In vitro quantitation of lethal and physiologic effects of total body irradiation on stromal and hematopoietic stem cells in continuous bone marrow cultures from Rf mice

Evolution of malignant plasmacytoma cell lines from K14E7 Fancd2-/- mouse long-term bone marrow cultures

We tested the effect of expression of the Human Papilloma Virus (HPV E7) oncogene on hematopoiesis in long-term bone marrow cultures (LTBMCs) derived from K14E7 (FVB) Fancd2-/- (129/Sv), K14E7 Fancd2+/+, Fancd2-/-, and control (FVB X 129/Sv) Fl mice. K14E7 Fancd2-/- and Fancd2-/- LTBMCs showed decreased duration of production of total nonadherent hematopoietic cells and progenitors forming day 7 and day 14 multilineage CFU-GEMM colonies in secondary cultures (7 wks and 8 wks respectively) compared to cultures from K14E7 Fancd2+/+ (17 wks) or control mice (18 wks) p < 0.0001. Marrow stromal cell lines derived from both K14E7 Fancd2-/- and Fancd2-/- cultures were radiosensitive, as were IL-3 dependent hematopoietic progenitor cell lines derived from K14E7 Fancd2-/- cultures. In contrast, Fancd2-/- mouse hematopoietic progenitor cell lines and fresh marrow were radioresistant. K14E7 Fancd2-/- mouse freshly explanted bone marrow expressed no detectable K14 or E7; however, LTBMCs produced K14 positive factor-independent (FI) clonal malignant plasmacytoma forming cell lines in which E7 was detected in the nucleus with p53 and Rb. Transfection of an E6/E7 plasmid into Fancd2-/-, but not control Fancd2+/+ IL-3 dependent hematopoietic progenitor cell lines, increased cloning efficiency, cell growth, and induced malignant cell lines. Therefore, the altered radiobiology of hematopoietic progenitor cells and malignant transformation in vitro by K14E7 expression in cells of the Fancd2-/- genotype suggests a potential role of HPV in hematopoietic malignancies in FA patients.

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the age-dependent sensitivity to radiation carcinogenesis, including the effects of in-utero exposure.

Dysregulated in vitro hematopoiesis, radiosensitivity, proliferation, and osteoblastogenesis with marrow from SAMP6 mice

The senescence accelerated-prone mouse variant 6 (SAMP6) shows normal growth followed by rapid aging, development of osteopenia, and shortened lifespan, compared with control R1 mice. Because oxidative stress is a fundamental mechanism of tissue aging, we tested whether cellular parameters that are associated with oxidative stress are impaired with marrow from SAMP6 mice. We compared in vitro hematopoiesis, irradiation sensitivity, proliferative potential, and osteoblastogenesis with marrow cells from SAMP6 and R1 mice. Marrow cells from SAMP6 mice showed shortened in vitro hematopoiesis; their stromal cells showed greater radiation sensitivity and decreased proliferation. Consistent with those properties, there was constitutive upregulation of transforming growth factor-β(1), an inhibitor of hematopoiesis, and of cell cycle inhibitory genes, p16(INK4A) and p19(ARF). Paradoxically, there was constitutive expression of osteoblast genes in stromal cells from SAMP6 mice, but in vitro matrix mineralization was impaired. These studies and data included in other reports indicate that impaired proliferation of osteoblast progenitors in SAMP6 marrow may be a major factor contributing to accelerated loss of bone mass. In sum, marrow from SAMP6 mice had diminished capacity for long-term hematopoiesis, increased radiosensitivity, and reduced proliferative capacity.

Increased longevity of hematopoiesis in continuous bone marrow cultures derived from NOS1 (nNOS, mtNOS) homozygous recombinant negative mice correlates with radioresistance of hematopoietic and marrow stromal cells

OBJECTIVE

Neuronal nitric oxide synthase (NOS1, mitochondrial NOS, neuronal NOS) homozygous deletion recombinant negative mice demonstrate ionizing irradiation resistance in vivo, attributable to the decrease in mitochondrial-localized production of peroxynitrite, a potent lipid toxic free radical species resulting from the combination of nitric oxide and superoxide. The present studies were designed to determine whether reduced mitochondrial generation of toxic radical oxygen species in NOS1-/- mice also increased the longevity of hematopoiesis in continuous bone marrow cultures and conferred radioresistance to cells in vitro.

MATERIALS AND METHODS

Long-term bone marrow cultures (LTBMCs) were established from NOS1-/- and NOS1+/+ littermate mice. Radiation resistance of hematopoietic and marrow stromal cells was measured. Cell cycle analysis and measurement of glutathione and glutathione peroxidase were carried out on irradiated clonal bone marrow stromal cell lines.

RESULTS

A significant increase in longevity of hematopoiesis was detected in NOS1-/- mouse LTBMCs for over 64 weeks in culture compared to 20 weeks for NOS1+/+ mouse LTBMCs (p < 0.001). Permanent bone marrow stromal cell lines derived from NOS1-/- mouse LTBMCs demonstrated increased radioresistance in vitro reflected by an increased shoulder on the survival curve with n = 32.15 +/- 1.21 compared to NOS1+/+ cells n = 10.47 +/- 3.2 (p = 0.0026), interleukin-3-dependent NOS1-/- hematopoietic progenitor cell lines also demonstrated decreased apoptosis after 10 Gy irradiation. Both pre- and postirradiation stabilization of the cellular antioxidant pool was detected in NOS1-/- cells. NOS1-/- cells showed a prolonged G1 cell cycle arrest after 10 Gy.

CONCLUSIONS

Prolonged hematopoiesis in LTBMCs correlates with intrinsic radioresistance of hematopoietic and marrow stromal cells from NOS1-/- mice. The data confirm the importance to hematopoiesis of mitochondrial localized nitric oxide in both radioresistance and longevity of hematopoiesis in continuous bone marrow cultures.

Hematopoietic stem cell compartment: acute and late effects of radiation therapy and chemotherapy

The bone marrow is an important dose-limiting cell renewal tissue for chemotherapy, wide-field irradiation, and autologous bone marrow transplantation. Over the past 5-10 years a great deal has been discovered about the hematopoietic stem cell compartment. Although the toxicity associated with prolonged myelosuppression continues to limit the wider use of chemotherapy and irradiation, ways are being discovered to circumvent this toxicity such as with the increasing use of cytokines. This review describes what is known of how chemotherapy and irradiation damage stem cells and the microenvironment, how cytokines protect hematopoietic cells from radiation damage and speed marrow recovery after chemotherapy or marrow transplantation, and how various types of blood marrow cells contribute to engraftment and long-term hematopoiesis after high doses of cytotoxic agents and/or total body irradiation.

Haemopoietic long-term bone marrow cultures from adult mice show osteogenic capacity in vitro on 3-dimensional collagen sponges

Adult murine bone marrow cells, cultured under conditions for long-term haemopoietic marrow cultures, produce bone matrix proteins and mineralized tissue in vitro, but only after the adherent stromal cells were loaded on a 3-dimensional collagen sponge. Provided more than 8 x 10(6) cells are loaded, mineralization as measured by 85Sr uptake from the culture medium, occurred in this 3-dimensional configuration (3-D) within 6 days. In contrast if undisrupted marrow fragments (containing more than 10(7) cells) are placed directly on a collagen sponge, then it requires more than 10 days before significant mineralization can similarly be detected. The 2-dimensional (2-D) long-term marrow culture system allows prior expansion of the stromal cells and some differentiation in an osteogenic direction within the adherent stromal layer. This is suggested by the presence of type I collagen and alkaline phosphatase positive cells. However; synthesis of osteonectin and a bone specific protein, osteocalcin, as well as calcification are only observed in 3-D cultures. Electron microscopy demonstrated hydroxyapatite mineral on collagen fibres, osteoblast-like cells, fibroblasts, cells which accumulated lipids, and macrophages which were retained on the collagen matrices. Irradiation of confluent long-term bone marrow cultures, prior to their loading on the collagen sponge showed that haemopoietic stem cells are not necessary for the mineralization.

Mechanisms towards compensation of long-term haemopoietic injury in mice after 5 Gy irradiation: in vivo and in vitro enhancement of superoxide anion production by granulocytes

This paper analyzes the long-term (6 and 12 months) function of mouse granulocytes after total body irradiation with a single dose (5 Gy) of X-rays. Superoxide anion production has been investigated in granulocytes from peripheral blood, and also in those harvested from long term bone marrow cultures, with the aim of correlating the environmental damage induced by radiation with the functional properties of granulocytes. An in vivo and in vitro enhancement of superoxide anion production and protein levels in granulocytes from irradiated mice is described. The presence of some colony stimulating factor in the supernatant of cultures from irradiated mice could play an important role in the priming of granulocytes.

Bone marrow from Balb/c mice radiocontaminated with 241Am in utero shows a deficient in vitro haemopoiesis

Radiation damage from 241Am to bone marrow cells was manifest in long-term bone marrow cultures (LTC) from offspring of mice radiocontaminated at the 14th day of gestation (119, 479, 803, 1754 kBq 241Am/kg). Offspring were reared by their own contaminated mother for 3 weeks postnatal. LTC from these offspring were less able to support in vitro CFC proliferation than control LTC from non-contaminated offspring. This radiation damage persisted 71 weeks after radiocontamination in utero. Using this in vitro culture system, damage was observed at lower doses if 241Am contamination occurred at foetal than at adult ages. Radiation damage was observed only using LTC, while the haemopoietic stem cell concentration (CFU-S, in vitro CFC) and the stromal stem cell concentration (CFU-F) from marrow in situ were not impaired after 241Am radiocontamination in utero. After culturing LTC in 25 per cent FCS and recharging the stromal adherent layer with bone marrow cell suspensions originating either from control offspring or from offspring contaminated with 241Am in utero, some evidence was found that the proliferation capacity of the haemopoietic cells was diminished. However, the nature of effects on the stromal elements is currently somewhat equivocal. Following in utero contamination the stromal adherent cells appeared to support better the production of in vitro CFC.

The radiation response and recovery of bone marrow stroma with particular reference to long-term bone marrow cultures

There is evidence for long-term haematopoietic dysfunction in some patients treated with radiotherapy. Although the underlying mechanisms are unclear, both stem cell and environmental defects have been implicated. In the present article we review the evidence concerning the role of stromal cells. According to the endpoints used, a wide range of radiosensitivities for the stroma have been reported. Long-term bone marrow cultures provide a system in which both functional and regenerative aspects of the stroma can be studied. A dose of 5 Gy applied prior to the establishment of long-term bone marrow cultures decreases both the formation of a confluent adherent stromal layer and its capacity to support haematopoiesis. In contrast, in its fully established phase, the adherent layer displays a high radioresistance due to the low proliferative stress applied to its stromal populations. A dose of 10 Gy given to a fully established adherent layer does not prevent haematopoietic engraftment and sustained haematopoiesis. At doses above 100 Gy a macrophage-like and epithelioid cell-type become dominant, which preserve their ability of producing growth regulatory molecules at doses as high as 500 Gy. These data suggest that the main effect on the stroma is a delayed expression of irradiation damage due to the slow rate of turnover of stromal cells. So far, there is little evidence for persistent deficiencies in the functional roles of stromal cell populations.

The pattern of myeloid suppression and recovery after the addition of methotrexate to murine long-term bone marrow culture

Treating long-term bone marrow culture with 10(-7)-10(-5) M methotrexate caused a 95% reduction in myelopoiesis as assessed by supernatant cell count and granulocyte/macrophage colony forming unit number. The suppression was irreversible with 10(-5) M methotrexate. Complete recovery of myeloid cell production occurred four and five weeks after cultures were treated with either 10(-7) M or 10(-6) M methotrexate, respectively. The suppression of myelopoiesis was completely prevented if 10(-3) M leucovorin was added to culture within 6 h of 10(-6) M methotrexate. The addition to culture of lung conditioned medium containing high concentrations of granulocyte/macrophage colony-stimulating factor shortened the time of myelopoietic suppression by one week. The addition of WEHI-3B medium containing both interleukin 3 and GM-CSF shortened the suppression by two weeks. This in vitro model provides unique opportunities to examine mechanisms involved in the myelopoietic and chemotherapy-induced suppression. A close analysis of approaches to modify the recovery process will also be possible.

Alteration in hematopoietic stem cell seeding and proliferation by both high and low dose rate irradiation of bone marrow stromal cells in vitro

The mechanism of physiologic alteration by high (HDR) or low dose rate (LDR) (5 or 120 cGy/min) irradiation of plateau-phase bone marrow stromal cell cultures was investigated using a technique of in vitro bone marrow transplantation. Purified stromal cell cultures from C57BL/6J, C3H/HeJ, or (C57BL/6J X DBA2/J)F1 (B6D2F1) mouse marrow were irradiated to doses of 2.5 to 10 Gy at LDR or 10-100 Gy at HDR and were then engrafted in vitro with nonadherent hematopoietic cells from murine continuous bone marrow cultures. Parameters of engraftment quantitated included: (1) numbers of adherent proliferating hematopoietic cell colonies, "cobblestone islands" (2) cumulative production of nonadherent hematopoietic cells over 8 weeks after engraftment, (3) M-CSF, GM-CSF and multi-CSF (IL-3) dependent hematopoietic progenitor cells forming greater than or equal to 50 cell colonies in semisolid medium, (4) cumulative production of CFUs, and (5) number of adherent stromal cells positive for detectable extracellular laminin or collagen type IV (markers of endothelial cells, reticular adventitial cells, or sinus lining cells). There was a decrease in cobblestone island formation between 5 and 10 Gy and this parameter possibly increased at doses of 50 and 100 Gy. There was no difference between HDR and LDR irradiation to 10 Gy. Irradiation to doses above 10 Gy decreased support of engrafted cells forming CFU-GM and CFU-GEMM. Measures of CFUs after 10 Gy were variable but indicated a possible increase with HDR and no effect of LDR at 1 week and a decrease in both HDR and LDR groups at 3 weeks after engraftment. Thus, LDR and HDR irradiation in vitro alter several specific parameters of marrow stromal cell support for engrafted hematopoietic stem cells.

Engraftment of a clonal bone marrow stromal cell line in vivo stimulates hematopoietic recovery from total body irradiation

Whether bone marrow stromal cells of donors contribute physiologically to hematopoietic stem cell reconstitution after marrow transplantation is unknown. To determine the transplantability of nonhematopoietic marrow stromal cells, stable clonal stromal cell line (GB1/6) expressing the a isoenzyme of glucose-6-phosphate isomerase (Glu6PI-a, D-glucose-6-phosphate ketol-isomerase; EC 5.3.1.9) was derived from murine long-term bone marrow cultures and made resistant to neomycin analogue G418 by retroviral gene transfer. GB1/6 cells were fibronectin+, laminin+, and collagen-type IV+ and collagen type I-; these GB1/6 cells supported in vitro growth of hematopoietic stem cells forming colony-forming units of spleen cells (CFU-S) and of granulocytes, erythrocytes, and macrophage/megakarocytes (CFU-GEMM) in the absence of detectable growth factors interleukin 3 (multi-colony-stimulating factor), granulocyte/macrophage colony-stimulating factor, granulocyte-stimulating factor, or their poly(A)+ mRNAs. The GB1/6 cells produced macrophage colony-stimulating factor constitutively. Recipient C57BL/6J (glucose-6-phosphate isomerase b) mice that received 3-Gy total-body irradiation and 13 Gy to the right hind limb were injected i.v. with GB1/6 cells. Engrafted mice demonstrated donor-originating Glu6PI-a+ stromal cells in marrow sinuses in situ 2 mo after transplantation and a significantly enhanced hematopoietic recovery compared with control irradiated nontransplanted mice. Continuous (over numerous passages) marrow cultures derived from transplanted mice demonstrated G418-resistant, Glu6PI-a+ stromal colony-forming cells and greater cumulative production of multipotential stem cells of recipient origin compared with cultures established from irradiated, nontransplanted control mice. These data are evidence for physiological function in vivo of a transplanted bone marrow stromal cell line.

Effects of low dose rate irradiation on plateau phase bone marrow stromal cells in vitro: demonstration of a new form of non-lethal, physiologic damage to support of hematopoietic stem cells

The clinical use of low dose rate (LDR) (5-25 rad/min) total body irradiation in bone marrow transplantation patients is well established. We have developed an in vitro system for study of the effects of LDR irradiation on bone marrow stromal cells. Purified mouse bone marrow stromal cell cultures in plateau phase with no detectable hematopoiesis were prepared and were then "engrafted" in vitro by addition of purified nonadherent hematopoietic cells from continuous bone marrow cultures. Hematopoietic cells were added in liquid medium or suspended in an overlay of semisolid 0.4% agar-containing medium. Other agar overlays contained Interleukin-3-dependent cloned multipotential hematopoietic stem cell line B6SUtA. In parallel experiments, a cloned permanent bone marrow stromal cell line D2XRII was used in place of purified stromal cell cultures. Stromal cultures were irradiated at 5 rad/min, 20 rad/min, or 200 rad/min, 24 hours or 3 weeks prior to "engraftment." Two classes of irradiation damage were demonstrated following 1000 rad irradiation at 200 rad/min: 1) Decreased clonagenic survival of trypsinized replated marrow stromal cells (lethal effect); and 2) decreased production by marrow stromal cells or D2XRII cells of colony stimulating factors (CSF)s for granulocyte-macrophage progenitor cells and B6SUtA cells (physiologic effect). Holding the cultures in plateau phase for 3 weeks after irradiation was associated with significantly more repair of the lethal effect compared to the physiologic effect. Cultures irradiated at 5 rad/min or 20 rad/min to doses producing significantly less lethal effect showed a complex alteration of production of growth factors. Cumulative cell production by hemopoietic stem cells added in liquid culture was comparably decreased for all three dose rates. These data demonstrate a distinct physiologic expression of irradiation damage to bone marrow stromal cells that affects cell to cell interaction, responds differently to changes in dose rate, and is repaired with kinetics different from those of the lethal effect of irradiation. The present system should prove valuable for investigation of cellular interactions in hematopoietic stem cell engraftment that are altered by total body irradiation.

Effect of donor age on long-term culture of bone marrow in vitro

Previous reports suggest that 33 degrees C is the optimum temperature for the long-term culture of murine bone marrow in vitro. We found that horse serum was an important variable determining our ability to culture marrow from immature (less than 10 weeks) mice at 37 degrees C. While some batches supported growth others did not. The ability of deficient horse serum to support growth could be corrected if the culture was fed at mid-week with additional medium. Marrow from aged mice (96 weeks and older) could invariably be cultured at 37 degrees C irrespective of the horse serum batch used for culture. Adult mice (20-24 weeks) gave intermediate results between immature and aged mice. All three groups of mice studied could be cultured at 33 degrees C irrespective of the batch of horse serum used or the age of the donor. These results indicate that horse serum provides a factor(s) which varies in concentration from batch to batch and is essential for normal marrow growth in vitro. The requirement for this factor is greater at higher temperature and in younger animals. Marrow from adult and aged mice was then simultaneously cultured at 33 degrees C and 37 degrees C. For adult mice the cell recovery at 33 degrees C was initially significantly higher than at 37 degrees C but at later times became less. As a result cumulative recovery at both temperatures was equal. Cumulative cell recovery and culture survival time was significantly less in the aged than the young mice cultures.(ABSTRACT TRUNCATED AT 250 WORDS)