Objective:The aim of this study was to investigate the role of cyclic adenosine monophosphate (cAMP) signaling on the differentiation of stem cells from the apical papilla (SCAPs).Methods:SCAPs were cultured by enzyme digestion method.After adding activator (Forskolin) and inhibitor (H-89) into the culture of SCAPs in mineralization-inducing medium,calcium deposition was measured by alizarin red staining.QPCR was performed to measure the mRNA expression of mineralization-related genes.Results:When the cAMP signaling was activated,calcium deposition and the mRNA expression of ALP,OCN,OSX and RUNX2 increased sharply.After inhibiting the signaling,calcium deposition and the mRNA expression of ALP,OCN,OSX and RUNX2 decreased.Conclusion:The cAMP signaling may promote the odontogenic and osteogenic differentiation of SCAPs.

Cadmium is a non-essential,non-degradable heavy metal element,the accumulation of cadmium can cause kidney damage.The purpose of this study was to reveal the ferroptosis mecha-nism induced by cadmium exposure in porcine kidney PK-15 cells.First of all,cell viability of gradi-ent concentration of cadmium chloride(CdCl2)on PK-15 cells was detected by CCK-8 method to screen suitable work concentration of CdCl2.Secondly,PK-15 cells were treated with 10 μmol/L CdCl2 for 3,6 and 12 h.The contents of lactate dehydrogenase(LDH)malondialdehyde(MDA)were detected by colorimetry,the expression of ferroptosis related protein were detected by West-ern blot,and the content of ferrous ion(Fe2+)was detected by fluorescence probe.Finally,PK-15 cells were pretreated with 10 μmol/L HO-1 inhibitor zinc protoporphyrin(ZnPP)for 6 h,and then treated with 10 μmol/L CdCl2 for 12 h.The morphology of PK-15 cells was observed by phase contrast microscope and the expression of ferroptosis related proteins was detected by West-ern blot.The results showed that CdCl2 treatment caused a significant decrease in cell viability.The levels of LDH,MDA and Fe2+,the protein levels of Nrf2,HO-1 and ALOX5,and the expression level of FTH1 protein were significantly decreased in CdCl2 treatment cells(P＜0.01).ZnPP could significantly improve the ferroptosis of PK-15 cells induced by CdCl2 treatment.Compared with CdCl2 treatment cells,the cell morphology was significantly improved,the protein levels of Nrf2,HO-1 and ALOX5 protein were significantly decreased,and the protein levels of FTH1 protein were significantly increased in ZnPP pretreatment group(P＜0.01).The results showed that cad-mium induced iron overload and lipid peroxidation,which result in ferroptosis in PK-15 cells through Nrf2/HO-1 pathway.

Porcine kidney cell line(PK-15)with HO-1 gene knockout was constructed by CRISPR/Cas9 system to provide experimental materials for exploring the role and molecular mechanism of HO-1 in cadmium-induced ferroptosis in PK-15 cells.Three sgRNA targeting HO-1 gene were de-signed,synthesized and ligated to lentiviral vector Lenti CRISPRv2.The constructed lentiviral plas-mid was transfected into human embryonic cells(HEK293FT)to obtain recombinant lentivirus,which was used to infect PK-15 cells.The monoclonal cell line with HO-1 knockout was obtained by puromycin screening and limited dilution method.The knockout effect was analyzed by sequencing and Western blot detection.The HO-1 gene knockout cells were treated with 10 μmol/L cadmium chloride(CdCl2).The cell viability was detected by CCK-8 method,the cell morpholo-gy was observed by phase contrast microscope,and the content of ferrous ion(Fe2+)was detected by fluorescence probe.The results showed that sgRNA2 possessed the highest editing efficiency.The base insertion or deletion of HO-1 gene and the frameshift of the target gene occurred in all five knockout cells.Western blot results showed that no expression of HO-1 protein was detected,indicating that the PK-15 cell line with HO-1 gene knockout was successfully constructed.After CdCl2 treatment,compared with the control cells,the cell viability was significantly increased and the Fe2+content was significantly decreased in PK-15 cells with HO-1 gene deletion,indicating that HO-1 gene knockout could significantly alleviate the abnormal iron metabolism caused by cadmium treatment.In conclusion,this study successfully constructed a PK-15 cell line knocking out HO-1 gene by using CRISPR/Cas9 gene editing technique,and confirmed that HO-1 plays an important role in iron metabolism abnormality in PK-15 cells induced by cadmium treatment,which lays a foundation for further study on the regulatory mechanism of HO-1 in ferroptosis in PK-15 cells induced by cadmium exposure.