In utero transplantation of autologous and allogeneic fetal liver stem cells in ovine fetuses

Objective The purpose of this study was to assess the feasibility of autologous stem cell transplantation in fetal sheep and to compare short-term engraftment of allogeneic and autologous fetal liver stem cells in an immunocompetent large animal model. Study design Fetal liver stem cells were collected from preimmune sheep fetuses with an open or ultrasound-guided technique. After being labeled with PKH26, the cells were transplanted intraperitoneally into allogeneic and autologous fetal recipients at 48 to 64 days of gestation. Engraftment was determined by flow cytometry and real-time polymerase chain reaction 1 to 2 weeks after transplantation. Results Fetal loss rate was 29% (allogeneic transplantation) and 73% (autologous transplantation). Engraftment of donor cells was found in all fetuses, with a level of ≤4.7% in fetal liver, spleen, bone marrow, blood and thymus. Overall, there was no difference between allogeneic and autologous grafts. Conclusion Autologous in utero transplantation of fetal liver stem cells in fetal sheep is feasible, but yields a high loss rate. Differences in the major histocompatibility complex between donor and recipient seems not to have a major impact on stem cell engraftment early in gestation; major histocompatibility complex–independent donor/host competition might be responsible for low engraftment in immunocompetent recipients.