Quantification of inflammatory cellular responses using real-time polymerase chain reaction

The introduction of tissue engineering strategies for the repair and replacement of human body components extends the application and importance of biomaterials. Implanted biomaterials frequently evoke inflammatory responses that are complex and not well understood at present. The goals of this work were to develop improved measurement methods for the quantification of cellular inflammatory responses to biomaterials and obtain data that lead to an enhanced understanding of the ways in which the body responds to the introduction of biomaterials. To evaluate the biocompatibility of materials, we established a system that allows for the analysis and quantitation of cellular inflammatory responses in vitro. In this study, the inflammatory responses of murine macrophages (RAW 264.7) were analyzed. The cells were incubated with polymethylmethacrylate (PMMA) microspheres in the presence and absence of lipopolysaccharide (LPS) at 8 and 18 h. The analysis of the genetic material obtained from the cells was quantitated using real‐time reverse transcription polymerase chain reaction (RT‐PCR). The cell populations treated with LPS or PMMA microspheres singly resulted in an elevation of cytokine levels compared to the untreated control. LPS resulted in a 258‐fold increase, while PMMA resulted in an 87.9‐fold increase at 8 h. RAW 264.7 cells incubated with LPS and PMMA particles demonstrated a synergistic effect by producing a marked increase in the level of cytokine expression, 336‐fold greater than that of the untreated control at 8 h. Fluorescence microscopy studies that assessed cellular viability were also performed and are consistent with the RT‐PCR results. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 305–313, 2004