Circulating autologous stem cells collected in very early remission from acute non-lymphoblastic leukaemia produce prompt but incomplete haemopoietic reconstitution after high dose melphalan or supralethal chemoradiotherapy

Current State and Issues of Regenerative Medicine for Rheumatic Diseases

The prognosis of rheumatic diseases is generally better than that of malignant diseases. However, some cases with poor prognoses resist conventional therapies and cause irreversible functional and organ damage. In recent years, there has been much research on regenerative medicine, which uses stem cells to restore the function of missing or dysfunctional tissues and organs. The development of regenerative medicine is also being attempted in rheumatic diseases. In diseases such as systemic sclerosis (SSc), systemic lupus erythematosus (SLE), and rheumatoid arthritis, hematopoietic stem cell transplantation has been attempted to correct and reconstruct abnormalities in the immune system. Mesenchymal stem cells (MSCs) have also been tried for the treatment of refractory skin ulcers in SSc using the ability of MSCs to differentiate into vascular endothelial cells and for the treatment of systemic lupus erythematosus SLE using the immunosuppressive effect of MSCs. CD34-positive endothelial progenitor cells (EPCs), which are found in the mononuclear cell fraction of bone marrow and peripheral blood, can differentiate into vascular endothelial cells at the site of ischemia. Therefore, EPCs have been used in research on vascular regeneration therapy for patients with severe lower limb ischemia caused by rheumatic diseases such as SSc. Since the first report of induced pluripotent stem cells (iPSCs) in 2007, research on regenerative medicine using iPSCs has been actively conducted, and their application to rheumatic diseases is expected. However, there are many safety issues and bioethical issues involved in regenerative medicine research, and it is essential to resolve these issues for practical application and spread of regenerative medicine in the future. The environment surrounding regenerative medicine research is changing drastically, and the required expertise is becoming higher. This paper outlines the current status and challenges of regenerative medicine in rheumatic diseases.

Evolution of Peripheral Blood Stem Cell Transplantation

Blood-derived progenitors have become the predominant source of hematopoietic stem cells for clinical transplantation. The main advantages compared to the bone marrow are as follows: harvesting blood stem cells is less painful for the donor, utilizes much less resources such as operating theater time and general anesthesia, and, above all, is associated with significantly accelerated reconstitution. The latter has ultimately improved patient safety as a consequence of significantly shortened aplastic phase and hence reduced morbidity and mortality after transplantation. Basic and translational research efforts in the 1960s to the mid-1980s have made the first blood stem cell transplantation in Heidelberg in 1985 possible. Diverse groups around the world have contributed to incremental knowledge that culminated in the first successful attempts in blood stem cell transplantation. These efforts have spawned modern research into stem cell biology and the immune modulatory effects of allogeneic transplantations.

Early Hematopoietic Reconstitution after Autologous Transplantation with Blood-Derived Stem Cells in a Patient with Advanced Lymphoma

A 30-year-old man with advanced non-Hodgkin lymphoma underwent repeated leukaphereses for harvesting blood-derived hemopoietic stem cells. Collection was started 8-10 days after the end of L-VAMP therapy (3 cycles). Nine procedures were performed and a total of 65.4× 109 mononuclear cells (0.87× 109/Kg) were collected, processed, cryopreserved and stored in liquid nitrogen. The yields of CFU-GM, BFU-E and CFU-GEMM were respectively 964× 104 (12.4× 104/Kg), 249× 104 (3.2× 104/Kg) and 798× 104 (10.4× 104). The patient received a myeloablative regimen consisting of fractionated total body irradiation (1200 cGy) and cyclophosphamide (120 mg/kg) followed by infusion of his own thawed cells. Early trilineage hematopoietic recovery was first observed on day +8; 1× 109/l WBC were reached on day + 11, 0.5× 109/l PMN on day + 13 and 50× 109/l platelets on day + 11. Course was uneventful and the patient was discharged from hospital on day + 21. Eight months after transplant the patient is in continuous unmaintained complete remission with normal blood cell counts. This reports suggests that complete and sustained engraftment can be achieved with peripheral stem cells recruited after “soft” chemotherapy.

Peripheral Blood Stem Cell Transplantation: Critical Review

Autologous blood stem cell transplantations have been increasingly performed worldwide for almost ten years in place of autologous bone marrow transplantation and even of allogenic bone marrow transplantation. Several crucial issues were the subjects of impassioned controversies. Some of them are now satisfactorily answered while others still remain unresolved. First, it is now possible to conclude today that peripheral blood stem cells (PBSC) are undoubtedly capable of restoring short term hematopoiesis when reinfused after myeloablative therapy as well and even more rapidly than bone marrow stem cells, provided that they have been previously collected in sufficient amounts. On the opposite, it is still impossible to firmly prove that their very immature CD34+ cell subset, although in vitro functionally and phenotypically almost identical to their marrow counterpart, is actually responsible for sustained long term hematopoietic recovery, even if it is likely that these cells play a key role.

Most of the time, using chemotherapy alone or a combination of chemotherapy and cytokine(s), mobilizing regimens allow collection of appropriate yields of PBSC with only a small number of apheresis cycles, provided that a sufficient number of residual stem cells remains to be stimulated, when, on the contrary, collection in steady-state is time-consuming and does not provide further accelerated post transplant hematopoietic recovery.

It was initially hypothesized that PBSC could have a lower likelihood of tumoral contamination compared with bone marrow. In fact, biological as well as clinical data are discordant and probably depend largely on the type of disease, its evolutive history and its way of dissemination. Furthermore, the respective impact on the development of further relapse of graft contamination and of residual tumor cells into patient remains to be determined.

Finally, although it has often been claimed that the cost of mobilization, collection and cryopreservation of PBSC would be much higher than the cost of bone marrow harvesting, it is now possible to assert that the whole ABSCT procedure, including this preliminary phase, as well as the post-transplant period, allows an indisputable saving compared with ABMT.

These advantages are already sufficient reasons “per se” to propose ABSCT in place of ABMT or alloBMT in many indications even if their clinical benefit, in terms of disease-outcome, remains to be prospectively explored.

Sources of Human Hematopoietic Stem Cells for Transplantation–A Review

Transplantation of hematopoietic stem cells provides a means of replacing a defective hematopoietic system in patients with a wide range of malignant and nonmalignant disorders that affect the blood forming tissue. The same procedure has also allowed dose-escalation of standard chemotherapy and radiotherapy in the treatment of malignant disease of nonhematological origin. Until recently, bone marrow has been the sole source of hematopoietic stem cells, but limitations of conventional bone marrow transplantation have stimulated a search for alternative sources and uses of stem cells. Fetal tissues (especially liver) are a recognized source of transplantable stem cells and offer the great advantage of reduced immunogenicity, potentially removing the problems of tissue type matching. Umbilical cord blood is also a rich source of stem cells and, although it contains alloreactive cells, it is readily available without special ethical constraints. Both fetal tissue and cord blood suffer the disadvantages of limited numbers of stem cells per donation, and there is much interest in the development of technologies for the safe and reliable expansion and/or pooling of stem and progenitor cells. The observation that small numbers of stem cells are found in the peripheral blood of adults has led to the exploitation of the blood as a further source of stem cells. The ability to mobilize these cells from the medullary compartment into the periphery by the use of chemotherapy and/or recombinant hematopoietic growth factors has enabled the collection of sufficient numbers of cells for transplantation purposes. All of these advances are increasing the options and the range of choices available to clinicians and patients in the arena of hematopoietic stem cell transplantation.

Tbo-Filgrastim versus Filgrastim during Mobilization and Neutrophil Engraftment for Autologous Stem Cell Transplantation

There are limited data available supporting the use of the recombinant granulocyte colony-stimulating factor (G-CSF), tbo-filgrastim, rather than traditionally used filgrastim to mobilize peripheral blood stem cells (PBSC) or to accelerate engraftment after autologous stem cell transplantation (ASCT). We sought to compare the efficacy and cost of tbo-filgrastim to filgrastim in these settings. Patients diagnosed with lymphoma or plasma cell disorders undergoing G-CSF mobilization, with or without plerixafor, were included in this retrospective analysis. The primary outcome was total collected CD34(+) cells/kg. Secondary mobilization endpoints included peripheral CD34(+) cells/μL on days 4 and 5 of mobilization, adjunctive use of plerixafor, CD34(+) cells/kg collected on day 5, number of collection days and volumes processed, number of collections reaching 5 million CD34(+) cells/kg, and percent reaching target collection goal in 1 day. Secondary engraftment endpoints included time to neutrophil and platelet engraftment, number of blood product transfusions required before engraftment, events of febrile neutropenia, and length of stay. A total of 185 patients were included in the final analysis. Patients receiving filgrastim (n = 86) collected a median of 5.56 × 10(6) CD34(+) cells/kg, compared with a median of 5.85 × 10(6) CD34(+) cells/kg in the tbo-filgrastim group (n = 99; P = .58). There were no statistically significant differences in all secondary endpoints with the exception of apheresis volumes processed (tbo-filgrastim, 17.0 liters versus filgrastim, 19.7 liters; P < .01) and mean platelet transfusions (tbo-filgrastim, 1.7 units versus filgrastim, 1.4 units; P = .04). In conclusion, tbo-filgrastim demonstrated similar CD34(+) yield compared with filgrastim in mobilization and post-transplantation settings, with no clinically meaningful differences in secondary efficacy and safety endpoints. Furthermore, tbo-filgrastim utilization was associated with cost savings of approximately $1406 per patient utilizing average wholesale price.

Granulocyte colony-stimulating factor produces long-term changes in gene and microRNA expression profiles in CD34+ cells from healthy donors

Granulocyte colony-stimulating factor is the most commonly used cytokine for the mobilization of hematopoietic progenitor cells from healthy donors for allogeneic stem cell transplantation. Although the administration of this cytokine is considered safe, knowledge about its long-term effects, especially in hematopoietic progenitor cells, is limited. On this background, the aim of our study was to analyze whether or not granulocyte colony-stimulating factor induces changes in gene and microRNA expression profiles in hematopoietic progenitor cells from healthy donors, and to determine whether or not these changes persist in the long-term. For this purpose, we analyzed the whole genome expression profile and the expression of 384 microRNA in CD34(+) cells isolated from peripheral blood of six healthy donors, before mobilization and at 5, 30 and 365 days after mobilization with granulocyte colony-stimulating factor. Six microRNA were differentially expressed at all time points analyzed after mobilization treatment as compared to the expression in samples obtained before exposure to the drug. In addition, 2424 genes were also differentially expressed for at least 1 year after mobilization. Of interest, 109 of these genes are targets of the differentially expressed microRNA also identified in this study. These data strongly suggest that granulocyte colony-stimulating factor modifies gene and microRNA expression profiles in hematopoietic progenitor cells from healthy donors. Remarkably, some changes are present from early time-points and persist for at least 1 year after exposure to the drug. This effect on hematopoietic progenitor cells has not been previously reported.

Current clinical indications for plerixafor

Autologous and allogeneic hematopoietic stem cell (HSC) transplantation are considered the standard of care for many malignancies including lymphoma, multiple myeloma, and some leukemias. In many cases, mobilized peripheral blood has become the preferred source for HSCs. Plerixafor, an inhibitor of the interaction between CX chemokine receptor 4 (CXCR4) and stromal derived factor-1 alpha (SDF-1), has been evaluated in clinical trials and approved by the FDA and EMA. This agent has very modest toxicity and appears to be quite potent at HSC mobilization. Current clinical indications for the use of plerixafor are the subject of this review.

A (selective) history of Australian involvement in cytokine biology

This review focuses on contributions to cytokine biology made by Australians in Australia. It is clearly biased by my own experiences and selective recollections especially related to the colony-stimulating factors in which Australian involvement has been pre-eminent from discovery to clinical use. Nevertheless Australian scientists have also made profound contributions to other areas of cytokine and growth factor biology (including interferons, inflammatory cytokines, chemokines and epidermal, insulin-like and vascular endothelial growth factors) that are briefly described in this review as well as other chapters in this volume.

Advances in stem cell mobilization

The use of mobilized peripheral blood stem cells (PBSCs) has largely replaced the use of bone marrow as a source of stem cells for both allogeneic and autologous stem cell transplantation. G-CSF with or without chemotherapy is the most commonly used regimen for stem cell mobilization. Some donors or patients, especially the heavily pretreated patients, fail to mobilize the targeted number of stem cells with this regimen. A better understanding of the mechanisms involved in hematopoietic stem cell (HSC) trafficking could lead to the development of newer mobilizing agents and therapeutic approaches. This review will cover the current methods for stem cell mobilization and recent developments in the understanding of the biology of stem cells and the bone marrow microenvironment.

Mobilisation strategies for normal and malignant cells

This review evaluates the latest information on the mobilisation of haemopoietic stem cells for transplantation, with the focus on what is the current best practice and how new understanding of the bone marrow stem cell niche provides new insights into optimising mobilisation regimens. The review then looks at the mobilisation of mesenchymal stromal cells, immune cells as well as malignant cells and what clinical implications there are.

How I treat patients who mobilize hematopoietic stem cells poorly

Transplantation with 2-5 × 106 mobilized CD34+cells/kg body weight lowers transplantation costs and mortality. Mobilization is most commonly performed with recombinant human G-CSF with or without chemotherapy, but a proportion of patients/donors fail to mobilize sufficient cells. BM disease, prior treatment, and age are factors influencing mobilization, but genetics also contributes. Mobilization may fail because of the changes affecting the HSC/progenitor cell/BM niche integrity and chemotaxis. Poor mobilization affects patient outcome and increases resource use. Until recently increasing G-CSF dose and adding SCF have been used in poor mobilizers with limited success. However, plerixafor through its rapid direct blockage of the CXCR4/CXCL12 chemotaxis pathway and synergy with G-CSF and chemotherapy has become a new and important agent for mobilization. Its efficacy in upfront and failed mobilizers is well established. To maximize HSC harvest in poor mobilizers the clinician needs to optimize current mobilization protocols and to integrate novel agents such as plerixafor. These include when to mobilize in relation to chemotherapy, how to schedule and perform apheresis, how to identify poor mobilizers, and what are the criteria for preemptive and immediate salvage use of plerixafor.

Comparison of unmobilized and mobilized graft characteristics and the implications of cell subsets on autologous and allogeneic transplantation outcomes

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) are considered the standard of care for many malignancies, including lymphoma, myeloma, and some leukemias. In many cases, mobilized peripheral blood has become the preferred source of hematopoietic stem cells. The efficacy of different mobilization regimens and transplantation outcomes based on cell doses has been well studied; however, the characteristics of the stem cell graft may be of equal importance with respect to patient outcomes following autologous or allogeneic HSCT. This review summarizes available preclinical and clinical data for bone marrow and mobilized peripheral blood HSCT characteristics, defined as the cell types found in the graft as well as their gene expression profiles. It also explores how graft characteristics can affect bone marrow homing, engraftment, immune reconstitution, and other posttransplantation outcomes in both the allogeneic and autologous HSCT settings.

Spanish Society of Medical Oncology consensus for the use of haematopoietic colony-stimulating factors in cancer patients

Neutropenia is a common complication of cancer chemotherapy. Colony-stimulating factors (CSF) may be used to avoid neutropenia-associated complications. The Spanish Society of Medical Oncology (SEOM) recently constituted a working group to review the main issues concerning the use of CSF and carried out a consensus process about the use of CSF in cancer patients, held in Madrid on 26 May 2006. The group concluded the following recommendations: prophylactic use of CSF is recommended when a rate of febrile neutropenia (FN) higher than 20% is expected without the use of CSF or when additional risk factors for neutropenia exist; therapeutic use of CSF is recommended in order to treat FN episodes but not to treat afebrile neutropenic episodes. In addition, the use of CSF is considered effective when used to mobilise stem cells before high-dose chemotherapy and when used for chemotherapy schedule optimisation in dose-dense and in dose-intense regimens.

The long road to the thymus: the generation, mobilization, and circulation of T-cell progenitors in mouse and man

The majority of T cells develop in the thymus. T-cell progenitors in the thymus do not self-renew and so progenitor cells must be continuously imported from the blood into the thymus to maintain T-cell production. Recent work has shed light on both the identity of the cells that home to the thymus and the molecular mechanisms involved. This review will discuss the cells in the bone marrow and blood that are involved in early thymopoiesis in mouse and man. Understanding the pre-thymic steps in T-cell development may translate into new therapeutics, especially in the field of hematopoietic stem cell transplantation.

The effect of bleeding on hematopoietic stem cell cycling and self-renewal

Hematopoietic stem cells (HSCs) divide and give rise to more committed progenitors, which ultimately produce all lineages of blood cells. HSCs can be induced to enter the cell cycle in vitro and in vivo by stimulatory cytokines and in vivo by ablation of bone marrow (BM) cells with irradiation or chemotherapeutic agents. Although it has been postulated that rates of HSC proliferation increase with normal hematopoietic stresses, such as infection or hemorrhage, this hypothesis has never been directly tested. The ability to analyze HSCs prospectively by cell-surface phenotype c-kit(+), Thy1.1(lo), Sca-1(+), Linage(neg/lo) has allowed us to perform a detailed examination of the effects of bleeding on the cell cycle kinetics of HSCs. Our results demonstrate for the first time that HSCs in both the BM and the spleen proliferate and self-renew in response to tail-vein bleeding in mice. This response was suppressed when red blood cells, but not when white blood cells, were transferred after bleeding. Thus, regulators of HSC proliferation can sense and respond to red blood cell levels.

G-CSF- and GM-CSF-induced upregulation of CD26 peptidase downregulates the functional chemotactic response of CD34+CD38− human cord blood hematopoietic cells

OBJECTIVE

Cytokine treatment with granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and stem cell factor (SCF) is a mainstay of current and future clinical and research protocols for peripheral blood stem cell mobilization, therapeutic care after hematopoietic stem cell transplantation (HSCT), and ex vivo hematopoietic stem and progenitor cell (HSC/HPC) expansion. We have previously shown that the peptidase CD26 (DPPIV/dipeptidylpeptidase IV) negatively regulates HSC/HPC and that inhibition of CD26 improves the chemotactic ability and trafficking of HSC/HPC. We set out to establish whether short-term in vitro G-CSF, GM-CSF, or SCF treatment upregulates CD26 and thereby has a detrimental effect on the chemotactic potential of HSC/HPC that could be reversed by CD26 inhibitor treatment.

MATERIALS AND METHODS

CD34+ or CD34+CD38- cells, a population enriched in HSC, were isolated from human umbilical cord blood and subjected to G-CSF, GM-CSF, or SCF treatment. We then evaluated CD26 expression, CD26 activity, and CXCL12 (SDF-1)-induced migration in the presence or absence of a CD26 inhibitor, Diprotin A.

RESULTS

Treatment with G-CSF and GM-CSF but not SCF upregulates CD26 expression and activity resulting in a CD26 inhibitor-reversible downregulation of CXCL12-induced chemotactic response.

CONCLUSIONS

Short-term in vitro G-CSF and GM-CSF treatment upregulates the peptidase CD26, resulting in downregulation of the functional ability of CD34+CD38- cells to respond to the chemokine CXCL12. This suggests that current and future clinical protocols utilizing G-CSF and GM-CSF may have unforeseen detrimental effects on the trafficking of HSC/HPC during HSCT that can be overcome through the use of CD26 inhibitors.

Involvement of Proteases in Cytokine-Induced Hematopoietic Stem Cell Mobilization

The number of circulating stem cells and progenitor cells can be increased by physiological stress, such as exercise, stress, and infections. The process of shifting the stem cells from the bone marrow into the peripheral blood is referred to as "mobilization" or "egress." Cytokine-mobilized hematopoietic progenitor cells (HPCs) are currently used for autologous or allogeneic stem cell transplantation in a variety of malignant and nonmalignant diseases. In spite of the wide-spread use of mobilized peripheral blood stem cells for transplantation, the mechanisms underlying mobilization are still incompletely understood. Here we discuss the role of neutrophils and proteases as mediators of stem cell mobilization.

Apheresis techniques for collection of peripheral blood progenitor cells

The combination of effective mobilisation protocols and efficient use of apheresis machines has caused peripheral blood progenitor cells (PBPC) transplantation to grow rapidly. The development of apheresis technology has improved over the years. Today PBSC procedures have changed towards systems to minimise operator interaction and to reduce the collection of undesired cells such as polymorphonuclear cells and platelets using functionally closed, sterile environments for PBSC collection in keeping with Good Manufacturing Practice guidelines. Blood cell separators with continuous flow technique allow the processing of more blood than intermittent flow devices resulting in higher PBSC yields. Large volume leukapheresis with the processing of 3-4-fold donor's/patient's blood volume can increase the number of collected progenitor cells. Therefore, intermittent flow cell separators are indicated if only single vein access is available. Anticoagulant induced hypocalcaemia is an often observed side effect in long lasting PBPC harvesting and monitoring of electrolytes should be performed especially at the end of the apheresis procedure to supplement low levels of potassium, calcium or magnesium. Refinement and improvement of collection techniques continue to add to the armamentarium of current approaches for cancer and non-malignant conditions and will enable future strategies.

Factors for PBPC collection efficiency and collection predictors

Factors affecting collection efficiency of peripheral blood stem cells (PBSCs) include patient's age, diagnosis, preceding chemoradiotherapy, disease invasion of the bone marrow and mobilizing chemotherapy in PBSC collection for autologous transplants. Mobilizing cytokines, timing for apheresis, machines and operating software would affect mobilization and collection of PBSCs both for autologous and allogeneic transplantation. Also donor's age and gender would affect PBSC yield for allogeneic transplantation. Surrogate markers including peripheral blood CD34+ cell counts before mobilization and on day of collection have been reported to predict the yield of PBSC harvest. A number of standard procedures have been developed based on these findings. Newer agents for PBSC mobilization are being evaluated and still other factors affecting mobilization are being sought to better predict and cope with poor mobilization.

Human embryonic or adult stem cells: an overview on ethics and perspectives for tissue engineering

Over the past few years, research on animal and human stem cells has experienced tremendous advances which are almost daily loudly revealed to the public on the front-page of newspapers. The reason for such an enthusiasm over stem cells is that they could be used to cure patients suffering from spontaneous or injuries-related diseases that are due to particular types of cells functioning incorrectly, such as cardiomyopathy, diabetes mellitus, osteoporosis, cancers, Parkinson's disease, spinal cord injuries or genetic abnormalities. Currently, these diseases have slightly or non-efficient treatment options, and millions of people around the world are desperately waiting to be cured. Even if not any person with one of these diseases could potentially benefit from stem cell therapy, the new concept of "regenerative medicine" is unprecedented since it involves the regeneration of normal cells, tissues and organs which could allow to treat a patient whereby both, the immediate problem would be corrected and the normal physiological processes restored, without any need for subsequent drugs. However, conflicting ethical controversies surround this new medicine approach, inside and outside the medical community, especially when human embryonic stem cells (h-ESCs) are concerned. This ethical debate on clinical use of h-ESCs has recently encouraged the research on "adult" stem cells (ASCs) regarded as a less conflicting alternative for the future of regenerative medicine.

Comparison of two leukapheresis programs for computerized collection of blood progenitor cells on a new cell separator

BACKGROUND

Peripheral blood progenitor cells (PBPCs) can be collected on various cell separators. Two leukapheresis programs (LP-MNC and LP-PBSC-Lym) were evaluated for computerized collection of PBPCs on a new cell separator.

STUDY DESIGN AND METHODS

Leukapheresis assisted by the LP-MNC or LP-PBSC-Lym software was performed for the harvesting of PBPCs in 52 oncology patients after chemotherapy plus G-CSF treatment and in 18 healthy subjects after G-CSF mobilization alone.

RESULTS

A total of 38 components from 33 donors via LP-MNC and 43 components from 37 donors via LP-PBSC-Lym were collected with a median of one (range, one to two) standard-volume leukapheresis procedures (9.2-13.3 L) per donor. There were no significant differences between the two groups concerning median counts of WBCs, CD34+ cells, CD34+ cell yields per harvest, and CD34+ cell yields of cumulative harvests. The blood cell counts after leukapheresis revealed that the LP-MNC resulted in significantly higher platelet loss than LP-PBSC-Lym (p = 0.024): 35.9 percent (range, 19.2%-66.1%) versus 29.7 percent (11.6%-52.3%). Regarding the CD34+ cell collection efficiency, the LP-MNC program was significantly better than the LP-PBSC-Lym program (p < 0.001): 77.5 percent (range, 35.5%-98.9%) versus 58.3 percent (range, 20.4%-98.9%). However, concentrates collected by the LP-PBSC-Lym program had significantly higher percentages of MNCs (p < 0.001) and CD34+ cells (p = 0.028) than harvests with the LP-MNC program: 90 percent (range, 69%-99%) versus 70 percent (range, 35%-98%) and 1.2 percent (range, 0.2%-7.3%) versus 0.7 percent (range, 0.2%-6.0%), respectively. No leukapheresis-related serious adverse events were seen, and time for hematopoietic engraftment was equivalent to data published in the literature.

CONCLUSION

The LP-MNC program shows a significantly better CD34+ cell collection efficiency than the LP-PBSC-Lym program. However, collections with the LP-MNC program result in PBPC components with a lower MNC and CD34+ cell concentrations and a higher apheresis-related loss of patient's platelets.

Peripheral blood progenitor cell transplantation

Peripheral blood progenitor cells (PBPCs) have become increasingly popular over the last 15 years as the source of hematopoietic stem cells for transplantation. In the early 1990s, PBPCs replaced bone marrow (BM) as the preferred source of autologous stem cells, and recently the same phenomenon is seen in the allogeneic setting. Under steady-state conditions, the concentration of PBPCs (as defined by CFU-GM and/or CD34+ cells) is very low, and techniques were developed to increase markedly this concentration. Such mobilization techniques include daily injections of filgrastim (G-CSF) or a combination of chemotherapy and growth factors. Leukapheresis procedures allow the collection of large numbers of circulating white blood cells (and PBPCs). One or two leukapheresis procedures are often sufficient to obtain the minimum number of CD34+ cells considered necessary for prompt and consistent engraftment (i.e., 2.5-5.0 x 10(6)/kg). As compared to BM, autologous transplants with PBPCs lead to faster hematologic recovery and have few, if any, disadvantages. In the allogeneic arena, PBPCs also result in faster engraftment, but at a somewhat higher cost of chronic graft-versus-host disease (GvHD). This may be a double-edged sword leading to both increased graft-versus-tumor effects and increased morbidity. The rapid advances in the study of hematopoietic, and even earlier, stem cells will continue to shape the future of PBPC transplantation.

Stem cells in the aetiopathogenesis and therapy of rheumatic disease

Animal models of autoimmune disease and case reports of patients with these diseases who have been involved in bone marrow transplants have provided important data implicating the haemopoietic stem cell in rheumatic disease pathogenesis. Animal and human examples exist for both cure and transfer of rheumatoid arthritis, systemic lupus erythematosus (SLE) and other organ-specific diseases using allogeneic haemopoietic stem cell transplantation. This would suggest that the stem cell in these diseases is abnormal and could be cured by replacement of a normal stem cell although more in vitro data are required in this area. Given the morbidity and increased mortality in some patients with severe autoimmune diseases and the increasing safety of autologous haemopoietic stem cell transplantation (HSCT), pilot studies have been conducted using HSCT in rheumatic diseases. It is still unclear whether an autologous graft will cure these diseases but significant remissions have been obtained which have provided important data for the design of randomized trials of HSCT versus more conventional therapy. Several trials are now open to accrual under the auspices of the European Bone Marrow Transplant Group/European League Against Rheumatism (EBMT/EULAR) registry. Future clinical and laboratory research will need to document the abnormalities of the stem cell of a rheumatic patient because new therapies based on gene therapy or stem cell differentiation could be apllied to these diseases. With increasing safety of allogeneic HSCT it is not unreasonable to predict cure of some rheumatic diseases in the near future.

Immune reconstitution and production of intracellular cytokines in T lymphocyte populations following autologous peripheral blood stem cell transplantation

For the better understanding of engraftment properties after autologous peripheral blood stem cell transplantation (PBSCT), hematopoietic recovery, immune reconstitution and functional capacity of cytokine production in different lymphocyte populations were examined. In a prospective study, we examined 24 patients suffering from different malignancies after autologous PBSCT. The examination intervals were 1, 3, 6 and 12 months after PBSCT. T cells, B cells and NK cells were analyzed using flow cytometry. The expression and kinetics of cytokines in T lymphocytes were evaluated in 10 patients by intracellular staining of cytokines after PMA/ionomycin stimulation. We observed rapid hematopoietic engraftment proceeding to stable long-term reconstitution. For CD3(+) lymphocytes, a consistent reconstitution associated with an increase in CD3(+)CD8(+) cytotoxic T cells was observed, whereas the CD3(+)CD4(+) helper/inducer T cells remained low (< 200/microl). Impaired B lymphopoiesis with severe depression (<1%) was detected 1 month after PBSCT but recovered thereafter (12.8% after 3 months). The percentages of cytokine-producing T cells and the mean fluorescence intensity (MFI) shifts suggested an insufficient capacity for producing IFNgamma, in particular for CD3(+)CD4(+) T cells, compared to healthy volunteers early after PBSCT. Rapid hematopoietic recovery and partly impaired immune reconstitution, especially regarding the regeneration of B lymphocytes and T helper cells, was observed. The CD4(+) subpopulation remained low throughout the period of examination, whereas the B cells showed a delayed recovery after 3 months. Cytokine production proved to be sufficient after in vitro stimulation in T cell populations with the exception of IFNgamma synthesis.

Flow cytometric enumeration and immunophenotyping of hematopoietic stem and progenitor cells

Flow cytometric enumeration of CD34(+) hematopoietic stem and progenitor cells (HPC) is widely used to evaluate the adequacy of peripheral blood stem cell grafts and is also useful for planning the apheresis sessions needed to obtain these grafts. A state-of-the-art method to enumerate CD34(+) cells has been developed that makes use of a multiparameter definition of HPC, based on their light scatter characteristics and dim expression of CD45, utilizing fluorescent counting beads. This approach allows the absolute CD34(+) cell count to be determined directly from a flow cytometer. The method can be extended with a viability stain and additional markers for further immunologic characterization of CD34(+) cells, and has been successfully implemented in multicenter trials. Using such a standardized assay, it should be possible to define more accurately the lower threshold for a safe HPC graft in terms of short- and long-term hematopoietic reconstitution. Semin Hematol 38:139-147.

Clinically relevant hypokalaemia, hypocalcaemia, and loss of hemoglobin and platelets during stem cell apheresis

Since the introduction of hematopoietic growth factors, the collection of mobilized stem cells via leukapheresis has widely replaced the harvest of bone marrow in both autologous and allogeneic transplantation settings. We investigated the frequency and the extent of anticoagulant-induced electrolyte changes and the cell-separation-related loss of hemoglobin and platelets. In our study a total of 200 leukaphereses were performed on 60 patients with hematological malignancies. The electrolytes (calcium and potassium) were determined photometrically pre- and post-apheresis. Blood counts were analyzed to calculate the relative decline in hemoglobin and platelet counts. Stem cells were collected by processing a mean total blood volume of 11.6+/-3.9 L with a citrate consumption of 1,345+/-126 mL. More than 50% of all patients needed replacement therapy of either potassium or calcium. In non-substituted patients the initial serum potassium concentration dropped by 11.3+/-7.0% to 3.25+/-0.33 mmol/L post apheresis. In 21% of non-substituted patients, clinical relevant hypokalaemia was observed with levels < 3 mmol/L. The mean citrate-induced reduction of the total calcium was 5.5+/-6.0%. In addition the relative loss of hemoglobin and platelet counts amounted to 10.7+/-5.2% and 24.2+/-12.5%, respectively. In addition to the well-documented citrate-induced hypocalcaemia, we observed a considerable reduction in serum potassium during stem cell apheresis. This can result in a clinically relevant, substitution requiring hypokalaemia. The modest decline in hemoglobin and platelet counts suggested that levels of >9 g/dl (Hb) and platelets >30 x 10(9)/L are sufficient for a safe standard leukapheresis.

Mobilization and transplantation of peripheral blood stem cells

Two hundred nineteen patients underwent peripheral blood stem cell (PBSC) transplantation from 1990 to 1997. Stem cells were mobilized with cyclophosphamide (CY), or with CY plus Taxol or etoposide, followed by cytokines, and collected when leukocyte counts > or = 1,000/microl, or when CD34+ counts > or = 20/microl. On average, four to five collections were needed to obtain sufficient PBSC for engraftment. When CD34+ counts were used, the average number of collections decreased from 5.4 to 4.2. A discrepancy was noted in the extraction ratios and number of collections that depended on the optical density (I/O) setting of the leukapheresis machine. Patients collected at a setting of 100 had higher extraction ratios and required fewer collections (mean = 2.7) than those collected at 150 (mean = 4.4). This result was unexpected, because the entire mononuclear cell layer is collected at the higher I/O setting. Further analysis revealed that a larger volume of red cells was collected at 150 than at 100. These procedures used a small-volume collection chamber, so the chamber was apparently overloaded by RBC at the higher setting. More rapid recovery of neutrophil counts and platelet counts was seen in PBSC transplants than in autologous marrow transplants; moreover, PBSC transplant patients required fewer RBC and platelet transfusions. Sixteen out of 21 normal donors for allogeneic PBSC transplants gave adequate collections (> 2.5 x 10(6) CD34+ cells/kg), but three donors failed to yield > or = 1.5 x 10(6) CD34 cells/kg. This suggests an inherent difference among certain normal donors that may make PBSC mobilization difficult.

Isolation of primary and immortalized CD34-hematopoietic and mesenchymal stem cells from various sources

Based on historical radiation experiments in rodents, the hematopoietic stem cell was defined by its biological properties and later by the expression of certain surface antigens (e.g., CD34), as well as the absence of lineage-specific markers (e.g., DR). Quite recently it was shown that hematopoietic reconstitution can also be achieved by CD34- stem cells, which can be isolated from the bone marrow, peripheral blood and cord blood cells. CD34-stem cells are considered to be predominately part of the quiescent stem cell pool of hematopoietic and mesenchymal stem cells. Due to novel techniques, CD34-stem cells can be expanded on the level of a true stem cell but also directed towards their differentiation into specified tissues or organ systems. This requires the establishment of primary fibroblast-like CD34- stem cells in vitro and their possible reversible and transient immortalization with optimized vector systems.

Therapeutic relevance of CD34 cell dose in blood cell transplantation for cancer therapy

PURPOSE

To review recent advances in peripheral-blood progenitor-cell (PBPC) transplantation in order to define the optimal cell dose required for autologous and allogeneic transplantation.

MATERIALS AND METHODS

A search of MEDLINE was conducted to identify relevant publications. Their bibliographies were also used to identify further articles and abstracts for critical review.

RESULTS

The CD34(+) cell content of a graft is regarded as an accurate predictor of engraftment success. Postchemotherapy autologous PBPC transplantation with >/= 5 x 10(6) CD34(+) cells/kg body weight leads to more rapid engraftment than does transplantation of lower cell doses. Further increases in transplant cell dose further accelerate platelet but not neutrophil engraftment. Evidence that long-term hematopoietic recovery may be more accurately predicted by the subpopulation of primitive progenitors transplanted suggests that the content of CD34(+)CD33(-) and long-term culture-initiating cells in cell collection samples may be important for predicting successful engraftment, particularly in patients with poor mobilization. Allogeneic transplantation has been limited by concerns regarding graft-versus-host disease and the use of hematopoietic growth factors in donors. The risk of graft rejection and engraftment failure after HLA-mismatched allogeneic transplantation may be overcome by intensive chemoradiotherapy and the infusion of large numbers of T cell-depleted hematopoietic stem cells.

CONCLUSION

An optimal cell dose of >/= 8 x 10(6) CD34(+) cells/kg seems to be recommended for autologous PBPC transplantation. This dose facilitates the administration of scheduled chemotherapy on time and reduces the demand for other supportive therapies. A combination of growth factors may enable patients with poor mobilization to achieve a collection sufficient to allow transplantation. The optimum PBPC dose for allogeneic transplantation remains to be defined.

Cost analysis of autologous peripheral stem cell transplantation versus autologous bone marrow transplantation for patients with non Hodgkin's lymphoma and acute lymphoblastic leukaemia

We evaluated the costs of unpurged autologous stem cell transplantation in a non-randomised study of 54 consecutive patients with lymphoproliferative malignancies who have been transplanted at the Nijmegen University Hospital between July 1992 and March 1998. Thirty-five patients were transplanted with autologous peripheral stem cells (APSCT): 30 had non Hodgkin's lymphoma (NHL) and 5 acute lymphoblastic leukaemia (ALL). Nineteen patients were transplanted with autologous bone marrow stem cells (ABMT): 17 had NHL and 2 ALL. The number of progenitor cells (CFU-GM, BFU-E) and nucleated cells was significantly higher in peripheral blood transplants. The duration of cytopenia was shorter after APSCT. The leucocyte recovery to 0.5 x 10(9)/L was 13 days for recipients of peripheral stem cells compared to 20 days for bone marrow recipients (P <0.001). The platelet recoveries to 20 x 10(9)/L were 13 and 29 days, respectively (P = 0.001). This resulted in significantly shorter admission duration 24 days after APSCT versus 30 days (P = 0.003) after ABMT. Furthermore, a statistically significant difference between both groups was observed for antimicrobial costs (mean: fl 2,939 vs fl 4,888; P = 0.008), platelet transfusions (median: 3 vs 7 units; P = 0.01) and erythrocyte transfusions (median: 6 vs 10 units; P = 0.03). The mean overall costs were lower in patients transplanted with stem cells from peripheral blood: fl 34,178 versus fl 43,469 (P = 0.007). This study suggests that the APSCT results in significant cost savings due to shorter hospital stay and less costs of supportive care, despite higher mobilisation costs. The costs of blood transfusions and antimicrobials for patients with ALL were significantly higher when compared to patients with NHL.

Hematopoietic stem/progenitor cell mobilization. A continuing quest for etiologic mechanisms

The physiologic egress of mature hemopoietic cells and of hemopoietic stem/progenitor cells from bone marrow to the circulation are poorly understood processes. Likewise, the mechanism of their enforced emigration or mobilization through the use of several agents has not been unraveled. Although mobilization is suspected to be a multi-step process, involving sequential and/or overlapping changes in adhesion and migratory capacity, a model of molecular hierarchy, like the one governing the extravasation of mature leukocytes to tissues of inflammation, has not been worked out. Understanding the in vivo mechanism of mobilization has been a challenge. Signals emanating from both stromal cells and from hemopoietic cells are likely involved. However, dissecting out their roles, specificity, and interactions has been difficult. Nevertheless insightful information is rapidly emerging, especially with the current availability of many mouse models bearing targeted disruptions of cytoadhesion or signaling molecules.