Routing pathway of syngeneic donor hematopoietic stem cells after simple intra-amniotic delivery

Background: We sought to determine the pathway through which syngeneic hematopoietic stem cells (HSCs) delivered into the amniotic fluid can reach the fetal circulation. Methods: Lewis rat fetuses were divided in two groups based on the content of intra-amniotic injections performed on gestational day 17 (E17; term = E21-22): either a suspension of luciferase-labeled syngeneic HSCs ( n = 137), or acellular luciferase ( n = 44). Samples from placenta, chorion, amnion, amniotic fluid, umbilical cord, and 8 fetal sites were procured at 5 daily time points thereafter until term for analysis. Results: When controlled by acellular luciferase, donor HSCs were identified in the amnion, chorion, placenta, and amniotic fluid of fetuses receiving cells at all time points ( p = 0.033 to < 0.001), peaking first at the amnion and subsequently at the chorion and placenta. Cells could be detected in the fetal liver as early as day 1, progressively expanding to all the other fetal sites over time, in parallel to their increased presence in the chorion and placenta. Conclusions: The chronology of syngeneic donor hematopoietic stem cell trafficking after intra-amniotic injection is suggestive of controlled routing through the gestational membranes and placenta. Hematoge-nous donor cell routing is a constituent of transamniotic hematopoietic stem cell therapy, significantly expanding its potential applications. (c) 2022 Elsevier Inc. All rights reserved.