Thorac Cardiovasc Surg 2012; 60 - V244
DOI: 10.1055/s-0031-1297634

Strategies to effectively trace transplanted stem cells – How transgenes affect immune responses

A Grabosch 1, T Deuse 1, 2, TT Phan 3, 4, H Reichenspurner 1, RC Robbins 2, J Wu 5, S Schrepfer 1, 2
  • 1University Heart Center Hamburg, TSI-Lab, Hamburg, Germany
  • 2Stanford University, CT Surgery, Stanford, United States
  • 3Yong Loo Lin School of Medicine, Department of Surgery, Singapore, Singapore
  • 4Clinical Research Centre, CellResearch Corporation, Singapore, Singapore
  • 5Stanford University, CV Medicine, Stanford, United States

Aims: The occurrence of immunologic responses to transferred genes or genetically modified transplanted cells is a potentially limiting factor in biologic research and clinical therapy. The broad use of Luciferase (Luc) and Green Fluorescent Protein (GFP) as tracers to select for cells expressing other transgenes of interest prompted us to investigate the immunologic response stimulated by these markers.

Methods: Immune responses were simultaneously compared in four different groupes where transgene expression in multipotent human umbilical cord mesenchymal stem cells (hucMSCs) is driven by plasmid DNA, Minicircle DNA (MC) or Adenoviral (AdV) and Lentiviral particles.

Specific immune responses were monitored in immunocompetent Balb/c mice following i.m. administration of 1*106 manipulated hucMSCs.

Results: Both transgenes were expressed at comparable levels. Although GFP expression from a plasmid or MC elevated the levels of Th1-cell responses by 2 fold, only Luc induced a significantly stronger (p=0.021 for MC, p=0.032 for plasmid) IFN-gamma production compared to mock cells 5 days after injection as revealed by ELISpot. IL-4 secretion was not significantly changed in all test groups suggesting cell rejection is mainly via Th1-cell mediated mechanisms. The average days of cell rejection were 2–4 days for plasmid or MC transfected groups, whereas AdV and Lentivirus transduced groups survived significantly longer for up to 11.5 days (p<0.05) similar to wildtype hucMSCs. The damping of Luc-transgene expression was further associated with antigen-specific immune responses by the host.

Conclusion: Our data suggest that Luc expressing hucMSCs get rapidly rejected by the immune system under transient xenogenic conditions. In particular xenogenic Luc expressed from the Minicircle causes the strongest Th1-cell activation, suggesting Luc protein itself may be the cause of rejection. Stable expression of virally produced Luc or GFP has a comparably minor effect in the recipients making them more valuable tools for long-term research and expression in vivo.