Dental pulp stem cells (DPSC) are pluripotent stem cells with high differentiation potential isolated from dental pulp. Using DPSC for vascular regeneration may be a good option. Hypoxia inducible factor-1α (HIF-1α) is an upstream gene of vascular endothelial growth factor (VEGF), and the small ubiquitin like protease 1 (SENP1) can reverse the small ubiquitin like (SUMO) modification of HIF-1α. Through the regulation of SENP1/HIF-1α, good vascular regeneration characteristics have been demonstrated in many in vitro and in vivo experiments. The SENP1/HIF-1α signaling axis has varying degrees of promoting and inhibiting effects on many solid tumors. Although there is relatively little literature on the role of the SENP1/HIF-1α signaling axis in dental pulp stem cells, it can be determined that SENP1/HIF-1α plays an important role in the angiogenesis of dental pulp stem cells. This article will elucidate the SENP1/HIF-1α signaling pathway and its mechanism of promoting vascular differentiation of DPSC.

Streptococcus pyogenes Cas9 (SpCas9) has become a powerful genome editing tool, but has a limited range of recognizable protospacer adjacent motifs (PAMs) and shows off-target effects. To address these issues, we present a rational approach to optimize the xCas9 mutant derived from SpCas9 by directed evolution. Firstly, energy minimization with the Rosetta program was applied to optimize the three-dimensional structure of Cas9 to obtain the lowest energy conformation. Subsequently, combinatorial mutations were designed based on the mutations sites of xCas9 acquired during the directed evolution. Finally, optimal mutants were selected from the designed mutants by free energy ranking and subjected to experimental verification. A new mutant yCas9 (262A/324R/409N/480K/543D/694L/1219T) with multiple PAM recognition ability and low off-target effects was obtained and verified by DNA cleavage experiments. This mutant recognizes the NG, GAA and GAT PAMs and shows low off-target DNA cleavage activity guided by mismatched sgRNA, thus provides a gene editing tool with potential applications in biomedical field. Furthermore, we performed molecular dynamics simulations on the structures of SpCas9, xCas9 and yCas9 to reveal the mechanisms of their PAM recognition and off-target effects. These may provide theoretical guidance for further optimization and modification of CRISPR/Cas9 proteins.
CRISPR-Associated Protein 9/metabolism* ; CRISPR-Cas Systems/genetics* ; Clustered Regularly Interspaced Short Palindromic Repeats ; Gene Editing ; RNA, Guide/genetics* ; Streptococcus pyogenes/metabolism*