Leukocytes lacking HLA class I alleles derived from hematopoietic stem/proge
nitor cells (HSPCs) that undergo copy number neutral loss of heterozygosity
of the short arm of chromosome 6 (6pLOH) or HLA allelic mutations are often
detected in patients with aplastic anemia (AA), but the precise mechanisms u
nderlying clonal hematopoiesis by such HLA(-) HSPCs remain unknown. To addre
ss this issue, we attempted to reconstitute the hematopoiesis of NOD-scid mi
ce with HSPCs derived from two AA patients who possessed B4002(-) and B5401(
-) leukocytes, respectively, as a result of 6pLOH and/or allelic mutations.
Two sets of three different iPS cell (iPSC) clones were established from the
patients' monocytes, which included wild-type, 6pLOH(+), and HLA-B(-) (B400
2[-] or B5401[-]) clones. Three-week cultures of the iPSCs in the presence o
f various growth factors produced hematopoietic cells consisting of 70% CD34
+ cells. 10 6 CD34 + cells were injected i
nto the femoral bone of C57BL/6.Rag2 mice harboring NOD-Sirpa (BRGS) which w
ere sacrificed at 9-12 weeks after the injection. 3.5 to 8.9 % human CD45 <S
UP>+ cells were detected in the BM, spleen, and peripheral blood, and
all retained original phenotypes. The percentages of donor chimerism were si
milar among the mice engrafted with the three-different iPSC-HSPCs. The dono
r-B cell functionality was confirmed by upregulation of human CD21, CD25 and
IgM expression after stimulation with pokeweed mitogen. These chimeric mice
should serve as a good model for studying the mechanisms of clonal hematopo
iesis by HLA(-) HSPCs in AA patients