Fax +41 61 306 12 34 E-Mail karger@karger.com www.karger.com Original Paper Fetal Diagn Ther 2013;33:116–121 DOI: 10.1159/000346211 In utero Hematopoietic Stem Cell Transplantation in Canines: Exploring the Gestational Age Window of Opportunity to Maximize Engraftment Scott M. Petersen a Mariya Gendelman b Kathleen M. Murphy c Michael Torbenson c Richard J. Jones d Gail Stetten e Chris Bird b Karin J. Blakemore b a Division of Maternal-Fetal Medicine, Department of Gynecology and Obstetrics, Walter Reed National Military Medical Center, Bethesda, Md., and Departments of b Gynecology and Obstetrics, c Pathology, d Oncology and e Cytogenetics, Johns Hopkins University School of Medicine, Baltimore, Md., USA Introduction Many of the morbidities and limitations of postnatal bone marrow transplantation (BMT) could be avoided by utilizing in utero hematopoietic stem cell transplantation (IUHSCT). Disease candidates that look promising for human application of IUHSCT include many congenital enzyme, hematologic, and immune deficiencies [1, 2]. Complications of postnatal BMT include toxicities of re- quired immunosuppressive therapies and graft-versus- host disease (GVHD). Furthermore, less than 25% of re- cipients will have an HLA-matched donor. Limited engraftment has been a major obstacle in pre- vious attempts at human IUHSCT. To date, the only clear successes have been with X-linked severe combined im- munodeficiency likely secondary to a competitive advan- tage for donor cells [3, 4]. We have developed a model of IUHSCT in fetal canines [5] which, similar to humans, develop immunocompetence prior to birth [6], in order to investigate the roles of donor cell dosing and gesta- tional age in engraftment and GVHD. This study is an Key Words Bone marrow transplantation · Canine model · Hematopoietic stem cells · Transplantation Abstract Objective: In utero hematopoietic stem cell transplanta- tion (IUHSCT) is a promising therapy for a variety of con- genital disorders. Our objective was to determine the opti- mal time in gestation for IUHSCT in a canine model. Meth- ods: IUHSCT was performed in day 31–50 (term 63) fetal canines with CD34+ cells isolated from paternal bone mar- row at doses of 0.09–3.4 × 10 9 CD34+ cells/kg and T cells (CD3+/CD5+) from paternal blood at 0.11–1.1 × 10 9 cells/kg. Engraftment was assayed using PCR-based chimerism anal- ysis (SRY gene detection for female recipients, and unique microsatellite loci for both sexes). Results: Microchimerism and chimerism were present in multiple recipients across most gestational ages at transplant. Maximal engraftment was obtained in hematopoietic tissues in transplants per- formed at 42 days. At extremes of recipient gestational age, minimal to no engraftment was seen. Conclusion: Fetal age at the time of IUHSCT plays an important role in achieving engraftment in our canine model. Copyright © 2013 S. Karger AG, Basel Received: September 4, 2012 Accepted after revision: November 26, 2012 Published online: January 19, 2013 Scott M. Petersen, MD Division of Maternal-Fetal Medicine, Department of Gynecology/Obstetrics National Naval Medical Center, 8901 Wisconsin Avenue Bethesda, MD 20889 (USA) E-Mail scott.petersen  @  med.navy.mil © 2013 S. Karger AG, Basel 1015–3837/13/0332–0116$38.00/0 Accessible online at: www.karger.com/fdt Presented at the 26th Annual Meeting of the Society for Maternal- Fetal Medicine, Miami, Fla., 29 January to 4 February, 2006.