Collection of large quantities of granulocyte/macrophage progenitor cells (CFUc) in man by means of continuous-flow leukapheresis

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.

Optimization of leukocyte collection and monocyte isolation for dendritic cell culture

Leukapheresis is the method of choice to collect monocytes for dendritic cell (DC) culture. Improvement of cell separators and cell collection software have enabled the collection of 10(9) monocytes for the generation of monocyte-derived DCs, which is sufficient to prepare a DC vaccine series. However, leukapheresis works with the technique of differential centrifugation which is not applicable to selectively collect mononuclear cells of similar density. After leukapheresis, thus, additional preparation steps are required to isolate and enrich the desired monocyte population. The cell isolation and cultivation techniques depend on the quality of the original leukocyte harvest due to the monocyte yield and the content of residual erythrocytes and platelets. Monocyte elutriation from the leukapheresis product shows a high monocyte recovery of 80%. However, only 30% of the isolated monocytes can be developed into mature DCs. The factors responsible for DC maturation and the development of different DC subsets are the subject of current research.

Donor demographic and laboratory predictors of allogeneic peripheral blood stem cell mobilization in an ethnically diverse population

A reliable estimate of peripheral blood stem cell (PBSC) mobilization response to granulocyte colony-stimulating factor (G-CSF) may identify donors at risk for poor mobilization and help optimize transplantation approaches. We studied 639 allogeneic PBSC collections performed in 412 white, 75 black, 116 Hispanic, and 36 Asian/Pacific adult donors who were prescribed G-CSF dosed at either 10 or 16 microg/kg per day for 5 days followed by large-volume leukapheresis (LVL). Additional LVL (mean, 11 L) to collect lymphocytes for donor lymphocyte infusion (DLI) and other therapies was performed before G-CSF administration in 299 of these donors. Day 5 preapheresis blood CD34(+) cell counts after mobilization were significantly lower in whites compared with blacks, Hispanics, and Asian/Pacific donors (79 vs 104, 94, and 101 cells/microL, P < .001). In addition, donors who underwent lymphapheresis before mobilization had higher CD34(+) cell counts than donors who did not (94 vs 79 cells/microL, P < .001). In multivariate analysis, higher post-G-CSF CD34(+) cell counts were most strongly associated with the total amount of G-CSF received, followed by the pre-G-CSF platelet count, pre-G-CSF mononuclear count, and performance of prior LVL for DLI collection. Age, white ethnicity, and female gender were associated with significantly lower post-G-CSF CD34(+) cell counts.

Ancestim (recombinant human stem cell factor, SCF) in association with filgrastim does not enhance chemotherapy and/or growth factor-induced peripheral blood progenitor cell (PBPC) mobilization in patients with a prior insufficient PBPC collection

Up to a third of autologous transplantation candidates fail to mobilize hematopoietic progenitors into the peripheral blood with chemotherapy and/or growth factor treatment, thus requiring innovative mobilization strategies. In total, 20 cancer patients unable to provide adequate PBPC products after a previous mobilization attempt were treated with ancestim (20 microg/kg/day s.c.) and filgrastim (10 microg/kg/day s.c.). In 16 patients, the pre-study mobilization was with filgrastim alone. Eight patients underwent single large volume leukapheresis (LVL) and 12 multiple standard volume leukaphereses (SVL) in both mobilizations. Pairwise comparison of peripheral blood CD34(+) cell concentrations on the day of first leukapheresis failed to document synergism - median CD34(+)/microl of 3.2 (<0.1 to 15.4) and 4.5 (1-28.56) for the pre-study and on-study mobilizations (P = 0.79, sign test), and 4.2 (<0.1-15.4) and 5 (1-28.56), respectively, for the 16 patients previously mobilized with filgrastim alone (P = 1, sign test). The number of CD34(+) cells/kg collected per unit of blood volume (BV) processed was similar in both mobilizations - median 0.1 x 10(6)/kg/BV and 0.09 x 10(6)/kg/BV, respectively (P = 1, sign test). In this phase II study, the combination of ancestim and filgrastim did not allow adequate PBPC mobilization and collection in patients with a previous suboptimal PBPC collection.

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.

Large-volume leukapheresis for peripheral blood stem cell collection in patients with hematologic malignancies

Large-volume leukapheresis (LVL, 15-35 L) was performed in two groups of patients (n = 10) with hematologic malignancies to obtain peripheral blood stem cells for bone marrow rescue following high-dose chemotherapy. The target cell count was 7 x 10(8) mononuclear cells (MNCs = lymphocytes and monocytes) per kg of body weight. Group A patients (n = 4) were studied on Day 1 of LVL, and components were collected from them as four sequential samples. Total MNCs collected averaged 1.29 x 10(10), total colony-forming-units granulocyte-macrophage (CFU-GM) averaged 12.1 x 10(6), and a 1.8-fold mobilization of CFU-GM was observed (p < 0.05, Sample 1 vs. Sample 4). Group B patients (n = 6) were studied throughout the three consecutive planned days of 5-hour LVL. An average of three LVL procedures per patient was performed (range, 1.25-4), and an average of 27 L (range, 24-33) of blood per LVL was processed. The blood:ACD-A ratio was 24:1 with 3000 units of heparin per 500 mL of ACD-A; heparin was also added to the collection bags. The component had an average hematocrit (Hct) of 0.02 and MNC content of 93 percent. The patients' pre-LVL and post-LVL average Hct varied significantly (before Day 1, 0.36 +/- 0.08; after Day 3, 0.28 +/- 0.06; p < 0.05). Platelet counts also decreased, with post-Day 3 counts averaging 19 percent of the average pre-Day 1 counts (p < 0.05). A decrease in the average MNC count after LVL was significant on Day 1 only (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Structure and function of bone marrow hemopoiesis: mechanisms of response to ionizing radiation exposure

It is the purpose of this presentation to review the unique structure and function of bone marrow anchored hematopoiesis in their significance for its response mechanisms to an exposure to ionizing radiation. The ultimate objective of bone marrow hematopoiesis is to maintain in the peripheral blood a constant level of the different blood cell types (erythrocytes, granulocytes, platelets, lymphocytes, etc.). All of them have their particular turnover kinetics (such as granulocytes 120 x 10(9)/d, erythrocytes 200 x 10(9)/d or thrombocytes 150 x 10(9)/d), are semi-autonomous in their steady state regulatory mechanisms and dependent on a life-long supply of mature cells from a stem cell pool with unlimited replicative and pluripotent differentiative potential. The present knowledge of hematopoietic cellular renewal is the result of years of basic experimental and clinical studies using radionuclides in various metabolic forms including (59)Fe, (32)P (DF (32)P), (51)Cr, (131)I, (60)Co, (3)H ((3)HTdR) and (14)C ((14)CTdR). To understand the physiology but in particular the radiation-pathophysiology, it is essential to recognize in detail the infrastructure of the bone marrow as a distinct unit. Indispensable for a life-long cell production is the capsule of the marrow - the bone cortex -, the arterial supply of blood connected to the sinusoidal microvascular architecture with its sinusoids contorti and recti as well as the central (cell collecting) sinusoids. It is further of importance to recognize the significance of nerval regulation of blood flow, characterized by myelinated and unmyelinated nerve fibers. The type of unique lining cells of the sinusoids is the prerequisite for the cell traffic between the hemopoietic parenchyma and the blood. This in turn cannot be achieved without an alternative opening and closing of the sinusoidal segments which - in turn - requires a rigid long capsule to assure an - in toto - constant volume of each bone marrow unit. If a bone marrow unit is exposed to ionizing radiation, a perturbance of the balance between cellular growth pressure and blood flow dynamics can be observed, resulting in a special type of bone marrow hemorrhage and an "excess cell loss" that may result in an non-thrombopenic exhaustion of the stem cell pool. Of great importance is the question as to the mechanisms that allow the bone marrow hemopoiesis to act as one cell renewal system although the bone marrow units are distributed throughout more than 100 bone marrow areas or units in the skeleton. The observation that "the bone marrow" acts and reacts as "one organ" is due to the regulatory mechanisms: the humeral factors (such as erythropoietins, granulopoietins, thrombopoietins etc.), the nerval factors (central nervous regulation) and cellular factors (continuous migration of stem cells through the blood to assure a sufficient stem cell pool size in each bone marrow "sub-unit"). It should be recalled that the bone marrow functions as a physiological chimera and becomes established by the hematogeneic seeding of stem cells to a mesenchymal matrix during embryogenesis. The repopulation of the bone marrow after partial body irradiation, after strongly inhomogeneous radiation exposure or after total body exposure with stem cell transplantation can well be considered as a repetition of the embryogenesis of bone marrow hemopoiesis with the key element of stem cells migrating via the blood to stromal sites of the marrow prepared to accept stem cells to home and start their replication and differentiation if the micro-environmental quality permits. In summary, the radiation biology of bone marrow hemopoiesis requires a thorough understanding of the physiology and pathophysiology of structure, function and regulation not only of the process of cellular renewal but also of the intricate infrastructure.

The role of blood stem cells in hematopoietic cell renewal

It has been the purpose of this keynote address to review available evidence for the notion that the stem and progenitor cells circulating in the peripheral blood play a decisive role in the homeostasis of blood cell formation distributed throughout dozens of bone marrow units in the skeleton. Furthermore, if this notion is correct, one could speculate that the quantity and quality of stem and progenitor cells in the blood should reflect the functional state of the hematopoietic stem cell system throughout the skeletal bone marrow and provide a new tool for the evaluation of alteration in blood cell production. On this basis, the following questions are considered: A) What do we know about the quality and quantity of blood stem cells in steady state conditions? B) In what way do blood stem cells respond to perturbations of the "steady state" of blood cell formation? C) Which role do blood stem cells play during hemopoietic development assuming that the establishment of bone marrow hemopoiesis requires the "seeding" of blood stem cells into an appropriate cellular environment? D) What is the role of blood stem cells in hemopoietic regeneration after partial body irradiation with a small volume of marrow (and hence stem cells) protected? and E) What are the mechanisms and/or kinetics of hemopoietic recovery if stem cells introduced into the circulation were collected from exogenous (autologous or allogeneic) sources? In this review presentation, experimental work of our group and of other members of the scientific community is summarized. It becomes obvious that blood stem and progenitor cells play a key role in hematopoietic homeostasis. Furthermore, their physiology and pathophysiology deserve rigorous experimental studies in order to develop a novel tool in the diagnosis and prognosis of neoplastic and non-neoplastic disorders of blood cell formation.

Large-volume leukaphereses may be more efficient than standard-volume leukaphereses for collection of peripheral blood progenitor cells

To overcome the need for multiple leukaphereses to collect enough PBPC for autologous transplantation, large-volume leukaphereses (LVL) are used to process multiple blood volumes per session. We compared the efficiency of CD34+ cell collection by LVL (n = 63; median blood volumes processed 11.1) with that of standard-volume leukaphereses (SVL) (n = 38; median blood volumes processed 1.9). To achieve this in patients with different peripheral blood concentrations of CD34+ cells, we analyzed the ratio of CD34+ cells collected per unit of blood volume processed, divided by the number of CD34+ cells in total blood volume at the beginning of apheresis. For LVL, 30% (9%-323%) of circulating CD34+ cells were collected per blood volume compared with 42% (7%-144%) for SVL (p = 0.02). However, in LVL patients, peripheral blood CD34+ cells/L decreased a median of 54% during LVL (similar data for SVL not available). The number of CD34+ cells collected per blood volume processed after 4 and 8 blood volumes and at the end of LVL were 0.32 (0.01-2.05), 0.24 (0.01-1.68), and 0.22 (0.01-2.40) x 10(6) CD34+ cells/kg, respectively (p = 0.0007), despite the 54% decrease in peripheral blood CD34+ cells/L throughout LVL. A median 66% decrease in the platelet count was also observed during LVL. Thus, LVL may be more efficient than SVL for PBPC collection, allowing, in most patients, the collection in one LVL of sufficient PBPC to support autologous transplantation.

Haemopoietic cell renewal in radiation fields

Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a "turbulence region" for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a "blood stem cell bank" might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container.

Bone marrow after autologous blood stem cell transplantation and total body irradiation: magnetic resonance and chemical shift imaging

Magnetic resonance studies of the lumbar, pelvic, and femoral bone marrow were performed in 10 patients after autologous blood stem cell transplantation, including total body irradiation and myeloablative chemotherapy. The posttreatment interval varied between 2 and 6 yr. The appearance on T1-weighted images and the quantitative data obtained from chemical shift imaging (relative fat signal) were compared to 10 age-matched healthy volunteers. The classification of the T1-weighted images yielded no significant differences between the two groups. Chemical shift imaging by determination of the relative fat signal was able to detect a significant fatty replacement of the patients' lumbar (p < .002) and pelvic marrow (p < .01), showing the clinically inapparent decreased cellularity of the bone marrow. This difference did not change within the interval of 2-6 yr after transplantation.

Peripheral blood stem cell transplantation

Haematopoietic stem cells are usually sessile within the bone marrow microenvironment. However, small numbers do circulate in the peripheral blood of normal individuals, and following chemotherapy and/or intravenous growth factors, a substantial transient rise in circulating stem cells occurs. Leukocytes harvested by cytapheresis at this time can be used for autologous reconstitution of the haematopoietic and lymphoid systems following high dosage chemo/radiotherapy for the treatment of malignant disease. Peripheral blood stem cell transplants give rise to similar disease response rates as autologous bone marrow transplants, but have the advantage of more rapid haematopoietic reconstitution, and in addition can be offered to patients in whom marrow harvest is not feasible due to bone marrow damage or infiltration. This article reviews the theoretical and historical background to haematopoietic stem cell research, current clinical practice in peripheral blood stem cell mobilisation and harvesting, addresses the potential advantages and disadvantages compared to bone marrow transplantation, and assesses current experience of comparative efficacy.

Increased numbers of circulating haematopoietic progenitor cells after treatment with high-dose interleukin-2 in cancer patients

Immunotherapy with recombinant interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells has been applied to patients with metastatic cancers for its antitumour activity. In the present study we investigated the effects of in vivo administration of IL-2 (3 x 10(6) U/m2/d, continuously i.v.) on haematopoiesis. Six patients with disseminated renal cell carcinoma, treated with IL-2 and LAK cells, were monitored for the numbers of white blood cells and circulating haematopoietic progenitor cells (HPC). During IL-2 treatment lymphopenia developed, followed by lymphocytosis after discontinuation of IL-2 infusions. IL-2 administration also resulted in neutrophilia and eosinophilia. Absolute numbers of circulating HPC declined markedly during IL-2 treatment. However, after completing IL-2 infusions, the numbers of circulating erythroid (BFU-E), myeloid (CFU-GM) and multipotential progenitor cells (CFU-GEMM) strongly increased, reaching a maximum after 5 d (day 10 from the start of IL-2 treatment). This increase did not result from repeated leucaphereses, since patients treated with IL-2 alone showed a similar response. In comparison with pretreatment levels the pool of circulating HPC expanded about 20-fold. This study illustrates that IL-2 treatment has a biphasic effect on the frequency of circulating BFU-E, CFU-GM and CFU-GEMM, causing a decrease during IL-2 infusion, followed by an increase after IL-2 administration. The total number of progenitor cells harvested by four consecutive leucaphereses is in the range that is commonly used for peripheral blood stem cell autografting.

Peripheral blood stem cell autografting

Transplantation of haemopoietic stem cells provides a means whereby patients with malignant disease may be treated with increased doses of chemotherapy or chemoradiotherapy. Until recently, the bone marrow has been the sole source of these cells. However, haemopoietic progenitors can also be demonstrated in the blood and it has been known for more than twenty years that peripheral blood mononuclear cells are capable of repopulating the marrow in animals. This phenomenon has recently been reproduced in man. The use of peripheral blood rather than bone marrow for autologous stem cell rescue may have advantages in terms of ready access, availability in patients with compromised pelvic bone marrows, a lower risk of tumour contamination and more rapid granulocyte and immune recovery. However, clinical experience with peripheral blood stem cell autografting is still very small. This review discusses the characteristics of circulating stem cells, the methods by which they can be collected and stored and the information which has come from recent studies of their transplantation in man.

Isolation of mononuclear leukocytes in a plastic bag system using Ficoll-Hypaque

Mononuclear cells, present in bone marrow and peripheral blood, have been isolated from red cells and granulocytes using a ficoll-hypaque density centrifugation process. Cells isolated by this process which uses centrifuge tubes may become contaminated. In 19 studies in our laboratory we used Ficoll-Hypaque treatment to isolate mononuclear cells from cellular residues obtained during plateletpheresis using a modified 600-ml polyvinyl-chloride (PL-146) plastic bag with the Haemonetics blood processor V-50 or the Fenwal CS-3000 blood processor. The 600-ml PVC plastic bag was modified by sealing its vertical edges using radio frequency to form a narrow bag with a volume of approximately 200 ml. A 125-volume of diluted apheresis cellular residue was collected, and the mononuclear cells were isolated as follows: the diluted cellular residue was layered onto 75 ml of Ficoll-Hypaque with a specific gravity of 1.077 and was centrifuged at 260 g for 30 min at 22 degrees C. The supernatant plasma was removed. The mononuclear cell layer was transferred to a sterile 600-ml transfer bag, and the cells were washed with saline. Of the 4.24 +/- 0.9 X 10(9) mononuclear cells applied to the gradient, approximately 3.73 +/- 0.8 X 10(9) cells were recovered. The recovered cells consisted of 77.3 +/- 8% lymphocytes, 19.0 +/- 7% monocytes, and 3.6 +/- 3% granulocytes. There was no significant difference in tissue culture growth in the CFU-GEMM assay of mononuclear cells whether the plastic tube or the plastic bag system was used. Aerobic bacteriologic cultures were negative. The PL-146 plastic bag system used in this study proved to be a significant aid in isolating mononuclear cells from plateletpheresis residue.

High levels of circulating haemopoietic stem cells in very early remission from acute non-lymphoblastic leukaemia and their collection and cryopreservation

Circulating myeloid progenitor cells (PB CFU-GM) were measured in the peripheral blood of 13 patients with acute non-lymphoblastic leukaemia (ANLL) as they entered first remission. The mean of the recorded peak levels was 2796 X 10(3) CFU-GM/l, representing a 25-fold increase above the mean value in normal subjects. These elevated levels of PB CFU-GM occurred regularly during the very early remission phase when platelet counts rose rapidly. Five of the patients had PB mononuclear cells collected by continuous-flow leukapheresis during this early recovery phase. CFU-GM were assayed as a measure of the number of haemopoietic stem cells in each collection. The cells were concentrated and then cryopreserved in liquid nitrogen. Leukapheresis was also performed on five normal subjects for comparison. Low numbers of CFU-GM were harvested from normal subjects, mean 0.33 +/- 0.06 X 10(4) CFU-GM/kg body weight for each leukapheresis. In ANLL patients entering remission, however, very large numbers of CFU-GM were regularly harvested. A mean of 11 +/- 2 X 10(4) CFU-GM/kg body weight were cryopreserved after each leukapheresis, representing 5 times the number of CFU-GM considered necessary for successful autologous haemopoietic reconstitution. Haemopoietic stem cell viability was assessed after varying periods of cryopreservation. There was no significant stem cell loss after up to 24 months storage. Thus, it is possible to collect and cryopreserve large numbers of CFU-GM and by inference pluripotent haemopoietic stem cells from the peripheral blood of patients with ANLL during very early remission. The possible biological and therapeutic implications are discussed.