Human Leukocyte Antigen I Knockdown Human Embryonic Stem Cells Induce Host Ignorance and Achieve Prolonged Xenogeneic Survival

Abstract

Background-Although human embryonic stem cells (hESC) have enormous potential for cell replacement therapy of heart failure, immune rejection of hESC derivatives inevitably would occur after transplantation. We therefore aimed to generate a hypoantigeneic hESC line with improved survival characteristics. Methods and Results-Using various in vivo, nonischemic, hindlimb xenotransplant models (immunocompetent and defined immunodefective mouse strains) as well as human in vitro T-cell and natural killer (NK)-cell assays, we revealed a central role for T cells in mediating hESC rejection. The NK-cell susceptibility of hESC in vivo was found to be low, and the NK response to hESC challenge in vitro was negligible. To reduce the antigenicity of hESC, we successfully generated human leukocyte antigen (HLA) I knockdown cells (hESC siRNAϩIB ) using both HLA I RNA interference (siRNA) and intrabody (IB) technology. HLA I expression was Ϸ99% reduced after 7 days and remained low for weeks. Cellular immune recognition of these hESC siRNAϩIB was strongly reduced in both xenogeneic and allogeneic settings. Immune rejection was profoundly mitigated after hESC siRNAϩIB transplantation into immunocompetent mice, and even long-term graft survival was achieved in one third of the animals without any immunosuppression. The survival benefit of hESC siRNAϩIB was further confirmed under ischemic conditions in a left anterior descending coronary artery ligation model. Conclusions-HLA I knockdown hESC siRNAϩIB provoke T-cell ignorance and experience largely mitigated xenogeneic rejection. By generating hypoantigeneic hESC lines, the generation of acceptable hESC derivatives may become a practical concept and push cell replacement strategies forward.

Pluripotent stem cells and tolerance induction in organ transplantation

“…The progressive immune response towards ESC was characterized by generation of alloreactive Th1 cells, development of donor ESC-specific antibodies [33] and accelerated rejection of a subsequent ESC infusion [34,35]. Similarly, transplantation of hESC to wild-type, natural killer (NK) cell deficient or B cell deficient mice led to vigorous T-cell-mediated rejection and failure to develop teratoma [8,36,37]. Although further studies are clearly required, these findings suggested that early predictions of low immunogenicity may ultimately proved premature, reflecting the inevitable complexities of the xenogeneic models used, rather than novel properties of the PSC cells per se.…”

Pluripotent Stem Cell Derived Cardiomyocytes for Cardiac Repair

“…While undifferentiated PSCs have some degree of immune privilege [106], their differentiated progeny including cardiomyocytes are immunogenic and clearly evoke an immune response in allogeneic recipients [16,107]. A number of exotic solutions to this problem have been proposed including the creation of isogeneic PSCs by somatic cell nuclear transfer [108], the creation of “universal donor” PSC lines via HLA engineering [109,110], and the induction of tolerance via bone marrow microchimerism [111,112]. Because iPSCs can be genetically matched to their recipient, they represent another theoretical solution to this problem, although the creation of “customized” autologous iPSC therapies would likely present a new set of practical hurdles in terms of scalability, economics, and regulatory burden.…”

Human embryonic stem cells (hESCs) for heart regeneration

“…Recently, MHC-I knock-down has been reported to be effective in profoundly reducing hESC rejection (Deuse et al , 2011), the residual MHC-I expression in MHC-silenced cells being expected to provide suffi cient protection against the negligible response of human natural killer cells to hESC challenge (Drukker et al , 2002).…”