背景:木胸(WB)肌病是世界范围内商业肉鸡中常见的肌病。组织学检查显示,WB肌病伴有胸大肌(PM)损伤。然而,导致肉鸡WB形成的潜在机制尚未完全阐明。本研究旨在探讨缺氧介导的程序性细胞死亡(PCD)在WB肌病形成中的潜在作用。
结果:对对照组(CON)和WB组的PM肌肉进行了组织学检查和生化分析。顶部的胸肌厚度显着增加,中间,在WB组中发现底部(P<0.01),并伴有肌纤维的病理结构损伤。PM肌肉中每根纤维的毛细血管数,以及血液中pO2和sO2的水平,显著降低(P<0.01),而血液中pCO2和TCO2水平显著升高(P<0.05),提示WB组PM肌肉缺氧情况。我们进一步评估了PCD相关通路,包括自噬,凋亡,和坏死,以了解对WB鸟类PM肌肉缺氧条件增强的后果反应。LC3II与LC3I的比率,和自噬相关因子HIF-1α,BNIP3,Beclin1,AMPKα,和ULK1在mRNA和蛋白质水平,均显著上调(P<0.05),提示WB组PM肌肉发生自噬。凋亡指数,以及Bax的表达,Cytc,caspase9和caspase3显著增加(P<0.05),而Bcl-2在受WB影响的PM肌肉中显著降低(P<0.05),表明线粒体途径介导的细胞凋亡的发生。此外,凋亡相关因子RIP1、RIP3和MLKL的表达,以及NF-κB和促炎细胞因子TNF-α,IL-1β,在受WB影响的PM肌肉中,IL-6均显着增强(P<0.05)。
结论:WB肌病减少血液供应并诱导PM肌肉缺氧,与PCD的发生密切相关,包括细胞凋亡,自噬,和肌纤维内的坏死,最终导致肉鸡肌肉异常损伤和WB的发育。
BACKGROUND: Wooden breast (WB) myopathy is a common myopathy found in commercial broiler chickens worldwide. Histological examination has revealed that WB myopathy is accompanied by damage to the pectoralis major (PM) muscle. However, the underlying mechanisms responsible for the formation of WB in broilers have not been fully elucidated. This study aimed to investigate the potential role of hypoxia-mediated programmed cell death (PCD) in the formation of WB myopathy.
RESULTS: Histological examination and biochemical analysis were performed on the PM muscle of the control (CON) and WB groups. A significantly increased thickness of the breast muscle in the top, middle, and bottom portions (P<0.01) was found along with pathological structure damage of myofibers in the WB group. The number of capillaries per fiber in PM muscle, and the levels of pO2 and sO2 in the blood, were significantly decreased (P < 0.01), while the levels of pCO2 and TCO2 in the blood were significantly increased (P < 0.05), suggesting hypoxic conditions in the PM muscle of the WB group. We further evaluated the PCD-related pathways including autophagy, apoptosis, and necroptosis to understand the consequence response to enhanced hypoxic conditions in the PM muscle of birds with WB. The ratio of LC3 II to LC3 I, and the autophagy-related factors HIF-1α, BNIP3, Beclin1, AMPKα, and ULK1 at the mRNA and protein levels, were all significantly upregulated (P < 0.05), showing that autophagy occurred in the PM muscle of the WB group. The apoptotic index, as well as the expressions of Bax, Cytc, caspase 9, and caspase 3, were significantly increased (P < 0.05), whereas Bcl-2 was significantly decreased (P < 0.05) in the WB-affected PM muscle, indicating the occurrence of apoptosis mediated by the mitochondrial pathway. Additionally, the expressions of necroptosis-related factors RIP1, RIP3, and MLKL, as well as NF-κB and the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6, were all significantly enhanced (P < 0.05) in the WB-affected PM muscle.
CONCLUSIONS: The WB myopathy reduces blood supply and induces hypoxia in the PM muscle, which is closely related to the occurrence of PCD including apoptosis, autophagy, and necroptosis within myofibers, and finally leads to abnormal muscle damage and the development of WB in broilers.