Deciphering bone marrow engraftment after allogeneic stem cell transplantation in humans using single cell analyses.

BACKGROUND

Donor cell engraftment is a pre-requisite of successful allogeneic hematopoietic stem cell transplantation. Based on peripheral blood analyses it is characterized by early myeloid recovery and T- and B-cells lymphopenia. However, cellular networks associated with bone marrow engraftment of allogeneic human cells have been poorly described.

METHODS

Mass cytometry and CITEseq analyses were performed on bone marrow cells, three months post-transplant in patients with acute myelogenous leukemia.

RESULTS

Mass cytometry in 26 patients and 20 healthy controls disclosed profound alterations in myeloid and B-cell progenitors, with a shift towards terminal myeloid differentiation and decreased B-cell progenitors. Unsupervised analysis separated recipients into 2 groups, one of them being driven by previous GVHD (R2 patients). We then used single-cell CITEseq to decipher engraftment, which resolved 36 clusters, encompassing all bone marrow cellular components. Hematopoiesis in transplant recipients was sustained by committed myeloid and erythroid progenitors in a setting of monocytes-, NK cells- and T-cells mediated inflammation. Gene expression disclosed major pathways in transplant recipients, namely, TNFα signaling via NFκ-B, and interferon-γ response. The hallmark of allograft rejection was consistently found in clusters from transplant recipients, especially in R2 recipients.

CONCLUSION

Bone marrow cell engraftment of allogeneic donor cells is characterized by a state of emergency hematopoiesis in the setting of allogeneic response driving inflammation.

TRIAL REGISTRATION

Not applicable.

FUNDING

This study has been supported by the French National Cancer Institute (Institut National du Cancer): PLBIO19-239 and by an unrestricted research grant by Alexion Pharmaceutical.