Feeder-free culture for mouse induced pluripotent stem cells by using UV/ozone surface-modified substrates.

Pluripotent stem cells (PSCs), especially induced PSCs (iPSCs), have great potential for regenerative medicine. Conventionally, PSCs are cultured and expanded efficiently on feeder cell layers or on cell-adhesive matrices. Large-scale iPSC expansion in an undifferentiated state without laborious culturing procedures and high manufacturing costs for the adhesive matrix is urgently required to integrate iPSCs into therapeutic applications. For this, feeder layers or cell-adhesive matrix coating have to be removed from the iPSC culture system. To enable feeder- and matrix coating-free culture conditions, we focused on a UV/ozone surface treatment technique for polystyrene cell culture substrates to improve PSC adhesion and proliferation. In this study, changes in the molecular structure of UV/ozone-modified polystyrene were characterized to optimize the surface chemistry for iPSC. Mouse iPSCs (miPSCs) were cultured on the UV/ozone-modified polystyrene substrates without feeder layers. As a result, large polymeric chains of polystyrene were dissociated into small polymeric chains and oxidized to form ester and carboxylic acid functional groups by the UV/ozone treatment. Moreover, it was suggested that optimal valance of these modified molecules enabled the feeder- and matrix coating-free culture of miPSC with maintaining pluripotency.