The Importance of Cell–Cell Interaction Dynamics in Bottom-Up Tissue Engineering: Concepts of Colloidal Self-Assembly in the Fabrication of Multicellular Architectures

Abstract

Building tissue from cells as the basic building block based on principles of self-assembly is a challenging and promising approach. Understanding how far principles of self-assembly and self-sorting known for colloidal particles apply to cells remains unanswered. In this study, we demonstrate that not just controlling the cell–cell interactions but also their dynamics is a crucial factor that determines the formed multicellular structure, using photoswitchable interactions between cells that are activated with blue light and reverse in the dark. Tuning dynamics of the cell–cell interactions by pulsed light activation results in multicellular architectures with different sizes and shapes. When the interactions between cells are dynamic, compact and round multicellular clusters under thermodynamic control form, while otherwise branched and loose aggregates under kinetic control assemble. These structures parallel what is known for colloidal assemblies under reaction- and diffusion-limited cluster aggregation, respectively. Similarly, dynamic interactions between cells are essential for cells to self-sort into distinct groups. Using four different cell types, which expressed two orthogonal cell–cell interaction pairs, the cells sorted into two separate assemblies. Bringing concepts of colloidal self-assembly to bottom-up tissue engineering provides a new theoretical framework and will help in the design of more predictable tissue-like structures.

Orthogonal Blue and Red Light Controlled Cell–Cell Adhesions Enable Sorting-out in Multicellular Structures

“…In addition, general advantages of photoregulation are the high spatiotemporal control, tunable dynamics, and high orthogonality without interference from other cellular processes, as previously demonstrated in numerous optogenetic studies. 33 − 39 …”

“…Moreover, the cell clustering under light was faster for all photoswitchable proteins and already significant after 30 min, while the E-cadherin based clustering of MCF7 cells was slower and took over 1 h. These differences in assembly dynamics and final aggregate size could be explained by factors including the differences in intrinsic properties of the photoswitchable proteins, such as the thermodynamic and mechanical stability of the dimerization and the protein–protein interaction dynamics. 33 …”

“…It should be noted that we have observed similar differences in the reversion kinetics at the molecular and the cell–cell adhesion level using other heterophilic light responsive protein–protein interactions. 33 , 34 …”

Wie Licht beim Aufbau von Geweben helfen kann

“…Die andere Variante sind Proteinpaare, die bei Beleuchtung aneinanderbinden, also heterodimerisieren. Zwei unterschiedliche Zelltypen, die je einen der Bindungspartner auf der Oberfl äche präsentieren, können durch Lichteinwirkung miteinander verbunden werden [7,9]. Mit diesen unterschiedlichen selbst-und fremdspezifi schen Zell-Zell-Interaktionen können wir gezielt Zellen vom gleichen oder unterschiedlichen Typus in einer multizellulären Struktur zusammenbauen.…”

“…Ein weiterer Aspekt, der bei der Herstellung von Gewebestrukturen eine wichtige Rolle spielt, ist die Dynamik der Zell-Zell-Adhäsionen (Abb. 2B, [9]). Wenn Zellen sehr stark miteinander interagieren und daher nach den ersten Kontakten nicht die Möglichkeit haben, sich neu anzuordnen, bilden sich verzweigte, multizelluläre Strukturen.…”