Correia-Pinto Jorge, Reis Joaquim L, Hutchins Grover M, Baptista Maria J, Estevão-Costa José, Flake Alan W, Leite-Moreira Adelino F
Department of Physiology, Faculty of Medicine, Porto, Portugal, Spain.
J Pediatr Surg. 2002 Mar;37(3):488-92. doi: 10.1053/jpsu.2002.30872.
BACKGROUND/PURPOSE: The rationale for in utero repair of myelomeningocele has been supported experimentally by the observation of preserved neural function after prenatal closure of surgically created defects compared with nonrepaired controls. The mechanism of injury to the exposed neural elements is unknown. Postulated mechanisms include trauma to the herniated neural elements or progressive injury from amniotic fluid exposure as gestation proceeds. A component of amniotic fluid that may contribute to neural injury is meconium. In the current study the effect of human meconium on the exposed spinal cord in a fetal rat model of myelomeningocele was examined.
Twenty time-dated pregnant rats underwent laparotomy at 181/2 days of gestation. The exposed uterus was bathed in ritrodrine for tocolysis. The amniotic cavity was opened over the dorsal midline of the fetal rat, and, under a dissecting microscope (x25), a 2- to 3-level laminectomy was performed. Under magnification (x40), the translucent dura was opened using a 25-gauge needle as a knife. Two fetuses per dam were operated on. In the control group, the amniotic fluid was restored with saline solution, whereas in the experimental group a solution of Human meconium diluted (10%) in saline was used to restore the amniotic fluid. Fetuses were harvested by cesarean section at 211/2 days' gestational age. The liveborn pups were then killed and fixed in 10% formaline. Sections 10 micrometer thick were stained with H&E and studied by light microscopy for evidence of spinal cord injury.
Seven of 20 (35%) experimental rat pups and 6 of 20 (30%) control rat pups were liveborn. All liveborn pups had severe paralysis of the hindlimbs and tail, so that functional differences between the 2 groups could not be detected. Histologic examination of 13 spinal cords at the site of surgical exposure showed that necrosis of neural tissue in 5 of 7 meconium-exposed rat pups was increased when compared with that observed in the 6 fetuses exposed to amniotic fluid without meconium. In general, inflammation was greater and repair processes appeared delayed in meconium-exposed rat pups.
Exposure of the spinal cord of fetal rats to amniotic fluid by surgically created myelomeningocele leads to severe functional impairment. Histologically recognizable necrosis of neural elements was increased in those animals that were exposed to diluted human meconium in the amniotic fluid. The results support the hypothesis that meconium may contribute to the pathophysiology of spinal cord injury observed in myelomeningocele.
背景/目的：与未修复的对照组相比，在手术制造的缺损进行产前闭合后观察到神经功能得以保留，这一实验结果支持了胎儿期修复脊髓脊膜膨出的理论依据。暴露的神经组织的损伤机制尚不清楚。推测的机制包括对突出的神经组织的创伤或随着孕周增加羊水暴露导致的渐进性损伤。羊水的一个可能导致神经损伤的成分是胎粪。在本研究中，检测了人胎粪对脊髓脊膜膨出胎儿大鼠模型中暴露的脊髓的影响。
20只确定孕周的孕鼠在妊娠18.5天时接受剖腹手术。暴露的子宫用利托君冲洗以抑制宫缩。在胎儿大鼠的背侧中线打开羊膜腔，在解剖显微镜（25倍）下进行2至3节段的椎板切除术。在放大倍数（40倍）下，用25号针头当作手术刀打开半透明的硬脑膜。每只孕鼠的2只胎儿接受手术。对照组用盐溶液恢复羊水，而实验组用在盐水中稀释（10%）的人胎粪溶液恢复羊水。在妊娠21.5天时通过剖宫产取出胎儿。然后将存活出生的幼崽处死并固定在10%的甲醛中。10微米厚的切片用苏木精和伊红染色，通过光学显微镜研究脊髓损伤的证据。
20只实验大鼠幼崽中有7只（35%）存活出生，20只对照大鼠幼崽中有6只（30%）存活出生。所有存活出生的幼崽均有严重的后肢和尾巴麻痹，因此无法检测到两组之间的功能差异。对手术暴露部位的13根脊髓进行组织学检查发现，与6只暴露于无胎粪羊水的胎儿相比，7只暴露于胎粪的大鼠幼崽中有5只神经组织坏死增加。一般来说，暴露于胎粪的大鼠幼崽炎症更严重，修复过程似乎延迟。
通过手术制造脊髓脊膜膨出使胎儿大鼠的脊髓暴露于羊水会导致严重的功能损害。在那些羊水中暴露于稀释人胎粪的动物中，神经组织在组织学上可识别的坏死增加。结果支持胎粪可能导致脊髓脊膜膨出中观察到的脊髓损伤病理生理学变化这一假说。
