Red blood cells
Researchers say they have generated the first human immortalized adult erythroid line that provides a sustainable supply of erythroid cells.
The team says this cell line, known as Bristol Erythroid Line Adult (BEL-A), is the first erythroid line to fully recapitulate normal erythropoiesis.
It produced mature reticulocytes that proved functionally and molecularly similar to adult reticulocytes cultured in vitro.
In addition, in vivo survival rates of BEL-A reticulocytes were similar to the survival rates of red blood cells (RBCs) from adult donors.
The researchers described their generation and testing of the BEL-A line in Nature Communications.
“Previous approaches to producing red blood cells have relied on various sources of stem cells, which can only presently produce very limited quantities,” said study author Jan Frayne, PhD, of the University of Bristol in the UK.
“By taking an alternative approach, we have generated the first human immortalized adult erythroid line (Bristol Erythroid Line Adult or BEL-A), and in doing so, have demonstrated a feasible way to sustainably manufacture red cells for clinical use from in vitro culture.”
Dr Frayne and her colleagues began with CD34+ cells from adult bone marrow. The researchers transduced these cells with an HPV16-E6/E7 construct and maintained them in the primary medium of the team’s erythroid culture system for 4 days.
On day 5, the researchers transferred the cells to an expansion medium containing doxycycline. After 190 days of continuous proliferation, the cells were frozen for storage.
Some cells were frozen throughout this time period as well, and all of the samples re-established efficiently in culture after thawing.
The researchers said these immortalized BEL-A cells were pro- to early basophilic erythroblasts, and there was no change in morphology over time.
After 100 days in continuous culture, the researchers transferred BEL-A cells to the primary erythroid culture medium containing doxycycline. The cells remained there for 6 days and were then moved to a medium without doxycycline to induce differentiation to mature erythroblasts and reticulocytes.
The researchers said the BEL-A cells exhibited an “unchanged ability to differentiate,” and were consistently able to expand.
The team also noted that BEL-A reticulocytes were similar to normal adult reticulocytes. The cells had similar diameters, comparable deformability indexes, and they bound and released oxygen in the same way.
The researchers tested the in vivo survival of BEL-A reticulocytes as well. They transfused BEL-A reticulocytes and donor RBCs into macrophage-depleted NSG mice. There was no difference in survival between the 2 cell types.
Dr Frayne and her colleagues said their results suggest immortalized erythroid lines can be used for the manufacture of RBCs for clinical use and for the study of erythropoiesis.
