Development of intramedullary Schwann cells in irradiated spinal cords of immature rats

Abstract

Intramedullary Schwann cells are observed in the central nervous system in some clinical cases or experimentally following high-dose irradiation. The present study examined the susceptible regions of the spinal cord in induction of Schwann cells by lower doses of irradiation. The spinal cords of three-day-old rats were exposed to X-irradiation at a single dose of 5 Gy or 10 Gy. Each irradiated group was divided into two subgroups: in one the irradiated zone was limited to a 5-mm length of mid-thoracic spinal cord, and in the other the irradiated zone was limited to a 5-mm length of lumbosacral spinal cord. Irradiation-induced development of Schwann cells was observed only in the dorsal funiculi of lumbosacral spinal cord exposed to 10 Gy, but not exposed to 5 Gy, and in the group whose mid-thoracic spinal cord was exposed to 10 Gy. These findings indicated that there was a dose-related effect on developing Schwann cells, and that the occurrence of Schwann cells was influenced by the region of the spinal cord irradiated in immature rats.

髄内シュワン細胞は臨床例や実験的高線量照射後に中枢神経系で観察される。本研究では、低線量照射によるシュワン細胞の誘発における脊髄中の感受性領域を検討した。生後3日のラットの脊髄に5Gyまたは10Gyの線量で1回X線照射した。各照射群を、照射ゾーンを5mm長の中央胸部脊髄に限定したものと、照射ゾーンを5mm長さの腰仙脊髄に限定したものの2群に分けた。シュワン細胞の照射誘発発達は10Gyを照射した腰仙脊髄の背策においてのみ観察され、5Gy照射と中央胸部脊髄の10Gy照射群では見られなかった。この発見により、シュワン細胞の発達には線量に関連した効果があり、シュワン細胞の出現は未熟ラットの照射脊髄部位に影響されることがわかった。