Biochemical and Histomorphometric Response of Gallic Acid on Gene Expression Levels in Annular Puncture-induced Intervertebral Disc Degeneration using Rabbit Model

Intervertebral disc (IVD) degeneration is a complex multifactorial condition arising from changes in disc morphology, extracellular matrix and neurovascular composition. This study investigated the effect of Gallic acid on the histoarchitecture of the intervertebral disc of rabbit subjected to annular puncture. Twenty (20) New Zealand white rabbits were divided into 4 groups (n=5). Group A (non-punctured) received normal saline orally as placebo; Group B underwent annular puncture (punctured control group) and received normal saline orally for 8 weeks; Group C received 500 mg/kg bw of Gallic acid orally for 8 weeks immediately after puncture; Group D received 500 mg/kg bw of Gallic acid orally after 4 weeks post puncture for 4 weeks. After the experimental period, the disc height index, histomorphometric studies, biochemical analysis, gene expression for collagen type I, collagen type II, Aggrecan and Matrix Metaloproteinase-13, and expression level of Bax were measured and analysed. There was a significant difference in disc height index among the punctured-treated groups compared to the punctured non-treated group. The morphology of the intervertebral disc was preserved and significant restoration in the structural architecture of both the nucleus pulposus and annulus fibrosus was observed in group C compared to group B. However, the oxidative stress markers (catalase, superoxide dismutase and glutathione) collagen type II and aggrecan levels were significantly increased with a corresponding decrease in malondialdehyde, collagen type I, Matrix Metaloproteinase-13, and Bcl-2-associated X protein (Bax) levels. Gallic Acid administration prevents and restores annular punctured disc degeneration attributed to its antioxidant and anti-inflammatory potential.

Key Words: gallic acid, intervertebral disc degeneration, gene expression, antioxidant, histology