Singh Sagar, Winkelstein Beth A
Department of Bioengineering, University of Pennsylvania, 210 S. 33rd St, Philadelphia, PA, 19104, USA.
Department of Neurosurgery, University of Pennsylvania, 3400 Spruce St, Philadelphia, PA, 19104, USA.
Biomech Model Mechanobiol. 2022 Jun;21(3):885-898. doi: 10.1007/s10237-022-01565-6. Epub 2022 Mar 12.
Stretch injury of the facet capsular ligament is a cause of neck pain, inducing axonal injury, neuronal hyperexcitability, and upregulation of pain neuromodulators. Although thresholds for pain and collagen reorganization have been defined and integrins can modulate pain signaling with joint trauma, little is known about the role of integrin signaling in neuronal dysfunction from tensile loading of the innervated capsular ligament. Using a well-characterized biomimetic collagen gel model of the capsular ligament's microstructure and innervation, this study evaluated extrasynpatic expression of N-Methyl-D-Aspartate receptor subtype 2B (NR2B) as a measure of neuronal dysfunction following tensile loading and determined mechanical thresholds for its upregulation in primary sensory neurons, with and without integrin inhibition. Collagen gels with dissociated dorsal root ganglion neurons (n = 16) were fabricated; a subset of gels (n = 8) was treated with the β1 integrin subunit inhibitor, TC-I15. Gels were stretched to failure in tension and then immunolabeled for axonal NR2B. Inhibiting the integrin subunit does not change the failure force (p = 0.12) or displacement (p = 0.44) but does reduce expression of the β1 subunit by 41% (p < 0.001) and decrease axonal NR2B expression after stretch (p = 0.018). Logistic regressions estimating the maximum principal strain threshold for neuronal dysfunction as evaluated by Analysis of Covariance determine that integrin inhibition increases (p = 0.029) the 50th percentile strain threshold (7.1%) above the threshold for upregulation in untreated gels (6.2%). These results suggest that integrin contributes to stretch-induced neuronal dysfunction via neuron-integrin-collagen interactions.
小关节囊韧带的拉伸损伤是颈部疼痛的一个原因，可导致轴突损伤、神经元兴奋性过高以及疼痛神经调节因子上调。虽然已经明确了疼痛阈值和胶原重组，并且整合素可调节关节创伤时的疼痛信号，但对于整合素信号在受支配囊韧带拉伸负荷导致的神经元功能障碍中的作用知之甚少。本研究使用具有特征明确的囊韧带微观结构和神经支配的仿生胶原凝胶模型，评估N-甲基-D-天冬氨酸受体2B亚型（NR2B）的突触外表达，以此作为拉伸负荷后神经元功能障碍的指标，并确定在有无整合素抑制的情况下，初级感觉神经元中NR2B上调的力学阈值。制备了含有解离背根神经节神经元（n = 16）的胶原凝胶；一部分凝胶（n = 8）用β1整合素亚基抑制剂TC-I15处理。将凝胶拉伸至破坏，然后对轴突NR2B进行免疫标记。抑制整合素亚基不会改变破坏力（p = 0.12）或位移（p = 0.44），但会使β1亚基的表达降低41%（p < 0.001），并减少拉伸后轴突NR2B的表达（p = 0.018）。通过协方差分析评估神经元功能障碍的最大主应变阈值的逻辑回归确定，整合素抑制会使第50百分位应变阈值（7.1%）升高（p = 0.029），高于未处理凝胶中上调阈值（6.2%）。这些结果表明，整合素通过神经元-整合素-胶原相互作用促成拉伸诱导的神经元功能障碍。
