The Effects Of Conditioned Medium From Placenta Derived Mesenchymal Stem Cells On The Viability Of Periodontal Ligament Cells From Extracted Teeth

Objective: The status of periodontal ligament cells(PDLCs)is critical for the healing of replanted teeth.Extra-oral time and storage media have a profound effect on the viability of PDLCs.Dry storage of avulsed teeth will have irreversible damage to PDLCs.Therefore,it has an important effect on the healing with a normal periodontal ligament to keep the avulsed teeth in a suitable storage medium to maintain the viability of PDLCs.Nowadays,study on the storage media of avulsed teeth still is a major issue in the field of dental trauma.The International Association of Dental Traumatology has recommended the Hank's balanced salt solution(HBSS)as a storage medium to preserve the PDLCs for avulsed teeth due to its capability to maintain vitality of PDLCs.However,it has some limitations in the clinical application.Placenta-derived mesenchymal stem cell-conditioned medium(PMSC-CM)contains numerous growth factors secreted by placenta-derived mesenchymal stem cells which are supposed to promote cell proliferation and migration,meanwhile,it can promote wound healing.The objective of the present study was to analyze the vitality of PDLCs following storage in PMSC-CM or HBSS,to evaluate the effectiveness of PMSC-CM as a storage medium for avulsed tooth,providing experimental and theoretical basis for finding a new storage medium.Methods: The extracted teeth were obtained from clinically healthy premolars extracted for orthodontic reasons and stored in either HBSS or PMSC-CM for 6 h,12 h or 24 h at the room temperature(10 teeth for each group).The PDLCs were obtained using whole teeth digestion.The ratio of apoptosis of PDLCs was determined by flow cytometry.Data were statistically analyzed by the least significance difference(LSD)method using SPSS 22.0 software.P values less than 0.05 were considered statistically significant.Results: After exposure to the two different experimental solutions at room temperature,the apoptosis rate and necrosis rate of PDLCs was increased with the length of storage duration.The PMSC-CM group showed the lower percentage of apoptotic and necrotic cells after 24 h,and higher percentage of viable cells,which was significantly different from the HBSS group(P < 0.01),while no significantly difference was found at 6 h and 12 h in two groups.Conclusions: Compared with HBSS,PMSC-CM showed better ability in maintaining the viability of PDLCs for a long period extra-oral time,and it could inhibit apoptosis and necrosis of PDLCs,which suggested that PMSC-CM could be used as a promising storage medium for avulsed teeth.