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Background: The purpose of this study was to evaluate single-stranded conformational polymorphism (SSCP)-PCR utilizing two different regions of mitochondrial DNA (mtDNA) as a method to discriminate between donor platelets and recipient cells., Study Design and Methods: Twenty-eight mixtures of platelets (1:1 ratio) were prepared from eight randomly selected persons to simulate donor-recipient combinations after allogeneic platelet transfusion. The mtDNA was extracted from each donor and each prepared mixture. Four primer pairs were designed to amplify two regions of mtDNA, hypervariable region (HVR) 1 and 2. An SSCP-PCR method was developed to analyze the four different amplicons. In addition, the amplified DNA samples containing HVR1 and HVR2 mtDNA of the eight persons were sequenced by using dye-terminator cycle sequencing to determine mtDNA polymorphisms., Results: With four different primer pairs and SSCP-PCR, it was possible to discriminate between donor and recipient DNA in all 28 combinations. DNA sequencing confirmed that the suspected differences were localized within the amplicons examined by SSCP-PCR., Conclusion: SSCP-PCR analysis targeting the HVR1 and HVR2 mtDNA is a promising new method to potentially identify donor cells on the basis of mtDNA polymorphisms. The method does not require prior knowledge of sequence differences between donor and recipient and can be optimized to quantify the amount of residual transfused allogeneic platelets.

Human mitochondrial DNA polymorphisms are unique targets to discriminate nucleated cells and platelets between donor and recipient in the setting of transplantation or transfusion. We have previously used this approach to discriminate allogeneic platelets from autologous platelets after transfusion. In the present study, we used DNA sequencing to investigate polymorphisms present in two of the hypervariable segments (HVR1 and HVR2) found within the non-coding region of the mitochondrial genome among 100 plateletapheresis donors. Alignments were made with the Cambridge Reference Sequence (CRS) for human mitochondrial DNA (mtDNA). Combining the sequencing information of HVR1 and HVR2 we could demonstrate that, of the 100 investigated mtDNA samples, none was identical to the CRS. We found a total of 2-17 polymorphisms per donor in the investigated regions, most of them were basepair substitutions (563) and insertions (151). No deletions were found. Sixty-six of the 110 detected polymorphisms were detected in more than one sample. Seven polymorphisms are newly described and have not been published in the Mitomap database. Our results demonstrate that polymerase chain reaction analysis of the many polymorphisms found in the hypervariable region of mitochondrial DNA represents a more informative target than previously described mitochondrial polymorphisms for discriminating donor-recipient cells after transfusion or transplantation.

Background: Because mitochondria are abundant in white cells and are also present in platelets, polymorphic sequences in mitochondrial DNA (mtDNA) represent a unique target for polymerase chain reaction (PCR)-based detection of donor material., Study Design and Methods: A PCR assay was developed that uses sequence-specific primers (SSP) focused on two continent-specific mtDNA polymorphisms. Results were validated by the use of informative restriction endonucleases. Three commercially available methods to extract mtDNA from white cell-reduced human platelets was compared. In preparation for in vivo studies, in vitro mixing studies designed to mimic transfusion were conducted to investigate the performance of the SSP-PCR assay., Results: The gene sequences of two representative examples of amplicons obtained with the new SSP-PCR matched the sequence expected from the published genetic code. Fifteen individuals were classified as either positive (n = 6) or negative (n = 9) for the Asian polymorphism by the use of published primers known to flank the polymorphic site followed by digestion with appropriate restriction enzymes. Results with SSP-PCR were nearly perfectly concordant with those of restriction enzyme analysis. Although the use of three DNA extraction methods allowed the preparation of mtDNA that was suitable for PCR, large and consistent differences (ranging from 10- to 1000-fold) in endpoint sensitivity were found. In vitro mixing studies reproducibly documented that the SSP-PCR assay could detect as little as 1 percent of donor platelets mixed with recipient blood., Conclusion: PCR-SSP can be reliably used to identify human mtDNA polymorphisms. By optimization of the method of mtDNA extraction, the sensitivity of PCR-SSP assay was greatly increased. This assay should prove useful in investigations of allogeneic platelet transfusions without cell labeling. It may also be applied to studies of the donor cell microchimerism that follows transfusion or transplantation.