Abstract 12780: Reduction of Immunogenicity of Syngeneic Induced Pluripotent Stem Cells via Promotion of Cardiomyogenic Differentiation
Background: Induced pluripotent stem cell (iPSC) is a promising approach for the regeneration of self-cardiac tissue for replacement of damaged myocardium. However, it was recently reported that syngeneic iPSCs had significant immunogenicity due to the expression of 9 genes, such as Lce1f, Spt1, Cyp3a11, Zg16, Lce3a, Chi3L4, Olr1, Retn, and Hormad1, which can impair the survival and function of iPSCs after syngeneic transplantation. Here, we hypothesized that the magnitude of immunogenicity of syngeneic iPSCs is dependent upon the differentiation stage of the cells.
Methods: Cardiomyocytes were generated from the iPSCs of C57BL/6 (B6) mouse origin by Wnt-signaling molecules, followed by a purification process using a glucose-free medium in vitro. These cardiomyocytes showed markedly higher positivity for Nkx2.5 and alpha-MHC as compared to undifferentiated iPSCs and embryonic bodies (EBs) formed from the iPSCs of the same origin. Immunogenicity of each cell was assessed by mixed lymphocyte reaction (MLR) assay, in which the spleen cells of B6 origin were stimulated by the undifferentiated iPSCs, the EBs formed from the iPSCs, or the cardiomyocytes derived from the iPSCs of syngeneic origin. Subsequently, expression of the 9 genes was examined in each cell by means of real-time PCR.
Results: The MLR revealed a markedly greater proliferative reaction of B6 spleen cells against the syngeneic undifferentiated iPSCs (1169% ± 76% of baseline), compared to that against the syngeneic induced cardiomyocytes (171% ± 10% of baseline). In addition, Hormad1 expression in the EBs was 13% ± 1.8% of that in the undifferentiated iPSCs, whereas in the induced cardiomyocytes, Hormad1 expression was 0.95% ± 0.30% of that in the undifferentiated iPSCs (P < 0.0001). None of the cells expressed Cyp3a11 and Zg16. The expression of the other 6 genes was not significantly different among the cells.
Conclusions: Immunogenicity of the syngeneic iPSCs was serially decreased during the process of cardiomyogenic differentiation in vitro, in association with expression of Hormad1, which may produce immunogenicity of the iPSCs. A further purification procedure or modulation of Hormad1 expression might fully diminish the immunogenicity of the syngeneic iPSC-derived cardiomyocytes.
- © 2012 by American Heart Association, Inc.