Abstract
Homology-directed gene editing of hematopoietic stem and progenitor cells (HSPCs) is a promising strategy for the treatment of inherited blood disorders, obviating many of the limitations associated with viral vector-mediated gene therapies. The use of CRISPR/Cas9 or other programmable nucleases and improved methods of homology template delivery have enabled precise ex vivo gene editing. These transformative advances have also highlighted technical challenges to achieve high-efficiency gene editing in HSPCs for therapeutic applications. In this review, we discuss recent pre-clinical investigations utilizing homology-mediated gene editing in HSPCs and highlight various strategies to improve editing efficiency in these cells.
Highlights
The modification or insertion of genes was initially proposed in the early 1970s as a curative approach for inherited disorders [1]
Colony forming unit assays reveal that Homology-Independent Targeted Insertion (HITI) does not result in lineage skewing, and HITI-edited hematopoietic stem and progenitor cells (HSPCs) transplanted into immunodeficient NSG mice comprised an average of 21% of engrafted human CD45+ cells within the bone marrow 18 weeks post-transplantation [120]
A burst of scientific advances have led to improved gene editing modalities in recent years
Summary
The modification or insertion of genes was initially proposed in the early 1970s as a curative approach for inherited disorders [1]. The elimination of portions of the 30 -LTR promoter and enhancer elements in these vectors provide a key self-inactivating (SIN) safety feature to alleviate concerns on possible recombination with endogenous HIV particles or unintended activation of proto-oncogenes near the genomic site of vector integration. For these SIN vectors, the efficiency of transgene expression is highly dependent on the addition of an internal ubiquitous promoter, and reduced or ectopic expression of the therapeutic gene can be limiting in disorders requiring robust or targeted transgene expression for a therapeutic effect. Med. 2021, 10, 513 in HSPCs and examine new strategies developed to improve gene editing efficiency to levels necessary for effective treatment of inherited blood disorders
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