NUCLEUS PULPOSUS PROGENITOR CELL EXHAUSTION IN DISC AGEING AND DEGENERATION: O20.Sakai D; Nakamura, K; Nakai, T; Grad, S; Alini, M; Chan, D; Risbud, M; Masuda, K; Ando, K; Mochida, JSpine Journal Meeting Abstracts: 2013 - Volume - Issue - ppg 14-15 Free