Engineered stem cells may provide ‘universal’ donor cells for sickle cell disease
ATLANTA — A panel of customized induced pluripotent stem cells may allow for more efficient and safe matching of blood for transfusions among patients with sickle cell disease, according to a study presented during the plenary session of the ASH Annual Meeting and Exposition.
The induced pluripotent stem cells (iPSCs) were reprogrammed from rare donors or genetically engineered using CRISPR/Cas9 to express rare blood group antigen phenotype s or combinations that are near impossible to find as donor red cells.
Although patients with sickle cell disease require frequent blood transfusions , the development of uncommon antibodies in their blood — largely due to RH gene variation — makes it challeng ing to find safe donor blood. Even if patients receive blood that is Rh matched by standard blood bank tests, the variants increase the risk for forming Rh antibodies with transfusions. If a patient receives incorrectly matched blood, their immune system will destroy the transfused red cells.
Transfusable blood for patients who require perfectly matched Rh is rare, and routinely RH genotyping all donated blood to prepare for these patients is time consuming and costly. RH variants occur in only 1% to 2% of the general population, but have been observed in more than half of cohorts with sickle cell disease.
Stella T. Chou, MD, assistant professor of pediatrics at Children’s Hospital of Philadelphia, and colleagues hypothesized that they could reprogram human iPSCs from rare donors or genetically engineer them to produce standard red cell reagents to identify patients with complex antibodies.
“It has been more than 10 years since iPSCs have been available, but we have yet to see applications for blood diseases that improve how we care for our patients,” Chou said in a press release. “Using this panel, we would be able to more quickly identify what antibodies the patient has made, informing us what kind of blood we have to give them. It means we’ll be able to improve their ability to be transfused safely and reduce delays in their care.”
Previously, human iPSC-derived red blood cells had been largely developmentally primitive red cells that differed from donor-derived red cells with high levels of embryonic globin expression, large size and an inability to enucleate in culture.
Chou and colleagues sought to improve iPSC hematopoietic differentiation protocols by developing a panel that included:
- Rh-null cells;
- cells lacking hrS, a high prevalence Rh antigen;
- cells expressing a partial C antigen and lacking hrB, a high prevalence Rh antigen; and
- cells expressing low-prevalence Rh antigens V and VS and lacking hrB.
In addition to using blood from donors with rare RH variants, researchers also genetically engineered some iPSCs using CRISPR/Cas9 to create blood cells with specific combinations of antigens — specifically, they disrupted RHCE alleles by a large deletion from exon 1 to exon 2 or via insertion-deletion mutations. For lines lacking high-prevalence Rh antigens, researchers reprogrammed group O donor cells whose genotypes were heterozygous for RHD*DAU0/RHCE*ceMO and RHD*DOL/RHCE*ceBI, homozygous for RHD*DIIIa-CE(4-7)-D/RHCE*ceS and homozygous for RHD/RHCE*ce733G.
Researchers assessed red blood cell agglutination by gel card assay of untargeted group O, D+, E– and e+ and the genetically engineered Rh-null iPSCs using standard anti-D, -E and -e reagents for Rh typing. They found the untargeted O and D+ red blood cells agglutinated with anti-D and anti-E, whereas the engineered Rh-null iPSC red blood cells did not show agglutination with all three antibodies.
Further refinement of this technique could allow for the development of a simple, cost-effective screening tool that can be used at local blood blanks to help quickly identify Rh-matched blood for patients with sickle cell disease.
“In the future, when technology for scale-up is available, Rh-null iRBCs could be used as ‘universal’ donor cells for therapeutic applications,” the researchers wrote. – by Alexandra Todak
Posocco D, et al. Abstract 3. Presented at: ASH Annual Meeting and Exposition; Dec. 9-12, 2017; Atlanta.
Disclosure: The authors report no relevant financial disclosures.