Selection of healthy NP tissue based on MRI.

a) Healthy NP tissues exhibiting high signal intensity on T2-weighted MR imaging were selected and were classified as grade 1 by the Pfirrmann Grading System. b–d) Expression of Col1A1, Col2A1, and ACAN in NP tissues according to Pfirrmann’s grades 1–3 and HNP were analyzed using RT-PCR. Grade 3 NP and HNP tissues exhibited significantly higher expression of Col1A1 than did grade1 NP tissues. For Col2A1 and ACAN, there was a significant difference only in HNP (Fig. 1c, d), *p<0.05. d) Histochemical analysis of sections of NP tissues classified according to Pfirrmann’s grades 1–3 and HNP. Grade3 and HNP cells exhibited typical degenerative histological changes. Scale bar: 20 µm.