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I McNiece

Publications and source records attributed to I McNiece.

At least 19 recordsLinked to original sources
PubMed2006

Ex vivo expansion of mafosfamide-purged PBPC products.

BACKGROUND: Multiple studies have demonstrated that 'purging' of autografts with 4-hydroperoxycyclophosphamide (4HC) or the related compound mafosfamide (Mf), to eradicate residual leukemia, produces the best results associated with autologous blood and marrow transplantation for AML. However, 4HC purging results in prolonged aplasia. Therefore, we evaluated the potential of ex vivo expansion of Mf-treated CD34+ cells from mobilized PBPC. METHODS: CD34+ cells were isolated from PBPC products and treated with 30 microg/mL Mf. The Mf-treated CD34+ cells were washed and cultured for 14 days in StemLine II-defined media containing recombinant human (rh) SCF, G-CSF and thrombopoietin (Tpo). RESULTS: Treatment with Mf resulted in 90% killing of progenitor cells (GM-CFC) but maintenance of SCID-repopulating cells (SRC). Ex vivo culture of the Mf-treated CD34+ cells resulted in decreased cell numbers (10-20% of the starting cell dose) during the first week. Nevertheless, in the second week of culture the total cell numbers expanded to approximately 20-fold above starting cell numbers and progenitor cells returned to approximately pre-treatment levels. DISCUSSION: These studies demonstrate the potential of ex vivo culture to expand both total cell numbers and progenitor cells following treatment of PBPC CD34+ cells with Mf. Clinical studies are currently being initiated to evaluate the engraftment potential of these purged and expanded products.

Adjuvants, Immunologic↗
PubMed2004

Ex vivo expansion of cord blood mononuclear cells on mesenchymal stem cells.

BACKGROUND: Cord blood (CB) cells are being used increasingly as a source of hematopoietic cells to support high dose chemotherapy. However, CB units contain low numbers of cells, including CD34+ cells, and thus their use is associated with significant delays in engraftment of neutrophils and platelets. Exvivo expansion of CB has been proposed to increase the numbers of cells available. We and others have reported the requirement of CD34 selection for optimal expansion of CB products'; however, the selection of frozen CB products in clinical trials results in significant loss of CD34+ cells, with a median recovery of 50, but less than 40% recovery in more than one-third of products. In the present studies we evaluated the potential of mesenchymal stem cells (MSC) to support ex vivo expansion of unselected CB products. METHODS: Mononuclear cells (MNC) from CB products were isolated and cultured on preformed MSC layers in T150 flasks containing 50 mL Stemline II media plus hematopoietic growth factors. Various culture conditions were compared for optimal expansion of the CB MNC. RESULTS: Ex vivo expansion of CB MNC on MSC resulted in 10- to 20-fold expansion of total nucleated cells, seven- to 18-fold expansion of committed progenitor cells, two- to five-fold expansion of primitive progenitor cells and 16- to 37-fold expansion of CD34+ cells. DISCUSSION: These studies demonstrated significant expansion of CB products without CD34 cell selection using culture conditions that are clinically applicable. Our current focus is to initiate clinical trials to evaluate the in vivo potential of CB cells expanded with these conditions.

Antigens, CD34↗
PubMed2001

Ex vivo expansion of hematopoietic progenitor cells and mature cells.

Hematopoietic cells have the potential for providing benefit in a variety of clinical settings. These include cells for support of patients undergoing high-dose chemotherapy, as a target for replacement gene therapy, and as a source of cells for immunotherapy. The limitation to many of these applications has been the total absolute number of defined target cells. Therefore many investigators have explored methods to culture hematopoietic cells in vitro to increase the numbers of these cells. Studies attempting to expand hematopoietic stem cells, progenitor cells, and mature cells in vitro have become possible over the past decade due to the availability of recombinant growth factors and cell selection technologies. To date, no studies have demonstrated convincing data on the expansion of true stem cells, and so the focus of this review is the expansion of committed progenitor cells and mature cells. A number of clinical studies have been preformed using a variety of culture conditions, and several studies are currently in progress that explore the use of ex vivo expanded cells. These studies will be discussed in this review. There are evolving data that suggest that there are real clinical benefits associated with the use of the expanded cells; however, we are still at the early stages of understanding how to optimally culture different cell populations. The next decade should determine what culture conditions and what cell populations are needed for a range of clinical applications.

Animals↗
PubMed2000

Ex vivo expanded peripheral blood progenitor cells provide rapid neutrophil recovery after high-dose chemotherapy in patients with breast cancer.

Ex vivo expanded peripheral blood progenitor cells (PBPCs) have been proposed as a source of hematopoietic support to decrease or eliminate the period of neutropenia after high-dose chemotherapy. CD34 cells were selected from rhG-CSF mobilized PBPCs from patients with breast cancer and were cultured for 10 days in defined media containing 100 ng/mL each of rhSCF, rhG-CSF, and PEG-rhMGDF in 1 L Teflon bags at 20 000 cells/mL. After culture the cells were washed and reinfused on day 0 of transplantation. On day +1, cohort 1 patients (n = 10) also received an unexpanded CD34-selected PBPC product. These patients engrafted neutrophils (absolute neutrophil count, >500/microL) in a median of 6 (range, 5-14) days. Cohort 2 patients (n = 11), who received expanded PBPCs only, engrafted neutrophils in a median of 8 (range, 4-16) days. In comparison, the median time to neutrophil engraftment in a historical control group of patients (n = 100) was 9 days (range, 7-30 days). All surviving patients are now past the 15-month posttransplantation stage with no evidence of late graft failure. The total number of nucleated cells harvested after expansion culture was shown to be the best predictor of time to neutrophil engraftment, with all patients receiving more than 4 x 10(7) cells/kg, engrafting neutrophils by day 8. No significant effect on platelet recovery was observed in any patient. These data demonstrate that PBPCs expanded under the conditions defined can shorten the time to engraftment of neutrophils compared with historical controls and that the rate of engraftment is related to the dose of expanded cells transplanted.

Antigens, CD↗
PubMed2000

Increased expansion and differentiation of cord blood products using a two-step expansion culture.

OBJECTIVE: [corrected] The use of allogeneic cord blood (CB) products as a source of cellular support for patients receiving high-dose chemotherapy has been limited primarily to smaller children due to the low numbers of cells in a CB unit. Ex vivo expansion of CB cells has been proposed as a method to increase the number of cells available for transplantation. Following high-dose chemotherapy administration, we transplanted adult patients with CB expanded in static culture for 10 days, in DM containing stem cell factor (SCF), granulocyte colony-stimulating factor (G-CSF), and megakaryocyte growth and development factor (MGDF). Patients achieved neutrophil engraftment in a median of 26 days (range 15 to 45). In an attempt to hasten the time to neutrophil engraftment, we developed a two-step culture system that results in increased expansion of total nucleated cells and further maturation of neutrophil precursors. MATERIALS AND METHODS: CD34(+) cells isolated from CB products were cultured for 7 days at 37 degrees C in 100-mL Teflon culture bags containing 50 mL of DM containing SCF, G-CSF, and MGDF (100 ng/mL). The cells were harvested from these bags after 7 days of incubation at 37 degrees C and transferred to 1-L Teflon bags containing 1 L of DM plus SCF, G-CSF, and MGDF. After a second culture period of 7 days, the cells were harvested, washed, and assayed for mature (granulocyte-macrophage colony-forming cells [GM-CFC]) and primitive progenitor cells (high proliferative potential colony-forming cells [HPP-CFC]). RESULTS: The two-step cultures resulted in a median total nucleated cell expansion of 438-fold (range 286 to 952, N = 11); the original one-step cultures resulted in a median expansion of 98-fold (range 59 to 350, N = 5). Equivalent expansion of committed progenitor cells (GM-CFC) and primitive progenitor cells (HPP-CFC) was obtained. CD34(+) cells were expanded a median of 29-fold in the two-step cultures (N = 11). The two-step culture contained more mature neutrophil cells, by morphologic examination, than the one-step cultures, similar to ex vivo expanded peripheral blood progenitor cells (PBPC). CONCLUSION: The two-step ex vivo expansion conditions described for CB resulted in increased numbers of total nucleated cells, GM-CFC, HPP-CFC, and CD34(+) cells and morphologically resembled ex vivo expanded PBPC, which have been shown to provide more rapid neutrophil engraftment than unexpanded PBPC. We propose that the availability of increased numbers of expanded CB cells may result in more rapid engraftment of neutrophils following infusion to transplant recipients.

Antigens, CD34↗
PubMed2000

Highly purified CD34+ cells isolated using magnetically activated cell selection provide rapid engraftment following high-dose chemotherapy in breast cancer patients.

The primary objective of this study was to evaluate the safety of infusion of CD34+ cells, selected using a clinical scale magnetically activated cell sorting device, assessed by time to hematological engraftment and incidence of adverse events. Secondary objectives included evaluation of device performance in terms of purity and recovery of the CD34+ cell product. Breast cancer patients suitable for transplantation received cyclophosphamide and filgrastim for mobilisation, followed by three leukaphereses. The products of the first two leukaphereses underwent CD34+ cell selection. The product of the third leukapheresis was cryopreserved unmanipulated. Following high-dose cyclophosphamide, thiotepa and carboplatin, selected CD34+ cells were infused. In 54 patients who received selected cells only, the median time to platelet recovery and neutrophil recovery was 11 days (range 5-51) and 9 days (range 5-51), respectively. There were no adverse events associated with infusion of selected cells. A total of 126 leukapheresis samples was available before and after selection for central CD34+ analysis. The median purity was 96.1% (27.4-99.4) and the median recovery was 52. 3% (15.2-146.3). These data show that cells selected using magnetically activated cell selection provide safe and rapid engraftment after high-dose therapy. Bone Marrow Transplantation (2000) 25, 243-249.

Adolescent↗
PubMed1999

Ex-vivo expansion of hematopoietic progenitor cells: preliminary results in breast cancer.

Ex-vivo expanded progenitor cells have been proposed as a source of cells to support high-dose chemotherapy and to decrease or eliminate the period of neutropenia following transplantation. To date, no clinical studies using ex vivo expanded cells, have demonstrated any decrease in the time to neutrophil or platelet recovery, although a number of clinical studies have been performed using a variety of growth factor cocktails and culture conditions. Over the past 6 years we have developed a static culture system that results in optimal expansion of myeloid progenitor cells. We have initiated a clinical study to evaluate this culture system in breast cancer patients receiving peripheral blood progenitor cells (PBPC) to support high-dose chemotherapy. CD34 selected cells were cultured for 10 days in 800 ml of defined media (Amgen Inc.) containing 100 ng/ml each of rhSCF, rhG-CSF and rhMGDF in 1L teflon bags (American Fluoroseal) at 20,000 to 50,000 cells per ml. After culture the cells were washed with 3 volumes of PBS to remove all media and growth factors and reinfused on day 0 of transplant followed by daily administration of rhG-CSF. On day +1 the patients received an unexpanded PBPC product to ensure the durability of the graft. Patients transplanted with expanded PBPC cells recovered neutrophil counts (ANC > 500/microl) as early as day 4 post transplant with a median of 6 days (range 4 to 14 days). In comparison, our historical control group of patients (N=175) had a median time to neutrophil engraftment of 9 days (range 7 to 24 days). A second cohort of patients were transplanted with expanded cells alone and a similar rapid engraftment was obtained. The first patients are now over 70 days post transplant with durable engraftment. No effect on platelet recovery has been observed in any patients to date. These data demonstrate that PBPC expanded under the conditions defined can significantly shorten the time to engraftment of neutrophils.

Breast Neoplasms↗
PubMed1999

A new form of Filgrastim with sustained duration in vivo and enhanced ability to mobilize PBPC in both mice and humans.

Granulocyte colony-stimulating factor (G-CSF) has proven effective in the prophylaxis of chemotherapy-induced neutropenia and as a mobilizer of peripheral blood progenitor cells. The longevity of G-CSF action is limited by its removal from the body by two mechanisms. The first is thought to be mediated via receptors (receptor mediated clearance [RMC]) predominantly on neutrophils, the second process is likely the result of renal clearance. With the intention of developing a novel form of Filgrastim (r-met HuG-CSF) with a sustained duration of action in vivo, a new derivative named SD/01 has been made by association of Filgrastim with poly(ethylene glycol). The desired properties of this new agent would include a prolonged duration of action sufficient to cover a complete single course of chemotherapy. SD/01 is shown here to sustain significantly elevated neutrophil counts in hematopoietically normal mice for 5 days. In neutropenic mice effects were noted for at least 9 days, accompanying a significant reduction in the duration of chemotherapy induced neutropenia. Normal human volunteers showed higher than baseline ANC for around 9 to 10 days after a single injection of SD/01. Data from these normal volunteers also indicate that mobilization of CD34+ cells and progenitors may occur in a more timely manner and to around the same absolute numbers as with repeated daily injections of unmodified Filgrastim. These data indicate that SD/01 represents an efficacious novel form of Filgrastim with actions sustained for between one and two weeks from a single injection.

Animals↗
PubMed1998

Minimization of CD34+ cell enumeration variability using the ProCOUNT standardized methodology.

The dose of cells expressing the surface antigen CD34 (CD34+) has been shown to be a reliable predictor of the time to engraftment following transplantation of PBPC to support high-dose chemotherapy. However, evaluation of rare cells is complicated by a number of factors, including the variability in operator and technical procedures. Recently, Becton Dickinson Immunocytometry Systems introduced a new CD34+ cell analysis system, the ProCOUNT cell enumeration kit, which automates the analysis of CD34+ cells and minimizes the variabilities of this procedure. We have evaluated the ProCOUNT system in comparison to a standard CD34 cell analysis (based on the Milan approach) using leukapheresis products from patients and normal donors mobilized with chemotherapy plus recombinant human G-CSF (rhG-CSF) or with rhG-CSF alone. In addition, we compared these analyses using CD34+ cell-selected mobilized leukapheresis products with purities of 75% or greater. The standard CD34 cell analysis methodology quantitated the frequency of cells identified as CD45+, low side scatter, and CD34+. A high correlation coefficient was obtained between the ProCOUNT methodology and the standard CD34 cell analysis methodology for cells obtained from leukapheresis products mobilized with chemotherapy plus rhG-CSF (r = 0.98), rhG-CSF alone (r = 0.96), and CD34+-selected mobilized leukapheresis products (r = 0.83). A comparison was also made between technicians using both analysis methods. Whereas the correlation coefficient between two technicians using the standard methodology was r = 0.77, the correlation coefficient was much higher when using ProCOUNT (r = 0.99). These data demonstrate that the use of ProCOUNT is associated with less variability between data analyzed by different operators. Also, ProCOUNT is consistent with existing CD34+ cellular analysis methodologies. An additional advantage is the ability to determine the absolute concentration of CD34+ cells, thereby allowing calculation of total CD34+ cell numbers without using WBC counts, which also have inherent errors. The ProCOUNT system provides an automated analysis procedure that minimizes the variables in CD34+ cell analysis and may be useful for standardization of methodology between laboratories.

Antigens, CD34↗
PubMed1997

Engraftment and development of human CD34(+)-enriched cells from umbilical cord blood in NOD/LtSz-scid/scid mice.

Understanding the repopulating characteristics of human hematopoietic stem/progenitor cell fractions is crucial for predicting their performance after transplant into high-risk patients following high-dose therapy. We report that human umbilical cord blood cells, 78% to 100% of which express the hematopoietic progenitor cell surface marker CD34, can consistently engraft, develop, and proliferate in the hematopoietic tissues of sublethally irradiated NOD/LtSz-scid/scid mice. Engraftment and development of CD34+ cells is not dependent on human growth factor support. CD34+ cells home to the mouse bone marrow (BM) that becomes the primary site of human hematopoietic development containing myeloid, lymphoid, erythroid, and CD34+ progenitor populations. Myeloid, and in particular lymphoid cells possessing more mature cell surface markers, comprise the human component of mouse spleen and peripheral blood, indicating that development proceeds from primary hematopoietic sites to the periphery. Repopulation of secondary recipients with human cells by BM from primary recipients demonstrates the maintenance of substantial proliferation capacity of the input precursor population. These data suggest that the cells capable of initiating human cell engraftment (SCID-repopulating cells) are contained in the CD34+ cell fraction, and that this mouse model will be useful for assaying the developmental potential of other rare human hematopoietic cell fractions in vivo.

Animals↗
PubMed1997

Flt-3 ligand synergizes with granulocyte colony-stimulating factor to increase neutrophil numbers and to mobilize peripheral blood stem cells with long-term repopulating potential.

Flt-3 ligand (FL) shares many features with stem cell factor (SCF), a widely documented cofactor for peripheral blood progenitor cell (PBPC) mobilization. We investigated the mobilization of PBPCs by FL in combination with granulocyte colony-stimulating factor (G-CSF). As a single agent, FL was a relatively modest mobilizer of PBPCs, resulting in 360 granulocyte/macrophage colony-forming cells (GM-CFCs)/mL blood (control, 155 GM-CFCs/mL blood) and no advantage in leukocyte recovery when these PBPCs were transplanted to irradiated recipient mice. G-CSF, on the other hand, mobilized over 20,000 GM-CFCs/mL blood, and the combination of G-CSF + FL resulted in over 100,000 GM-CFCs/mL blood. The combination of G-CSF + FL stimulated increased levels of monocytes and basophils in the peripheral blood. The performance of the mobilized PBPC product in irradiated hosts correlated with progenitor numbers resulting in long-term engraftment in association with accelerated short-term recovery of both leukocytes and platelets. These data demonstrate the potential of FL to synergize with G-CSF to mobilize PBPCs with both short- and long-term engraftment potential. The effect is similar to the synergistic interaction of G-CSF and SCF on PBPC mobilization. The use of FL as opposed to SCF may elicit a different spectrum of toxicities including lymphoid proliferation effects, in contrast to the mast cell degranulation effects of SCF. Clinical studies of FL are needed to evaluate its usefulness in man.

Animals↗
PubMed1997

Recombinant methionyl human stem cell factor and filgrastim for peripheral blood progenitor cell mobilization and transplantation in non-Hodgkin's lymphoma patients--results of a phase I/II trial.

To examine the safety and efficacy of recombinant-methionyl human stem cell factor (r-metHuSCF), 38 patients with intermediate-grade or immunoblastic high-grade non-Hodgkin's lymphoma who were eligible for autologous transplantation were randomized to receive r-metHuSCF (5, 10, 15, or 20 microg/kg/d) plus Filgrastim (10 microg/kg/d) or Filgrastim (10 microg/kg/d) alone to mobilize peripheral blood progenitor cells. Subcutaneous administration of r-metHuSCF was well tolerated in conjunction with a multi-agent pre-medication regimen; local injection site reactions were the most commonly seen adverse event. The total mononuclear cell count, CD34+ cell content, granulocyte-macrophage colony-forming cells (GM-CFC), and burst-forming units-erythroid (BFU-E) per kilogram in the apheresis product was similar when all patients were analyzed by treatment cohort and mobilization regimen (Filgrastim or r-metHuSCF in combination with Filgrastim); however, when prior chemotherapy was taken into account in a supplementary analysis, clinically important differences were observed. Extensive prior therapy was defined as the amount of exposure to specific stem cell toxic chemotherapeutic agents that patients received. These agents include procarbazine, nitrogen mustard, melphalan, nitrosoureas (> or = 2 cycles of any of these drugs) or greater than 7.5 g of cytosine arabinoside. In these patients, there was an increased number of CD34+ cells (1.76 v 0.28 x 10(6)/kg), GM-CFC (20.5 v 5.0 x 10(4)/kg), and BFU-E (36.9 v 8.9 x 10(4)/kg) in patients receiving r-metHuSCF and Filgrastim (N = 18) compared with Filgrastim alone (N = 5). These patients also had a decreased time to an untransfused platelet count of 20 x 10(9)/L that was 10.5 days shorter in the patients who received r-metHuSCF and Filgrastim (12.5 v 23 days). These differences were not found to be statistically significant, possibly because of small size, but are clinically important.

Adult↗
PubMed1997

An analysis of the effects of combined treatment with rmGM-CSF and PEG-rHuMGDF in murine bone marrow transplant recipients.

We have studied the potential of combination growth factor treatment with GM-CSF and megakaryocyte growth and development factor (MGDF) to stimulate hematopoietic recovery in mice following bone marrow transplantation. More rapid recovery of neutrophils occurred in mice treated with recombinant murine (rm)GM-CSF plus pegylated recombinant human (PEG-rHu)MGDF than carrier treated controls, however this recovery was equivalent to the effect of treatment with rmGM-CSF alone. PEG-rHuMGDF stimulated a more rapid recovery of platelets with no effect on neutrophil recovery. At the two tested doses of rmGM-CSF (72 and 200 microg/kg/day) the platelet recovery was inferior to that in carrier treated mice. Also, the addition of rmGM-CSF to PEG-rHuMGDF had a dose-related negative impact on platelet recovery compared to PEG-rHuMGDF alone. These data suggest that the use of combination therapy in some clinical indications may lead to unexpected results. Furthermore, careful dosage studies may be necessary to identify the full potential of combined growth factors to obtain additive or synergistic effects on multilineage hematopoietic reconstitution in vivo.

Animals↗
PubMed1997

Large-scale isolation of CD34+ cells using the Amgen cell selection device results in high levels of purity and recovery.

The Amgen Cell Selection Device (ACSD) is a fully automated system based on the research scale magnetic-activated cell separation (MACS) system (Miltenyi Biotech GmbH, Bergisch Gladbach, Germany) for the selection of CD34+ cells. Leukapheresis products (LP) (n = 30) from normal donors mobilized with recombinant human granulocyte colony-stimulating factor (rhG-CSF) were selected with the ACSD to evaluate the performance of this system. The starting LP contained a median of 0.51% CD34+ cells (range 0.21%-1.54%) and a median WBC count of 3.0 x 10(10) (range 1-4.7 x 10(10) cells). After selection on the ACSD a mean purity of 91.5% +/- 0.6% CD34+ cells was obtained, with a median purity of 95.5% CD34+ cells. A median of 98 x 10(6) total CD34+ cells were recovered postselection, with a range of 31-323 x 10(6) cells collected from the LP. This represented a mean recovery of 81.7% +/- 6% of CD34+ cells and a median of 78% compared with starting CD34+ cell numbers in the LP. FACS analysis of the selected products demonstrated a 4-5 log depletion of T cell subsets, including CD3, CD4, CD8, and CD56 subsets. These data demonstrate the high performance obtained with the ACSD resulting in a final product of greater than 90% purity of CD34+ cells. CD34+ cells selected with the ACSD represent an ideal product for clinical applications, such as tumor cell purging, T cell depletion for allogeneic transplant, ex vivo expansion, and gene therapy.

Antigens, CD↗
PubMed1997

Ex vivo expansion of megakaryocyte progenitors: effect of various growth factor combinations on CD34+ progenitor cells from bone marrow and G-CSF-mobilized peripheral blood.

Prolonged thrombocytopenia resulting from inadequate megakaryocyte (MK) progenitor cell reconstitution is a serious complication of hematopoietic cell-supported high-dose chemotherapy (HDC). In this situation, the infusion of MK progenitors that are expanded ex vivo could be clinically beneficial. In this study we investigated the ability of various growth factor combinations to generate MK progenitors. CD34+ cells derived from bone marrow (BM) and granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood (PB) from 17 patients with breast cancer, lymphoma, or myeloma were cultured unpertubed for 10 days in a serum-free liquid culture system that contained recombinant growth factors. Five different growth factors combinations were evaluated: Stem cell factor (SCF), interleukin (IL)-3, IL-6 + G-CSF (combination 1); SCF, megakaryocyte growth and development factor (MGDF) + G-CSF (combination 2); SCF + MGDF (combination 3); MGDF alone (combination 4); and SCF, IL-3, IL-6, G-CSF + MGDF (combination 5). PB CD34+ cells yielded significantly higher numbers of CD41+ MK progenitors than BM CD34+ cells with any of the growth factor regimens assayed. PB CD34+ cells (2x10[5]) at day 0 generated 1.2 to 1.3x10(6) CD41+ cells by day 10 when cultured in the presence of growth factor combinations 1, 2, or 3. In contrast, 2x10(5) BM CD34+ cells produced 5x10(5) CD41+ cells after 9 days in the presence of combination 1, whereas lower numbers of CD41+ cells were generated in cultures with combinations 2 and 3 (2.3x10[5] and 4.2x10[4], respectively). The addition of MGDF to cultures that were grown with combination 1 for 5 days increased the number of CD41+ cells (1.7-fold increase in PB-derived cultures, 1.6-fold increase in BM-derived cultures). Treatment with MGDF alone resulted in higher frequencies of MK progenitors than those obtained in cultures with combined growth factors (79% in PB-derived cultures, 25% in BM-derived cultures), but because total cell growth was attenuated, absolute numbers of MK progenitors were lower (7x10(5) in PB-derived cultures, 7x10(4) in BM). Morphological analysis of immunocytochemically identified megakaryocytic cells revealed mononuclear cells as the predominant cell type in all of the cultures. During the 10-day culture period, PB-derived MK progenitors did not show notable maturation, even under the influence of MGDF, whereas in BM-derived cultures MGDF induced a significant shift to binuclear cells and stage I MK after day 5. Phenotypic analysis of cell surface markers showed that the majority of cultured megakaryocytic cells coexpressed CD34 and platelet glycoproteins (GPs), also indicating an immature stage of development. The ex vivo proliferative activity of CD34+ cells and their potential to develop into the megakaryocytic lineage demonstrated considerably high interpatient variations. There was no correlation between platelet recovery following HDC with hematopoietic cell support and the magnitude of GP+ cell expansion ex vivo, suggesting the feasibilty of MK expansion ex vivo in patients with prolonged thrombocytopenia posttransplantation. In summary, these data indicate that GCSF-mobilized CD34+ PBPCs are more effectively expanded ex vivo into the megakaryocytic lineage than are CD34+ BMPCs. CD34+/GP+ MK progenitors may be an appropiate cell population for transplantion as prophylaxis or treatment of prolonged thrombocytopenia. The efficacy of this procedure will be tested prospectively in a clinical trial.

Adult↗
PubMed1997

Multilineage engraftment in NOD/LtSz-scid/scid mice from mobilized human CD34+ peripheral blood progenitor cells.

Peripheral blood progenitor cells (PBPCs) are now the most widely used source for hematopoietic support of patients in the autologous transplant setting and are increasingly being used for allogeneic transplantation. A reliable model to characterize the in vivo potential of various PBPC subpopulations could be valuable as a preclinical assay to predict the hematopoietic performance in humans of these populations and of products resulting from their manipulations ex vivo. We have used immunocompromised nonobese diabetic/LtSz-scid/scid (NOD/SCID) mice to engraft human CD34+ PBPCs and to study the repopulation characteristics of this progenitor cell fraction. Following myeloablation, intravenous infusion of CD34+ cells consistently produced engraftment and development in mice. Multilineage development occurred in all mice with CD34+ cells, erythroid precursors, and the most immature populations of myeloid cells and B lymphocytes restricted to the mouse bone marrow (BM). More mature populations of myeloid cells and B lymphocytes were peripheralized to the spleen and blood of the animals. This finding suggests that human hematopoiesis in the mice may recapitulate hematopoietic recovery in humans. The provision of human growth factors was not necessary for either engraftment or development of CD34+ cells. When mice were supplemented with growth factors, engraftment levels were unaffected but development was biased toward myeloid production. These findings indicate that providing nonphysiological levels of human growth factors may obscure or enhance the developmental potential of particular progenitor cell populations in this model. Cells capable of initiating colony formation in vitro were maintained in BM during the engraftment period (up to 17 weeks), suggesting that continuous production of myeloid and erythroid precursors occurred from more primitive hematopoietic cells subsequent to engraftment. In comparing results from this study with previous results, it was found that in this model the engraftment potential of CD34+ umbilical cord blood cells is greater than that described here for CD34+ PBPCs. In summary, this model may provide a reliable assay to predict the hematopoietic potential of progenitor cell populations in humans if a correlation for engraftment of identical cell fractions can be established between the two species.

Animals↗
PubMed1996

CD34-deficient mice have reduced eosinophil accumulation after allergen exposure and show a novel crossreactive 90-kD protein.

CD34 is expressed on the surface of hematopoietic stem/progenitor cells, stromal cells, and on the surface of high-endothelial venules (HEV). CD34 binds L-selectin, an adhesion molecule important for leukocyte rolling on venules and lymphocyte homing to peripheral lymph nodes (PLN). We generated CD34-deficient mutant animals through the use of homologous recombination. Wild-type and mutant animals showed no differences in lymphocyte binding to PLN HEV, in leukocyte rolling on venules or homing to PLN, in neutrophil extravasation into peritoneum in response to inflammatory stimulus, nor in delayed type hypersensitivity. Anti-L-selectin monoclonal antibody (MEL-14) also inhibited these immune responses similarly in both CD34-deficient and wild-type mice. However, eosinophil accumulation in the lung after inhalation of a model allergen, ovalbumin, is several-fold lower in mutant mice. We found no abnormalities in hematopoiesis in adult mice and interactions between mutant progenitor cells and a stromal cell line in vitro were normal. No differences existed in the recovery of progenitor cells after 5-fluorouracil treatment, nor in the mobilization of progenitor cells after granulocyte colony-stimulating factor treatment compared with wild-type animals. Surprisingly, although CD34 was not expressed in these mice, a portion of its 90-kD band crossreactive with MECA79 remained after Western blot. Thus, we have identified an additional molecule(s) that might be involved in leukocyte trafficking. These results indicate that CD34 plays an important role in eosinophil trafficking into the lung.

Allergens↗