Stem Cell Factor/c-kit Signaling Mediated Cardiac Stem Cell Migration

Background The stem cells included embryonic stem cell and adult stemcell.Recently,it was reported that there are cardiac stem cells (CSCs) in the rat heartwhich accumulated in the atria and apex,and they could reconstitutewell-differentiated myocardium that are formed by blood-carrying new vessels andmyocytes by appropriate stimulation.However,most of the myocardial infarctioninvolved the anterior part of left ventricle,how do the CSCs migrate into theperi-infarcted areas after myocardial infarction (MI)? It remains entirely unknownabout the signal transduction involved in the migration of CSCs.There is c-kit on thesurface of the CSCs,and stem cell factor (SCF) is the ligand of the c-kit.Uponligand stimulation,c-kit receptors dimerize,activate its intrinsic tyrosine kinase,andautophosphorylate.The phosphorylatedc-kit receptor generates binding sites for SH2domain-containing proteins.Those proteins are subsequently activated orphosphorylated and further transduce signaling cascades that lead to various cellularresponses.Objective To investigate the role of SCF/c-kit signal in the migration ofCSC and reveal the potential involved signal factor.Methods (1) in vivo:Rat heart MI was induced by left coronary arteryligation.Both immunohistochemical staining and Western blotting analysis wasperformed to detect the expression of SCF protein,and RT-PCR was conducted forthe expression of SCF mRNA.Hemodynamic measurment was performed toevaluate the left ventricle function.And immunofluorescence was applied to detectthe migration of the transplantation BrdU-labeled CSCs.(2) in vitro:Cardiac stem cells were isolated from rat hearts,and a cardiac stem cell migration assay wasperformed using a 48-well chemotaxis chamber system.Western blotting wasperformed to detect the expression of p38MAPK and phosphorylated p38MAPK.Result On day 5 after MI in rats,the expression of stem cell factor (SCF)mRNA and protein was significantly increased in the peri-infarcted area,which wasmatched with more accumulation of CSCs in the region and improvement of cardiacfunction,which was blocked by p38 MAPK selective inhibitor SB203580.In in vitroexperiments,SCF induced CSCs migration in a concentration-dependent manner,and the antibody against SCF receptor (c-kit) blocked the SCF-induced CSCsmigration.Western blot analysis showed that the phosphorylated p38 MAPK(Phospho-p38 MAPK) was highly increased in the SCF-treated CSCs and theinhibition of p38 MAPK activity significantly attenuated SCF-induced the migrationof CSCs.Conclusion It demonstrated that SCF/c-kit signaling may mediate themigration of CSCs via activation of p38 MAPK.