Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia.
Lasers Med Sci. 2011 May;26(3):401-13. doi: 10.1007/s10103-010-0871-0. Epub 2010 Dec 29.
The effects of non-ablative infrared (IR) laser treatment of collagenous tissue have been commonly interpreted in terms of collagen denaturation spread over the laser-heated tissue area. In this work, the existing model is refined to account for the recently reported laser-treated tissue heterogeneity and complex collagen degradation pattern using comprehensive optical imaging and calorimetry toolkits. Patella ligament (PL) provided a simple model of type I collagen tissue containing its full structural content from triple-helix molecules to gross architecture. PL ex vivo was subjected to IR laser treatments (laser spot, 1.6 mm) of equal dose, where the tissue temperature reached the collagen denaturation temperature of 60 ± 2°C at the laser spot epicenterin the first regime, and was limited to 67 ± 2°C in the second regime. The collagen network was analyzed versus distance from the epicenter. Experimental characterization of the collagenous tissue at all structural levels included cross-polarization optical coherence tomography, nonlinear optical microscopy, light microscopy/histology, and differential scanning calorimetry. Regressive rearrangement of the PL collagen network was found to spread well outside the laser spot epicenter (>2 mm) and was accompanied by multilevel hierarchical reorganization of collagen. Four zones of distinct optical and morphological properties were identified, all elliptical in shape, and elongated in the direction perpendicular to the PL long axis. Although the collagen transformation into a random-coil molecular structure was occasionally observed, it was mechanical integrity of the supramolecular structures that was primarily compromised. We found that the structural rearrangement of the collagen network related primarily to the heat-induced thermo-mechanical effects rather than molecular unfolding. The current body of evidence supports the notion that the supramolecular collagen structure suffered degradation of various degrees, which gave rise to the observed zonal character of the laser-treated lesion.
非消融性红外（IR）激光处理胶原组织的影响通常根据激光加热组织区域内的胶原变性来解释。在这项工作中，我们使用综合光学成像和量热工具包，对现有的模型进行了改进，以解释最近报道的激光处理组织异质性和复杂的胶原降解模式。髌韧带（PL）提供了一个简单的 I 型胶原组织模型，其中包含从三螺旋分子到整体结构的完整结构内容。PL 离体标本接受了相同剂量的 IR 激光处理（激光点，1.6mm），其中组织温度在第一阶段达到了胶原变性温度 60±2°C，在第二阶段限制在 67±2°C。胶原网络根据距中心点的距离进行分析。对所有结构水平的胶原组织进行了实验表征，包括交叉偏振光相干断层扫描、非线性光学显微镜、光学显微镜/组织学和差示扫描量热法。发现 PL 胶原网络的退行性重排很好地扩展到了激光点中心点之外（>2mm），并伴随着胶原的多层次层次重组。发现四个具有不同光学和形态特性的区域，它们的形状均为椭圆形，并且在垂直于 PL 长轴的方向上拉长。尽管偶尔观察到胶原转化为无规卷曲的分子结构，但主要是超分子结构的机械完整性受到了损害。我们发现，胶原网络的结构重排主要与热诱导的热机械效应有关，而不是分子展开。目前的证据支持这样一种观点，即超分子胶原结构受到不同程度的降解，这导致了观察到的激光处理损伤的带状特征。
