The absence of serum also stimulates cell aggregation into islet-like clusters, which likely contributes to formation of cell conformation and cell-to-cell contacts required for BCD cell redifferentiation. We previously observed that proliferation of sorted BCD cells depended on factors secreted by non-BCD cells in the islet cell culture . It is possible that other cell types present in the islet cell culture also provide components needed for redifferentiation of BCD cells. Redifferentiation of purified BCD cells, in the absence of non- BCD cells, will help address this possibility. BCD cell redifferentiation involves MET, as judged by changes in gene expression, and by stimulation of redifferentiation upon inhibition of the EMT effector SLUG. The mechanistic correlation between MET and redifferentiation remains to be elucidated. It is possible that restoration of ECAD ASP1517 HIF inhibitor expression reinstates the normal cell-to-cell contacts needed for LEE011 chemical information Activation of beta-cell genes. Alternatively, transcription factors involved in EMT may act as repressors of beta-cell gene expression. Treatment with RC induced redifferentiation of up to 25% of all BCD cells at p5�C7. This represents a net 8�C32 fold increase in the number of insulin-producing cells, compared to uncultured islets. Improved redifferentiation conditions may extend the redifferentiation capacity to later passages, and increase the fraction of BCD cells undergoing redifferentiation, thus allowing generation of a larger mass of insulin-producing cells. Highthroughput screening of compound libraries may identify agents which can further stimulate redifferentiation of the expanded BCD cells. Improved redifferentiation protocols, followed by sorting of the insulin-producing cells generated, will allow functional analyses in vivo, in immunodeficient mice. In addition to improving the redifferentiation protocol, extension of the expansion capacity beyond the ,16 population doublings obtained in our current expansion conditions may be of potential value for generation of higher numbers of insulin-producing cells. Generation of SST + cells from lineage-traced cells suggests that redifferentiation involves BCD cell transition through an islet progenitor-like stage. Activation of expression of transcription factors characteristic of islet progenitor cells during redifferentiation, including SOX9, FOXA2, PDX1, NGN3, PAX4, and ARX, supports this possibility.