Genetic factors in the maturation of the canine intervertebral disc.

The composition and structure of the intervertebral discs have been studied in a group of six four-month-old beagles which were full or half-siblings. The animals were raised in identical environment and were comparable weight and size at sacrifice. Collagen, hexosamine, uronic acid, sialic acid and non-collagenous protein analysis (via indirect method) were performed on the nucleus pulposus (NP), transitional zone (TZ) and a annulus fibrosus (AF) of the discs for the lumbo-sacral, lumbar and thoracic spinal levels. Parallel histochemical and morphological examinations of the discs were also performed. The knee joint meniscus, and articular cartilage was also examined for the components described. The results of the analysis for the discs revealed that within this single age group there co-exist two statistically different compositional states. These differences reside largely in the NP and TZ regions and from the analytical values are interpreted as indicating the chondroid and non-chondroid conditions. No such compositional variation was observed for articular cartilage and fibrocartilage (knee joint menisci).