Fetal Hematogenous Routing of a Donor Hematopoietic Stem Cell Line in a Healthy Syngeneic Model of Transamniotic Stem Cell Therapy

Background/Purpose: In utero administration of hematopoietic stem cells (HSCs) has long been shown to have a variety of actual or potential clinical applications. However, this therapeutic principle is hindered by invasive and morbid techniques of cell delivery. We sought to determine whether donor HSCs could reach the fetal circulation after simple intra-amniotic delivery in large numbers in a syngeneic rat model of transamniotic stem cell therapy (TRASCET).

Methods: Pregnant Lewis rat dams underwent volume-matched intra-amniotic injections in all fetuses (n=90) on gestational day 17 (E17; term=E21-22) of either a suspension of commercially available Lewis rat HSCs labeled with a luciferase reporter gene (TRASCET; n=37 fetuses), or an acellular suspension of recombinant luciferase (n=53). Infused HSCs consisted of syngeneic cells that were at least 80% positive for CD34, CD117, SSEA3, SSEA4, Sox2, Oct4, and alkaline phosphatase on flow cytometry. Fetuses were euthanized at term for screening of luciferase activity at 8 select anatomical sites relevant to HSC-based therapies (Table). Positive luminescence was defined as relative light unit values exceeding the mean plus 2 standard deviations of blank wells. Statistical comparisons were by Fisher’s exact test and logistic regression.

Results: Among survivors (47/90; 52.2%), donor HSCs were identified selectively in the placenta, umbilical cord, bone marrow, and thymus (p=0.003, p<0.001, p<0.001, and p=0.009, respectively) when compared with acellular luciferase controls on univariate analysis (Table). In anatomical sites where multivariable analysis could be performed to account for fetuses from the same mother (placenta, umbilical cord, and thymus), these significant differences were still present (p=0.022, p=0.002, and p=0.008, respectively).

Conclusions: Donor hematopoietic stem cells can reach the fetal circulation, including the fetal bone marrow, after intra-amniotic delivery in large numbers in a syngeneic rat model. Transamniotic stem cell therapy may become a practicable, minimally invasive strategy for the prenatal administration of these cells.