Cytokine treatment or accessory cells are required to initiate engraftment of purified primitive human hematopoietic cells transplanted at limiting doses into NOD/SCID mice.
(17/9154)
Little is known about the cell types or mechanisms that underlie the engraftment process. Here, we have examined parameters affecting the engraftment of purified human Lin-CD34+CD38- normal and AML cells transplanted at limiting doses into NOD/SCID recipients. Mice transplanted with 500 to 1000 Lin-CD34+CD38- cord blood (CB) or AML cells required the co-transplantation of accessory cells (ACs) or short-term in vivo cytokine treatment for engraftment, whereas transplantation of higher doses (>5000 Lin-CD34+CD38- cells) did not show these requirements suggesting that ACs are effective for both normal and leukemic stem cell engraftment in this model. Mature Lin+CD34- and primitive Lin-CD34+CD38+ cells were capable of acting as ACs even though no repopulating cells are present. Cytokine treatment of NOD/SCID mice could partially replace the requirement for co-transplantation of AC. Furthermore, no difference was seen between the percentage of engrafted mice treated with cytokines for only the first 10 days after transplant compared to those receiving cytokines for the entire time of repopulation. Surprisingly, no engraftment was detected in mice when cytokine treatment was delayed until 10 days posttransplant. Together, these studies suggest that the engraftment process requires pluripotent stem cells plus accessory cells or cytokine treatment which act early after transplantation. The NOD/SCID xenotransplant system provides the means to further clarify the processes underlying human stem cell engraftment. (+info)
Influence of increased c-Myc expression on the growth characteristics of human melanoma.
(18/9154)
Overexpression of the proto-oncogene c-myc has been associated with neoplastic transformation in a variety of tumors. For human melanoma high c-myc expression has been found in the vertical growth phase and higher positivity reported in metastases than primary tumors. The principle aim of this study was to determine, whether c-Myc expression influences the metastatic behavior of human melanoma in the absence of lymphocyte-mediated immune phenomena. The growth characteristics and tumor biology of two c-myc transfectants of the human melanoma cell line IGR39D, expressing c-Myc 1.7 and three times over baseline and the respective vector control were analyzed both in vitro and in a severe combined immunodeficient mouse model in vivo. Both c-myc transfectants showed increased growth rates, anchorage independent growth and directed cell movement in culture. Subcutaneously implanted IGR39D melanomas highly overexpressing c-Myc spontaneously formed macroscopic metastases (lymph nodes and lung) in severe combined immunodeficient mice in all cases (n = 7 per group), whereas less prominent c-Myc overexpression caused the development of only lung micrometastases. During the time period leading to terminal disease in animals injected with c-myc transfected human melanoma cells, melanoma development was not seen in vector controls. These findings suggest that constitutive high c-Myc expression in human melanoma results in a more aggressive growth behavior both in vitro and in vivo and favors metastasis in severe combined immunodeficient mice by factors unrelated to immune phenomena such as class I human leukocyte antigen downregulation known to be associated with c-Myc expression. (+info)
Genetic control of experimental lyme arthritis in the absence of specific immunity.
(19/9154)
Host genetics play an important role in determining resistance or susceptibility to experimental Lyme arthritis. While specific immunity appears to regulate disease resolution, innate immunity appears to regulate disease severity. Intradermal infection with Borrelia burgdorferi yields severe arthritis in C3H/He (C3H) mice but only minimal arthritis in BALB/c mice. Intradermal infection of immunodeficient C3H SCID mice also results in severe arthritis, but arthritis of only moderate severity in BALB/c SCID mice. In the present study, we examined immunodeficient recombinase-activating gene-knockout (RAG-1(-/-)) (RAG-) mice from resistant C57BL/6 (B6) and DBA/2 (DBA) mouse strains. B. burgdorferi-infected B6 RAG- and DBA RAG- mice had little or no ankle swelling, a low occurrence of inflammatory infiltrates in tibiotarsal joints, and low arthritis severity scores in comparison to RAG+ and RAG- BALB/c or C3H mice. Few differences in spirochete DNA levels in ankles of resistant and susceptible RAG- mice were seen. These data suggest that resistance to arthritis development following B. burgdorferi infection is not necessarily dependent on an acquired immune response and can occur despite the presence of high spirochete burden. Thus, genes expressed outside the specific immune response can be central regulators of experimental arthritis. (+info)
T cell independence of bleomycin-induced pulmonary fibrosis.
(20/9154)
The role of T cells and cytokines in bleomycin (BLM)-induced fibrosis was evaluated in susceptible and resistant strains of normal and SCID mice. Histology and hydroxyproline analysis showed that BLM induced pulmonary fibrosis in C57BL/6 and (C57BL/6 x BALB/c)F1 mice, whereas BALB/c mice were resistant to the disease. To test whether lymphocytes were required for the induction of BLM-induced pulmonary fibrosis, SCID mice were injected intratracheally with BLM and evaluated for the development of pulmonary inflammation and fibrosis. Similar morphological changes and increases in hydroxyproline were observed in both C57BL/6 SCID and (C57BL/6 x CB.17)F1 SCID animals compared to those seen in wild-type C57BL/6 and (C57BL/6 x BALB/c)F1 mice. In contrast, CB.17 SCID mice, which are genetically similar to BALB/c mice, were resistant to disease induction. Analysis of the cellular infiltrate in BLM-treated C57Bl/6 SCID mice confirmed a lack of T cells in the lungs of SCID mice and demonstrated a pronounced accumulation of eosinophils in areas of developing pulmonary fibrosis. NK cells were significantly elevated in untreated SCID mice and did not increase further after BLM treatment. Analysis of selected cytokines 1 day after initiation of BLM-induced pulmonary fibrosis indicated that the levels of TNF-alpha and IFN-gamma appeared to segregate with fibrosis in both the SCID and wild-type mice. The data demonstrate that T cells are not required for the induction of fibrosis by BLM and suggest that responses by non-lymphoid cells may be sufficient for the induction of fibrosis. (+info)
Energy intake and prostate tumor growth, angiogenesis, and vascular endothelial growth factor expression.
(21/9154)
BACKGROUND: A sedentary lifestyle coupled with excessive energy intake is speculated to be a factor associated with increased incidence of prostate cancer. We have investigated the effects of energy intake on prostate tumor growth in experimental animals. METHODS: Two transplantable prostate tumor models, i.e., the androgen-dependent Dunning R3327-H adenocarcinoma in rats and the androgen-sensitive LNCaP human carcinoma in severe combined immunodeficient mice, were studied. R3327-H tumor growth and relevant tumor biomarkers (proliferation index, apoptosis [programmed cell death], microvessel density, and vascular endothelial growth factor [VEGF] expression) were compared in ad libitum fed control rats, ad libitum fed castrated rats, and groups restricted in energy intake by 20% or 40%. A second set of experiments involving both tumor models examined tumor growth in ad libitum fed rats or in animals whose energy intake was restricted by 30% using three different methods, i.e., total diet restriction, carbohydrate restriction, or lipid restriction. All P values are two-sided. RESULTS: R3327-H tumors were smaller in energy-restricted or castrated rats than in control rats (P<.001). Tumors from energy-restricted rats exhibited changes in tumor architecture characterized by increased stroma and more homogeneous and smaller glands. In castrated rats, the tumor proliferation index was reduced (P<.0001), whereas apoptosis was increased in both energy-restricted (P<.001) and castrated (P<.001) rats. Tumor microvessel density and VEGF expression were reduced by energy restriction and castration (P<.003 versus control). Restriction of energy intake by reduction of carbohydrate intake, lipid intake, or total diet produced a similar inhibition of growth of R3327-H or LNCaP tumors. These effects were associated with reduced circulating insulin-like growth factor-I. CONCLUSIONS: Our observations are consistent with the hypothesis that energy restriction reduces prostate tumor growth by inhibiting tumor angiogenesis. Furthermore, dietary fat concentration does not influence prostate tumor growth when energy intake is reduced. (+info)
Gene transfer of cytokine inhibitors into human synovial fibroblasts in the SCID mouse model.
(22/9154)
OBJECTIVE: To investigate the effects of retrovirus-based gene delivery of inhibitory cytokines and cytokine inhibitors into human synovial fibroblasts in the SCID mouse model of rheumatoid arthritis (RA). METHODS: The MFG vector was used for gene delivery of tumor necrosis factor alpha receptor (TNFalphaR) p55, viral interleukin-10 (IL-10), and murine IL-10 into RA synovial fibroblasts. The effect on invasion of these cells into human articular cartilage and on perichondrocytic cartilage degradation was examined after 60 days of coimplantation into the SCID mouse. RESULTS: TNFalphaR p55 gene transfer showed only a limited effect on inhibition of RA synovial fibroblast invasiveness and cartilage degradation. In contrast, invasion of the RA synovial fibroblasts into the coimplanted cartilage was strongly inhibited by both viral and murine IL-10. Perichondrocytic cartilage degradation was not affected by either form of IL-10. CONCLUSION: The data show that cytokines can be successfully inserted into the genome of human RA synovial fibroblasts using a retroviral vector delivery system, and that the SCID mouse model of human RA is a valuable tool for examining the effects of gene transfer. In addition, inhibition of more than one cytokine pathway may be required to inhibit both synovial- and chondrocyte-mediated cartilage destruction in RA. (+info)
One-day ex vivo culture allows effective gene transfer into human nonobese diabetic/severe combined immune-deficient repopulating cells using high-titer vesicular stomatitis virus G protein pseudotyped retrovirus.
(23/9154)
Retrovirus-mediated gene transfer into long-lived human pluripotent hematopoietic stem cells (HSCs) is a widely sought but elusive goal. A major problem is the quiescent nature of most HSCs, with the perceived requirement for ex vivo prestimulation in cytokines to induce stem cell cycling and allow stable gene integration. However, ex vivo culture may impair stem cell function, and could explain the disappointing clinical results in many current gene transfer trials. To address this possibility, we examined the ex vivo survival of nonobese diabetic/severe combined immune-deficient (NOD/SCID) repopulating cells (SRCs) over 3 days. After 1 day of culture, the SRC number and proliferation declined twofold, and was further reduced by day 3; self-renewal was only detectable in noncultured cells. To determine if the period of ex vivo culture could be shortened, we used a vesicular stomatitis virus G protein (VSV-G) pseudotyped retrovirus vector that was concentrated to high titer. The results showed that gene transfer rates were similar without or with 48 hours prestimulation. Thus, the use of high-titer VSV-G pseudotyped retrovirus may minimize the loss of HSCs during culture, because efficient gene transfer can be obtained without the need for extended ex vivo culture. (+info)
Normal development in porcine thymus grafts and specific tolerance of human T cells to porcine donor MHC.
(24/9154)
The induction of T cell tolerance is likely to play an essential role in successful xenotransplantation in humans. In this study, we show that porcine thymus grafts in immunodeficient mice support normal development of polyclonal, functional human T cells. These T cells were specifically tolerant to MHC Ags of the porcine thymus donor and responded to nondonor porcine xenoantigens and alloantigens. Exogenous IL-2 did not abolish tolerance, suggesting central clonal deletion rather than anergy as the likely tolerance mechanism. Our study suggests that the thymic transplantation approach to achieving tolerance with restoration of immunocompetence may be applicable to xenotransplantation of pig tissues to humans. (+info)