Pathological biominerals: Raman and infrared studies of bioapatite deposits in human heart valves

Spectroscopic characterization of calcium phosphate precipitated under human eye conditions: An in vitro study

Calcification is a well-known process of calcium phosphate mineralization observed in intraocular lenses. Despite the many works conducted in this field, there is no strict explanation of the mechanisms of this process. In order to better understand the phenomenon, i.e., the mechanisms and structural conditions that promote calcification, any research observations should be conducted under conditions that best reflect those of the human eye. Taking into account the specific anatomy and physicochemical conditions of the human eye, the problem under discussion becomes difficult to solve in vitro. In the present study, calcium phosphates formed under conditions similar to those in the human eye were characterized using SEM/EDS and infrared spectroscopy. Conducted study showed the formation of white spherical precipitates, which are unstable when extracted from solution. Such precipitates were characteristic of solutions containing 1.5-3.0 mM² of solutes. Elemental analysis showed a Ca/P ratio of 1.64-1.65, which is similar to the ratio for hydroxyapatite (1.67). Chemical structure analysis revealed the presence of broad bending and stretching bands at 475-830 cm^-1 and 880-1250 cm^-1, respectively, which are characteristic of PO₄^3- groups in apatite calcium phosphates. In further analysis involving numerical fitting the bands corresponding to apatitic PO₄^3- and indicating the presence of calcium phosphates hydration were found. The results allow the selection of immersion media for further studies involving the incubation of hydrogel intraocular lenses.

Biomineralogical signatures of breast microcalcifications

Microcalcifications, primarily biogenic apatite, occur in cancerous and benign breast pathologies and are key mammographic indicators. Outside the clinic, numerous microcalcification compositional metrics (e.g., carbonate and metal content) are linked to malignancy, yet microcalcification formation is dependent on microenvironmental conditions, which are notoriously heterogeneous in breast cancer. We interrogate multiscale heterogeneity in 93 calcifications from 21 breast cancer patients using an omics-inspired approach: For each microcalcification, we define a "biomineralogical signature" combining metrics derived from Raman microscopy and energy-dispersive spectroscopy. We observe that (i) calcifications cluster into physiologically relevant groups reflecting tissue type and local malignancy; (ii) carbonate content exhibits substantial intratumor heterogeneity; (iii) trace metals including zinc, iron, and aluminum are enhanced in malignant-localized calcifications; and (iv) the lipid-to-protein ratio within calcifications is lower in patients with poor composite outcome, suggesting that there is potential clinical value in expanding research on calcification diagnostic metrics to include "mineral-entrapped" organic matrix.

Models and Techniques to Study Aortic Valve Calcification in Vitro, ex Vivo and in Vivo. An Overview

Aortic valve stenosis secondary to aortic valve calcification is the most common valve disease in the Western world. Calcification is a result of pathological proliferation and osteogenic differentiation of resident valve interstitial cells. To develop non-surgical treatments, the molecular and cellular mechanisms of pathological calcification must be revealed. In the current overview, we present methods for evaluation of calcification in different ex vivo, in vitro and in vivo situations including imaging in patients. The latter include echocardiography, scanning with computed tomography and magnetic resonance imaging. Particular emphasis is on translational studies of calcific aortic valve stenosis with a special focus on cell culture using human primary cell cultures. Such models are widely used and suitable for screening of drugs against calcification. Animal models are presented, but there is no animal model that faithfully mimics human calcific aortic valve disease. A model of experimentally induced calcification in whole porcine aortic valve leaflets ex vivo is also included. Finally, miscellaneous methods and aspects of aortic valve calcification, such as, for instance, biomarkers are presented.

Evaluation of the influence of diet supplementation with conjugated linoleic acid isomers on elemental composition in the cardio-oncological nutritional programming rat' model

BACKGROUND

The 'developmental origin of health and disease' (DOHaD) hypothesis assumes that due to the action of some stimuli during fetal life the long-term physiological changes occurs and may affects the risk of various diseases. The main aim of this study was to assess impact of supplementation of maternal' and early postnatal diet with conjugated linoleic acids (CLA) isomers on selected elements content in hearts of their female offspring with chemically induced breast cancer.

METHODS

Elemental composition was determined by quadrupole mass spectrometer with inductively coupled plasma ionization (ICP-MS).

RESULTS

The effect of maternal' diet on the elements content was more pronounced than the progeny diet modifications. Significant correlations among determined elements, especially macroelements, and lipidomic parameters, in the experimental factors dependent manner were observed. It can be concluded that supplementation of maternal and progeny diets with CLA isomers may significantly influence the contents of both macro- and microelements in cardiac tissue of newborns.

CONCLUSION

Our results also indicate, that dynamic and intricate balance among various elements in body may be affected by the lipid dietary supplements also in the pathological state. Utility of cardio-oncological approach in developmental programming study was confirmed.

Cancer Influences the Elemental Composition of the Myocardium More Strongly than Conjugated Linoleic Acids-Chemometric Approach to Cardio-Oncological Studies

The aim of the study was to verify in a cardio-oncological model experiment if conjugated linoleic acids (CLA) fed to rats with mammary tumors affect the content of selected macro- and microelements in their myocardium. The diet of Sprague-Dawley females was supplemented either with CLA isomers or with safflower oil. In hearts of rats suffering from breast cancer, selected elements were analyzed with a quadrupole mass spectrometer with inductively coupled plasma ionization (ICP-MS). In order to better understand the data trends, cluster analysis, principal component analysis and linear discriminant analysis were applied. Mammary tumors influenced macro- and microelements content in the myocardium to a greater extent than applied diet supplementation. Significant influences of diet (p = 0.0192), mammary tumors (p = 0.0200) and interactions of both factors (p = 0.0151) were documented in terms of Fe content. CLA significantly decreased the contents of Cu and Mn (p = 0.0158 and p = 0.0265, respectively). The level of Ni was significantly higher (p = 0.0073), which was more pronounced in groups supplemented with CLA. The obtained results confirmed antioxidant properties of CLA and the relationship with Se deposition. Chemometric techniques distinctly showed that the coexisting pathological process induced differences to the greater extent than diet supplementation in the elemental content in the myocardium, which may impinge on cardiac tissue's susceptibility to injuries.

A Comparative Study of Pathological Nanomineral Aggregates with Distinct Morphology in Human Aortic Atherosclerotic Plaques

Calcification exists in atherosclerotic plaques in the form of nanomineral aggregates and is closely related to the development of atherosclerosis. Spheroidal and massive calcification are two major types of calcification found in atherosclerotic tissue. However, the exact difference between these two types of calcification is still not clear. Samples composed entirely of spheroidal calcifications and massive calcifications were isolated from aortic atherosclerotic plaques and tested using both bulk and microscopic analysis techniques. Scanning electron microscopy and transmission electron microscopy showed that spheroidal calcifications had a core-shell structure. Massive calcifications were composed of randomly arranged nanocrystals. Synchrotron radiation X-ray diffraction, Raman spectroscopy and selected area electron diffraction showed amorphous calcium phosphate, whitlockite and carbonate hydroxyapatite all existing in spheroidal calcification, while massive calcification only consisted of carbonate hydroxyapatite. We conclude that amorphous calcium phosphate may act as a precursor phase of spheroidal calcifications that eventually transforms into a crystalline phase, while whitlockite in lesions could aggravate the progression of atherosclerosis.

Lambl's excrescence in transcatheter aortic valve implantation: prevalence and risk of embolic events

BACKGROUND

The role of aortic valve Lambl's excrescence (LEs) in determining ischemic events has not been well clarified, but they can represent a potential embolic source during procedures with catheter/device manipulation through the aortic valve. Aim of our study was to assess the prevalence of LEs and the rate of embolism in patients with aortic valve stenosis scheduled for transcatheter aortic valve implantation (TAVI).

METHODS

Our population was divided into two groups, named LEs and no-LEs. In each group, the rate of cerebral embolic events was assessed, as well as other TAVI-related complications.

RESULTS

In our study population 28 patients (37%) had aortic strands and 48 (63%) did not have them. A cerebral protection device was used in four patients of LEs group (14% vs. 0, P=0.03). The mean procedural time was similar in the two groups: 50±19 and 55±26 minutes (P=0.38) in LEs and no-LEs groups, respectively. The device success was achieved in 96% of LEs and 88% of no-LEs patients (P=0.37). Two patients of no-LEs group died during the procedure. Major complications were observed in both groups without any significant differences. Only one case of stroke occurred in the population without LEs (0 LEs vs. 2% no-LEs, 0.78). No cases of peripheral embolism were observed.

CONCLUSIONS

In our population the observation of LEs is not uncommon. Despite the presumed high risk of embolism, we have not observed an increase in the rate of cerebral ischemic events or other TAVI related complications in patients with LEs.

Differences in mineral composition and morphology between men and women in aortic valve calcification

Aortic valve calcification leads to the deposition of calcium phosphate minerals in the extracellular matrix of the aortic valve leaflets. The mineral deposits can severely narrow the opening of the aortic valve, leading to aortic stenosis. There are no therapies to halt or slow down disease progression and the mechanisms governing aortic valve calcification are still poorly understood. Recently, several studies have shown that for the same aortic stenosis severity, women present significantly lower calcification loads than men. The cause of this sex-related difference is unknown. To understand this difference, we analyzed mineral deposits from surgically excised calcified human aortic valves with different material characterization techniques. We find profound differences in mineral composition and morphology between sexes, which strongly suggest that minerals form slower in women than in men and follow a different mineralization pathway. This finding paves the way for new approaches specifically geared towards men or women in the diagnosis and treatment of aortic valve calcification. STATEMENT OF SIGNIFICANCE: Aortic valve calcification is a health disorder with increasing prevalence and high morbidity and mortality. Currently there is no approved effective treatment; the only available therapeutic option is invasive valve replacement, to which not all patients are suited. The main reason for such lack of treatment options is our lack of understanding of the calcification mechanism. In this study, we show profound differences in mineral composition and morphology between sexes, suggesting that aortic valve calcification follows different mineralization pathways in men and women. These findings pave the way for new approaches specifically geared towards men or women in the diagnosis and treatment of aortic valve calcification.

Development of calcific aortic valve disease: Do we know enough for new clinical trials?

Calcific aortic valve disease (CAVD), previously thought to represent a passive degeneration of the valvular extracellular matrix (VECM), is now regarded as an intricate multistage disorder with sequential yet intertangled and interacting underlying processes. Endothelial dysfunction and injury, initiated by disturbed blood flow and metabolic disorders, lead to the deposition of low-density lipoprotein cholesterol in the VECM further provoking macrophage infiltration, oxidative stress, and release of pro-inflammatory cytokines. Such changes in the valvular homeostasis induce differentiation of normally quiescent valvular interstitial cells (VICs) into synthetically active myofibroblasts producing excessive quantities of the VECM and proteins responsible for its remodeling. As a result of constantly ongoing degradation and re-deposition, VECM becomes disorganised and rigid, additionally potentiating myofibroblastic differentiation of VICs and worsening adaptation of the valve to the blood flow. Moreover, disrupted and excessively vascularised VECM is susceptible to the dystrophic calcification caused by calcium and phosphate precipitating on damaged collagen fibers and concurrently accompanied by osteogenic differentiation of VICs. Being combined, passive calcification and biomineralisation synergistically induce ossification of the aortic valve ultimately resulting in its mechanical incompetence requiring surgical replacement. Unfortunately, multiple attempts have failed to find an efficient conservative treatment of CAVD; however, therapeutic regimens and clinical settings have also been far from the optimal. In this review, we focused on interactions and transitions between aforementioned mechanisms demarcating ascending stages of CAVD, suggesting a predisposing condition (bicuspid aortic valve) and drug combination (lipid-lowering drugs combined with angiotensin II antagonists and cytokine inhibitors) for the further testing in both preclinical and clinical trials.

Treatment with XAV-939 prevents in vitro calcification of human valvular interstitial cells

The development of a substance or inhibitor-based treatment strategy for the prevention of aortic valve stenosis is a challenge and a main focus of medical research in this area. One strategy may be to use the tankyrase inhibitor XAV-939, which leads to Axin stabilisation and subsequent destruction of the β-catenin complex and dephosphorylation of β-catenin. The dephosphorylated active form of β-catenin (non-phospho-β-catenin) then promotes nuclear transcription that leads to osteogenesis. The aims of the present study were to develop an experimental system for inducing in vitro calcification of human aortic valvular interstitial cells (VICs) to investigate the potential anti-calcific effect of XAV-939 and to analyse expression of the Wnt signalling proteins and Sox9, a chondrogenesis regulator, in this model. Calcification of human VIC cultures was induced by cultivation in an osteogenic medium and the effect of co-incubation with 1μM XAV-939 was monitored. Calcification was quantified when mineral deposits were visible in culture and was histologically verified by von Kossa or Alizarin red staining and by IR-spectroscopy. Protein expression of alkaline phosphatase, Axin, β-catenin and Sox9 were quantified by western blotting. In 58% of the VIC preparations, calcification was induced in an osteogenic culture medium and was accompanied by upregulation of alkaline phosphatase. The calcification induction was prevented by the XAV-939 co-treatment and the alkaline phosphatase upregulation was suppressed. As expected, Axin was upregulated, but the levels of active non-phospho-β-catenin were also enhanced. Sox9 was induced during XAV-939 treatment but apparently not as a result of downregulation of β-catenin signalling. XAV-939 was therefore able to prevent calcification of human VIC cultures, and XAV-939 treatment was accompanied by upregulation of active non-phospho-β-catenin. Although XAV-939 does not downregulate active β-catenin, treatment with XAV-939 results in Sox9 upregulation that may prevent the calcification process.

Structural and crystal-chemical characteristics of the apatite deposits from human aortic walls

Thermal behavior of biological apatite is the object of several studies. Crystal size, carbonate content, phase composition, and other parameters change during annealing up to 900 °C in biological minerals with apatite structure. The way these parameters change reflects the specific properties of the initial bioapatite. This work presents data on thermal transformations of pathological bioapatite from the human cardiovascular system, namely aortic wall deposits. Some minor elements, foreign to calcium hydroxyapatite (e.g., Na and Mg), can be both incorporated in the apatite structure and localized in the surface layers of crystals, modifying functions of the mineral. A new approach was proposed to determine the predominant location of minor elements, such as Mg, Na, and K, in the mineral of pathological deposits. Mg and Na in pathological apatite can be in both structurally bound (substituting calcium in lattice) and labile (localized on the crystal surface) states, while K is not able to join the apatite structure in significant amount or be chemically bound to it. This approach, based on atomic spectrometry, can be used effectively in combination with a set of traditional techniques, such as like EDS, IRS, and XRD.

Deregulation of Notch1 pathway and circulating endothelial progenitor cell (EPC) number in patients with bicuspid aortic valve with and without ascending aorta aneurysm

Bicuspid aortic valve (BAV) is frequently associated with the development of ascending aortic aneurysm, even if the underlying mechanisms remain to be clarified. Here, we investigated if a deregulation of Notch1 signaling pathway and endothelial progenitor cells (EPCs) number is associated with BAV disease and an early ascending aortic aneurysm (AAA) onset. For this purpose, 70 subjects with BAV (M/F 50/20; mean age: 58.8 ± 14.8 years) and 70 subjects with tricuspid aortic valve (TAV) (M/F 35/35; mean age: 69.1 ± 12.8 years) and AAA complicated or not, were included. Interestingly, patients with AAA showed a significant increase in circulating Notch1 levels and EPC number than subjects without AAA. However, circulating Notch1 levels and EPC number were significantly lower in BAV subjects than TAV patients either in the presence or absence of AAA. Finally, Notch pathway was activated to a greater extent in aortic aneurysmatic portions with respect to healthy aortic fragments in both BAV and TAV patients. However, the expression of genes encoding components and ligands of Notch pathway in aortic tissues was significantly lower in BAV than TAV subjects. Our study demonstrates that BAV subjects are characterized by a significant decrease in both tissue and circulating levels of Notch pathway, and in blood EPC number than TAV patients, either in presence or absence of AAA disease.

Crystallinity of hydroxyapatite drives myofibroblastic activation and calcification in aortic valves

Calcific aortic valve disease (CAVD) is an inexorably degenerative pathology characterized by progressive calcific lesion formation on the valve leaflets. The interaction of valvular cells in advanced lesion environments is not well understood yet highly relevant as clinically detectable CAVD exhibits calcifications composed of non-stoichiometric hydroxyapatite (HA). In this study, Fourier transform infrared spectroscopic imaging was used to spatially analyze mineral properties as a function of disease progression. Crystallinity (size and perfection) increased with increased valve calcification. To study the relationship between crystallinity and cellular behavior in CAVD, valve cells were seeded into 3D mineral-rich collagen gels containing synthetic HA particles, which had varying crystallinities. Lower crystallinity HA drove myofibroblastic activation in both valve interstitial and endothelial cells, as well as osteoblastic differentiation in interstitial cells. Additionally, calcium accumulation within gels depended on crystallinity, and apoptosis was insufficient to explain differences in HA-driven cellular activity. The protective nature of endothelial cells against interstitial cell activation and calcium accumulation was completely inhibited in the presence of less crystalline HA particles. Elucidating valve cellular behavior post-calcification is of vital importance to better predict and treat clinical pathogenesis, and mineral-containing hydrogel models provide a unique 3D platform to evaluate valve cell responses to a later stage of valve disease.

STATEMENT OF SIGNIFICANCE

We implement a 3D in vitro platform with embedded hydroxyapatite (HA) nanoparticles to investigate the interaction between valve interstitial cells, valve endothelial cells, and a mineral-rich extracellular environment. HA nanoparticles were synthesized based on analysis of the mineral properties of calcific regions of diseased human aortic valves. Our findings indicate that crystallinity of HA drives activation and differentiation in interstitial and endothelial cells. We also show that a mineralized environment blocks endothelial protection against interstitial cell calcification. Our HA-containing hydrogel model provides a unique 3D platform to evaluate valve cell responses to a mineralized ECM. This study additionally lays the groundwork to capture the diversity of mineral properties in calcified valves, and link these properties to progression of the disease.

Multidisciplinary Approach to Understand Medial Arterial Calcification

OBJECTIVE

Vascular calcification significantly increases morbidity in life-threatening diseases, and no treatments are available because of lack of understanding of the underlying molecular mechanism. Here, we study the physicochemical details of mineral nucleation and growth in an animal model that faithfully recapitulates medial arterial calcification in humans, to understand how pathological calcification is initiated on the vascular extracellular matrix.

APPROACH AND RESULTS

MGP (matrix Gla protein) is a potent mineralization inhibitor. We study the evolution of medial calcification in MGP-deficient mice over the course of 5 weeks using a combination of material science techniques and find that mineral composition and crystallinity evolve over time and space. We show that calcium is adsorbed first and then amorphous calcium phosphate and octacalcium phosphate forms, which then transform into hydroxyapatite and carbonated apatite. These events are repeated after each nucleation event, providing a snapshot of the overall mineral evolution at each time point analyzed.

CONCLUSIONS

Our results show that an interdisciplinary approach combining animal models and materials science can provide insights into the mechanism of vascular calcification and suggest the importance of analyzing mineral phases, rather than just overall mineralization extent, to diagnose and possibly prevent disease development.

Lipoprotein(a) Induces Human Aortic Valve Interstitial Cell Calcification

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Lp(a) significantly increased alkaline phosphatase activity, phosphate and calcium content, and matrix vesicle formation and induced apoptosis and calcification of normal human aortic valve interstitial cells.

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The type of minerals induced by Lp(a) resembles that seen in calcified human aortic valves as shown by Raman spectroscopy.

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Lp(a)-induced calcification of human aortic valve interstitial cells is mediated by activation of MAPK38, GSK3β, and Wnt signaling.

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Inhibition of GSK3β and MAPK38 significantly reduced lipoprotein(a)-induced aortic valve interstitial cell calcification.

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Lp(a)is abundant in calcified aortic valves, and lipoprotein(a) immunoreactivity colocalized with that of oxidized phospholipids.

Lipoprotein(a), or Lp(a), significantly increased alkaline phosphatase activity, release of phosphate, calcium deposition, hydroxyapatite, cell apoptosis, matrix vesicle formation, and phosphorylation of signal transduction proteins; increased expression of chondro-osteogenic mediators; and decreased SOX9 and matrix Gla protein (p < 0.001). Inhibition of MAPK38 and GSK3β significantly reduced Lp(a)-induced calcification of human aortic valve interstitial cells (p < 0.001). There was abundant presence of Lp(a) and E06 immunoreactivity in diseased human aortic valves. The present study demonstrates a causal effect for Lp(a) in aortic valve calcification and suggests that interfering with the Lp(a)pathway could provide a novel therapeutic approach in the management of this debilitating disease.

Two types of bone necrosis in the Middle Triassic Pistosaurus longaevus bones: the results of integrated studies

Avascular necrosis, diagnosed on the basis of either a specific pathological modification of the articular surfaces of bone or its radiologic appearance in vertebral centra, has been recognized in many Mesozoic marine reptiles as well as in present-day marine mammals. Its presence in the zoological and paleontologic record is usually associated with decompression syndrome, a disease that affects secondarily aquatic vertebrates that could dive. Bone necrosis can also be caused by infectious processes, but it differs in appearance from decompression syndrome-associated aseptic necrosis. Herein, we report evidence of septic necrosis in the proximal articular surface of the femur of a marine reptile, Pistosaurus longaevus, from the Middle Triassic of Poland and Germany. This is the oldest recognition of septic necrosis associated with septic arthritis in the fossil record so far, and the mineralogical composition of pathologically altered bone is described herein in detail. The occurrence of septic necrosis is contrasted with decompression syndrome-associated avascular necrosis, also described in Pistosaurus longaevus bone from Middle Triassic of Germany.

Biological Niches within Human Calcified Aortic Valves: Towards Understanding of the Pathological Biomineralization Process

Despite recent advances, mineralization site, its microarchitecture, and composition in calcific heart valve remain poorly understood. A multiscale investigation, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometry (EDS), from micrometre up to nanometre, was conducted on human severely calcified aortic and mitral valves, to provide new insights into calcification process. Our aim was to evaluate the spatial relationship existing between bioapatite crystals, their local growing microenvironment, and the presence of a hierarchical architecture. Here we detected the presence of bioapatite crystals in two different mineralization sites that suggest the action of two different growth processes: a pathological crystallization process that occurs in biological niches and is ascribed to a purely physicochemical process and a matrix-mediated mineralized process in which the extracellular matrix acts as the template for a site-directed nanocrystals nucleation. Different shapes of bioapatite crystallization were observed at micrometer scale in each microenvironment but at the nanoscale level crystals appear to be made up by the same subunits.

Carotenoids co-localize with hydroxyapatite, cholesterol, and other lipids in calcified stenotic aortic valves. Ex vivo Raman maps compared to histological patterns

Unlike its application for atherosclerotic plaque analysis, Raman microspectroscopy was sporadically used to check the sole nature of bioapatite deposits in stenotic aortic valves, neglecting the involvement of accumulated lipids/lipoproteins in the calcific process. Here, Raman microspectroscopy was employed for examination of stenotic aortic valve leaflets to add information on nature and distribution of accumulated lipids and their correlation with mineralization in the light of its potential precocious diagnostic use. Cryosections from surgically explanted stenotic aortic valves (n=4) were studied matching Raman maps against specific histological patterns. Raman maps revealed the presence of phospholipids/triglycerides and cholesterol, which showed spatial overlapping with one another and Raman-identified hydroxyapatite. Moreover, the Raman patterns correlated with those displayed by both von-Kossa-calcium- and Nile-blue-stained serial cryosections. Raman analysis also provided the first identification of carotenoids, which co-localized with the identified lipid moieties. Additional fit concerned the distribution of collagen and elastin. The good correlation of Raman maps with high-affinity staining patterns proved that Raman microspectroscopy is a reliable tool in evaluating calcification degree, alteration/displacement of extracellular matrix components, and accumulation rate of different lipid forms in calcified heart valves. In addition, the novel identification of carotenoids supports the concept that valve stenosis is an atherosclerosis-like valve lesion, consistently with their previous Raman microspectroscopical identification inside atherosclerotic plaques.

Morphological and chemical study of pathological deposits in human aortic and mitral valve stenosis: a biomineralogical contribution

Aim of this study was to investigate heart valve calcification process by different biomineralogical techniques to provide morphological and chemical features of the ectopic deposit extracted from patients with severe mitral and aortic valve stenosis, to better evaluate this pathological process. Polarized light microscopy and scanning electron microscopy analyses brought to light the presence of nodular and massive mineralization forms characterized by different levels of calcification, as well as the presence of submicrometric calcified globular cluster, micrometric cavities containing disorganized tissue structures, and submillimeter pockets formed by organic fibers very similar to amyloid formations. Electron microprobe analyses showed variable concentrations of Ca and P within each deposit and the highest content of Ca and P within calcified tricuspid aortic valves, while powder X-ray diffraction analyses indicated in the nanometer range the dimension of the pathological bioapatite crystals. These findings indicated the presence of highly heterogeneous deposits within heart valve tissues and suggested a progressive maturation process with continuous changes in the composition of the valvular tissue, similar to the multistep formation process of bone tissue. Moreover the micrometric cavities represent structural stages of the valve tissue that immediately precedes the formation of heavily mineralized deposits such as bone-like nodules.

Exploring type II microcalcifications in benign and premalignant breast lesions by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)

The characteristics of type II microcalcifications in fibroadenoma (FB), atypical ductal hyperplasia (ADH), and ductal carcinoma in situ (DCIS) breast tissues has been analyzed by the fingerprint features of Raman spectroscopy. Fresh breast tissues were first handled to frozen sections and then they were measured by normal Raman spectroscopy. Due to inherently low sensitivity of Raman scattering, Au@SiO2 shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique was utilized. A total number of 71 Raman spectra and 70 SHINERS spectra were obtained from the microcalcifications in benign and premalignant breast tissues. Principal component analysis (PCA) was used to distinguish the type II microcalcifications between these tissues. This is the first time to detect type II microcalcifications in premalignant (ADH and DCIS) breast tissue frozen sections, and also the first time SHINERS has been utilized for breast cancer detection. Conclusions demonstrated in this paper confirm that SHINERS has great potentials to be applied to the identification of breast lesions as an auxiliary method to mammography in the early diagnosis of breast cancer.

Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43- ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3-10.3 wt% CO32- range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.