Single-Cell RNA Sequencing of Sox17-Expressing Lineages Reveals Distinct Gene Regulatory Networks and Dynamic Developmental Trajectories

Development and aging of resident endothelial stem cells in pre-existing blood vessels

Organ-specific somatic stem cells play an important role in supporting tissue turnover and facilitating regeneration on injury. Hematopoietic stem cells are one of the most established organ-specific somatic cells that have been frequently used for transplantation therapy. Recently, there has been a growing interest in other organ-specific somatic cells, including vascular endothelial stem cells (VESCs). We have previously reported on the use of CD157 and CD200 as markers to isolate VESCs from adult mouse organs, particularly the liver. In this review, we aimed to summarize, based on our previous research, how CD157⁺CD200⁺ VESCs in the liver develop from the fetal stage to postnatal life, what transcriptional regulatory mechanisms govern them, and how VESCs change with aging.

Direct programming of human pluripotent stem cells into endothelial progenitors with SOX17 and FGF2

Transcription factors (TFs) are pivotal in guiding stem cell behavior, including their maintenance and differentiation. Using single-cell RNA sequencing, we investigated TFs expressed in endothelial progenitors (EPs) derived from human pluripotent stem cells (hPSCs) and identified upregulated expression of SOXF factors SOX7, SOX17, and SOX18 in the EP population. To test whether overexpression of these factors increases differentiation efficiency, we established inducible hPSC lines for each SOXF factor and found only SOX17 overexpression robustly increased the percentage of cells expressing CD34 and vascular endothelial cadherin (VEC). Conversely, SOX17 knockdown via CRISPR-Cas13d significantly compromised EP differentiation. Intriguingly, we discovered SOX17 overexpression alone was sufficient to generate CD34+VEC+CD31- cells, and, when combined with FGF2 treatment, more than 90% of CD34+VEC+CD31+ EP was produced. These cells are capable of further differentiating into endothelial cells. These findings underscore an undiscovered role of SOX17 in programming hPSCs toward an EP lineage, illuminating pivotal mechanisms in EP differentiation.