Staphylococcal Lipoteichoic Acid Promotes Osteogenic Differentiation Of Mouse Mesenchymal Stem Cells By Increasing Autophagic Activity

Background and Objectives:Bone and joint infections are one of the most common and serious complications that plague orthopaedic clinics.Staphylococcus aureus is a Gram-positive bacterium that is most commonly associated with bone infections.Mesenchymal stem cells(MSCs),which have the capacity of multi-directional differentiation potential and self-renewal,play an important role in normal bone development and maintenance of the balance of bone metabolism.Autophagy,a major self-protective mechanism of eukaryotic cells,plays a critical role in cellular repair and homeostasis.Lipteichoic acid(LTA)is a main component of S.aureus cell-wall.Lipopolysaccharide,the equivalent component to LTA in Gram-negative bacteria,was reported to stimulate autophagic activity in several studies.But effects of LTA on autophagy and osteogenic differentiation of MSCs remain unclear.This study was to explore the effect of staphylococcal lipoteichoic acid(LTA)on autophagy in mouse mesenchymal stem cells(MSCs),and then influence the osteogenesis through the change of autophagic activity.Materials and Methods:Mouse C3H10T1/2 cells were induced by osteogenic medium with the treatment of LTA at different concentrations(1,5,10 ?g/ml);the effect on osteogenesis were detected by alkaline phosphatase staining,alizarin red staining,real-time quantitative PCR and Western blotting;the autophagic activity were investigated by the expression of LC3-?and p62 protein;3-methyladenine(3-MA)were used as the autophagy inhibitor,and rapamycin(rapamycin,Rap)were used to activate autophagy.ResultCompared with control group,the positive rate of alkaline phosphatase was enhanced in the LTA groups;the formation of calcium nodules was increased simultaneously the expression of osteogenesis markers was significantly up-regulated with the LTA treatment on the mRNA and protein level;.The expression of LC3-? protein was increased in LTA groups while the expression of p62 protein was decreased.Inhibition of autophagy significantly reduced the effect of LTA on osteogenesis of MSCs;and the promotion of LTA on osteogenic differentiation was further enhanced when adding rapamycin to activate autophagic activity.ConclusionLTA enhanced autophagy of MSCs and promoted osteogenic differentiation of MSCs.3MA inhibited the promoting effect of LTA on osteogenesis of MSCs,while rapamycin enhanced the on osteogenic differentiation of MSCs promoted by LTA.LTA-induced autophagy promotes osteogenic differentiation of MSCs.It provides new insight of prevention and treatment for bone infection.