Tscherter Anne, Heidemann Martina, Kleinlogel Sonja, Streit Jürg
Department of Physiology, University of Bern Bern, Switzerland.
Front Cell Neurosci. 2016 Sep 21;10:220. doi: 10.3389/fncel.2016.00220. eCollection 2016.
Presently there exists no cure for spinal cord injury (SCI). However, transplantation of embryonic tissue into spinal cord (SC) lesions resulted in axon outgrowth across the lesion site and some functional recovery, fostering hope for future stem cell therapies. Although evidence for functional recovery is given, the exact cellular mechanism of the graft support remains elusive: either the grafted cells provide a permissive environment for the host tissue to regenerate itself or the grafts actually integrate functionally into the host neuronal network reconnecting the separated SC circuits. We tested the two hypotheses in an SC lesion model that is based on propagation of activity between two rat organotypic SC slices in culture. Transplantation of dissociated cells from E14 rat SC or forebrain (FB) re-established the relay of activity over the lesion site and thus, provoked functional regeneration. Combining patch-clamp recordings from transplanted cells with network activity measurements from the host tissue on multi-electrode arrays (MEAs) we here show that neurons differentiate from the grafted cells and integrate into the host circuits. Optogenetic silencing of neurons developed from transplanted embryonic mouse FB cells provides clear evidence that they replace the lost neuronal connections to relay and synchronize activity between the separated SC circuits. In contrast, transplantation of neurospheres (NS) induced neither the differentiation of mature neurons from the grafts nor an improvement of functional regeneration. Together these findings suggest, that the formation of neuronal relays from grafted embryonic cells is essential to re-connect segregated SC circuits.
目前，脊髓损伤（SCI）尚无治愈方法。然而，将胚胎组织移植到脊髓（SC）损伤部位可导致轴突穿过损伤部位生长并实现一定程度的功能恢复，这为未来的干细胞治疗带来了希望。尽管有功能恢复的证据，但移植支持的确切细胞机制仍不清楚：要么移植的细胞为宿主组织自身再生提供了有利环境，要么移植实际上在功能上整合到宿主神经元网络中，重新连接分离的脊髓回路。我们在一个基于培养的两个大鼠脊髓器官型切片之间活动传播的脊髓损伤模型中测试了这两个假设。移植来自E14大鼠脊髓或前脑（FB）的解离细胞重新建立了损伤部位的活动中继，从而引发了功能再生。我们将移植细胞的膜片钳记录与多电极阵列（MEA）上宿主组织的网络活动测量相结合，在此表明移植细胞分化出神经元并整合到宿主回路中。对移植的胚胎小鼠前脑细胞发育而来的神经元进行光遗传学沉默提供了明确证据，表明它们替代了丢失的神经元连接，以中继和同步分离的脊髓回路之间的活动。相比之下，神经球（NS）移植既未诱导移植细胞分化出成熟神经元，也未改善功能再生。这些发现共同表明，移植胚胎细胞形成神经元中继对于重新连接分离的脊髓回路至关重要。
