AN APPROACH TO THE CHARACTERIZATION OF STEM CELLS IN MOUSE BONE MARROW

Hydrogen sulphide increases hepatic differentiation of human tooth pulp stem cells compared with human bone marrow stem cells

AIM

To determine the differences in stem cell properties, in hepatic differentiation and in the effects of hydrogen sulphide (H2 S) on hepatic differentiation between human bone marrow stem cells (hBMC) and stem cells from human exfoliated primary tooth pulp (SHED).

METHODOLOGY

CD117(+) cells were magnetically separated and subjected to hepatic differentiation. CD117(+) cell lineages were characterized for transcription factors indicative of stem cells by qRT-PCR. For the last 9 days of the differentiation, the test cells were exposed to 0.1 ng mL(-1) H2 S. Immunocytochemistry and flow cytometry of albumin, alpha-fetoprotein and carbamoyl phosphate synthetase were carried out after differentiation. Urea concentration and glycogen synthesis were also determined.

RESULTS

Genes expressed in SHED were also expressed in BMC. No difference in expression level of hepatic markers was shown by immunofluorescence. SHED showed more positive cells than hBMC (P < 0.01). H2 S increased the number of positive cells in both cultures (P < 0.01). Urea concentration and glycogen synthesis increased significantly after H2 S exposure (P < 0.001 and P < 0.05, respectively). Real-time PCR data were analysed by RT(2) profiler RT-PCR Array Data Analysis version 3.5 (Qiagen), and ELISA data were analysed by Bonferroni's multiple comparison using Windows spss version 16 (SPSS Inc, Chicago, IL, USA). Bonferroni's multiple comparison test was also carried out after angle transformation for the percentage data of flow cytometer using Windows spss(®) version 16 (SPSS Inc). Statistical significance was accepted at P < 0.05.

CONCLUSIONS

Stem cells from human exfoliated primary tooth pulp and BMC have similar properties. The level of hepatic differentiation in SHED compared with BMC was the same or higher. H2 S increased the level of hepatic differentiation.

Stimulatory effect of intermittent feeding on hemopoietic recovery in sublethally gamma-irradiated mice

The effect of three-week adaptation to intermittent feeding on the recovery of the hemopoietic functions of mice after sublethal gamma irradiation was investigated. Measurement of oxygen consumption, carbon dioxide output and the respiratory quotient demonstrated an increased metabolic rate in the intermittently fed animals and an accentuation of lipogenic processes. This metabolic state persisted even after irradiation. An improvement in the recovery of hemopoietic functions after irradiation was demonstrated in adapted animals, which was reflected by the increased proliferative activity of the hemopoietic cell populations (more intensive incorporation of 125I-UdR into the DNA of cells of the spleen, thymus and femoral bone marrow), by more rapid renewal of spleen weight, more rapid recovery of the femoral bone marrow cellularity and increased levels of granulocytes in peripheral blood.

Transformation of hemopoietic stem cells by phytohemagglutinin (PHA) II. Mechanism of action

It has long been known that phytohemagglutinin (PHA) stimulates transformation and growth of immune competent lymphocytes. Lymphoid cell colonies have previously been shown in the spleen with PHA treated lymph node cells from donor mice were injected into irradiated mice. This communication reports the results of in vivo effects of PHA stimulation on agar colony forming units and spleen colony forming units (CFU). C3H/Hej mice injected with 1 ml of PHA-M were found to secrete colony stimulating factors (PHA-CSF) which lead to an increase in the number of agar colony forming units (granulopoiesis). Serum obtained on day 6 after PHA injection showed enhanced granulopoiesis which was four times higher than in the controls. It was found that 1.0 ml and 0.15 ml of PHA-CSF were more effective in promoting the growth of agar colony forming units in agar plates. Intravenous injection of PHA increased the number of spleen-as well as agar colony forming units (CFU). Day 3 appeared to be optimal for in vivo effects of PHA on granulopoietic cells. An increase in the colony forming units was obtainable when previously treated bone marrow and spleen cells taken on day 3 were injected into irradiated mice. There was a fourfold increase of the colony forming units (CFUs) in the spleen and a twofold one in bone marrow cells. As compared to the controls, the increase in agar colony forming units (CFUc) of bone marrow was fourfold and that of the spleen tenfold. On day 5 some effect was still noticeable but it was lower than on day 3. On weight and cell count basis it was found that on day 6 PHA had a significant in vivo effect on the spleen. On the basis of our findings it can be concluded that PHA supports the survival of transplanted stem cells by stimulating their differentiation into unipotent erythroid progenitor cells. It may also be concluded that PHA activates the immune competent stem cells (mostly T lymphocytes) and displays a supporting function for a better stem cell survival and differentiation into the erythroid progenitor cells. The activated lymphocytes secrete a colony-stimulating like factor which stimulates granulopoiesis and also helps in the differentiation of the stem cells.

Comparison of cell proliferation in the regenerating bone marrow and spleen of irradiated mice with the use of 125I-iododeoxyuridine

The method of 125IUdR labelling of hemopoietic cell populations was used to estimate differences of repopulation kinetics in the femoral bone marrow and spleen of sublethally irradiated mice. In regenerating bone marrow the cellularity and proliferation index, as measured by 6 h 125IUdR incorporation, were found to be inversely related. In the spleen the proliferation index increased parallelly with the increase in cellularity and indicates an ineffectiveness of a change in the set point of local cellularity control. Experiments with measuring the retention of 125IUdR in hemopoietic organs revealed, in the spleen of irradiated animals, phases of increased cell losses as well as immigration of labelled cells into this organ.

Effect of estrogen on natural killer cells

Treatment of mice with sustained high levels of betarestradiol leads to a reduction in natural killer cell activity and genetic resistance to bone marrow transplantation. The loss of natural killing does not seem to result from either humoral or immune suppression. Natural killer cells are thought to depend on the bone marrow, and it is notable that estrogens reduce natural killing at approximately the same time that they produce a loss of ma-row due to osteoproliferation. Similarly, mice with congenital osteopetrosis are deficient in natural killing. However, changes in natural killing during and after treatment with estrogen do not correspond directly to changes in marrow volume. Estrogens are known to exacerbate spontaneous autoimmunity in NZB/NZW mice. The relationship between this effect and the effect of estrogen on natural killing is not clear. When natural killing is lowered in NZB/NZW mice by the in vivo administration of 89Sr, autoimmunity is reduced.

Proliferative capacity of erythropoietic stem cell lines and aging: an overview

The earliest bone marrow precursor cell types, often called stem CELLS, have a very large capacity for self renewal. This makes them a useful model system in which to test the hypothesis that normal somatic cells have a limited proliferative capacity. Marrow precursor cells differentiate and multiply to replenish the supply of various blood cell types that constantly turn over. Especially with erythrocyte production, this function is well difined and can be tested rigorously to determine whether a significant amount of the stem cell proliferative capacity is exhausted. Functional tests generally show that marrow stem cell lines are exhausted after three to six serial transplantations into successive recipients; the few exceptions are cases in which functioning by cells from the irradiated recipients has not been ruled out. Genetic markers unambiguously identifying marrow stem cell lines from the original donor are necessary for clear cut interpretations of transplantation experiments. No significant differences are found when comparing erythrocyte production by marrow stem cell lines from old and young adult donors. This suggests that little or none of the erythropoietic stem cell's proliferative capacity is exhausted by a lifespan of normal functioning.

Biphasic pattern of thymus regeneration after whole-body irradiation

Whole-body irradiation of mice with 300 or 400 R causes a precipitous fall in thymus weight, followed by an increase in the mitotic index and an almost complete restoration of thymus mass. This phase is followed by a secondary fall in thymus weight and gradual recovery. This secondary fall can be prevented by intravenous injection of bone marrow or shielding of the hind limbs during irradiation. The hypothesis is proposed that the thymus depends on the migration of cells from the bone marrow to the thymus for the maintenance of its cell population. Bone marrow cells with chromosome markers injected intravenously into normal or lightly irradiated (150 R) animals do not populate the host bone marrow to any significant degree. After whole-body irradiation with heavy doses (400 R), donor cells dominate the marrow. There may be a competition between dividing cells in the bone marrow which regulates proliferation of hemic cells. Bone marrow cells with marker chromosomes do not repopulate the thymus in irradiated animals until long after repopulating the bone marrow. It is possible that these cells have to pass through the marrow or the blood-marrow barrier to acquire characteristics needed for entering the thymus. After whole-body irradiation with 500 R or more, the first phase of regeneration of the thymus, represented by an increase in the mitotic index, does not occur to a significant degree. Apparently cells in the thymus capable of proliferation have been largely eliminated, and restoration of organ mass depends chiefly on seeding from other sources, probably the bone marrow. After whole-body irradiation with 200 R, only the first phase of thymus weight loss and regeneration takes place. Probably bone marrow injury is too small to interfere with the supply of cells repopulating the thymus.

The effect of heterologous anti-lymphocyte seerum on mouse hemopoietic stem cells

The present study has demonstrated that rabbit anti-mouse lymphocyte serum (RAMLS) has the capability of destroying bone marrow cells and suppressing hemopoietic stem cell function. The in vitro incubation of bone marrow suspensions with RAMLS caused extensive cell lysis with an apparent preferential destruction of lymphoid, erythroid, and blastoid elements. Using the spleen colony assay, the number of functional hemopoietic stem cells was found to be markedly reduced in bone marrow populations exposed to RAMLS in vitro. Further, this loss of stem cell function could be produced by exposing marrow suspensions to small concentrations of antiserum which did not produce detectable cytotoxic effects on the general marrow population. A similar effect of RAMLS upon hemopoietic stem cells was found in vivo. The intravenous injection of RAMLS into lethally irradiated mice immediately after the infusion of isogeneic marrow cells reduced the number of spleen colonies formed, indicating that the antiserum could exhibit a deleterious effect upon stem cells in the bloodstream of the intact animal. Normal animals treated with daily subcutaneous injections of RAMLS for 3 wk had a significantly reduced marrow content of functional hemopoietic stem cells, suggesting that RAMLS can affect stem cells located in situ in the bone marrow. The experiments indicate that RAMLS possesses potential marrow toxicity.

Factors influencing hematopoietic spleen colony formation in irradiated mice. I. The normal pattern of endogenous colony formation

Data pertaining to the endogenous mouse spleen colony system, 10 days postirradiation, are presented. The D(o) for visible colonies is 78 R, while that for 6 hr iron uptake over a range of 600-800 R is 50 R. The D(o) for spleen weight is 196 R and that for IUdR uptake is 193 R. These measurements increase with the age of the mouse. Hypertransfusion decreases spleen iron uptake and colony number. DF-(32)P and sodium sulfate-(35)S are not useful indicators of splenic hematopoiesis in this system. Visible hematopoietic colonies in the spleen are not produced by vinblastine, nitrogen mustard, methotrexate, or cyclophosphamide.

Hemopoietic spleen colony studies. IV. Phytohemagglutinin and hemopoietic regeneration

The effects of phytohemagglutinin (PHA) were studied in irradiated mice to see if a definite myeloproliferative effect could be demonstrated in vivo. The data obtained suggested the following conclusions. PHA treatment of the bone marrow donor only, causes a consistent but slight reduction in transplantable spleen colony-forming unit (CFU) content of the bone marrow 24 hr after the last PHA injection, but no change was found in the proportion of the various colony types. PHA treatment of the irradiated recipient of normal bone marrow causes no change in the number of spleen colonies. However, 8-day colonies are only about half normal size, are much more likely to be of mixed cell types, contain many large undifferentiated blastoid cells, but fewer transplantable CFU. The spleen sinusoids are packed with hemopoietic cells. Spleen colonies developing in hosts receiving daily injections of PHA show, in addition to the usual spectrum of cell types, a high proportion of unusual blastoid cells resembling the PHA transformed peripheral lymphocytes seen in vitro. The function of these cells is not known, but they may represent augmented proliferation and/or transformation of stem cells. PHA administered after irradiation significantly increased the number of endogenous spleen colonies, and, at certain doses of irradiation, improved postirradiation survival. PHA administered before irradiation had no effect on the number of endogenous spleen colonies formed, or on postirradiation survival. On the basis of these and other data, possible modes of action of PHA are discussed.