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

1. Purpose

• The objective of this study was to investigate the preventive effects of Amobarbital on the progression of disc degeneration using both ex vivo and in vivo rabbit disc herniation models.

• Specifically, the study aimed to verify whether Amobarbital, which previously demonstrated the ability to inhibit chemically induced oxidative stress, remains effective in an actual injury-induced model.

2. Methods

• Drug Delivery System: Amobarbital was loaded into a composite hydrogel consisting of Pluronic F-127 and Hyaluronic Acid (HA) for local injection. This system was designed to form a gel at body temperature, enabling the sustained release of the drug over a period of 3 to 4 days.

• 
  

• Experimental Models:

  • Ex vivo model: Thoracic and lumbar spine segments were harvested from rabbits, and the nucleus pulposus (NP) was punctured with a 20-gauge needle, followed by culturing for either 2 or 7 days.

  • In vivo model: Degeneration was induced by puncturing the lumbar discs of live rabbits with an 18-gauge needle, with results observed at 2 and 8 weeks post-injury.

  • 
    

• Evaluation Metrics:

  • A histological grading system was applied to score changes in the morphology of the annulus fibrosus (AF), as well as the cellularity and matrix of the NP.

  • Cell death (TUNEL assay, VDAC1 staining) and oxidative stress response (Nrf2 staining) were measured.

  • Radiographic analysis was used to calculate changes in the Disc Height Index (DHI).

3. Results

• Histological Protection: While the control group (hydrogel-only) exhibited severe degeneration, including NP cell clustering and matrix condensation, the Amobarbital-treated group significantly inhibited these degenerative changes.

• Inhibition of Cell Death and Stress: Amobarbital reduced NP cell apoptosis and extended the expression of Nrf2, which responds to oxidative stress, for up to 7 days, demonstrating a potent cytoprotective effect.

• Structural Maintenance: In the in vivo experiments, the Amobarbital-treated group maintained a significantly higher disc height compared to the control group at both the 2-week and 8-week time points.

4. Conclusions

• Local injection of hydrogel-loaded Amobarbital reduced cellular and structural degenerative changes following disc herniation injury.

• Therefore, Amobarbital represents a potential therapeutic option to treat or delay intervertebral disc degeneration (IDD) by specifically targeting oxidative stress.