Ependyma as a possible morphological basis of ischemic preconditioning tolerance in rat spinal cord ischemia model: nestin and Fluoro-Jade B observations.

1. To test our hypothesis that a transient nonlethal ischemic insult benefits the lumbosacral spinal cord ischemic injury, nestin, the marker of proliferating cells, and Fluoro-Jade B, the marker of degenerating cells, were used in rats. Morphological outcome was evaluated after 12-min ischemia versus 12-min ischemia preconditioned by 3-min ischemic period and 30-min recirculation (IPC), in each group followed by 2, 3, and 4 days of posttreatment survival. 2. Twelve-minute ischemia, inducing nestin-positivity in ependyma and reactive astrocytes at the L(1-3) spinal cord segments, shows this region as the viable region of spinal cord in all postischemic survival periods. On the other hand, abundance of Fluoro-Jade B-positive cells, distributed throughout the dorsal horn and intermediate zone of L4-S2 segments, points out the most injured spinal cord region by ischemia. 3. After the same ischemic insult in IPC rats only a few nestin-positive ependymal cell and reactive astrocytes appeared beside the nestin-positive vessels in the lower lumbar and sacral spinal cord segments of all survival periods. The appearance of nestin-positive cells in the spinal cord segments, which "should have been affected" by ischemia indicates protection of this region by the IPC treatment. 4. The number and density evaluation of Fluoro-Jade B fluorescent cells of L4-S2 segments after ischemia and IPC confirmed that degenerating cells were significantly reduced in the IPC rats in all survival periods. 5. Our results showing the immunohistochemical response of epemdyma, committed to the presence of viable tissue, indicate that the ependymal cells may contribute to the ischemic resistance in the IPC rats.