Description of a closed plastic bag system for the collection and cryopreservation of leukapheresis-derived blood mononuclear leukocytes and CFUc from human donors

Cryopreservation in Closed Bag Systems as an Alternative to Clean Rooms for Preparations of Peripheral Blood Stem Cells

Autologous and allogeneic stem cell transplantation (SCT) represents a therapeutic option widely used for hematopoietic malignancies. One important milestone in the development of this treatment strategy was the development of effective cryopreservation technologies resulting in a high quality with respect to cell viability as well as lack of contamination of the graft.Stem cell preparations have been initially performed within standard laboratories as it is routinely still the case in many countries. With the emergence of cleanrooms, manufacturing of stem cell preparations within these facilities has become a new standard mandatory in Europe. However, due to high costs and laborious procedures, novel developments recently emerged using closed bag systems as reliable alternatives to conventional cleanrooms. Several hurdles needed to be overcome including the addition of the cryoprotectant dimethylsulfoxide (DMSO) as a relevant manipulation. As a result of the development, closed bag systems proved to be comparable in terms of product quality and patient outcome to cleanroom products. They also comply with the strict regulations of good manufacturing practice.With closed systems being available, costs and efforts of a cleanroom facility may be substantially reduced in the future. The process can be easily extended for other cell preparations requiring minor modifications as donor lymphocyte preparations. Moreover, novel developments may provide solutions for the production of advanced-therapy medicinal products in closed systems.

Blood stem cell transplantation: from preclinical to clinical models

This introductory statement to the International Symposium "Ten Years of Blood Stem Cell Transplantation in Heidelberg" provides the opportunity to review the experimental work that was necessary to set the stage for the first successful clinical studies to use blood-derived stem cells to treat hemopoietic and other malignancies. The Ulm University research group used the preclinical canine model to systematically and extensively explore the possibilities and limitations of the therapeutic use of blood-derived hemopoietic stem and progenitor cells. It became clear that blood stem cells are physiological elements of the circulating blood, that their concentration can be drastically increased by chemical and biological means, that they do not lose their function during appropriate cryopreservation, and that they can be "purified" and used successfully to restore hemopoiesis after myeloablative conditioning both in the autologous and allogeneic situation. If compared to fetal liver-derived stem cells, there is excellent experimental evidence that fetal liver-derived stem cells may have even more potential in their ability to restore hemopoiesis, and it is evident that much more experimental work is needed.

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.

Collection and cryopreservation of human stem and progenitor cells for bone marrow transplantation

Bone marrow collection was undertaken from human organ donors (Group 1: n = 7) to develop a closed-system single-step technique for stem and progenitor cell enrichment, using the Cobe 2997 continuous-flow blood-cell separator. The effects of programmed freezing, storage in liquid nitrogen, and thawing were then defined using these grafts. Once standardised, this method was extended to autografting following cryopreservation of a comparable fraction (Group 2: n = 8) and then to allogeneic transplantation after ex vivo exposure to the lytic monoclonal antibody. Campath-1 IgM and human complement, but without cryopreservation (Group 3; n = 9). The median number of mononuclear cells harvested was 5.0 x 10(6)/mL (n = 24), and this was not significantly different in the three groups. The ex vivo graft, composing marrow rich anticoagulated whole blood, was recirculated in the separator at a flow rate of 60 mL/minute, with a centrifuge speed of 1,100 r.p.m., and the mononuclear cell fractions were collected at the rate of 1.5 mL/minute. The average procedure time from formation of the interface in the single disposable channel to achievement of the final volume was 90 minutes. The mean recovery of the mononuclear cells was 101.4% (SD 38.0) and the GM:CFUc was 91% (SD 43.86). These figures were not significantly influenced by subsequent cryopreservation (Group 1; n = 7 and Group 2; n = 8) or following exposure to the monoclonal antibody. Campath-1 IgM (Group 3; n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Density distribution of hematopoietic progenitor cells and T lymphocytes from peripheral blood: heterogeneity of the human population

Density gradient centrifugation has been used in animal systems to purify stem cells and eliminate T lymphocytes prior to allogeneic transplantation. There is substantial disagreement whether the same approach can be used to purify hematopoietic stem cells obtained from human peripheral blood. The purpose of the present study was to resolve that issue by determining the density distribution of 4 classes of human leucocytes: total mononuclear cells, T lymphocytes, CFUc, and BFUe. To ensure a representative sampling, a large number of randomly selected donors were analyzed. The results show that most T lymphocytes band between 1.068 and 1.071 g/ml, with relatively little variation from individual to individual. In contrast, the density distributions of both CFUc and BFUe fluctuated markedly from donor to donor. As a consequence, there was significant variability in the degree of progenitor-T cell separation. The implications of these results for clinical application of the density separation technique are discussed.

Autologous transplantation with circulating hemopoietic stem cells

Circulating stem cells exist in sufficient numbers in mouse, dog, and man to allow collection and transplantation after ablative treatment. Preclinical studies in the mouse have shown a low concentration, with a transplantation potential ratio of bone marrow to blood of 1:100. The ratio of circulating stem cells to bone marrow stem cells is more favorable in the dog (1:10-20). Recent pilot studies carried out in different centers with 10 patients have shown that this approach is feasible in man, too. It appears that 5 X 10(8) mononuclear cells/kg of body weight collected by seven or eight leukapheresis procedures of about 4 hrs each is sufficient for fast hemopoietic recovery after marrow ablative treatment. Potential advantages of the use of blood stem cells over bone marrow stem cells are the decreased likelihood of contamination with malignant cells, the avoidance of general anesthesia, and the infusion of immunocompetent cells, which might hasten immunorecovery in the autologous setting.

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.

Bone marrow structure and its possible significance for hematopoietic cell renewal

The authors review the progress made during the last quarter of a century in the fields of hematopoietic cellular proliferation and differentiation in relation to the bone marrow structure and the microenvironment provided by the marrow stroma in which unlimited self-renewal occurs. The marrow is conceived of as an organ in which the stroma originates from local mesenchymal elements which form a vascularized and innervated matrix, seeded later by blood-borne stem cells. Transplantation studies using total-body-irradiated dogs show that stem cells derived from the marrow, as well as those from the blood and from the fetal liver, are able to repopulate a marrow rendered aplastic by irradiation. By grafting equal numbers of GM-CFU from peripheral blood and bone marrow, a faster hemopoietic reconstitution is provided by blood-derived stem cells. The most efficient stem cells in the long range are those derived from fetal liver. Bone marrow and peripheral blood GM-CFU differ in some in vitro characteristics such as radiation sensitivity. These peripheral blood cells are more radiosensitive than those derived from the marrow. Autografting of bone marrow mononuclear cell fractions obtained by velocity sedimentation techniques demonstrates that the fraction of small mononuclear cells holds a repopulating potential similar to that of circulating blood stem cells. The cells collected in fraction 2 of a discontinuous albumin gradient contain most of the blood stem cells and repopulate the marrow without causing GVHD, while cells collected in fractions 3 and 4 contain a minimal amount of stem cells and cause severe GVHD.

Cryopreservation of human platelets and bone marrow and peripheral blood totipotential mononuclear stem cells

Human platelets in sufficient numbers for a therapeutic transfusion can be collected for preservation either by pooling ABO- and Rh-compatible platelets or by apheresis procedures using mechanical cell-separating machines. Human platelets have been frozen successfully with 5 or 6% dimethyl sulfoxide (DMSO) and stored at -150 or -180 degrees C, respectively. Platelets frozen with 5% DMSO have been stored at -150 degrees C for at least 3 years, and platelets frozen with 6% DMSO have been stored at -80 degrees C for at least 2 years. Approximately 95% of the DMSO usually is removed by washing the platelets after thawing, and the residual DMSO produces no untoward effects. Washed platelets resuspended in plasma can be stored at room temperature for 6 to 8 hr before transfusion. Platelets thus frozen have freeze-thaw-wash recovery values of about 80%. In vivo survival values are only about 50% those seen with fresh platelets, and it is necessary to transfuse twice as many to achieve comparable results. Studies have shown that these platelets have satisfactory circulation, reduce clinical bleeding, and shorten the prolonged bleeding times associated with thrombocytopenia. Studies are now being made on human bone marrow and peripheral blood, from which totipotential cells devoid of immunocompetent cells can be isolated and frozen.

Studies of cell separation: a comparison of the osmotic response of human lymphocytes and granulocyte-monocyte progenitor cells

The feasibility of using hypo- or hypertonic stress to selectively destroy lymphocytes while sparing stem cells was investigated. Lymphocytes were isolated from peripheral blood and exposed to Hanks' balanced salt solutions ranging in concentration from 66 to 2700 mOsm. The Boyle-van't Hoff plot of cell volume versus reciprocal osmolality was linear. Following osmotic stress, viabilities of the lymphocytes and the granulocyte-monocyte progenitor cells (CFUc) were determined. Lymphocyte viability was assessed by tritiated thymidine incorporation following mitogen stimulation. CFUc viability was measured with the soft agar colony assay. Both types of cells were found to possess high osmotic tolerances compared to other blood cells. While progenitor cells in general appeared to survive anisotonic exposure somewhat better than lymphocytes, significant statistical differences were not established for most situations. The highest degree of CFUc enrichment was twofold, but there was a concomitant 50% drop in CFUc survival. These results suggest that osmotic stress is not a useful procedure for the separation of peripheral blood lymphocytes and stem cells.

Collection, storage, and use of hematopoietic stem cells from peripheral blood

Complete hematopoietic reconstitution using nonleukemic peripheral blood mononuclear cells has yet to be achieved in humans. Significant advances have been made in in vitro quantification of putative stem cells, in animal models of the reconstitutive process, and in the collection, processing, and storage techniques for stem cell preparations. These may eventually lead to use of hematopoietic stem cells from peripheral blood for both allogeneic and autologous bone marrow reconstitution in a variety of clinical situations.

Autologous transplantation of a bone marrow graft manipulated by chemoseparation to eliminate residual tumor cells

An autologous bone marrow transplantation (ABMT) was performed in a 45-year-old male patient with AML in therapy-resistant first relapse including CNS-disease. The marrow graft was harvested 18 months before, at the beginning of first remission, and was subjected to an in-vitro incubation with 4-hydroperoxycyclophosphamide (4-HC) prior to cryopreservation to eliminate residual clonogenic tumor cells. After myeloablative therapy with high-dose Cyclo-phosphamide (CY), total body irradiation (TBI) and intrathecal application of Methotrexate (MTX), the manipulated marrow graft was reinfused. The myelopoietic reconstitution started already 6 days after ABMT and was completed 40 days thereafter. There is evidence for a complete remission in marrow and spinal fluid observed over a period of 4 months.

4-hydroperoxycyclophosphamide: a model for eliminating residual human tumour cells and T-lymphocytes from the bone marrow graft

Autologous bone marrow transplantation in acute leukaemia carries the risk of relapse from reinfusion of tumour cells present in marrow collected in remission and cryopreserved. An effective method for clearing marrow of tumour cells is required for a successful outcome. In the animal model 4-hydroperoxycyclophosphamide (4-HC) has proved to be effective in eliminating tumour cells from an autologous marrow graft. In the present studies, the in vitro effect of short- and long-term marrow cell incubation with 4-HC on haemopoietic stem cells was investigated to determine the maximum concentration of 4-HC that can be used for in vitro incubation without destroying the capacity of the marrow to effect complete haematological recovery as judged by residual CFUc content. However, loss of CFUc may not necessarily parallel survival of pluripotential stem cells. 4-HC was also shown to be effective against peripheral T-lymphocytes. Its possible therapeutic use in preventing or ameliorating graft-versus-host disease in allogeneic marrow grafts by preincubation with 4-HC prior to transplantation is discussed.

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

Continuous-flow leukapheresis using the AMINCO Celltrifuge was performed in 35 adult volunteers for the procurement of large quantities of granulocyte/macrophage progenitor cells (CFUc) as part of the mononuclear leucocytes. The donor blood volume processed was 12 1 at a flow rate of 50 ml per min. The centrifuge speed was 800 rpm. The mean yield of mononuclear cells (MNC) per run was 12.0 x 10(9) and that of CFUc, 8.7 x 10(5). The leukapheresis did not much affect the donor blood cell concentration except the platelet concentration; this must be considered as a limiting factor for leukapheresis. The mean granulocyte contamination of the leukapheresis-derived leucocytes was only about 10%. Successive leukaphereses (with short-term intervals) in 7 donors led to significant increases in CFUc yield. The possible therapeutic application of blood stem cells in the treatment of haemopoietic failure in man is discussed.