Xu MengMeng, Jones Odell D, Wang Liyang, Zhou Xin, Davis Harry G, Bryant Joseph L, Ma Jianjie, Isaacs Willian B, Xu Xuehong
Department of Pharmacology, Duke University Medical Center, Durham, NC 27708 USA.
University of Pennsylvania ULAR, Philadelphia, PA 19144 USA.
Cell Biosci. 2017 Jan 3;7:3. doi: 10.1186/s13578-016-0130-6. eCollection 2017.
Massive liquid crystal droplets have been found during embryonic development in more than twenty different tissues and organs, including the liver, brain and kidney. Liquid crystal deposits have also been identified in multiple human pathologies, including vascular disease, liver dysfunction, age-related macular degeneration, and other chronic illnesses. Despite the involvement of liquid crystals in such a large number of human processes, this phenomenon is poorly understood and there are no in vitro systems to further examine the function of liquid crystals in biology.
We report the presence of tubular birefringent structures in embryoid bodies (EBs) differentiated in culture. These birefringent tubular structures initiate at the EB surface and penetrated the cortex at a variety of depths. Under crossed polarized light, these tubules are seen as a collection of birefringent Maltese crosses and tubules with birefringent walls and a non-birefringent lumen. The fluidity of these birefringent structures under pressure application led to elongation and widening, which was partially recoverable with pressure release. These birefringent structures also displayed heat triggered phase transition from liquid crystal to isotropic status that is partially recoverable with return to ambient temperature. These pressure and temperature triggered changes confirm the birefringent structures as liquid crystals. The first report of liquid crystal so early in development.
The structure of the liquid crystal tubule network we observed distributed throughout the differentiated embryoid bodies may function as a transportation network for nutrients and metabolic waste during EB growth, and act as a precursor to the vascular system. This observation not only reveals the involvement of liquid crystals earlier than previously known, but also provides a method for studying liquid crystals in vitro.
在胚胎发育过程中，已在二十多种不同的组织和器官中发现了大量液晶滴，包括肝脏、大脑和肾脏。在多种人类疾病中也发现了液晶沉积物，包括血管疾病、肝功能障碍、年龄相关性黄斑变性和其他慢性疾病。尽管液晶参与了如此众多的人类生理过程，但这种现象仍未得到充分理解，并且没有体外系统来进一步研究液晶在生物学中的功能。
我们报告了在体外分化的类胚体（EBs）中存在管状双折射结构。这些双折射管状结构起始于EB表面，并以不同深度穿透皮质。在正交偏光下，这些小管被视为一系列双折射马耳他十字以及具有双折射壁和非双折射管腔的小管。施加压力时，这些双折射结构的流动性导致其伸长和变宽，压力释放后部分可恢复。这些双折射结构还表现出热触发的从液晶到各向同性状态的相变，回到环境温度后部分可恢复。这些压力和温度触发的变化证实了双折射结构为液晶。这是在发育如此早期首次报道液晶。
我们观察到的分布在整个分化类胚体中的液晶小管网络结构，可能在EB生长过程中作为营养物质和代谢废物的运输网络，并充当血管系统的前体。这一观察结果不仅揭示了液晶比先前已知的更早参与其中，还提供了一种体外研究液晶的方法。
