An Intradiscal Injection of Osteogenic Protein-1 Restores the Viscoelastic Properties of Degenerated Intervetebral Discs in the Rabbit Annular Puncture Model

Introduction: Biological approaches for treating degenerative intervertebral disc (IVD) diseases are of great interest. An intradiscal injection of osteogenic protein-1 (OP-1) has been shown to be effective in the structural restoration of the IVD. However, the effect of this approach on the biomechanical properties of the IVD remains unknown. This study was performed to investigate the effects of OP-1 on the viscoelastic properties of IVDs in the rabbit anular-puncture disc degeneration model.

Methods: Disc degeneration was established by anulus fibrosus (AF) puncture (18G) at L2/3 and L4/5 (L3/4: non-punctured controls) in 16 New Zealand White rabbits. Four weeks later each punctured disc received 10 ?l of either 5% lactose or OP-1 (100 ?g). Disc height was radiographically monitored biweekly. Eight weeks after the injection, dynamic viscoelastic properties of the IVDs were tested using uniaxial compression at six frequencies. The IVDs were also analyzed biochemically.

Results: OP-1 injections significantly restored disc height (vs. Lactose, p<0 .001). The elastic modulus of the OP-1-injected IVDs was significantly higher than that in lactose-injected at all frequencies (mean: +43%, p<0.001). viscous (0.05, 0.2, 0.5, and 1 Hz [mean: +55%, p<0.001]) or showed a strong tendency other frequencies. For both moduli, no significant difference observed between control IVDs. OP-1 increased PG content nucleus pulposus (NP) AF (p<0.001) collagen NP. NP contents positive correlation with moduli (Rho="0.36-0.46)."

Discussion: The viscoelastic properties of a degenerated IVD were restored by an injection of OP-1. Correlation analyses suggest that enhanced anabolic activities resulting from the OP-1 injection may influence the biomechanical properties of the IVD.

** The FDA has not cleared a drug and/or medical device described in this presentation (i.e., the drug or medical device is being discussed in an (off-label use.)

Hibbs Award Nominee for Best Basic Science Paper