Changes in Osteopontin Expression in the Rat Lumbar Spinal Cord Following the Avulsion of Lumbar Nerve Roots / 대한해부학회지

ABSTRACT

This study investigated the expression of osteopontin (OPN) in rat lumbar spinal cords after lumbar nerve root avulsion, using in situ hybridization histochemistry, immunocytochemistry and western blot analysis. Cells expressing OPN were motoneurons and interneurons in the ventral horn, but no signals were observed in neurons in the dorsal horn of the normal lumbar spinal cord. From day 1 after avulsion injury, OPN mRNA-labeled neurons increased in the ventral horn and the intermediate zone. By day 3, relatively strong OPN mRNA signals were found throughout the gray matter of the injured side of the spinal cord with OPN mRNA-labeled cells scattered in the superficial dorsal horn. By day 7, the labeling patterns for OPN mRNA were similar to those on day 3, but the numbers of OPN mRNA-labeled cells in the ventral horn and the intermediate zone peaked. At this point, these labeled cells were also more densely packed and the intensity of signals was stronger. Interestingly, these labeled cells were neurons, but not glial cells such as astrocytes or microglia. This OPN mRNA-labeled cell profile in the dorsal horn had nearly disappeared by day 14 after avulsion injury, and the labeling pattern became similar to that on day 1. By day 28, after avulsion injury, the numbers of OPN mRNA-labeled cells decreased further below control values. These results suggest that increased expression of OPN in the rat lumbar spinal cord after avulsion injury might play an important role in the pathogenesis of damaged neurons.