Rat hepatocyte spheroids formed on temperature-responsive PIPAAm polymer-grafted surface maintain long-term differentiated hepatocyte function

Background.Although the development of a practicable culture method to maintain long-term hepatocyte function is highly desirable, hepatocytes lose their liver-specific functions rapidly on regular collagen-coated dishes. In this study, we evaluated the efficacy of a special cell culture dish coated with the temperature-responsive polymer poly(N-isopropylacrylamide) (PIPAAm), and observed the morphological and functional changes of hepatocytes on changing the amount of polymer.Methods.Culture plates with varying amounts of PIPAAm polymer (1.5～3.5 times that in the commercially available temperatureresponsive polymer-containing dish (UpCellR, CellSeed, Tokyo, Japan)) were prepared. All dishes were enhanced by adding a layer of rat tail collagen I at a dose of 600 μg/dish for 3 hours. Hepatocytes isolated from Sprague-Dawley rats were cultured in these static culture systems. Morphologic changes and liver-specific functions were evaluated.Results.On day 7 of culture, spheroid formation of hepatocytes was observed in the high-polymer group, with the presence of glycogen and albumin in the spheroid. In the high-polymer group, the rate of albumin production was significantly higher than in the low-polymer group until day 14 of culture (P<0.001).Conclusion.The spheroid formation of hepatocytes cultured in the presence of a high level of PIPAAm showed the long-term maintenance of liver-specific functions in vitro

One-cocycles on smooth flows of weights and extended modular coactions

This paper is concerned with Borel 1-cocycles on ergodic flows on standard Borel measure spaces and a certain type of group coactions on (separable) factors

A characterization of coactions whose fixed-point algebras contain special maximal abelian *-subalgebras

It is shown that, for the von Neumann algebra A obtained from a principal measured groupoidRwith the diagonal subalgebraD of A, there exists a natural ‘bijective’ correspondence between coactions on A that fix D pointwise and Borel 1-cocycles on R. As an application of this result, we classify a certain type of coactions on approximately finite-dimensional type II factors up to cocycle conjugacy. By using our characterization of coactions mentioned above, we are also able to generalize to some extent those results of Zimmer concerning 1-cocycles on ergodic equivalence relations into compact groups