Haematopoietic stem cell survival and transplantation efficacy is limited by the BH3-only proteins Bim and Bmf.
Bottom Line: Thereby, we revealed a critical role for Bim and Bmf as regulators of HSPC dynamics both during early engraftment and long-term reconstitution.HSPCs derived from wild-type donors were readily displaced by Bim- or Bmf-deficient or Bcl-2-overexpressing HSPCs as early as 10 days after engraftment.Finally, we provide proof of principle that RNAi-based reduction of BIM or BMF, or overexpression of BCL-2 in human CD34(+) cord blood cells may be an attractive therapeutic option to increase stem cell survival and transplantation efficacy.
Affiliation: Division of Developmental Immunology, Biocenter, Innsbruck Medical University, Innsbruck, Austria. email@example.comShow MeSH
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Mentions: To investigate the potency of human HSPCs with reduced levels of BIM or BMF to engraft and to compete against non-manipulated HSPCs we used newborn rag2−/−γc−/− mice and injected them intrahepatically with the progeny of 105 CD34+ cells transduced with lentiviruses either expressing shRNAs targeting Luciferase, BIM or BMF mRNA or a BCL-2 transgene. Transduction efficiencies were monitored before transplantation and found comparable between the vectors (Supporting Information Fig 6A). Eight weeks after transplantation overall human engraftment, defined by percentages of human CD45+ cells was similar in all groups analysed (Fig 7A and B). However, in all analysed organs a clearly higher proportion of GFP+ cells was detected when CD34+ donor cells expressed BIM or BMF shRNA, corroborating our results obtained in the murine in vivo system (Fig 7A and C). Notably, significant competitive advantages of GFP+ cells expressing BIM or BMF shRNAs could not only be observed in differentiated CD19+ B cells and CD33+ myeloid cells (Supporting Information Fig 6B and C) but was already visible in immature human CD34+ cells isolated from murine livers, BM and spleens (Fig 7A and D). The effects obtained by BCL-2 overexpression were similar (Fig 7B–D, right panels) indicating that BIM and BMF account for the majority of apoptosis induction during transplantation of CD34+ cells. Since intrahepatic transplantation may only partially mimic intraosseous engraftment occurring during clinical HSCT, we additionally injected human CD34+ cells intravenously into adult recipient mice. Results were comparable with those obtained in newborn mice with a clear engraftment advantage of CD34+ cells expressing BIM shRNA in all cell subsets analysed (Supporting Information Fig 7).
Affiliation: Division of Developmental Immunology, Biocenter, Innsbruck Medical University, Innsbruck, Austria. firstname.lastname@example.org