Engineered Tissue On A String

Long, thin fibrous materials would be attractive for tissue engineering if there were a good way to incorporate cells and extracellular matrix proteins into the fibers. Shoji Takeuchi and coworkers at the University of Tokyo have now made that wish come true (Nat. Mater., DOI: 10.1038/nmat3606). The researchers took advantage of double-coaxial laminar flow in a microfluidic device to fabricate fibers with a tough calcium alginate shell around cells and extracellular matrix proteins such as collagen or fibrinogen. The calcium alginate quickly forms a stable hydrogel that holds the proteins in place so they can also gel. After the researchers culture cells in the core, they remove the outer shell by enzymatic digestion. They made meter-long fibers with a variety of cell types, including structural, muscle, epithelial, and nerve cells. The cell-containing fibers function just like their constituent cells. The researchers made three-dimensional structures by braiding and weaving the yarnlike fibers. In a test of the materials, they implanted 20-cm-long, insulin-secreting pancreatic cell fibers into diabetic mice. The fibers normalized blood glucose levels in the mice for almost two weeks.