RESUMO
Aseptic loosening of polymethylmethacrylate (PMMA) fixed prosthesis is characterized by formation of a radiolucent fibrous membrane, accumulation of inflammatory cells and osteolysis. Since this membrane is produced by fibroblasts, it is likely that these connective tissue cells play a critical role in the loosening process. Whether fibroblasts form the radiolucent membrane in response to stimulation by PMMA has not yet been established, nor is it known whether fibroblasts play a role in attracting inflammatory cells to the bone-cement interface by secreting chemical mediators. To address this question, we analyzed the in vitro response of normal human fibroblasts to PMMA. Cells were plated with 10(5)/mL Dulbecco minimal essential medium and were incubated 4 h later with PMMA particles, polystyrene (PS) particles, or medium alone. Proliferative capacity monitored by incorporation of 3H-thymidine was significantly increased following a 48 h exposure to PMMA. Protein synthesis determined by incorporation of 14C-leucine and 14C-proline was also increased. In contrast, levels of secreted prostaglandin (PG) E2 assayed immunoenzymatically was not altered by PMMA. Fibroblasts exposed to control PS did not change their proliferative or protein synthetic activity. Fibroblasts internalized PMMA and PS particles without detectable ultrastructural damage. PMMA enhancement of fibroblast proliferative capacity and protein synthetic ability observed in our in vitro assay system suggests similar effects on fibroblasts in vivo.
