerated wear test demonstrates suitable mechanical strength of PVP cusps for heart valve. The swine model demonstrates that the PVP valve cusps are promising for valve replacement.

JavaCyte, a novel open-source tool for automated quantification of key hallmarks of cardiac structural remodeling

Many cardiac pathologies involve changes in tissue structure. Conventional analysis of structural features is extremely time-consuming and subject to observer bias. The possibility to determine spatial interrelations between these features is often not fully exploited. We developed a staining protocol and an ImageJ-based tool (JavaCyte) for automated histological analysis of cardiac structure, including quantification of cardiomyocyte size, overall and endomysial fibrosis, spatial patterns of endomysial fibrosis, fibroblast density, capillary density and capillary size. This automated analysis was compared to manual quantification in several well-characterized goat models of atrial fibrillation (AF). In addition, we tested inter-observer variability in atrial biopsies from the CATCH-ME consortium atrial tissue bank, with patients stratified by their cardiovascular risk profile for structural remodeling. We were able to reproduce previous manually derived histological findings in goat models for AF and AV block (AVB) using JavaCyte. Furthermore, strong correlation was found between manual and automated observations for myocyte count (r = 0.94, p < 0.001), myocyte diameter (r = 0.97, p < 0.001), endomysial fibrosis (r = 0.98, p < 0.001) and capillary count (r = 0.95, p < 0.001) in human biopsies. No significant variation between observers was observed (ICC = 0.89, p < 0.001). We developed and validated an open-source tool for high-throughput, automated histological analysis of cardiac tissue properties. JavaCyte was as accurate as manual measurements, with less inter-observer variability and faster throughput.

Genetic reduction of the extracellular matrix protein versican attenuates inflammatory cell infiltration and improves contractile function in dystrophic mdx diaphragm muscles

There is a persistent, aberrant accumulation of V0/V1 versican in skeletal muscles from patients with Duchenne muscular dystrophy and in diaphragm muscles from mdx mice. Versican is a provisional matrix protein implicated in fibrosis and inflammation in various disease states, yet its role in the pathogenesis of muscular dystrophy is not known. Here, female mdx and male hdf mice (haploinsufficient for the versican allele) were bred. In the resulting F1 mdx-hdf male pups, V0/V1 versican expression in diaphragm muscles was decreased by 50% compared to mdx littermates at 20-26 weeks of age. In mdx-hdf mice, spontaneous physical activity increased by 17% and there was a concomitant decrease in total energy expenditure and whole-body glucose oxidation. Versican reduction improved the ex vivo strength and endurance of diaphragm muscle strips. These changes in diaphragm contractile properties in mdx-hdf mice were associated with decreased monocyte and macrophage infiltration and a reduction in the proportion of fibres expressing the slow type I myosin heavy chain isoform. Given the high metabolic cost of inflammation in dystrophy, an attenuated inflammatory response may contribute to the effects of versican reduction on whole-body metabolism. Altogether, versican reduction ameliorates the dystrophic pathology of mdx-hdf mice as evidenced by improved diaphragm contractile function and increased physical activity.

Multifunctional targeting daunorubicin plus quinacrine liposomes, modified by wheat germ agglutinin and tamoxifen, for treating brain glioma and glioma stem cells

Most anticancer drugs are not able to cross the blood-brain barrier (BBB) effectively while surgery and radiation therapy cannot eradicate brain glioma cells and glioma stem cells (GSCs), hence resulting in poor prognosis with high recurrence rates. In the present study, a kind of multifunctional targeting daunorubicin plus quinacrine liposomes was developed for treating brain glioma and GSCs. Evaluations were performed on in-vitro BBB model, murine glioma cells, GSCs, and GSCs bearing mice. Results showed that the multifunctional targeting daunorubicin plus quinacrine liposomes exhibited evident capabilities in crossing the BBB, in killing glioma cells and GSCs and in diminishing brain glioma in mice. Action mechanism studies indicated that the enhanced efficacy of the multifunctional targeting drugs-loaded liposomes could be due to the following aspects: evading the rapid elimination from blood circulation; crossing the BBB effectively; improving drug uptake by glioma cells and GSCs; down-regulating the overexpressed ABC transporters; inducing apoptosis of GSCs via up-regulating apoptotic receptor/ligand (Fas/Fasl), activating apoptotic enzymes (caspases 8, 9 and 3), activating pro-apoptotic proteins (Bax and Bok), activating tumor suppressor protein (P53) and suppressing anti-apoptotic proteins (Bcl-2 and Mcl-1). In conclusion, the multifunctional targeting daunorubicin plus quinacrine liposomes could be used as a potential therapy for treating brain glioma and GSCs.

Serum amyloid A impairs the antiinflammatory properties of HDL

HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however, the effect of the inflammatory state on the functional properties of HDL on adipocytes is unknown. Here, we found that HDL from mice injected with AgNO3 fails to inhibit palmitate-induced inflammation and reduces cholesterol efflux from 3T3-L1 adipocytes. Moreover, HDL isolated from obese mice with moderate inflammation and humans with systemic lupus erythematosus had similar effects. Since serum amyloid A (SAA) concentrations in HDL increase with inflammation, we investigated whether elevated SAA is a causal factor in HDL dysfunction. HDL from AgNO3-injected mice lacking Saa1.1 and Saa2.1 exhibited a partial restoration of antiinflammatory and cholesterol efflux properties in adipocytes. Conversely, incorporation of SAA into HDL preparations reduced antiinflammatory properties but not to the same extent as HDL from AgNO3-injected mice. SAA-enriched HDL colocalized with cell surface-associated extracellular matrix (ECM) of adipocytes, suggesting impaired access to the plasma membrane. Enzymatic digestion of proteoglycans in the ECM restored the ability of SAA-containing HDL to inhibit palmitate-induced inflammation and cholesterol efflux. Collectively, these findings indicate that inflammation results in a loss of the antiinflammatory properties of HDL on adipocytes, which appears to partially result from the SAA component of HDL binding to cell-surface proteoglycans, thereby preventing access of HDL to the plasma membrane.

Wheat germ agglutinin staining as a suitable method for detection and quantification of fibrosis in cardiac tissue after myocardial infarction

The quantification of fibrotic tissue is an important task in the analysis of cardiac remodeling. The use of established fibrosis staining techniques is limited on frozen cardiac tissue sections due to a reduced color contrast compared to paraffin embedded sections. We therefore used FITC-labeled wheat germ agglutinin (WGA), which marks fibrotic tissue in comparable quality as the established picrosirius red (SR) staining, for the staining of post myocardial infarction scar tissue. The fibrosis amount was quantified in a histogram-based approach using the non-commercial image processing program ImageJ. Our results clearly demonstrate that WGA-FITC is a suitable marker for cardiac fibrosis in frozen tissue sections. In combination with the histogram-based analysis, this new quantification approach is i) easy and fast to perform; ii) suitable for raw frozen tissue sections; and iii) allows the use of additional antibodies in co-immunostaining.

Beta-1 integrin is important for the structural maintenance and homeostasis of differentiating fiber cells

β1-Integrin is a heterodimeric transmembrane protein that has roles in both cell-extra-cellular matrix and cell-cell interactions. Conditional deletion of β1-integrin from all lens cells during embryonic development results in profound lens defects, however, it is less clear whether this reflects functions in the lens epithelium alone or whether this protein plays a role in lens fibers. Thus, a conditional approach was used to delete β1-integrin solely from the lens fiber cells. This deletion resulted in two distinct phenotypes with some lenses exhibiting cataracts while others were clear, albeit with refractive defects. Analysis of "clear" conditional knockout lenses revealed that they had profound defects in fiber cell morphology associated with the loss of the F-actin network. Physiological measurements found that the lens fiber cells had a twofold increase in gap junctional coupling, perhaps due to differential localization of connexins 46 and 50, as well as increased water permeability. This would presumably facilitate transport of ions and nutrients through the lens, and may partially explain how lenses with profound structural abnormalities can maintain transparency. In summary, β1-integrin plays a role in maintaining the cellular morphology and homeostasis of the lens fiber cells.

Electrical Integration of Human Embryonic Stem Cell-Derived Cardiomyocytes in a Guinea Pig Chronic Infarct Model

BACKGROUND

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) were recently shown to be capable of electromechanical integration following direct injection into intact or recently injured guinea pig hearts, and hESC-CM transplantation in recently injured hearts correlated with improvements in contractile function and a reduction in the incidence of arrhythmias. The present study was aimed at determining the ability of hESC-CMs to integrate and modulate electrical stability following transplantation in a chronic model of cardiac injury.

METHODS AND RESULTS

At 28 days following cardiac cryoinjury, guinea pigs underwent intracardiac injection of hESC-CMs, noncardiac hESC derivatives (non-CMs), or vehicle. Histology confirmed partial remuscularization of the infarct zone in hESC-CM recipients while non-CM recipients showed heterogeneous xenografts. The 3 experimental groups showed no significant difference in the left ventricular dimensions or fractional shortening by echocardiography or in the incidence of spontaneous arrhythmias by telemetric monitoring. Although recipients of hESC-CMs and vehicle showed a similar incidence of arrhythmias induced by programmed electrical stimulation at 4 weeks posttransplantation, non-CM recipients proved to be highly inducible, with a ∼3-fold greater incidence of induced arrhythmias. In parallel studies, we investigated the ability of hESC-CMs to couple with host myocardium in chronically injured hearts by the intravital imaging of hESC-CM grafts that stably expressed a fluorescent reporter of graft activation, the genetically encoded calcium sensor GCaMP3. In this work, we found that only ∼38% (5 of 13) of recipients of GCaMP3+ hESC-CMs showed fluorescent transients that were coupled to the host electrocardiogram.

CONCLUSIONS

Human embryonic stem cell-derived cardiomyocytes engraft in chronically injured hearts without increasing the incidence of arrhythmias, but their electromechanical integration is more limited than previously reported following their transplantation in a subacute injury model. Moreover, non-CM grafts may promote arrhythmias under certain conditions, a finding that underscores the need for input preparations of high cardiac purity.

Foxl1-deficient mice exhibit aberrant epithelial cell positioning resulting from dysregulated EphB/EphrinB expression in the small intestine

The winged helix transcription factor Foxl1, expressed in the gut mesenchyme, regulates epithelial cell proliferation and differentiation through the Wnt/beta-catenin pathway. To better understand the role of Foxl1 in epithelial morphogenesis, we examined the tissue structure and positioning of epithelial cells in the small intestine of Foxl1-deficient mice. The small intestine of Foxl1-deficient mice manifested aberrant crypt structure, including widely distributed Paneth cells, which coincided with the ectopic and increased expression of EphB2 and EphB3, which are key regulators of epithelial cell positioning. Furthermore, real-time quantitative PCR indicated that a subset of Wnt family genes was highly expressed in the gut mesenchyme of Foxl1-deficient mice compared with that of wild-type mice. Such an increase in Wnt expression was remarkable in the mesenchyme, where the aberrant Paneth cell positioning was observed by in situ hybridization. Foxl1 plays an important role in the maintenance of crypt architecture and epithelial cell positioning through the mesenchymal-epithelial interaction in the small intestine. This interaction is essential for the normal regulation of the Wnt/beta-catenin pathway and the subsequent EphB/EphrinB expression.

Ruptured Achilles tendons show increased lectin stainability

PURPOSE

To ascertain whether lectins could be a useful tool for investigation of the extracellular matrix of degenerated and normal tendons.

METHODS

Hematoxylin-eosin-stained slides were assessed blindly using a semiquantitative grading scale for fiber structure, fiber arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, hyalinization, and glycosaminoglycan, with a pathology score giving up to three marks per each of the above variables, with 0 being normal and 3 being maximally abnormal. For lectin staining with Aleuria aurantia, Canavalia ensiformis, Galanthus nivalis, Phaseolus vulgaris, Arachis hypogea, Sambucus nigra, and Triticum vulgaris, assessment of staining on a scale from 0 (no staining) to 5 (strong staining) was performed blindly.

RESULTS

The mean pathology sum score of ruptured tendons (N = 14; average age 46.5 yr, range 29-61) was significantly greater than the mean pathology score of the control tendons of Achilles tendons from individuals with no known tendon pathology (N = 16; average age 62.5 yr, range 49-73) (pathology score: 18.5 +/- 3.2 vs 6.1 +/- 2.3). Four of the seven lectins used exhibited significantly positive results.

CONCLUSIONS

Ruptured tendons were histologically significantly more degenerated than control tendons. Ruptured tendons showed different lectin staining properties than nonruptured ones. This difference may have resulted from posttranslational changes in the extracellular matrix producing alterations in the biochemistry of the tendon, which might interfere with the interaction with the lateral sugar residues of the collagen molecules or cause steric blockade.

Light and electron microscopic demonstration of wheat germ agglutinin binding in the pericellular matrix of rat mandibular condylar cartilage

Binding of wheat germ agglutinin to rat mandibular condylar cartilage was investigated with the avidin-biotin peroxidase complex. Binding sites were observed in the pericellular matrix of the hypertrophic cell zone. Two distinct patterns were identified: one showed binding to the pericellular matrix without apparent contour; in the other binding was confined to the matrix but with conspicuous condensation forming a pericellular rim. The first binding pattern was seen particularly in the upper part of the hypertrophic cell zone adjoining the mature cell zone; the second was localized in the lower part of this zone adjacent to the site of endochondral calcification. The binding sites in the pericellular matrix are assumed to be NANA and/or GlcNAc in view of the sugar specificity of this lectin. The presence of these binding sites in this region may be due to a structural alteration or modification of proteoglycans in the course of preparation for endochondral calcification.

Lectin binding pattern in the embryonal and early fetal human vertebral column

Paraffin sections from vertebral columns of ten human embryos and fetuses ranging from stage 16 to the 12th week were stained with the FITC-coupled lectins PNA, RCA I, Con A and WGA in order to investigate changes in carbohydrate-binding sites during vertebral development. PNA revealed a specific binding site in the vertebral body blastema in the precartilaginous stage of development. Beginning with the 25-mm CRL embryo, PNA-binding sites occurred in the developing fibrous annulus and the inner zone of the intervertebral discs. The first binding sites for RCA I were seen in the extracellular matrix of vertebral bodies during the cartilaginous stage of vertebral development. During early ossification of the vertebrae, staining for RCA I-binding sites in the cytoplasm of the chondrocytes and the area around the future cartilaginous end-plates was observed. Con A bound to the chondrocyte cytoplasm, and also very strongly to notochordal cells in all developmental stages examined. WGA-binding sites appeared simultaneously with cartilage formation. Connective tissue components, e.g. ligaments, were diffusely stained by WGA. Also this lectin showed an affinity for vertebral body chondrocytes. We discuss the biochemical aspects of these lectin-binding sites, and their possible roles in the differentiation process of the human vertebral column. The results of this first lectin histochemical study on human vertebral development are compared with related results in other species.

Specific binding of peanut agglutinin and soybean agglutinin to chondroitinase ABC-digested cartilage proteoglycans: histochemical, ultrastructural cytochemical, and biochemical characterization

The binding of peanut agglutinin (PNA) and soybean agglutinin (SBA) to cartilage proteoglycans was investigated by histochemical, ultrastructural cytochemical, and biochemical methods. Following aldehyde fixation, specimens of rat epiphyseal cartilage were examined by horseradish peroxidase-labelled lectin cytochemistry with and without prior digestion in chondroitinase ABC. At the light microscope level neither PNA nor SBA exhibited any affinity for cartilage matrix, but became strongly bound following chondroitinase treatment. Similarly, at the ultrastructural level, extracellular matrix granules, presumed to be proteoglycan monomer(s), lacked PNA affinity in undigested specimens, and stained very weakly with SBA. Both PNA and SBA weakly to moderately stained the trans cisternae of the Golgi-flattened cisternae in chondrocytes. The chondrocyte plasmalemma lacked PNA staining, but reacted weakly with SBA. Following chondroitinase digestion, PNA and SBA stained matrix granules, and the cell surface of chondrocytes intensely, whereas the Golgi trans cisternae, the Golgi-derived vacuoles, and multivesicular bodies demonstrated weak to moderate reactivity. Proteoglycan aggregates purified from rat chondrosarcoma and bovine nasal cartilage bound PNA and SBA avidly after digestion with chondroitinase. Undigested proteoglycans lacked affinity for PNA and reacted very weakly with SBA. These results indicate that both PNA and SBA specifically react with chondroitinase-modified oligosaccharide(s) bound to core proteins of cartilage proteoglycans. This provided a specific histochemical and ultrastructural cytochemical procedure for localizing chondroitin sulphate-containing proteoglycans.