Biology subjects

Bertazzo, S.

Publications and source records attributed to Bertazzo, S..

11 recordsLinked to original sources

bioRxiv2026

Biomineralization from platelet δ-granules as the origin of cardiovascular calcification in humans and other animals.

Cardiovascular calcification is present in practically all cardiac diseases, which are the top killers in the world today1, and is particularly associated with atherosclerosis2, aortic stenosis3 and rheumatic fever4. If not the direct cause of death, calcification contributes considerably to complications that can lead to heart failure5. Nonetheless, the origins and mechanisms of cardiovascular calcification are still strongly debated3,6-12. Just over a decade ago, it has been reported that nano and micron-sized calcified spherical particles, formed from a single crystal of magnesium-containing calcium phosphate, were the first calcified structure that could be detected in cardiovascular tissue13. These particles were found even before any sign of cardiac disease was present and were present in all stages of cardiac diseases13. The ubiquity of these particles suggests their importance for the origins and development of cardiovascular calcific diseases. Here, we show that these particles originate from platelet {delta}-granules and are present in mammals, birds and lizards. Based on our results, we suggest a new mechanism for the origins of these particles, complementing existing models of cardiovascular calcification7,14, and bringing a new, early, and hitherto unaccounted key event in the process of cardiovascular calcification. This new mechanism model, along with a better understanding of the early stages of cardiovascular calcification, could open the path for the development of pharmacological prevention and treatment solutions for several cardiac diseases.

pathology↗

bioRxiv2024

Density-Dependent Colour Scanning Electron Microscopy (DDC-SEM). Applications in the study of calcified tissues and visual impact.

Scanning Electron Microscopy (SEM) is widely used as a technique for materials characterization. It has also been successfully applied to the imaging of biological samples, providing invaluable insights into the topography, morphology and composition of biological structures. A particular method combining different SEM detectors, named Density-Dependent Coloured SEM (DDC-SEM), has proven to be most useful for the identification and visualization of minerals in soft tissues. The method consists of a manipulation of original greyscale SEM images to produce coloured images that provide both topography and density information for samples with components of different densities. Here we provide a discussion on how to use DDC-SEM to aid the visualization and intuitive understanding of pathological calcification. This method has become popular not only for its scientific improvement of conventional SEM greyscale images, but also for its aesthetical merits. Lay summaryScanning Electron Microscopes (SEM) are widely used tools for examining biological materials such as human tissue. Like other electron microscopes, it only produces images in greyscale. SEM has been useful, for instance, in improving our understanding of calcific diseases. These diseases involve the build-up of mineral in the bodys soft tissues, and frequently affect the heart, kidneys, or eyes. This work provides a discussion on using a SEM technique known as Density-Dependent Colour Scanning Electron Microscopy (DDC-SEM), which enhances SEM images through scanning the same area with different detectors, assigning a unique colour to each detectors output, and then overlaying these images.

scientific communication and education↗

bioRxiv2023

Multiscale Multimodal Characterization and Simulation of Structural Alterations in Failed Bioprosthetic Heart Valves

Calcific degeneration is the most frequent type of heart valve failure, with rising incidence due to the ageing population. The gold standard treatment to date is valve replacement. Unfortunately, calcification oftentimes re-occurs in bioprosthetic substitutes, with the governing processes remaining poorly understood. Here, we present a multiscale, multimodal analysis of disturbances and extensive mineralisation of the collagen network in failed bioprosthetic bovine pericardium valve explants with full histoanatomical context. In addition to highly abundant mineralized collagen fibres and fibrils, calcified micron-sized particles previously discovered in native valves were also prevalent on the aortic as well as the ventricular surface of bioprosthetic valves. The two mineral types (fibers and particles) were detectable even in early-stage mineralisation, prior to any macroscopic calcification. Based on multiscale multimodal characterisation and high-fidelity simulations, we demonstrate that mineral occurrence coincides with regions exposed to high haemodynamic and biomechanical indicators. These insights obtained by multiscale analysis of failed bioprosthetic valves may serve as groundwork for the evidence-based development of more durable alternatives. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/529530v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@c7e0b5org.highwire.dtl.DTLVardef@71bdbdorg.highwire.dtl.DTLVardef@15fdc23org.highwire.dtl.DTLVardef@6dbd1c_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

68Ga-Bisphosphonates for the Imaging of Extraosseous Calcification by Positron Emission Tomography

Radiolabelled bisphosphonates (BPs) and [18F]NaF (18F-fluoride) are the two types of radiotracers available to image calcium mineral in vivo (e.g. bone), yet only [18F]NaF has been widely explored for the non-invasive molecular imaging of extraosseous calcification (EC) using the highly sensitive nuclear imaging technique positron emission tomography (PET). These two radiotracers bind calcium mineral deposits via different mechanisms, with BPs chelating to calcium ions and thus being non-selective, and [18F]NaF being selective for hydroxyapatite (HAp) which is the main component of bone mineral. Taking into account that the composition of EC has been reported to include a diverse range of non-HAp calcium minerals, we hypothesised that BPs may be more sensitive for imaging EC due to their ability to bind to both HAp and non-HAp deposits. To test this hypothesis, we report a comparison between the 68Ga-labelled BP tracer [68Ga]Ga-THP-Pam and [18F]NaF for PET imaging in a rat model of EC that develops macro- and microcalcifications in several organs. The presence of macrocalcifications was identified using preclinical computed tomography (CT) and microcalcifications were identified using CT-based 3D X-ray histology (XRH) on isolated organs ex vivo. The morphological and mineral analysis of individual calcified deposits was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The PET imaging and ex vivo analysis results demonstrated that while both radiotracers behave similarly for bone imaging, the BP-based radiotracer [68Ga]Ga-THP-Pam was able to detect EC more sensitively in several organs in which the mineral composition departs from that of HAp. We conclude that BP-based PET radiotracers such as [68Ga]Ga-THP-Pam have a particular advantage for the sensitive imaging and early detection of EC by being able to detect a wider array of relevant calcium minerals in vivo than [18F]NaF, and should be evaluated clinically for this purpose.

pharmacology and toxicology↗

bioRxiv2022

Alizarin Red fluorescence imaging for nano calcification

The formation of calcium phosphate (calcification) has been observed in a variety of healthy and diseased tissues and contributes to a wide range of pathologies. In physiological and pathological mechanisms, calcification begins at the nano scale and then develops into structures that range from a few micrometres to several centimetres. Fluorescence microscopy can be an efficient way to visualise such early calcification and its interaction with cells and proteins. The limited shelf life and high cost of commercial dyes for staining calcification, however, can be problematic when using this imaging method. Here, we aim to evaluate the effectiveness and stability of Alizarin Red (AR) as a fluorescent staining agent for nano and micro calcified structures. Our results show that AR staining for nano and micro calcified structures is a simple, reliable, effective, and quite inexpensive method to visualize calcification at the nano and micro scale in biological samples.

pathology↗

bioRxiv2022

Density-Dependent Color Scanning Electron Microscopy (DDC-SEM) for calcified tissue and pathological calcification.

Scanning electron microscopy (SEM) is widely used for materials characterization. It has also been successfully applied to the imaging of biological samples, providing invaluable insights into the topography, morphology and composition of biological structures, including pathological minerals, in diseases affecting cardiovascular, kidney and ocular tissues. Here we provide a comprehensive and detailed guide on how to use colored SEM to aid the visualization and characterization of pathological calcification, and identify the effects of different sample preparation protocols for the visualisation of these minerals.

pathology↗

bioRxiv2022

Time-dependent Role of Bisphosphonates on Atherosclerotic Plaque Calcification

Atherosclerotic plaque calcification directly contributes to the leading cause of morbidity and mortality by affecting the plaque vulnerability and rupture risk. Small microcalcifications can increase plaque stress and promote rupture, whereas large calcifications can stabilize plaques. Drugs that target bone mineralization may lead to unintended consequences on ectopic plaque calcification and cardiovascular outcomes. Bisphosphonates, common anti-osteoporotic agents, elicited unexpected cardiovascular events in clinical trials. Here, we investigated the role of bisphosphonates treatment and timing on the disruption or promotion of vascular calcification and bone mineral in a mouse model of atherosclerosis. We started the bisphosphonate treatment either before plaque formation, at early plaque formation times associated with the onset of calcification, or at late stages of plaque development. Our data indicate that long term bisphosphonate treatment (beginning prior to plaque development) leads to higher levels of plaque calcification, with a narrower mineral size distribution. When given later in plaque development, we measured a wider distribution of mineral size. These morphological alterations may associate with higher risk of plaque rupture by creating stress foci. Yet, bone mineral density positively correlated with the duration of bisphosphonate treatment.

bioengineering↗

bioRxiv2021

Epidermal Growth Factor Receptor Inhibition Prevents Caveolin-1-dependent Calcifying Extracellular Vesicle Biogenesis

Chronic kidney disease (CKD) increases the risk of cardiovascular disease, including vascular calcification, leading to higher mortality. Release of calcifying extracellular vesicles (EVs) by vascular smooth muscle cells (VSMCs) promotes the ectopic mineralization of vessel walls. Caveolin-1 (CAV1) protein plays a key role in genesis of calcifying EVs in VSMCs. Epidermal growth factor receptor (EGFR) co-localizes with and influences the intracellular trafficking of CAV1. Using a diet-induced mouse model of CKD, we measured serum EGFR and assessed the potential of EGFR inhibition to prevent vascular calcification. Mice with CKD developed widespread vascular calcification, which associated with increased serum levels of EGFR. We computationally analyzed 7651 individuals in the Multi-Ethnic Study of Atherosclerosis (MESA) and Framingham cohorts to assess potential correlations between coronary artery calcium and single nucleotide polymorphisms (SNPs) associated with elevated serum levels of EGFR. Individuals in the MESA and Framingham cohorts with SNPs associated with increased serum EGFR exhibit elevated coronary artery calcium. In both the CKD mice and human VSMC culture, EGFR inhibition significantly reduced vascular calcification by mitigating the release of CAV1-positive calcifying EVs. EGFR inhibition also increased bone mineral density in CKD mice. Given that EGFR inhibitors exhibit clinical safety and efficacy in other pathologies, the current data suggest that EGFR may be an ideal target to prevent pathological vascular calcification.

pathology↗

bioRxiv2020

Association of cellular and subcellular calcification with phosphorylated tau in the brains of Alzheimer's disease patients.

Brain calcification (calcium phosphate mineral formation) has been reported in the past 100 years in the brains of Alzheimers disease (AD) patients. However, the association between calcification and AD, the triggers for calcification, and its role within the disease are not clear. On the other hand, hyperphosphorylated tau protein (pTau) tangles have been widely studied and recognized as an essential factor in developing AD. In this work, calcification in the brains of AD patients is characterized by advanced electron microscopy and fluorescence microscopy. Results are then compared to samples from cognitively healthy, age-matched donors, and the colocalization of calcification and pTau is investigated. Here, we show that AD patients brains present microcalcification associated with the neural cell nuclei and cell projections, and that these are strongly related to the presence of pTau. The link between microcalcification and pTau suggests a potential new mechanism of brain cell damage. Together with the formation of amyloid plaques and neurofibrillary tangles, microcalcification in neuronal cells adds to a better understanding of the pathology of AD. Finally, the presence of microcalcification in the neuronal cells of AD patients may assist in AD diagnosis, and may open new avenues for developing intervention strategies based on inhibition of calcification.

pathology↗

bioRxiv2020

Invasive breast tumors are characterized by the presence of crystalline nanoparticles

The presence of calcifications on mammograms is a widely used diagnostic marker for breast cancer. While the clinicopathological analysis of breast tissue is well-developed, an in-depth characterisation of the properties of calcifications at the micro and nano scale remained elusive. In this work, we use nano-analytical methods to investigate the calcification present in healthy breast tissue, as well as in benign and malignant breast tumour tissue biopsies. While polycrystalline apatite with lower crystallinity can be found in all breast tissue samples, we show that magnesium-containing nano and micro spherical particles are found only in malignant invasive breast cancers. These particles concentration increases with cancer progression. The discovery of these spherical particles provides new insights into the characteristics of breast calcification associated with malignant tumours and opens new research pathways to a better understanding of breast tumours and their microenvironment in general.

cancer biology↗

bioRxiv2019

Electron microscopy characterization of minerals formed in vitro by human bone cells and vascular smooth muscle cells

Soft tissue mineralization has been found to be a major component of diseases such as aortic valve stenosis and rheumatic heart disease. Cardiovascular mineralization has been suggested to follow mechanisms similar to those of bone formation with several cell culture models been developed over the years to provide mechanistic insights. These cell models have been characterized by a wide range of biochemical and molecular methods, which identified the presence of osteogenic markers and bone-like cells. However, there is a surprisingly small number of studies where the mineral formed in these cell culture models has been characterized by physico-chemical methods, and even fewer studies have compared this mineral to the one produced by bone cells in cultures. Here we investigated the morphology and composition of the minerals formed in cell cultures of vascular smooth muscle cells and bone cells. Electron microscopy and traditional cell mineralization assays were applied, revealing that vascular cells are indeed able to form calcified nodules of elemental composition similar to bone, however with different morphology. Comparison of morphologies of the two minerals to that found in cardiovascular tissue shows that some of tissue calcification resembles the calcified fibers produced by bone cells in vitro. These results suggest that the characterization of the mineral is of utmost importance and its morphology and chemical properties can contribute an important piece of information in the comprehensive analysis of soft tissue mineralization mechanisms, both in in vitro cell culture as well as in clinical samples.

pathology↗