Materials composed of the Drosophila melanogaster protein ultrabithorax are cytocompatible

The Drosophila melanogaster Hox protein ultrabithorax (Ubx) has the interesting ability to hierarchically self-assemble in vitro into materials that have mechanical properties comparable to natural elastin. Ubx materials can be easily functionalized by gene fusion, generating potentially useful scaffolds for cell and tissue engineering. Here, we tested the cytocompatibility of fibers composed of Ubx or an mCherry-Ubx fusion protein. Fibers were cultured with three primary human cell lines derived from vasculature at low passage: umbilical vein endothelial cells, brain vascular pericytes, or aortic smooth muscle cells. No direct or indirect toxicity was observed for any cell line, in response to fibers composed of either plain Ubx or mCherry-Ubx. Cells readily adhered to Ubx fibers, and cells attached to fibers could be transferred between tissue cultures without loss of viability for at least 96 h. When attached to fibers, the morphology of the three cell lines differed somewhat, but all cells in contact with Ubx fibers exhibited a microtubular network aligned with the long axis of Ubx fibers. Thus, Ubx fibers are cytocompatible with cultured primary human vascular cells.