SummaryDuring liver development, hepatoblasts and liver non-parenchymal cells (NPCs) such as liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs) constitute the liver bud where they proliferate and differentiate. Accordingly, we reasoned that liver NPCs would support the maturation of hepatocytes derived from human induced pluripotent stem cells (hiPSCs), which usually exhibit limited functions. We found that the transforming growth factor β and Rho signaling pathways, respectively, regulated the proliferation and maturation of LSEC and HSC progenitors isolated from mouse fetal livers. Based on these results, we have established culture systems to generate LSECs and HSCs from hiPSCs. These hiPSC-derived NPCs exhibited distinctive phenotypes and promoted self-renewal of hiPSC-derived liver progenitor cells (LPCs) over the long term in the two-dimensional culture system without exogenous cytokines and hepatic maturation of hiPSC-derived LPCs. Thus, a functional human liver model can be constructed in vitro from the LPCs, LSECs, and HSCs derived from hiPSCs.

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We analyzed the shape and width of room-temperature persistent holes in photoreactive and multiplescattering media in frequency and wave-vector domains. The shape and width of holes depend on sample thickness, transport mean free path, geometrical configuration, and absorption lengths. The measurements of the angular dependence of hole burning in a disordered CdS 0.85 Se 0.15-doped glass sample were in quantitative agreement with theory.

We examined laser action in a two-dimensional amplifying and scattering medium consisting of random array of dye-doped plastic fiber. When the excitation pulse energy was increased, the parallel emission component to the fiber first reached the laser threshold showing spectral collapse, and then further increase in the excitation pulse energy resulted in the subsequent laser action in the perpendicular component. Two-beam spatial-correlation measurement was performed to examine the gain regions. It was found that the size of the gain region is different between the two polarization components. Experimental results on the threshold and the gain region are discussed on the basis of simple rate equations.