Fare fibroblastlarının uyarılmış hepatositlere dönüşümünün geliştirilmesi

Transdifferentiation is the conversion of a differentiated cell to another differentiated cell type by the expression of lineage-specific transcription factors. Compared to directed differentiation of pluripotent stem cells, it is deemed to happen faster and be potentially safer for future clinical applications. However, in many contexts, the fidelity and efficiency of lineage conversion remains low, which suggest that there are a number of uncharacterized barriers to lineage conversion. We hypothesized that remodeling of the chromatin landscape during transdifferentiation may constitute one such barrier and modulating the activity of chromatin modifier complexes may increase the efficiency of lineage conversion. We have utilized the conversion of mouse fibroblasts to induced hepatocytes (iHeps) as a model system to test this hypothesis and to understand how chromatin modifications change during this process. Specifically, we expressed the two transcription factors Hnf4α and Foxa1 necessary for the conversion of fibroblasts, and treated the cells with small molecule inhibitors of various chromatin modifiers. We then tested both the efficiency and the quality of conversion at the gene expression level. We observed that removal of the activating H3K79 methylation mark through inhibition of DOT1L, and suppression of the repressive H3K27me3 mark through the inhibition of EZH2 are facilitators of this conversion. Inhibition of these two modifications led to the generation of induced hepatocytes that are more similar to mouse hepatocytes than untreated controls are in terms of hepatocyte marker expression. These findings provide insight into the chromatin modifications that are important in establishing the identity of engineered hepatocytes.