Therapeutically relevant engraftment of a CRISPR-Cas9–edited HSC-enriched population with HbF reactivation in nonhuman primates

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Science Translational Medicine  31 Jul 2019:
Vol. 11, Issue 503, eaaw3768
DOI: 10.1126/scitranslmed.aaw3768

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Enriching stem cells for gene editing

Gene editing using CRISPR-Cas9 offers the potential of targeted treatment for a variety of genetic diseases. These include inherited abnormalities of β hemoglobin, which can be indirectly targeted by increasing the amount of healthy fetal hemoglobin even without fully correcting the disease-causing mutation. Humbert et al. used CRISPR-based gene editing to modify hematopoietic stem cells from nonhuman primates, introducing a naturally occurring mutation that increases the amount of fetal hemoglobin. The authors successfully applied this method to a highly enriched population of stem cells in the primate model, suggesting the potential for translating this efficient editing technique to human patients.


Reactivation of fetal hemoglobin (HbF) is being pursued as a treatment strategy for hemoglobinopathies. Here, we evaluated the therapeutic potential of hematopoietic stem and progenitor cells (HSPCs) edited with the CRISPR-Cas9 nuclease platform to recapitulate naturally occurring mutations identified in individuals who express increased amounts of HbF, a condition known as hereditary persistence of HbF. CRISPR-Cas9 treatment and transplantation of HSPCs purified on the basis of surface expression of the CD34 receptor in a nonhuman primate (NHP) autologous transplantation model resulted in up to 30% engraftment of gene-edited cells for >1 year. Edited cells effectively and stably reactivated HbF, as evidenced by up to 18% HbF-expressing erythrocytes in peripheral blood. Similar results were obtained by editing highly enriched stem cells, defined by the markers CD34+CD90+CD45RA, allowing for a 10-fold reduction in the number of transplanted target cells, thus considerably reducing the need for editing reagents. The frequency of engrafted, gene-edited cells persisting in vivo using this approach may be sufficient to ameliorate the phenotype for a number of genetic diseases.

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