肌内注射肉毒杆菌毒素A对兔咬肌组织形态学的影响

Histomorphologic evaluation of rabbit masseters with botulinum toxin A

目的:探讨肉毒杆菌毒素A对骨骼肌形态和组织学的影响。方法:25只成年新西兰白兔随机分为5组,每组5只,分别进行2,4,8,12和24周观察,每只实验兔一侧咬肌内注射肉毒杆菌毒素A,另一侧注射生理氯化钠溶液作自身对照,另取5只正常白兔不作任何处理,作为正常对照组。用B超测松弛状态下咬肌厚度,完整切除双侧咬肌称咬肌湿重,并留取部分肌组织做切片进行HE染色、ATP酶染色和NADH-TR(烟酰胺腺嘌呤二核苷四唑还原酶)染色,光镜下观察并进行图像分析。结果:注射内毒杆菌毒素A的给药侧咬肌湿重减轻,厚度变薄,与正常对照与自身对照咬肌比较差异有显著性。给药侧咬肌萎缩程度逐渐加重,至第12周达到最重,第24周时维持与第12周时相近似的水平。切片光镜检查显示给药侧咬肌肌纤维面积减小。ATP酶和NADH-TR染色见给药侧咬肌Ⅱ型肌纤维减小,Ⅱb型纤维更加明显,Ⅰ型纤维无明显变化。正常对照与自身对照侧咬肌的各项指标均无明显差异。结论:内毒杆菌毒素A有肯定的诱导肌萎缩的作用,其肌萎缩主要为Ⅱ型肌纤维,对Ⅰ型肌纤维无明显影响。

Objective： To assess the histomorphologic effect of botulinum toxin A on masseter muscular atrophy of rabbits. Methods：25 New Zealand adult rabbits were randomly 1：1 assigned to one of five observation groups; each group received an intramascular injection of botulinum toxin A at one side of masseter and normal saline at other side of masseter, and subsequently was monitored for 2, 4, 8, 12 or 24 weeks, respectively. Additional 5 healthy rabbits without any injections were used as a normal control. The thickness of the masseters was measured by a B ultrasonic detector. The rabbits were terminated under anesthesia at the corresponding weeks to excise the masseters for weighing, histomorphologic and histochemical evaluations using an optical microscope with HE, ATP enzyme or NADH-TR staining, respectively. Results：The saline-injected masseters were no significantly morphodifference compared to the normal rabbits. Botulinum toxin A-injected masseters showed significant muscular atrophies in respect of reductions of the thickness and wet weight. The optical microscope disclosed that diameters and cross sectional areas of the type Ⅱ muscular fiber were reduced, especially type Ⅱ b fibers. No changes of the diameters and areas of type Ⅰ fibers were found. The degree of muscular atrophies was getting worse at the most at week 12, and suspended the significant worsening after the week 12. Conelusion：Botulinum toxin A is for sure to worsen muscular atrophy on type Ⅱ fibers.