An HRL‐SC/HIF‐1α positive feedback loop enhances cell proliferation, migration and angiogenesis in dental pulp stem cells via PI3K/AKT signalling pathway

Abstract Aim Dental pulp stem cells (DPSCs) are essential for pulp regeneration but face low survival rates after transplantation. Genetic modification before transplantation is a promising solution to this issue. We aim to elucidate the biological function and regulatory mechanism of hypoxic lncRNA HRL‐SC in DPSCs. Methodology The biological functions of HRL‐SC and hypoxia inducible factor‐1α (HIF‐1α) in DPSCs were evaluated in vitro by cell proliferation, migration and tube formation assays. Subcutaneous transplantation in nude mice was used to evaluate the effect of HRL‐SC on DPSC viability in vivo. RNA sequencing and bioinformatics analysis, RNA immunoprecipitation, dual luciferase reporter gene assay, co‐immunoprecipitation, RNA fluorescence in situ hybridization, immunofluorescence and RNA and protein stability assays were used to explore the potential mechanism of HRL‐SC in DPSCs. Data were analysed by one‐way analysis of variance ( anova ) or Student's t ‐test, with a p <.05 indicating statistical significance. Results HRL‐SC, a hypoxia‐responsive lncRNA, enhanced the proliferation, migration and tube formation abilities of DPSCs. Subcutaneous transplantation of dental blocks revealed that HRL‐SC‐mediated DPSCs exhibited improved cell viability and elevated expression of Ki‐67 and CD31, along with the capacity to form vascular‐like structures. HIF‐1α was observed to induce transcription of HRL‐SC. Reciprocally, HRL‐SC bound to VHL, thereby inhibiting VHL‐mediated HIF‐1α ubiquitination, which resulted in a positive feed‐forward loop of HRL‐SC/HIF‐1α. RNA‐sequencing and functional analyses revealed that HRL‐SC was closely associated with hypoxia, angiogenesis, regeneration, integrin and PI3K/AKT signalling pathways. Furthermore, HRL‐SC was shown to stabilize ITGAV and ITGB3 through PTBP1. Finally, it was confirmed that HRL‐SC activated the PI3K/AKT signalling pathway via the integrin αvβ3/FAK and HIF‐1α/PDK1 axes. Conclusions DPSCs modified with HRL‐SC demonstrated enhanced cell viability via the PI3K/AKT signaling pathway and exhibited functional characteristics of endothelial cells, which may provide a novel strategy for the application of DPSCs in pulp regeneration.