Proteomic Analysis and Identification of Paracrine Factors in Mesenchymal Stem Cell-Conditioned Media under Hypoxia

BACKGROUND/AIMS: We previously showed that a hypoxic environment modulates the antiarrhythmic potential of mesenchymal stem cells. METHODS: To investigate the mechanism by which secreted proteins contribute to the pathogenesis of antiarrhythmic potential in mesenchymal stem cells, we used two-dimensional electrophoresis combined with MALDI-TOF-MS to perform a proteomic analysis to compare the paracrine media produced by normoxic and hypoxic cells. RESULTS: The proteomic analysis revealed that 66 protein spots out of a total of 231 matched spots indicated differential expression between the normoxic and hypoxic conditioned media of mesenchymal stem cells. Interestingly, two tropomyosin isoforms were dramatically increased in the hypoxic conditioned medium of mesenchymal stem cells. An increase in tropomyosin was confirmed using Western blot to analyze the conditioned media between normoxic and hypoxic cells. In a network analysis based on gene ontology (GO) Molecular Function by GeneMANIA analysis, most of the identified proteins were found to be involved in the regulation of heart processes. CONCLUSION: Our results show that hypoxia up-regulates tropomyosin and other secreted proteins which suggests that tropomyosin may be involved in regulating proarrhythmic and antiarrhythmic functions.