SOX17 Regulates Conversion of Human Fibroblasts Into Endothelial Cells and Erythroblasts by Dedifferentiation Into CD34+ Progenitor Cells

Lianghui Zhang, Ankit Jambusaria, Zhigang Hong, Glenn Marsboom, Peter T. Toth, Brittney-Shea Herbert, Asrar B. Malik, Jalees Rehman

Background -The mechanisms underlying the de-differentiation and lineage conversion of adult human fibroblasts into functional endothelial cells have not yet been fully defined. Furthermore, it is not known whether fibroblast de-differentiation recapitulates the generation of multipotent progenitors during embryonic development which give rise to endothelial and hematopoietic cell lineages. Here we established the role of the developmental transcription factor SOX17 in regulating the bi-lineage conversion of fibroblasts via the generation of intermediate progenitors. Methods -CD34(+) progenitors were generated following the de-differentiation of human adult dermal fibroblasts by overexpression of pluripotency transcription factors. Sorted CD34(+) cells were transdifferentiated into induced endothelial cells (iECs) and induced erythroblasts (iErythroblasts) using lineage specific growth factors. The therapeutic potential of the generated cells was assessed in an experimental model of myocardial infarction. Results -iECs expressed specific endothelial cell surface markers and also exhibited the capacity for cell proliferation and neovascularization. Induced erythroblasts expressed erythroid surface markers and formed erythroid colonies. Endothelial lineage conversion was dependent on the upregulation of the developmental transcription factor SOX17 whereas suppression of SOX17 instead directed the cells towards an erythroid fate. Implantation of these human bi-potential CD34(+) progenitors into immune-deficient NOD-SCID mice resulted in the formation of micro-vessels derived from human endothelial cells that were perfused with mouse and human erythrocytes. iECs generated from human fibroblasts showed upregulation of telomerase. Cell implantation markedly improved vascularity and cardiac function after myocardial infarction without any evidence of teratoma formation. Conclusions -De-differentiation of fibroblasts to intermediate CD34(+) progenitors gives rise to endothelial cells and erythroblasts in a SOX17-dependent manner. These findings identify the intermediate CD34(+) progenitor state as a critical bifurcation point which can be tuned to generate functional blood vessels or erythrocytes and salvage ischemic tissue.