Fig. 3

Fig. 3

a TRAP, measured by biochemical assay and normalized for scale area, has indicated a progressive increase of the activity in 3-, 6- and 9-month-old fish (3 months vs 9 months, p < 0.001; 6 months vs 9 months, p < 0.001). b Histochemical staining for TRAP activity on aging scales (scale bar = 0.1 mm). TRAP-positive signal has been detected along scale border of 9-month-old fish surrounding a bone resorption area. c Gene expression analysis on aging scales. Real-time PCR for bone-specific genes has shown an increase of tnfrsf1b (homolog of human rank) expression in scales from 6- and 9-month-old fish and an age-dependent downregulation of tnfsf11 and tnfrsf11b (homolog of human rankl and opg) (OPG: 3 months vs 6 months, p < 0.01; 3 months vs 9 months, p < 0.001; 6 months vs 9 months, p < 0.01. RANKL: 3 months vs 6 months, p < 0.01; 3 months vs 9 months, p < 0.001; 6 months vs 9 months, p < 0.01. RANK: 3 months vs 6 months, p < 0.001; 3 months vs 9 months, p < 0.001). d Calculated tnfsf11/tnfrsf11b (rankl/opg) ratio was found unchanged during aging