Differential biomechanical properties of mouse distal colon and rectum innervated by the splanchnic and pelvic afferents
Differential biomechanical properties of mouse distal colon and rectum innervated by the splanchnic and pelvic afferents
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DOI：
10.1152/ajpgi.00324.2018
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发表时间：
2019-04-01
影响因子：
4.5
通讯作者：
Feng, Bin
中科院分区：
文献类型：
--
作者：
Siri, Saeed;Maier, Franz;Feng, Bin
内脏疼痛是肠易激综合征患者的主要主诉之一，这种疼痛是由远端结肠和直肠（结肠直肠）的机械扩张和拉伸引起的。本研究的重点是结肠直肠的生物力学，可以发挥关键作用的机械神经编码。我们收获了小鼠结肠直肠的远端30 mm，平均分为三个10 mm长的节段（结肠，中间和直肠），并对每个组织节段进行双轴机械拉伸试验和开角测量。此外，我们确定了胶原纤维的取向和内容物的厚度结直肠壁的非线性成像通过二次谐波产生（SHG）。我们的研究结果揭示了从结肠到直肠段的组织顺应性和预应力的逐步增加，这支持了先前的电生理发现，即分别支配结肠和直肠神经支配的腰内脏神经（LSN）和盆腔神经（PN）的传入神经对不同的机械神经编码。结直肠在圆周方向上的粘弹性明显大于轴向。此外，我们的SHG结果显示粘膜下层中有丰富的胶原蛋白网络，并且与轴向方向成约+/- 30度，与双轴测试结果一致，轴向方向的刚度几乎是周向方向的两倍。从目前的生物力学研究结果强烈表明，局部组织生物力学的突出作用，在确定不同地区的结肠直肠的差异机械神经编码功能。新&值得注意的是，机械扩张和拉伸，而不是热，切割，或捏，可靠地引起疼痛从远端结肠和直肠。我们报告了不同的局部力学沿着的纵向长度的结直肠，这是与现有的文献上不同的mechanotransduction传入神经支配的近端和远端区域的结直肠。这项研究提请注意局部力学作为一个潜在的决定因素，机械神经编码的结直肠，这是至关重要的内脏伤害性。
Visceral pain is one of the principal complaints of patients with irritable bowel syndrome, and this pain is reliably evoked by mechanical distension and stretch of distal colon and rectum (colorectum). This study focuses on the biomechanics of the colorectum that could play critical roles in mechanical neural encoding. We harvested the distal 30 mm of the colorectum from mice, divided evenly into three 10-mm-long segments (colonic, intermediate and rectal), and conducted biaxial mechanical stretch tests and opening-angle measurements for each tissue segment. In addition, we determined the collagen fiber orientations and contents across the thickness of the colorectal wall by nonlinear imaging via second harmonic generation (SHG). Our results reveal a progressive increase in tissue compliance and prestress from colonic to rectal segments, which supports prior electrophysiological findings of distinct mechanical neural encodings by afferents in the lumbar splanchnic nerves (LSN) and pelvic nerves (PN) that dominate colonic and rectal innervations, respectively. The colorectum is significantly more viscoelastic in the circumferential direction than in the axial direction. In addition, our SHG results reveal a rich collagen network in the submucosa and orients approximately +/- 30 degrees to the axial direction, consistent with the biaxial test results presenting almost twice the stiffness in axial direction versus the circumferential direction. Results from current biomechanical study strongly indicate the prominent roles of local tissue biomechanics in determining the differential mechanical neural encoding functions in different regions of the colorectum.NEW & NOTEWORTHY Mechanical distension and stretch-not heat, cutting, or pinching-reliably evoke pain from distal colon and rectum. We report different local mechanics along the longitudinal length of the colorectum, which is consistent with the existing literature on distinct mechanotransduction of afferents innervating proximal and distal regions of the colorectum. This study draws attention to local mechanics as a potential determinant factor for mechanical neural encoding of the colorectum, which is crucial in visceral nociception.