Mineral trioxide aggregate (MTA) inhibits osteoclastogenesis and osteoclast activation through calcium and aluminum activities.

Abstract

To evaluate the effect(s) of mineral trioxide aggregate (MTA) on in vitro RANKL-mediated osteoclast-dependent bone resorption events and the influence of Ca2+ and Al3+ on the osteoclastogenesis inhibition by MTA. Two types of osteoclast precursors, RAW 264.7 (RAW) cell line or bone marrow cells (obtained from BALB/c mice and stimulated with recombinant (r)macrophage colony stimulation factor (M-CSF), were stimulated with or withoutrecombinant (r) activator of nuclear kappa B ligand (RANKL), in the presence or absence ofMTA for 6 to 8days. White Angelus MTA and Bios MTA (Angelus, Londrina, Paraná, Brazil) were prepared and inserted into capillary tubes (direct contact surface = 0.50mm2 and 0.01mm2). Influence of MTA on these types of osteoclast precursors was measured by the number of differentiated tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells (RAW and bone marrow cells), TRAP enzyme activity (RAW cells), cathepsin K gene expression (RAW cells), and resorptive pit formation (RAW cells) by mature osteoclasts. Besides, RAW cells were also stimulated with Ca2+ and Al3+ to evaluate the influence of theseions on MTA anti-osteoclastogenic potential. In bone marrow and RAW cells, the number of TRAP-positive mature osteoclast cells induced by rRANKL was significantly inhibited by the presence of MTA compared with control rRANKL stimulation without MTA (p < 0.05), along with the reduction of TRAP enzyme activity (p < 0.05) and the low expression of cathepsin K gene (p < 0.05). In contrast, to control mature osteoclasts, the resorption area on dentin was significantly decreased for mature osteoclasts incubated with MTA (p < 0.05). rRANKL-stimulated RAW cells treated with Ca2+ and Al3+ decreased the number of osteoclasts cells. Besides, the aluminum oxide was the dominant suppressor of the osteoclastogenesis process. MTA significantly suppressed RANKL-mediated osteoclastogenesis and osteoclast activity and, therefore, appears able to suppress bone resorption events in periapical lesions. This process might be related to Ca2+ and Al3+ activities. MTA is an important worldwidely acknowleged biomaterial. The knowledge about its molecular activities on osteoclasts might contribute to improving the understanding of itsclinical efficacy.