Hall S M, Berry M, Wyse J P
Division of Anatomy and Cell Biology, United Medical School, London, UK.
J Neurocytol. 1992 Jun;21(6):402-12. doi: 10.1007/BF01191505.
We have examined the behaviour in vivo of regenerating PNS axons in the presence of grafts of optic nerve taken from the Browman-Wyse mutant rat. Browman-Wyse optic nerves are unusual because a 2-4 mm length of the proximal (retinal) end of the nerve lacks oligodendrocytes and CNS myelin and therefore retinal ganglion cell axons lying within the proximal segment are unmyelinated and ensheathed by processes of astrocyte cytoplasm. Schwann cells may also be present within some proximal segments. Distally, Browman-Wyse optic nerves are morphologically and immunohistochemically indistinguishable from control optic nerves. When we grafted intact Browman-Wyse optic nerves or 'triplets' consisting of proximal, junctional and distal segments of Browman-Wyse optic nerve between the stumps of freshly transected sciatic nerves, we found that regenerating axons avoided all the grafts which did not contain Schwann cells, i.e., proximal segments which contained only astrocytes; regions of Schwann cell-bearing proximal segments which did not contain Schwann cells; junctional and distal segments (which contained astrocytes, oligodendrocytes and CNS myelin debris). However, axons did enter and grow through proximal segments which contained Schwann cells in addition to astrocytes. Schwann cells were seen within grafts even after mitomycin C pretreatment of sciatic proximal nerve stumps had delayed outgrowth of Schwann cells from the host nerves; we therefore conclude that the Schwann cells which became associated with regenerating axons within the grafts of Browman-Wyse optic nerve were derived from an endogenous population. Our findings indicate that astrocytes may be capable of supporting axonal regeneration in the presence of Schwann cells.
我们研究了在取自布朗曼-怀斯突变大鼠的视神经移植物存在的情况下，周围神经系统（PNS）再生轴突在体内的行为。布朗曼-怀斯视神经不同寻常，因为神经近端（视网膜）端2-4毫米长的一段缺乏少突胶质细胞和中枢神经系统髓鞘，因此位于近端节段内的视网膜神经节细胞轴突无髓鞘，由星形胶质细胞胞质的突起包裹。雪旺细胞也可能存在于一些近端节段。在远端，布朗曼-怀斯视神经在形态学和免疫组织化学上与对照视神经无法区分。当我们将完整的布朗曼-怀斯视神经或由布朗曼-怀斯视神经的近端、连接段和远端段组成的“三联体”移植到新鲜横断的坐骨神经残端之间时，我们发现再生轴突避开了所有不含雪旺细胞的移植物，即仅含星形胶质细胞的近端节段；含雪旺细胞的近端节段中不含雪旺细胞的区域；连接段和远端段（含有星形胶质细胞、少突胶质细胞和中枢神经系统髓鞘碎片）。然而，轴突确实进入并穿过了除星形胶质细胞外还含有雪旺细胞的近端节段。即使在对坐骨神经近端残端进行丝裂霉素C预处理延迟了雪旺细胞从宿主神经长出之后，仍能在移植物中看到雪旺细胞；因此我们得出结论，与布朗曼-怀斯视神经移植物内再生轴突相关的雪旺细胞源自内源性群体。我们的研究结果表明，在有雪旺细胞存在的情况下，星形胶质细胞可能能够支持轴突再生。
