Inhibition of BET selectively eliminates undifferentiated pluripotent stem cells

Efficient Differentiation of Mouse Induced Pluripotent Stem Cells into Alveolar Epithelium Type II with a BRD4 Inhibitor

Regenerative medicine has continued to progress for lung biology and lung diseases. Efforts have focused on a variety of different applications for pluripotent stem cells. Several groups have reported successful methods for inducing differentiation of induced pluripotent stem cells (iPSCs) into the airway epithelium such as alveolar epithelium type II (ATII). However, differentiation efficiency varies among reports and improvements are needed. In the present paper, we propose a novel method for elimination of residual undifferentiated murine iPSCs using JQ1, a potent inhibitor of bromodomain (BRD) and extraterminal domain (BET) family proteins, for efficient differentiation into ATII. First, the murine iPSC line 20D-17 was induced to differentiate into ATII over a period of 26 days (days 0-26) using previously reported embryoid body seeding and stepwise differentiation methods. mRNA expressions of differentiation markers including surfactant protein C (Sftpc) were confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) results, and 17% of the cells were shown positive for prosurfactant protein C (proSPC) in flow cytometry analysis. Next, those cells were cultured three-dimensionally in Matrigel for an additional 14 days (days 26-40), during which JQ1 was added for 4 days (days 28-32) to remove residual undifferentiated iPSCs. As a result, on day 40, the mRNA expression level of Sftpc in the three-dimensional culture was maintained at the same level as on day 26 and shown to be further increased by the addition of JQ1, with 39% of the cells found to express proSPC, showing that differentiation efficiency could be further increased. Three-dimensional culture with BRD4 inhibition by JQ1 improved the differentiation induction efficiency to ATII by removing residual undifferentiated murine iPSCs during the differentiation induction process.

Metastable Reprogramming State of Single Transcription Factor-Derived Induced Hepatocyte-Like Cells

We previously described the generation of induced hepatocyte-like cells (iHeps) using the hepatic transcription factor Hnf1a together with small molecules. These iHeps represent a hepatic state that is more mature compared with iHeps generated with multiple hepatic factors. However, the underlying mechanism of hepatic conversion involving transgene dependence of the established iHeps is largely unknown. Here, we describe the generation of transgene-independent iHeps by inducing the ectopic expression of Hnf1a using both an episomal vector and a doxycycline-inducible lentivirus. In contrast to iHeps with sustained expression of Hnf1a, transgene-independent Hnf1a iHeps lose their typical morphology and in vitro functionality with rapid downregulation of hepatic markers upon withdrawal of small molecules. Taken together, our data indicates that the reprogramming state of single factor Hnf1a-derived iHeps is metastable and that the hepatic identity of these cells could be maintained only by the continuous supply of either small molecules or the master hepatic factor Hnf1a. Our findings emphasize the importance of a factor screening strategy for inducing specific cellular identities with a stable reprogramming state in order to eventually translate direct conversion technology to the clinic.