Department of Integrative Medical Biology, Section for Anatomy, Umeå University, Umeå, Sweden.
Department of Clinical Science, Ophthalmology, Umeå University, Umeå, Sweden.
Invest Ophthalmol Vis Sci. 2018 Jan 1;59(1):539-548. doi: 10.1167/iovs.17-22554.
To investigate the relation between type of motor endplate, acetylcholine receptor (AChR) subunit composition, and fiber types in human extraocular muscles (EOMs).
EOM samples collected from subjects aged 34 to 82 years were serially sectioned and processed for immunohistochemistry, with specific antibodies against different myosin heavy chain (MyHC) isoforms, neurofilament, synaptophysin, and adult epsilon (ε) and fetal gamma (γ) AChR subunits as well as α-bungarotoxin.
A novel type of motor endplate consisting of large, multiterminal en plaque endings was found in human EOMs, in addition to the previously well-described single en plaque and multiple en grappe endplates. Such novel endplates were abundant but exclusively observed in myofibers lacking MyHC slow and fast IIa but containing MyHC extraocular (MyHCeom), isoforms. Multiple en grappe endings were found only in myofibers containing MyHC slow-tonic isoform and contained fetal γ AChR subunit. Adult ε and fetal γ AChR subunits, alone or combined, were found in the multiterminal endplates. Distinct AChR subunits were present in adjacent motor endplates of a given myofiber containing MyHCeom.
Human EOMs have a more complex innervation pattern than previously described, comprising also a novel type of multiterminal motor endplate present in myofibers containing MyHCeom. The heterogeneity in AChR subunit composition in a given myofiber suggests the possible presence of polyneuronal innervation in human EOMs.
研究人类眼外肌（EOM）中运动终板的类型、乙酰胆碱受体（AChR）亚基组成与纤维类型之间的关系。
收集年龄在 34 岁至 82 岁之间的受试者的 EOM 样本，进行连续切片并进行免疫组织化学处理，使用针对不同肌球蛋白重链（MyHC）同工型、神经丝、突触素、成人ε（ε）和胎儿γ（γ）AChR 亚基以及α-银环蛇毒素的特异性抗体。
除了先前描述的单个斑块和多个结节状终板之外，在人类 EOM 中还发现了一种新型的运动终板，由大的、多末端斑块状终末组成。这种新型终板丰富，但仅存在于缺乏 MyHC 慢型和快型 IIa 但含有眼外肌型（MyHCeom）同工型的肌纤维中。多个结节状终板仅存在于含有 MyHC 慢-紧张型同工型的肌纤维中，并含有胎儿γ AChR 亚基。成人ε和胎儿γ AChR 亚基单独或组合存在于多末端终板中。在含有 MyHCeom 的给定肌纤维的相邻运动终板中存在不同的 AChR 亚基。
人类 EOM 的神经支配模式比以前描述的更为复杂，包括存在于含有 MyHCeom 的肌纤维中的新型多末端运动终板。在给定的肌纤维中 AChR 亚基组成的异质性表明人类 EOM 中可能存在多神经元支配。
