The innervation of the long head of the biceps tendon (LHBT) is not sufficiently documented. This is a drawback since pathologies of the LHBT are a major source of shoulder pain. Thus, the study aimed to characterize structurally and molecularly nervous elements of the LHBT. The proximal part of 11 LHBTs was harvested intraoperatively. There were 8 female and 3 male specimens. Age ranged from 66 to 86 years. For structural analyses, nervous elements were viewed in the transmission electron microscope. For molecular characterization, we used general neuronal markers including antibodies against neurofilament and protein gene product 9.5 (PGP9.5) as well as specific neuronal markers including antibodies against myelin basic protein (MBP), calcitonin gene-related product (CGRP), substance P (SP), tyrosine hydroxylase (TH), and growth-associated protein 43 (GAP43). Anti-neurofilament and anti-PGP9.5 visualized the overall innervation. Anti-MBP visualized myelination, anti-CGRP and anti-SP nociceptive fibers, anti-TH sympathetic nerve fibers, and anti-GAP43 nerve fibers during development and regeneration. Immunolabeled sections were analyzed in the confocal laser scanning microscope. We show that the LHBT contains unmyelinated as well as myelinated nerve fibers which group in nerve fascicles and follow blood vessels. Manny myelinated and unmyelinated axons exhibit molecular features of nociceptive nerve fibers. Another subpopulation of unmyelinated axons exhibits molecular characteristics of sympathetic nerve fibers. Unmyelinated sympathetic fibers and unmyelinated nociceptive fibers express proteins that are found during development and regeneration. Present findings support the hypothesis that ingrowth of nociceptive fibers are the source of chronic tendon pain.

中文翻译：

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肱二头肌腱长头中轴突的结构和分子特征

肱二头肌长头肌腱 (LHBT) 的神经支配没有得到充分记录。这是一个缺点，因为 LHBT 的病理是肩痛的主要来源。因此，该研究旨在表征 LHBT 的结构和分子神经元件。术中采集了 11 个 LHBT 的近端部分。有8个女性和3个男性标本。年龄从66岁到86岁不等。对于结构分析，在透射电子显微镜中观察神经元。对于分子表征，我们使用了一般神经元标记物，包括针对神经丝和蛋白质基因产物 9.5 (PGP9.5) 的抗体以及特定神经元标记物，包括针对髓鞘碱性蛋白 (MBP)、降钙素基因相关产物 (CGRP)、P 物质的抗体(SP)、酪氨酸羟化酶 (TH)、和生长相关蛋白 43 (GAP43)。抗神经丝和抗 PGP9.5 使整体神经支配可视化。在发育和再生过程中，抗 MBP 可视化髓鞘形成、抗 CGRP 和抗 SP 伤害性纤维、抗 TH 交感神经纤维和抗 GAP43 神经纤维。在共聚焦激光扫描显微镜中分析免疫标记的切片。我们表明 LHBT 包含无髓鞘和有髓神经纤维，它们在神经束中聚集并跟随血管。曼尼有髓鞘和无髓鞘轴突表现出伤害性神经纤维的分子特征。另一个无髓鞘轴突亚群表现出交感神经纤维的分子特征。无髓鞘交感神经纤维和无髓鞘伤害性纤维表达在发育和再生过程中发现的蛋白质。