Zimmer J, Gähwiler B H
Institute of Anatomy, University of Aarhus, Denmark.
J Comp Neurol. 1987 Oct 1;264(1):1-13. doi: 10.1002/cne.902640102.
In hippocampal slice cultures, the mossy fibers from the dentate granule cells project as normally to cells in the dentate hilus (CA4) and the hippocampal CA3 pyramidal cells. After lesions in vivo and intracerebral transplantation, the mossy fibers can alter their normal distribution within CA3 and even contact CA1 pyramidal cells. The present study examined whether similar changes could be induced in the more simple, virtual two-dimensionally organized slice cultures. For this purpose slices of 7-day-old hippocampi were prepared and subjected to one of the two following manipulations: (1) transection of the mossy fiber layer in CA3 or (2) rearrangement of the geometrical relations between the dentate granule cells in their potential targets (CA3 and CA1) by coculturing dentate slices with CA3 or CA1 slices. Two to 8 weeks later the distribution of the mossy fiber system was visualized by histochemical Timm sulphide silver staining of the terminals. The distribution of the mossy fiber system observed in previous studies of ordinary hippocampal slice cultures was confirmed. In addition, mossy fibers were found to cross the cuts through the mossy fiber layer with formation of a reduced number of characteristic Timm-stained terminals in CA3 distal to the lesion. Close proximity and contiguity of the cut surfaces were important for such growth to occur. Significantly fewer mossy fiber terminals were found when separate slices of dentate and CA3 tissue were joined and grown as cocultures. Similar apposition of slices of dentate and CA1 tissue only rarely resulted in the ingrowth of mossy fibers into CA1. The Timm-stained mossy fiber terminals were then of subnormal size. The results show the potentials of the slice culture technique in supplementing lesion and transplant studies in situ. The growth of mossy fibers across a transection of their pathway is thus a new observation, difficult to demonstrate in the brain. The limited growth in the cocultures of aberrant mossy fibers into Ca1 does, on the other hand, emphasize the importance of close structural contact for the formation of nerve connections, and such contact is apparently more easily obtained in the brain. When the growth of the mossy fibers and that of the cholinergic septohippocampal fibers are compared, it is evident that the cholinergic axons grow better both in vitro and in vivo after lesions and transplantation.
在海马切片培养物中，齿状颗粒细胞的苔藓纤维正常投射至齿状回门区（CA4）的细胞以及海马CA3锥体细胞。在体内损伤和脑内移植后，苔藓纤维可改变其在CA3内的正常分布，甚至与CA1锥体细胞接触。本研究检测了在更为简单的、虚拟二维组织的切片培养物中是否能诱导出类似变化。为此，制备了7日龄海马的切片，并进行以下两种操作之一：（1）横断CA3中的苔藓纤维层；（2）通过将齿状回切片与CA3或CA1切片共培养，重新排列齿状颗粒细胞与其潜在靶标（CA3和CA1）之间的几何关系。2至8周后，通过对终末进行组织化学硫堇银染色来观察苔藓纤维系统的分布。先前对普通海马切片培养物研究中观察到的苔藓纤维系统分布得到了证实。此外，发现苔藓纤维穿过苔藓纤维层的切口，并在损伤远端的CA3中形成数量减少的特征性硫堇染色终末。切口表面的紧密靠近和邻接对于这种生长的发生很重要。当将齿状回和CA3组织的单独切片连接起来作为共培养物生长时，发现苔藓纤维终末明显减少。齿状回和CA1组织切片的类似并置很少导致苔藓纤维长入CA1。然后，硫堇染色的苔藓纤维终末尺寸低于正常。结果显示了切片培养技术在补充原位损伤和移植研究方面的潜力。苔藓纤维穿过其通路的横断处生长是一项新的观察结果，在脑中难以证实。另一方面，异常苔藓纤维在共培养物中向Ca1的有限生长强调了紧密结构接触对于神经连接形成的重要性，而这种接触在脑中显然更容易获得。当比较苔藓纤维与胆碱能海马隔区纤维的生长时，很明显胆碱能轴突在损伤和移植后的体外和体内生长都更好。
