在生物中，細胞的集體運動是極為重要的過程，如胚胎演化、傷口 癒合、癌症轉移等。細胞可透過細胞間隙 (cell junction) 與近鄰細胞產生交互作用與主動爬行形成強耦合自主多體系統 (coupled many-body active system)並可展現集體合作運動。 我們研究癌細胞入侵至二維緻密單層血管內皮細胞後在時空上癌細胞群聚現象與其之動力行為。單層的血管內皮細胞運動隨著時間與細胞數增生而從液態相持續減緩至冷液體相 (cold-liquid state)，意旨內皮細胞將持續運動永不停歇，這是因為細胞為主動軟物質，有無限多個自由度可主動伸展及收縮其細胞形態。並透過細胞間隙 (cell junction)交換彼此動量，因此單層血管內皮細胞可持續運動並展現類漩渦運動 (vortex-like motion)。 我們混合了 10 % 癌細胞於緻密單層血管內皮細胞，觀察癌細胞 團簇後在時空上的演變，利用活體染色發現癌細胞利用破壞血管內皮 細胞間隙侵略至單層緻密的血管內皮細胞層，由於癌細胞造成的血管 內皮細胞破口處大小不依因此引發的集體運動行為呈現多尺度的群聚 現象，亦發現癌細胞的集體運動為多尺度的類漩渦運動 (turbulent-like motion)，其頻譜呈現冪次下降 (power law decay)。;Through the interplay of mutual coupling and self-propelling, coupled many-body active systems can exhibit collective motions, especially in biological systems such as fish schools, flocking birds, dense bacteria, confluent cells. In the systems of 2D confluent cells on the substrate, cells are strongly coupled with their neighbors through cell junctions. The highly deformable cell boundary contains a large number of degrees of freedom. Therefore, the confluent epithelial and endothelial cell monolayers have been used as model systems to investigate the intriguing cell collective motion. Nevertheless, unlike the studies on collective motion of the single type cell monolayers mainly exhibit liquid or solid-like collective motions, the dynamics of mixtures of two different types of cells remain elusive. In this work, we experimentally study the dynamical evolutions of a confluent endothelial cell (EC) monolayer and a cancer cell (CC)/ EC mixture after the invasion of more motile CCs into a confluent EC monolayer. We demonstrate that slowed down the vortex like coherent motion of EC only monolayer, and the rejuvenation of aged motion after the invasion of a small fraction of CCs. It is found that, the slowed down collective motion in EC only monolayer is due to the gradual structure relaxation and increasing EC density through proliferation. CC invasion is associated with opening EC cell-cell junctions. With increasing time, CCs tend to gradually aggregate and form larger clusters. Interaction with ECs through the confining fluctuating irregular EC boundary without EC-CC junction, more CCs in the larger clusters exhibit stronger turbulent motion with power law scaling extending to the lower frequency modes. It also leads to longer trajectory persistent length. The speeded up CC dynamics in turn enhances the turbulent like motion of surrounding ECs and awakes their slowed down dynamics.
