Cytotoxicity of polymethyl methacrylate cement on primary cultured metastatic spinal cells

Abstract

Polymethyl methacrylate (PMMA) bone cement has been commonly used for percutaneous injection into collapsed vertebral bodies due to malignant tumor. The purpose of this study was to investigate the possible mechanisms of PMMA’s cytotoxcity on primary cultured spinal metastastic cells (SMCs) in vitro. PMMA specimens were prepared in standard discs made of dough and polymerization stages, and the eluates were prepared following the ISO standard. Primary SMCs were obtained and isolated from 7 patients with spinal metastatic tumors undergoing vertebroplasty. Primary cultured SMCs were treated with PMMA specimens of different stages for 24 h, or co-cultured with extracted medium for successive 3 days. The temperatures in two locations from cement discs were recorded by K-type thermocouples. Furthermore, cell proliferation, apoptosis and cycles were determined by MTT and flow cytometry, respectively. The modulation of apoptotic proteins (bcl-2, bax, caspase-3, caspase-8, Fas and PARP) and cell cycle proteins (cyclin D1, P21 and P27) were analyzed by western blot and real time PCR. The results of this study demonstrated that PMMA treatment was able to suppress SMCs proliferation, induce cell apoptosis and inhibit cell cycle arrest when compared to the control group in vitro (P<0.05). Simultaneously, the temperature recorded at the periphery of the PMMA specimen was not high enough to casue thermal injury. Furthermore, molecular markers of apoptosis including Fas, caspase-3 and caspase-9 activated, and Bcl-2/Bax dysregulated in the SMCs with PMMA stimulation. In addition, PMMA treatment showed decreased expression of cyclin D1 that induces cell cycle and increased epxression of inhibitory protein P21, with no significant difference of P27 expression. In summary, the present study confirms that PMMA cement can compromise the vitality and apoptosis of SMCs. This cytotoxic effect may be regulated by the biomarkers Fas, Bcl-2, Bax, caspase-3, caspase-9, cyclin D1 and P21, but not on account of thermal damage.