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PubMed1984

Cultured human monocytes and fibroblasts solubilize calcium phosphate crystals.

Two rheumatic syndromes associated with deposition of calcium phosphate crystals in soft tissues of the shoulder have prompted us to study the cellular mechanisms of calcium phosphate crystal solubilization. Synthetic 45Ca labeled calcium phosphate crystal aggregates were solubilized by cultured human fibroblasts or monocytes. Such solubilization required crystal cell contact and was inhibited by chloroquine and ammonium. We hypothesize that the mechanism of crystal solubilization involves phagocytosis followed by dissolution in the acidic environment of secondary lysosomes. Study of the mechanism of calcium phosphate solubilization may be important in understanding resorption of extra-osseus as well as osseus calcification. Intracellular release of calcium from calcium phosphate crystals may also explain our previous observation that hydroxyapatite and other calcium-containing crystals are mitogenic stimuli for fibroblasts and synovial cells.

Ammonium Chloride↗
PubMed2006

Basic calcium phosphate crystals: pathways to joint degeneration.

PURPOSE OF REVIEW: Basic calcium phosphate crystals have long been associated with rheumatic syndromes. Although an understanding of the molecular mechanisms involved in generating these pathological effects has been significantly advanced in recent years, it is still incomplete. RECENT FINDINGS: Basic calcium phosphate crystals have been shown to increase prostaglandin E(2) production in human fibroblasts, mediated by the induction of both cyclooxygenases 1 and 2. Basic calcium phosphate crystals have also been found to upregulate IL-1beta in fibroblasts and chondrocytes. The upregulation of inducible nitric oxide synthase and stimulation of nitric oxide production in chondrocytes by octacalcium phosphate crystals has been demonstrated. The involvement of protein kinase C isoforms in basic calcium phosphate crystal-mediated matrix metalloproteinase 1 and 3 expression in human fibroblasts has been clarified. Two pathways are involved: protein kinase Calpha mediates the calcium-dependent pathway, whereas protein kinase Cmu activates the extracellular-regulated kinase pathway in a calcium-independent cascade. In addition, basic calcium phosphate crystals activate the transcription factor Egr-1, an effect that may contribute to the mitogenic effect of these crystals on fibroblasts. SUMMARY: Recent findings have emphasized the potential for basic calcium phosphate crystals to stimulate the production of a variety of inflammatory mediators such as prostaglandin E(2), nitric oxide, IL-1beta and matrix metalloproteinases, and have helped to elucidate the mechanisms of these effects. Such advances are essential for the ongoing search for effective therapies for basic calcium phosphate crystal-associated diseases.

Calcinosis↗
PubMed2006

Use of calcium phosphate cement paste in orbital volume augmentation.

BACKGROUND: The development of calcium phosphate in cement paste form has made its application simplified and easy. In this study, the authors used an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide/hydroxyapatite injectable calcium phosphate cement paste to evaluate its potential use in orbital volume augmentation. METHODS: Five New Zealand white rabbits were used in this study. In each rabbit, the right orbit was directly implanted with calcium phosphate cement in its injectable paste form, and a prehardened form was placed in the left orbit. The orbital roof was approached through a subciliary skin incision and the implant was placed posterior to the globe of the eyeball to push it outward. Measurement of proptosis and intraocular pressure was monitored before and after implantation. The animals were killed after 3 months, and orbit bone-implant samples were taken for histology and microradiography. RESULTS: In both groups, proptosis was induced, 4.2 +/- 0.27 mm in the prehardened group and 3.8 +/- 0.22 mm in the injectable group. These values taken 1 week postimplantation were unchanged until the end of the experiment and were maintained without significant intraocular pressure changes. The implants were well tolerated, and no sign of infection, extrusion, or migration was noted. Histologic analysis showed good biocompatibility and osteoconductivity, and microradiography has confirmed a well-set cement with direct bone union to it. CONCLUSION: These findings therefore indicate that calcium phosphate cement implant, when used as an injectable paste or in its prehardened form, can be a safe, effective material for orbital volume augmentation.

Animals↗
PubMed2005

Ectopic bone formation by microporous calcium phosphate ceramic particles in sheep muscles.

Calcium phosphate ceramics are widely used in bone reconstructive surgery because of their osteconductive properties. However, these materials generally lack osteoinductive properties required to support bone healing in large defects. In this article, we study the osteoinductive potential of calcium phosphate ceramic particles implanted for 6 months into the dorsal muscles of eight adult female sheep. Microporous biphasic calcium phosphate (MBCP) granules of 1-2 mm composed of hydroxyapatite and beta-tricalcium phosphate (60/40) had macropores of 450 microm, micropores of 0.43 microm, and a specific surface area of 1.8 m(2)/g. After 6 months in the back muscles of sheep, the explants composed of MBCP granules were hard and encapsulated by normal muscle tissue. Ectopic bone formation with Haversian structures was observed in close contact with the MBCP granules in histological sections. Back-scattered electron microscopy and micro-computed tomography indicated that approximately 10% of well-mineralized bone with mature osteocytes had formed between or upon the granules. The ectopic bone showed trabeculae bridging the MBCP granules. Both the number and thickness of the trabeculae formed between the MBCP particles were comparable to those measured in spongious bone. The overall results therefore confirmed the presence of mature bone after intramuscular implantation of MBCP granules. The different hypotheses explaining ectopic bone formation induced by MBCP granules are discussed. Synthetic bone substitutes with osteoinductive properties could be used in bone reconstructive surgery.

Animals↗
PubMed1989

Measurement of calcium phosphate crystalluria: influence of pH and osmolality and invariable presence of oxalate.

Calcium phosphate and calcium oxalate urinary crystal concentrations in normal and stone-forming subjects were measured. The urinary crystals were examined by light microscopy and urine samples were analysed for oxalate, pH and osmolality. Calcium phosphate crystal concentrations were clearly related to urine pH but unrelated to urine osmolality. An unexpected finding was co-precipitation of oxalate with calcium phosphate. Consequently, precipitated invariable oxalate increased with rising urinary pH. Possible explanations and implications are discussed.

Calcium Oxalate↗
PubMed2002

Biological and medical significance of calcium phosphates.

The inorganic part of hard tissues (bones and teeth) of mammals consists of calcium phosphate, mainly of apatitic structure. Similarly, most undesired calcifications (i.e. those appearing as a result of various diseases) of mammals also contain calcium phosphate. For example, atherosclerosis results in blood-vessel blockage caused by a solid composite of cholesterol with calcium phosphate. Dental caries result in a replacement of less soluble and hard apatite by more soluble and softer calcium hydrogenphosphates. Osteoporosis is a demineralization of bone. Therefore, from a chemical point of view, processes of normal (bone and teeth formation and growth) and pathological (atherosclerosis and dental calculus) calcifications are just an in vivo crystallization of calcium phosphate. Similarly, dental caries and osteoporosis can be considered to be in vivo dissolution of calcium phosphates. On the other hand, because of the chemical similarity with biological calcified tissues, all calcium phosphates are remarkably biocompatible. This property is widely used in medicine for biomaterials that are either entirely made of or coated with calcium phosphate. For example, self-setting bone cements made of calcium phosphates are helpful in bone repair and titanium substitutes covered with a surface layer of calcium phosphates are used for hip-joint endoprostheses and tooth substitutes, to facilitate the growth of bone and thereby raise the mechanical stability. Calcium phosphates have a great biological and medical significance and in this review we give an overview of the current knowledge in this subject.

Animals↗
PubMedDate not supplied

[Amyotrophic lateral sclerosis: its relationship with thyroid function and phosphate calcium metabolism].

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease involving motor neurons of the spinal cord, brain stem, and motor cortex. Previous studies reported the coexistence of motor neuron disease with thyroid dysfunction and primary hyperparathyroidism. These findings suggested an eventual role of the previously mentioned endocrine disorders and the development of ALS. OBJECTIVE: Identify thyroid dysfunction and changes in mineral metabolism in patients affected by sporadic ALS. PATIENTS AND METHODS: We retrospectively analyzed data from 41 in ward patients from June 1998, to June 2001. All of them were diagnosed with sporadic ALS. The following laboratory test were performed: thyrotropin (TSH), thyroxine (T4), serum calcium, serum phosphate, parathyroid hormone (PTH) and ionic calcium concentrations. RESULTS: None of the studied patients was found to be hyperthyroid. Two patients had elevated TSH and normal T4, these findings suggested subclinical hypothyroidism. Elevated PTH was found in one patient; another had primary hyperparathyroidism. Low serum calcium was found in three patients and elevated phosphate was found in another four. CONCLUSIONS: All these findings do not allow us to assert a pathogenic association between thyroid dysfunction or alteration of phosphate calcium metabolism and ALS.

Adolescent↗
PubMed1998

Mucins and calcium phosphate precipitates additively stimulate cholesterol crystallization.

Human biliary mucin and calcium binding protein (CBP) influence formation of both calcium salt precipitates and cholesterol crystals and colocalize in the center of cholesterol gallstones. We investigated how physiological concentrations of these proteins regulate cholesterol crystallization in model biles, supersaturated with cholesterol and calcium salts, mimicking pathological human bile. Using polarizing light microscopy and nephelometry to assess cholesterol crystallization, the influence of calcium ions and calcium phosphate precipitates in the absence and presence of mucin, CBP, and human serum albumin was determined. Calcium phosphate precipitates stimulated cholesterol crystallization more strongly than soluble calcium. Mucin also stimulated, and with soluble calcium or calcium phosphate precipitates additively increased, the cholesterol crystal mass. In the absence of mucin, only human serum albumin plus CBP, not these proteins individually, decreased the stimulating effect of calcium phosphate precipitates but not of soluble calcium. However, seeding of calcium phosphate precipitates in biles with mucins resulted in near complete cholesterol crystallization within one day whether CBP and HSA were or were not also present. In conclusion, calcium salt precipitates plus human biliary mucins induce rapid and complete crystallization of cholesterol from model biles, little influenced by human biliary calcium binding proteins.

Bile↗
PubMed2007

Control of crystallinity of hydrated products in a calcium phosphate bone cement.

In this study, a calcium phosphate cement (CPC), consisting of partially crystallized calcium phosphate (PCCP), was synthesized. X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electronic microscope (SEM) were used to characterize the cement. The results showed that by changing the ratio of amorphous calcium phosphate (ACP) to PCCP in the cement, hydrated products of controllable crystallinity were obtained. With increase in the relative amount of PCCP, the hydrated products changed gradually from very poor crystallinity with little needle-like hydroxyapatite (Hap) crystallites to relatively high crystallinity with more needle-like Hap crystallites; the compressive strength of the cement increased, and the degradation of the cement decreased. The cement was implanted into the tibia tubercle of healthy mature Zelanian white rabbits and the histological specimens were obtained after 4 and 16 weeks of implantation. The result revealed that this bone cement was biocompatible and showed very early osteoconductive properties. Thus, the CPC has potential for use in orthopedic surgery for filling non- load-bearing bone defects.

Animals↗
PubMed2001

Setting characteristics and mechanical behaviour of a calcium phosphate bone cement containing tetracycline.

Calcium phosphate cements are used for bone defect filling and they may also be used as delivery systems for active agents. The physicochemical behaviour of an ionic cement, with a final composition of hydroxyapatite, containing tetracycline hydrochloride was investigated. Chemical characterisation, X-ray diffraction analysis, compressive strength and tensile strength were performed. It is known that the antibiotic can be adsorbed on calcium phosphate compounds and the presence of chloride ions can strongly influence the behaviour of the cement. Adding more than 1% (w/w) of 95% pure tetracycline hydrochloride in the solid phase led to a cement with poor mechanical properties, but which, in addition to hydroxyapatite, contained residual starting reagents. For this reason, experiments were also performed with tetracycline previously treated with a calcium sulphate solution. Using a treated tetracycline, it was possible to introduce at least 7% (w/w) of active ingredient whilst still allowing the reaction to proceed to completion i.e. the formation of hydroxyapatite with good mechanical properties. Therefore, treating the tetracycline HCI with calcium sulphate solution prior to reaction conserved the activity of the antibiotic, limited the influence of the antibiotic on the cement evolution and retained the physical properties of the cement.

Bone Cements↗
PubMed2003

Resorption patterns of calcium-phosphate cements in bone.

Two calcium phosphate cements, one monophasic and the other biphasic, have been used as bone void filler in a sheep model. The cements were injected into a slot defect in the proximal tibia and into a cylindrical defect in the distal femur. In this study, we focused on the resorption pattern of the two cement formulations and the subsequent biologic reaction. Bone remodeling occurred synchronously with the resorption of the implant material in a creeping substitution process. Cracks and pores in the monophasic cement were filled with osseous tissues. The biphasic cement showed faster resorption of the matrix. The more slowly resorbing granules were surrounded by newly grown bone, thus providing an inverse scaffold for cancellous bone regeneration. In highly loaded areas, the long-term support function of the fixation appears to be critical. Because cortical bridging of the defects was seen in only one case, it can be concluded that calcium-phosphate cements are preferentially suitable as cancellous bone substitute materials.

Animals↗
PubMed2001

Is there a chemical interaction between calcium phosphates and hydroxypropylmethylcellulose (HPMC) in organic/inorganic composites?

Solid composites of calcium phosphates and hydroxypropylmethylcellulose (HPMC) were prepared at temperatures of 121 degrees C. Three biologically relevant calcium phosphates were studied: CaHPO(4). 2H(2)O (DCPD), calcium deficient apatite (CDA), and biphasic calcium phosphate (BCP). Properties of the solid composites obtained were studied with FTIR, X-ray diffraction, and SEM techniques. Special attention was devoted to seeking a possible chemical interaction between calcium phosphates and HPMC. No interaction was found. Thus, HPMC was proven to have no influence on chemical properties of calcium phosphates.

Calcium Phosphates↗
PubMed1996

Transfecting mammalian cells: optimization of critical parameters affecting calcium-phosphate precipitate formation.

DNA-calcium phosphate co-precipitates arise spontaneously in supersaturated solutions. Highly effective precipitates for transfection purposes, however, can be generated only in a very narrow range of physico-chemical conditions that control the initiation and growth of precipitate complexes. The concentrations of calcium and phosphate are the main factors influencing characteristics of the precipitate complex, but other parameters, such as temperature, DNA concentration and reaction time are important as well. An example for this is the finding that almost all of the soluble DNA in the reaction mix can be bound into an insoluble complex with calcium phosphate in <1 min. Extending the reaction time to 20 min results in aggregation and/or growth of particles and reduces the level of expression. With improved protocols we gained better reproducibility and higher efficiencies both for transient and for stable transfections. Up to 60% of cells stained positive for beta-gal and transient production of secreted proteins was improved 5- to 10-fold over results seen with transfections using standard procedures. Similar improvements in efficiency (number of recombinant cell colonies) were observed with stable transfections, using co-transfected marker plasmids for selection. Transient expression levels 2 days after DNA transfer and titers obtained from stable cell lines, emerging weeks later, showed strong correlation.

Animals↗
PubMed1991

Calcium phosphate, bile acids and colorectal cancer.

The biochemical and nutritional studies discussed here are consistent with the model presented in Figure 1. As shown in vitro, bile acids are precipitated by insoluble calcium phosphate. This calcium phosphate dependent precipitation drastically inhibits their cytotoxicity. A diet-induced increase in luminal surfactant concentration stimulates lytic activity of faecal water and intestinal cell damage resulting in an increased proliferation. The increase in luminal surfactant concentration and lytic activity of faecal water can be counteracted by supplemental dietary calcium phosphate. Supplemental calcium in humans increases the formation of insoluble calcium-phosphate-bile acid complexes in faeces, decreases the soluble fatty acid concentration and decreases lytic activity of faecal water. This sequence of effects offers a molecular explanation of the protective effects of supplemental calcium on proliferation as frequently observed (see studies cited above). It should be realised that this chain of evidence still lacks final proof of a preventive effect of dietary calcium on colorectal cancer. Until now, only protective effects on the first stage of development of colorectal cancer (hyperproliferation) have been observed. More well-designed studies in patients and healthy volunteers are needed using a combined biochemical, nutritional and clinical approach to elucidate the complex mechanism of the protective effect of calcium on colon cancer.

Animals↗
PubMed1991

Purification and characterization of a rabbit salivary protein, a potent inhibitor of crystal growth of calcium phosphate salts.

Human saliva is supersaturated with respect to basic calcium phosphate salts but is stabilized by specific macromolecules that inhibit calcium phosphate precipitation. One of the families of inhibitory proteins in human and monkey saliva is the acidic proline-rich proteins. The purpose of this study was to isolate and characterize inhibitors of calcium phosphate precipitation from rabbit parotid saliva. Saliva was fractionated by immunoaffinity chromatography and anion exchange chromatography. Individual fractions were assayed for their ability to inhibit calcium phosphate crystal growth and the fraction associated with the inhibition was purified by repeated anion exchange chromatography, preparative gel electrophoresis and electroelution. A major (APRP) and two minor proteins (AM1, AM2) that were inhibitory were purified. APRP is an acidic proline-rich phospho-glycoprotein and a very potent inhibitor of secondary crystal growth of calcium phosphate as it was active at a concentration of 2 x 10(-8) M in a standard assay. The N-terminal sequence of one APRP was EYENLDGSLAATQNDDD?Q and a clostripain fragment of APRP had the following N-terminal sequence PQHRPPRPGGH-????SPPP?GN???PPP. Although the N-terminal segment of APRP does not resemble that of proline-rich proteins, alignment of the clostripain fragment with the repeat region of such proteins from rat, mouse, monkey and man revealed a high degree of similarity, indicating a structural relationship with the proline-rich protein family.

Amino Acid Sequence↗
PubMed1997

Oral calcium phosphate: a new therapy for Crigler-Najjar disease?

BACKGROUND & AIMS: Calcium phosphate binds unconjugated bilirubin in vitro, and dietary calcium phosphate supplementation reduces the serum bilirubin level in rats with hereditary unconjugated hyperbilirubinemia (Gunn rats). The aim of this study was to evaluate the effect of oral calcium phosphate supplementation on plasma bilirubin levels in patients with Crigler-Najjar disease. METHODS: A placebo-controlled, double-blind, crossover design was used. Eleven patients, 2-42 years of age, participated. The group included 5 patients with type I disease who were all treated with phototherapy and 6 patients with type II disease who were primarily treated with phenobarbital. In addition to plasma bilirubin levels, dietary intake and urinary and fecal excretion of calcium and phosphate were evaluated. RESULTS: A modest but significant decrease in serum bilirubin was observed in patients with type I disease (18% +/- 6%, P = 0.03) but not in patients with type II disease during treatment with calcium phosphate. Urinary output of calcium and phosphate did not change during the treatment period. CONCLUSIONS: Oral calcium phosphate may be a useful adjuvant to photo-therapy in Crigler-Najjar type I disease.

Administration, Oral↗
PubMedDate not supplied

Fructose precipitates calcium phosphate in the kidneys of female rats fed magnesium-deficient diets.

We have previously shown the synergistic interaction between fructose and magnesium (Mg) deficiency on renal calcification of female rats. The purpose of the present study was to determine whether the calcification formed in the kidneys of female rats fed an Mg-deficient fructose diet is due to phosphate or oxalate precipitates of calcium. The rats were divided into two dietary groups: fructose without Mg and starch with Mg. Rats were fed their respective diets for 9 weeks, and 24 h urine was collected for measuring urinary output, pH, Mg and calcium (Ca). The rats were then fasted overnight and after decapitation, blood was immediately collected for measuring plasma Ca and Mg, and the kidneys were removed. Left kidneys were used to determine their Mg and Ca contents, and right kidneys were dissected and fixed in neutral buffered formalin. Formalin-fixed specimens for microscopy were processed in paraffin using conventional procedures. Histochemical analysis was conducted by staining serial paraffin sections with haematoxylin, eosin, PAS-Schiff, alcian blue and trichrome. The sections were stained by the von Kossa method for calcium phosphate and by the silver hydroperoxide method for calcium oxalate. Only calcium phosphate was detected in the corticomedullary junction of the kidneys of female rats fed Mg-deficient fructose. The hypercalcaemia, hypercalciuria, and hypomagnesuria observed in the fructose group may cause calcium phosphate crystallization. A possible mechanism for the interaction between magnesium deficiency, fructose and oestrogen may be through parathyroid hormone which increases tubular fluid Ca and phosphorus (TF[Ca]x[P]). Further studies are required to prove the mechanism proposed here.

Animals↗
PubMed1996

Kinetic study of the setting reaction of a calcium phosphate bone cement.

The setting reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196 degrees C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) alpha-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5O H, whereas DCP did not react significantly; 2) the reaction was nearly finished within 32 h, during which both the reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings.

Bone Cements↗