Hacettepe University, Institute of Neurological Sciences and Psychiatry, Ankara, Turkey.
Hacettepe University, Institute of Neurological Sciences and Psychiatry, Ankara, Turkey.
Exp Neurol. 2020 Oct;332:113392. doi: 10.1016/j.expneurol.2020.113392. Epub 2020 Jun 29.
Although it has been documented that central nervous system pericytes are able to contract in response to physiological, pharmacological or pathological stimuli, the underlying mechanism of pericyte contractility is incompletely understood especially in downstream pericytes that express low amounts of alpha-smooth muscle actin (α-SMA). To study whether pericyte contraction involves F-actin polymerization as in vascular smooth muscle cells, we increased retinal microvascular pericyte tonus by intravitreal injection of a vasoconstrictive agent, noradrenaline (NA). The contralateral eye of each mouse was used for vehicle injection. The retinas were rapidly extracted and fixed within 2 min after injections. Polymeric/filamentous (F-actin) and monomeric/globular (G-actin) forms of actin were labeled by fluorescently-conjugated phalloidin and deoxyribonuclease-I, respectively. We studied 108 and 83 pericytes from 6 NA- and 6 vehicle-treated retinas and, found that F/G-actin ratio, a microscopy-based index of F-actin polymerization, significantly increased in NA-treated retinas [median (IQR): 4.2 (3.1) vs. 3.5 (2.1), p = .006], suggesting a role for F-actin polymerization in pericyte contractility. Shift from G-actin monomers to polymerized F-actin was more pronounced in 5th and 6th order contracted pericytes compared to non-contracted ones [7.6 (4.7) vs. 3.2 (1.2), p < .001], possibly due to their dependence on de novo F-actin polymerization for contractile force generation because they express α-SMA in low quantities. Capillaries showing F-actin polymerization had significantly reduced diameters compared to the ones that did not exhibit increased F/G-actin ratio in pericytes [near soma / branch origin diameter; 0.67 (0.14) vs. 0.81 (0.34), p = .005]. NA-responsive capillaries generally did not show nodal constrictions but a tide-like diameter decrease, reaching a maximum near pericyte soma. These findings suggest that pericytes on high order downstream capillaries have F-actin-mediated contractile capability, which may contribute to the vascular resistance and blood flow regulation in capillary bed.
虽然已经有文献证明中枢神经系统周细胞能够对生理、药理学或病理学刺激做出收缩反应，但周细胞收缩性的潜在机制尚不完全清楚，尤其是在表达低量α-平滑肌肌动蛋白 (α-SMA) 的下游周细胞中。为了研究周细胞收缩是否涉及到血管平滑肌细胞中的 F-肌动蛋白聚合，我们通过向玻璃体内注射血管收缩剂去甲肾上腺素 (NA) 来增加视网膜微血管周细胞的紧张度。每只小鼠的对侧眼睛用于注射载体。在注射后 2 分钟内快速提取并固定视网膜。通过荧光标记的鬼笔环肽和脱氧核糖核酸酶-I 分别标记聚合/丝状 (F-肌动蛋白) 和单体/球状 (G-肌动蛋白) 形式的肌动蛋白。我们研究了来自 6 只 NA 处理和 6 只载体处理的视网膜的 108 个和 83 个周细胞，发现 NA 处理的视网膜中 F/G-肌动蛋白比值（一种基于显微镜的 F-肌动蛋白聚合指数）显著增加[中位数 (IQR)：4.2 (3.1) 比 3.5 (2.1)，p = 0.006]，提示 F-肌动蛋白聚合在周细胞收缩性中起作用。与非收缩性周细胞相比，在第 5 级和第 6 级收缩性周细胞中，从 G-肌动蛋白单体向聚合的 F-肌动蛋白的转变更为明显[7.6 (4.7) 比 3.2 (1.2)，p < 0.001]，这可能是因为它们依赖于新的 F-肌动蛋白聚合来产生收缩力，因为它们低量表达α-SMA。与在周细胞中未表现出增加的 F/G-肌动蛋白比值的毛细血管相比，显示 F-肌动蛋白聚合的毛细血管的直径明显减小[靠近体/分支起源直径；0.67 (0.14) 比 0.81 (0.34)，p = 0.005]。NA 反应性毛细血管通常没有表现出节段性收缩，但出现类似潮汐的直径减小，在周细胞体附近达到最大值。这些发现表明，在下游高阶毛细血管上的周细胞具有 F-肌动蛋白介导的收缩能力，这可能有助于毛细血管床的血管阻力和血流调节。
