G-CSF-mobilized peripheral blood mononuclear cells added to marrow facilitates engraftment in nonmyeloablated canine recipients: CD3 cells are required

Stable mixed donor/host hematopoietic chimerism can be uniformly established in dogs conditioned with 200 cGy TBI before dog leukocyte antigen (DLA)-identical marrow transplantation and immunosuppressed with a short course of mycophenolate mofetil (MMF) and cyclosporine (CSP) after the transplantation. A further decrease in the TBI dose to 100 cGy or the elimination of MMF in this model results in graft rejection. Here we asked whetherthe addition of G-CSF-mobilized peripheral blood mononuclear cells (G-PBMC) to marrow grafts would enhance donor engraftment in dogs conditioned with 100 cGy TBI and given postgrafting immunosuppression with CSP alone. Using this model, 7 of 9 dogs given only marrow cells rejected their grafts within 8 to 17 weeks after transplantation. In contrast, the addition of unmodified G-PBMC to marrow grafts resulted in stable mixed donor/host chimerism in 5 of 8 dogs studied (P = .06). However, addition of the CD3-depleted fraction of G-PBMC, which contained both CD34 cells and CD14 cells, resulted in engraftment in only 1 of 7 recipients. We conclude that adding G-PBMC to marrow grafts replaced the requirement of MMF and 100 cGy of TBI, and that CD3 cells were required to facilitate engraftment of marrow cells in DLA-identical recipients, whereas the additional CD34 cells present in G-PBMC were not sufficient for this effect.

Comparison of gene expression in CD34+ cells from bone marrow and G-CSF-mobilized peripheral blood by high-density oligonucleotide array analysis

A prospective randomized trial has shown that there is a survival advantage for allogeneic transplant recipients who received granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood mononuclear cells (GPBMC) versus those who received bone marrow (BM) as a source of stem cells. The biological basis for this advantage is not clear and may be attributable to qualitative as well as quantitative differences in the CD34 cells, T cells, and/or the monocytes transplanted. To begin to address this issue, gene expression patterns in CD34 cells isolated from these 2 stem cell sources were compared to identify functional pathways that may distinguish these 2 populations. CD34 cells were isolated to purity from the BM and peripheral blood stem cells of multiple healthy donors. (The complete data set will be available at http://parma.fhcrc.org/lgraf upon publication.) Two separate RNA preparations from pooled samples from both sources were analyzed by Affymetrix Oligonucleotide Array chips for expression of over 6400 human genes. Comparative analyses among the samples showed that a small set of 28 sequences increased and 38 sequences decreased in expression more than 3-fold in both of the GPBMC samples compared to those in BM samples. More highly expressed genes include several for nuclear proteins and transcriptional factors. Functional categorization of the genes decreased in expression indicated sequences influential in cell cycle progression, in agreement with the recognized quiescence of circulating CD34 cells. Multiple transcriptional regulators and chemokines were also found to be decreased. These data emphasize that in addition to increased numbers of CD34 cells, G-CSF mobilization also results in significant qualitative changes. Whether they impact engraftment remains to be determined.

CD34 cell dose in granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell grafts affects engraftment kinetics and development of extensive chronic graft-versus-host disease after human leukocyte antigen-identical sibling transplantation

A retrospective analysis of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cell (G-PBMC) products harvested from healthy donors indicates significant variability in both the absolute number and relative proportion of CD34, CD3, and CD14 cells obtained. This report examined whether variations in the cellular composition of G-PBMC products correlated with clinical outcomes after myeloablative allogeneic transplantation. The numbers of CD34, CD3, and CD14 cells infused into 181 human leukocyte antigen (HLA)-identical sibling recipients were analyzed with respect to tempo of engraftment, acute graft-versus-host-disease (GVHD), clinical extensive chronic GVHD, overall survival, and disease relapse. Neither acute GVHD, overall survival, nor disease relapse was statistically significantly associated with CD34, CD3, or CD14 cell doses or the CD14 to CD3 ratio. CD3 and CD14 cell doses and CD14 to CD3 ratios did not correlate with the tempo of neutrophil and platelet engraftment. However, increasing CD34 cell numbers were significantly associated with accelerated neutrophil (P =.03) and platelet (P =.01) engraftment. Higher doses of CD34 cells (> 8.0 x 10(6)/kg) were also associated with a significantly increased hazard of clinical extensive chronic GVHD (HR = 2.3, 95% confidence interval [CI] 1.4-3.7, P =.001), but neither CD3 nor CD14 doses were statistically significantly associated with chronic GVHD. It was concluded that CD34 cell dose in G-PBMC grafts appears to affect both the engraftment kinetics and the development of clinical extensive chronic GVHD in HLA-identical sibling recipients but without a demonstrable impact on survival, relapse, and acute GVHD. Given the morbidity associated with extensive chronic GVHD, efforts to further accelerate engraftment in HLA-matched sibling transplants by increasing CD34 cell number in G-PBMC products may be counterproductive.

Hematopoietic responses to stress conditions in young dogs compared with elderly dogs

Clinical observations show that older patients do not tolerate high-dose chemoradiotherapy as well as younger patients. It is unclear whether this is due to age-related differences in their responses to hematopoietic injury or to differential toxicities to other organs. In the present study, 6 young (0.5 years) and 6 elderly (8 years) dogs were challenged with 7 repeated nonlethal doses of 50 or 100 cGy total body irradiation (TBI) each (total 550 cGy), and 21 days of recombinant canine granulocyte-colony stimulating factor (rcG-CSF) after the last TBI dose. Recoveries of absolute neutrophil, platelet, and lymphocyte counts after each TBI dose, responses to rcG-CSF treatment, and telomere lengths in neutrophils were compared before and after the study. No differences were found in recoveries of neutrophils, platelets, or in responses to rcG-CSF among young and old dogs. In contrast, recoveries were suggestively worse in younger dogs. After rcG-CSF, platelet recoveries were poor in both groups compared with previous platelet recoveries (P <.01). Consequently, 2 old and 3 young dogs were euthanized because of persistent thrombocytopenia and bleeding. At the study's completion, marrow cellularities and peripheral blood counts of the remaining young and elderly dogs were equivalent. The telomere lengths in both groups were significantly reduced after the study versus beforehand (P =.03), but the median attritions of telomeres were not different. It was concluded that aging does not appear to affect hematopoietic cell recoveries after repeated low-dose TBI, suggesting that poor tolerance of radiochemotherapy regimens in older patients may be due to nonhematopoietic organ toxicities rather than age-related changes in hematopoietic stem cells reserves.

Hematopoietic cell transplantation in older patients with hematologic malignancies: replacing high-dose cytotoxic therapy with graft-versus-tumor effects

Toxicities have limited the use of allogeneic hematopoietic cell transplantation (HCT) to younger, medically fit patients. In a canine HCT model, a combination of postgrafting mycophenolate mofetil (MMF) and cyclosporine (CSP) allowed stable allogeneic engraftment after minimally toxic conditioning with low-dose (200 cGy) total-body irradiation (TBI). These findings, together with the known antitumor effects of donor leukocyte infusions (DLIs), led to the design of this trial. Forty-five patients (median age 56 years) with hematologic malignancies, HLA-identical sibling donors, and relative contraindications to conventional HCT were treated. Immunosuppression involved TBI of 200 cGy before and CSP/MMF after HCT. DLIs were given after HCT for persistent malignancy, mixed chimerism, or both. Regimen toxicities and myelosuppression were mild, allowing 53% of eligible patients to have entirely outpatient transplantations. Nonfatal graft rejection occurred in 20% of patients. Grades II to III acute graft-versus-host disease (GVHD) occurred in 47% of patients with sustained engraftment. With median follow-up of 417 days, survival was 66.7%, nonrelapse mortality 6.7%, and relapse mortality 26.7%. Fifty-three percent of patients with sustained engraftment were in complete remission, including 8 with molecular remissions. This novel allografting approach, based on the use of postgrafting immunosuppression to control graft rejection and GVHD, has dramatically reduced the acute toxicities of allografting. HCT with the induction of potent graft-versus-tumor effects can be performed in previously ineligible patients, largely in an outpatient setting. Future protocol modifications should reduce rejection and GVHD, thereby facilitating studies of allogeneic immunotherapy for a variety of malignancies. (Blood. 2001;97:3390-3400)

Characterization and functional analysis of laminin isoforms in human bone marrow

Laminins are a family of disulfide-linked heterotrimeric proteins consisting of 3 different subunits termed alpha, beta, and gamma chains. Combinations of 11 characterized laminin subunits (alpha 1-alpha 5, beta 1-beta 3, and gamma 1-gamma 3) generate at least 12 laminin isoforms, which can serve different functions. Although expression of laminin in the hematopoietic microenvironment has been known for many years, the nature of the laminin isoforms present in the human bone marrow is poorly characterized. The present study attempts to clarify this issue. Reverse transcriptase-polymerase chain reaction analysis of human bone marrow stromal cells suggested the expression of many laminin isoforms in the marrow. Northern blot and immunoblot analysis, however, showed that laminin-8/9 and laminin-10/11 are the most abundant laminin isoforms synthesized by human bone marrow stromal cells. Other isoforms, if present, certainly play a minor role in the hematopoietic microenvironment. Functionally, laminin-10/11 preparations showed strong adhesive interactions with human CD34(+) cell lines. Antibodies against the beta 1 integrin subunit inhibited these interactions. Other laminin isoforms, especially laminin-1 and laminin-2/4, showed only weak or no adhesive interactions with the hematopoietic cell lines tested, explaining former negative results. In addition to its adhesion-mediating properties, laminin-10/11 preparations also showed a mitogenic activity for human hematopoietic progenitor cells. Taken together, these data suggest that laminin in the bone marrow plays a hitherto unexpected important function in the development of hematopoietic progenitor cells. (Blood. 2000;96:4194-4203)

Polyclonal hematopoiesis with variable telomere shortening in human long-term allogeneic marrow graft recipients

Donor-derived hematopoiesis was assessed in 17 patients who received allogeneic marrow grafts from HLA-matched siblings between 1971 and 1980. Complete blood counts were normal or near normal in all patients except one. Chimerism analyses, using either dual-color XY-chromosome fluorescence in situ hybridization (FISH) or analysis of variable number tandem repeat loci, indicated that 15 out of 16 patients had greater than 97% donor-derived hematopoiesis, whereas 1 patient had indeterminate chimerism. All 12 recipients of grafts from female donors exhibited polyclonal hematopoiesis by X-linked clonal analysis with the use of molecular probes. Of the 17 recipients, 9 exhibited a less than 1.0-kilobase shortening of granulocyte telomere length compared with their respective donors, according to terminal restriction fragment analysis or flow-FISH with a fluorescein-labeled peptide nucleic acid probe. These data suggest that under standard transplantation conditions, the stem cell proliferative potential is not compromised during hematopoietic reconstitution. (Blood. 2000;96:3991-3994)

Expansion and transduction of nonenriched human cord blood cells using HS-5 conditioned medium and FLT3-L

Cord blood (CB) stem cell transplantations have been associated with delayed hematopoietic engraftment. This has most likely been due to the limited numbers of hematopoietic short-term repopulating cells in CB. Ex vivo expansion of CB has been attempted, and expansion of CD34-enriched CB has been successful; however, CD34 enrichment procedures are in general associated with substantial cell loss. Thus, we have studied culture conditions for expansion of nonenriched CB. Nonenriched CB cells were cultured for 21 days in the presence of conditioned medium from the HS-5 stromal cell line and FLT3-L or alternatively in the presence of FLT3-L, stem cell factor (SCF), megakaryocite growth and development factor (MGDF), and granulocyte colony-stimulating factor (G-CSF) (FSMG), either on fibronectin fragment CH-296-coated dishes or on uncoated dishes. With all four culture conditions, the number of mononuclear cells initially decreased until day 7 and then increased until the end of the expansion cultures. Overall expansion using HS-5 and FLT3-L resulted in superior expansion of MNC and CFU-C (44-/34-fold) for both cultures with and without CH-296 compared to FSMG (18-/17-fold). Expansion on CH-296 was less efficient than expansion on tissue culture-treated wells without CH-296 for both conditions. We then studied the best time for transduction on nonenriched CB. In contrast to enriched CD34 cells, we found for both conditions, HS-5/FLT3-L and growth factor cocktail, higher transduction efficiencies when cells were transduced on day 7 as compared to day 2. Gene transfer rates up to 45% were achieved with both conditions, which corresponded with the increased number of cells in S phase on day 7 compared to day 2. We conclude that HS-5 and FLT-3L allow efficient expansion and transduction of nonenriched CB.

Graft-versus-host disease and donor-directed hemagglutinin titers after ABO-mismatched related and unrelated marrow allografts: evidence for a graft-versus-plasma cell effect

The gradual disappearance of host antidonor isohemagglutinins after major ABO-mismatched hematopoietic stem cell (HSC) allografts has been attributed to the gradual destruction of host plasma cells by graft-versus-host effects. To corroborate this hypothesis, we retrospectively analyzed results from 383 major or major/minor ABO-mismatched unrelated and related HSC allografts performed between 1983 and 1998. All patients were conditioned by high-dose pretransplant therapy and given methotrexate/cyclosporine for graft-versus-host disease (GvHD) prophylaxis. Of the 383 patients, 155 had HLA-matched related and 228 had unrelated grafts. We asked whether unrelated recipients experienced a more rapid disappearance of isohemagglutinins than related recipients, and whether, within the groups of related and unrelated recipients, the titer disappeared faster in patients with GvHD than in those without GvHD. The median time to reach undetectable antidonor IgG and IgM titers was significantly shorter in unrelated recipients (46 versus 61 days; P =.016). In addition, related recipients with GvHD had a 2. 2-fold increased likelihood (1.12-4.39,95% CI; P =.02) of reaching undetectable titers within 100 days than patients without GvHD. The persistence of antidonor isohemagglutinins led to significantly increased red blood cell (RBC) transfusion requirements in the ABO-mismatched related patients compared with ABO-matched counterparts. However, time to neutrophil and platelet engraftment, incidence of GvHD, and survival were not influenced by ABO incompatibility. In conclusion, our results corroborate the hypothesis that the rate of disappearance of antidonor isohemagglutinins after ABO-mismatched allogeneic HSC grafts is influenced by the degree of genetic disparity between donor and recipient, suggesting a graft-versus-plasma cell effect.

Interleukin-1 (IL-1) inhibits growth of cytomegalovirus in human marrow stromal cells: inhibition is reversed upon removal of IL-1

A Toledo strain cytomegalovirus (CMV) containing the gene for green fluorescent protein (GFP) under the control of elongation factor-1 promoter was used to study infection of human marrow stromal cells. Two stromal cell lines were used: HS-5, which secretes copious amounts of known cytokines and interleukins; and HS-27a, which does not secrete these activities. CMV growth and spread was monitored by counting green plaques and quantitating GFP intensity. Initial studies indicated that, whereas HS-5 and 27a have similar susceptibilities to infection, as evidenced by the same number of GFP+ cells at day 2, HS-5 appears more resistant to growth and spread of CMV. Furthermore, conditioned media from HS-5 (HS-5 CM) inhibited CMV plaque formation in HS-27a, suggesting that factors secreted by HS-5 are responsible for limiting CMV growth. Neutralizing antibodies against interleukin-1alpha (IL-1alpha) and IL-1beta completely blocked the ability of HS-5 CM to limit viral growth, suggesting that IL-1, which is known to be present in HS-5 CM, is responsible for this effect. When exogenous IL-1beta was added to CMV-infected HS-27a, both the number of plaques and the intensity of GFP was significantly reduced in IL-1-treated HS-27a compared with untreated HS-27a (the number of plaques by day 18 was 20 +/- 3 v 151 +/- 12/well, respectively; GFP intensity was 535 +/- 165 v 6,516 +/- 652/well, respectively, in 4 separate experiments). At day 21, when IL-1beta-treated, CMV-infected cultures were passaged and then cultured in the absence of IL-1beta, CMV growth progressed with the kinetics of the original untreated culture, indicating that the IL-1beta effect is reversible. Because HS-27a expresses the type I IL-1 receptor, we speculate that the antiviral effects are mediated through IL-1-induced changes in cellular gene expression. DNA chip analysis of mRNA from IL-1beta-treated and nontreated HS-27a cells has identified some candidate molecules.

Haemopoietic reconstitution by donor-derived myelodysplastic progenitor cells after haemopoietic stem cell transplantation

A 50-year-old woman who was retrospectively diagnosed with an early asymptomatic myelodysplastic syndrome (MDS) served as a haemopoietic stem cell donor for her HLA-identical sister who had chemotherapy-refractory non-Hodgkin's lymphoma. The MDS of the donor was classified as refractory anaemia (RA) and cytogenetically characterized by deletion of the long arm of chromosome 20 [del(20q)]. Donor cell engraftment in marrow and peripheral blood was analysed over a period of 5 months after transplant using conventional cytogenetics, fluorescence in situ hybridization, and variable number of tandem repeats. Neutrophil counts >0.5 x 109/l and platelet counts >20 x 109/l were reached promptly on days 12 and 24, respectively. Throughout the period of observation the percentage of cells with the del(20q) abnormality in the recipient's marrow and peripheral blood was comparable to the proportion of these cells in the donor. These data indicate that the abnormal clone was capable of homing to the marrow, proliferating, differentiating, and therefore contributing to haemopoiesis in a relatively efficient manner. This implies that MDS progenitor cells may not have homing and growth deficiencies, a finding that has particular relevance for autologous transplantation in MDS patients where tumour cells potentially contaminate the graft.

Dissecting the marrow microenvironment

Cloned human stromal cell lines representing functionally distinct cellular components of the marrow microenvironment were generated to serve as tools for identifying gene products that regulate hematopoiesis. Oligonucleotide arrays, or "gene chips" were used to provide a comprehensive comparison of gene expression among the cell lines. One line, designated HS-5, was found to secrete large amounts of cytokines, and conditioned media from this line was found to support the ex vivo expansion of both immature and mature progenitors. In contrast, a second line, designated HS-27a, does not secrete known cytokines but does support cobblestone area formation by CD34+/38lo cells. HS-27a, but not HS-5, was also found to express hJagged1, a ligand for Notch1, which may function to influence cell fate decisions of hematopoietic precursors. Both cell lines are currently being used to identify other gene products that regulate hematopoiesis and to generate reagents that will allow more formal evaluation of the putative role of hJagged1 in hematopoietic cell fate decisions.

Endogenous FLT-3 ligand serum levels are associated with disease stage in patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDS) caused by a clonal hematopoietic stem cell disorder progress to either overt leukemia or cytopenia, which leads to lethal infection or bleeding. Although several clinical trials have attempted to reverse cytopenia by using hematopoietic growth factors (HGF), success has been limited due in part to a limited understanding of the role of HGF in MDS progression. The FLT3 ligand, which binds to and activates the FLT3 receptor, does not have a stimulatory effect on hematopoietic cells, but can synergize with other HGF to support the expansion of both immature and committed progenitors. Using ELISA technology we measured endogenous serum levels in 93 patients with MDS: 29 RA, 1 RARS, 31 RAEB, 23 RAEBt, 9 CMML. 48.3% of RA patients' sera had significantly elevated FLT3 ligand levels ranging from 404 to 5735 pg/ml, whereas none of the RAEB, RAEBt, or CMML patients sera had levels different from controls. No significant correlation was found between FLT3 ligand levels and peripheral blood counts, bone marrow cellularity, age, cytogenetic abnormalities, or survival. Our data suggest that FLT3 ligand levels can be upregulated early in the course of MDS, which may represent an appropriate response to a decreased number of normal progenitors, or alternatively a dysregulated HGF system.

The role of accessory cells in allogeneic peripheral blood stem cell transplantation

Granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (G-PBMC) have been used increasingly to reconstitute hematopoiesis after myeloablative therapy in allogeneic transplantation. Compared with conventional bone marrow, faster engraftment is consistently observed with G-PBMC, with differences more pronounced in platelet than in neutrophil recovery. G-PBMC contain not only severalfold more CD34+ cells than bone marrow but also, on average, 50-fold more monocytes, which may stimulate stromal cell function and facilitate engraftment. Although G-PBMC also contain 10-fold more T cells, the incidence and severity of acute graft-vs.-host disease (GVHD) is no higher than that observed in allogeneic bone marrow transplantation. Hypothetically, these clinical observations can be explained by the direct effect of G-CSF on T cell function as demonstrated by polarization of T cells expressing the T helper type 2 (Th 2) cytokine interleukin (IL)-4 in the murine model. Alternatively, G-PBMC may contain cells that actively suppress donor T cell responsiveness. Recent reports indicate that the large number of CD14+ monocytes in G-PBMC can suppress donor T cell proliferation in vitro. This effect may be attributable to both the increased ratio of CD14+:CD3+ cells in G-PBMC and the evidence that CD14+ cells in G-PBMC have decreased expression of both B7.2 and HLA-DR. There is some indication that natural killer (NK) cell number and function may be augmented in G-PBMC, which could have a favorable impact on the graft-vs.-leukemia (GVL) effect. Therefore, both the CD34+ and accessory cell content of G-PBMC may be important in early engraftment by controlling acute GVHD and facilitating GVL.

Ex vivo expansion of immature 4-hydroperoxycyclophosphamide-resistant progenitor cells from G-CSF-mobilized peripheral blood

The application of ex vivo expansion to cell products pharmacologically purged in vitro may provide sufficient numbers of cells for rapid engraftment in a product with reduced tumor burden. To pursue this possibility we evaluated the effect of 4-hydroperoxycyclophosphamide (4-HC) treatment on granulocyte colony-stimulating factor-mobilized peripheral blood stem cells (G-PBSC) and their subsequent expansion potential. A small number of G-PBSC CD34+ cells are resistant to 4-HC and are phenotypically and functionally immature. 4-HC-resistant G-PBSC cells are CD34+ bright, CD38+/-, DR(lo), CD13(lo), CD33-, CD71-, and rhodamine dull. In six experiments, treating G-PBSC with 60 microg/mL of 4-HC at 37 degrees C for 30 minutes reduced the number of colony-forming units (CFUs) per 5000 CD34+ cells by 96.3% (from 1333 +/- 137 to 46.5 +/- 11). This purging also reduced the frequency of 5-week long-term culture initiating cells (LTC-ICs) from 1/39 (range 1/27 to 1/62) to <1/1680 (range 1/1180 to 1/2420). Ex vivo expansion cultures were used to compare the proliferative potential of treated and untreated CD34+ cells. These cells were cultured with either the HS-5 stromal cell line serum-deprived conditioned media supplemented with 10 ng/mL kit ligand (HS-5CM/KL) or a recombinant growth factor mix (GFmix) containing 10 ng/mL each of interleukin (IL)-1, IL-3, IL-6, KL, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and 3 U/mL of erythropoietin. Culturing untreated CD34+ G-PBSC with 10% HS-5CM/KL increased total nucleated cells by 460-fold after 15 days. Progenitors, which were measured as CFUs, also increased by 47-fold over the same period. More significantly, culturing the 4-HC-treated CD34+ cells with HS-5/KL increased CFUs 98-fold and the nucleated cells increased 4573-fold. The absolute number of CFUs present after expansion of the 4-HC-resistant cells with HS-5CM/KL was threefold higher than that detected before purging and significantly higher than that obtained with GFmix. These data indicate that G-PBSC contain a very immature pool of cells not detectable using the 5-week LTC-IC assay, but have extremely high proliferative potential. Additionally, pharmacological purging of G-PBSC greatly reduces mature cells while retaining an immature population. Also significant is the finding that supernatant from the HS-5 bone marrow stromal cell line plus KL can fully regenerate progenitors from the 4-HC-resistant CD34+ G-PBSC.

Production of interleukin-10 by granulocyte colony-stimulating factor-mobilized blood products: a mechanism for monocyte-mediated suppression of T-cell proliferation

Previous reports showed that granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (G-PBMC) are hyporesponsive to alloantigen compared with control PBMC. In the current study, neutralizing antibodies to interleukin-10 (IL-10) increased the proliferative response of G-PBMC to alloantigen by 50. 14% (+/- 12.79%; n = 8), whereas the proliferative response of control PBMC was not affected. The inhibition of OKT3-stimulated CD4 cell proliferation by G-PBMC-derived CD14(+) cells could also be abrogated by the addition of IL-10 neutralizing antibodies. Further, IL-10 levels correlated with the number of CD14 cells in these cultures. Constitutive IL-10 mRNA levels detected by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) were 10-fold higher in G-PBMC compared with control PBMC. This translated into significantly higher IL-10 levels after 24-hour lipopolysaccharide (LPS) stimulation of G-PBMC compared with control PBMC (P = .036). IL-10 mRNA levels were also fivefold higher in isolated G-PBMC-derived CD14 cells compared with control CD14 cells. This corresponded to increased constitutive production of IL-10 by isolated G-PBMC-derived CD14 cells compared with control CD14 cells (357.2 +/- 104.5 v 51.7 +/- 30.5, P = .051). In conclusion, these data suggest that monocytes contained within G-PBMC, which, in comparison to marrow, are increased in absolute number and relative proportion to T cells, may suppress T-cell responsiveness by secretion of IL-10.

The human homolog of rat Jagged1 expressed by marrow stroma inhibits differentiation of 32D cells through interaction with Notch1

A cDNA clone encoding the human homolog of rat Jagged1 was isolated from normal human marrow. Analyses of human stromal cell lines indicate that this gene, designated hJagged1, is expressed by marrow stromal cells typified by the cell line HS-27a, which supports the long-term maintenance of hematopoietic progenitor cells. G-CSF-induced differentiation of 32D cells expressing Notch1 was inhibited by coculturing with HS-27a. A peptide corresponding to the Delta/Serrate/LAG-2 domain of hJagged1 and supernatants from COS cells expressing a soluble form of the extracellular portion of hJagged1 were able to mimic this effect. These observations suggest that hJagged1 may function as a ligand for Notch1 and play a role in mediating cell fate decisions during hematopoiesis.

Impaired induction of the CD28-responsive complex in granulocyte colony-stimulating factor mobilized CD4 T cells

Use of the CD28/B7 costimulatory signal for T-cell activation was analyzed in granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood mononuclear cells (G-PBMCs) and in peripheral blood mononuclear cells obtained before administration of G-CSF (preG-PBMCs). CTLA4Ig inhibition of OKT3-stimulated proliferation was significantly lower in G-PBMCs compared with preG-PBMCs (39.9% +/- 5.6% and 72.2% +/- 5.4%, respectively; P < .001). Furthermore, as shown in electrophoretic mobility-shift assays, the inducible level of the T-cell transcription factor CD28 responsive complex (CD28RC) was suppressed in CD4 cells derived from G-PBMC. However, depletion of CD14 cells from G-PBMCs restored CD28RC induction to normal levels. Taken together, these findings suggest that the large number of CD14 monocytes in G-PBMCs may limit T-cell responsiveness by suppressing the induction of the CD28RC.

Extrinsic control of stem cell fate: practical considerations

Decades of experimental data suggest that hematopoietic stem cells can remain quiescent, divide, differentiate or die and further, that these cell fate decisions are determined by extracellular signals provided by the hematopoietic microenvironment (ME). Given the importance of the ME for regulating hematopoiesis, it is imperative that transplanted stem cells migrate efficiently and home to appropriate niches where they can receive regulatory signals. Currently the rapid engraftment seen after transplantation of cytokine-mobilized blood-derived stem cells would suggest that these cells are well-equipped for homing. More recent concerns have now been raised by the possibility that in vitro expansion of these stem cells may diminish their ability to engraft. One possible explanation for this is that expansion protocols may alter adhesion molecule expression and consequently homing. Data presented in this report indicate that expression of adhesion molecules is altered following in vitro exposure to recombinant cytokines, and that various combinations of cytokines differentially modulate adhesion molecule expression.

Association of specific cytomegalovirus genotypes with death from myelosuppression after marrow transplantation

A retrospective analysis of cytomegalovirus (CMV) genotype was conducted on 281 CMV isolates obtained from marrow transplant recipients. The genotyping was based on sequence variations in the gene encoding envelope glycoprotein B (gB) as detected by restriction analysis of polymerase chain reaction (PCR)-amplified gB DNA. Among all isolates studied, the distribution of gB types 1-4 was 48.4%, 16.4%, 24.6%, and 8.2%, respectively, with only 2.5% of all isolates containing more than one gB type. The association of gB types with acute graft-versus-host-disease (GVHD) and death related to myelosuppression was examined using appropriate multivariable regression models. Covariables in addition to gB type included underlying disease type, donor-recipient HLA matching, donor CMV serostatus, and age as a continuous variable. Death associated with myelosuppression occurred in 2.9% or 4 of 136 patients with gB1, 0% or 0 of 46 patients with gB2, 21.7% or 15 of 69 patients with gB3, and 17.4% or four of 23 patients with gB4. The significant association of CMV gB type with death due to myelosuppression was maintained in a multivariable analysis (P < .001). In addition, the data also suggested that gB types 3 and 4 may be associated with a reduced hazard of grades II to IV acute GVHD.

Differential modulation of adhesion markers with ex vivo expansion of human umbilical CD34+ progenitor cells

The effect of different expansion protocols on the expression levels of CD49dw/CD29 (VLA-4), CD11a/CD18 (LFA-1), CD31 (PECAM-1), CD44, and CD34 was determined after cord blood CD34+ cells were cultured for defined periods with the following: 1) A growth factor mix (GFmix) containing interleukin (IL)-1, IL-3, IL-6, kit ligand (KL), G-CSF, GM-CSF, and erythropoietin (Epo); 2) IL-3 + KL; and 3) HS-5 (a human stromal cell line supernatant) + KL. Before culturing, cord blood CD34+ cells (> 95% purity) were 94 +/- 5% CD31+, 98 +/- 1% CD44+, 66 +/- 29% VLA-4+, and 68 +/- 18% LFA-1+ (mean +/- SEM). Immunophenotyping and morphological examination of pre- and post-cultured cells indicated that GFmix preferentially supported erythroid development, while IL-3+KL and HS-5+KL preferentially supported myeloid development. Similar to what other investigators have reported, there was an absolute increase in CD34+ cell numbers as well as clonogenic precursors with ex vivo expansion. However, the majority of clonogenic precursors post-expansion expressed CD34 antigen at reduced levels. Examination of adhesion molecules indicated that a majority of cells cultured with GFmix expressed PECAM-1 and LFA-1 at undetectable levels, but PECAM-1 and LFA-1 levels remained essentially unchanged when cells were cultured with IL-3+KL and HS-5+KL. Overall VLA-4 expression levels slightly increased and CD44 expression levels were more heterogeneous with ex vivo expansion. Nevertheless, LFA-1, VLA-4, PECAM-1, and CD44 expression levels remained essentially unchanged on cultured progeny retaining a CD34 phenotype, independent of the culture system used. Together these results indicate that differential modulation of adhesion markers occur with different culture conditions, yet adhesion receptor expression levels on progeny cells retaining a CD34 phenotype are essentially maintained independent of the culture conditions. And although there is an absolute increase in CD34+ cells after ex vivo expansion, a majority of clonogenic precursors have reduced levels of CD34 antigen.

Phenotype and engraftment potential of cytokine-mobilized peripheral blood mononuclear cells

Cytokine-mobilized peripheral blood stem cell products are increasingly used for hematopoietic reconstitution after myeloablative therapy. Favorable engraftment kinetics, the ease of harvest, and the large number of CD34+ cells obtained that allow for graft manipulations (ie, tumor cell or T-cell depletion) have made this stem cell source an attractive alternative to marrow. More recent data suggest that in addition to the increased number of CD34 cells, there may be also qualitative differences between leukapheresis products and marrow. In the allogeneic transplantation setting, the one log more T cells contained in granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells compared with marrow has not translated into more severe graft-versus-host disease, indicating possible differences in T-cell or accessory-cell function. Whether such differences will compromise graft-versus-leukemia effects and disease-free survival remains to be seen. Nevertheless, it is reasonable to speculate that cytokine-mobilized peripheral blood products may eventually replace marrow as a source for hematopoietic stem cells. However, each new mobilization strategy needs to be evaluated carefully, as comparable increases in CD34 cell numbers may not necessarily affect the same, as yet underlined, qualitative changes that make this product so attractive.

Suppression of alloantigen-induced T-cell proliferation by CD14+ cells derived from granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells

The proliferative responsiveness of granulocyte colony-stimulating factor (G-CSF)-mobilized blood was studied in uni-directional mixed leukocyte cultures. Unfractionated mononuclear cells from mobilized blood obtained by leukapheresis at day 4 after initiation of G-CSF (G-PBMC) were hyporesponsive (31.5% +/- 9.2% response, P = .003) compared to mononuclear cells obtained from the peripheral blood before administration of G-CSF (preG-PBMC). There was great variability among donors when purified preG- and G-CD4 cells were compared. In eight of 10 donors, G-CD4 cells were equally responsive or moderately hyporesponsive; in two of 10 donors, G-CD4 cells were more strikingly hyporesponsive. CD14 cells derived from leukapheresis products (G-CD14 cells) suppressed alloantigen-induced proliferation by 48.6% +/- 7.5% when added to preG-PBMC or preG-CD4 cells at responder-CD14 ratios of 2:1 (P < .001). Suppression was evident (14.4% +/- 5.0%) even at responder-CD14 ratios of 8:1 and was largely contact-independent. PreG- and G-CD14 cells had equivalent potency in suppressing proliferative responses. Given that G-CSF-mobilized blood cell grafts contain 50-fold more CD14 cells and only 10-fold more T cells than marrow, we propose that suppression of donor T cells by the large proportion of monocytes present in leukapheresis products could contribute to the unexpectedly low incidence and severity of graft-versus-host disease after peripheral blood stem cell transplantation.

Mortality hazard functions as related to neutropenia at different times after marrow transplantation

We characterized the relationship between severe neutropenia and risk of death in 2,276 patients after marrow transplantation to define objective and clinically relevant criteria that could be used to judge the timing and potential value of interventions designed to improve survival in patients with delayed initial engraftment. Proportional hazard models were used to estimate the relative risk of death before day 100 among patients alive on any given day with an absolute neutrophil count (ANC) less than 100/microL compared with those alive on the same day with an ANC > or = 100/microL. Between day 10 and 14, the risk ratio remained close to 1.0, indicating that the risk of death before day 100 for patients with an ANC less than 100/microL was similar to that for patients with an ANC > or = 100/microL. Between day 15, when 38% of patients had an ANC less than 100/microL, and day 26, when 3.8% of patients had an ANC less than 100/microL, the risk ratio showed an overall upward trend, indicating that patients with an ANC less than 100/microL had a higher risk of death before day 100 than those with an ANC > or = 100/microL. Thereafter, the risk ratio fluctuated between 2.01 and 5.78, indicating consistently higher risks of mortality in patients with severe neutropenia. However, allogeneic and autologous transplant recipients each had distinctive risk ratio patterns. These results could be helpful in deciding the appropriate timing for treatment given to improve graft function after marrow transplantation.

Normal human peripheral blood mononuclear cells mobilized with granulocyte colony-stimulating factor have increased osteoclastogenic potential compared to nonmobilized blood

Single-cell suspensions of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (G-PBMC) cultured in alpha minimal essential medium (alphaMEM) containing 10% fetal bovine serum formed multicellular aggregates within 24 hours. In six separate experiments, formation of aggregates appeared to be dependent on cell density per surface area, so that 5.8 +/- 1.3 aggregates formed per 1 x 10(5) cells when G-PBMC were cultured at densities greater than or equal to 1 x 10(5) cells/cm2. The frequency of aggregate formation was less than 1 per 10(5) cells when G-PBMC were cultured at densities less than 1 x 10(5) cells/cm2. Once formed, aggregates became adherent within 72 hours, and then, over the course of 21 days, released CD3/CD4/CD25-positive cells into the supernatant. This T-cell production peaked between days 7 and 14, reaching a total of 1,269 +/- 125.9 cells released per aggregate by day 21. Between days 14 and 21, the aggregates also generated macroscopic clusters of adherent mononuclear and giant multinucleated cells that stained positive for tartrate-resistant acid phosphatase (TRAP). At 4 weeks, the macroscopic foci coalesced into monolayers. Multinucleated TRAP-positive cells were distinguished from macrophage polykaryons by the absence of CD14 expression and the presence of osteoclast-specific membrane receptors for calcitonin and alphavbeta3-vitronectin. The osteoclast nature of these cells was further demonstrated by their ability to form resorption lacunae on dentine slices. Comparable osteoclast formation was not detected in cultures of normal marrow or normal nonmobilized peripheral blood.

CD14+ cells in granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells induce secretion of interleukin-6 and G-CSF by marrow stroma

The ability of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (G-PBMCs) to induce secretion of cytokines in primary long-term marrow cultures (LTC) or in the human marrow stromal cell line HS23 was compared with that of marrow mononuclear cells. Equal numbers of G-PBMCs or marrow mononuclear cells were added to stromal cultures, supernatants were harvested at day 4 and levels of interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-6, G-CSF, and tumor necrosis factor alpha (TNF alpha) were determined. G-PBMCs induced 21.4-fold higher levels of IL-6 and 12.5-fold higher levels of G-CSF in LTC cocultures compared with marrow mononuclear cells and induced 20.6-fold more IL-6 and 6.3-fold more G-CSF when added to HS23 cells. Experiments using sorted populations of CD20+, CD3+, and CD14+ cells showed that CD14+ cells within G-PBMCs were responsible for triggering the production of IL-6 and G-CSF. The effect did not require cell-cell contact and was inhibited when neutralizing antibodies to IL-1 alpha and IL-1 beta were used in combination. In these experiments, the greater stimulating ability of G-PBMCs is most likely attributable to the greater number of CD14+ cells in G-PBMCs (26.1+% +/- 2.3%) compared with marrow (2.5% +/- 0.8%), because equal numbers of CD14+ cells sorted from marrow and G-PBMCs showed comparable ability to induce IL-6 and G-CSF when placed directly on stromal cells.

Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony stimulating factor

Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSC). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 90 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graft-versus-host-disease (GVHD), grades II-IV occurred in 47% of patients and grades III-IV in 17%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. There have also been successful reports of using G-CSF mobilized allogeneic PBSC following second transplants for graft rejection or relapse. Allogeneic PBSC have been infused without reconditioning for correction of graft failure and unmodified or CD34 selected PBSC have also been given with marrow to augment the dose of hematopoietic cells. Further studies are needed to define the role of allogeneic PBSC for transplantation, refine PBSC mobilization and collection techniques and to evaluate the long-term effects of cytokines in normal donors.

Transplantation of allogeneic peripheral blood stem cells

Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSCs). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 100 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graft-versus-host-disease (GVHD) grades II-IV occurred in 44% of patients and grades III-IV in 16%. From a small number of evaluable patients surviving for more than 100 days, it appears the incidence of chronic GVHD is approximately 50%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. Further studies are needed to define the role of allogeneic PBSCs for transplantation, to refine PBSC mobilization and collection techniques, and to evaluate the long-term effects of cytokines in normal donors.

Benign marrow progenitors are enriched in the CD34+/HLA-DRlo population but not in the CD34+/CD38lo population in chronic myeloid leukemia: an analysis using interphase fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) was used to discriminate between benign and malignant cells in sorted populations of chronic myelogenous leukemia (CML) marrow. FISH has the advantage of allowing for a cell by cell analysis of the breakpoint cluster region (BCR) gene rearrangement immediately after flow sorting in nondividing G0/G1 cells that are potentially transcriptionally inactive. We initially selected CD34+ cells with very low expression of the activation antigen CD38 as a candidate phenotype for an immature and hypothetically more benign cell population, but found no enrichment for Ph negativity in that subtype. In five CML samples, 55% +/- 3.3% (mean +/- SE) of CD34+/CD38hi cells had the BCR gene rearrangement, similar to 57% +/- 3.7% seen in the CD34+/CD38lo population. In contrast, subsequent experiments (n = 4) determined that the CD34+/HLA-DRlo population in CML marrow does contain an increased proportion of benign cells: 15% +/- 1% of the CD34+/DRlo cells were BCR rearranged, compared with 52% +/- 5.8% of the CD34+/DRhi cells (P = .001). Our results indicate that benign progenitors in CML are enriched within the CD34+ cells with low DR antigen expression, but not low CD38 expression. One possible interpretation of these observations is that low CD38 antigen expression is not as useful as low HLA-DR expression for isolating immature cells.

Identification of a novel DNA sequence differentially expressed between normal human CD34+CD38hi and CD34+CD38lo marrow cells

We have applied the recently developed differential display method to extend the molecular characterization of the less mature CD34+CD38lo bone marrow progenitors in comparison with the CD34+CD38hi cells to better understand their functional differences. Immunomagnetic enrichment of CD34+ cells followed by flow cytometry was used to isolate CD34+CD38lo and CD34+CD38hi cells from human organ donor bone marrow. A limited set of the poly A+ RNA sequences present in these two cell populations was amplified by a combination of reverse transcription with an anchored oligo dT-based primer and polymerase chain reaction with the same oligo dT primer and arbitrary decamers. A radioactive tracer allowed these sequences to be displayed as a series of bands on a denaturing polyacrylamide gel. Eight bands were chosen that appeared in multiple displays to represent gene sequences differentially expressed between CD34+CD38hi and CD34+CD38lo cells. Comparison of the sequences with public DNA sequence databases available identified one sequence as myeloperoxidase. Two other clones matched sequence fragments of unknown function, whereas the remaining five are novel sequences not present in existing databases. The relative level of expression of all of the sequences was tested by an independent reverse transcriptase-polymerase chain reaction with sequence-specific oligonucleotide primers. The lower level of myeloperoxidase mRNA in CD34+CD38lo cells was confirmed, as was the higher expression of the novel sequence 345. Sequence 345 expression is highest in CD34+CD38- cells and decreases with increased CD38 expression. It is expressed in negligible amounts in hematopoietic cell lines and other sources of human tissue, suggesting it may have a functional role in normal hematopoiesis.

Cell cycle and functional differences between CD34+/CD38hi and CD34+/38lo human marrow cells after in vitro cytokine exposure

The proliferation kinetics and clonogenic activity of CD34+/38hi (CD38hi) and CD34+/38lo (CD38lo) human marrow cells were measured before and after culturing the cells in vitro over a 6-day period in serum-deprived medium containing recombinant growth factors (interleukin-1 [IL-1], IL-3, IL-6, granulocyte colony-stimulating factor [G-CSF], granulocyte-macrophage [GM]-CSF, kit ligand, and erythropoietin). Before in vitro culture, 3% +/- 3% of the CD38lo and 13% +/- 2% of the CD38hi cells were in the S-phase of the cell cycle. The clonogenic activity of CD38hi cells was twofold greater than that of the CD38lo cells, as measured by colony-forming units (CFU) in short-term assays. However, CD38hi cells contained fewer pre-CFU than did the CD38lo cells, generating only 3 +/- 2 colonies per 1,000 cells after 4 weeks of culture on competent stromal layers, compared with 107 +/- 46 colonies per 1,000 cells from the CD38lo population. CD38hi and CD38lo cells exhibited distinctly different responses when cultured in serum-deprived medium supplemented with recombinant growth factors. After culturing cells for 24 hours, CD38lo cells essentially remained a noncycling population with only 5.1% +/- 3.0% of the cells cycling, whereas 44.2% +/- 6.9% of the CD38hi cells were in DNA synthesis. Gradually CD38lo cells were recruited into cycle, such that by 72 hours, approximately 28% of the CD38lo cells were in S-phase. However, during 6 days of culture, the percentage of cycling CD38lo cells never exceeded the proliferative response observed for CD38hi cells. Phenotype analysis conducted at day 6 indicated that 86% of the CD38hi population were no longer phenotypically CD34+/38hi, while 60% of CD38lo cells maintained a CD34+/38lo phenotype. Long-term cultures initiated with 6-day in vitro-expanded CD38lo cells showed approximately a twofold decrease in clonogenic activity attributable to a loss of erythroid precursors and a decrease in GM colonies. Thus, a proportion of CD38lo cells capable of generating CFU was maintained even after exposure to growth factors.

Functionally distinct human marrow stromal cell lines immortalized by transduction with the human papilloma virus E6/E7 genes

A replication-defective recombinant retrovirus containing the human papilloma virus E6/E7 genes (LXSN-16 E6E7) was used to immortalize stromal cells from human marrow. The E6/E7 gene products interfere with the function of tumor-suppressor proteins p53 and Rb, respectively, thereby preventing cell cycle arrest without causing significant transformation. Twenty-seven immortalized clones designated HS-1 to HS-27 were isolated, four of which are characterized in this report. Two cell lines, HS-5 and HS-21, appear to be fibroblastoid and secrete significant levels of granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage-CSF (GM-CSF), macrophage-CSF (M-CSF), Kit ligand (KL), macrophage-inhibitory protein-1 alpha, interleukin-6 (IL-6), IL-8, and IL-11. However, only HS-5 supports proliferation of hematopoietic progenitor cells when cocultured in serum-deprived media with no exogenous factors. Conditioned media (CM) from HS-5 promotes growth of myeloid colonies to significantly greater extent than a cocktail of recombinant factors containing 10 ng/mL of IL-1, IL-3, IL-6, G-CSF, GM-CSF, and KL and 3 U of erythropoietin (Epo). Two additional clones, HS-23 and HS-27, resemble "blanket" cells, with an epithelioid morphology, and are much larger, broader, and flatter when compared with HS-5 and HS-21. These lines secrete low levels of growth factors and do not support proliferation of isolated progenitor cells in cocultures. CM from HS-23 and HS-27 also fail to support growth of myeloid colonies. Both HS-23 and HS-27 express relatively high levels of VCAM-1, yet HS-27 is the only line that supports the formation of "cobblestone" areas by isolated CD34+38lo cells. We hypothesize that HS-5, HS-21, HS-23, and HS-27 represent functionally distinct components of the marrow microenvironment.

Aplastic anemia: analysis of stromal cell function in long-term marrow cultures

Marrow samples from 89 patients with aplastic anemia (AA) were evaluated for their ability to grow stromal layers in standard long-term marrow cultures (LTMCs). Results were highly variable: 6.8% failed to grow any stromal cells (group I); 42.5% either failed to grow to confluency or appeared to have a decreased number of adipocytes and/or macrophages (group II); and 52.8% appeared as normal confluent cultures with fibroblasts, adipocytes, and macrophages (group III). Analyses of patient data suggested that group I patients had a longer disease duration and poorer survival (P = .07). Enzyme-linked immunosorbent assay analysis of cytokine production was performed on 20 of the normal-appearing AA LTMCs and 12 LTMCs established from normal donors. Significant differences between the AA and control groups were apparent for macrophage inflammatory protein-1 alpha (MIP-1 alpha), interleukin-1 receptor antagonist (IL-1ra), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and leukemia-inhibitory factor (LIF). The most dramatic differences observed were elevated levels of MIP-1 alpha and GM-CSF and decreased levels of IL-1ra, particularly after IL-1 alpha stimulation. In contrast, IL-1 alpha stimulation of AA LTMCs produced levels of IL-6, LIF, and G-CSF comparable with those of controls. These data suggest that defects exist within the microenvironment of some AA marrows. Whether the majority of these defects are the cause or consequence of aplasia is not clear. However, we speculate that some of these abnormalities may contribute to the maintenance of the hypoplastic state and, in extreme cases, prevent engraftment of donor marrow.

An evaluation of renal tubular DNA laddering in response to oxygen deprivation and oxidant injury

It has recently been suggested that endonuclease activation and/or apoptosis, possibly triggered by oxidant stress, are important pathogenetic mechanisms in oxygen deprivation/reoxygenation-induced proximal tubular cell death. To explore this possibility, DNA "laddering," a characteristic feature of these processes, was sought in: (1) postischemic rat kidneys (25- or 40-min arterial clamping; 0, 1, 4, 8, 24, and 48 h and 6 days reflow); (2) posthypoxic isolate rat proximal tubular segments and (3) cultured human kidney proximal tubular cells (HK-2) subjected either to energy depletion plus Ca2+ overload (antimycin A plus 2-deoxyglucose plus Ca2+ ionophore A23187), or to H2O2-induced cell death. DNA was subsequently extracted, electrophoresed through agarose gels, and visualized with ethidium bromide or Southern blotting. To maximize ladder detection, DNA samples were also end-labeled with 32P dideoxyadenosine triphosphate with terminal deoxynucleotidyl transferase (tdt), followed by electrophoresis. None of the postischemic DNA samples demonstrated any laddering by either ethidium bromide staining or Southern analysis (apoptotic lymphocyte DNA was a positive control). However, trace laddering was apparent by the tat technique, commencing at 1 h of reflow, peaking at 24 h, and resolving slowly thereafter. This finding correlated with the morphologic expression of tubular necrosis, not apoptosis. Hypoxia/reoxygenation caused proximal tubular segment death (44 to 64%), and HK-2 cells were slowly killed by both the H2O2 and the energy depletion/Ca(2+)-loading protocols. However, neither protocol induced ethidium bromide- or tdt-detectable DNA laddering. It was concluded that: (1) minimal DNA laddering develops postischemia, and this change is reliably detected only by the tdt method; (2) it correlates with the morphologic expression of tubular necrosis, not apoptosis; and (3) in vitro oxidative- and energy depletion-mediated proximal tubular cell death can be dissociated from DNA ladder formation.

Increased gene transfer into human hematopoietic progenitor cells by extended in vitro exposure to a pseudotyped retroviral vector

Retroviral-mediated gene transfer is the most attractive modality for gene transfer into hematopoietic stem cells. However, transduction efficiency has been low using amphotropic Moloney murine leukemia virus (MoMLV) vectors. In this study, we investigated modifications of gene transfer using amphotropic MoMLV vectors in cell-free supernatant for their ability to increase the currently low transduction of both committed hematopoietic progenitors, granulocyte-macrophage colony-forming units (CFU-GMs), and their precursors, long-term culture-initiating cells (LTC-IC). First, based on the observation that bone marrow cells express more gibbon ape leukemia virus (GALV) receptor (Glvr-1) than amphotropic receptor (Ram-1), PG13/LN, which is a MoMLV vector pseudotyped with the GALV envelope, was compared with the analogous amphotropic envelope vector (PA317/LN). Second, progenitor cell transduction efficiency was compared between CD34 enriched and nonenriched progenitor populations. Third, the duration of transduction in vitro was extended to increase the proportion of progenitor cells that entered cell cycle and could thereby integrate vector cDNA. In 20 experiments, 1 x 10(6) marrow or peripheral blood mononuclear cells (PBMCs)/mL were exposed to identical titers of pseudotyped PG13/LN vector or PA317/LN vector in the presence of recombinant human interleukin-1 (IL-1), IL-3, IL-6, and stem cell factor (SCF; c-kit ligand) for 5 days. 50% of fresh vector supernatant was refed daily. Hematopoietic progenitor cells as measured by G418-resistant granulomonocytic colony (CFU-GM) formation were transduced more effectively with PG13/LN (19.35%) than with PA317/LN (11.5%, P = .012). In 11 further experiments, enrichment of CD34 antigen positive cells significantly improved gene transfer from 13.9% G418-resistant CFU-GM in nonenriched to 24.9% in CD34-enriched progenitor cells (P < .01). To analyze gene transfer after extended growth factor-supported long-term culture, 1 x 10(6) marrow cells/mL were cultured with IL-1, IL-3, IL-6, and SCF (50 ng/mL each) for 1, 2, and 3 weeks. Fifty percent of PG13/LN supernatant with growth factors was refed on 5 days per week. Five percent of marrow CFU-GM and 67% of LTC-IC were G418 resistant at 1 week (n = 4), 60% of CFU-GM and 100% of LTC-IC were resistant at 2 weeks (n = 2) and 74% of CFU-GM (n = 4) and 82% of LTC-IC (n = 2) were resistant at three weeks.(ABSTRACT TRUNCATED AT 400 WORDS)

Frequency distribution of cytomegalovirus envelope glycoprotein genotypes in bone marrow transplant recipients

Using restriction analysis of polymerase chain reaction (PCR)-amplified DNA, the cytomegalovirus (CMV) envelope glycoprotein (gB and gH) genotypes were determined for virus isolates from 128 bone marrow transplant recipients with fatal or nonfatal CMV. All isolates could be assigned to one of four gB and gH genotypes previously identified by DNA sequencing studies. Isolates of gB type 1 were more commonly found to be of gH type 2, whereas gB types 2-4 were more commonly linked to gH type 1. A small frequency of recombination with gB was detected by restriction analysis of DNA from variable regions of the gp55 and gp116 domains. Multiple isolates from various sites of 29 patients were typed and, with three exceptions, the gB genotype remained constant in all isolates from a single patient. Patients who survived CMV infection more commonly shed virus of gB type 1 than those who died (P = .003). This significant difference of gB types among patient subsets is unexplained but raises the possibility that gB genotypes may serve as a marker for pathogenicity of CMV strains in marrow transplant patients.

An evaluation of antioxidant effects on recovery from postischemic acute renal failure

Xanthine oxidase (XO) activity and hydroxyl radical (.OH) formation are widely proposed mediators of renal reperfusion injury, potentially altering the severity of, and recovery from, postischemic acute renal failure. The goal of this study was to ascertain whether combination XO inhibitor (oxypurinol) and .OH scavenger (Na benzoate) therapy, given at the time of renal ischemia, alters the extent of: (1) tubular necrosis and filtration failure; (2) DNA fragmentation/apoptosis (assessed in situ by terminal deoxynucleotidyl transferase reactivity); (3) early tubular regenerative responses (proliferating cell nuclear antigen expression; (3H)thymidine incorporation); and (4) the rate and/or degree of functional and morphologic repair. The effects of XO inhibition, .OH scavengers, and "catalytic" iron (FeSO4) on human proximal tubular cell proliferation in vitro were also assessed with a newly established cell line (HK-2). Male Sprague-Dawley rats were subjected to 35 min of bilateral renal arterial occlusion with or without oxypurinol/benzoate therapy. These agents did not alter the extent of tubular necrosis or filtration failure, proliferating cell nuclear antigen expression or thymidine incorporation, or the rate/extent of renal functional/morphologic repair. DNA fragmentation did not precede tubular necrosis, and it was unaffected by antioxidant therapy. By 5 days postischemia, both treatment groups demonstrated regenerating epithelial fronds that protruded into the lumina. These structures contained terminal deoxynucleotidyl transferase-reactive, but morphologically intact, cells, suggesting the presence of apoptosis. Oxypurinol and .OH scavengers (benzoate; dimethylthiourea) suppressed in vitro tubular cell proliferation; conversely, catalytic Fe had a growth-stimulatory effect. These results suggest that: (1) XO inhibition/.OH scavenger therapy has no discernible net effect on postischemic acute renal failure; (2) DNA fragmentation does not precede tubular necrosis, suggesting that it is not a primary mediator of ischemic cell death; and (3) antioxidants can be antiproliferative for human tubular cells, possibly mitigating their potential beneficial effects.

HK-2: an immortalized proximal tubule epithelial cell line from normal adult human kidney

Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.

Declining lymphocyte counts following cytomegalovirus (CMV) infection are associated with fatal CMV disease in bone marrow transplant patients

A previous pilot study conducted on 12 bone marrow transplant recipients suggested that detection of cytomegalovirus (CMV) in lymphocytes was associated with a drop in lymphocyte counts and death due to CMV disease. To test the association between decreasing lymphocytes and CMV-related death, we undertook a retrospective study of 332 CMV-infected patients transplanted between 1987 and 1990. The patients were divided into three groups: I = 170 patients who survived their infection and were alive at the time of the study; II = 103 patients who died of causes other than CMV infection; and III = 59 patients who died of CMV disease. Lymphocyte counts were analyzed during a 24-day period, starting 10 days before the day of first positive CMV culture (day 0). Lymphocyte counts were significantly lower in Group III from day 0 through day +14 (p < .001 vs. group I; and p = .002 vs. group II). Multivariate statistical analysis was used to adjust for other differences between the groups that might influence lymphocyte numbers. Average lymphocyte counts in patients who died of CMV disease decreased by an average of 35% after day 0. The differences in lymphocyte counts remained independent of the effects of acute graft-vs.-host disease (GVHD), time since transplant, transplant type, and high-dose steroid treatment. In summary, these data suggest that in some patients a drop in lymphocyte counts is a consequence of CMV infection associated with fatal CMV disease. Whether this can be attributed to direct infection of lymphocytes, a defective immune response, or some other mechanism remains to be determined.

Expression of CD7 on normal human myeloid progenitors

Existence of biphenotypic leukemias co-expressing CD7 and CD34 has prompted the question of whether a similar population of cells is present in normal human bone marrow. As CD7 is considered to be a T cell-restricted Ag, the co-expression of CD7 with the "human stem cell Ag" CD34 may identify a bipotent stage within hemopoietic differentiation. Cells with this phenotype have previously been isolated from human thymus. In this report we provide evidence that human marrow mononuclear cells also contain a minor subpopulation of cells co-expressing CD7 and CD34. The CD7+/CD34+ cells were found to contain committed myeloid progenitors assayed both as CFU in semi-solid media and by their ability to produce granulocytes in long term marrow cultures. Expression of CD7 on myeloid committed progenitors was further confirmed in a C-mediated cytotoxic assay. We conclude that CD7 expression is not restricted to T cells but is also expressed during early stages of myeloid differentiation.