Eftimov Petar, Yokoi Norihiko, Tonchev Vesselin, Nencheva Yana, Georgiev Georgi As
Department of Cytology, Histology and Embryology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia, Bulgaria.
Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Eur Biophys J. 2017 Mar;46(2):129-140. doi: 10.1007/s00249-016-1146-x. Epub 2016 Jun 21.
The surface properties of meibomian secretion (MGS), the major constituent of the tear film (TF) lipid layer, are of key importance for TF stability. The interfacial properties of canine, cMGS, and feline, fMGS, meibum films were studied using a Langmuir surface balance. These species were selected because they have blinking frequency and TF stability similar to those of humans. The sample's performance during dynamic area changes was evaluated by surface pressure (π)-area (A) isocycles and the layer structure was monitored with Brewster angle microscopy. The films' dilatational rheology was probed via the stress-relaxation technique. The animal MGS showed similar behavior both between each other and with human MGS (studied previously). They form reversible, non-collapsible, multilayer thick films. The relaxations of canine, feline, and human MGS films were well described by double exponential decay reflecting the presence of two processes: (1) fast elastic process, with characteristic time τ < 10 s and (2) slow viscous process, with τ > 100 s-emphasizing the meibum layers viscoelasticity. The temperature decrease from 35 to 25 °C resulted in decreased thickness and lateral expansion of all MGS layers accompanied with increase of the π/A hysteresis and of the elastic process contribution to π relaxation transients. Thus, MGS films of mammals with similar blinking frequency and TF stability have similar surface properties and stress relaxations unaltered by the interspecies MGS compositional variations. Such knowledge may impact the selection of animal mimics of human MGS and on a better understanding of lipid classes' impact on meibum functionality.
睑板腺分泌物（MGS）是泪膜（TF）脂质层的主要成分，其表面性质对TF的稳定性至关重要。使用Langmuir表面天平研究了犬类睑板腺分泌物（cMGS）和猫类睑板腺分泌物（fMGS）睑脂膜的界面性质。选择这些物种是因为它们的眨眼频率和TF稳定性与人类相似。通过表面压力（π）-面积（A）等压线评估样品在动态面积变化过程中的性能，并用布鲁斯特角显微镜监测层结构。通过应力松弛技术探测薄膜的膨胀流变学。动物MGS彼此之间以及与之前研究的人类MGS表现出相似的行为。它们形成可逆、不可塌陷的多层厚膜。犬类、猫类和人类MGS膜的松弛过程可以用双指数衰减很好地描述，这反映了两个过程的存在：（1）快速弹性过程，特征时间τ<10秒；（2）缓慢粘性过程，τ>100秒，强调睑脂层的粘弹性。温度从35℃降至25℃导致所有MGS层的厚度和横向膨胀减小，同时π/A滞后增加，弹性过程对π松弛瞬态的贡献增加。因此，具有相似眨眼频率和TF稳定性的哺乳动物的MGS膜具有相似的表面性质和应力松弛，不受种间MGS成分变化的影响。这些知识可能会影响对人类MGS动物模拟物的选择，并有助于更好地理解脂质类别对睑脂功能的影响。
