CXCR4 induction in hematopoietic progenitor cells from Fanca^-/-, -c^-/-, and -d2^-/- mice

Objective: Bone marrow failure is a near-universal occurrence in patients with Fanconi anemia (FA) and is thought to result from exhaustion of the hematopoietic stem cell (HSC) pool. Retrovirus-mediated expression of the deficient protein corrects this phenotype and makes FA a candidate disease for HSC-directed gene therapy. However, inherent repopulation deficits and stem cell attrition during conventional transduction culture prevent therapeutic chimerism. Materials and Methods: We previously reported rapid transduction protocols to limit stem cell losses after ex vivo culture. Here we describe a complementary strategy intended to improve repopulation through upregulation of chemokine receptor (CXCR) 4, a principal factor in hematopoietic homing. Results: Using murine models with transgenic disruption of Fanca, -c, and -d2, we found that c-kit⁺ and sca-1⁺ progenitor cells express levels of CXCR4 comparable with those of wild-type littermates. Lineage-depleted progenitor populations rapidly upregulated CXCR4 transcript and protein in response to cytokine stimulation or hypoxia, regardless of genotype. Hypoxia conditioning of lineage-depleted Fancc^-/- progenitors also reduced oxidative stress, improved in vitro migration and led to improved chimerism in myeloablated recipients after transplantation. Conclusion: These studies provide evidence that CXCR4 regulation in progenitor cells from transgenic mice representing multiple FA genotypes is intact and that modulation of homing offers a potential strategy to offset the FA HSC repopulation deficiency.