Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in the production of intracellular retinoic acid (RA). Retinoic acid induces differentiation in hematopoietic cells. BMS493 is a pan inverse retinoic acid receptor (RAR) agonist.
BMS493 prevents retinoic acid-induced differentiation and preserves islet regenerative functions during expansion. Treatment with BMS493 increases the frequency of ALDHhi cells after expansion. After a 6-day expansion, BMS493-treated ALDHhi cells show a 2-fold increase in the number of cells available for transplantation compared with untreated controls. Treating human islets in culture with conditioned media generated from BMS493-treated ALDHhi cells show increased β-cell proliferation. When treated with BMS493, UCB-derived ALDHhi cells expanded for 6 days in culture show a twofold increase in the frequency of cells that retain high ALDH activity compared with untreated controls. Therefore, treatment with BMS493 during expansion increases the total number of ALDHhi cells available for transplantation without the loss of hematopoietic colony-forming progenitor capacity.
BMS493-treated cells show similar hematopoietic colony-forming capacity compared with untreated cells, with ALDHhi subpopulations producing more colonies than low aldehyde dehydrogenase activity subpopulations for expanded cells. Moreover, BMS493 could be used during ex vivo expansion to prevent RA-induced differentiation. BMS493-treated cells retain primitive cell surface marker expression. Expanded BMS493-treated cells reduce the expression of the mature hematopoietic cell surface marker CD38. Collectively, expanded BMS493-treated cells enhance retention of ALDHhi cells with primitive cell surface marker (CD34 and CD133) coexpression.
In summary, BMS493 is an inverse RAR agonist, inhibits RA-induced differentiation of UCB-derived ALDHhi cells in culture. Furthermore, BMS493 completely abrogates all-trans-retinoic (atRA)-induced DNA fragmentation, Sub-G1 fraction, and caspase-3 activation.