Toward creating “caninized” mice: reconstitution of canine immune cells in immunodeficient mice

Objective: To generate "caninized" mice that could be used for investigating canine diseases and testing new therapies. Methods: In this experimental study, canine hematopoietic stem cells (HSCs) were isolated from bone marrow mononuclear cells from donor dogs using immunomagnetic sorting and an anti-canine CD34 antibody. Fresh or overnight-cultured HSCs were administered IV into sublethally irradiated immunodeficient mice (NOD scid γ strain) 4 to 20 hours after irradiation (median dose, 2.0 X 105 cells; n = 120) with noninjected irradiated controls (30). Engraftment was assessed by serum canine immunoglobulin M (IgM) measurement and flow cytometric analysis for canine leukocytes and immunohistochemical staining for T and B cells. Results: HSCs were enriched after sorting (median CD34+ cells, 87.6% vs 2.5% in bone marrow mononuclear cells). Canine IgM was measurable in sera of 49% of 94 surviving injected mice 19 to 42 weeks after irradiation (median IgM, 310 ng/mL; range, 18 to > 8,400 ng/mL). Higher serum canine IgM concentrations were detected in mice injected with fresh versus overnight-cultured HSCs. Low numbers of canine leukocytes and T and B cells were identified in the spleen and bone marrow with flow cytometry or immunohistochemistry. Conclusions: NOD scid γ mice can be engrafted with canine immune cells. Clinical Relevance: The creation of "caninized" mice is feasible, but efficiency of engraftment was low and requires further optimization before these mice can be used to model canine disease.