In contrast to the short-term (ST) CD341 stem cells, studies have suggested that long-term (LT) hematopoietic stem cells (HSCs) found in the CD342 stem cell pool have trouble migrating and engrafting when introduced through IV. To understand why these deficiencies exist, we set out to fully elucidate the adhesion mechanisms used by ST and LT-HSCs to migrate to the bone marrow(BM). Specifically focusing on murine ST-HSCs (Flk22CD341) and LT-HSCs (Flk22CD342), we observed a distinctive expression pattern of BM homing effectors necessary for the first step, namely sialyl Lewis-X (sLex) (ligand for E-selectin), and the second step, namely CXCR4 chemokine receptor (receptor for SDF-1). sLex expression was higher on Flk22CD341 ST-HSCs (.60%) compared with Flk22CD342 LT-HSCs (,10%), which correlated to binding to E-selectin. Higher concentrations of CXCR4 were observed on Flk22CD341 ST-HSCs compared with Flk22CD342 LT-HSCs. Interestingly, the expression of CD26, a peptidase known to deactivate chemokines (ie, SDF-1), was higher on Flk22CD342 LT-HSCs. Given that both E-selectin–binding and CXCR4-mediated migration are compromised in Flk22CD342 LT-HSCs, we aimed to enhance their ability to migrate using recombinant human fucosyltransferase 6 (rhFTVI) and the CD26 inhibitor, Dip A (diprotin A). To this end, we observed that although LT-HSCs expressed low concentrations of sLex, they were able to engraft when transplanted into recipient mice. Moreover, although both CD26 inhibition and fucosylation enhanced migration of both HSC populations in vitro, only pretreatment of LT-HSCs with Dip A enhanced engraftment in vivo after transplantation into recipient mice. Remarkably, fucosylation of Flk22CD341 ST-HSCs consistently led to their ability to transplant secondary recipients. These data suggest that using fucosylation and Dip A to overcome the molecular disparity in adhesion mechanisms among ST-HSCs and LT-HSCs differentially influences their abilities to migrate and engraft in vivo and promotes the ability of ST-HSCs to engraft secondary recipient mice, the gold standard for testing functionality of LT-HSCs.
Bibliographical noteFunding Information:
The authors thank Simona Spinelli, Stefano Pietro, and Francesco Rottoli from the Animal Resource Core Laboratory (ARCL) facility at King Abdullah University of Science and Technology (KAUST), who were very helpful for animal-related studies and provided excellent training. Recombinant human FTVI was developed in a collaboration with Jae Man Lee and Takahiro Kusakabe during a Competitive Research Grant (OCRF-2014-CRG3-2276) from KAUST. Mass spectrometry was performed in Bioscience Core Laboratory facility at KAUST with the help of Huoming Zhang. The authors would like to thank Umm Habiba for her support in the management of the laboratory and thank the entire Cell Migration and Signaling Laboratory for their support and discussions. This work was supported by a KAUST Faculty Baseline Research Funding Program to J.S.M.
This work was supported by a KAUST Faculty Baseline Research Funding Program to J.S.M.
© 2022 by The American Society of Hematology.
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