Comparison of the content and subpopulations of CD3 and CD34 positive cells in bone marrow harvests and G-CSF-mobilized peripheral blood leukapheresis products from healthy adult donors

Prevention of relapse after allogeneic hematopoietic cell transplantation by donor and cell source selection

Allogeneic hematopoietic cell transplantation (HCT) is the most established form of cancer immunotherapy and has been successfully applied for the treatment and cure of otherwise lethal neoplastic blood disorders. Cancer immune surveillance is mediated to a large extent by alloreactive T and natural killer (NK) cells recognizing genetic differences between patient and donor. Profound insights into the biology of these effector cells has been obtained over recent years and used for the development of innovative strategies for intelligent donor selection, aiming for improved graft-versus-leukemia effect without unmanageable graft-versus-host disease. The cellular composition of the stem cell source plays a major role in modulating these effects. This review summarizes the current state-of the-art of donor selection according to HLA, NK alloreactivity and stem cell source.

Bone marrow versus peripheral blood as a graft source for haploidentical donor transplantation in adults using post-transplant cyclophosphamide-A systematic review and meta-analysis

BACKGROUND

Peripheral-blood (PB) and bone marrow (BM) are both widely used in hematopoietic stem cell transplantation (HSCT). However, it is unclear whether PB or BM produces a more satisfactory outcome in haploidentical HSCT, particularly for patients using post-transplant cyclophosphamide (PTCy), which is the standard therapy. However, to date, no meta-analysis focusing on this issue has been published.

METHODS

We systematically searched PubMed, MEDLINE, Web of Science, the Cochrane Library and the ClinicalTrials.gov website for studies regarding the use of BM or PB in haploidentical HSCT for hematological malignancies in adults using PTCy. Data were analyzed using Open Meta-Analyst statistical software.

RESULTS

Fourteen studies were extracted including four comparative retrospective reports and ten single-arm reports, with a total of 1759 patients received PTCy haploidentical HSCT (462 patients received PBSCT, 1297 patients received BMT). The pooled outcomes of comparative retrospective studies showed significantly higher incidence of grade III-IV acute graft-versus-host disease (GVHD) (OR = 1.741, 95%CI 1.032-2.938), incidence of grade IIIV acute GVHD (OR = 1.778, 95%CI 1.314, 2.406) and engraftment rate (OR = 1.843, 95%CI 1.066-3.185) in the PB group. No significant differences were found on the incidence of relapse, 2-year overall survival (OS) and disease-free survival (DFS), acute IIIV GVHD and chronic GVHD between PBSCT or BMT.

CONCLUSION

The efficacy of PB is not inferior to BM for patients undergoing PTCy haploidentical HSCT with regard to primary outcomes, including OS, DFS, NRM and relapse. However, with regards to convenience and pain relief, PB graft is suitable for haploidentical HSCT, but with a higher risk of acute GVHD.

Graft-versus-Host Disease after HLA-Matched Sibling Bone Marrow or Peripheral Blood Stem Cell Transplantation: Comparison of North American Caucasian and Japanese Populations

The risk of acute graft-versus-host disease (GVHD) after HLA-matched sibling bone marrow transplantation (BMT) is lower in Japanese than in Caucasian patients. However, race may have differential effect on GVHD dependent on the graft source. North American Caucasian and Japanese patients receiving their first allogeneic BMT or peripheral blood stem cell transplantation from an HLA-matched sibling for leukemia were eligible. BMT was performed in 13% of the Caucasian patients and in 53% of the Japanese patients. On multivariate analysis, the interaction term between race and graft source was not significant in any of the models, indicating that graft source does not affect the impact of race on outcomes. The risk of grade III or IV acute GVHD was significantly lower in the Japanese patients compared with the Caucasian patients (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.57 to 0.96), which resulted in lower risk of nonrelapse mortality in the Japanese patients (HR, 0.69; 95% CI, 0.54 to 0.89). The risk of relapse was also lower in this group. The lower risks of nonrelapse mortality and relapse resulted in lower overall mortality rates among the Japanese patients. In conclusion, our data indicate that irrespective of graft source, the risk of severe acute GVHD is lower in Japanese patients, resulting in a lower risk of nonrelapse mortality.

G-CSF-primed bone marrow as a source of stem cells for allografting: revisiting the concept

The source of hematopoietic stem cells (HSCs) for allogeneic transplantation has evolved over the last decades, from the sole use of unstimulated bone marrow (BM) to the use of G-CSF (filgrastim)-mobilized peripheral blood, G-CSF-primed BM (G-BM) and cord blood. G-CSF-mobilized PBSC has replaced BM as the most commonly used source of allogeneic stem cells. G-BM is a source of HSCs, with studies demonstrating the safety and feasibility of this strategy with the potential for reducing GvHD, while retaining the speed of engraftment. Although the G-BM had lost its use as the optimal source of stem cells, after the widespread use of haploidentical transplantation, their use has resurfaced in 2010. This source can still be used in today's world of transplantation in aplastic anemia and other benign diseases, as well as in children donors. This study intends to review the evidence for this approach and whether this approach still has merit in the ever-evolving field of allogenic HSC transplantation. The merit of G-BM is its ability to offer speed of engraftment with reduced GvHD.

Dual roles of autologous CD8+ T cells in hematopoietic progenitor cell mobilization and engraftment

BACKGROUND

Poor marrow cellularity alone cannot explain poor hematopoietic progenitor cell (HPC) mobilization. This study assessed the role of CD8+ T cells in HPC cell mobilization and engraftment.

STUDY DESIGN AND METHODS

Mobilization and engraftment were assessed in 192 autologous HPC donors. CD34+, CD4+, and CD8+ T-cell contents in apheresis products were evaluated. Using a chemotaxis assay, we assessed the effect of purified autologous CD8+ T cells from low and high mobilizers on HPC migration from high to low stromal cell-derived factor (SDF-1α) concentration gradients. We also assessed CD8+ T-cell content association with days to neutrophil engraftment.

RESULTS

The median number of CD34+ cells/kg was 4.7 × 10(6) . Patients were categorized according to their total CD34+ cell collection quartile distribution into low, moderate, and high mobilizers. We found that HPC products from low mobilizers contained more CD8+ T cells than HPC products from moderate and high mobilizers. Chemotaxis assays showed depletion of CD8+ T cells enhances HPC mobilization independent of SDF-1α concentration. Neutrophil engraftment analysis showed that the higher the CD8+ T-cell content per unit CD34+ cell, the faster the rate of engraftment.

CONCLUSION

Our findings suggest CD8+ T cells inhibit HPC mobilization and facilitate homing and engraftment.

Peripheral blood hematopoietic stem cells for transplantation of hematological diseases from related, haploidentical donors after reduced-intensity conditioning

In a multicenter collaboration, we carried out T cell-replete, peripheral blood stem cell (PBSC) transplantations from related, HLA-haploidentical donors with reduced-intensity conditioning (RIC) and post-transplantation cyclophosphamide (Cy) as graft-versus-host disease (GVHD) prophylaxis in 55 patients with high-risk hematologic disorders. Patients received 2 doses of Cy 50 mg/kg i.v. on days 3 and 4 after infusion of PBSC (mean, 6.4 × 10(6)/kg CD34(+) cells; mean, 2.0 × 10(8)/kg CD3(+) cells). The median times to neutrophil (500/μL) and platelet (>20,000/μL) recovery were 17 and 21 days respectively. All but 2 of the patients achieved full engraftment. The 1-year cumulative incidences of grade II and grade III acute GVHD were 53% and 8%, respectively. There were no cases of grade IV GVHD. The 2-year cumulative incidence of chronic GHVD was 18%. With a median follow-up of 509 days, overall survival and event-free survival at 2 years were 48% and 51%, respectively. The 2-year cumulative incidences of nonrelapse mortality and relapse were 23% and 28%, respectively. Our results suggest that PBSC can be substituted safely and effectively for bone marrow as the graft source for haploidentical transplantation after RIC.

Impact of conditioning regimen on outcome of 2-year disease-free survivors of autologous stem cell transplantation for Hodgkin lymphoma

BACKGROUND

Autologous stem cell transplantation is the standard of care for patients with relapsed HL and the long-term outcomes for survivors 2 years after ASCT have not been well described. No prospective trials have compared the effect of different conditioning regimens on outcomes.

PATIENTS AND METHODS

We searched the Nebraska Lymphoma Study Group database to identify patients with HL who received ASCT from 1984 to 2007. Patients were conditioned with either CBV (cyclophosphamide, carmustine, and etoposide) or BEAM (carmustine, etoposide, cytarabine, and melphalan).

RESULTS

At a median follow-up of 8 (range, 2-26) years, 225 patients were alive and disease-free 2 years after ASCT. Analysis was limited to these patients. At 5 years, the progression-free survival (PFS) was 92% for BEAM and 73% for CBV (P = .002) and the overall survival (OS) was 95% for BEAM and 87% for CBV (P = .07). At 10 years, the PFS was 79% for BEAM and 59% for CBV (P = .01) and the OS was 84% for BEAM and 66% for CBV (P = .02).

CONCLUSION

Patients with HL who are disease-free and alive 2 years after ASCT have favorable outcomes. We observed lower risk of progression and longer survival associated with use of BEAM vs. CBV. Patients in the BEAM group received a transplant in more recent years so we cannot exclude the possibility that the superior outcomes seen in the BEAM group are because of better supportive care, use of peripheral blood stem cell grafts, or improvements in salvage therapies before transplantation.

[Hematopoietic stem cells mobilization: state of the art in 2011 and perspectives]

High-dose chemotherapy with stem cells support has largely improved in terms of hematopoietic stem and progenitor cells harvest procedures as well as in those, which target or manipulate the cellular composition of autologous graft. Optimal preparative regimens and supportive care had lead to better use of autologous transplantation procedure. For other patients assigned to hematopoietic transplantation, availability of allogeneic donors appears to be an interesting alternative source of hematopoietic stem cells. Since three decades, hematopoietic growth factors development has allowed mobilization optimization and collection of peripheral hematopoietic stem cells leading to reduced days of hospitalization and less blood products requirements, being more cost-effective for patients in autologous transplantation settings and for stem cell collection facilities in allogeneic ones. New perspectives include, besides ex vivo manipulation of graft, development of mobilizing drugs in order to perform transplantation even in poor mobilizers patients. An important goal is achieved with the description of genetic polymorphisms related to optimal mobilization of stem cells. New approach using more promising and selective agents called chemokines, such as plerixafor the main leader among these agents are now available and appear complementary for alternative approach using cytokines alone (G-CSF, GM-CSF, SCF). The aim of this review is to assess the evolution of theses biotechnologies and their role in different steps of autologous transplantation and allogeneic stem cells collection.

A prospective dose-finding trial using a modified continual reassessment method for optimization of fludarabine plus melphalan conditioning for marrow transplantation from unrelated donors in patients with hematopoietic malignancies

BACKGROUND

Because of the less graft-facilitating effect by bone marrow (BM), we need to assess a dosage of conditioning more accurately particularly in combination with reduced-intensity conditioning. Thus we examined that modified continual reassessment method (mCRM) is applicable for deciding appropriate conditioning of allogeneic BM transplantation.

PATIENTS AND METHODS

The conditioning regimen consisted of i.v. fludarabine (125 mg/m2) plus an examination dose of i.v. melphalan. The primary endpoint was a donor-type T-cell chimerism at day 28 with successful engraftment defined as >90% donor cells. Five patients per dose level were planned to be accrued and chimerism data were used to determine the next dose.

RESULTS

Seventeen patients were enrolled at doses between 130 and 160 mg/m2. The dose was changed from 160 to 130 mg/m(2) (second level) after five full-donor chimerisms. With one patient of 0% chimera in the second level, the dose was increased to 135 mg/m2 (third level). Following five full-donor chimerisms in the third level, the study was complete as projected.

CONCLUSIONS

mCRM was shown to be a relevant method for dose-finding of conditioning regimen. The melphalan dose of 135 mg/m2 was determined as the recommended phase II dose to induce initial full-donor chimerism.

Decision analysis of peripheral blood versus bone marrow hematopoietic stem cells for allogeneic hematopoietic cell transplantation

Peripheral blood stem cells (PBSCs) and bone marrow (BM) hematopoietic stem cells represent therapeutic alternatives in allogeneic hematopoietic cell transplantation. Randomized controlled trials and an individual patient data meta-analysis (IPDMA) have demonstrated a decreased risk of disease relapse and an increased risk of acute and chronic graft-versus-host disease (aGVHD, cGVHD) in patients receiving PBSCs compared with those receiving BM stem cells. Decision modeling provides quantitative integration of the risks and benefits associated with these alternative treatments, incorporates survival discounts for lower quality of life in patients with aGVHD or cGVHD and post-transplantation relapse, and allows sensitivity analyses for all model assumptions. We have constructed an externally validated Markov model to represent and analyze the decision to use PBSC or BM, estimating post-transplantation state transition probabilities (eg, GVHD and relapse) and quality-of-life discounts from the IPDMA and relevant literature; importantly, this IPDMA synthesized data from primarily adult patients treated with myeloablative (MA) conditioning regimens with T cell-replete matched sibling donors. In this setting, the model demonstrates the superiority of PBSC over BM in both overall and quality-adjusted life expectancy, with a 7-month advantage for PBSC. Sensitivity analyses support this conclusion through a range of values for each variable supported by the IPDMA and quality-of-life discounts, as supported by the literature. However, BM is the optimal strategy in conditions in which the 1-year relapse probability is < 5%. PBSC is the optimal stem cell source in terms of both overall and quality-adjusted life expectancy, except in conditions with a very low relapse probability, in which BM provides optimal outcomes.

Pilot study of allogeneic G-CSF-stimulated bone marrow transplantation: harvest, engraftment, and graft-versus-host disease

Peripheral blood progenitor cell (PBPC) harvests mobilized by granulocyte colony-stimulating factor (G-CSF) contain more CD34+ cells and provide more rapid engraftment than do bone marrow (BM) harvests. However, some reports have suggested a higher risk of chronic graft-versus-host disease (GVHD), possibly because such PBPC harvests contain approximately 10 times more T lymphocytes than do BM harvests. Some groups are attempting to combine the faster engraftment of PBPCs with the lower incidence of GVHD observed after BM transplantation by using G-CSF-primed BM conventionally harvested from iliac crests for allogenic BM transplantation. We report the results of a pilot study of 38 allogeneic transplants using G-CSF-stimulated BM from related donors, with a focus on the harvest composition, engraftment, and incidence of acute and chronic GVHDs.

Disease- or therapy-related bone marrow damage cannot be overcome by changes in stem cell source or dose in allogeneic transplantation

OBJECTIVE

To test whether the functional impairment of the host bone marrow (BM) microenvironment pre-existing at the time of transplantation could be overcome by the increased content of immature cells in allogeneic peripheral blood stem cell transplantation (PBSCT) when compared with bone marrow transplantation (BMT).

METHODS

Cobble stone area forming cells (CAFC) were assayed in normal BM and BM after allogeneic BMT and PBSCT after stable engraftment. Groups were compared by two-tailed t-test.

RESULTS

While BM from 11 normal controls contained an average of 778.8 CAFC-d35 per 10(6) low density bone marrow cells (LDBMC, range 453-1231 per 10(6) LDBMC), BM from patients after BMT contained an average of 123.7 CAFC-d35 per 10(6) LDBMC (range 38-257) per 10(6) LDBMC. BM from patients transplanted with PBSC after myeloablative conditioning contained 128.3 (range 46-305) CAFC-d35 per 10(6) LDBMC (P = 0.89 compared with BMT). Similar results were obtained when patients after PBSCT with non-myeloablative conditioning were included (P = 0.62 compared with BMT). CAFC numbers in patients transplanted in early stages of myeloid leukaemia (acute myeloid leukaemia first remission, chronic myeloid leukaemia first chronic phase) were significantly higher than CAFC numbers in patients transplanted in more advanced stages (P = 0.008) or myelodysplastic syndrome (P = 0.023). The lowest CAFC numbers were found in two cases of retransplantation.

CONCLUSION

Our findings indicate that the functional state of the BM microenvironment rather than stem cell dose or source is limiting for the homing and engraftment of immature haemopoietic cells in clinical transplantation.

Primed marrow for autologous and allogeneic transplantation: A review comparing primed marrow to mobilized blood and steady-state marrow

Mobilized peripheral blood collections, obtained following either chemotherapy (with or without granulocyte colony-stimulating factor (G-CSF)) or G-CSF administration alone, are rapidly replacing traditional bone marrow harvests as the source of cells for hematopoietic stem cell transplantation. According to the Autologous Blood and Marrow Transplant and the International Bone Marrow Transplant Registries, for the years 1998 through 2000, blood stem cell (BSC) transplants accounted for about 80% of autologous transplants in the pediatric age group and more than 90% of the autologous transplants among adults. In allogeneic transplantation, where the donor is a healthy family member or normal volunteer, G-CSF-mobilized BSC transplants are being used more and more frequently, accounting for about 20% of allogeneic transplants in the pediatric age range and more than 40% of allogeneic transplants among adults during the same time period. It is not, therefore, too great a stretch to imagine that BSC transplants will soon be, if not already, in the majority for allogeneic transplantation among adults. The principal reason why this is happening is the prevailing view that BSC engraft more rapidly than marrow stem cells (MSC). However, this view is based on comparisons between primed circulating blood cells (BSC) and unprimed resident marrow cells in the steady state (SS-MSC). If the reason why BSC engraft faster than SS-MSC were a consequence of G-CSF used for mobilization, then would priming of MSC by G-CSF (Prim-MSC) accelerate engraftment of marrow as well? We reviewed the literature of the last 10 years to see if there were enough data to answer this question.

Hematopoietic stem cell graft manipulation as a mechanism of immunotherapy

Hematopoietic stem cell transplants (SCT) are used in the treatment of neoplastic diseases, in addition to congenital, autoimmune, and inflammatory disorders. Both autologous and allogeneic SCT are used, depending on donor availability and the type of disease being treated, resulting in different morbidity and outcomes. In both types of SCT, immune regulation via graft manipulation is being studied, although with highly different targeted outcomes. In general, autologous SCT have lower treatment-related morbidity and mortality, but a higher incidence of tumor relapse, and graft manipulation targets immune augmentation and/or the reduction of immune tolerance. In contrast, allogeneic SCT have a higher incidence of treatment-related morbidity and mortality and a significantly longer time of disease progression, and the targeted outcomes or graft manipulation focus on a reduction in graft versus host disease (GVHD). One source of the increased relapse rate and shorter overall survival (OS) following high dose chemotherapy (HDT) and autologous SCT is the immune tolerance that limits host response, both innate and antigen (Ag) specific, against the tumor. The immune tolerance that is observed is due in part to the tumor burden and prior cytotoxic therapy. Therefore, graft manipulation, as an adjuvant therapeutic approach in autologous SCT, is primarily focused on non-specific or specific immune augmentation using cytokines and vaccines. Recently, manipulation of the infused product as a form of cellular therapy has begun to also focus on approaches to reduce immune tolerance found in transplant patients, both prior to and following HDT and SCT. To this end, graft manipulation to reduce the presence of Fas Ligand (FasL)-expressing cells or interleukin (IL)10 and tumor growth factor (TGF)beta production has been proposed. In contrast to autologous transplantation, graft manipulation during allogeneic transplantation is used extensively. This includes limiting the infusion of T cells within the product or as a donor leukocyte infusion (DLI), resulting in a reduction in GVHD and the induction of long-term survivors. Indeed, allogeneic SCT provide the only curative therapy for patients with chronic myelogenous leukemia (CML), refractory acute leukemia, and myelodysplasia. The curative potential of allogeneic SCT is reduced, however, by the development of GVHD, a potentially lethal T-cell-mediated immune response targeting host tissues [Int. Arch. Allergy Immunol. 102 (1993) 309, J. Exp. Med. 183 (1996) 589]. The morbidity and mortality associated with GVHD limit this technology, resulting focus on those patients who have no alternative therapeutic options or who have advanced disease. Thus, allogeneic SCT provide one of the few statistically supported demonstrations of therapeutic efficacy by T cells (comparison of allogeneic to autologous transplantation). In contrast to autologous transplantation, control of GVHD following allogeneic SCT focuses on immune suppression and the induction of tolerance. Here too, graft manipulation is appropriate, and there are numerous studies of T-cell depletion to reduce GVHD, with or without the isolation and infusion of T cells as DLI. Additional strategies are examining the isolation and infusion of T cells with graft versus leukemia (GVL) activity to reduce GVHD and/or the infusion of genetically manipulated and/or selected cellular populations (monocytes or dendritic cells (DC)) to induce tolerance. Therefore, depending upon the type of transplant, the goals associated with graft manipulation can be radically different. In this review, we emphasize using graft manipulation to regulate immune tolerance and anergy in association with SCT. Although this paper focuses on hematopoietic SCT, it should be noted that these strategies are relevant to conditions other than neoplastic and congenital diseases, including solid organ transplants, and autoimmune and inflammatory diseases.

A comparison of T-, B- and NK-cell reconstitution following conventional or nonmyeloablative conditioning and transplantation with bone marrow or peripheral blood stem cells from human leucocyte antigen identical sibling donors

This retrospective study compares the reconstitution of T, B and NK cells in three groups of patients transplanted for haematological malignancies with grafts from their HLA-identical sibling donors. In all, 15 patients received PBSC after a nonmyeloablative conditioning regimen consisting of fludarabine and 200 cGy TBI, 13 patients received PBSC after myeloablative conditioning and 37 patients received BM after myeloablative conditioning. In the nonmyeloablative group, the NK cells normalised after 1 month, the CD8+ T cells normalised after 3 months, the CD4+ T cells reached near normal values after 9 months and the B cell values were reduced until 12 months after transplant. In the two myeloablative groups, recipients of PBSC had a significantly higher number of CD4+ T cells after 4 months (P=0.004) and after 12 months (P=0.001), than recipients of BM. We found no differences in the T cell reconstitution between the two PBSC groups. This was of interest as the recipients of nonmyeloablative conditioning were older (P<0.001) and had a higher occurrence of chronic GVHD (P<0.05) than the recipients of myeloablative conditioning. In contrast, the recipients of nonmyeloablative conditioning had a delayed B cell recovery when compared to the patients who received myeloablative conditioning (P=0.04).

Peripheral blood stem cell versus bone marrow allotransplantation: does the source of hematopoietic stem cells matter?

Hematopoietic stem cells from 4 different sources have been or are being used for the reconstitution of lymphohematopoietic function after myeloablative, near-myeloablative, or nonmyeloablative treatment. Bone marrow (BM)-derived stem cells, introduced by E. D. Thomas in 1963, are considered the classical stem cell source. Fetal liver stem cell transplantation has been performed on a limited number of patients with aplastic anemia or acute leukemia, but only transient engraftment has been demonstrated. Peripheral blood as a stem cell source was introduced in 1981, and cord blood was introduced as a source in 1988. The various stem cell sources differ in their reconstitutive and immunogenic characteristics, which are based on the proportion of early pluripotent and self-renewing stem cells to lineage-committed late progenitor cells and on the number and characteristics of accompanying "accessory cells" contained in stem cell allografts.

Controlled trial of filgrastim for acceleration of neutrophil recovery after allogeneic blood stem cell transplantation from human leukocyte antigen–matched related donors

The rapid recovery of hematopoiesis after allogeneic blood stem cell transplantation has been attributed to the quality and quantity of hematopoietic progenitors in the blood stem cell grafts from filgrastim-stimulated donors. To determine whether further stimulation with filgrastim after transplantation would affect hematopoietic recovery, a prospective, randomized, controlled study was performed. Forty-two adult recipients of allogeneic blood stem cells from human leukocyte antigen-matched related donors were randomized to receive 10 μg/kg per day filgrastim subcutaneously from day 1 through neutrophil recovery or no growth factor support after transplantation. There was no significant difference between the 2 groups in the number of CD34+ cells infused (median, 4.8 vs 4.3 × 106/kg). Graft-versus-host (GVHD) disease prophylaxis consisted of tacrolimus and steroids for 9 patients and tacrolimus and minimethotrexate for 33 patients. The group receiving filgrastim had a shorter time to neutrophil levels greater than 0.5 × 109/L (day 12 vs day 15, P = .002) and to neutrophil levels greater than 1.0 × 109/L (day 12 vs day 16, P = .01). The filgrastim group also had a trend for earlier discharge (day 16 vs 20, P = .05). There was no significant difference between the groups in time to platelet recovery, number of transfusions, regimen-related toxicity, infection, incidence of GVHD, relapse, survival, or hospital charges. It can be concluded that the administration of filgrastim after allogeneic blood stem cell transplantation shortens the time to neutrophil recovery.

Cytokine-induced expansion of human CD34+ stem/progenitor and CD34+CD41+ early megakaryocytic marrow cells cultured on normal osteoblasts

Thrombocytopenia remains a significant cause of morbidity in cancer patients undergoing allogeneic bone marrow transplantation (BMT), which consumes millions each year for frequent platelet transfusions. Using a novel culture system containing appropriate cytokine(s) on a layer of normal human osteoblasts, we investigated the expansion of early megakaryocytic progenitor cells while maintaining the number of CD34+ stem/progenitor marrow cells in an attempt to provide an effective solution for the problem of post-transplant thrombocytopenia. After seven days of culture, normal human osteoblasts alone without cytokines significantly increased the number of CD34+ and CD34+CD41+ marrow cells. Among the various cytokine combinations tested, both stem cell factor (SCF), interleukin 3 (IL-3)+IL-11 and SCF+IL-3+IL-11+thrombopoietin (TPO) emerged as the most effective in expanding early CD34+CD41+ megakaryocytic cells. Early CD34+CD41+ megakaryocytic cells have increased by 3.1- and 4.7-fold compared with day 7 control cultures, and by 62- and 94-fold, respectively, compared with day 0 input, respectively. Also, late CD41+ megakaryocytic cells have increased by 15.4- and 27.5-fold compared with day 7 control cultures in the presence of the same two combinations. In addition, the same cytokine combinations achieved 17.6- and 13.3-fold increases in the number of CD34+ marrow cells after the same seven days of culture on a layer of human osteoblasts. The combination (SCF+IL-3+IL-11+TPO) achieved the highest expansion of CD34+CD41+ early megakaryocytic cells from human marrow CD34+ cells reported so far in the literature. Recently, transplantation of SCF+IL-1+IL-3+TPO ex vivo expanded megakaryocytic progenitor cells as a supplement has been shown to accelerate platelet recovery by three to five days in mice. Therefore, the clinical use of the combination (SCF+IL-3+IL-11+TPO) for ex vivo expansion of CD34+ and megakaryocytic progenitor cells from a portion of the donor's marrow harvest is warranted in allogeneic BMT. Such a protocol would accelerate platelet recovery and shorten the period of hospitalization after allogeneic BMT. The present study has confirmed the role of human osteoblasts in supporting the proliferation and maintenance of human CD34+ stem/progenitor marrow cells. Given the facilitating role of osteoblasts shown previously in several allogeneic BMT studies in mice, it is possible to envisage a future role for donor osteoblasts in clinical BMT. Transplantation of the cultured donor osteoblasts together with the ex vivo expanded CD34+ marrow cells as a supplement might not only accelerate platelet recovery but also prevent acute graft-versus-host disease in allogeneic BMT. The present novel culture system should have useful clinical application in allogeneic BMT.

Factors influencing platelet recovery after autologous transplantation of G-CSF-mobilized peripheral blood stem/progenitor cells following myeloablative therapy in 50 heavily pretreated lymphoma patients

Delayed platelet recovery following autologous PBPCs transplantation after myeloablative therapy remains an unresolved problem in lymphoma patients heavily pretreated with several chemotherapy cycles and/or radiotherapy. In the present study of 50 lymphoma patients, the factors influencing platelet recovery after myeloablative therapy followed by autologous PBPCs transplantation were analysed retrospectively. The median age was 42 years (range, 15-58). Fourteen patients had HD and 36 had NHL (13 high-grade and 23 low-grade); most (80%) had stage III or IV. Twenty-two patients had received radiotherapy to various extents before mobilization. The mean number of previous chemotherapy cycles was seven (range 3-24) of different regimens (range 1-4). A median of three leukapheresis procedures (range 1-5) was performed after G-CSF mobilization. Single leukapheresis was sufficient in only one patient. A significant correlation was found between the BFU-E content of autografts and platelet recovery after transplantation. Neither the patient's age and sex nor the stage and grade of lymphoma had any effect on platelet recovery after transplantation. Neither the type of myeloablative therapy used or the dose of G-CSF administered after transplantation had any effect on platelet recovery after transplantation. The type of previous chemotherapy cycles was a major adverse factor affecting the progenitor cell yield in the autografts. Lymphoma patients previously treated with ASHAP and/or Dexa-BEAM cycles had less progenitor cell yield. The chemotherapeutic agents used in previous cycles also had a clear adverse effect on the progenitor cell yield in the autografts. Lymphoma patients previously treated with cycles including cytarabine and/or cisplatin showed significantly less progenitor cell yield and slower platelet recovery after transplantation. All seven patients with delayed platelet recovery had received cytarabine and/or cisplatin in several previous ASHAP and/or Dexa-BEAM cycles. All seven patients had a BFU-E count of less than 1 x 10(5)/kg yield in the autografts.