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M I Collector

Publications and source records attributed to M I Collector.

16 recordsLinked to original sources
PubMed2001

Multi-organ, multi-lineage engraftment by a single bone marrow-derived stem cell.

Purification of rare hematopoietic stem cell(s) (HSC) to homogeneity is required to study their self-renewal, differentiation, phenotype, and homing. Long-term repopulation (LTR) of irradiated hosts and serial transplantation to secondary hosts represent the gold standard for demonstrating self-renewal and differentiation, the defining properties of HSC. We show that rare cells that home to bone marrow can LTR primary and secondary recipients. During the homing, CD34 and SCA-1 expression increases uniquely on cells that home to marrow. These adult bone marrow cells have tremendous differentiative capacity as they can also differentiate into epithelial cells of the liver, lung, GI tract, and skin. This finding may contribute to clinical treatment of genetic disease or tissue repair.

Animals↗
PubMed2001

Phenotype and function of hematopoietic stem cells.

Using an in vivo selection technique, we can isolate individual cells that can repopulate the hematopoietic system of a lethally irradiated murine recipient. These cells rapidly acquire a CD34 phenotype in the animal. Progenitors in our long-term chimeras are of donor type. We also have evidence that transplantation of limiting numbers (as low as a single cell) that have this long-term repopulating ability (LTRA) can self-renew. This is demonstrated by serial transplantation of marrow from engrafted recipients 11 months post transplant into new hosts for four additional months.

Animals↗
PubMed1999

Homing of long-term and short-term engrafting cells in vivo.

Long-term repopulating hematopoietic stem cells can be separated from cells which provided radioprotection (short-term repopulating cells) on the basis of size. This might be a result of the quiescent nature of long-term repopulating cells. To define the activity of these populations we utilized a dye, PKH26, which incorporates into the membrane of cells and is equally distributed to daughter cells when they divide. We were able to retrieve PKH26(+)-labeled cells posttransplant in the hematopoietic tissues of the recipients. We could also assess their cell cycle status and their ability, short- and long-term, to reconstitute secondary lethally irradiated hosts in limiting dilution. The results suggest that long-term repopulating cells remain quiescent in the bone marrow shortly after engraftment, whereas cells which radioprotect are more rapidly dividing. We could not detect labeled cells in the peripheral blood posttransplant, and even though cells homed to both the spleen and bone marrow the cells in the bone marrow were significantly more competent at reconstituting lethally irradiated secondary hosts.

Animals↗
PubMed1999

Hematopoietic stem cell tracking in vivo: a comparison of short-term and long-term repopulating cells.

We have previously demonstrated that we could separate long-term repopulating stem cells from cells that provided radioprotection (short-term repopulating cells) on the basis of size and suggested that this might be due to the quiescent nature of long-term repopulating cells. To further define the activity of these populations, we used a dye (PKH26), which incorporates into the membrane of cells and is equally distributed to daughter cells when they divide. We developed an assay, which allowed us to retrieve PKH26(+) long-term and short-term repopulating cells in the hematopoietic tissues of the recipients posttransplant. We were able to recover the labeled cells and determine their cell cycle activity, as well as their ability to reconstitute secondary lethally irradiated hosts in limiting dilution. The results of our assay suggest that long-term repopulating cells are quiescent in the bone marrow (BM) 48 hours after transplant. We were able to detect only a few labeled cells in the peripheral blood posttransplant and even though cells homed to both the spleen and BM, more long-term repopulating cells homed to the marrow and only these cells, which homed to the marrow, were capable of reconstituting lethally irradiated secondary hosts long-term.

Animals↗
PubMed1997

Distinct patterns of inactivation of p15INK4B and p16INK4A characterize the major types of hematological malignancies.

Inactivation of the cyclin-dependent kinase inhibitors p16INK4A and p15INK4B are frequent alterations in neoplasia, often resulting from homozygous deletion or promoter region hypermethylation. We have analyzed both modes of inactivation of p15INK4B and p16INK4A in the major types of adult and pediatric hematological malignancies. Hypermethylation of p15INK4B, without alteration of p16INK4A, was an almost universal finding in adult acute myelogenous leukemia, and occurred very frequently in adult acute lymphocytic leukemia and pediatric acute myelogenous leukemia and acute lymphocytic leukemia. In contrast, neither p15INK4B nor p16INK4A were inactivated in any stage of chronic myelogenous leukemia. Hypermethylation of p16INK4A, often without alterations of p15INK4B, was found in non-Hodgkin's lymphoma and was much more frequent in cases with high-grade than low-grade histology. Enriched normal bone marrow stem cells had no detectable promoter region methylation of these genes, as analyzed by a newly developed PCR method. Remarkably distinct patterns of inactivation of p15INK4B and p16INK4A characterize different types of hematological malignancy, and alterations in these tumor suppressor genes are one of the most common alterations in hematological malignancies.

Adult↗
PubMed1997

Phenotypic and functional characterization of the hematopoietic stem cell.

The purpose of this report is to demonstrate the phenotypic and functional characteristics of a primitive hematopoietic stem cell (HSC). We present evidence that an isolated murine HSC can repopulate the hematopoietic tissues of lethally irradiated recipient animals long term. By limiting dilution, as few as ten isolated stem cells can reconstitute mice for their lifetime. The stem cell which we have isolated does not copurify with colony forming unit-spleen or radioprotect recipients from lethal radiation. The phenotypic characterization of this rare cell, which represents 0.005% of total bone marrow, includes either the absence or very low expression of markers associated with long-term repopulating cells described by other groups. We believe this stem cell represents a very early self-renewing stem cell in the mouse.

Animals↗
PubMed1996

Characterization of mouse lymphohematopoietic stem cells lacking spleen colony-forming activity.

The classical definition of lymphohematopoietic stem cells (LHSC), the most primitive progenitors of all blood cells, requires that they have the capacity for self-renewal and for the long-term production of all blood cell lineages. However, other characteristics of LHSC have been debated. Our previous data suggested that mouse LHSC are very slowly proliferating cells that generate delayed multilineage engraftment, while "radioprotection" (rapid engraftment that will prevent early death from radiation-induced marrow aplasia) results from more committed progenitors. Alternatively, some groups have reported that mouse LHSC are responsible for both radioprotection and long-term repopulation of all blood cell lineages. A possible explanation for this difference is that cells with the capacity for long-term production of all blood cell lineages are biologically heterogeneous. We now show that 10 LHSC can generate all blood cell lineages for the lifetime of the animal. However, these cells lacked radioprotection and spleen colony-forming activity. LHSC were identified and isolated by their small size, their lack of expression of antigens characteristic of mature blood cell lineages, and their high expression of aldehyde dehydrogenase. In addition, these cells were found to express undetectable or low levels of many antigens presumed to mark LHSC, including Thy-1, Ly-6A/E (Sca-1), c-kit, and CD34. There appears to be at least two classes of LHSC with the capacity for long-term production of all blood cell lineages: one that generates both radioprotection and long-term engraftment and one that produces delayed but durable engraftment. Our data suggest that this latter class may represent a very primitive class of LHSC.

Aldehyde Dehydrogenase↗
PubMed1996

The estrogen receptor CpG island is methylated in most hematopoietic neoplasms.

Estrogen appears to be a negative regulator of normal hematopoiesis. Chromosome 6q, which contains the estrogen receptor (ER) gene, is frequently altered in human hematopoietic neoplasms. The ER gene, which has growth and metastasis suppressor activity in many different cell types, is inactivated by promoter methylation in some ER-negative breast tumors and 100% of colorectal tumors. We now report that the promoter region of the ER gene is aberrantly methylated in 86% of human hematopoietic tumors, including 8 of 9 pediatric acute lymphocytic leukemia, 17 of 18 adult acute lymphocytic leukemia, 21 of 23 adult acute myelogenous leukemia, 3 of 6 chronic phase chronic myelogenous leukemia, 9 of 9 blast crisis chronic myelogenous leukemia and 5 of 8 lymphomas. This methylation event was also present in all nine leukemia cell lines examined, where it was associated with very low or absent ER expression. In addition, rat and mouse leukemia cell line also exhibited this change, indicating that ER CpG island methylation in leukemias is conserved among species. Our results suggest that ER CpG island methylation could be an important step in the genesis of human hematopoietic neoplasms and might be a useful molecular marker for monitoring the clinical status of these diseases.

Adult↗
PubMed1996

Selective radiosensitization of p53-deficient cells by caffeine-mediated activation of p34cdc2 kinase.

The induction of tumor cell death by anticancer therapy results from a genetic program of autonomous cell death termed apoptosis. Because the p53 tumor suppressor gene is a critical component for induction of apoptosis in response to DNA damage, its inactivation in cancers may be responsible for their resistance to genotoxic anticancer agents. The cellular response to DNA damage involves a cell-cycle arrest at both the G1/S and G2/M transitions; these checkpoints maintain viability by preventing the replication or segregation of damaged DNA. The arrest at the G1 checkpoint is mediated by p53-dependent induction of p21WAF1/CIP1, whereas the G2 arrest involves inactivation of p34cdc2 kinase. Following DNA damage, p53-deficient cells fail to arrest at G1 and accumulate at the G2/M transition. We demonstrate that abrogation of G2 arrest by caffeine-mediated activation of p34cdc2 kinase results in the selective sensitization of p53-deficient primary and tumor cells to irradiation-induced apoptosis. These data suggest that pharmacologic activation of p34cdc2 kinase may be a useful therapeutic strategy for circumventing the resistance of p53-deficient cancers to genotoxic anticancer agents.

Animals↗
PubMed1995

Assessment of aldehyde dehydrogenase in viable cells.

Cytosolic aldehyde dehydrogenase (ALDH), an enzyme responsible for oxidizing intracellular aldehydes, has an important role in ethanol, vitamin A, and cyclophosphamide metabolism. High expression of this enzyme in primitive stem cells from multiple tissues, including bone marrow and intestine, appears to be an important mechanism by which these cells are resistant to cyclophosphamide. However, although hematopoietic stem cells (HSC) express high levels of cytosolic ALDH, isolating viable HSC by their ALDH expression has not been possible because ALDH is an intracellular protein. We found that a fluorescent aldehyde, dansyl aminoacetaldehyde (DAAA), could be used in flow cytometry experiments to isolate viable mouse and human cells based on their ALDH content. The level of dansyl fluorescence exhibited by cells after incubation with DAAA paralleled cytosolic ALDH levels determined by Western blotting and the sensitivity of the cells to cyclophosphamide. Moreover, DAAA appeared to be a more sensitive means of assessing cytosolic ALDH levels than Western blotting. Bone marrow progenitors treated with DAAA proliferated normally. Furthermore, marrow cells expressing high levels of dansyl fluorescence after incubation with DAAA were enriched for hematopoietic progenitors. The ability to isolate viable cells that express high levels of cytosolic ALDH could be an important component of methodology for identifying and purifying HSC and for studying cyclophosphamide-resistant tumor cell populations.

Aldehyde Dehydrogenase↗
PubMed1994

Characterization of murine CD34, a marker for hematopoietic progenitor and stem cells.

CD34 is expressed on human hematopoietic stem and progenitor cells, and its clinical usefulness for the purification of stem cells has been well established. However, a similar pattern of expression for murine CD34 (mCD34) has not yet been determined. Two polyclonal anti-mCD34 antibodies that specifically recognize both endogenous and recombinant murine CD34 were developed to characterize the mCD34 protein and to determine its pattern of expression on murine cell lines and hematopoietic progenitor cells. Fluorescence-activated cell sorter analysis showed that mCD34 is expressed on NIH/3T3 embryonic fibroblasts, PA6 stromal cells, embryonic stem cells, M1 leukemia cells, and a subpopulation of normal bone marrow cells. Murine CD34 was found to be a glycoprotein expressed on the cell surface as either a full-length (approximately 100 kD) or truncated (approximately 90 kD) protein in NIH/3T3 and PA6 cells. Recombinant full-length CD34, when expressed in the CHO-K1 cell line, had a molecular weight of approximately 105 kD. Full-length CD34 expressed on M1 leukemia cells, had a higher apparent molecular weight (110 kD). These results suggest that there are glycosylation differences between CD34 expressed by different cell types. The full-length form, but not the truncated form, is a phosphoprotein that is hyperphosphorylated in response to 12-0-Tetradecanoyl phorbol 13-acetate treatment, suggesting potential functional differences between the two forms. Selection of the 3% highest-expressing CD34+ bone marrow cells enriched for the hematopoietic precursors that form colony-forming unit-spleen (CFU-S), CFU-granulocyte-macrophage, and burst-forming unit-erythroid. Transplantation of lethally irradiated mice with these cells demonstrated both short- and long-term repopulating ability, indicating that this population contains both functional hematopoietic progenitors and the putative stem cell. These antibodies should be useful to select for murine hematopoietic stem cells.

3T3 Cells↗
PubMed1993

BCR-ABL gene rearrangement and expression of primitive hematopoietic progenitors in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by an initial chronic phase of expanded yet orderly clonal hematopoiesis that is distinguished by the BCR-ABL gene rearrangement. We found that although the mature myeloid compartment in patients with CML was expanded and entirely derived from the dominant leukemic clone, the primitive hematopoietic progenitor compartment did not show a corresponding expansion and was substantially enriched for cells without the BCR-ABL gene rearrangement. More importantly, primitive progenitors exhibiting the BCR-ABL gene rearrangement did not express either the BCR-ABL hybrid mRNA or fusion protein (P210). Expression of P210 protein and BCR-ABL mRNA increased with myeloid commitment in vivo as well as with growth factor-induced proliferation and differentiation of the primitive CML progenitors in vitro. This differential expression of BCR-ABL between primitive and mature CML progenitors may explain the expansion of the leukemic clone at the level of mature myeloid progenitors and granulocytes without a concomitant expansion of primitive CML progenitors. Because BCR-ABL mRNA is minimally expressed or may be absent in primitive CML progenitors, these cells may escape detection by reverse transcriptase-polymerase chain reaction and eradication by antisense oligonucleotides targeted against BCR-ABL mRNA.

Base Sequence↗
PubMed1986

Thymic regulation of hematopoiesis. III: Isolation of helper and suppressor populations using counterflow centrifugal elutriation.

We have evidence that thymic regulatory cells can either enhance or inhibit the growth of hematopoietic progenitors in vitro. We have suggested that two separate populations are responsible for this regulatory interaction but isolation of the cell types has proven difficult. We now report the isolation by counterflow centrifugal elutriation (CCE) of two separate populations of thymocytes which regulate erythropoiesis in coculture. We demonstrate that a minority population (less than 10%) of slow sedimenting elutriated thymocytes provide a helper function whereas the suppressor population is the majority population. Furthermore, some thymocytes of intermediate cell volume neither enhance nor inhibit erythroid colony growth. We conclude that isolation of thymic subsets can lead to identification of populations which induce cell-cell regulation of hematopoietic progenitors resulting in both a positive and negative feedback control of growth.

Animals↗
PubMed1983

Regulation of hematopoiesis II: the role of polyamine inhibition on helper or suppressor influences of the thymus.

We have previously suggested in murine model systems, that two cell subpopulations with differing proliferative capacity, from the thymus, modify the growth of erythroid progenitor cells in vitro. In order to further characterize these populations, we have specifically inhibited polyamine biosynthesis; this pathway is essential for the process of cell replication. Thus, alpha-difluoromethyl ornithine (DFMO) was used to block the conversion of ornithine to putrescine, the first and rate-limiting step in polyamine biosynthesis. We observed a threefold increase in hematopoietic progenitors (CFU-S and CFU-E) from bone marrow in animals treated with DFMO. We further examined the effect of DFMO on accessory "helper" and "suppressor" cells from the thymus and observed an increase in helper activity with an elimination of suppressor activity. All of these effects of DFMO were specific for inhibition of polyamine biosynthesis, since simultaneous addition of the depleted biosynthetic product, putrescine, restored suppressor activity. We conclude that polyamine biosynthesis is required acutely for accessory cell regulation of hematopoiesis.

Animals↗
PubMed1977

Stress-induced modulation of the immune response.

After mice were exposed to a daily auditory stressor for varying lengths of time, the responses of their splenic lymphoid cells in vitro were assessed. Both the blastogenic activity of concanavalin A or lipopolysaccharide and the ability of immune lymphocytes to lyse P815 target cells showed the same patterns of immunosuppression and enhancement.

Animals↗