豚鼠外源性血管内皮细胞生长因子增强内耳屏障转运作用的磁共振成像研究

目的观察血管内皮细胞生长因子(vascularendothelialgrowthfactor, VEGF)能否改变血迷路屏障和血外淋巴屏障的物质转运作用。方法11只300 ~900g雌雄兼并的杂色豚鼠在甲苯噻嗪(16mg/kg)和氯氨酮(60mg/kg)基础麻醉下接受手术,通过圆窗膜(明胶海绵吸附)将VEGF(6耳)或磷酸盐缓冲液(PBS, 5耳)投放至内耳。用T1对比剂二乙烯三胺五乙酸双甲酰胺钆(gadolinium diethylenetriamine pentaacetate bismethylamide, Gd DTPA BMA)作为内耳屏障转运示踪剂,用4 7T场强, 40cm孔径的BrukerBiospecAvance47 /40试验磁共振系统进行豚鼠耳蜗二维磁共振成像观测,用Paravision软件进行图像密度分析,用AdobePhotoshop6 0软件进行图像呈示。结果圆窗膜投放PBS未影响血外淋巴屏障渗透性变化。圆窗膜投放VEGF可显著增强处理侧血外淋巴屏障渗透性,VEGF处理的耳蜗鼓阶内Gd DTPA BMA转运显著增加(P<0 01 ), VEGF处理的耳蜗前庭阶内Gd DTPA BMA转运也显著增加(P<0 01)。VEGF处理的耳蜗中阶内Gd DTPA BMA转运无明显增加(P>0 05)。结论VEGF显著增强血外淋巴屏障的物质转运作用并可能有利于内耳在各种有害环境下的代偿及修复。

MRI evidence of exogenous vascular endothelial growth factor-enhanced transport across inner ear barriers in guinea pigs

Objective Increased vascular endothelial growth factor (VEGF) and VEGF receptor expression is the important biological response under shear stress, ischemia and hypoxia conditions. Mechanical vibration induced cochlea shear stress and trauma obviously upregulate VEGF and VEGF receptor 2 (VEGFR2) expression in the cochlea. To evaluate the possibility of VEGF varying the transport in blood-labyrinth barrier and blood-perilymphatic barrier. Methods Eleven guinea pigs, male and female, weighing from 300 g to 900 g were kept under general anaesthesia with xylazine (16 mg/kg) and ketamine (60 mg/kg) for both drug delivery and MRI measurement. VEGF (6 ears) and phosphate-buffered saline (PBS,5 ears) were delivered to the inner ear via the round window membrane (soaked in gelfoam). The T1 contrast agent gadodiamide (Gd-DTPA-BMA) chelated bound paramagnetic gadolinium was used as the inner ear barrier transportation tracer. A Bruker Biospec Avance 47/40 experimental MRI system with a magnetic field strength of 4.7 Tesla and a 40 cm bore was used for the 2-dimensional cochlea MRI evaluation. The Paravision software was used for image intensity measurement and the Adobe Photoshop 6.0 software was used for image presentation. Results VEGF induced significant Gd uptake in the scala tympani and scala vestibuli, but had little effect on the uptake of Gd in the scala meeia. Conclusions~VEGF significantly increased the transportation of blood-perilymphatic barrier and adapted the inner ear for compensation and repair.