Variation in the inflammatory properties of basic calcium phosphate crystals according to crystal type

Abstract

Objective. To determine the inflammatory potential of basic calcium phosphate (BCP) crystals, which have been identified in human joints.Methods. Hydroxyapatite, carbonate apatite, whitlockite, and octacalcium phosphate crystals were injected in rat air pouches. Volume and cellularity of the exudate were measured. Physicochemical properties of the injected BCP crystals were determined, and correlations with the magnitude of induced inflammatory responses were sought.Results. Significant differences were observed among the volumes and white blood cell (WBC) counts of the pouch exudates, based on the various crystal types used to induce inflammation. A strong correlation was demonstrated between the specific surface (SS) area of the injected crystals and the area under the curve for induced WBC count versus time (R2 = 0.88, P = 0.05). Conclusion. The inflammatory potential of BCP crystals appeared to vary according to crystal features. SS area and the Ca:P ratio (which correlates with crystal solubility) influenced inflammatory properties. These results could explain the variable clinical consequences of BCP deposits, and must be taken into account in the choice of apatite ceramics for use as biomaterials. This correlation was observed forVarious basic calcium phosphatc (BCP) crystals (i.c., synthcsizcd under basic pH, as opposed to acidic CP crystals such as brushite) can be identified in human joints, where tolerance of them appears highly variable. Crystal dcposits are usually asymptomatic, but have been considered responsible for acute periarticular (1-3) or articular (43) inflammation, subchondral ( 6 ) or diaphyseal (7) bone erosions, and destructive arthropathies (8).

Basic Calcium Phosphate Crystals Induce Monocyte/Macrophage IL-1β Secretion through the NLRP3 Inflammasome In Vitro

“…We found that all three forms of BCP crystals are capable of stimulating the release of active IL-1b from monocytes and macrophages, with OCP crystals being more inflammatory than either HA or CA forms of BCP. OCP crystals are also more inflammatory in comparison with MSU and CPPD crystals in our assays confirming our previous findings (30). Interestingly, we did observe a reduction in OCP-induced IL-1b release when human monocytes were differentiated into macrophages, extending previous data that showed a change in the inflammatory state of macrophages to MSU when compared with monocytes (35).…”

“…Sterile, pyrogen-free MSU, CPPD, and BCP crystals were synthesized as described previously (7,30). Crystals were suspended in sterile PBS and dispersed by brief sonication.…”

Calcium pyrophosphate dihydrate and basic calcium phosphate crystalinduced arthropathies: Update on pathogenesis, clinical features, and Therapy

“…The nature of the calcification also can play a role in the crystal evolution fashion, because it has been demonstrated that BCP crystals possessed variable inflammatory potential [43]. Recently, Hamada et al [54] reported that calcium deposits in 34 patients with calcific periarthrtis were composed of carbonated apatite.…”

“…These suggested a cell-specific response triggered by calcium-containing crystals. Prudhommeaux et al [43] demonstrated the variation in the inflammatory properties of basic calcium phosphate crystals according to crystal type. The inflammatory potential increased with the specific surface area of the BCP crystals.…”

Untitled

“…Although in certain in vivo experiments an inflammatory reaction was observed after implantation of calcium orthophosphate bioceramics [600][601][602], the general conclusion on using calcium orthophosphates with Ca/P ionic ratio within 1.0 -1.7 is that all types of implants (bioceramics of various porosities and structures, powders or granules) are not only nontoxic but also induce neither inflammatory nor foreign-body reactions [603]. The biological response to implanted calcium orthophosphates follows a similar cascade observed in fracture healing.…”