Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment
Sydney Felker, … , Dylan Siniard, Punam Malik
Sydney Felker, … , Dylan Siniard, Punam Malik
Published May 9, 2022
Citation Information: JCI Insight. 2022;7(9):e151847. https://doi.org/10.1172/jci.insight.151847.
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Research Article Stem cells Transplantation

Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment

Abstract

Gene therapy involves a substantial loss of hematopoietic stem and progenitor cells (HSPC) during processing and homing. Intra-BM (i.b.m.) transplantation can reduce homing losses, but prior studies have not yielded promising results. We studied the mechanisms involved in homing and engraftment of i.b.m. transplanted and i.v. transplanted genetically modified (GM) human HSPC. We found that i.b.m. HSPC transplantation improved engraftment of hematopoietic progenitor cells (HPC) but not of long-term repopulating hematopoietic stem cells (HSC). Mechanistically, HPC expressed higher functional levels of CXCR4 than HSC, conferring them a retention and homing advantage when transplanted i.b.m. Removing HPC and transplanting an HSC-enriched population i.b.m. significantly increased long-term engraftment over i.v. transplantation. Transient upregulation of CXCR4 on GM HSC-enriched cells, using a noncytotoxic portion of viral protein R (VPR) fused to CXCR4 delivered as a protein in lentiviral particles, resulted in higher homing and long-term engraftment of GM HSC transplanted either i.v. or i.b.m. compared with standard i.v. transplants. Overall, we show a mechanism for why i.b.m. transplants do not significantly improve long-term engraftment over i.v. transplants. I.b.m. transplantation becomes relevant when an HSC-enriched population is delivered. Alternatively, CXCR4 expression on HSC, when transiently increased using a protein delivery method, improves homing and engraftment specifically of GM HSC.

Authors

Sydney Felker, Archana Shrestha, Jeff Bailey, Devin M Pillis, Dylan Siniard, Punam Malik

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Figure 1

Hematopoietic progenitor cells (HPC) have a preferential engraftment advantage when transplanted in the BM directly in NSG mice.

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Hematopoietic progenitor cells (HPC) have a preferential engraftment adv...
(A–D) Irradiated NSG mice were transplanted with MPB CD34+ HSPC that were transduced with a GFP-encoding LV vector (gene transfer 63%–66%) either i.v. or i.b.m. at the indicated cell doses. Human cell engraftment was analyzed by determining the percentage of human CD45+ (hCD45+) cells and GM hCD45+ (hCD45+GFP+) cells in the BM obtained via BM aspirate at 12 weeks to assess short-term engraftment (A and B) and from pooled BM from femurs, tibias, and iliac crests at 24 weeks to determine long-term human engraftment (C and D). Bars represent median engraftment ± 95% CI. Each symbol represents an individual mouse; n = 18–20 mice per cell dose per transplant method. Mice were transplanted using 4 unique MPB donors in 4 experiments; statistical analysis was performed using 1-way ANOVA comparing i.v. and i.b.m. groups at each cell dose with correction for multiple comparisons. (E–H) Lineage output of the human xenograft. BM was stained with antibodies specific for T cell lineage (hCD3), B cell lineage (hCD19), myeloid lineage (hCD33), and HSPC (hCD34) to determine the lineage output of the transplanted total HSPC (E and G) and GM HSPC (F and H) at 12 weeks and 24 weeks after transplant. Statistical analysis was performed using 2-way ANOVA. *P < 0.05, **P < 0.01.