MIXED CHIMERISM OF CARDIOMYOCYTES AND VESSELS AFTER ALLOGENEIC BONE MARROW AND STEM-CELL TRANSPLANTATION IN COMPARISON WITH CARDIAC ALLOGRAFTS

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Abstract
Controversy persists about mixed chimerism (mCh) occurring in the hearts of patients after orthotopic cardiac transplantation in comparison with allogeneic bone marrow (BM) and peripheral blood stem-cell (PBSC) transplants. Cadaver hearts were examined after sex-mismatched transplantation by immunophenotyping combined with dual color fluorescence in situ hybridization (X and Y chromosome-specific probes). A striking disparity in the extent of mCh depending on the different transplantation procedures was recognizable. After allografting with PBSCs, 1.7% chimeric cardiomyocytes were detectable contrasting 5.4% of donor cells after full BM transplantation. In cardiac transplants, host-type endothelial cells (16.2%) and myocytes (14.3%) of the vessel walls were more often encountered than after BM and PBSC allografting. A sprouting of vascular structures into the donor heart after orthotopic cardiac transplantation has to be assumed, as does a pivotal role of the mesenchymal stem cells of the BM in the development of mCh.