Department of Oral Biology, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil.
Egas Moniz Center for Interdisciplinary Research (CiiEM), Egas Moniz School of Health & Science, Caparica, Almada, Portugal.
Aesthetic Plast Surg. 2024 Mar;48(5):1037-1044. doi: 10.1007/s00266-023-03572-z. Epub 2023 Aug 24.
It has been reported that botulinum toxin type A (BoNT-A) produces structural changes in masticatory muscles. However, not all histomorphometric parameters affected by BoNT-A parameters have been assessed. This study investigated the histomorphometric changes in the masseter muscle of rats after a single injection of BoNT-A.
Forty-four adult animals were randomly divided into control group (n = 22) and BoNT-A group (n = 22). Controls received a single dose of 0.14 mL/kg of saline in masseter muscles, and the BoNT-A group received a 7 U/Kg of BoNT-A. The groups received the same volume of injected substances. Animals were sacrificed on 7th (n = 5), 14th (n = 5), 21st (n = 5), 28th (n = 4) and 90th (n = 3) days post-treatment. Histological masseter tissue slides were obtained from hematoxylin-eosin treatment and analyzed in optical microscopy regarding muscle cross-sectional area, amount of connective tissue and quantity and diameter of myocytes. For statistical analysis, generalized linear models were used to compare the data (ANOVA). In all test, the significance level of 5% was set.
BoNT-A values of cross-sectional area of the masseter muscle were significantly lower than controls (p < 0.01) throughout the study. Regarding myocytes quantity, BoNT-A subgroups presented higher values than controls (p < 0.0001) since the 14th day until the end of the study; however, the diameter of myocytes was smaller in all BoNT-A subgroups (p < 0.0001) in all assessment points. The amount of connective tissue was higher in BoNT-A subgroups (p < 0.0001) throughout the study.
A single injection of BoNT-A altered the structure of masseter muscle of rats, regarding its histomorphometric parameters.
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据报道，肉毒毒素 A 型（BoNT-A）可使咀嚼肌发生结构改变。然而，并非所有受 BoNT-A 参数影响的组织形态计量学参数都得到了评估。本研究旨在探讨 BoNT-A 单次注射后大鼠咬肌的组织形态计量学变化。
44 只成年大鼠随机分为对照组（n = 22）和 BoNT-A 组（n = 22）。对照组大鼠在咬肌内接受单次 0.14 mL/kg 的生理盐水注射，BoNT-A 组则接受 7 U/kg 的 BoNT-A。两组接受的注射体积相同。动物分别于治疗后第 7、14、21、28 和 90 天处死（n = 5）。从苏木精-伊红处理的咬肌组织切片中获得组织学图像，并在光学显微镜下分析肌肉横截面积、结缔组织量以及肌细胞数量和直径。使用广义线性模型对数据进行比较（方差分析）。所有检验均设定 5%的显著性水平。
BoNT-A 组大鼠咬肌横截面积值在整个研究过程中均显著低于对照组（p < 0.01）。在肌细胞数量方面，BoNT-A 亚组自第 14 天至研究结束时均高于对照组（p < 0.0001）；然而，所有 BoNT-A 亚组的肌细胞直径均较小（p < 0.0001）。BoNT-A 亚组的结缔组织量在整个研究过程中均较高（p < 0.0001）。
单次 BoNT-A 注射可改变大鼠咬肌的结构，影响其组织形态计量学参数。
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