Ratio between osteoprotegerin (OPG) and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) mRNA expression in four cell lines of human gingival fibroblasts (HGF) and periodontal ligament fibroblasts (PDL) stimulated with 10 ng/ml interleukin (IL)-1α with or without 1% cycloheximide (CHX). RNA was extracted from both HGF and PDL, first-strand cDNA synthesis and real-time polymerase chain reaction (PCR) analysis for osteoprotegerin (OPG) and GAPDH was carried out as described in Materials and methods. Data are expressed as a ratio between the amount of OPG and GAPDH mRNA expression ± s.d. of four experiments. An asterisk (*) represents statistical significance ( P
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