Biodistribution and Safety of Human Multi-Chimeric Cells (HMCC) After Systemic Intraosseous and Intravenous Administration in the Experimental Mouse Model.

Cellular therapies provide promising options for inducing tolerance in transplantation of solid organs, bone marrow, and vascularized composite allografts. However, novel tolerance-inducing protocols remain limited despite extensive research. We previously introduced and characterized a Human Multi-Chimeric Cell (HMCC) line, created through ex vivo fusion of human umbilical cord blood (UCB) cells derived from three unrelated donors. In this study, we assessed in vivo biodistribution and safety of HMCC in the NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mouse model. Twenty-four NSG mice were randomly assigned to four groups (n=6/group) and received intraosseous (IO.) or intravenous (IV.) injections of 0.6 x 106 donor UCB cells or fused HMCC: Group 1 - UCB (IO.), Group 2 - UCB (IV.), Group 3 - HMCC (IO.), and Group 4 - HMCC (IV.). Hematopoietic phenotype maintenance and presence of HLA class I antigens in the selected lymphoid and non-lymphoid organs were assessed by flow cytometry (FC). Weekly evaluation and magnetic resonance imaging (MRI) assessed HMCC safety. Comparative analysis of delivery routes revealed significant differences in HLA class I percentages for IO.: 1.83%±0.79%, vs. IV. delivery: 0.04%±0.01%, p<0.01, and hematopoietic stem cell markers percentages of CD3 (IO.: 1.41%±0.04%, vs. IV.: 0.07%±0.01%, p<0.05), and CD4 (IO.: 2.74%±0.31%, vs. IV.: 0.59%±0.11%, p<0.01). Biodistribution analysis after IO. delivery confirmed HMCC presence in lymphoid organs and negligible presence in non-lymphoid organs, except for lung (IO.: 0.19%±0.06%, vs. IV.: 6.33%±0.56%, p<0.0001). No evidence of tumorigenesis was observed by MRI at 90 days following IO. and IV. administration of HMCC. This study confirmed biodistribution and safety of HMCC therapy in the NSG mouse model, both following IO. and IV. administration. However, IO. delivery route confirmed higher efficacy of engraftment and safety profile, introducing HMCC as a novel cell-based therapeutic approach with promising clinical applications in solid organ, bone marrow, and VCA transplantation.