RT Journal Article SR Electronic T1 Silk assembly integrates cells into a 3D fibrillar network that promotes cell spreading and proliferation JF bioRxiv FD Cold Spring Harbor Laboratory SP 403345 DO 10.1101/403345 A1 Ulrika Johansson A1 Mona Widhe A1 Nancy Dekki Shalaly A1 Irene Linares Arregui A1 Linnea Nilebäck A1 Christos Panagiotis Tasiopoulos A1 Carolina Åstrand A1 Per-Olof Berggren A1 Christian Gasser A1 My Hedhammar YR 2018 UL http://biorxiv.org/content/early/2018/08/29/403345.abstract AB Tissues are built of cells integrated in an extracellular matrix (ECM) which provides a three-dimensional (3D) fibrillar network with specific sites for cell anchorage. By genetic engineering, motifs from the ECM can be functionally fused to recombinant silk proteins. Such a silk protein, FN-silk, which harbours a motif from fibronectin, has the ability to self-assemble into fibrillar networks under physiological-like conditions. Herein we describe a method by which mammalian cells are added to the silk solution before assembly, and thereby get uniformly integrated between the formed fibrils. In the resulting 3D scaffold, the cells proliferate and spread out with tissue-like morphology. Elongated cells containing filamentous actin and defined focal adhesion points confirm proper cell attachment to the FN-silk. The cells remain viable in culture for at least 90 days. The method is also scalable to macro-sized 3D cultures. Silk fibers with integrated cells are both strong and extendable, with mechanical properties similar to that of artery walls. The described method enables both differentiation of stem- or precursor cells in 3D and facile co-culture of several different cell types. We show that inclusion of endothelial cells leads to the formation of vessel-like structures throughout the tissue constructs. Hence, silk-assembly in presence of cells constitutes a viable option for 3D culture of cells integrated in a fibrillary ECM-like network, with potential as base for engineering of functional tissue.