SEARCH

SEARCH BY CITATION

Keywords:

  • Mesenchymal stem cells;
  • Adult human bone marrow;
  • Aldehyde dehydrogenase;
  • Angiogenesis;
  • Autologous stem cell transplantation;
  • Cellular therapy;
  • Cord blood;
  • Endothelial stem cell;
  • Hematopoietic progenitors;
  • Neural stem cell

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

Flow cytometry has been used to detect cells that express high levels of the aldehyde dehydrogenase activity in normal tissues. Such ALDH bright (ALDHbr) cell populations have been sorted from human cord blood, bone marrow, mobilized peripheral blood, skeletal muscle, and breast tissue and from the rodent brain, pancreas, and prostate. A variety of hematopoietic, endothelial, and mutiltipotential mesenchymal progenitors are enriched in the human bone marrow, cord, and peripheral blood ALDHbr populations. Multipotential neural progenitors are enriched in rodent brain tissue, and tissue-specific progenitors in the other tissue types. In xenograft models, uncultured human bone marrow and cord ALDHbr cells home to damaged tissue and protect mice against acute ischemic injury by promoting angiogenesis. Uncultured cord ALDHbr cells also deploy to nonhematopoietic tissues and protect animals in CCl4 intoxication and chronic multiorgan failure models. Mouse ALDHbr cells and cells derived from them in culture protect animals in a chronic neurodegenerative disease model. Purifying ALDHbr cells appears to increase their ability to repair tissues in these animal models. Clinical studies suggest that the number of ALDHbr cells present in hematopoietic grafts or circulating in the blood of cardiovascular disease patients is related to clinical outcomes or disease severity. ALDHbr cells have been used to supplement unrelated cord blood transplant and to treat patients with ischemic heart failure and critical limb ischemia. ALDH activity can play several physiological roles in stem and progenitor cells that may potentiate their utility in cell therapy. STEM Cells 2011;29:570–575


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

Several allogeneic and autologous cell populations are in clinical development for use as agents to repair tissue damage. This concise review focuses on one of these cell populations that express high activity of the enzyme aldehyde dehydrogenase (ALDH). These cell populations known as ALDH bright (ALDHbr) cells are isolated from adult tissues by flow sorting. Jones et al. [1] developed the first method to sort living cells based on ALDH activity and demonstrated that human and mouse bone marrow hematopoietic progenitor cells (HPCs) expressed high levels of the enzyme. Storms et al. [2] synthesized a new substrate for the flow assay and characterized human cord blood (CB) HPC populations with high ALDH activity and low light scatter properties. Since the commercialization of the latter method, now widely known by its trade name Aldefluor (Aldagen, Inc, Durham, NC, www.aldagen.com.), it has been used to enrich populations of stem and progenitor cells from a variety of adult tissues, from primary cancers, and from cultured cells. This review briefly outlines the basis for selection of ALDHbr cells by cell sorting, explores roles that ALDH may play in stem cell physiology and tissue repair, and then details tissue repair activities that have been demonstrated in ALDHbr cells isolated from various tissues. Efforts to translate basic studies into clinical use of ALDHbr cells in regenerative medicine are summarized. The length limitation of a review precludes detailed discussion of other aspects of roles of ALDH in cells or the literature on expression of ALDH by tumor cells. However, several recent reviews of these topics are available [3–6].

HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

ALDH is a generic designation for a closely related superfamily of 19 human enzymes that can catalyze the pyridine nucleotide linked oxidization of aldehydes into carboxylic acids (Fig. 1). The individual members of the superfamily show substrate preferences for different aldehydes and some also have other functions unrelated to aldehyde oxidation [7]. A variety of compounds that inhibit ALDH activity is available; these compounds may inhibit the activities of several different ALDH gene products [4]. One inhibitor diethylaminobenzaldehyde (DEAB) is routinely used as an inhibitor of the Aldefluor reaction [2]. Figure 1 explains how the Aldefluor reaction is carried out and how ALDHbr cells are defined for cell sorting.

thumbnail image

Figure 1. Flow cytometric detection and isolation of aldehyde dehydrogenase (ALDH) bright (ALDHbr) cells. (A): This diagram depicts a generalized ALDH reaction in a living cell. ALDH isozymes mediate the pyridine nucleotide linked oxidation of the aldehyde R-CHO into the carboxylic acid R-COOH. The diagram shows the carboxylic acid in its ionized form at physiological pH. In the Aldefluor reaction, the substrate is biodipy FL-aminoacetaldehyde. Bodipy FL (a trademark of Molecular Probes, Inc.) gives a green fluorescence when illuminated with 488 nm laser light in a flow cytometer. This nonpolar substrate passively diffuses into cells and forms an intracellular pool. For simplicity, the pool and the reaction are shown in the cell cytoplasm; some ALDH isozymes are localized in other compartments. The ALDH reaction product bodipy-aminoacetic acid accumulates in cells in proportion to ALDH activity. The charged reaction product is normally trapped in cells, but it can be actively pumped from cells by ATP binding cassette proteins; these proteins are highly expressed in ALDHbr cells. Efflux can be controlled by keeping cells on ice during cell sorting [2]. (B): These cytograms illustrate the definition of ALDHbr cells in human bone marrow. An initial gate (not shown) uses forward and side scatter to differentiate the nucleated cell population from debris, aggregates, and erythrocytes. Side scatter versus green fluorescence cytograms are constructed from signals derived from nucleated cells. The cytogram on the left is from a control in which ALDH activity was inhibited with diethylaminobenzaldehyde (DEAB). Green fluorescence in this sample arises from the intracellular pool of substrate. The gate shown by the dotted circle defines a low side scatter cell population with little or no bodipy fluorescence. An identical cytogram of the cells in which the ALDH reaction proceeded without DEAB is shown on the right. The cells in the defined gate are defined as low side scatter, high ALDH activity ALDHbr cells, and are sorted. Similar gating strategies are used with other cell types. Abbreviations: ABC, ATP binding cassette; ALDH, aldehyde dehydrogenase; DEAB, diethylaminobenzaldehyde.

Download figure to PowerPoint

The full range of ALDH isozymes that oxidize Aldefluor under reaction conditions conventionally used to prepare samples for sorting of ALDHbr cells is unknown. However, immunochemical and DEAB inhibition studies suggested that ALDH1A1 is a major ALDH gene product over expressed in human bone marrow stem cells [8] and breast cancer stem cells and that ALDH1A1 activity is correlated with high Aldefluor activity [9]. Recently, RNA knockdown and antibody staining methods have implicated ALDH1A3, a molecule that is closely related to ALDH1A1, as the major contributor to Aldefluor oxidation in some ALDHbr breast cancer stem cells [10].

ALDH1A1 and/or ALDH3A1 may play an important role in defining the ALDHbr population is important, because these are two of four ALDH isoforms (ALDH1A1, ALDH1A2, ALDH1A3, and ALDH8A1) that oxidize retinaldehyde to retinoic acids [7]. One hypothesis suggests that the ALDH activity detected by Aldefluor influences stem cell and tissue repair cell activity through retinoic acids [11, 12]. Retinoic acids formed by the action of these four ALDH isoforms could bind to transcription factors that regulate many developmental programs [13, 14]. In principle, ALDH1a1 and ALDH1A3 could indirectly regulate cell activity and proliferation by controlling intracellular retinoid concentrations and could modulate the activity of other cells by releasing retinoids and/or paracrine factors under retinoid control. To date, ALDH1A1 is the only over expressed ALDH isoforms with retinoid oxidizing activity detected in ALDHbr populations sorted from normal tissues [12, 15]. However, targeted deletion of ALDH1A1 activity does not diminish Aldefluor oxidation by mouse bone marrow cells [16], suggesting that other ALDH isozymes can oxidize Aldefluor oxidization in these animals. Similarly, knocking down transcript levels for each of the 15 known zebra fish ALDH isoforms fail to reduce retinoid responsive expansion of ALDHbr hematopoietic progenitors [17]. The redundancy of ALDH isozymes and complexity of retinoid regulation have made it difficult to determine the full range of ALDH molecules that participate in retinoid mediated activities in cells.

ALDH isozymes that do not have oxidize retinoids, including mitochondrial ALDH isozymes, are also expressed in ALDHbr cells [10, 12, 15]. In all cases, these ALDH isozymes are coexpressed with ALDH1A1 or ALDH1A3 and whether these other isozymes contribute to the oxidation of the Aldefluor substrate is unknown. Several authors have pointed out that activities of ALDH unrelated to retinoid metabolism can be important in stem cell biology [3–6]. ALDH1A subfamily proteins and other ALDH isozymes oxidize aldehydes besides retinoids, including lipid oxidation products formed when cells are subjected to oxidative stress [7]. Several stem cell types, including some cancer stem cells, reside in and have metabolic pathways attuned to hypoxic environments [18], and the increase in ALDH activity may reflect the demands of surviving in such niches. Evidence consistent with this idea is presented below. Thus, ALDH isozymes over expressed in ALDHbr cell populations can regulate a variety of functions that are important in stem cell biology and tissue repair, but if and how these molecules contribute to tissue repair in the specific experimental and clinical contexts described in the following sections are largely unknown.

ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

ALDHbr populations derived from human CB [2, 19–24], bone marrow [1, 25–27], and cytokine mobilized peripheral blood [28–30] are highly enriched in early and lineage committed HPC and heterogeneous in expression of canonical HPC surface markers such as CD133 and CD34. All myeloid lineages, B-cells, and natural killer cells arise from ALDHbr CB cells in mouse xenograft models. ALDHbr CB populations include all of the long-term and most of the short-term cells that reconstitute hematopoiesis in these models. Recently, Liu et al. [24] demonstrated that T-cells also arise from highly purified cord ALDHbrCD34+ in nonobese, diabetic, severe combined immunodeficiency (NOD-SCID) γ−/− mice and that the pace and extent of short-term and long-term engraftment of the bone marrow and release of mature blood cells to the periphery depends on the dose of ALDHbrCD34+ cells administered.

Methods to detect and enrich ALDHbr HPCs are moving into the clinic. Measuring circulating ALDHbr cells has been used to monitor effectiveness of HPC mobilization and to detect differences in HPC subsets mobilized by different agents [29, 30]. Also, the number of ALDHbr cells in hematopoietic grafts is being explored as a metric of graft potency. In retrospective studies, the dose of ALDHbr cells administered to patients is inversely correlated with hematopoietic engraftment time [28, 29, 31]. Preliminary reports suggest that ALDHbr content of thawed cords, particularly if carried out prospectively on segments attached to cryopreserved CB units during unit selection, could be useful as a measure of the unit potency [32, 33]; formal prospective trials are anticipated. Finally, CB ALDHbr cell products have been used to supplement conventional allogeneic CB transplant in children in hopes of ultimately accelerating engraftment. A preliminary report suggests that the procedure is feasible and safe [34].

Two general points regarding the use of ALDHbr cells in regenerative medicine applications emerge from the studies of HPC activity in human ALDHbr cells. First, high ALDHbr activity discriminates different types of cells bearing CD34 and CD133 surface markers. For example, most of the CD34+ and CD133+ cells in CB do not express high ALDH activity, but as already noted, these ALDHlow populations contain short-term but not long-term reconstituting cells [19–24]. Similarly, ALDHbr cells from human bone marrow contain early multilineage progenitors that make megakaryocytes, but ALDHlow cells do not [25]. ALDHbr and ALDHlow population isolated from other tissues also exhibit important functional differences even though they express similar surface antigens, as discussed below.

Second, ALDHbr cells from hematopoietic graft sources are enriched in stem cells besides HPC. Approximately 10%–15% of the ALDHbr cells in cord [2, 18–24] and mobilized peripheral blood are CD34− [28–30]. These cells, CD34− and CD133− ALDHbr cells, have not been found to have any HPC activity in vitro or in vivo [19, 20, 28]. In bone marrow, approximately 50% of the ALDHbr cells are CD34− [25–27], and these cells are likely to have nonhematopoietic activity. ALDHbr cells from human bone marrow are highly enriched in progenitors that give rise to multipotent mesenchymal cells [25, 26]. Endothelial progenitor cells are also highly enriched in human ALDHbr populations from bone marrow [25, 26] and normal peripheral blood [35, 36]. In the context of tissue repair, human ALDHbr cells, especially cells derived from bone marrow, can provide a mixture of potential progenitor and, as discussed below, paracrine activities from a variety of stem cell types.

ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

Two studies in mouse xenograft models demonstrate that freshly isolated, uncultured human ALDHbr cells home rapidly to ischemic tissue damage. Nanoparticle labeled CB ALDHbr cells administered intravenously 1 day after left anterior ascending coronary artery occlusion, preferentially homed to the infarcted anterior surface of the heart and could be detected there for 3 days, but labeled ALDHlow cells were detected only in the spleen [37]. In a hind limb ischemia model [26], labeled bone marrow ALDHbr cells were administered intravenously 1 day after permanent ligation of the blood supply to the right hind limb, and animals were imaged after transplant. Labeled ALDHbr cells were specifically detected at the ischemic lesion and persisted there for up to 7 days.

In both these models, ALDHbr cells that homed to ischemic sites mediated local formation of new blood vessels. In the coronary model, engraftment with ALDHbr cells, but not ALDHlow cells, led to an increase in the number of large diameter mouse blood vessels specifically in the infarcted area of the heart. No improvement in cardiac function was noted. In the hind limb model, perfusion of the ligated limb increased 7 days after infusion of the ALDHbr cells and increased steadily to >80% of control level over the next 2 weeks. Restoration of perfusion was associated with a twofold increase in capillary density at the ligation site. As in the coronary model, few human cells were detected in the damaged leg 3 weeks after transplantation. Transplantation with ALDHlow cells or with unsorted bone marrow mononuclear cells did not restore tissue perfusion or increase in capillary density. These results show that ALDHbr cell populations contain the angiogenic cell compartment of human bone marrow and CB and that these cells can stimulate formation of new blood vessels at sites of ischemic injury.

Because human cells did not persist in large numbers at injury sites in these ischemic injury models, angiogenesis was attributed to elaboration of angiogenic factors by the transplanted ALDHbr cells. Smith et al. [38] have reported that human bone marrow ALDHbr cells express angiogenic cytokines, that expression of these cytokines is upregulated by hypoxia, and that medium conditioned by these cells can protect endothelial cells from ischemic damage. Thus, ALDHbr cell populations have a variety of progenitor cell activities and can respond to ischemic tissue damage through paracrine mechanisms.

In the hind limb ischemia study, unsorted bone marrow cells did not increase limb perfusion or capillary density even though the dose administered contained two- to fourfold more ALDHbr cells than the angiogenic ALDHbr preparations. This suggests that ALDHlow cells in human bone marrow can inhibit the homing and/or angiogenic activity of ALDHbr cells and that sorting potentiates angiogenic activity. This provides a rationale for sorting ALDHbr cells from bone marrow for potential therapeutic uses.

ALDHbr cell technology is moving into the clinic in the context of cardiovascular medicine and ischemic diseases. Povsic et al. [35, 36] reported that the number of ALDHbr cells circulating in the blood of cardiovascular patients was inversely correlated with the extent of coronary artery disease. This group suggested that circulating ALDHbr cell levels could be used to assess risk of cardiac disease and to monitor the efficacy of therapeutic interventions. The number of ALDHbr cells in the bone marrow of noncardiac patients undergoing hip replacement remains reasonably constant, but peripheral blood ALDHbr cells varied with age [39]. Thus, unless disease or medical treatment depletes the bone marrow ALDHbr compartment [40], ALDHbr populations from elderly patients should be accessible for use in autologous cell therapy. Clinical trials testing the feasibility and safety of using uncultured autologous bone marrow-derived ALDHbr cell populations in treating critical limb ischemia [41] and ischemic heart failure [42] have been completed; preliminary reports suggest that ALDHbr cells may improve perfusion of ischemic leg or heart tissue.

OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

Cells derived from uncultured CB ALDHbr cells during a 2 to 3-month period after transplantation can home to several nonhematopoietic tissues in response to chronic injury caused by genetic lysosomal storage disease [43] and by CCl4-induced liver damage [44] in mouse xenograft models. Such dispersion of human cells to tissues was not observed in animals engrafted with ALDHlow cells. In the intoxication model, prior engraftment with ALDHbr cells reduced mortality to 58% when compared with untreated animals and animals receiving ALDHlow cells. As human cells did not persist in large numbers in the liver, the authors suggested that the cells derived from the ALDHbr cells protected engrafted mice by secreting paracrine factors.

ALDHBR CELLS FROM NEURAL TISSUE

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

ALDHbr multipotent neuroprogenitors cells are present in the developing rat embryonic neural tube [45], fetal mouse brain [46], and both subventricular and subcortical zones of adult mouse brain [47]. These cells form neurospheres that can be propagated and also driven to form neurons, astrocytes, and glia in culture. When adult brain neural progenitor cells (NPC) were sorted into subpopulations based on prominin-1, Lewis X, and high ALDH activity, only ALDHbr cells demonstrated the ability to form neurospheres and retained multipotency in vitro [47]. Thus, ALDH activity identifies functional neuroprogenitor subpopulations within broader populations defined by surface antigens.

ALDHbr cells were cultured under conditions that promoted formation of motor neurons and transplanted i.t. into mouse models of spinal motor atrophy [48, 49]. Both transplanted neurons and uncultured ALDHbr cells migrated to ventral horns and established functional neuromuscular junctions. Transplantation significantly ameliorated all aspects of disease progression and extended life, but did not rescue the animals. Although migration of transplanted cells was observed and motor neurons arose from the transplanted cells, the protective effects of cell transplantation were attributed to production of angiogenic and neuroprotective cytokines by the cells. Cells derived from the ALDHbr cells strongly expressed such cytokines. Uncultured, freshly isolated ALDHbr cells also improved the disease progression and secreted several of protective cytokines, although not as much as the cultured cells. Corti et al. [49] suggested that isolating ALDHbr cells and culturing them in the absence of the inhibitory effects of spinal cord glial cells promotes the development of cells that can produce neuroprotective cytokines. This recalls the effect of enriching ALDHbr cells on efficacy of human bone marrow in the hind limb ischemia model discussed above.

ALDHBR CELLS FROM OTHER TISSUES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

Skeletal Muscle Progenitors

ALDHbr populations derived from biopsies [50] or primary explants [51] of human skeletal muscle are enriched in myoblast progenitors. ALDHbr cells from biopsies contained CD34+ and CD34− cells, and none of the cells initially expressed the myoblast marker CD56. ALDHbrCD34+ cells had some characteristics of mesenchymal stem cells (MSCs) and gave rise in culture to a heterogeneous population of CD56− cells. The ALDHbrCD34− fraction developed in vitro as a highly enriched population of CD56+ myoblasts that formed myotubes and showed strong myogenic potential on i.m. transplantation [50]. When explant cultures were driven to differentiate, only ALDHbr cells gave rise to myoblasts. Differentiated ALDHbr myoblasts survived treatment with H2O2 and DEAB, transplantation, and engrafts skeletal muscle better than ALDHlow populations [51]. This result is consistent with the idea that high ALDH activity allows ALDHbr populations to survive oxidative stress encountered in tissue repair contexts. Finally, when immunoselected CD56+ cells from the differentiated cultures were analyzed, no differences were found in the myogenic potential of ALDHbr and ALDHlo cells in vitro [50]. This result is consistent with observations on MSCs [52, 53] and endothelial cells [54] showing that ALDH expression is sometimes uncoupled from functional activity when differentiated cells are propagated in culture.

Mammary Epithelium

ALDHbr cells from human breast reduction samples include cells that formed mammospheres at 20-fold higher frequency than unsorted cells and had 10-fold higher clonogenicity. The cells were multipotential, giving rise to uncommitted, myoepithelial, luminal epithelial and mixed colonies, and ducts, when transplanted into mammary fat pads. The ALDHdim population gave rise only to luminal epithelial cells [9]. In contrast to these results with human cells, ALDHbr cells isolated from bovine mammary epithelium gave rise to cells with luminal phenotype in culture, while ALDHlow cells were myoepithelial progenitors [55].

Pancreatic Cells

Rovira et al. [15] used Aldefluor to sort the ALDHbr population of central acinar/terminal duct cells from peripheral acinar duct units of adult mice. These cells expressed early embryonic pancreas markers and formed spherical pancreatospheres. These spheres accumulated secretory products and retained some ALDHbr cells, although ALDH activity was extinguished in most cells. The derived endocrine cells showed glucose regulated insulin secretion. Spheres could be serially propagated. On transplantation into mouse embryos, ALDHbr cells, but not dim cells, contributed to both exocrine and endocrine lineages in the developing pancreas. In a repair model of pancreatitis, ALDHbr cells expanded in structures derived from acinar cells.

Prostate Epithelium

Mouse prostate cells contain an ALDHbr population that gives rise to functional basal and luminal duct tissue and neuroendocrine cells when transplanted under the renal capsule with feeder cells. Unlike ALDHlow cells, the ALDHbr cells express basal epithelial and characteristic prostate progenitor cell markers and proliferated robustly [56].

Corneal Limbic Cells

ALDHbr and ALDHlow cell populations derived from cadaveric human limbic tissue differ in clonogenicity and expression of putative limbic progenitor cell markers. However, in this case, limbic progenitor cell activity was enriched in the ALDHlow cells [57]. Several ALDH isoforms are expressed highly in the cornea where ALDH activity protects the cornea from oxidative damage [7]. Thus, high ALDH is a characteristic of differentiated corneal cells.

CONCLUSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References

ALDHbr cell populations enriched in stem cell activity have been sorted from several normal tissues using the Aldefluor method. Identifying the specific ALDH isozymes that oxidize Aldefluor in each ALDHbr population will help clarify the physiological functions of ALDH in these cells. ALDHbr cells reconstitute hematopoiesis and effect tissue repair in animal models. Clinical monitoring of graft ALDHbr cell content and circulating ALDHbr cell levels in patients suggests that ALDHbr cells play important roles in hematopoietic transplantation and in ischemic cardiovascular disease. ALDHbr cells have been manufactured from unrelated donor CB and from autologous bone marrow, and have been administered to patients in early clinical trials. Additional uses for ALDHbr cells in cell therapy may emerge from the preclinical models reviewed above.

Several issues concerning the potential clinical use of regenerative therapies based on ALDHbr cells remain to be addressed. Most significantly, one ALDHbr cell product is manufactured for one patient, a characteristic shared with other therapies based on banked unrelated CB, unmanipulated autologous bone marrow, autologous apheresis products, and autologous induced pluripotential cell products, among others. In principle, manufacture and delivery of these lot-of-one products pose more complex logistic problems than off-the-shelf allogeneic products made by processes that yield doses for many patients form a single production run. Manufacturing a clinical ALDHbr cell product, which takes about half-a-day with current sorting technologies, is at an intermediate level of complexity when compared with unmanipulated banked CB and bone marrow products, which require minimal processing before delivery, and expanded CB and bone marrow products or induced pluripotential cells, which require cultivation. Gene therapy approaches add to complexity. Scaling ALDHbr cell manufacture, like scaling of cell therapies requiring cell culture or manipulation, will be challenging.

Whether cell sorting from an adult tissue sample can yield a therapeutically effective dose of ALDHbr cells remains unknown. In preclinical models and early clinical trials, enriched ALDHbr cells have been administered in numbers one or two orders of magnitude lower than most other cell therapies. This reflects the rarity of these cells, the size of the cord or the bone marrow samples from which the ALDHbr cell products have been manufactured, and efficiency of manufacturing. As noted above, preclinical data suggests that enriching ALDHbr cells increases their potency in tissue repair when compared with unsorted tissue cell preparations. How the potency of unexpanded ALDHbr cells that have not been exposed to cytokines in culture will compare with other therapies based on expanded cells is unknown. Another technical issue that will influence the efficacy of ALDHbr and all other cell products is the route of delivery. Interactions among dose, potency, and delivery will vary for different clinical indications. These questions will only be answered as ALDHbr cell products and other candidate cell therapies move from initial safety trials into more advanced clinical trials focused on efficacy in specific clinical indications.

References

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. HOW ARE ALDHBR CELLS DEFINED, AND WHAT IS THE SIGNIFICANCE OF HIGH ALDH ACTIVITY IN CELLS?
  5. ALDHBR CELLS FROM SOURCES OF HEMATOPOIETIC GRAFT IN TRANSPLANTATION AND TISSUE REPAIR
  6. ALDHBR CELL FROM HUMAN CB AND BONE MARROW IN REPAIR OF ISCHEMIC INJURY
  7. OTHER TISSUE REPAIR MODELS INVOLVING HUMAN CB ALDHBR CELLS
  8. ALDHBR CELLS FROM NEURAL TISSUE
  9. ALDHBR CELLS FROM OTHER TISSUES
  10. CONCLUSION
  11. Disclosure of Potential Conflicts of Interest
  12. References
  • 1
    Jones RJ, Barber JP, Vala MS et al. Assessment of aldehyde dehydrogenase in viable cells. Blood 1995; 85: 27422746.
  • 2
    Storms RW, Trujillo AP, Springer JB et al. Isolation of primitive human hematopoietic progenitors on the basis of aldehyde dehydrogenase activity. Proc Natl Acad Sci USA 1999; 96: 91189123.
  • 3
    D'Angelo RC, Wicha MS. Stem cells in normal development and cancer. Prog Mol Biol Transl Sci 2010; 95: 113158.
  • 4
    Alison MR, Guppy NJ, Lim SM et al. Finding cancer stem cells: Are aldehyde dehydrogenases fit for purpose? J Pathol 2010; 222: 335344.
  • 5
    Ma I, Allan AL. The role of human aldehyde dehydrogenase in normal and cancer stem cells. Stem Cell Rev 2010 (in press). Doi: 10.1007/s12015–010-9208–4.
  • 6
    Moreb JS. Aldehyde dehydrogenase as a marker for stem cells. Curr Stem Cell Res Ther 2008; 3: 237246.
  • 7
    Marchitti SA, Brocker C, Stagos D et al. Non-P450 aldehyde oxidizing enzymes: The aldehyde dehydrogenase superfamily. Expert Opin Drug Metab Toxicol 2008; 4: 697720.
  • 8
    Kastan MB, Schlaffer E, Russo JE et al. Direct demonstration of elevated aldehyde dehydrogenase in humanhematopoietic progenitor cells. Blood 1990; 74: 19451950.
  • 9
    Ginestier C, Hur MH, Charafe-Jauffret E et al. ALDH1 is a marker of normal and malignant human mammary stem cells and a predictor of poor clinical outcome. Cell Stem Cell 2007; 1: 555567.
  • 10
    Marcato P, Dean C, Pan D et al. Aldehyde dehydrogenase activity of breast cancer stem cells is primarily due to isoform ALDH1A3 and its expression is predictive of metastasis. Stem Cells 2011; 29: 3245.
  • 11
    Chute JP, Muramoto GG, Whitesides J et al. Inhibition of aldehyde dehydrogenase and retinoid signaling induces the expansion of human hematopoietic stem cells. Proc Natl Acad Sci USA 2006; 103: 1170711712.
  • 12
    Muramoto GG, Russell JL, Safi R et al. Inhibition of aldehyde dehydrogenase expands hematopoietic stem cells with radioprotective capacity. Stem Cells 2010; 28: 523534.
  • 13
    Dolle P. Developmental expression of retinoic acid receptors (RARs). Nucl Recept Signal 2009; 7: e006.
  • 14
    Mark M, Ghyselinck NB, Chambon P. Function of retinoic acid receptors during embryonic development. Nucl Recept Signal 2009; 7: e002.
  • 15
    Rovira M, Scott SG, Liss AS et al. Isolation and characterization of centroacinar/terminal ductal progenitor cells in adult mouse pancreas. Proc Natl Acad Sci USA 2010; 107: 7580.
  • 16
    Levi BP, Yilmaz OH, Duester G et al. Aldehyde dehydrogenase 1a1 is dispensable for stem cell function in the mouse hematopoietic and nervous systems. Blood 2009; 113: 16701680.
  • 17
    Ma AC, Chung MI, Liang R et al. A DEAB-sensitive aldehyde dehydrogenase regulates hematopoietic stem and progenitor cells development during primitive hematopoiesis in zebrafish embryos. Leukemia 2010; 24: 20902099.
  • 18
    Mohyeldin A, Garzon-Muvdi T, Quinones-Hinojosa A. Oxygen in stem cell biology: A critical component of the stem cell niche. Cell Stem Cell 2010; 7: 150161.
  • 19
    Hess DA, Meyerrose TE, Wirthlin L et al. Functional characterization of highly purified human hematopoietic repopulating cells isolated according to aldehyde dehydrogenase activity. Blood 2004; 104: 16481655.
  • 20
    Storms RW, Green PD, Safford KM et al. Distinct hematopoietic progenitor compartments are delineated by the expression of aldehyde dehydrogenase and CD34. Blood 2005; 106: 95102.
  • 21
    Hess DA, Wirthlin L, Craft TP et al. Selection based on CD133 and high aldehyde dehydrogenase activity isolates long-term reconstituting human hematopoietic stem cells. Blood 2006; 107: 21622169.
  • 22
    Pearce DJ, Bonnet D. The combined use of Hoechst efflux ability and aldehyde dehydrogenase activity to identify murine and human hematopoietic stem cells. Exp Hematol 2007; 35: 14371446.
  • 23
    Christ O, Lucke K, Imren S et al. Improved purification of hematopoietic stem cells based on their elevated aldehyde dehydrogenase activity. Haematologica 2007; 92: 11651172.
  • 24
    Liu C, Chen BJ, Deoliveira D et al. Progenitor cell dose determines the pace and completeness of engraftment in a xenograft model for cord blood transplantation. Blood 2010; 116: 55185527.
  • 25
    Gentry T, Foster S, Winstead L et al. Simultaneous isolation of human BM hematopoietic, endothelial and mesenchymal progenitor cells by flow sorting based on aldehyde dehydrogenase activity: Implications for cell therapy. Cytotherapy 2007; 9: 259274.
  • 26
    Capoccia BJ, Robson DL, Levac KD et al. Revascularization of ischemic limbs after transplantation of human bone marrow cells with high aldehyde dehydrogenase activity. Blood 2009; 113: 53405351.
  • 27
    Mirabelli P, Di NR, Lo PC et al. Extended flow cytometry characterization of normal bone marrow progenitor cells by simultaneous detection of aldehyde dehydrogenase and early hematopoietic antigens: Implication for erythroid differentiation studies. BMC Physiol 2008; 8: 13.
  • 28
    Fallon P, Gentry T, Balber AE et al. Mobilized peripheral blood SSCloALDHbr cells have the phenotypic and functional properties of primitive haematopoietic cells and their number correlates with engraftment following autologous transplantation. Br J Haematol 2003; 122: 99108.
  • 29
    Gunduz E, Demirel G, Bal C et al. Evaluation of mobilized peripheral stem cells according to CD34 and aldehyde dehydrogenase expression and effect of SSC(lo) ALDH(br) cells on hematopoietic recovery. Cytotherapy 2010; 12: 10061012.
  • 30
    Taubert I, Saffrich R, Zepeda-Moreno A et al. Characterization of hematopoietic stem cell subsets from patients with multiple myeloma after mobilization with plerixafor. Cytotherapy. 2010 (in press). Doi: 10.3109/14653249.2010.530652.
  • 31
    Lioznov M, Dellbrugger C, Sputtek A et al. Transportation and cryopreservation may impair haematopoietic stem cell function and engraftment of allogeneic PBSCs, but not BM. Bone Marrow Transplant 2008; 42: 121128.
  • 32
    Page KM, Gentry T, Shoulars K et al. Use of aldehyde dehydrogenase content to predict dominating cord in double cord blood transplant. Biol Bone Marrow Transplant 2010; 16: 2155.
  • 33
    Shoulars K, Gentry T, Page KM et al. Creation of a segment-based aldehyde dehydrogenase assay as a biomarker for cord blood potency. Biol Bone Marrow Transplant 2010; 16: 263.
  • 34
    Kurtzberg J, Mendizabal A, Reese M et al. Augmentation of standard umbilical cord blood transplantation with ALDHbr cells: Results of a phase I study in pediatric patients. Biol Bone Marrow Transplant 2008; 14: 105.
  • 35
    Povsic TJ, Zavodni KL, Vainorius E et al. Common endothelial progenitor cell assays identify discrete endothelial progenitor cell populations. Am Heart J 2009; 157: 335344.
  • 36
    Povsic TJ, Zavodni KL, Kelly FL et al. Circulating progenitor cells can be reliably identified on the basis of aldehyde dehydrogenase activity. J Am Coll Cardiol 2007; 50: 22432248.
  • 37
    Sondergaard CS, Hess DA, Maxwell DJ et al. Human cord blood progenitors with high aldehyde dehydrogenase activity improve vascular density in a model of acute myocardial infarction. J Transl Med 2010; 8: 2437.
  • 38
    Smith L, White H, Gentry T et al. Human ALDH-bright bone marrow cells produce paracrine factors that protect endothelial cells from hypoxic and nutritional stress. Blood 2009; 114: 3056.
  • 39
    Povsic TJ, Zhou J, Adams SD et al. Aging is not associated with bone marrow-resident progenitor cell depletion. J Gerontol A Biol Sci Med Sci 2010; 65: 10421050.
  • 40
    Dimmeler S, Leri A. Aging and disease as modifiers of efficacy of cell therapy. Circ Res 2008; 102: 13191330.
  • 41
    Perin EC, Silva G, Gahremanpour A et al. A randomized, controlled study of autologous therapy with bone marrow-derived aldehyde dehydrogenase bright cells in patients with critical limb ischemia. Catheter Cardiovasc Interv 2011 (in press).
  • 42
    Perin EC, Silva GV, Zheng Y et al. First in man transendocardial injection of autologous aldehyde dehydrogenase bright cells in hear failure patients (FOCUS-Bright). Circulation 2009; 120: S812.
  • 43
    Hess DA, Craft TP, Wirthlin L et al. Widespread nonhematopoietic tissue distribution by transplanted human progenitor cells with high aldehyde dehydrogenase activity. Stem Cells 2008; 26: 611620.
  • 44
    Zhou P, Hohm S, Olusanya Y et al. Human progenitor cells with high aldehyde dehydrogenase activity efficiently engraft into damaged liver in a novel model. Hepatology 2009; 49: 19922000.
  • 45
    Cai J, Cheng A, Luo Y et al. Membrane properties of rat embryonic multipotent neural stem cells. J Neurochem 2004; 88: 212226.
  • 46
    Corti S, Locatelli F, Papadimitriou D et al. Identification of a primitive brain-derived neural stem cell population based on aldehyde dehydrogenase activity. Stem Cells 2006; 24: 975985.
  • 47
    Obermair FJ, Fiorelli R, Schroeter A et al. A novel classification of quiescent and transit amplifying adult neural stem cells by surface and metabolic markers permits a defined simultaneous isolation. Stem Cell Res 2010; 5: 131143.
  • 48
    Corti S, Locatelli F, Papadimitriou D et al. Transplanted ALDHhiSSClo neural stem cells generate motor neurons and delay disease progression of nmd mice, an animal model of SMARD1. Hum Mol Genet 2006; 15: 167187.
  • 49
    Corti S, Nizzardo M, Nardini M et al. Neural stem cell transplantation can ameliorate the phenotype of a mouse model of spinal muscular atrophy. J Clin Invest 2008; 118: 33163330.
  • 50
    Vauchez K, Marolleau JP, Schmid M et al. Aldehyde dehydrogenase activity identifies a population of human skeletal muscle cells with high myogenic capacities. Mol Ther 2009; 17: 19481958.
  • 51
    Jean E, Laoudj-Chenivesse D, Notarnicola C et al. Aldehyde dehydrogenase activity promotes survival of human muscle precursor cells. J Cell Mol Med 2011; 15: 119133.
  • 52
    Nagano M, Kimura K, Yamashita T et al. Hypoxia responsive mesenchymal stem cells derived from human umbilical cord blood are effective for bone repair. Stem Cells Dev 2010; 19: 11951210.
  • 53
    Estes BT, Wu AW, Storms RW et al. Extended passaging, but not aldehyde dehydrogenase activity, increases the chondrogenic potential of human adipose-derived adult stem cells. J Cell Physiol 2006; 209: 987995.
  • 54
    Nagano M, Yamashita T, Hamada H et al. Identification of functional endothelial progenitor cells suitable for the treatment of ischemic tissue using human umbilical cord blood. Blood 2007; 110: 151160.
  • 55
    Martignani E, Eirew P, Accornero P et al. Human milk protein production in xenografts of genetically engineered bovine mammary epithelial stem cells. PLoS One 2010; 5: e13372.
  • 56
    Burger PE, Gupta R, Xiong X et al. High aldehyde dehydrogenase activity: A novel functional marker of murine prostate stem/progenitor cells. Stem Cells 2009; 27: 22202228.
  • 57
    Ahmad S, Kolli S, Li DQ et al. A putative role for RHAMM/HMMR as a negative marker of stem cell-containing population of human limbal epithelial cells. Stem Cells 2008; 26: 16091619.