Inflammation and intervertebral disc degeneration in dogs

Abstract

Intervertebral disc (IVD) degeneration is an abnormal, cell-mediated response to progressive structural failure of the IVD. IVD degeneration is more common in chondrodystrophic (CD) dogs than in non-chondrodystrophic (NCD) dogs. In CD dogs IVD degeneration progresses quickly and results in Hansen type I herniation. In NCD dogs degeneration has a gradual character and results in Hansen type II herniation. The Pfirrmann grading system is used to grade IVD degeneration on the basis of magnetic resonance imaging (MRI) findings. The goal of this research is to investigate whether the PGE2 levels in IVDs of dogs suffering from chronic low back pain, are correlated with higher grades of disc degeneration. IVD tissue was collected from canine patients that underwent surgery at the University Clinic for Companion Animals in Utrecht. All the sample IVDs were graded by using the Pfirmann grading system and afterwards the samples were classified in groups on the basis of their Pfirrmann score, NCD/CD classification and the fact whether herniation occurred or not. The PGE2 content, DNA content, protein content and GAG content of the samples were measured. To examine COX-2 protein expression on histological samples, a COX-2 immunohistochemical staining was performed. A difference was found between PGE2/weight ratios and PGE2/DNA ratios, which can be explained by the cellularity of the samples. In this study the weight of the samples appeared to be a better correction factor for the PGE2 content. The PGE2/protein content ratio was not a reliable measure to represent PGE2 contents. The PGE2 content in the NP appeared to be higher than in the AF. Furthermore, our results suggest that the lack of clinical signs is associated with a lower PGE2 content. Our results support findings in literature that the GAG/weight ratio in the NP is negatively correlated with increasing degeneration. A decrease in GAG content was seen in the NP as degeneration increases. We did not find an increase in GAG content in the AF as degeneration increased. Our dataset turned out to be too small to test whether there is a correlation between PGE2 levels and Pfirrmann score. The COX-2 immunohistochemical staining appeared to be not specific enough and needs further optimization before patient samples can be tested.