The Impact Of Nanometre-sized Joint Prosthesis Wear Particles On Bone Marrow Mesenchymal Stem Cells

Objective After the nanometre-sized wear particles are co-cultured with bone marrow mesenchymal stem cells（BMSCs）,the cytotoxicity and the effects of nanometre-sized wear particles on proliferation and potential of osteogenic differentiation of BMSCs are evaluated.Our purpose is to explore the mechanism of prosthesis loosening after joint replacement surgery and to provide the basis for the improvement and clinical application of joint prosthesis materials.Methods 1)SD rat BMSCs were cultured in vitro through whole bone marrow adherence method,then the observation of cell morphology,flow cytometry for cell surface markers,osteogenic differentiation and adipogenic differentiation was used to identify the cells.2)Ultrahigh molecular weight polyethylene（UHMWPE）and high corss-linked polyethylene（HXLPE）wear particles were prepared through friction test;Cobalt-chromium alloy（Co-Cr）,titanium alloy（Ti）and zirconia ceramic（Zr O₂）wear particles were prepared by DC electric arc plasma method.3)Different nanometre-sized particles were co-cultured with BMSCs for 48 hours,then the qualitative and quantitative analysis of the cytotoxicity of the particles were conducted through calcein staining/pyridine iodide staining and flow cytometry;Different nanometre-sized particles were co-cultured with BMSCs for 4 days,then the cell proliferation was measured every day using the cell counting kit-8;Different nanometre-sized particles were co-cultured with BMSCs under induced osteogenic conditions,then the AKP activity was assayed on the 3rd,6th and 9th day using the AKP assay kit.Results 1)BMSCs were successfully cultured in vitro through the bone marrow adherence method.The obtained cells possessed the biological characteristics of BMSCs.2)Friction test could not prepare the UHMWPE and HXLPE nanometre-sized wear particles which met the experiment requirements.3)On cytotoxicity of BMSCs,the proportion of dead cells in Co-Cr,Ti and ZrO₂ groups were all higher than that in the blank control group.The proportion of dead cells in Co-Cr was the highest,while the proportion of dead cells in ZrO₂ was the lowest,the statistical analysis results showed that there was a significant statistical difference in overall contrasts（P<0.05）;The between-groups contrasts showed that there were significant statistical differences between Co-Cr group with other groups（P<0.05）,while there were no significant statistical difference between Ti group with ZrO₂ group（P>0.05）.4)CCK-8 experiments showed that the absorbance of each group at different measurement time points all showed that the blank control group>ZrO₂ group>Ti group> Co-Cr group,there was a significant statistical difference in overall contrasts（P<0.05）;The between-groups contrasts showed that there were significant statistical differences from the second day to the forth day（P<0.05）.5)The AKP activity of BMSCs in each group was inhibited at each time point,the inhibition effect of Co-Cr particles was the strongest,while the Ti particles was the weakest,the statistical results showed that there was a significant statistical difference in overall contrasts（P<0.05）;The between-groups contrasts showed significant statistical differences in the third day and the ninth day（P<0.05）.Conclusions 1)The nanometre-sized Co-Cr,Ti and ZrO₂ particles all with the cytotoxicity,and with the negative impact on proliferation and osteogenesis differentiation of BMSCs.2)The nanometre-sized Co-Cr particles with the significantly negative impact on cytotoxicity,proliferation and osteogenic differentiation inhibition of BMSCs;There are no significant difference in cytotoxicity between nanometre-sized Ti particles and nanometre-sized ZrO₂ particles;The proliferation inhibition of BMSCs caused by nanometre-sized Ti particles are stronger than nanometre-sized ZrO₂ particles,while the interference effect on osteogenic differentiation of BMSCs is weaker than that of nanometre-sized ZrO₂ particles.