Researchers say they can increase the production of red blood cells (RBCs) in the lab by targeting a single gene—SH2B3.
The team used RNA interference (RNAi) to turn down SH2B3 in human hematopoietic stem and progenitor cells (HSPCs) and increased the yield of RBCs about 3- to 7-fold.
They also used CRISPR/Cas9 genome editing to shut off SH2B3 in human embryonic stem cell (hESC) lines, increasing the yield of RBCs about 3-fold.
The researchers noted that the method involving hESCs would be easier to use for large-scale production of RBCs.
Vijay Sankaran, MD, PhD, of the Broad Institute in Cambridge, Massachusetts, and his colleagues conducted this research and reported the results in Cell Stem Cell.
The researchers homed in on their target gene, SH2B3, after genome sequencing data revealed naturally occurring variations in SH2B3. These variations reduce the gene’s activity and increase RBC production.
“There’s a variation in SH2B3 found in about 40% of people that leads to modestly higher red blood cell counts,” Dr Sankaran said. “But if you look at people with really high red blood cell levels, they often have rare SH2B3 mutations. That said to us that here is a target where you can partially or completely eliminate its function as a way of increasing red blood cells robustly.”
So Dr Sankaran and his colleagues set out to see if they could use SH2B3 as a target to increase the yield of lab-based RBC production processes (as opposed to tweaking cells in culture by adding cytokines and other factors).
To do this, they first used RNAi to turn down SH2B3 in donated adult HSPCs and HSPCs from umbilical cord blood.
The team’s data confirmed that shutting off SH2B3 with RNAi skews an HSPC’s profile of cell production to favor RBCs. Adult HSPCs treated with RNAi produced 3- to 5-fold more RBCs than controls. And RNAi-treated HSPCs from cord blood produced 5- to 7-fold more RBCs than controls.
Using multiple tests, the researchers found the RBCs produced by RNAi were essentially indistinguishable from control cells.
Dr Sankaran and his colleagues recognized that this approach would be very difficult to scale up to a level that could impact the clinical need for RBCs. So, in a separate set of experiments, they used CRISPR to permanently shut off SH2B3 in hESC lines, which can be readily renewed in a lab.
The team then treated the edited cells with a cocktail of factors known to encourage blood cell production. Under these conditions, the edited hESCs produced 3 times more RBCs than controls. Again, the team could find no significant differences between RBCs from the edited stem cells and controls.
Dr Sankaran believes that SH2B3 enforces some kind of upper limit on how much RBC precursors respond to calls for more RBC production.
“This is a nice approach because it removes the brakes that normally keep cells restrained and limit how much red blood cell precursors respond to different laboratory conditions,” he said.
Dr Sankaran also believes that, with further development, the combination of CRISPR and hESCs could increase the yields and reduce the costs of producing RBCs in the lab to the level where commercial-scale manufacture could be feasible.
“This is allowing us to get close to the cost of normal donor-derived blood units,” he said. “If we can get the costs down to about $2000 per unit, that’s a reasonable cost.”
Previous research has shown it is possible to produce transfusion-grade RBCs, but the costs ranged from $8000 to $15,000 per unit of blood.
