title: Rapid Self-Assembly of Tubular Arterial Media Layer from Smooth Muscle Cells in Transient Fibrin Gel.
abstract: BACKGROUND: Tissue engineered blood vessels could address the large clinical need for small caliber vascular grafts. Self-assembly approaches that employ transient scaffolds to form tissues from only cells and secreted matrix could form completely autologous vascular grafts that rapidly remodel and integrate with host tissue in vivo. The objective of this study was to develop a simple and rapid method to self-assemble vascular cells into vascular grafts.  HYPOTHESIS: We hypothesized that entrapment in rapidly degrading fibrin gels could facilitate self-assembly of vascular smooth muscle cells into a tubular tissue comprised mainly of SMCs and secreted matrix.  METHODS: Baboon SMCs were entrapped in fibrin around a silicone tube and cultured for 14 days without fibrinolysis inhibitor. Spontaneous delamination from the inner tube allowed for simple isolation of constructs with forceps.  RESULTS: Engineered tissues are tubular, handleable, and highly cellular, with substantial collagen deposition. Fibrin is largely degraded within 14 days. Tensile elastic modulus of ring segments is 36.2 kPa and 1.60 MPa for the toe and heel regions of the stress-strain relation, respectively.  CONCLUSION: Fibrin entrapment without fibrinolysis inhibitor can facilitate rapid self-assembly of SMCs into tubular tissues. Future work will focus on mechanical conditioning and co-culture with vascular endothelial cells to improve mechanical strength and impart antithrombogenicity.
authors.affiliation: Department of Bioengineering and Surgery, McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213.
authors.forename: Robert
authors.initials: R
authors.lastname: Allen
authors.forename: Yadong
authors.initials: Y
authors.lastname: Wang