FGF2 and isolated hemihyperplasia: Thrombin, basic fibroblast growth factor (bFGF), and platelet‐derived growth factor (PDGF)‐BB, which are related to vascular injury and known to contribute to IH, were selected as the biomolecules for investigation.[1, 27, 28] For this purpose, we used the 5‐channel MPS developed in our previous study (Figure1).[17] In preparation of 3D VSMC culture, a basic collagen solution was introduced into the subendothelial channels, and a mixture of VSMCs and neutral collagen solution was seeded into the medial channels in the microphysiological device.