Pannese E, Procacci P, Berti E, Ledda M
Institute of Histology, Embryology and Neurocytology, University of Milan, Italy.
Anat Embryol (Berl). 1999 Mar;199(3):199-206. doi: 10.1007/s004290050220.
The perikaryal surface of spinal ganglion neurons undergoes dynamic changes throughout life. In particular, numerous slender projections develop and retract continuously from this surface. We showed previously that the outgrowth of these projections, while an intrinsic property of spinal ganglion neurons, is also influenced by the surrounding microenvironment. Since the latter consists of satellite cells and the extracellular matrix, we sought to determine the relative contributions of each of these components to the outgrowth of perikaryal projections. To this end, we took advantage of a little known characteristic of the satellite cell sheaths: in the rabbit, these sheaths can exhibit gaps that leave the nerve cell body surface directly exposed to the extracellular matrix. We compared the surface domains covered by satellite cells with those in direct contact with the extracellular matrix. We found that the perikaryal projections are abundant in the former domains but are absent in the latter. We also found that the perineuronal extracellular matrix of rabbit spinal ganglia contains laminin and fibronectin, two glycoproteins that have been reported to promote the growth of axonal processes from sensory ganglion neurons. Laminin and fibronectin were also present at the level of the gaps in the satellite cell sheath. These results: (1) provide additional evidence that environmental factors influence the outgrowth of perikaryal projections from spinal ganglion neurons; (2) suggest that satellite cells permit the outgrowth of these projections; (3) suggest that in the spinal ganglia of adult rabbits the perineuronal extracellular matrix is not in itself able to promote the outgrowth of these projections. This study provides a further example of the influence that supporting neuroglial cells have on sensory ganglion neurons.
脊髓神经节神经元的胞体表面在整个生命过程中会经历动态变化。特别是，许多细长的突起不断地从该表面长出和缩回。我们之前表明，这些突起的生长虽然是脊髓神经节神经元的固有特性，但也受到周围微环境的影响。由于后者由卫星细胞和细胞外基质组成，我们试图确定这些成分各自对胞体突起生长的相对贡献。为此，我们利用了卫星细胞鞘鲜为人知的一个特性：在兔子中，这些鞘会出现间隙，使神经细胞体表面直接暴露于细胞外基质。我们比较了卫星细胞覆盖的表面区域和与细胞外基质直接接触的区域。我们发现，胞体突起在前一个区域丰富，但在后一个区域不存在。我们还发现，兔脊髓神经节的神经元周围细胞外基质含有层粘连蛋白和纤连蛋白，这两种糖蛋白已被报道可促进感觉神经节神经元轴突的生长。层粘连蛋白和纤连蛋白也存在于卫星细胞鞘间隙处。这些结果：（1）提供了额外证据，证明环境因素影响脊髓神经节神经元胞体突起的生长；（2）表明卫星细胞允许这些突起生长；（3）表明在成年兔的脊髓神经节中，神经元周围细胞外基质本身并不能促进这些突起的生长。这项研究进一步例证了支持性神经胶质细胞对感觉神经节神经元的影响。
