Construction of luminal structures with different diameters in the cell sheets. (a) Top view of the stacked cell sheets before and after removing the titanium wires with diameters of 50, 100, 150, and 200 μm (scale bars, 5 mm). (b) Cross-sectional images captured using OCT. The white arrows indicate the lumen structures (scale bars, 500 μm). (c) Histological images of the stacked cell sheets with lumen structures (scale bars, 100 μm). (d) Graph showing the results obtained by the image analysis and measurement of the luminal structure size (). The error bars refer to ± SD.