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Titration of Bone Marrow Cell Infusion in a Preclinical Model of Composite Tissue Allotransplantation
Galen S. Wachtman, MD, Rishi Jindal, MD, Jignesh V. Unadkat, MD, Vijay S. Gorantla, MD, PhD, Stefan Schneeberger, MD, Gerald Brandacher, MD, W.P. Andrew Lee, MD
University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
2010-03-31
Presenter: Galen S. Wachtman, MD
Affidavit:
Director Name:
Author Category: Resident/Fellow
Presentation Category: Basic Science Research
Abstract Category: General Reconstruction
Introduction: Composite tissue allotransplantation (CTA) is a clinical reality, but lifelong multi-drug immunosuppression is required for graft survival, carrying high risk for serious side effects. Current research focuses on developing strategies to minimize immunosuppression. We have developed a model of heterotopic hindlimb transplantation in Yucatan miniature swine using recipient conditioning, donor bone marrow infusion, and monotherapy immunosuppression. We aim to determine the optimal dose of bone marrow cells to be infused to establish stable mixed chimerism.
Methods: Complete SLA-mismatched miniature Yucatan swine were used, with male donors and female recipients. Recipients underwent 100cGy total body and 700cGy thymic irradiation. Three groups of 4 animals received 15, 30 and 60 million cells/kg of whole unmodified bone marrow. Flow cytometry evaluated cellular depletion after irradiation and chimerism assessed with Real Time PCR.
Results: There were no infectious complications or graft versus host disease. Animals show approximately 80% T cell, 100% B cell, and 35% myeloid cell depletion by flow cytometry, with recovery to normal by approximately 40 days. Chimerism was established in all animals after bone marrow cell infusion. However, microchimerism at day 9 was significantly increased for 60 million cells/kg (0.0003%, p=0.0008) versus 15 and 30 million cells/kg groups. Stable long-term microchimerism was achieved at all doses at experimental endpoints (1x10^6 %).
Conclusions: Total body and thymic irradiation results in immune cell cytodepletion which is non-toxic to swine. Stable long-term microchimerism was obtained in all groups; infusion of 60 million cells/kg provided a statistically significant increase in chimerism early after infusion.
