Transplantation of Fetal Liver Cells into Newborn Hemophilic Mice for Hemophilia A Cell Therapy

Abstract

[Background]: Hemophilia A cell therapy approaches in pediatric individuals require suitable FVIII-producing cell populations presenting stable engraftment potential. We previously showed that adult-derived FVIIIproducing cells, i.e. liver sinusoidal endothelial cells (LSEC) and hematopoietic stem cells (HSC), can be used for the treatment of adult hemophilia A (HA) mice. However, after transplantation in busulfan-conditioned newborn mice, adult LSEC/HSC cannot ef¿ciently engraft, while murine fetal liver (FL) hemato/vascular cells from day 11-13 of gestation (E11-E13) strongly reconstitute the hematopoietic compartment and showed multiorgan endothelial reconstitution potential while secreting FVIII. [Aims]: To investigate the engraftment of FL cells in newborn HA mice as a new strategy for the treatment of paediatric HA patients. [Methods]: We transplanted FL cells from E11-E13 GFP+ mice into newborn HA mice pre-treated with busulfan (FLE11-E13+BU). Control groups received FLE11-E13 GFP+ cells without busulfan pretreatment (FLE11-E13noBU) or PBS±BU. The engraftment level as well as the FVIII production and activity was assessed in recipients starting from 4 weeks and followed-up for 18 months after transplantation. Moreover, we evaluated the presence of anti-FVIII antibodies/inhibitors in plasma of transplanted mice. [Results]: In FLE11-E13+BU group we observed >60% engraftment in peripheral blood with concomitant FVIII activity (up to 16%) which remained stable up to 18 months after transplantation, while engraftment and FVIII activity were lower in absence of preconditioning. Additionally, FLE11-E13+BU group showed the presence of up to 4% of GFP+ LSEC 18 months after transplantation, demonstrating that transplanted FL cells in BU-conditioned newborn mice contributed in reconstituting the hemato/vascular compartment. Mice of FLE11-E13+BU and E13noBU groups did not develop anti-FVIII antibodies, not even after FVIII immunization. [Conclusions]: FL cells transplantation may provide a novel and highly promising preclinical model for HA treatment, paving the way for studies aiming at deriving long-term reconstituting ¿fetal-like¿ hemato/vascular progenitors from other sources (e.g. iPSC).