Magneticall y-oriented tissue-equivalent tubes: Application to a circumferentiall.y-oriented media-equivalent

Circumferential orientation of collagen fibrils in a media-equivalent (ME) is achieved in a simple and effective way using the orienting effect of a strong magnetic field during collagen fibrillogenesis when the ME is first created. Circumferential orientation of the entrapped smooth muscle cells (SMC) is achieved subsequently via cell contact guidance, the induced SMC orientation along oriented fibrils. After describing our methods (U.S. patent pending), we provide several lines of evidence that our magnetically-oriented ME is circumferentially oriented, including collagen birefringence and circumferential SMC orientation, accelerated ME contraction and increased ME stiffness with reduced creep in the circumferential direction, as compared to control MEs that were not exposed to a magnetic field during fibrillogenesis. We compare the mechanical properties and collagen fibril orientation of ME that contract freely following preparation versus ME that are left on the lumen-forming rod during contraction. The relative contributions of SMC and collagen to the mechanical properties of the ME are assessed by comparing ME treated with cytochalasin B and untreated ME. We discuss the optimization of our methods in order to better mimic the circumferential orientation and mechanical properties of a natural media.