Pathology and gene expression of the sciatic nerve after non-freezing cold injury

Abstract

Objective To investigate the morphological changes in the sciatic nerve and the dorsal root ganglions (DRGs) and also gene expression in DRGs after non-freezing cold injury, and to explore the molecular mechanism of peripheral nerve cold injury and regeneration. Methods Twenty-four male Wistar rats were used. The sciatic nerve on one side was cooled to 4℃ for 2 h, and the sciatic nerve on the opposite side was exposed, but without cooling. Sciatic nerves and L4, L5 and L6 DRGs from both sides were harvested at the 1st, 2nd and 3rd week after cooling. Any pathological changes were observed using light and electron microscopy. Laser capture microdissection (LCM) was used to investigate the DRG neurons' gene expression. The array result was verified with RT-PCR for eight genes. Results Large fiber degeneration was obvious by the 7th day after cooling. Myelinated fiber regeneration had begun by the 14th day, so this time was chosen to explore the neurons' gene expression. Ninety-six genes and expressed sequence tags (ESTs) were up-regulated greater than 2 fold. Their proteins' functions were classified as adaptive response to external stimulus, apoptosis regulation, cell adhesion, immune and inflammation response,nerve regeneration, pain associated molecules, microtubule cytoskeleton, ion-channels, neurotransmitters and receptors, and neuropeptides. Conclusions A complex molecular mechanism is involved in cold injury and regeneration of the sciatic nerve, and many genes are involved. Large scale microarray analysis is a potent means to screen out related genes, thus suggesting future repair strategies. Key words: Cold injury; Peripheral nerves; Gene expression; Microarrays; Laser capture microdissection