Comparative Study on Osteoconductivity by Synthetic Octacalcium Phosphate and Sintered Hydroxyapatite in Rabbit Bone Marrow

Abstract

Octacalcium phosphate (OCP) is thought to be a precursor of the mineral crystals in biological apatite. Synthetic OCP has been shown to be converted into an apatite structure when implanted in murine calvarial bone, to enhance bone regeneration more than synthetic hydroxyapatite (HA), and to degrade faster than biodegradable beta-tricalcium phosphate. This study was designed to investigate whether OCP implantation enhances the formation and resorption of new bone (remodeling) concomitant with OCP degradation when implanted intramedullary in a rabbit femur for 12 weeks, compared to sintered HA ceramic. Histological and histomorphometric analyses using undecalcified specimens showed that the area of bone apposition was significantly higher on OCP than on HA between 2 and 3 weeks, whereas it subsequently became smaller on OCP than on HA. The area attacked by multinucleated giant cells, including tartrate-resistant acid phosphatase (TRAP)-positive cells, was significantly higher for OCP than for HA at 8 weeks. Radiography revealed resorption of OCP but not of HA. The results disclose some osteoconductive characteristics of synthetic OCP in the bone marrow space: (1) enhancement of bone regeneration at the initial bone apposition stage and (2) stimulation of resorption of the newly formed bone coupled with OCP biodegradation mediated by TRAP-positive osteoclast-like cells. These results suggest that synthetic OCP would be a more useful bone substitute than HA in implant applications where rapid bone formation and concomitant implant resorption are important considerations.

Osteoblastic differentiation of stromal ST-2 cells from octacalcium phosphate exposure via p38 signaling pathway

“…The present study did not provide complete explanation for the adverse effects of the calcium concentration on ST-2 cells. However, the tendency to reduce calcium concentration by OCP surely reflects the in vivo observation that host osteoblastic cells are stimulated by OCP if implanted in bone defects as reported previously 13,48,49) . Pi ions have been found to play multiple roles in maintaining osteoblast-like cells 18) .…”

Stimulatory effect of hydrothermally synthesized biodegradable hydroxyapatite granules on osteogenesis and direct association with osteoclasts

“…In these experiments, HHA was biodegradable in implanted bone tissue, and higher MAR in specimens implanted with HHA might be associated with osteoclastic resorption of HHA. Biphagic calcium phosphate and octacalcium phosphate have also been shown to be resorbed by osteoclasts [20,21]. In addition, it was shown that the amount of newly formed bone in the region implanted with biphagic calcium phosphate or octacalcium phosphate is more than that of HA using animal models [12,22].…”

The impact of octacalcium phosphate on the dynamics of bone matrix formation in experimental bone defects

“…Исследования in vivo показали, что синтетический ОКФ в мышечных (S. Ban и соавт., 1992), подкожных [20] тканях и на различных костных участках [10,19,20] превращается в биологический апатит. Также было показано, что вслед за резорбцией ОКФ происходит его замещение новой костью [8,10]. Кроме того, было обна-ружено, что покрытие ОКФ на дентальных имплантатах способствует активной остеоинтеграции [4,5], стимулирует пролиферацию остеобластных клеток [6], а в ряде случаев способствует эктопическому остеогенезу [7,21].…”