Effects of HA/ZrO2 composite powder on mesenchymal stem cells proliferation and osteogenic differentiation

Abstract

To evaluate the effects of hydroxyapatite/Zirconiumoxide (HA/ZrO2) composite powder on proliferation and osteogenic differentiation of rabbit mesenchymal stem cells (MSCs) by using molecular biology methods in vitro. HA/ZrO2 composite powder prepared by using powder of HA and ZrO2 with different proportions sintered at 1600°C were compared with pure HA powder and pure ZrO2 powder. The effects of the composite powder suspensions on the proliferation of the rabbit MSCs were measured by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT assay), alkaline phosphatase (ALP) activities were measured by the ALP colorimetric assay, and the cellular expression levels of Collagen I, osteocalcin and osteopontin mRNAs were determined by Reverse Transcription Polymerase Chain Reaction (RT-PCR). The HA phase was transformed into the β-Ca3(PO4)2(β-TCP), α-Ca3(PO4)2 and CaZrO3 phases in the composite powder after sintering at 1600°C, with a positive correlation between the contents of the HA phase and the new phases. The MTT assay showed that both pure HA powder and HA containing composite powder were able to promote cellular proliferation, but pure ZrO2 powder had no effect in stimulating cell proliferation (P<0.05). Vonkossa staining revealed that the composites and pure HA powder were capable of reducing the percentages of positively stained cells. The ALP colorimetric assay demonstrated that the ALP activities of cells maintained in culture media with HA and HA containing composite powder were significantly higher than that of cells cultured in regular media or media containing pure ZrO2 (P<0.05). RT-PCR results showed that the composite powder were able to stimulate the expression of Collagen I and osteocalcin. The HA/ZrO2 composite powder can also facilitate osteogenic differentiation.