Fig. 1.

(a) Ratio between receptor activator of nuclear factor kappa B ligand (RANKL) 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. RNA was extracted from 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 RANKL and GAPDH mRNA expression ± s.d. of four experiments. An asterisk (*) represents statistical significance (P < 0·05). (b) All the primary HGF (11 cell lines from clinically healthy gingiva and two cell lines from clinically periodontitis gingiva) and PDL (11 cell lines from clinically healthy premolar) cells lines were stimulated with 10 ng/ml IL-1α for 24 h. Production of OPG in cultured supernatant was determined using enzyme-linked immunosorbent assay (ELISA). Data are expressed as concentration of OPG product per cell.