应用DiI染色晶体对人胚胎视神经发育过程的初步研究

目的：应用Dil(1,1′-dioctadecyl-3,3′,3′-tertamethylin-docarbocyanine perchlorate,一种羰花青染料)染色晶体研究人胚胎视网膜、外侧膝状体、上丘及视皮质间连接的形态学特征和动态发育过程。方法：对不同胎龄的7个胎儿眼球标本进行灌注固定后,分别于标本的视束、上丘臂和视皮质下板层植入Dil染色晶体,以标记来自视网膜和外侧膝状体的轴突。于室温下放置4-10周,等待Dil染色晶体扩散,再根据神经走向切片,通过激光共焦扫描显微镜观察并记录植入Dil染色晶体12-28周的结果。结果：植入Dil染色晶体12周时,胎儿标本的视网膜神经纤维投射已经到达外侧膝状体,但尚未出现分层现象;视网膜神经投射也已达到上丘,纤维位于上丘臂的背侧;视皮质下已出现板层结构。植入22周时视皮质下仍存在板层结构。结论：植入Dil染色晶体12周前,视网膜神经纤维投射已达到外侧膝状体和上丘,视皮质下的板层也已经形成,22周后消失。Dil染色技术能有效地用于研究胚胎期视神经的连续发育过程。

A preliminary study on development of human visual system in fetus by DiI-tracing

OBJECTIVE: To reveal the morphological features and dynamic processes of the development of inter-connections in the retina, lateral geniculate nucleus (LGN), superior colliculus (SC) and visual cortex (VC) in human fetal life by using a fluorescent tracer, 1, 1'-dioctadecyl-3, 3, 3', 3'-tetramethylin-docarbocyanine perchlorate (DiI). METHODS: DiI was embedded into the optic tract, brachium of superior colliculus and subplate of visual cortex in fixed postmortem human tissues of 7 fetuses. The tissue was incubated at 37 degrees C for 4 to 10 weeks (ws). After DiI had satisfactorily diffused via axons of the visual system, the tissue was sectioned, mounted and observed under a confocal laser scanning microscope. RESULTS: In 12 week-fetus, retinogeniculate axon has already reached LGN, but there was no cellular lamination. After embedment, axons from retina arrived at SC, and the fibers were distributed along the dorsal part of the SC. At 12 and 22 ws, there were subplates under visual cortex. CONCLUSION: The retinogeniculate axon reaches LGN before 12 ws and forms cellular lamination after 12 ws. The axon from retina reaches SC before 12 ws. The subplate under visual cortex forms before 12 ws and disappears after 22 ws. DiI can be easily and effectively used to label the axon of visual system of human fetus to study the prenatal development of human visual pathway.