坐骨神経切断・縫合処置後の末梢神経再生に対するBrain-Derived Neurotrophic Factorの投与効果 : 形態計測学的研究  [in Japanese] The Effect of Brain-Derived Neurotrophic Factor on Elongation of Axons after Transection with Suture Morphometric Evaluation  [in Japanese]

Brain-derived neurotrophic factor (BDNF)は,末梢神経ではシュワン細胞および線維芽細胞で産生され,末梢性運動・感覚ニューロンの生存・維持,発達および障害に伴う修復に重要な役割を果たすと判断される。本研究ではSprague Dawleyラットの坐骨神経を切断後縫合し,組換えヒトBDNF 20 mg/kgを7日間連日皮下投与を行った実験群(n=8)とBDNF溶解液のみを同様に投与した対照群(n=9)を対象とした。切断部位より3 mm遠位部の坐骨神経において,BDNF投与によって末梢神経の再生の早期に生じる軸索の発芽および伸長が促進されるか否かを組織計測学的に検討することを目的とした。両群間で神経束総横断面積,軸索密度(数/mm^2),神経あたりの軸索数(数/神経),軸索直径の最大値および中央値ならびに軸索の直径分布の明らかな差は認められなかった。これらの結果より,本研究の実験条件下ではBDNFが末梢神経線維の再生の早期の軸索の発芽および伸長を促進する作用は明らかでないと判断した。

Brain-derived neurotrophic factor (BDNF) is considered to play an important role in survival, maintenance, development and repair of the peripheral neuron. In this study, the effect of human recombinant BDNF on sprouting and elongation of axons, the early phase of regeneration of nerve fibers, was morphometrically evaluated 7 days following the sciatic nerve transection and juxtaposition of proximal and distal stumps with suture in Sprague-Dawley rats. In the experimental group (test), 20 mg/kg of BDNF was injected subcutaneously every day for seven days in eight rats, starting 30 minutes after the transection. In the control group (control), phosphate buffered-saline alone was injected in nine rats as in the experimental group. The various morphometric parameters were evaluated in the sciatic nerve of each rat of the control and test, 3 mm distal to the site of the transection on light and electron microscopy of Epon-embedded sections. On both light and electron microscopy only a few myelinated fibers with a very thin myelin sheath were found only in one nerve in each of the control and test. However, significant numbers of unmyelinated axons were found in each nerve of the control and test. There were no statistically significant differences in the total fascicular area per nerve, the numbers of myelinated and unmyelinated axons per mm^2 of fascicular area and per nerve, their maximum and median diameters and their size distribution histograms between control and test. In addition, there were no statistically significant differences in the numbers of myelin ovoids per mm^2 of the fascicular area and per nerve, their maximum and median diameters and their size distribution histograms between control and test. Therefore, we concluded that there was no definite evidence that BDNF promoted the sprouting and elongation of axons, the early phase of the regeneration of nerve fibers, at least under this experimental condition.