In this research project, we have found the following things.

(1) Purification and expansion of hepatic progenitor cells derived from human pluripotent stem cells. We differentiated human ES and iPS cells into hepatocytic cells by the serial cytokine stimulation and stained with several cell surface antibodies. We found that the CD13+CD133+ cell fraction contained the progenitor cells having the high-proliferative ability and bi-potency to differentiate into hepatocytic and cholangiocytic cells. Long-term proliferation of these cells required the addition of epidermal growth factor and the inhibition of Rock and ALK signals (PLoS One, 2013).

(2) Differentiation of human iPS-derived hepatic progenitor cells into cholangiocytic cyst structure. We found that part of iPS-derived hepatic progenitor cells spontaneously differentiated into cholangiocytic progenitor-like cells in long-term culture. We purified these cholangiocytic progenitor-like cells using specific cell-surface marker antibodies and cultured in extracellular matrix gel in the presence of several cytokines. These cells differentiated into epithelial cysts expressing keratin 7, a cholangiocytic marker gene.

As shown above, we established the new culture system for the induction of human cholangiocytic cyst structures derived from human iPS cells.