Targeting oxidative stress with amobarbital to prevent intervertebral disc degeneration: part II. Rabbit disc herniation model

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BACKGROUND: Evidence that oxidative stress contributes to the progression of posttraumatic intervertebral disc degeneration suggests targeting oxidant metabolism in disc cells as a strategy to mitigate degeneration in injured discs. We previously identified amobarbital, a drug that suppresses mitochondrial activity in a cell culture model with the chemical induction of oxidative stress, as a promising candidate for this purpose. PURPOSE: The objective of this study was to investigate the preventive effects of amobarbital on the progression of disc degeneration using a rabbit disc herniation model. STUDY DESIGN/SETTING: The effects of amobarbital on the prevention of disc degeneration were evaluated in both ex vivo and in vivo herniated discs. METHODS: Spine motion segments or animals were randomly assigned for intact control, vehicle control (hydrogel only), and amobarbital. Disc herniation was initiated by puncturing the annulus fibrosus with a needle, and amobarbital was delivered to the nucleus pulposus (NP) in a Pluronic F-127/hyaluronic acid hydrogel. A modified histological classification was applied to evaluate for degenerative cellular and matrix changes in both the annulus fibrosus and NP. Additionally, immunohistochemical staining for apoptosis and oxidative stress response, and radiography for disc height index were examined in the ex vivo and in vivo models, respectively. RESULTS: Amobarbital injection allowed uniform distribution in the whole NP and showed sustained release for 3 to 4 days. In an organ culture model, amobarbital treatment after a discal injury prohibited morphologic changes of notochordal cells, structural changes of extracellular matrix, endplate chondrocyte migration, and cell apoptosis compared with the vehicle control. Similarly, the preventive effects of amobarbital on disc degeneration were confirmed in an animal study, especially at 2 weeks, with maintained disc height. CONCLUSIONS: In summary, amobarbital injection loaded in F127/hyaluronic acid hydrogel reduced cellular and structural degenerative changes against herniated discal injuries. Therefore, amobarbital has great potential for treating degenerative disc degeneration. CLINICAL SIGNIFICANCE: Amobarbital encapsulated in hydrogel in this model allowed for effective local delivery into the NP and sustained release of amobarbital, which is promising for potential clinical application. Delivering amobarbital in NP cells may be a therapeutic option to retard intervertebral disc degeneration.

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