Expression of msxb and fgf20a during fin regeneration in adult zebrafish (between 6 and 8 months old). A: In situ hybridization of msxb and fgf20a at 0, 24, 48, 72, and 96 hpa, respectively. Dashed lines indicate the plane of amputation. Scale bar = 1 mm. B, C: Real-time RT-PCR analysis of the expression of msxb and fgf20a at different times during regeneration. The expression levels of msxb and fgf20a at 0 hpa (control) were normalized to 1, respectively. Data represents the means ± SE. n = 4 for each measurement. n.s., not significant; *P < 0.05.

Regeneration of the caudal fin in adult zebrafish at different ages. A: Caudal fin growth at 48 hpa. Dashed lines indicate the plane of amputation. Scale bar = 1 mm. B, C: Real-time RT-PCR analysis of the expression of msxb and fgf20a in regenerating fins at 48 hpa in zebrafish at different ages. The expression levels of msxb and fgf20a in 4-month-old animals were normalized to 1, respectively. Data represents the means ± SE. n = 4 for each measurement. n.s., not significant.

Expression of msxb in the caudal fin after amputation. A: In situ hybridization of msxb in the control tissue (immediately after amputation) and in tissues in which the previously formed blastema was removed (second and forth panels) or not completely amputated (third and fifth panels, dashed lines indicate the sites where the previous amputation took place). Scale bar = 1 mm. B: Real-time RT-PCR analysis of the expression of msxb in the caudal fin in the control tissue and in tissues in which the previously formed blastema was removed or not completely amputated. Single asterisk (*) indicates that the blastema formed from the previous amputation was partially removed; **P < 0.005.

Fin regeneration after repeated amputations in adult zebrafish (between 6 and 8 months old). A: Caudal fin growth at 48 hpa. Dashed lines indicate the plane of amputation. Scale bar = 1 mm. B, C: Real-time RT-PCR analysis of the expression of msxb and fgf20a in regenerating caudal fins at 48 hpa. The expression levels of msxb and fgf20a after the first amputation were normalized to 1, respectively. Data represents the means ± SE. n = 4 for each measurement. n.s., not significant.