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Genotoxic parameters of human degenerated intervertebral discs are linked to the pathogenesis of disc degeneration.

BACKGROUND
Degenerative disc disease (DDD) is a prevalent disorder that brings great incapacity and morbidity to the world's population. Its pathophysiology is not fully understood. DNA damage can influence this process, but so far, there have been few studies to evaluate this topic and its true importance in DDD, as well as whether there is a relation between degeneration grade and DNA damage. The objective of this study is to evaluate the degree of damage to the DNA and the relation to the severity of DDD and measure its response to this insult compared to live/dead cell parameters and reactive oxygen species activity in human discs.


METHODS
An experimental study was performed with 15 patients with grade IV or V Pfirrmann classification who underwent spinal surgery. Five patients were operated on two levels, resulting in 20 samples that were submitted to the comet assay to measure DNA damage. Of these, six samples were submitted to flow cytometry, and apoptosis, necrosis, cell membrane integrity, intracellular esterase activity, reactive oxygen species (ROS), caspase 3 and mitochondrial membrane potential were evaluated.


RESULTS
All samples had DNA damage, and the average of index damage (ID) was 78.1 (SD ± 65.11) and frequency damage (FD) was 49.3% (SD ± 26,05%). There was no statistical difference between the Pfirrmann grades and genotoxic damage. Likewise, all samples that underwent flow cytometry showed apoptosis and ROS to many different degrees.


CONCLUSIONS
DNA damage occurs in high-grade degeneration of human discs and contributes to activation of the apoptosis pathway and ROS production that can accelerate disc degeneration.