Atf3 Deficiency Promotes Mesodermal Commitment and Enhances Endothelial Differentiation in Embryonic Stem Cells.

Background: Ischemic diseases have become a major threat to global health, with endothelial cell (EC) damage closely associated with their pathogenesis and progression. Cell therapies targeting endothelial repair have thus become a treatment approach of great interest, yet the procurement of clinically approved ECs for these applications has not been fully established. Modulating the expression of Atf3 (activating transcription factor 3) represents a potential strategy for deriving ECs from stem cells; however, its precise function in the development and differentiation of ECs from stem cells remains elusive. In the present study, we sought to elucidate the potential role of Atf3 in the differentiation of embryonic stem cells into ECs.

Methods: CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9) system was used to knockout Atf3 (Atf3KO [Atf3 knockout]) in mouse embryonic stem cells. EC differentiation was initially induced using the hanging drop method to promote embryoid bodies formation, followed by embryoid bodies attachment onto culture slides. The expression changes of EC markers during differentiation were assessed by RNA sequencing, Western blotting, immunofluorescence staining, flow cytometry, and reverse transcription quantitative polymerase chain reaction. Functional comparisons of differentiated ECs were performed by assessing LDL (low-density lipoprotein) uptake and NO production. Potential molecular mechanisms were further explored via bioinformatic analysis of RNA sequencing data.

Results: Atf3KO led to a significant upregulation in the expression levels of progenitor and mesoderm cell markers on days 3 and 6 of differentiation. By day 9, the expression of mature EC markers also exhibited a notable increase. Moreover, Atf3KO enhanced the functional properties of differentiated Atf3KO ECs. In addition, our findings revealed that the activation of the Rap1 signaling pathway, triggered by Atf3KO, contributed to ECs development and maturation.

Conclusions: Atf3KO directs embryonic stem cells toward the mesodermal lineage and activates the Rap1 signaling pathway, thereby promoting ECs development. These findings highlight a key role of Atf3 in regulating early stage of vascular endothelial development.