Inhibition of aldehyde dehydrogenase and retinoid signaling induces the expansion of human hematopoietic stem cells

Abstract

Aldehyde dehydrogenase (ALDH) is an enzyme that is expressed in the liver and is required for the conversion of retinol (vitamin A) to retinoic acids. ALDH is also highly enriched in hematopoietic stem cells (HSCs) and is considered a selectable marker of human HSCs, although its contribution to stem cell fate remains unknown. In this study, we demonstrate that ALDH is a key regulator of HSC differentiation. Inhibition of ALDH with diethylaminobenzaldehyde (DEAB) delayed the differentiation of human HSCs that otherwise occurred in response to cytokines. Moreover, short-term culture with DEAB caused a 3.4-fold expansion in the most primitive assayable human cells, the nonobese diabetic͞severe combined immunodeficiency mouse repopulating cells, compared with day 0 CD34 ؉ CD38 ؊ lin ؊ cells. The effects of DEAB on HSC differentiation could be reversed by the coadministration of the retinoic acid receptor agonist, all-trans-retinoic acid, suggesting that the ability of ALDH to generate retinoic acids is important in determining HSC fate. DEAB treatment also caused a decrease in retinoic acid receptor-mediated signaling within human HSCs, suggesting directly that inhibition of ALDH promotes HSC self-renewal via reduction of retinoic acid activity. Modulation of ALDH activity and retinoid signaling is a previously unrecognized and effective strategy to amplify human HSCs.retinoic acid ͉ self-renewal ͉ diethylaminobenzaldehyde ͉ long-term repopulating cells H ematopoietic stem cells (HSCs) possess the unique capacity to self-renew and give rise to all mature lymphohematopoietic progeny throughout the lifetime of an individual (1, 2). Several molecular pathways that regulate HSC self-renewal have now been identified, including Notch (3), HOXB4 (4), Wnt (5), and bone morphogenetic protein signaling pathways (6). The osteoblastic niche for HSCs within the bone marrow (BM) has also been characterized (7,8). Despite these advances in understanding HSC biology, clinical methods to amplify human HSCs have yet to be realized, and characterization of the pathways that regulate HSC self-renewal continues to evolve.Two decades ago, Colvin et al. (9,10) demonstrated that the intracellular enzyme, aldehyde dehydrogenase (ALDH), protected BM progenitors from the cytotoxic effects of cyclophosphamide by deactivation of its metabolite, 4-hydroxycyclophosphamide (9, 10). Several isoforms of ALDH have been identified, with ALDH1 being the primary isoform expressed within human hematopoietic progenitors (11,12). Recent studies have shown that human and murine hematopoietic progenitors can be isolated by using a fluorescently labeled dye specific for ALDH activity (13-16) and cord blood (CB) ALDH br lin Ϫ cells are enriched for nonobese diabetic͞severe combined immunodeficiency (NOD͞SCID) mouse repopulating cells [SCID-repopulating cells (SRCs)] (15, 16). Although these data demonstrate that ALDH is a selectable marker for human stem͞progenitor cells, the HSC-specific function of ALDH remains unknown. In the liver, ALDH1 contributes prima...

Aldehyde Dehydrogenase Discriminates the CD133 Liver Cancer Stem Cell Populations

“…15, 16). In particular, a functional role of ALDH was recently shown, in which diethylaminobenzaldehyde, a specific inhibitor of ALDH, deregulated human HSC self-renewal by interfering with endogenous retinoic acid biosynthesis (17). These data suggested that ALDH may regulate HSC function and is a potential therapeutic target.…”

Reactive oxygen species and aldehyde dehydrogenase activity in Hodgkin lymphoma cells

“…[1][2][3][4][5][6][7][8][9] Recent studies have pointed to high aldehyde dehydrogenase (ALDH) activity as a candidate CIC characteristic. [10][11][12][13][14][15][16][17][18][19][20] ALDH oxidizes retinol to retinoic acid in the early stages of stem cell differentiation. 11 High ALDH activity is detected in both physiological stem cells, such as hematopoietic and neural stem cells, 21,22 and CICs of human multiple myeloma, acute myeloid leukemia, and cancers of the lung and breast, 10,[12][13][14][15][16][17] indicating that ALDH activity may be a common marker for both normal and malignant stem cell populations.…”

Ex vivo expansion of hematopoietic stem cells

“…However, when the RA pathway is inhibited by a dominant negative RARα mouse HSC repopulation is also supported [174]. Diethylaminobenzaldehyde, an inhibitor of aldehyde dehydrogenase, the enzyme that is responsible for RA synthesis, induced a 3.4-fold of increase of repopulating cord blood HSCs after 7 d of culture, as determined by SCID repopulation assays [175,176]. Together, these results suggest that RA is an important modulator of HSC homeostasis.…”