Mitochondrial Functions Maintain Scap Survival Following P. Endodontalis Infection

To investigate the effects of Porphyromonas endodontalis on the viability of stem cells from the apical papilla (SCAP) and explore the mechanism of mitochondrial functions and downstream signalling in maintaining SCAP survival, thus to provide insights into the biological basis of inflamed vital pulp therapy in immature permanent tooth. CCK8 and flow cytometric analysis were used to evaluate the proliferation and apoptosis of SCAP after P. endodontalis infection, using vascular endothelial cells (VECs) as control. Transcriptomic high-throughput sequencing was used to analysis the possible mechanism. Transmission electron microscopy and laser scanning confocal microscopy were used to observe the mitochondrial morphology and mitochondrial membrane potential. Western blot and inhibition experiments were performed to valid mitochondrial function in maintaining SCAP viability. After P. endodontalis infection, SCAP maintained cell viability and had higher cell viability and lower cell apoptosis compared to VECs. Transcriptomic high-throughput sequencing showed the differentially expressed mRNAs were enriched in mitochondrial membrane, depolarisation and fission. SCAP maintained stable mitochondrial morphology and higher mitochondrial membrane potential. Mitophagy related proteins (PRKN, PINK1, LC3, ABCD1) and mitochondrial fission protein, DRP1 were upregulated after treatment with P. endodontalis in SCAP. Cell viability of SCAP were decreased after inhibition mitophagy by 3-MA or mitochondrial fission by Midi1. SCAP could maintain cell viability after a short-duration P. endodontalis infection. The underlying mechanism of SCAP survival may be related to mitochondrial fission and mitophagy, which potentially serve as key protective mechanisms enabling SCAP to withstand P. endodontalis-induced cellular damage.