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PubMed1979

Effects of 226Ra and X-irradiation on the proliferative and differentiative ability of mouse hemopoietic stem cells.

The ability of hemopoietic stem cells to repopulate spleens of heavily irradiated syngeneic hosts in form of macroscopically visible clonal colonies of differentiating cells was studied in mice exposed for 32 and 4 weeks to internally deposited 226Ra (0.56 and 0.46 muCi per mouse respectively) or to 100 rad X-irradiation. Exocolonizing test and cytological techniques were used for quantitative evaluation. The size of stem cell compartment was reduced and the function of the surviving stem cells was altered by radium and X-ray irradiation. The proliferation and maintenance of hemopoietic cell populations were found to depend not only on the numbers of stem cells but also on their multiplicative and differentiative capability.

Animals↗

PubMed1978

Successive stimulation of major cell groups in bone marrow. A preliminary approach to the problem of stem cell competition.

The existence of pluripotential haemopoietic stem cells raises the possibility of stem cell competition when two or more differentiating stimuli are given either simultaneously or in close succession. The experiments now reported deal with the effects on guinea pig bone marrow of successive stimulation and they fall into two groups. In one group, erythropoiesis was first stimulated by means of hypoxia, after which granulopoiesis was stimulated by the intraperitoneal injection of typhoid vaccine. In another group, these two stimuli were given in the reverse order. Bone marrow changes were evaluated both quantitatively and by differential counts. The experimental animals were compared with controls given only one stimulus, either hypoxia or vaccine, and also with normal untreated animals. As judged by the output of granulocytes or erythrocytes, no stem cell shortage developed in the experimental animals. A marked fall in transitional cells in the bone marrow of the experimental animals is consistent with the view, though not affording actual proof, that the pluripotential stem cells are to be found in the transitional cell compartment.

Animals↗

PubMed1976

Osteopetrosis of microphthalmic mice -- a defect of the hematopoietic stem cell.?

The recessive genes mi and gl in the homozygous state determine, among other phenotypic effects, osteopetrosis in the house mouse. From a stock carrying mi derived from Grüneberg (1963) the mi gene was bred into the standard CBA/H inbred strain. Microphthalmic mice of these two stocks and their hybrids were treated as newborn by intraperitoneal injection and at weaning or maturity by intravenous injection of cell suspensions containing hematopoietic stem cells from phenotypically normal mice. Resolution of much of the osteopetrosis but not the other phenotypic effects occurred within a few months in the majority of cases, provided syngeneic or H-2 compatible allogeneic cells were given: it did not occur spontaneously or on giving H-2 incompatible cells or on giving compatible material by an inappropriate route. The results accord with hypotheses that (1) osteoclasis of scaffoldtype woven bone is impaired in mi mi, (2) that osteoclastic cells are derived through circulating monocytes from hematopoietic stem cells, and (3) in mi mi this defect can be overcome by a transplant of normal hemopoietic stem cells.

Age Factors↗

PubMed1979

A murine teratocarcinoma stem cell line carries suppressed oncogenic virus genomes.

Murine teratocarcinoma stem cells are nonpermissive for productive infection by a variety of DNA (polyoma and SV40 virus) and RNA (murine leukemia and sarcoma virus) tumor viruses whereas differentiated murine cells derived from the stem cells are permissive for productive (or abortive in the case of SV40) infection by these same viruses. The block to productive infection by these oncogenic viruses is at a postpenetration step in the replication cycle of these viruses but the precise level of the block has not been established for any of these viruses. In this report we describe teratocarcinoma-derived stem and differentiated cell lines which should be especially useful in determining the level of the block to replication of ecotropic murine leukemia virus in murine teratocarcinoma stem cells. The stem cell line, OTT6050AF1 BrdU, which is completely nonpermissive to productive infection by Moloney murine leukemia virus and consists of 97% pluripotent stem cells, contains DNA copies of an RNA tumor virus which is indistinguishable from the N-tropic murine leukemia virus of AKR mice. The stem cells are negative for expression of viral reverse transcriptase, p30 and gp69/71 and no virus is found by XC plaque assay or other biological tests. Differentiated cells established from the same teratocarcinoma tumor are 100% positive for viral gp69/71, p30, and produce large amounts of reverse transcriptase activity and N-tropic virus as detected by biological assay. The virus isolated from the differentiated cells is closely related, if not identical to AKR N-tropic virus by nucleic acid hybridization studies and is thus not an endogenous virus of the 129 strain of mice. The teratocarcinoma tumor from which the cell lines were established had been carried in 129 mice and perhaps at some time in the mouse passage history the tumors were infected (nonproductively) with the N-tropic virus. Regardless of the origin of this viral DNA, the OTT6050A derived stem and differentiated cell lines should be extremely useful in defining in stem cells the step at which ecotropic murine leukemia virus replication is blocked.

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PubMed1979

Stem cell growth and differentiation in Hydra attenuata. I. Regulation of the self-renewal probability in multiclone aggregates.

Interstitial stem cells in Hydra are rapidly proliferating multipotent stem cells which continuously give rise to precursors for nerve and nematocyte differentiation. Growth of the stem cell population is controlled by the cell cycle time of the stem cells and the self-renewal probability, Ps (the fraction of stem cells in each generation which divide to yield more stem cells). In normal Hydra the stem cell generation time is 24 h and Ps = 0.6; under these conditions the stem cell population doubles in 3.5 days. In the present experiments we have systematically investigated the dependence of Ps on stem cell density. We culture stem cells in a feeder layer system consisting of aggregates of nitrogen-mustard (NM)-inactivated Hydra cells. In this system stem cell density can be varied over a wide range by changing the number of clone-forming units (CFU) added to the aggregates. We have measured the growth rate of the stem cell population and the cell cycle of stem cells in NM aggregates after 4--7 days of culture. From these data we calculate the value of Ps. The results indicate that the growth rate decreases 4-fold as the number of CFU seeded per aggregate increases from 10 to 400. Under these same conditions the cell cycle remains constant. The values of Ps calculated from these results indicate the Ps decreases from 0.75 in aggregates seeded with 10--30 CFU to 0.55 in aggregates seeded with 200--400 CFU. These results support a model in which Ps is controlled by negative feedback from neighbouring stem cells. In addition, our experiments indicate that Ps decreases during the growth of stem cell clones. When only a few stem cells are seeded in aggregates, they give rise to isolated clones distributed throughout the aggregate. Ps decreases markedly within such clones as they grow in size presumably due to increasing stem cell content of the clones. Since Ps in such isolated clones declines with growth, we infer that the local stem cell concentration is what controls Ps and that the spatial range of the negative feedback signal is short compared to the dimensions of NM aggregates.

Animals↗

PubMed1975

Effects of bleomycin on mouse bone-marrow stem cells.

The mouse hematopoietic stem-cell population was tested by the spleen colony technique for effects of the antineoplastic agent bleomycin (BLM). The time response of normal bone marrow was investigated by a single dose of BLM (400 mg/kg) between 0 and 72 hours. The dose response was studied over a wide range of doses (from 40 to 1,600 mg/kg) at a 4-hour exposure. Additional experiments concerned 1) the fraction of colony-forming units in the S phase after BLM administration (by means of pulse hydroxyurea treatment), 2) the response of bone marrow stimulated by endotoxin, and 3) the effects of split-dose treatments. The relatively low toxicity of BLM on both the differentiated and stem-cell populations of unstimulated bone marrow was confirmed and detailed. This drug exhibited peculiar, proliferation-dependent cell inactivation kinetics. Furthermore, BLM induced parasynchronous behavior in the unstimulated stem-cell population. The various aspects of BLM action are discussed with regard to its use in cancer chemotherapy.

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PubMed1979

Immunoregulation of localized and disseminated murine myeloma: antigen-specific regulation of MOPC-315 stem cell proliferation and secretory cell differentiation.

Tumor development, MOPC-315 stem cells, and M315-secretory cells were quantitated in carrier-primed BALB/c mice that had been challenged subcutaneously or i.v. with mixtures of TNP-carrier and TNP-binding MOPC-315 cells. We observed that tumor incidence, myeloma stem cells, and secretory myeloma cells were: i) suppressed in mice in whom carrier-specific suppressor T cells had previously been induced and ii) initially ehnahced in mice with carrier-specific helper T cells. The early enhancement in mice with carrier-specific helper T cells was followed by progressively declining myeloma stem cell frequencies and regression of established tumors. These studies demonstrate that T cell-derived immunoregulators of host origin can be focused onto localized and disseminated malignant B cells and specifically regulate the expansion and differentiation of the neoplastic clone.

Animals↗

PubMed2026

Manipulation of protein translation and stem cell self-renewal by CRISPR activation of rRNA transcription.

Ribosomal RNA (rRNA) transcription rates vary during development, and their dysregulation is linked to diseases such as cancer and ribosomopathies. Owing to their high abundance and genomic redundancy, the functional significance of rRNA levels remains unclear. We developed TAPIR (Targeted Activation of Protein Translation), a CRISPR-based approach to elevate rRNA levels by inducing 47S ribosomal DNA transcription. TAPIR increased nucleolar size and enhanced protein synthesis, even in rapidly proliferating cells. In neural stem cells, elevated translation promoted self-renewal and proliferation in vitro and in vivo. Furthermore, TAPIR enabled the modeling and partial rescue of associated disease phenotypes. Our findings reveal that rRNA levels directly regulate translational output and that protein synthesis capacity can act as a key determinant of mammalian stem cell behavior.

Animals↗

PubMed1978

Stimulating factors and cell recruitment in murine bone marrow stem cells and EMT6 tumours.

The role of a stimulating factor in cell recruitment and the kinetics of its secretion were investigated by in vivo and in vitro techniques. The association of these two methods made it possible to demonstrate that a non-cycling population liberates a factor which in turn stimulates quiescent bone marrow stem cells into DNA synthesis. Moreover, it seems that undamaged cells are capable of secreting this factor. A stimulating factor responsible for cell recruitment was also demonstrated in an experimental EMT6 tumour and the kinetics of its secretion reported.

Animals↗

PubMed1976

In vivo distinction between a target cell for Friend virus (FVP) and murine hematopoietic stem cells.

Busulphan (BU) treatment of DBA/2 mice with hypertransfusion (HT)-induced polycythemia resulted in an ablation of detectable hematopoietic stem cells (CFUS) in pooled marrow from the long bones. Daily injections of erythropoietin (EP) stimulated an EP-responsive population of cells in the absence of detectable CFUS. Mice treated with BU and EP and having HT-induced polycythemia were inoculated with the polycythemia-inducing strain of Friend virus (FVP) and determinations were made for the presence of tumor colony-forming units (tCFU). No change in CFUS/10(6) bone marrow cells was detected as a result of EP treatment. However, tCFU were increased more than 100-fold in HT-BU-EP-treated mice compared with saline-treated controls. The demonstration of tCFU in mice in which CFUS were not detectable indicated that this leukemogenic effect of FVP could occur in the absence of the pluripotent stem cell. Furthermore, the increased numbers of this FVP target cell in the EP-stimulated, BU-treated mice with HT-induced polycythemia supported the model licating the target for this effect in the EP-responsive cell population.

Animals↗

PubMed1977

The identification in adult bone marrow of pluripotent and restricted stem cells of the myeloid and lymphoid systems.

The precise relationship between the stem cells for the lymphoid system and those for the blood-forming system is unclear. While it is generally assumed that the hemopoietic stem cell, the spleen colony-forming unit (CFU-S), is also the stem cell for the lymphoid system, there is little evidence for this hypothesis. To investigate the stem cells in these two systems, we irradiated bone marrow cells to induce unique chromosome aberrations in the stem cell population and injected them at limiting dilution into stem cell-deficient recipients. Several months (between 3 and 11) were allowed for the injected cells to repopulate the hemopoietic system. At that time, the bone marrow, spleen, and thymus were examined for a high frequency of cells having the same unique chromosome aberration. The presence of such markers shows that the marker was induced in a cell with extensive proliferative capacity, i.e., a stem cell. In addition, the splenic lymphocytes were stimulated with phytohemagglutinin (PHA) or lipopolysaccharide (LPS) to search for unique chromosomes in dividing T and B cells, respectively. Finally, bone marrow cells were injected into secondary irradiated recipients to determine if the marker occurred in CFU-S and to determine whether or not the same tissue distributions of marked cells could be propogated by bone marrow cells in a second recipient. After examination of 28 primary recipients, it was possible to identify three unique patterns of stem cell regeneration. In one set of mice, a unique chromosome marker was observed in CFU-S and in PHA- and LPS-stimulated cultures. These mice provide direct evidence for a pluripotent stem cell in bone marrow. In addition, two restricted stem cells were identified by this analysis. In three recipients, abnormal karyotypes were found only in myeloid cells and not in B and T lymphocytes. These mice presumably received a marked stem cell restricted to differentiate only into myeloid progeny. In three other recipients, chromosome aberrations were found only in PHA-stimulated cells; CFU-S and cells from LPS cultures did not have cells with the unique chromosome. This pattern suggests that bone marrow contains cells committed to differentiation only into T lymphocytes. For each of the three types of stem cells, secondary recipients had the same cellular distribution of marked cells as the primary recipients. This observation provides further evidence that unique markers can be induced in both pluripotent and restricted stem cells.

Age Factors↗

PubMed1976

[Effect of thymus cells on the radiosensitivity and differentiation trends of hematopoietic stem cells].

A stimulating influence of thymus cells on the capability of irradiated (from 100 to 500 r) bone marrow of mice of producing colonies in spleen of syngenous recipient has been proven. The intensification of colony formation involves an increased radioresistance of stem cells. It is supposed that radioresistant thymus cells have a stimulating effect. Thymus cells exert their influence not only to the rate of survival of stem cells proliferating in the bone marrow of femur, but also increase their erythropoetic potention.

Animals↗

PubMedDate not supplied

Kinetics and biochemical properties of haemopoietic stem cells during chicken development.

Haemopoietic stem cells from donors of different ages (embryos, adults) have been grafted into irradiated hosts. Cell multiplication kinetics, foetal haemoglobin production, age-specific antigen production were examined during two weeks after grafting. The results obtained tend to show that the erythrocyte characteristics are, for a large part, already determined in a stem cell type endowed with a large proliferative capacity.

Age Factors↗

PubMed2026

Age-associated chromatin repression of Hippo-Yap signaling drives oogonial stem cell decline in chicken.

Oogonial stem cells (OSCs) are a type of reproductive germline stem cell present in the ovaries of adult animals after birth. They have been proposed to contribute to follicle renewal and could be associated with reproductive longevity, yet the molecular mechanism contribute to OSC malfunction during aging in chicken remain unclear. Here, we show that OSC number and proliferative capacity decline significantly from pre-laying to late-laying stages, accompanied by increased follicular atresia. RNA-seq analysis revealed a global reduction in transcriptional activity in aged OSCs. ChIP-seq demonstrated elevated H3K27me3 deposition, particularly at promoter regions, which correlated with repression of proliferation-related genes in the Hippo pathway including YAP1 and TEAD1. Pharmacological inhibition of H3K27me3 reduced repressive chromatin marks, restored Hippo pathway gene expression, and significantly enhanced OSC proliferation. Conversely, YAP1 knockdown attenuated proliferation-associated gene expression. These findings indicate that age-dependent H3K27me3 accumulation suppresses OSC proliferation through epigenetic repression of the Hippo-YAP axis, providing mechanistic insight into ovarian aging and a potential strategy to extend the laying cycle in poultry.

Animals↗

PubMed2025

BCLAF1 restrains stress responses in hematopoietic stem cells to support expansion and repopulation.

Hematopoietic stem cells (HSCs) rapidly expand during fetal development and after stress. Here, we identify B-cell lymphoma-2-associated factor 1 (BCLAF1) as a regulator of HSC repopulation activity, with roles in the expansion of fetal HSCs and hematopoietic reconstitution after stem cell transplantation. Using mice with hematopoietic-specific and inducible deletion of Bclaf1, we find that BCLAF1 promotes fetal HSC development but is dispensable for the maintenance of adult HSCs at steady state. Loss of BCLAF1 in either fetal or adult HSCs significantly impairs their self-renewal and multilineage reconstitution activity after stem cell transplantation. Single-cell RNA sequencing of fetal hematopoietic progenitors reveals that loss of BCLAF1 reduces long-term HSCs and restrains the expression of stress response genes. BCLAF1 associates with chromatin throughout the genome of fetal and adult hematopoietic cells, likely through indirect mechanisms, to regulate transcriptional programs. These results establish a novel function for the transcriptional regulator BCLAF1 in limiting stress responses in HSCs, thereby preserving HSC development during embryogenesis and repopulation function after stem cell transplant.

Hematopoietic Stem Cells↗

PubMed2024

Bone-marrow-homing lipid nanoparticles for genome editing in diseased and malignant haematopoietic stem cells.

Therapeutic genome editing of haematopoietic stem cells (HSCs) would provide long-lasting treatments for multiple diseases. However, the in vivo delivery of genetic medicines to HSCs remains challenging, especially in diseased and malignant settings. Here we report on a series of bone-marrow-homing lipid nanoparticles that deliver mRNA to a broad group of at least 14 unique cell types in the bone marrow, including healthy and diseased HSCs, leukaemic stem cells, B cells, T cells, macrophages and leukaemia cells. CRISPR/Cas and base editing is achieved in a mouse model expressing human sickle cell disease phenotypes for potential foetal haemoglobin reactivation and conversion from sickle to non-sickle alleles. Bone-marrow-homing lipid nanoparticles were also able to achieve Cre-recombinase-mediated genetic deletion in bone-marrow-engrafted leukaemic stem cells and leukaemia cells. We show evidence that diverse cell types in the bone marrow niche can be edited using bone-marrow-homing lipid nanoparticles.

Animals↗

PubMed1976

Properties and development of erythropoietic stem cells in the chick embryo.

1. When injected into irradiated chickens, haemopoietic stem cells give rise to well-defined erythrocytic colonies in the host marrow. Such stem cells (CFU-M = Colony Forming Unit in Marrow) have been found in different tissue of the chicke embryo (yolk sac, blood, marrow). Analysis of the properties of CFU-M reveals that they represent two classes of stem cells: pluripotent stem cells mainly in adult marrow and erythrocytic-committed stem cells present in yolk sac. 2. Yolk sac contains the main pool of CFU-M during the major part of embryonic life. In the blood of 6-day-old embryo, there are three or four times more CFU-Ms than in the yolk sac; they are no longer detected in the blood after the 16th day of incubation. During development of the marrow, stem cells are actively differentiating and their total number remains the same from 16 days to hatching.

Age Factors↗

PubMed1977

Effect of hydroxyurea and vinblastine on the proliferation of the pluripotential stem cells.

The population of the pluripotential hemopoietic stem cells in mice, i. e. those cells forming colonies in the spleens of lethally irradiated mice (colony forming cells CFc) is proliferating relatively slowly. After a partial damage the population regenerates which is achieved by means of the increased proliferation rate. The effect of damage caused by different doses of hydroxyurea or vinblastine on the proliferation of the CFc has been investigated. CFc population was measured in femur bone marrow after grafting the sample of the bone marrow into the lethally irradiated mice recipients (spleen colony method). The proliferation rate was estimated either according to the magnitude of the fraction of cells synthesizing DNA in the S phase of the cell cycle, or according to the sensitivity of the population to the repeated injections of vinblastine. Data showed that even after very minute damage caused by hydroxyurea the stem cells started to proliferate intensively. The effect was dose dependent. The comparable damage caused by vinblastine had a significantly weaker effect on the proliferation of the stem cells. From the results it is concluded that the proliferation response of the pluripotential stem cells depends on two factors: one being the extent of the damage caused to the hemopoietic tissue and the second the position of the killed cells in the cell cycle.

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