The genetic profile of bone marrow transplanted patients in different vestiges of forensic interest

Abstract

The coexistence of cells with different genetic origins (donor and recipient) in a patient after receiving a hematopoietic stem cell transplantation (HSCT) is called chimerism. The study of chimerism after HSCT allows physicians to know the success or failure of the transplant, to predict the possibility of a relapse and to apply the opportune therapy. Due to the transdifferentiation capacity of hematopoietic stem cells (HSC) in non-hematological tissues, the vestiges from transplanted patients represent a challenge from a forensic perspective, since the interpretation of the genetic fingerprint can be misleading because of the presence of chimerism. The objective of this study is to examine the genetic profile in samples of forensic interest (nail and skin epithelial cells) of bone marrow transplanted patients and discuss the forensic and clinical implications. An observational and descriptive study has been developed in which the genetic profile of nail, epidermal cells and blood samples of patients receiving HSCT has been analyzed by the amplification and sequencing of 38 insertion/deletion polymorphisms (InDels) and 15 short tandem repeat polymorphisms (STRs). In this analysis, the age of patients and donors, the months elapsed from transplantation, the type of conditioning prior to the transplant and whether the patient has suffered graft-versus-host disease (GVHD) have been considered. Finally, the results obtained using the two identification techniques (InDels and STRs) have been compared in blood samples. The results indicate that chimerism can be detected in the DNA extracted from nail and skin epithelial cells of transplanted patients. The percentage of cells with donor DNA in nail and skin increases with time elapsed from the bone marrow transplantation, but the age of the patient or the donor, the type of conditioning and the presence of GVHD do not influence the proportion of chimerism. Finally, it has been found that, in blood samples of transplanted patients, the use of InDels and STRs for the calculation of chimerism can be used to achieve equivalent results.Human beings constantly lose epithelial cells, and these biological traces are frequently studied in the context of criminal investigation. In view of these results, it can be concluded that within a judicial context (e.g. when testifying as an expert witness) it is necessary to consider whether we are facing a possible transplanted patient or a person who has been a bone marrow donor.