Pathological calcification and replicating calcifying-nanoparticles: general approach and correlation

Transthyretin: From Structural Stability to Osteoarticular and Cardiovascular Diseases

Transthyretin (TTR) is a tetrameric protein transporting hormones in the plasma and brain, which has many other activities that have not been fully acknowledged. TTR is a positive indicator of nutrition status and is negatively correlated with inflammation. TTR is a neuroprotective and oxidative-stress-suppressing factor. The TTR structure is destabilized by mutations, oxidative modifications, aging, proteolysis, and metal cations, including Ca2+. Destabilized TTR molecules form amyloid deposits, resulting in senile and familial amyloidopathies. This review links structural stability of TTR with the environmental factors, particularly oxidative stress and Ca2+, and the processes involved in the pathogenesis of TTR-related diseases. The roles of TTR in biomineralization, calcification, and osteoarticular and cardiovascular diseases are broadly discussed. The association of TTR-related diseases and vascular and ligament tissue calcification with TTR levels and TTR structure is presented. It is indicated that unaggregated TTR and TTR amyloid are bound by vicious cycles, and that TTR may have an as yet undetermined role(s) at the crossroads of calcification, blood coagulation, and immune response.

Destabilised human transthyretin shapes the morphology of calcium carbonate crystals

Human transthyretin (TTR) is a homotetramer that transports thyroid hormones and retinol in the serum and cerebrospinal fluid. TTR is also an intracellular protein found in tissues such as those in the brain, eye and pancreas. TTR is a nutrition marker, reflecting the health of the organism, and TTR levels are linked to the normal and diseased states of the body. The switch from a protective to a pathological role is attributed to the destabilisation of the TTR structure, which leads to tetramer dissociation and amyloid formation. Native and destabilised TTR have been associated with osteoarthritis and bone density in humans. Moreover, TTR is present in eggshell mammillary cones; therefore, we verified the putative TTR engagement in the process of mineral formation. Using an in vitro assay, we found that TTR affected calcium carbonate crystal growth and morphology, producing asymmetric crystals with a complex nanocrystalline composition. The crystals possessed rounded edges and corners and irregular etch pits, suggesting the selective inhibition of crystal growth and/or dissolution imposed by TTR. The occurrence of many porosities, fibrillary inclusions and amorphous precipitates suggested that destabilisation of the TTR structure is an important factor involved in the mineralisation process. Crystals grown in the presence of TTR exhibited the characteristic features of crystals controlled by biomineralisation-active proteins, suggesting novel functions of TTR in the mineral formation process.

Soft tissue calcifications secondary to Hymenoptera stings: a potential prognostic CT imaging sign in pediatric patients

CONTEXT

Soft tissue calcifications (STCs) were incidentally found in some of the Hymenoptera-stung (HS) children when they underwent computed tomography (CT) scans for evaluating complications of vital organs. Afterwards, a predilection of STCs to the children with severe complications was clinically noticed. A hypothesis was then developed that STCs secondary to HS may correlate with poor outcomes.

OBJECTIVE

This study aims to firstly characterize the CT findings of STCs in HS children and to confirm our hypothesis that the occurrence of STCs may act as an indicator of poor outcomes in HS children.

MATERIALS AND METHODS

Children who received CT scanning after Hymenoptera sting from January 2011 to October 2016 in our hospital were analyzed retrospectively. Shape, location, and distribution of the STCs were described according to the CT findings. Then the enrolled cases were classified into Soft Tissue Calcification Group (STCG) and non-Soft tissue Calcification Group (non-STCG) to conduct prognostic comparisons of Sequential Organ Failure Assessment (SOFA) scores, incidence of main complications (acute liver failure (ALF), acute kidney injury stage III (AKI-III) and multiple organ failure (MOF)), length of hospital days, and in-hospital death, respectively. Pearson correlation was also utilized between the cumulative volume of STCs and the SOFA score.

RESULTS

Sixteen cases were enrolled, and STCs' incidence was 56.25% (9/16). Two STCG cases had diffuse nodular calcifications in their swollen subcutaneous tissue, and another seven had symmetrically stripy or patchy calcifications within or along local muscles. The SOFA scores during the first 3 days were all higher in STCG, and rose to the greatest difference at the third day (9.78 ± 2.17 vs. 2.29 ± 2.06, t = 7.009, p < .001); the incidence of ALF, AKI-III and MOF were significantly higher in STCG (66.67% vs. 0, p = .011), (77.78% vs. 0, p = .003) and (77.78% vs. 14.29%, p = .041); and children in STCG were treated with longer hospital durations (26.33 ± 8.41 days vs. 12.29 ± 7.36 days, t = 3.493, p = .004). One child in STCG died of cardiopulmonary failure, and no deaths occurred in non-STCG. No significant correlations presented between STCs cumulative volumes and SOFA score (r_Day1 = 0.096, p = .806; r_Day2 = 0.067, p = .863; r_Day3 = 0.024, p = .950).

CONCLUSION

Soft tissue calcifications detected on CT imaging following multiple Hymenoptera stings in pediatric patients may be a potential prognostic indicator of more severe complications and poorer outcomes.

Calcium orthophosphates (CaPO4): occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO4). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO4, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of CaPO4. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of CaPO4. In addition, natural CaPO4 are the major source of phosphorus, which is used to produce agricultural fertilizers, detergents and various phosphorus-containing chemicals. Thus, there is a great significance of CaPO4 for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Calcium orthophosphates: occurrence, properties, biomineralization, pathological calcification and biomimetic applications

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided.

A red herring in vascular calcification: 'nanobacteria' are protein-mineral complexes involved in biomineralization

Biomineralization at pathological extraosseous sites (i.e. vasculature and soft tissues) is associated with increased morbidity and mortality. So-called 'nanobacteria' have been described as pathogenic agents causing many diseases including calcification. Initially, their appearance, and having a content consisting of nucleic acids plus proteins and properties of growing structures, suggested that they were living organisms. However, it could be demonstrated that the so-called nanobacteria were in fact mineralizing nanoparticles that contain mineral and non-mineral compounds, that these particles bind to charged molecules and that supersaturation enables in vitro growth of these nanoparticles. Recent data indicate that nanoparticles consisting of protein-mineral complexes can be seen both in vitro and in vivo as precursors of matrix calcification.

Fetuin-A regulation of calcified matrix metabolism

The final step of biomineralization is a chemical precipitation reaction that occurs spontaneously in supersaturated or metastable salt solutions. Genetic programs direct precursor cells into a mineralization-competent state in physiological bone formation (osteogenesis) and in pathological mineralization (ectopic mineralization or calcification). Therefore, all tissues not meant to mineralize must be actively protected against chance precipitation of mineral. Fetuin-A is a liver-derived blood protein that acts as a potent inhibitor of ectopic mineralization. Monomeric fetuin-A protein binds small clusters of calcium and phosphate. This interaction results in the formation of prenucleation cluster-laden fetuin-A monomers, calciprotein monomers, and considerably larger aggregates of protein and mineral calciprotein particles. Both monomeric and aggregate forms of fetuin-A mineral accrue acidic plasma protein including albumin, thus stabilizing supersaturated and metastable mineral ion solutions as colloids. Hence, fetuin-A is a mineral carrier protein and a systemic inhibitor of pathological mineralization complementing local inhibitors that act in a cell-restricted or tissue-restricted fashion. Fetuin-A deficiency is associated with soft tissue calcification in mice and humans.

Nanopediatrics: enabling personalized medicine for children

The topic of the special series of reviews in this issue will be nanobiology and nanomedicine, with a focus on the impact of nanotechnology on children and their health; hence, the title of this collection and this introduction, Nanopediatrics: Enabling Personalized Medicine for Children. We will address what is meant when we discuss these nanodisciplines and why we developed a NanoPediatrics Program at University of California, Los Angeles. We will consider the implications of these nanodisciplines for individuals and society. The nature of research, diagnosis, and screening in nanomedicine and nanopediatrics will be illustrated by selected projects in nanodiagnostics and nanotherapeutics by our group and our collaborators, and the combined use of diagnostics and therapeutics in a single nanodevice referred to as "theranostics." We will conclude this introductory review with a summary of the reasons for developing the discipline of nanopediatrics.

Critical evaluation of gamma-irradiated serum used as feeder in the culture and demonstration of putative nanobacteria and calcifying nanoparticles

The culture and demonstration of putative nanobacteria (NB) and calcifying nanoparticles (CNP) from human and animal tissues has relied primarily on the use of a culture supplement consisting of FBS that had been γ-irradiated at a dose of 30 kGy (γ-FBS). The use of γ-FBS is based on the assumption that this sterilized fluid has been rid entirely of any residual NB/CNP, while it continues to promote the slow growth in culture of NB/CNP from human/animal tissues. We show here that γ-irradiation (5–50 kGy) produces extensive dose-dependent serum protein breakdown as demonstrated through UV and visible light spectrophotometry, fluorometry, Fourier-transformed infrared spectroscopy, and gel electrophoresis. Yet, both γ-FBS and γ-irradiated human serum (γ-HS) produce NB/CNP in cell culture conditions that are morphologically and chemically indistinguishable from their normal serum counterparts. Contrary to earlier claims, γ-FBS does not enhance the formation of NB/CNP from several human body fluids (saliva, urine, ascites, and synovial fluid) tested. In the presence of additional precipitating ions, both γ-irradiated serum (FBS and HS) and γ-irradiated proteins (albumin and fetuin-A) retain the inherent dual NB inhibitory and seeding capabilities seen also with their untreated counterparts. By gel electrophoresis, the particles formed from both γ-FBS and γ-HS are seen to have assimilated into their scaffold the same smeared protein profiles found in the γ-irradiated sera. However, their protein compositions as identified by proteomics are virtually identical to those seen with particles formed from untreated serum. Moreover, particles derived from human fluids and cultured in the presence of γ-FBS contain proteins derived from both γ-FBS and the human fluid under investigation—a confusing and unprecedented scenario indicating that these particles harbor proteins from both the host tissue and the FBS used as feeder. Thus, the NB/CNP described in the literature clearly bear hybrid protein compositions belonging to different species. We conclude that there is no basis to justify the use of γ-FBS as a feeder for the growth and demonstration of NB/CNP or any NB-like particles in culture. Moreover, our results call into question the validity of the entire body of literature accumulated to date on NB and CNP.