Abstract 3418: Xenografted Human Amniotic Membrane-Derived Mesenchymal Stem Cells Acquired Immune Tolerance and Transdifferentiated Into Cardiomyocytes in Vivo
Background: We previously found that human amniotic membrane-derived mesenchymal stem cells (hAMC) had higher efficiency of cardiomyogenic transdifferentiation (CMT, 20 –70%) than marrow-derived MSC (0.3%) in vitro. On the other hand, hAMC with lack of expression of human leukocyte antigens (HLA) except HLA-G, a non-classical HLA class I molecule, has been thought to play an important role for immune tolerance during pregnancy. Although allografted hAMC is believed to acquire immune tolerance in situ, it remains uncertain whether the transdifferentiated hAMC which may express its own classical HLA molecules, can maintain immune tolerance or not. In the present study, we aim to show that xenografted hAMCs have a potential for CMT in vivo and the differentiated cardiomyocytes can acquire immune tolerance and survive in recipient’s hearts.
Methods and Results: We isolated hAMCs from human term placentas after deliveries of male infants, and identified the infant-derived cells to exclude contamination of maternal cells by sex chromosomal analysis. Flowcytometric analysis revealed that hAMCs were negative for HLA-DR, HLA class II molecule and weakly positive for HLA-C, classical HLA class I molecule. Western blot analysis revealed marked expression of HLA-G in vitro. Four weeks after transplantation of EGFP-labeled hAMCs to the infarcted hearts of Wistar rats untreated with immunosuppressant, many EGFP-positive and rod-shaped differeniated cardiomocytes with clear striations of cardiac troponin-I, were observed. Enzyme-linked immunoassay of sera and immunohistochemical analysis were performed to show the presence of soluble HLA-G and FOXP3-positive T cells.
Conclusions: Engrafted hAMCs were transdifferentiated into cardiomyocytes and survived more than a month. HLA-G has been known to suppress rejection and induce FOXP3-positive regulatory T-cells. FOXP3-positive regulatory T-cells which may be induced by HLA-G on hAMCs, may play an important role for induction of immune tolerance. Since hAMCs have a high ability of CMT and can acquire immune tolerance, they can be a promising cellular source for allotransplantation in regenerative medicine.