肌硬膜桥的发育解剖学研究

The myodural bridge (MDB) as dense soft tissue communication extends from the deep suboccipital musculatures to the cervical spinal dura mater. Our recent study have provide the evidence for that the MDB is a universal, normal anatomical structure in mammals. Based on our recent study, a novel hypothesis on the physiological function of MDB was proposed that suboccipital muscles might work as a pump via the MDB to provide power for CSF circulation. The hypothesis was confirmed by measuring the changes of cerebrospinal fluid before and after the head rotation experiment. It was also suggested by other researches that the suboccipital muscles reflexive myostatic response could be involved in placing the dura under tension via the MDB. Developmental studies of the fetus and newborn showed that both the lateral ventricles and arachnoid granules developed rapidly after birth; Other studies showed that the suboccipital muscles and MDB play an important role in the regulation of dura mater tension and in keeping the vertical position and movement of the head. Therefore, it is speculated that the head rising of the newborn can change the pressure of the subarachnoid space through the dura mater pulled by MDB, which may promote the development of the cerebral ventricles. The origin and fibrous composition of the adult MDB are clear, however, there is no study on the developmental characteristics and structural evolution of the MDB. In order to clarify the developmental process and the structural characteristics of MDB in different developmental stages, we used the gross and microscopic anatomy, histological techniques et al, to study the MBD of human and SD rat in embryo. The destruction experiment is also carried out in this study. Destroy the MDB complex in suboccipital region of by electrocoagulation, to observe the CSF pressure changes before and after the destroying, and the effects on cerebral ventricular development will be observed. Through these experiment, further to explore the physiological function of musculodural bridge complex.

肌硬膜桥（MDB）是位于枕下区深层的肌肉和硬脊膜之间相连的结缔组织桥，现已证实MDB结构在哺乳动物中普遍存在。本课题组提出MDB可能是脑脊液循环动力来源之一的假说，并通过检测转头实验前后脑脊液流动变化对假说加以证实。胎儿和新生儿发育学研究显示侧脑室和蛛网膜颗粒均于出生后才快速发育；另有研究显示枕下肌和MDB参与硬膜张力的调控，并在头部直立和运动中发挥作用。故推测新生儿的抬头运动可通过MDB牵拉硬脊膜改变蛛网膜下腔压力，这可能对脑室发育有促进作用。成人MDB的结构来源和纤维组成已明确，但MDB的发育及结构演变特点尚无研究。本项目采用大体及显微解剖、组织学染色、小动物成像仪等技术对胚胎期及哺乳期的人及SD大鼠进行研究，揭示MDB的发生、发育过程及结构特点；并通过电凝损耗SD大鼠MDB复合体，观察损毁MDB近期对脑脊液压力的影响以及远期对脑室相关结构发育的影响，探索肌硬膜桥复合体的生理功能。

肌硬膜桥（MDB）是位于枕下区深层的肌肉和硬脊膜之间相连的结缔组织桥，现已证实MDB结构在哺乳动物中普遍存在。本课题组提出MDB可能是脑脊液循环动力来源之一的假说，并通过检测转头实验前后脑脊液流动变化对假说加以证实。胎儿和新生儿发育学研究显示侧脑室和蛛网膜颗粒均于出生后才快速发育；另有研究显示枕下肌和MDB参与硬膜张力的调控，并在头部直立和运动中发挥作用。故推测新生儿的抬头运动可通过MDB牵拉硬脊膜改变蛛网膜下腔压力，这可能对脑室发育有促进作用。本项目采用大体解剖、组织学染色等技术对人胚胎及SD大鼠胚胎进行研究，明确了人胚及SD大鼠胚胎MDB的发育进程及形态变化特点。研究结果：①从发育进程看：人胚胎的MDB发育于始于胚胎15周，于胚胎20-25周已经基本完成；而SD大鼠的MDB发育始于E14天，于出生后7天左右才基本完成。②从结构分化上看：大鼠及人胚的组织分化过程基本相似，MDB结构内的细胞成分均呈现由间充质细胞向成纤维细胞、纤维细胞分化成熟的过程，MDB结构内的纤维成分均为I型胶原纤维成熟的过程。③从蛛网膜颗粒发育及脉络丛发育的过程看，大鼠扫描电镜观察结果显示，E16天后脑脉络丛上皮表面出现分泌泡，蛛网膜颗粒扫描电镜可见出生后3天幼鼠的横窦内出现蛛网膜颗粒结构。④从损毁实验结果分析：SD大鼠枕后区损毁术后3、5、7周后手术模型组与药物模型组大鼠的硬膜外压力均低于假手术组大鼠，且两组大鼠的脉络丛上皮细胞表面微绒毛的高度以及上皮细胞表面的分泌泡、呈火山口样的数量均高于或多于假手术组与空白对照组大鼠。结论：①人胚及大鼠的MDB形态发育有细胞相似性，但存在明显的时空差异；②大鼠脉络丛分泌泡出现于MDB的结构发育起始阶段，而蛛网膜颗粒出现（3d）则在SD大鼠MDB形成期末，脉络丛、蛛网膜颗粒及MDB的发育过程存在时间交集；且MDB损毁大鼠术后3-7周测得脑脊液压力降低，且引起脉络丛上皮分泌泡密度发生改变，进一步证实MDB具有影响脑脊液循环的重要生理功能。本项目阐明了人及SD大鼠MDB的发育过程及各发育时期的形态特征，为进一步开展MDB功能研究提供了发育形态学基础。