NUP98-HOXA10hd fusion protein sustains multi-lineage haematopoiesis of lineage-committed progenitors in transplant setting

Prolonged generation of multi-lineage blood cells in wild-type animals from pluripotent stem cells

Regenerating prolonged multi-lineage hematopoiesis from pluripotent stem cells (PSCs), an unlimited cell source, is a crucial aim of regenerative hematology. In this study, we used a gene-edited PSC line and revealed that simultaneous expression of three transcription factors, Runx1, Hoxa9, and Hoxa10, drove the robust emergence of induced hematopoietic progenitor cells (iHPCs). The iHPCs engrafted successfully in wild-type animals and repopulated abundant and complete myeloid-, B-, and T-lineage mature cells. The generative multi-lineage hematopoiesis distributed normally in multiple organs, persisted over 6 months, and eventually declined over time with no leukemogenesis. Transcriptome characterization of generative myeloid, B, and T cells at the single-cell resolution further projected their identities to natural cell counterparts. Thus, we provide evidence that co-expression of exogenous Runx1, Hoxa9, and Hoxa10 simultaneously leads to long-term reconstitution of myeloid, B, and T lineages using PSC-derived iHPCs as the cell source.

Co-Expression of Runx1, Hoxa9, Hlf, and Hoxa7 Confers Multi-Lineage Potential on Hematopoietic Progenitors Derived From Pluripotent Stem Cells

The intrinsic factors that determine the fundamental traits of engraftment ability and multi-lineage potential of hematopoietic stem cells (HSCs) remain elusive. The induction of bona fade HSCs from pluripotent stem cells (PSCs) in dishes is urgently demanded but remains a great challenge in translational medicine. Runx1, Hoxa9, Hlf, and Hoxa7 are developmentally co-expressed during endothelial-to-hematopoietic transition and adult haematopoiesis. However, the expression of these factors fails to be turned on during in vitro hematopoietic induction from PSCs. Here, we established an inducible gene over-expression embryonic stem cell (ESC) line in which exogenous Runx1, Hoxa9, Hlf, and Hoxa7 genes were tandemly knocked in. A population of induced hematopoietic progenitor cells (iHPCs) expressing Kit and Sca1 surface markers were successfully obtained in vitro from the gene edited-ESC line. Upon transplantation of the Runx1-Hoxa9-Hlf-Hoxa7 ESC-derived iHPCs into irradiated immunodeficient mice, they can dominantly contribute to B cells, low proportions of T cells and myeloid cells. However, Runx1-Hoxa9-Hlf ESC-derived iHPCs only produced B lineage cells with extremely low contributions. Our study unveils that the coordination of Runx1, Hoxa9, Hlf, and Hoxa7 led to generation of the hematopoietic progenitors with the capacity of multi-lineage hematopoietic reconstitution in the immunodeficient recipient mice.

NUP98-HOXA10hd fusion protein sustains multi-lineage haematopoiesis of lineage-committed progenitors in transplant setting

Objectives

Exploring approaches of extending the haematopoiesis time window of MPPs and lineage‐committed progenitors might produce promising therapeutic effects. NUP98‐HOXA10hd (NA) fusion protein can expand long‐term haematopoietic stem cells (HSCs) and promote engraftment competitiveness without causing obvious oncogenesis. Our objectives were to investigate the roles of NA fusion protein in MPP and downstream lineage‐committed progenitor context.

Material and Methods

300 sorted MPPs (Lin⁻CD48⁻c‐kit⁺Sca1⁺CD135⁺CD150⁻) were mixed with 5 × 10⁵ total BM helper/competitor cells and injected into irradiated recipients. For secondary transplantation, 5 × 10⁶ total BM cells from primary recipient mice were injected into lethally irradiated recipients. NA‐MPP recipient mice were sacrified for flow cytometric analysis of bone marrow progenitors at indicated time points. Sorted MPPs and myeloid progenitors were used for RNA‐seq library preparation.

Results

We showed that NA‐expressing MPPs achieved significantly longer multi‐lineage haematopoiesis (>44‐week) than natural MPPs (20‐week). NA upregulated essential genes regulating long‐term haematopoiesis, cell cycle, epigenetic regulation and responses to stress in MPPs. These molecular traits are associated with the earlier appearance of a Sca1^‐c‐kit⁺ myeloid progenitor population, and more abundant cellularity of lineage‐committed progenitor as well as bone marrow nucleated cells. Further, the NA‐derived primary bone marrow cells, which lack NA‐LSK cells, successfully repopulated secondary multi‐lineage haematopoiesis over 20 weeks.

Conclusions

This study unveiled that NA fusion protein promotes MPP and lineage‐committed progenitor engraftment via extending long‐term multi‐lineage haematopoiesis.