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 3

The level of expression of CXCR4, not VLA4, on HSPC directs homing into BM with i.b.m. transplants.

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The level of expression of CXCR4, not VLA4, on HSPC directs homing into ...
(A–C) High CXCR4 expression on HPC mediates their preferential homing locally with i.b.m. transplant; CD34+ HSPC were transduced with a BFP LV vector, and the CD34+CD38+BFP+ HPC were sorted by flow cytometry 72 hours after gene transfer. HPC were blocked with AMD3100 (CXCR4 antagonist) or BIO5192 (VLA4 antagonist) before i.v. or i.b.m. delivery (A). Homing of hCD34+ cells was analyzed in the injected femur (IF) and non-IF for i.b.m. injected mice and in both femurs combined in i.v. injected mice. Data were normalized to i.v. injected control CD34+CD38+ cells, and the fold increase is indicated within the bar (B and C). n = 5–6 mice per group; statistical analysis was performed by 1-way ANOVA. (D–F) Induction of high CXCR4 expression on CD34+CD38– HSC enriched population via gene transfer confers them with a homing advantage despite higher abundance of CD34+CD38+ HPC. CD34+ HSPC were transduced with a BFP LV vector or a BFP-CXCR4 LV vector and sorted for transduced CD34+CD38–BFP+ cells and untransduced CD34+CD38+BFP– HPC at 72 hours. Transduced CD34+CD38– cells were mixed with untransduced CD34+CD38+ cells and transplanted i.v. or i.b.m., and homing of CD34+CD38–BFP+ cells into BM was analyzed at 20–22 hours (D). CXCR4 expression on injected cells at time of transplant is shown and the MFI on injected cells at time of transplant was as follows: CD34+CD38– control, 16,930; CD34+CD38+ control, 35,098; and CD34+CD38–CXCR4 transduced, 37,453. (E). Homing in BM is shown (F). n = 3–10 mice per experimental arm; statistical analysis was performed using 1-way ANOVA. *P < 0.05.