Figure 5.

Effects of co-administration of growth differentiation factor-6 (GDF-6) and atelocollagen (AC) on radiographic disc height in a rat tail intervertebral disc annular puncture model. A 20-G needle was used to puncture the rat caudal disc at a depth of 5 mm from the skin to the center of nucleus pulposus. The needle was rotated 360° and held in that position for 30 s before extraction to establish an intervertebral disc degeneration model. Following the initial puncture, (a) either vehicle (phosphate-buffered saline [PBS]; 2 μL per disc, group P), atelocollagen (AC; 2-μL AC per disc, group AC), or GDF-6 (20 μg in 2-μL AC gel per disc, group G + AC) or (b) vehicle (PBS; 2 μL per disc, group P′), GDF-6 (20 μg in 2-μL PBS per disc, group G′), or GDF-6 (20 μg in 2-μL AC gel per disc, group G + AC′) was randomly injected. Lateral radiographs of the rat tail were obtained on days 14 and 28 postoperatively, and the disc height index (DHI) was calculated by measuring, averaging, and normalizing the disc height compared to the adjacent vertebral body heights in the anterior, middle, and posterior regions. We designated the control without puncture as 100% (groups C and C′), and compared the four groups (C, P, A, G + AC) and (C′, P′, G′, G + AC′). Data are the mean ± standard deviation (n = 6). One-way analysis of variance with the Tukey–Kramer post-hoc test was used. Significant differences are set as * p < 0.050 and ** p < 0.010.