Whitlockite nanoparticle-coated hydroxyapatite granules for bone regeneration in defect of rat calvaria

Abstract

Background Whitlockite (WH; Ca18Mg2(HPO4)2(PO4)12) as the second most abundant ceramic of human bone after hydroxyapatite (HA; Ca10(PO4)6(OH)2), possessing high osteogenic activity, has been known that it can stimulate osteogenic differentiation as well as suppress osteoclastic activity, particularly, in the preparatory stage of bone regeneration. Methods In this work, we construct a unique ceramic structure by layering WH on the surface of HA granules (HAGs)s via dip-coating and sintering method. Results The cell proliferation of the WH-coated HAGs (WHHAGs) group in the cell counting kit (CCK-8) was about 1.15-fold higher than that of the NT group at 72 h after incubation. The western blot and qPCR results demonstrated that WHHAGs treatment readily stimulated the transcription of osteogenic genes by regulating the downstream signaling pathway of BMP and WNT receptors.This study presents a histological and radiological evaluation of the bone healing potential of the WHHAGs in a 7 mm diameter calvarial bone defect in rats, compared with/without the BMP and non-treated (NT) groups at the 8 weeks after surgery. The bone volume fraction (bone volume/tissue volume) of the WHHAGs group was about 7.32- and 3.56- fold higher than that of the NT group with/without the BMP, respectively. Besides, histological evaluation confirmed that the WHHAGs with BMP promoted bone regeneration. Conclusion These results suggest that the WHHAGs present the remarkable potential for application in dental and orthopedic bone regeneration.