Fetuin-A and albumin alter cytotoxic effects of calcium phosphate nanoparticles on human vascular smooth muscle cells

Femtosecond Laser-Engineered β-TCP Scaffolds: A Comparative Study of Green-Synthesized AgNPs vs. Ion Doping Against S. aureus for Bone Regeneration

Implant-associated infections, particularly those linked to Staphylococcus aureus (S. aureus), continue to compromise the clinical success of β-tricalcium phosphate (β-TCP) implants despite their excellent biocompatibility and osteoconductivity. This investigation aims to tackle these challenges by integrating femtosecond (fs)-laser surface processing with two complementary strategies: ion doping and functionalization with green-synthesized silver nanoparticles (AgNPs). AgNPs were produced via fs-laser photoreduction using green tea leaf extract (GTLE), noted for its anti-inflammatory and antioxidant properties. Fs-laser processing was applied to modify β-TCP scaffolds by systematically varying scanning velocities, fluences, and patterns. Lower scanning velocities generated organized nanostructures with enhanced roughness and wettability, as confirmed by scanning electron microscopy (SEM), optical profilometry, and contact angle measurements, whereas higher laser energies induced significant phase transitions between hydroxyapatite (HA) and α-tricalcium phosphate (α-TCP), as revealed by X-ray diffraction (XRD). AgNP-functionalized scaffolds demonstrated markedly superior antibacterial activity against S. aureus compared to the ion-doped variants, attributed to the synergistic interplay of nanostructure-mediated surface disruption and AgNP-induced bactericidal mechanisms. Although ion-doped scaffolds exhibited limited direct antibacterial effects, they showed concentration-dependent activity in indirect assays, likely due to controlled ion release. Both strategies promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) under defined conditions, albeit with transient cytotoxicity at higher fluences and excessive ion doping. Overall, this approach holds promise for markedly improving antibacterial efficacy and osteogenic compatibility, potentially transforming bone regeneration therapies.

Risk factors for and a preliminary prediction model of coronary artery calcification in patients beginning hemodialysis

BACKGROUND AND HYPOTHESIS

Vascular calcification (VC) is an important risk factor for cardiovascular events in patients undergoing maintenance hemodialysis (MHD); however, there is limited data on VC-related factors in patients beginning hemodialysis. Thus, this study aimed to determine the risk factors of VC and to establish a prediction model for evaluating VC progression in new patients undergoing hemodialysis.

METHODS

This study selected 86 patients who initiated in-center MHD between March 2021 and November 2022. Demographic characteristics, medical history, and laboratory data were collected. Coronary artery calcification (CAC) was assessed based on the Agatston vascular score determined via computed tomography. Serum levels of the VC inhibitors fetuin-A was quantified via enzyme-linked immunosorbent assays. Univariate and multivariate regression analyses were conducted to determine the risk factors for VC, and a neural network-based approach was adopted to construct a VC prediction model.

RESULTS

The average age of the patients was 56.74 ± 12.79 years, and 65.1% were male. CAC was observed in 72.09% of patients. Age, body mass index, diabetes, the comorbidity index, and the number of coronary artery branches with calcification were positively correlated with the CAC score, whereas plasma fetuin-A levels was negatively correlated. The multivariate logistic regression analysis revealed that age [odds ratio (OR) 1.07, 95%CI 1.00-1.14], the comorbidity index [OR 1.72, 95%CI 1.16-2.57], diabetes [OR 3.97, 95%CI 1.16-13.58] were independent risk factors for CAC; these factors were used to establish a simple scoring model to predict VC risk.

CONCLUSION

Age, the comorbidity index, diabetes were identified as independent risk factors for CAC in patients beginning hemodialysis, and the new VC prediction model based on these factors may help identify VC in patients undergoing MHD, facilitating clinical interventions.

Calcium phosphate formation and deposition in ischemic neurons

Ischemic stroke causes acute brain calcium phosphate (CaP) deposition, a process involving primarily the injured neurons. Whereas the adverse impact of CaP deposition on the brain structure and function has been recognized, the underlying mechanisms remain poorly understood. This investigation demonstrated that the neuron-expressed, plasma membrane-associated Ca2+-binding proteins annexin (Anx) A2, AnxA5, AnxA6, and AnxA7 contributed to neuronal CaP deposition in the mouse model of ischemic stroke. These Anxs were released from the degraded plasma membrane of the ischemic neurons and were able to form Anx/CaP complexes, a nanostructure capable of binding to the β actin filaments via Anx-actin interaction to cause neuronal CaP deposition prior to brain infarction. Anx administration to the healthy mouse brain caused brain CaP deposition and infarction. Monomeric β actin was able to block competitively Anx binding to β actin filaments and prevent ischemic stroke- and Anx administration-induced brain CaP deposition and infarction. Administration of siRNAs specific to the four Anx mRNAs alleviated brain CaP deposition and infarction. These observations support the role of Anxs in CaP formation and deposition in ischemic neurons.

Histopathological effects of hypervitaminosis-D and the protective role of fetuin-A in renal, hepatic, and cardiac tissues in a murine model

Hypervitaminosis D leads to toxic effects, including hypercalcemia, which can cause severe damage to various organs. Fetuin-A, a glycoprotein with anti-inflammatory properties, may protect tissues from such damage. This study explores the role of Fetuin-A in mitigating hypervitaminosis D-induced damage in renal, hepatic, and cardiac tissues. The objectives of this study were to: (1) Assess the extent of tissue damage from high-dose vitamin D in a murine model by examining the histopathological changes in liver, kidney and heart. (2) Investigate Fetuin-A's protective effect against this damage. Thirty-six albino rats were divided into four groups: (1) control, (2) vitamin D toxicity, (3) Fetuin-A + vitamin D, and (4) Fetuin-A only. Vitamin D was administered subcutaneously at 250 μg/20 g/day for 3 days. Fetuin-A was given at 100 μl/20 g, starting 7 days before vitamin D treatment. Histopathological analysis of liver, kidney, and heart tissues was performed using H&E and Alizarin Red staining and findings were analysed statistically. Vitamin D toxicity caused significant tissue damage, including apoptosis, inflammation, and calcification in the liver, kidneys, and heart. Pre-treatment with Fetuin-A reduced calcification and inflammation, preserving tissue architecture. Fetuin-A-only rats showed no damage or calcification. Fetuin-A provided statistically significant protection against vitamin D-induced damage, reducing oxidative stress and calcification in affected organs. These findings suggest Fetuin-A could be a potential therapeutic agent for hypervitaminosis D.

Dual-Function Femtosecond Laser: β-TCP Structuring and AgNP Synthesis via Photoreduction with Azorean Green Tea for Enhanced Osteointegration and Antibacterial Properties

β-Tricalcium phosphate (β-TCP) is a well-established biomaterial for bone regeneration, highly regarded for its biocompatibility and osteoconductivity. However, its clinical efficacy is often compromised by susceptibility to bacterial infections. In this study, we address this limitation by integrating femtosecond (fs)-laser processing with the concurrent synthesis of silver nanoparticles (AgNPs) mediated by Azorean green tea leaf extract (GTLE), which is known for its rich antioxidant and anti-inflammatory properties. The fs laser was employed to modify the surface of β-TCP scaffolds by varying scanning velocities, fluences, and patterns. The resulting patterns, formed at lower scanning velocities, display organized nanostructures, along with enhanced roughness and wettability, as characterized by Scanning Electron Microscopy (SEM), optical profilometry, and contact angle measurements. Concurrently, the femtosecond laser facilitated the photoreduction of silver ions in the presence of GTLE, enabling the efficient synthesis of small, spherical AgNPs, as confirmed by UV-vis spectroscopy, Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). The resulting AgNP-embedded β-TCP scaffolds exhibited a significantly improved cell viability and elongation of human bone marrow mesenchymal stem cells (hBM-MSCs), alongside significant antibacterial activity against Staphylococcus aureus (S. aureus). This study underscores the transformative potential of combining femtosecond laser surface modification with GTLE-mediated AgNP synthesis, presenting a novel and effective strategy for enhancing the performance of β-TCP scaffolds in bone-tissue engineering.

Reduced Fetuin-A Levels Are Associated With Exercise Intolerance and Predict the Risk of Adverse Outcomes in Patients With Heart Failure: The Role of Cardiac-Hepatic-Peripheral Interaction

BACKGROUND

Exercise intolerance in heart failure arises from multifactorial pathophysiological mechanisms. Hepatokines, liver-synthesized molecules, regulate systemic metabolisms in peripheral tissues. We previously identified the hepatokine fetuin-A as being linked to liver hypoperfusion in heart failure. Here, we investigated the role of fetuin-A in connecting cardiac-hepatic-peripheral interaction.

METHODS AND RESULTS

We conducted a prospective study involving 202 consecutive hospitalized patients (mean age, 56.8 years; 76.2% men) with heart failure who underwent cardiopulmonary exercise testing. We measured the serum concentration of fetuin-A by ELISA. Correlation analysis revealed a negative association between fetuin-A levels and the ratio of minimum minute ventilation to carbon dioxide production, its slope, and a tendency toward a positive correlation with peak oxygen uptake. Patients with impaired exercise tolerance exhibited lower fetuin-A levels. During a median follow-up of 1045 days, 18.3% experienced cardiac events, including 4 cardiac deaths and 33 cases of worsening heart failure. Classification and regression tree analysis identified a high-risk subgroup with lower fetuin-A (<24.3 mg/L) and impaired exercise tolerance (peak oxygen uptake<14.2 mL/kg per min). Kaplan-Meier analysis revealed that this subgroup had the highest risk of cardiac events. In a multivariable Cox proportional hazard model, the combination of lower fetuin-A and exercise intolerance was independently associated with increased risks of cardiac events.

CONCLUSIONS

Reduced circulating fetuin-A levels were associated with exercise intolerance in heart failure patients. Fetuin-A could emerge as a target implicated in exercise capacity connecting cardiac-hepatic-peripheral interaction and as a valuable biomarker for predicting prognosis when combined with peak oxygen uptake.

Associations of urinary fetuin-A with histopathology and kidney events in biopsy-proven kidney disease

Background

Fetuin-A is implicated in the pathogenesis of vascular calcification in chronic kidney disease (CKD); however, the relationship between fetuin-A, histopathologic lesions and long-term kidney outcomes in patients with various types of kidney disease remains unclear.

Methods

We measured urinary fetuin-A levels in 335 individuals undergoing clinically indicated native kidney biopsy. The expressions of fetuin-A mRNA and protein in the kidney were assessed using RNA sequencing and immunohistochemistry. The association of urinary fetuin-A with histopathologic lesions and major adverse kidney events (MAKE), defined as a decline in estimated glomerular filtration rate (eGFR) of at least 40%, kidney failure or death, was analyzed.

Results

Urinary fetuin-A levels showed a positive correlation with albuminuria (rs = 0.67, P < .001) and a negative correlation with eGFR (rs = -0.46, P < .001). After multivariate adjustment, higher urinary fetuin-A levels were associated with glomerular inflammation, mesangial expansion, interstitial fibrosis and tubular atrophy, and arteriolar sclerosis. Using a 1 transcript per million gene expression cutoff, we found kidney fetuin-A mRNA levels below the threshold in both individuals with normal kidney function and those with CKD. Additionally, immunohistochemistry revealed reduced fetuin-A staining in tubular cells of CKD patients compared with normal controls. During a median 21-month follow-up, 115 patients experienced MAKE, and Cox regression analysis confirmed a significant association between elevated urinary fetuin-A and MAKE. This association remained significant after adjusting for potential confounding factors.

Conclusion

Urinary fetuin-A is associated with chronic histological damage and adverse clinical outcomes across a spectrum of biopsy-proven kidney diseases.

Magnesium inhibits peritoneal calcification as a late-stage characteristic of encapsulating peritoneal sclerosis

Peritoneal calcification is a prominent feature of the later stage of encapsulating peritoneal sclerosis (EPS) in patients undergoing long-term peritoneal dialysis (PD). However, the pathogenesis and preventive strategy for peritoneal calcification remain unclear. Peritoneum samples from EPS patients were examined histologically. Peritoneal calcification was induced in mice by feeding with an adenine-containing diet combined with intraperitoneal administration of lipopolysaccharide and a calcifying solution containing high calcium and phosphate. Excised mouse peritoneum, human mesothelial cells (MeT5A), and mouse embryonic fibroblasts (MEFs) were cultured in calcifying medium. Immunohistochemistry confirmed the appearance of osteoblastic differentiation-marker-positive cells in the visceral peritoneum from EPS patients. Intraperitoneal administration of magnesium suppressed peritoneal fibrosis and calcification in mice. Calcifying medium increased the calcification of cultured mouse peritoneum, which was prevented by magnesium. Calcification of the extracellular matrix was accelerated in Met5A cells and MEFs treated with calcification medium. Calcifying medium also upregulated osteoblastic differentiation markers in MeT5A cells and induced apoptosis in MEFs. Conversely, magnesium supplementation mitigated extracellular matrix calcification and phenotypic transdifferentiation and apoptosis caused by calcifying conditions in cultured MeT5A cells and MEFs. Phosphate loading contributes to the progression of EPS through peritoneal calcification and fibrosis, which can be prevented by magnesium supplementation.

Predictive role of cardiac valvular calcification in all-cause mortality of Chinese initial haemodialysis patients: a follow-up study of 4 years

BACKGROUND

Cardiac valvular calcification (CVC) is prevalent in haemodialysis (HD) patients. Its association with mortality in Chinese incident haemodialysis (IHD) patients remains unknown.

METHODS

A total of 224 IHD patients who had just begun HD therapy at Zhongshan Hospital, Fudan University, were enrolled and divided into two groups according to the detection of cardiac valvular calcification (CVC) by echocardiography. The patients were followed for a median of 4 years for all-cause mortality and cardiovascular mortality.

RESULTS

During follow-up, 56 (25.0%) patients died, including 29 (51.8%) of cardiovascular disease. The adjusted HR related to all-cause mortality was 2.14 (95% CI, 1.05-4.39) for patients with cardiac valvular calcification. However, CVC was not an independent risk factor for cardiovascular mortality in patients who had just begun HD therapy.

CONCLUSION

CVC at baseline is an independent risk factor for all-cause mortality in HD patients and makes an independent contribution to the prediction of all-cause mortality. These findings support the use of echocardiography at the beginning of HD.

Development of Neovasculature in Axially Vascularized Calcium Phosphate Cement Scaffolds

Augmenting the vascular supply to generate new tissues, a crucial aspect in regenerative medicine, has been challenging. Recently, our group showed that calcium phosphate can induce the formation of a functional neo-angiosome without the need for microsurgical arterial anastomosis. This was a preclinical proof of concept for biomaterial-induced luminal sprouting of large-diameter vessels. In this study, we investigated if sprouting was a general response to surgical injury or placement of an inorganic construct around the vessel. Cylindrical biocement scaffolds of differing chemistries were placed around the femoral vein. A contrast agent was used to visualize vessel ingrowth into the scaffolds. Cell populations in the scaffold were mapped using immunohistochemistry. Calcium phosphate scaffolds induced 2.7-3 times greater volume of blood vessels than calcium sulphate or magnesium phosphate scaffolds. Macrophage and vSMC populations were identified that changed spatially and temporally within the scaffold during implantation. NLRP3 inflammasome activation peaked at weeks 2 and 4 and then declined; however, IL-1β expression was sustained over the course of the experiment. IL-8, a promoter of angiogenesis, was also detected, and together, these responses suggest a role of sterile inflammation. Unexpectedly, the effect was distinct from an injury response as a result of surgical placement and also was not simply a foreign body reaction as a result of placing a rigid bioceramic next to a vein, since, while the materials tested had similar microstructures, only the calcium phosphates tested elicited an angiogenic response. This finding then reveals a potential path towards a new strategy for creating better pro-regenerative biomaterials.

Calciprotein Particle Synthesis Strategy Determines In Vitro Calcification Potential

Circulating calciprotein particles (CPP), colloids of calcium, phosphate and proteins, were identified as potential drivers of the calcification process in chronic kidney disease. The present study compared CPP produced using different protocols with respect to particle morphology, composition, particle number and in vitro calcification potency. CPP were synthesized with 4.4 mM (CPP-A and B) or 6 mM (CPP-C and D) phosphate and 2.8 mM (CPP-A and B) or 10 mM (CPP-C and D) calcium, with either bovine fetuin-A (CPP-C) or fetal bovine serum (CPP-A, B and D) as a source of protein, and incubated for 7 (CPP-A2) or 14 days (CPP-B2), 12 h (CPP-C2, D2 and B1) or 30 min (CPP-D1). Particle number was determined with nanoparticle tracking and calcium content was measured in CPP preparations and to determine human vascular smooth muscle cell (hVSMC) calcification. Morphologically, CPP-C2 were the largest. Particle number did not correspond to the calcium content of CPP. Both methods of quantification resulted in variable potencies of CPP2 to calcify VSMC, with CPP-B2 as most stable inducer of hVSMC calcification. In contrast, CPP-B1 and D1 were unable to induce calcification of hVSMC, and endogenous CPP derived from pooled serum of dialysis patients were only able to calcify hVSMC to a small extent compared to CPP2.CPP synthesized using different protocols appear morphologically similar, but in vitro calcification potency is dependent on composition and how the CPP are quantified. Synthetic CPP are not comparable to endogenous CPP in terms of the calcification propensity.

Facile fabrication of hierarchically nanostructured gold electrode for bio-electrochemical applications

Nanoporous gold (NPG) is one of the most extensively investigated nanomaterials owing to its tunable pore size, ease of surface modification, and range of applications from catalysis, actuation, and molecular release to the development of electrochemical sensors. In an effort to improve the usefulness of NPG, a simple and robust method for the fabrication of hierarchical and bimodal nanoporous gold electrodes (hb-NPG) containing both macro-and mesopores is reported using electrochemical alloying and dealloying processes to engineer a bicontinuous solid/void morphology. Scanning electron microscopy (color SEM) images depict the hierarchical pore structure created after the multistep synthesis with an ensemble of tiny pores below 100 nm in size located in ligaments spanning larger pores of several hundred nanometers. Smaller-sized pores are exploited for surface modification, and the network of larger pores aids in molecular transport. Cyclic voltammetry (CV) was used to compare the electrochemically active surface area of the hierarchical bimodal structure with that of the regular unimodal NPG with an emphasis on the critical role of both dealloying and annealing in creating the desired structure. The adsorption of different proteins was followed using UV-vis absorbance measurements of solution depletion revealing the high loading capacity of hb-NPG. The surface coverage of lipoic acid on the hb-NPG was analyzed using thermogravimetric analysis (TGA) and reductive desorption. The roughness factor determinations suggest that the fabricated hb-NPG electrode has tremendous potential for biosensor development by changing the scaling relations between volume and surface area which may lead to improved analytical performance. We have chosen to take advantage of the surface architectures of hb-NPG due to the presence of a large specific surface area for functionalization and rapid transport pathways for faster response. It is shown that the hb-NPG electrode has a higher sensitivity for the amperometric detection of glucose than does an NPG electrode of the same geometric surface area.

Biological and Medical Applications of Calcium Phosphate Nanoparticles

Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.

Calciprotein Particles: Balancing Mineral Homeostasis and Vascular Pathology

[Figure: see text].

Live Imaging of Calciprotein Particle Clearance and Receptor Mediated Uptake: Role of Calciprotein Monomers

Background

The liver-derived plasma protein fetuin A is a systemic inhibitor of ectopic calcification. Fetuin-A stabilizes calcium phosphate mineral initially as ion clusters to form calciprotein monomers (CPM), and then as larger multimeric consolidations containing amorphous calcium phosphate (primary CPP, CPP 1) or more crystalline phases (secondary CPP, CPP 2). CPM and CPP mediate excess mineral stabilization, transport and clearance from circulation.

Methods

We injected i.v. synthetic fluorescent CPM and studied their clearance by live two-photon microscopy. We analyzed organ sections by fluorescence microscopy to assess CPM distribution. We studied cellular clearance and cytotoxicity by flow cytometry and live/dead staining, respectively, in cultured macrophages, liver sinusoidal endothelial cells (LSEC), and human proximal tubule epithelial HK-2 cells. Inflammasome activation was scored in macrophages. Fetuin A monomer and CPM charge were analyzed by ion exchange chromatography.

Results

Live mice cleared CPP in the liver as published previously. In contrast, CPM were filtered by kidney glomeruli into the Bowman space and the proximal tubules, suggesting tubular excretion of CPM-bound calcium phosphate and reabsorption of fetuin A. Fetuin-A monomer clearance was negligible in liver and low in kidney. Anion exchange chromatography revealed that fetuin A monomer was negatively charged, whereas CPM appeared neutral, suggesting electrochemical selectivity of CPM versus fetuin A. CPM were non-toxic in any of the investigated cell types, whereas CPP 1 were cytotoxic. Unlike CPP, CPM also did not activate the inflammasome.

Conclusions

Fetuin-A prevents calcium phosphate precipitation by forming CPM, which transform into CPP. Unlike CPP, CPM do not trigger inflammation. CPM are readily cleared in the kidneys, suggesting CPM as a physiological transporter of excess calcium and phosphate. Upon prolonged circulation, e.g., in chronic kidney disease, CPM will coalesce and form CPP, which cannot be cleared by the kidney, but will be endocytosed by liver sinusoidal endothelial cells and macrophages. Large amounts of CPP trigger inflammation. Chronic CPM and CPP clearance deficiency thus cause calcification by CPP deposition in blood vessels and soft tissues, as well as inflammation.

Sodium thiosulphate and progression of vascular calcification in end-stage renal disease patients: a double-blind, randomized, placebo-controlled study

BACKGROUND

Sodium thiosulphate (NaTS) is mostly used in haemodialysis (HD) patients with calcific uraemic arteriolopathy. This double-blind, randomized, placebo-controlled study assessed the effect of NaTS on progression of cardiovascular calcifications in HD patients.

METHODS

From 65 screened patients, we recruited 60 patients with an abdominal aorta Agatston calcification score ≥100. Thirty patients were randomized to receive NaTS 25 g/1.73 m2 and 30 patients to receive 100 mL of 0.9% sodium chloride intravenously during the last 15 min of HD over a period of 6 months. The primary endpoint was the absolute change of the abdominal aortic calcification score.

RESULTS

The abdominal aortic calcification score and calcification volume of the abdominal aorta increased similarly in both treatment groups during the trial. As compared with the saline group, patients receiving NaTS exhibited a reduction of their iliac artery calcification score (-137 ± 641 versus 245  ± 755; P = 0.049), reduced pulse wave velocity (9.6  ± 2.7 versus 11.4 ± 3.6; P = 0.000) and a lower carotid intima-media thickness (0.77  ± 0.1 versus 0.83  ±  00.17; P = 0.033) and had better preservation of echocardiographic parameters of left ventricular hypertrophy. No patient of the NaTS group developed new cardiac valve calcifications during the trial as compared with 8 of 29 patients in the saline group. By univariate analysis, NaTS therapy was the only predictor of not developing new valvular calcifications. No adverse events possibly related to NaTS infusion were noted.

CONCLUSIONS

While NaTS failed to retard abdominal aortic calcification progress, it positively affected calcification progress in iliac arteries and heart valves as well as several other cardiovascular functional parameters.

Reactive Oxygen-Forming Nox5 Links Vascular Smooth Muscle Cell Phenotypic Switching and Extracellular Vesicle-Mediated Vascular Calcification

RATIONALE

Vascular calcification, the formation of calcium phosphate crystals in the vessel wall, is mediated by vascular smooth muscle cells (VSMCs). However, the underlying molecular mechanisms remain elusive, precluding mechanism-based therapies.

OBJECTIVE

Phenotypic switching denotes a loss of contractile proteins and an increase in migration and proliferation, whereby VSMCs are termed synthetic. We examined how VSMC phenotypic switching influences vascular calcification and the possible role of the uniquely calcium-dependent reactive oxygen species (ROS)-forming Nox5 (NADPH oxidase 5).

METHODS AND RESULTS

In vitro cultures of synthetic VSMCs showed decreased expression of contractile markers CNN-1 (calponin 1), α-SMA (α-smooth muscle actin), and SM22-α (smooth muscle protein 22α) and an increase in synthetic marker S100A4 (S100 calcium binding protein A4) compared with contractile VSMCs. This was associated with increased calcification of synthetic cells in response to high extracellular Ca²⁺. Phenotypic switching was accompanied by increased levels of ROS and Ca²⁺-dependent Nox5 in synthetic VSMCs. Nox5 itself regulated VSMC phenotype as siRNA knockdown of Nox5 increased contractile marker expression and decreased calcification, while overexpression of Nox5 decreased contractile marker expression. ROS production in synthetic VSMCs was cytosolic Ca²⁺-dependent, in line with it being mediated by Nox5. Treatment of VSMCs with Ca²⁺ loaded extracellular vesicles (EVs) lead to an increase in cytosolic Ca²⁺. Inhibiting EV endocytosis with dynasore blocked the increase in cytosolic Ca²⁺ and VSMC calcification. Increased ROS production resulted in increased EV release and decreased phagocytosis by VSMCs.

CONCLUSIONS

We show here that contractile VSMCs are resistant to calcification and identify Nox5 as a key regulator of VSMC phenotypic switching. Additionally, we describe a new mechanism of Ca²⁺ uptake via EVs and show that Ca²⁺ induces ROS production in VSMCs via Nox5. ROS production is required for release of EVs, which promote calcification. Identifying molecular pathways that control Nox5 and VSMC-derived EVs provides potential targets to modulate vascular remodeling and calcification in the context of mineral imbalance. Graphic Abstract: A graphic abstract is available for this article.

Magnesium and calciprotein particles in vascular calcification: the good cop and the bad cop

PURPOSE OF REVIEW

Vascular calcification is a major contributor to increased cardiovascular mortality in chronic kidney disease (CKD). Recently, calciprotein particles (CPP) were identified to drive the calcification process. CPP may explain the effects of high phosphate on vascular calcification. Magnesium is a promising novel therapeutic approach to halt vascular calcification, because it inhibits CPP maturation and is associated with reduced cardiovascular mortality in CKD. We aim to examine the current evidence for the role of CPP in the calcification process and to explain how magnesium prevents calcification.

RECENT FINDINGS

A recent meta-analysis concluded that reducing high phosphate levels in CKD patients does not associate with lowering cardiovascular mortality. Inhibition of CPP formation prevents phosphate-induced calcification in vitro. Consequently, delaying CPP formation and maturation may be a clinical approach to reduce calcification. Magnesium inhibits CPP maturation and vascular calcification. Clinical pilot studies suggest that magnesium is a promising intervention strategy against calcification in CKD patients.

SUMMARY

CPP induce vascular calcification and are modulated by serum phosphate and magnesium concentrations. Magnesium is a strong inhibitor of CPP maturation and therefore, a promising therapeutic approach to reduce vascular calcification in CKD. Currently, several studies are being performed to determine the clinical outcomes of magnesium supplementation in CKD.

Seaweed Porphyra yezoensis polysaccharides with different molecular weights inhibit hydroxyapatite damage and osteoblast differentiation of A7R5 cells

Vascular calcification (VC) is a common pathological manifestation in patients with cardiovascular diseases, leading to high mortality in patients with chronic kidney diseases. The deposition of hydroxyapatite (HAP) crystals on vascular smooth muscle cells leads to cell damage, which promotes osteogenic transformation. In this study, four different molecular weights (MWs ) of Porphyra yezoensis polysaccharides (PYP1, PYP2, PYP3, and PYP4 with MWs of 576, 49.5, 12.6, and 4.02 kDa, respectively) were used to coat HAP, and the differences in toxicity and calcification of HAP on A7R5 cells before and after coating were studied. The results showed that PYPs could effectively reduce HAP damage to the A7R5 cells. Under the protection of PYPs, cell viability increased and lactate dehydrogenase release, active oxygen level, and cell necrosis rate decreased; also, the amount of the HAP crystals adhering to cell surfaces and entering cells decreased. PYPs with low molecular weights presented better protective effects than high-molecular-weight PYPs. PYPs also inhibited the osteogenic transformation of the A7R5 cells induced by HAP and decreased alkaline phosphatase (ALP) activity and expressions of bone/chondrocyte phenotype genes (runt-related factor 2, ALP, osteopontin, and osteocalcin). In the adenine-induced chronic renal failure (CRF) mouse VC model, PYP4 was found to obviously inhibit the aortic calcium level, and it also inhibited the serum creatinine, serum phosphorus and serum BUN levels. PYP4 (least molecular weight) showed the best inhibitory effect on calcification and may be considered as a candidate drug with therapeutic potential for inhibiting cellular damage and osteoblast differentiation induced by the HAP crystals.

Shape-dependent toxicity and mineralization of hydroxyapatite nanoparticles in A7R5 aortic smooth muscle cells

Vascular smooth muscle cell damage is a key step in inducing vascular calcification that yields hydroxyapatite (HAP) as a major product. The effect of the shape of HAP on the damage to vascular smooth muscle cells has yet to be investigated. In this study, we compared the differences in toxicity of four various morphological nano-HAP crystals, namely, H-Rod, H-Needle, H-Sphere, and H-Plate, in rat aortic smooth muscle cells (A7R5). The sizes of these crystals were 39 nm × 115 nm, 41 nm ×189 nm, 56 nm × 56 nm, and 91 nm × 192 nm, respectively. Results showed that all HAPs decreased cell viability, disorganized cell morphology, disrupted cell membranes, increased intracellular reactive oxygen species concentration, decreased mitochondrial membrane potential, decreased lysosome integrity, increased alkaline phosphatase activity, and increased intracellular calcium concentration, resulting in cell necrosis. The cytotoxicity of the four kinds of HAP was ranked as follows: H-Plate > H-Sphere > H-Needle > H-Rod. The cytotoxicity of each crystal was positively correlated with the following factors: large specific surface area, high electrical conductivity and low surface charge. HAP accelerated calcium deposits on the A7R5 cell surface and induced the expression of osteogenic proteins, such as BMP-2, Runx2, OCN, and ALP. The crystals with high cytotoxicity caused more calcium deposits on the cell surface, higher expression levels of osteogenic protein, and stronger osteogenic transformation abilities. These findings elucidated the relationship between crystal shape and cytotoxicity and provided theoretical references for decreasing the risks of vascular calcification.

A Proteomic Study of Atherosclerotic Plaques in Men with Coronary Atherosclerosis

Background: To study the changes in protein composition of atherosclerotic plaques at different stages of their development in coronary atherosclerosis using proteomics. Methods: The object of research consisted of homogenates of atherosclerotic plaques from coronary arteries at different stages of development, obtained from 15 patients. Plaque proteins were separated by two-dimensional electrophoresis. The resultant protein spots were identified by the matrix-assisted laser desorption ionization method with peptide mass mapping. Results: Groups of differentially expressed proteins, in which the amounts of proteins differed more than twofold (p < 0.05), were identified in pools of homogenates of atherosclerotic plaques at three stages of development. The amounts of the following proteins were increased in stable atherosclerotic plaques at the stage of lipidosis and fibrosis: vimentin, tropomyosin β-chain, actin, keratin, tubulin β-chain, microfibril-associated glycoprotein 4, serum amyloid P-component, and annexin 5. In plaques at the stage of fibrosis and calcification, the amounts of mimecan and fibrinogen were increased. In unstable atherosclerotic plaque of the necrotic–dystrophic type, the amounts of human serum albumin, mimecan, fibrinogen, serum amyloid P-component and annexin were increased. Conclusion: This proteomic study identifies the proteins present in atherosclerotic plaques of coronary arteries by comparing their proteomes at three different stages of plaque development during coronary atherosclerosis.

Calcium Signaling and Tissue Calcification

Calcification is a regulated physiological process occurring in bones and teeth. However, calcification is commonly found in soft tissues in association with aging and in a variety of diseases. Over the last two decades, it has emerged that calcification occurring in diseased arteries is not simply an inevitable build-up of insoluble precipitates of calcium phosphate. In some cases, it is an active process in which transcription factors drive conversion of vascular cells to an osteoblast or chondrocyte-like phenotype, with the subsequent production of mineralizing "matrix vesicles." Early studies of bone and cartilage calcification suggested roles for cellular calcium signaling in several of the processes involved in the regulation of bone calcification. Similarly, calcium signaling has recently been highlighted as an important component in the mechanisms regulating pathological calcification. The emerging hypothesis is that ectopic/pathological calcification occurs in tissues in which there is an imbalance in the regulatory mechanisms that actively prevent calcification. This review highlights the various ways that calcium signaling regulates tissue calcification, with a particular focus on pathological vascular calcification.

Effects of physical properties of nano-sized hydroxyapatite crystals on cellular toxicity in renal epithelial cells

Hydroxyapatite (HAP) is not only a common component of most idiopathic CaOx stones, but also the core of Randall's plaque. HAP is a nest that can induce the formation of Randall's plaques and even kidney stones. We studied the toxic effects and mechanisms of four different types of nano-HAP crystals (H-Sphere, 72.5 nm × 72.5 nm; H-Needle, 37.2 nm × 162.7 nm; H-Rod, 42.3 nm × 115.3 nm; and H-Plate, 145.5 nm × 272.9 nm) on human renal proximal tubular epithelial cells (HK-2). HAP crystals could cause oxidative stress that triggered a series of cell dysfunction problems, resulting in decreased cell viability, loss of cell membrane integrity, cell swelling, and cell necrosis. The toxic effect of HAP was mainly attributed to its entry into cell by endocytosis and its accumulation in the lysosomes, causing the level of intracellular reactive oxygen species (ROS) to rise, the mitochondrial membrane potential (Δψm) to decrease, the lysosomal integrity to be destroyed, and the cell cycle blocked during the G0/G1 phase. The cytotoxicity of the four kinds of HAP crystals was ranked as follows: H-Sphere > H-Needle > H-Rod > H-Plate. The cytotoxicity of each crystal was positively correlated with low absolute zeta potential, conduciveness to internalized morphology, large specific surface area and aspect ratio, and small particle size. These results indicated that nano-HAP could damage HK-2 cells, and the physical properties of HAP crystals play a vital effect in their cytotoxicity.

Clinical implications of fetuin-A

Fetuin-A, also termed alpha2-Heremans-Schmid glycoprotein, is a 46kDa hepatocyte derived protein (hepatokine) and serves multifaceted functions.

Research Progress on the Relationship between Coronary Artery Calcification and Chronic Renal Failure

Objective:

Coronary artery calcification (CAC) is thought to be a controlled metabolic process that is very similar to the formation of new bone. In patients with chronic renal failure (CRF), CAC is very common, and CAC severity correlates with the deterioration of renal function. We summarized the current understanding and emerging findings of the relationship between CAC and CRF.

Data Sources:

All studies were identified by systematically searching PubMed, Embase, and CNKI databases for the terms “coronary calcification”, “chronic renal failure”, “vascular smooth muscle cell”, and their synonyms until September 2017.

Study Selection:

We examined the titles and abstracts of all studies that met our search strategy thoroughly. The full text of relevant studies was evaluated. Reference lists of retrieved articles were also scrutinized for the additional relevant studies.

Results:

CRF can accelerate CAC progression. CRF increases the expression of pro-inflammatory factors, electrolyte imbalance (e.g., of calcium, phosphorus), parathyroid hormone, and uremic toxins and their ability to promote calcification. These factors, through the relevant signaling pathways, trigger vascular smooth muscle cells to transform into osteoblast-like cells while inhibiting the reduction of vascular calcification factors, thus inducing further CAC.

Conclusions:

Coronary heart disease in patients with CRF is due to multiple factors. Understanding the mechanism of CAC can help interventionists to protect the myocardium and reduce the prevalence of coronary heart disease and mortality.

Review of potential health risks associated with nanoscopic calcium phosphate

Calcium phosphate is applied in many products in biomedicine, but also in toothpastes and cosmetics. In some cases, it is present in nanoparticulate form, either on purpose or after degradation or mechanical abrasion. Possible concerns are related to the biological effect of such nanoparticles. A thorough literature review shows that calcium phosphate nanoparticles as such have no inherent toxicity but can lead to an increase of the intracellular calcium concentration after endosomal uptake and lysosomal degradation. However, cells are able to clear the calcium from the cytoplasm within a few hours, unless very high doses of calcium phosphate are applied. The observed cytotoxicity in some cell culture studies, mainly for unfunctionalized particles, is probably due to particle agglomeration and subsequent sedimentation onto the cell layer, leading to a very high local particle concentration, a high particle uptake, and subsequent cell death. There is no risk from an oral uptake of calcium phosphate nanoparticles due to their rapid dissolution in the stomach. The risk from dermal or mucosal uptake is very low. Calcium phosphate nanoparticles can enter the bloodstream by inhalation, but no adverse effects have been observed, except for a prolonged exposition to high particle doses. Calcium phosphate nanoparticles inside the body (e.g. after implantation or due to abrasion) do not pose a risk as they are typically resorbed and dissolved by osteoclasts and macrophages. There is no indication for a significant influence of the calcium phosphate phase or the particle shape (e.g. spherical or rod-like) on the biological response. In summary, the risk associated with an exposition to nanoparticulate calcium phosphate in doses that are usually applied in biomedicine, health care products, and cosmetics is very low and most likely not present at all.

STATEMENT OF SIGNIFICANCE

Calcium phosphate is a well-established biomaterial. However, there are occasions when it occurs in a nanoparticulate form (e.g. as nanoparticle or as nanoparticulate bone substitution material) or after abrasion from a calcium phosphate-coated metal implant. In the light of the current discussion on the safety of nanoparticles, there have been concerns about potential adverse effects of nano-calcium phosphate, e.g. in a statement of a EU study group from 2016 about possible dangers associated with non-spherical nano-hydroxyapatite in cosmetics. In the US, there was a discussion in 2016 about the dangers of nano-calcium phosphate in babyfood. In this review, the potential exposition routes for nano-calcium phosphate are reviewed, with special emphasis on its application as biomaterial.

Prognostic value of cardiovascular calcifications in hemodialysis patients: a longitudinal study

PURPOSE

Cardiovascular calcifications (CVC) are present in up to 70% of non-diabetic dialysis patients. Sparse data are available on predictors of very long-term outcomes of such patients. The Belgrade Aachen Study on Calcification in Hemodialysis patients (BASCH study) aimed to study this using a comprehensive CVC assessment.

METHODS

We prospectively analyzed 220 hemodialysis patients followed for a mean of 76 months (median 73 months, range 6-160 months). We compared patients deceased from cardiovascular diseases (CVD) and survivors. Analyses included composite calcification scores (determined by combining ultrasound and X-ray analyses), demographic, clinical and laboratory data and pulse wave velocity (PWV). For survival analysis, patients were divided into group according to quartiles (Q).

RESULTS

Compared to survivors, deceased patients from CVD were significantly older, more frequently hypertensive, had shorter dialysis times per week and lower Kt/V values, and they exhibited lower serum fetuin A, osteoprotegerin and hemoglobin as well as higher CRP levels. Composite calcification and Adragao scores were significantly higher in deceased patients from CVD as was PWV. Mean survival was 101 ± 47 months (Q1), 87 ± 51 month (Q2), 66 ± 48 (Q3) and 54 ± 45 months (Q4), p = 0.000. Cox multivariate regression analysis showed that independent predictors for cardiovascular mortality were composite calcification score in the range of third and fourth quartiles.

CONCLUSION

Composite calcification score emerged as significant predictors of long-term survival in our group of largely non-diabetic dialysis patient population, finding that should be confirmed by intervention studies.

Calcium phosphate particles stimulate interleukin-1β release from human vascular smooth muscle cells: A role for spleen tyrosine kinase and exosome release

AIMS

Calcium phosphate (CaP) particle deposits are found in several inflammatory diseases including atherosclerosis and osteoarthritis. CaP, and other forms of crystals and particles, can promote inflammasome formation in macrophages leading to caspase-1 activation and secretion of mature interleukin-1β (IL-1β). Given the close association of small CaP particles with vascular smooth muscle cells (VSMCs) in atherosclerotic fibrous caps, we aimed to determine if CaP particles affected pro-inflammatory signalling in human VSMCs.

METHODS AND RESULTS

Using ELISA to measure IL-1β release from VSMCs, we demonstrated that CaP particles stimulated IL-1β release from proliferating and senescent human VSMCs, but with substantially greater IL-1β release from senescent cells; this required caspase-1 activity but not LPS-priming of cells. Potential inflammasome agonists including ATP, nigericin and monosodium urate crystals did not stimulate IL-1β release from VSMCs. Western blot analysis demonstrated that CaP particles induced rapid activation of spleen tyrosine kinase (SYK) (increased phospho-Y525/526). The SYK inhibitor R406 reduced IL-1β release and caspase-1 activation in CaP particle-treated VSMCs, indicating that SYK activation occurs upstream of and is required for caspase-1 activation. In addition, IL-1β and caspase-1 colocalised in intracellular endosome-like vesicles and we detected IL-1β in exosomes isolated from VSMC media. Furthermore, CaP particle treatment stimulated exosome secretion by VSMCs in a SYK-dependent manner, while the exosome-release inhibitor spiroepoxide reduced IL-1β release.

CONCLUSIONS

CaP particles stimulate SYK and caspase-1 activation in VSMCs, leading to the release of IL-1β, at least in part via exosomes. These novel findings in human VSMCs highlight the pro-inflammatory and pro-calcific potential of microcalcification.

Chronic Kidney Disease Circulating Calciprotein Particles and Extracellular Vesicles Promote Vascular Calcification: A Role for GRP (Gla-Rich Protein)

OBJECTIVE

Inhibition of mineral crystal formation is a crucial step in ectopic calcification. Serum calciprotein particles (CPPs) have been linked to chronic kidney disease (CKD) calcification propensity, but additional knowledge is required to understand their function, assemblage, and composition. The role of other circulating nanostructures, such as extracellular vesicles (EVs) in vascular calcification is currently unknown. Here, we investigated the association of GRP (Gla-rich protein) with circulating CPP and EVs and the role of CKD CPPs and EVs in vascular calcification.

APPROACH AND RESULTS

Biological CPPs and EVs were isolated from healthy and CKD patients and comparatively characterized using ultrastructural, analytic, molecular, and immuno-based techniques. Our results show that GRP is a constitutive component of circulating CPPs and EVs. CKD stage 5 serum CPPs and EVs are characterized by lower levels of fetuin-A and GRP, and CPPs CKD stage 5 have increased mineral maturation, resembling secondary CPP particles. Vascular smooth muscle cell calcification assays reveal that CPPs CKD stage 5 and EVs CKD stage 5 are taken up by vascular smooth muscle cells and induce vascular calcification by promoting cell osteochondrogenic differentiation and inflammation. These effects were rescued by incubation of CPPs CKD stage 5 with γ-carboxylated GRP. In vitro, formation and maturation of basic calcium phosphate crystals was highly reduced in the presence of γ-carboxylated GRP, fetuin-A, and MGP (matrix gla protein), and a similar antimineralization system was identified in vivo.

CONCLUSIONS

Uremic CPPs and EVs are important players in the mechanisms of widespread calcification in CKD. We propose a major role for cGRP as inhibitory factor to prevent calcification at systemic and tissue levels.

Therapeutic Interference With Vascular Calcification-Lessons From Klotho-Hypomorphic Mice and Beyond

Medial vascular calcification, a major pathophysiological process associated with cardiovascular disease and mortality, involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). In chronic kidney disease (CKD), osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification is mainly driven by hyperphosphatemia, resulting from impaired elimination of phosphate by the diseased kidneys. Hyperphosphatemia with subsequent vascular calcification is a hallmark of klotho-hypomorphic mice, which are characterized by rapid development of multiple age-related disorders and early death. In those animals, hyperphosphatemia results from unrestrained formation of 1,25(OH)₂D₃ with subsequent retention of calcium and phosphate. Analysis of klotho-hypomorphic mice and mice with vitamin D₃ overload uncovered several pathophysiological mechanisms participating in the orchestration of vascular calcification and several therapeutic opportunities to delay or even halt vascular calcification. The present brief review addresses the beneficial effects of bicarbonate, carbonic anhydrase inhibition, magnesium supplementation, mineralocorticoid receptor (MR) blockage, and ammonium salts. The case is made that bicarbonate is mainly effective by decreasing intestinal phosphate absorption, and that carbonic anhydrase inhibition leads to metabolic acidosis, which counteracts calcium-phosphate precipitation and VSMC transdifferentiation. Magnesium supplementation, MR blockage and ammonium salts are mainly effective by interference with osteo-/chondrogenic signaling in VSMCs. It should be pointed out that the, by far, most efficient substances are ammonium salts, which may virtually prevent vascular calcification. Future research will probably uncover further therapeutic options and, most importantly, reveal whether these observations in mice can be translated into treatment of patients suffering from vascular calcification, such as patients with CKD.

Diethyl citrate and sodium citrate reduce the cytotoxic effects of nanosized hydroxyapatite crystals on mouse vascular smooth muscle cells

OBJECTIVE

This study aimed to investigate the damage mechanism of nanosized hydroxyapatite (nano-HAp) on mouse aortic smooth muscle cells (MOVASs) and the injury-inhibiting effects of diethyl citrate (Et2Cit) and sodium citrate (Na3Cit) to develop new drugs that can simultaneously induce anticoagulation and inhibit vascular calcification.

METHODS

The change in cell viability was evaluated using a cell proliferation assay kit, and the amount of lactate dehydrogenase (LDH) released was measured using an LDH kit. Intracellular reactive oxygen species (ROS) and mitochondrial damage were detected by DCFH-DA staining and JC-1 staining. Cell apoptosis and necrosis were detected by Annexin V staining. Intracellular calcium concentration and lysosomal integrity were measured using Fluo-4/AM and acridine orange, respectively.

RESULTS

Nano-HAp decreased cell viability and damaged the cell membrane, resulting in the release of a large amount of LDH. Nano-HAp entered the cells and damaged the mitochondria, and then induced cell apoptosis by producing a large amount of ROS. In addition, nano-HAp increased the intracellular Ca2+ concentration, leading to lysosomal rupture and cell necrosis. On addition of the anticoagulant Et2Cit or Na3Cit, cell viability and mitochondrial membrane potential increased, whereas the amount of LDH released, ROS, and apoptosis rate decreased. Et2 Cit and Na3Cit could also chelate with Ca+ to inhibit the intracellular Ca2+ elevations induced by nano-HAp, prevent lysosomal rupture, and reduce cell necrosis. High concentrations of Et2Cit and Na3Cit exhibited strong inhibitory effects. The inhibitory capacity of Na3Cit was stronger than that of Et2Cit at similar concentrations.

CONCLUSION

Both Et2Cit and Na3Cit significantly reduced the cytotoxicity of nano-HAp on MOVASs and inhibited the apoptosis and necrosis induced by nano-HAp crystals. The chelating function of citrate resulted in both anticoagulation and binding to HAp. Et2Cit and Na3Cit may play a role as anticoagulants in reducing injury to the vascular wall caused by nano-HAp.

Worsening calcification propensity precedes all-cause and cardiovascular mortality in haemodialyzed patients

A novel in-vitro test (T₅₀-test) assesses ex-vivo serum calcification propensity which predicts mortality in HD patients. The association of longitudinal changes of T₅₀ with all-cause and cardiovascular mortality has not been investigated. We assessed T₅₀ in paired sera collected at baseline and at 24 months in 188 prevalent European HD patients from the ISAR cohort, most of whom were Caucasians. Patients were followed for another 19 [interquartile range: 11–37] months. Serum T₅₀ exhibited a significant decline between baseline and 24 months (246 ± 64 to 190 ± 68 minutes; p < 0.001). With serum Δ-phosphate showing the strongest independent association with declining T₅₀ (r = −0.39; p < 0.001) in multivariable linear regression. The rate of decline of T₅₀ over 24 months was a significant predictor of all-cause (HR = 1.51 per 1SD decline, 95% CI: 1.04 to 2.2; p = 0.03) and cardiovascular mortality (HR = 2.15; 95% CI: 1.15 to 3.97; p = 0.02) in Kaplan Meier and multivariable Cox-regression analysis, while cross-sectional T₅₀ at inclusion and 24 months were not. Worsening serum calcification propensity was an independent predictor of mortality in this small cohort of prevalent HD patients. Prospective larger scaled studies are needed to assess the value of calcification propensity as a longitudinal parameter for risk stratification and monitoring of therapeutic interventions.

Delivery of the autofluorescent protein R-phycoerythrin by calcium phosphate nanoparticles into four different eukaryotic cell lines (HeLa, HEK293T, MG-63, MC3T3): Highly efficient, but leading to endolysosomal proteolysis in HeLa and MC3T3 cells

Nanoparticles can be used as carriers to transport biomolecules like proteins and synthetic molecules across the cell membrane because many molecules are not able to cross the cell membrane on their own. The uptake of nanoparticles together with their cargo typically occurs via endocytosis, raising concerns about the possible degradation of the cargo in the endolysosomal system. As the tracking of a dye-labelled protein during cellular uptake and processing is not indicative of the presence of the protein itself but only for the fluorescent label, a label-free tracking was performed with the red-fluorescing model protein R-phycoerythrin (R-PE). Four different eukaryotic cell lines were investigated: HeLa, HEK293T, MG-63, and MC3T3. Alone, the protein was not taken up by any cell line; only with the help of calcium phosphate nanoparticles, an efficient uptake occurred. After the uptake into HeLa cells, the protein was found in early endosomes (shown by the marker EEA1) and lysosomes (shown by the marker Lamp1). There, it was still intact and functional (i.e. properly folded) as its red fluorescence was detected. However, a few hours after the uptake, proteolysis started as indicated by the decreasing red fluorescence intensity in the case of HeLa and MC3T3 cells. 12 h after the uptake, the protein was almost completely degraded in HeLa cells and MC3T3 cells. In HEK293T cells and MG-63 cells, no degradation of the protein was observed. In the presence of Bafilomycin A1, an inhibitor of acidification and protein degradation in lysosomes, the fluorescence of R-PE remained intact over the whole observation period in the four cell lines. These results indicate that despite an efficient nanoparticle-mediated uptake of proteins by cells, a rapid endolysosomal degradation may prevent the desired (e.g. therapeutic) effect of a protein inside a cell.

Live-cell imaging to compare the transfection and gene silencing efficiency of calcium phosphate nanoparticles and a liposomal transfection agent

The processing of DNA (for transfection) and short interfering RNA (siRNA; for gene silencing), introduced into HeLa cells by triple-shell calcium phosphate nanoparticles, was followed by live-cell imaging. For comparison, the commercial liposomal transfection agent Lipofectamine was used. The cells were incubated with these delivery systems, carrying either enhanced green fluorescent protein (eGFP)-encoding DNA or siRNA against eGFP. In the latter case, HeLa cells that stably expressed eGFP were used. The expression of eGFP started after 5 h in the case of nanoparticles and after 4 h in the case of Lipofectamine. The corresponding times for gene silencing were 5 h (nanoparticles) and immediately after incubation (Lipofectamine). The expression of eGFP was notably enhanced 2-3 h after cell division (mitosis). In general, the transfection and gene silencing efficiencies of the nanoparticles were lower than those of Lipofectamime, even at a substantially higher dose (factor 20) of nucleic acids. However, the cytotoxicity of the nanoparticles was lower than that of Lipofectamine, making them suitable vectors for in vivo application.

Protein-drug nanoconjugates: Finding the alternative proteins as drug carrier

Present study was conducted to establish the interaction of bovine fetuin-A to validate its binding modalities with doxorubicin (Dox). Fetuin-A was purified to highest purity and monodispersity. Green synthesis of fetuin-A conjugated gold nanoparticles (F-GNPs) has been performed giving typical UV-maxima with subtle variation in fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) revealed spherical shaped, polydisperse F-GNPs of varying sizes, complementing the radius of hydration (19.5-62.4nm) by dynamic light scattering (DLS). Circular dichroism (CD) analysis of fetuin-A with respect to Dox interaction shows remarkable reduction in ellipticity with increasing concentrations of Dox (20-120μM). Fetuin-A:Dox and F-GNPs:Dox at variable concentrations revealed significantly enhanced absorption spectra, while a continuous decrease in florescence (560nm). This effect was more drastic when Dox interact with fetuin-A as compared to F-GNPs. Some known antimicrobial drugs were also investigated under similar conditions, giving strong quenching effect in a dose dependent manner suggesting the significant yet differential interactions. In cytotoxicity assay, fetuin-A:Dox conjugates revealed less toxicity as compared to F-GNPs:Dox and Dox alone. In-silico studies of the fetuin-A:Dox complex suggest that the drug binds in the major grove between beta-sheet and long loop region of D1 domain and stabilized by several hydrogen bonds.

Prothrombin Loading of Vascular Smooth Muscle Cell-Derived Exosomes Regulates Coagulation and Calcification

OBJECTIVE

The drug warfarin blocks carboxylation of vitamin K-dependent proteins and acts as an anticoagulant and an accelerant of vascular calcification. The calcification inhibitor MGP (matrix Gla [carboxyglutamic acid] protein), produced by vascular smooth muscle cells (VSMCs), is a key target of warfarin action in promoting calcification; however, it remains unclear whether proteins in the coagulation cascade also play a role in calcification.

APPROACH AND RESULTS

Vascular calcification is initiated by exosomes, and proteomic analysis revealed that VSMC exosomes are loaded with Gla-containing coagulation factors: IX and X, PT (prothrombin), and proteins C and S. Tracing of Alexa488-labeled PT showed that exosome loading occurs by direct binding to externalized phosphatidylserine (PS) on the exosomal surface and by endocytosis and recycling via late endosomes/multivesicular bodies. Notably, the PT Gla domain and a synthetic Gla domain peptide inhibited exosome-mediated VSMC calcification by preventing nucleation site formation on the exosomal surface. PT was deposited in the calcified vasculature, and there was a negative correlation between vascular calcification and the levels of circulating PT. In addition, we found that VSMC exosomes induced thrombogenesis in a tissue factor-dependent and PS-dependent manner.

CONCLUSIONS

Gamma-carboxylated coagulation proteins are potent inhibitors of vascular calcification suggesting warfarin action on these factors also contributes to accelerated calcification in patients receiving this drug. VSMC exosomes link calcification and coagulation acting as novel activators of the extrinsic coagulation pathway and inducers of calcification in the absence of Gla-containing inhibitors.

Uptake of the proteins HTRA1 and HTRA2 by cells mediated by calcium phosphate nanoparticles

The efficient intracellular delivery of (bio)molecules into living cells remains a challenge in biomedicine. Many biomolecules and synthetic drugs are not able to cross the cell membrane, which is a problem if an intracellular mode of action is desired, for example, with a nuclear receptor. Calcium phosphate nanoparticles can serve as carriers for small and large biomolecules as well as for synthetic compounds. The nanoparticles were prepared and colloidally stabilized with either polyethyleneimine (PEI; cationic nanoparticles) or carboxymethyl cellulose (CMC; anionic nanoparticles) and loaded with defined amounts of the fluorescently labelled proteins HTRA1, HTRA2, and BSA. The nanoparticles were purified by ultracentrifugation and characterized by dynamic light scattering and scanning electron microscopy. Various cell types (HeLa, MG-63, THP-1, and hMSC) were incubated with fluorescently labelled proteins alone or with protein-loaded cationic and anionic nanoparticles. The cellular uptake was followed by light and fluorescence microscopy, confocal laser scanning microscopy (CLSM), and flow cytometry. All proteins were readily transported into the cells by cationic calcium phosphate nanoparticles. Notably, only HTRA1 was able to penetrate the cell membrane of MG-63 cells in dissolved form. However, the application of endocytosis inhibitors revealed that the uptake pathway was different for dissolved HTRA1 and HTRA1-loaded nanoparticles.

Synthetic mimetics of the endogenous gastrointestinal nanomineral: Silent constructs that trap macromolecules for intracellular delivery

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75-150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the endogenous AMCP and show that it has marked capacity to trap macromolecules during formation. Macromolecular capture into AMCP involved incorporation as shown by STEM tomography of the synthetic AMCP particle with 5nm ultra-fine iron (III) oxohydroxide. In vitro, organic cargo-loaded synthetic AMCP was taken up by APCs and tracked to lysosomal compartments. The AMCP itself did not regulate any gene, or modify any gene regulation by its cargo, based upon whole genome transcriptomic analyses. We conclude that synthetic AMCP can efficiently trap macromolecules and deliver them to APCs in a silent fashion, and may thus represent a new platform for antigen delivery.

MICS, an easily ignored contributor to arterial calcification in CKD patients

In chronic kidney disease (CKD), simultaneous mineral and skeleton changes are prevalent, known as CKD-mineral bone disorder (CKD-MBD). Arterial calcification (AC) is a clinically important complication of CKD-MBD. It can increase arterial stiffness, which leads to severe cardiovascular events. However, current treatments have little effect on regression of AC, as its mechanisms are still unclear. There are multiple risk factors of AC, among which Malnutrition-Inflammation Complex Syndrome (MICS) is a new and crucial one. MICS, a combined syndrome of malnutrition and inflammation, generally begins at the early stage of CKD and becomes obvious in end-stage renal disease (ESRD). It was linked to reverse epidemiology and associated with increased cardiovascular mortality in ESRD patients. Recent data suggest that MICS can trigger CKD-MBD and accelerate the course of AC. In this present review, we summarize the recent understanding about the aggravating effects of MICS on AC and discuss the possible underlying mechanisms. A series of findings indicate that targeting MICS will provide a potential strategy for treating AC in CKD.

Nanoparticles as transfection agents: a comprehensive study with ten different cell lines

The performance of transfection agents to deliver nucleic acids into cells strongly depends on the cell type.

The Successful Treatment of Calciphylaxis with Sodium Thiosulfate and Hyperbaric Oxygen in a Non-dialyzed Patient with Chronic Kidney Disease

We present the case of a non-dialyzed patient with chronic kidney disease and biopsy-proven calciphylaxis who presented with painful cutaneous ulcers on both legs. The skin ulcers drastically improved within 6 months after the initiation of hemodialysis, aggressive wound care, the control of a mineral and bone disorder, and the administration of sodium thiosulfate and hyperbaric oxygen therapy. Notably, the patient's serum levels of C-reactive protein and calciprotein particles decreased and her serum albumin and fetuin-A levels increased in parallel with the alleviation of her calciphylaxis. This case highlights the importance of applying combined medical treatment to calciphylaxis and suggests the possible involvement of calciprotein particles in the pathogenesis of calciphylaxis.