In utero hematopoietic stem cell transplantation with haploidentical donor adult bone marrow in a canine model

Objective: Chimerism can be achieved in a canine model of in utero bone marrow transplantation with ≥ 1×10⁸ CD34⁺ haploidentical donor cells per kilogram without graft-versus-host disease. Study design: In utero bone marrow transplantation was performed by ultrasound-guided intraperitoneal infusion in 30- to 41-day-old canines with CD34⁺ selected cells from paternal bone marrow at doses of 1.3 × 10⁸ to 2.5 × 10¹⁰ CD34⁺ cells/kg. A method for marking control litter-mates was developed with intraperitoneal ethiodol. Postnatal studies included histologic, fluorescent in situ hybridization canine Y probe, and polymerase chain reaction-based chimerism analyses. Results: Term survival was 86% to 100% for transplantations ≥34 days versus 14% and 43% at 30 and 31 days. Microchimerism (< 1%) was demonstrated in tissues from 4 informative litters that included thymus, liver, skin, spleen, and intestine. Neither gestational age nor donor CD34 cell dosage altered the level of engraftment in these experiments. There was no evidence of graft-versus-host disease. Conclusion: In utero bone marrow transplantation in a canine model achieves microchimerism with high CD34⁺ cell doses.