Transplantation of human CD34+ hematopoietic stem and progenitor cells into severe immunocompromised newborn mice allows the development of a human hemato-lymphoid system (HHLS) in vivo (Rongvaux et al. Ann. Rev. Immunol. 2013). While fetal liver- or cord blood- derived CD34+ cells lead to high levels of engraftment, adult donor-derived CD34+ cell transplantation usually led to low levels of engraftment in existing humanized mice models. We recently generated novel mouse strains called 3rd generation humanized mice (3rd gen. huMice) in which human versions of cytokines (M-CSF and TPO with or without IL-3/GM-CSF) are knocked into Balb/c Rag2-/-γC-/- strains (MISTRG or MSTRG, respectively). In addition, human Sirpα, which is a critical factor to prevent donor cell to be eliminated by host macrophages, is expressed as transgene in both strains (Rongvaux et al., Nat. Biotechnol. 2014).
To evaluate human adult CD34+ cell engraftment in 3rd gen. huMice, CD34+ cells obtained from peripheral blood after G-CSF administration (3.0 – 5.5 x105 cells) were i.h. injected into sub-lethally irradiated newborn MISTRG or MSTRG and NOD/scid/γC-/- (NSG) mice or Rag2-/-γC-/-hSirpαTg (RGS) mice as controls. Seventeen of 18 (94%) MISTRG/MSTRG mice showed human CD45+ cell engraftment (>1% of total CD45+ cells in BM) 10-16 weeks after injection, whereas 4 of 11 (36%) NSG/RGS mice supported human cell engraftment. Percentages of human cells in the BM of the engrafted MISTRG/MSTRG were 7- to 8 fold higher than in the BM of engrafted NSG/RGS mice (30.2% ± 6.9 vs 4.1% ± 0.9, respectively). MISTRG/MSTRG mice supported significantly increased numbers of non-classical monocytes and NKp46+ cells in BM compared with NSG/RGS mice. Moreover, we observed significantly increased numbers of CD34+ and CD34+CD38- cells, a population enriched for human early progenitor cells and HSCs, in the BM of MISTRG/MSTRG mice. In addition, MISTRG/MSTRG mice supported higher level of human thymocyte development compared to NSG/RGS mice. Besides lymphoid organs, we further observed increased human CD45+ cells, mostly myeloid lineage cells, in the liver and lung of MISTRG/MSTRG mice compared to NSG/RGS mice.
Taken together, this study demonstrates that our 3rd gen. huMice models support adult donor-derived HSC engraftment and development of myeloid as well as lymphoid lineage cells at high levels in primary lymphoid and non-lymphoid organs. These models thus have the potential for personalized studies of healthy hematopoiesis as well as hemato-immune system diseases from adult individuals.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.