An in vitro and in vivo investigation of mellitate and ethane-1-hydroxy-1,1-diphosphonate in calcium phosphate systems

Influence of Soluble Pyrophosphate on Calculus Formation in Adults

The purpose of this double-blind, longitudinal clinical study was to assess the efficacy of a dentifrice containing 3.3% soluble pyrophosphate in inhibiting calculus formation and its effect upon the oral soft tissues. A total of 265 adult volunteers was given a dental prophylaxis. Each was examined for dental calculus and oral soft tissue pathology. The volunteers were then randomly assigned to use either a dentifrice containing soluble pyrophosphate and sodium fluoride or a placebo sodium fluoride formulation for ad libitum home usage. At the two-month completion of the study, 217 subjects were available for examination. The results showed that the group using the dentifrice containing soluble pyrophosphate experienced a significant 26% decrease in calculus formation as compared with the placebo group, with both dentifrices being equally well-tolerated by the oral soft tissues.

Is there a relationship between solubility and resorbability of different calcium phosphate phases in vitro?

BACKGROUND

Does chemistry govern biology or it is the other way around - that is a broad connotation of the question that this study attempted to answer.

METHOD

Comparison was made between the solubility and osteoclastic resorbability of four fundamentally different monophasic calcium phosphate (CP) powders with monodisperse particle size distributions: alkaline hydroxyapatite (HAP), acidic monetite (DCP), β-calcium pyrophosphate (CPP), and amorphous CP (ACP). Results With the exception of CPP, the difference in solubility between different CP phases became neither mitigated nor reversed, but augmented in the resorptive osteoclastic milieu. Thus, DCP, a phase with the highest solubility, was also resorbed more intensely than any other CP phase, whereas HAP, a phase with the lowest solubility, was resorbed least. CPP becomes retained inside the cells for the longest period of time, indicating hindered digestion of only this particular type of CP. Osteoclastogenesis was mildly hindered in the presence of HAP, ACP and DCP, but not in the presence of CPP. The most viable CP powder with respect to the mitochondrial succinic dehydrogenase activity was the one present in natural biological bone tissues: HAP.

CONCLUSION

Chemistry in this case does have a direct effect on biology. Biology neither overrides nor reverses the chemical propensities of inorganics with which it interacts, but rather augments and takes a direct advantage of them.

SIGNIFICANCE

These findings set the fundamental basis for designing the chemical makeup of CP and other biosoluble components of tissue engineering constructs for their most optimal resorption and tissue regeneration response.

Bisphosphonate modulates cementoblast behavior in vitro

BACKGROUND

Cementum formation is deemed to be instrumental for the successful regeneration of periodontal tissues, and thus events and modifiers of cementum formation and mineralization need to be determined. This study aimed to determine whether the bisphosphonate 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) altered the behavior of immortalized cementoblasts (osteocalcin-cementoblasts [OCCM]).

METHODS

OCCM from transgenic mice were exposed to HEBP at concentrations ranging from 0.01 to 10.0 microM. The assays performed included the count of cell number for proliferation, Northern blot analysis for gene expression (up to 10 days for core binding factor alpha-1 [Cbfa1], bone sialoprotein [BSP], osteocalcin [OCN], and osteopontin [OPN], markers for cementoblast/osteoblast maturation/mineralization), von Kossa stain and alizarin red S stain for mineralization, and enzyme assay (p-nitrophenol phosphate cleavage) for alkaline phosphatase (ALP) activity.

RESULTS

Mineral nodule formation was inhibited at the higher doses of HEBP (1.0 and 10.0 microM) only. At early stages (1, 3, and 6 days), gene expression assays revealed only subtle changes in treated cells versus untreated cells, but by day 10, groups treated with lower doses (0.01 and 0.1 microM) were markedly different at the gene expression level. OCN was significantly downregulated (70%) at the lowest dose, with less pronounced effects at higher doses. In concurrence, the master switch gene for osteoblasts, Cbfa1, was also downregulated at the lower doses. Inversely, OPN mRNA was enhanced at the lower doses. ALP activity was not altered by HEBP.

CONCLUSION

Bisphosphonate alters cementoblast function in vitro through the regulation of gene expression and mineral formation.

Effect of 1-hydroxyethylidene-1,1-bisphosphonate on membrane-mediated calcium phosphate formation in model liposomal suspensions

The bisphosphonate, 1-hydroxyethylidene-1,1-bisphosphonate (HEBP), was examined for its effect on calcium phosphate precipitation in pH 7.4, 22 degrees C suspensions of 7:2:1 PC:phosphatidylcholine (PC):dicetylphosphate (DCP):cholesterol (Chol) and 7:1:1 PC:phosphatidylserine (PS):Chol liposomes. HEBP (0.5-50 mumol/l) in the suspending medium had little, if any, effect on precipitation that formed inside phosphate-rich (50 mmol/l) aqueous interiors of liposomes as a result of ionophore (X-537A) driven 2.25 mmol/l Ca2+ influxes from the medium. On the other hand, HEBP had a significant negative impact on the subsequent spread of the precipitate into the surrounding medium when the latter was made metastable with 1.5 mmol/l total inorganic phosphate (PO4). The inhibitory effect of HEBP was more strongly felt in the 7PC:1PS:1Chol liposomal suspensions, with only 1 mumol/l HEBP needed to effectively block extraliposomal precipitation compared to 7.5 mumol/l for 7PC:2DCP:1Chol suspensions. Direct encapsulation of HEBP (1-1000 mumol/l) together with PO4 in the aqueous cores of 7PC:2DCP:1Chol liposomes reduced somewhat (approximately 30%) intraliposomal yields and delayed but did not block extraliposomal precipitate development. These results provide a possible physicochemical explanation for the suppression of matrix vesicle initiated mineralization in ectopically-induced osteoid tissue of HEBP treated mice [1]. In particular, the liposome results suggest that membrane phosphatidylserine interactions with mineral may enhance HEBP's effectiveness in vivo.

Adhesion of carboxylate cements to hydroxyapatite. II. Adsorption of aromatic carboxylates

An investigation was made into the effect of structure and functionality of aromatic carboxylates on their adsorption on to hydroxyapatite (HAP) with a view to identifying factors affecting the adhesion of polyacrylate cements to tooth materials. In general, the amount of carboxylate adsorbed was found to increase with the number of groups contained in the molecule. The arrangement of these groups around the benzene ring also affected adsorption. These results suggested that adsorption was the result of a cooperative effect between carboxylate groups. An adsorption isotherm for mellitate on to HAP was constructed.

Structure-activity relationships (SAR) of hydroxyapatite-binding molecules

Carboxyl-containing molecules can bind to HA with sufficient affinity to prevent the uptake of AZ by this mineral. Structural features that favor binding can be discerned. Isolated carboxyls are inactive; adjacent dicarboxylic functions are marginally active. Crowding of oxygens in the form of vicinal carboxyls or hydroxyls contributes the property of HA binding ability. This property exhibits gradation in magnitude and the variation can be correlated with structural features of the carboxyl-containing molecule. Phospho functions are generally more powerful contributors to HA binding property than are carboxyls.

Effects of N,N,N',N'-ethylenediaminetetramethylene phosphonic acid and 1-hydroxyethylidene-1,1-bisphosphonic acid on calcium absorption, plasma calcium, longitudinal bone growth, and bone histology in the growing rat

Phosphonate compounds are of considerable interest because of their effects on biological mineralization and mineral metabolism. The effects of graded doses given parenterally or orally of N,N,N',N'-ethylenediamine tetramethylene phosphonic acid (EDITEMPA) on calcium absorption, plasma calcium, endochondral bone elongation, and osseous tissue histology of rats were determined. In some experiments 1-hydroxyethylidene-1,1-bisphosphonic acid (HEBP) was included for comparison. Given sc for 7 days, EDITEMPA caused dose-related decreases in net weight gain, intestinal calcium absorption, and longitudinal bone growth. There were also increases in total plasma calcium concentrations and excess osteoid accumulation in bone. When EDITEMPA was given po for 7, 28, or 90 days, few changes in osseous tissues were observed and then only at the highest dose (333 mg/kg/day). An equivalent dose of HEBP caused substantial changes in osseous tissues and calcium parameters.

Effect of diphosphonates on hydroxyapatite formation induced by calcium-phospholipid-phosphate complexes

The diphosphonates disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) and disodium dichloromethylene diphosphonate (Cl2MDP) prevent hydroxyapatite (HA) formation in metastable calcium phosphate solutions, induced by calcium-phospholipid-phosphate complexes and by the acidic phospholipids phosphatidyl serine and phosphatidyl inositol. The diphosphonates appear to act not only as HA crystal poisons but also as surfactants which probably change the nature of the lipid micelle and the charge and conformational properties of the lipid molecules. The surfactants sodium dodecyl sulfate (SDS) and Non-Idet P-40 (NP-40), like the diphosphonates, prevent HA formation by the acidic phospholipids and complexed lipids, but do not act as HA surface poisons. The lipid surfactant lyso-phosphatidyl serine did not induce HA formation from solution. The relevance of the ability of the diphosphonates to act as lipid surfactants to the in vivo use of these agents is discussed.