Density separation of umbilical cord blood and recovery of hemopoietic progenitor cells: implications for cord blood banking

Neural progenitor cells from human induced pluripotent stem cells generated less autogenous immune response

The breakthrough development of induced pluripotent stem cells (iPSCs) raises the prospect of patient-specific treatment for many diseases through the replacement of affected cells. However, whether iPSC-derived functional cell lineages generate a deleterious immune response upon auto-transplantation remains unclear. In this study, we differentiated five human iPSC lines from skin fibroblasts and urine cells into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with autogenous peripheral blood mononuclear cells (PBMCs), we showed that both somatic cells and iPSC-derived NPCs do not stimulate significant autogenous PBMC proliferation. However, a significant immune reaction was detected when these cells were co-cultured with allogenous PBMCs. Furthermore, no significant expression of perforin or granzyme B was detected following stimulation of autogenous immune effector cells (CD3(+)CD8(-) T cells, CD3(+)CD8(+) T cells or CD3(-)CD56(+) NK cells) by NPCs in both PBMC and T cell co-culture systems. These results suggest that human iPSC-derived NPCs may not initiate an immune response in autogenous transplants, and thus set a base for further preclinical evaluation of human iPSCs.

Low immunogenicity of neural progenitor cells differentiated from induced pluripotent stem cells derived from less immunogenic somatic cells

The groundbreaking discovery of induced pluripotent stem cells (iPS cells) provides a new source for cell therapy. However, whether the iPS derived functional lineages from different cell origins have different immunogenicity remains unknown. It had been known that the cells isolated from extra-embryonic tissues, such as umbilical cord mesenchymal cells (UMCs), are less immunogenic than other adult lineages such as skin fibroblasts (SFs). In this report, we differentiated iPS cells from human UMCs and SFs into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with allologous peripheral blood mononuclear cells (PBMCs), we showed that UMCs were indeed less immunogenic than skin cells to simulate proliferation of PBMCs. Surprisingly, we found that the NPCs differentiated from UMC-iPS cells retained low immunogenicity as the parental UMCs based on the PBMC proliferation assay. In cytotoxic expression assay, reactions in most kinds of immune effector cells showed more perforin and granzyme B expression with SF-NPCs stimulation than that with UMC-NPCs stimulation in PBMC co-culture system, in T cell co-culture system as well. Furthermore, through whole genome expression microarray analysis, we showed that over 70 immune genes, including all members of HLA-I, were expressed at lower levels in NPCs derived from UMC-iPS cells than that from SF-iPS cells. Our results demonstrated a phenomenon that the low immunogenicity of the less immunogenic cells could be retained after cell reprogramming and further differentiation, thus provide a new concept to generate functional lineages with lower immunogenicity for regenerative medicine.

Validation of cord blood split products prepared by an automated method

OBJECTIVES

In this study, we studied whether the contents of the two compartments of automatically processed cord blood (CB) units are comparable with respect to cell counts and viability and therefore suitable for clinical therapy.

BACKGROUND

CB-derived stem cells are increasingly used for allogeneic transplantation. Many centres prepare the transplants by automated methods allowing to split the product into two portions.

METHODS

CB was collected at different sites in Germany and transported to a single centre for processing. Before and after cryopreservation laboratory analyses were performed to compare the quality of the two CB segments.

RESULTS

In total, 33 products were processed [mean collection volume: 18·6 ± 1·2 mL (range 15·2-20·2 mL) segment A; mean: 4·7 ± 0·3 mL (range 4·2-5·2 mL) segment B]. CD34+ cell counts, viability of CD34+ cells and many other haematological parameters showed a good comparibility between the two segments. However, lymphocyte counts and results of clonogenic assays were significantly different between the two segments of the split product.

CONCLUSION

We conclude that the preparation of the cord blood unit by the automated process results in a homogenous distribution of stem and progenitor cells. However, our findings show that the clonogenic capacity differs between the two segments.

Umbilical cord blood cells

The umbilical cord of a healthy neonate contains within it a multipotential treatment for a myriad of diseases and injuries. What was once tossed into the biohazard waste without a second thought is now known to be a goldmine of antigenically immature cells that rival the use of bone marrow for reconstitution of blood lineages. Umbilical cord blood (UCB) is emerging as an effective and feasible clinical treatment as its availability increases and benefits are realized. Basic science research has demonstrated a broad therapeutic capacity ranging from cell replacement to cell protection and anti-inflammation in a number of animal disease and injury models. UCB is easily obtained with no harm to infant or mother and can be stored at cryogenic temperatures with relatively little loss of cells upon thaw. The heterogeneous mononuclear fraction has been identified and characterized and transplanted both locally and systemically to treat animal models of stroke, myocardial infarction, Amytrophic Lateral Sclerosis, San Filippo, spinal cord injury, traumatic brain injury, and age-related neurodegeneration, among others. In the pages to follow, we share protocols for the identification and research use of the mononuclear cell fraction of UCB.

A closed system for the clinical banking of umbilical cord blood

Umbilical cord blood (UCB) is a source of hematopoietic progenitor cells and is used as an alternative to the bone marrow or peripheral blood for treatment of several onco-hematological diseases. Because of the limited number of CD34+ hematopoietic stem cells present in UCB units and of the elevated costs of cryopreservation, it is of paramount importance to select the UCB units that are clinically useful before storage and optimize banking efficiency by designing reliable procedures to process and freeze the selected units. Among the different parameters characterizing UCB, nucleated cell (NC) and CD34+ cell content provides useful criteria to select UCB units since clinical data documented that the infused cell load (both NC and CD34+ cells) plays an important role in the successful outcome of transplants. By evaluating volume, CD34+ cell content, NC total amount, and NC density of 117 UCB units, we found a significant association between CD34+ cell content and NC density and total amount, indicating these parameters as useful to decide UCB clinical utility. Furthermore, we set up a fast procedure to process UCB units for storage. A system for NC separation and volume reduction of UCB samples in a dedicated, germ-free, closed circuit was developed, where plasma and red blood cells (RBC) depletion was obtained by sedimentation in the presence of a 3.5% Polygeline solution. By this separation system, both RBC depletion and high NC and CD34+ cell recoveries were achieved in 60 min, and the yield was comparable to the one obtained by other separation methods. Since Polygeline has been clinically used as a plasma expander and no toxic effects on patients were reported, the protocol can be applied in the large-scale banking of UCB.

Supplementation of conventional freezing medium with a combination of catalase and trehalose results in better protection of surface molecules and functionality of hematopoietic cells

Our previous studies had shown that a combination of the bio-antioxidant catalase and the membrane stabilizer trehalose in the conventional freezing mixture affords better cryoprotection to hematopoietic cells as judged by clonogenic assays. In the present investigation, we extended these studies using several parameters like responsiveness to growth factors, expression of growth factor receptors, adhesion assays, adhesion molecule expression, and long-term culture-forming ability. Cells were frozen with (test cells) or without additives (control cells) in the conventional medium containing 10% dimethylsulfoxide (DMSO). Experiments were done on mononuclear cells (MNC) from cord blood/fetal liver hematopoietic cells (CB/FL) and CD34(+) cells isolated from frozen MNC. Our results showed that the responsiveness of test cells to the two early-acting cytokines, viz. interleukin-3 (IL-3) and stem cell factor (SCF) in CFU assays was better than control cells as seen by higher colony formation at limiting concentrations of these cytokines. We, therefore, analyzed the expression of these two growth factor receptors by flow cytometry. We found that in cryopreserved test MNC, as well as CD34(+) cells isolated from them, the expression of both cytokine receptors was two- to three-fold higher than control MNC and CD34(+) cells isolated from them. Adhesion assays carried out with CB/FL-derived CD34(+) cells and KG1a cells showed significantly higher adherence of test cells to M210B4 than respective control cells. Cryopreserved test MNC as well as CD34(+) cells isolated from them showed increased expression of adhesion molecules like CD43, CD44, CD49d, and CD49e. On isolated CD34(+) cells and KG1a cells, there was a two- to three-fold increase in a double-positive population expressing CD34/L-selectin in test cells as compared to control cells. Long-term cultures (LTC) were set up with frozen MNC as well as with CD34(+) cells. Clonogenic cells from LTC were enumerated at the end of the fifth week. There was a significantly increased formation of CFU from test cells than from control cells, indicating better preservation of early progenitors in test cells. Our results suggest that use of a combination of catalase and trehalose as a supplement in the conventional freezing medium results in better protection of growth factor receptors, adhesion molecules, and functionality of hematopoietic cells, yielding a better graft quality.

A new automated cell washer device for thawed cord blood units

BACKGROUND

The current available techniques to wash out DMSO from thawed umbilical cord blood (UCB) units are based essentially on standard centrifugation in an open system with various degrees of cell loss.

STUDY DESIGN AND METHODS

We evaluated the capacity of a new automated closed device (Cytomate, Baxter, IL) to wash out the DMSO from thawed UCB units, saving at the same time the progenitor and accessory cells in terms of CD34+ cells and MNCs. We modified the standard software of the device and calculated the cell recovery on 25 UCB units. Moreover, we set up a new gas chromatographic method to exactly detect the DMSO removal rate.

RESULTS

To evaluate the efficiency of the Cytomate device, we considered the postthawing (prewashing) versus postwashing cell recovery. The average recovery (%) in terms of total nucleated cells was 63.30 (range, 40.12-89.00), CD34+ cells was 70.20 (range, 11.51-89.01), CD3+ cells was 61.01 (range, 28.80-87.08), CD4+ cells was 62.53 (range, 30.62-96.73), CD8+ cells was 57.4 (range, 26.87-94.72), CD19+ cells was 63.33 (range, 39.10-90.33), CD16+/56+ cells was 70.67 (range, 8.91-98.40), CFU-GM was 74.33 (range, 20.23-98.60), total CFUs was 82.34 (range, 14.83-247.12), and viability was 89.67(range, 70.74-98.30). The total working time required was, on average, 15 minutes (range, 7-20).

CONCLUSIONS

The Cytomate device demonstrated a satisfying efficiency in cell recovery and in maintaining the clonogenic power of the UCB graft. The removal rate of DMSO was practically complete with evident advantages for the recipient. Finally, the entire manipulation performed in a closed system revealed to be safe, maintaining the sterility of the graft.

Cord blood processing with an automated and functionally closed system

BACKGROUND

Umbilical cord blood processing with standard centrifugation techniques is performed in open systems and results in varying cell and volume recoveries.

STUDY DESIGN AND METHODS

Forty umbilical cord blood donations were randomly assigned to processing either with a microprocessor-controlled cell separator equipped with closed disposables or with a manual separation procedure in blood bags. The collection efficiency of nucleated cells, MNCs, RBCs, and CD34+ cells and the processing time were analyzed.

RESULTS

Using the cell processor, mean collection efficiencies were 78.6 +/- 24.9 percent for nucleated cells, 77.4 +/- 27.8 percent for MNCs, 55.5 +/- 14.6 percent for RBCs, and 83.6 +/- 32.5 percent for CD34+ cells, while they were 73.1 +/- 13.2 percent for nucleated cells, 78.1 +/- 14.9 percent for MNCs, 26.0 +/- 12.2 percent for RBCs, and 77.0 +/- 17.6 percent for CD34+ cells when using the standard centrifugation technique. The processing time was about 20 minutes for automated processing and 60 to 80 minutes for the standard centrifugation technique.

CONCLUSION

Using the new cell processor, the collection efficiencies for nucleated cells, MNCs, and CD34+ cells are similar to those obtained by established centrifugation techniques while the RBC reduction is less effective. The main advantages of the new systems are the closed system, the more standardized processing procedure, and a significantly shorter processing time.

Dextran sedimentation in a semi-closed system for the clinical banking of umbilical cord blood

BACKGROUND

The results of current processing procedures for reducing volume and recovering HPCs from umbilical cord blood (UCB) before cryopreservation vary.

STUDY DESIGN AND METHODS

Dextran was added to bags containing UCB, followed by sedimentation for 30 minutes. The processed UCB was then frozen. RBCs, nucleated cells, MNCs, CD34+ cells, CFUs and long-term culture-initiating cells (LTC-ICs), viability, and sterility were evaluated. Fractionations in ficoll-hypaque and hydroxyethyl starch (HES) were also run in parallel for comparison.

RESULTS

The nucleated cell (NC) recovery and RBC depletion were 86.1 percent and 94.3 percent, respectively (n = 50). Sedimentation with dextran also enabled the recovery of 80.7 percent MNCs and 82.6 percent CD34+ cells (n = 30). Postsedimentation samples displayed no impairment of CFU growth (n = 42, 108.7% CFU-C, 104.6% CFU-GEMM, 107% CFU-GM, and 95.7% BFU-E). Long-term cultures on five paired samples before and after sedimentation generated similar numbers of CFU-C each week (p = 0.88). Limiting dilution analysis of 12 paired pre/postsedimentation samples showed comparable median proportions of LTC-ICs (1/6494 vs. 1/5236; p = 0.18). The cell viability of 24 samples of thawed UCB after sedimentation was 90.3 percent (77.5-96%) and the recovery of CFU-C, CFU-GEMM, CFU-GM, and BFU-E of 11 postsedimentation samples was 93.4 percent, 84.9 percent, 92.3 percent, and 83.4 percent, respectively. NC recovery was significantly higher after treatment with dextran than with ficoll-hypaque (n = 30; 88.5% vs. 29.1%; p<0.005) and HES treatment (n = 21; 88.5% vs. 76.4%; p = 0.004). However, MNCs, CD34+ cells, CFUs, LTC-ICs, and RBCs were comparable. Two cycles of dextran sedimentation recovered 93.9 percent of NCs with cell viability of 98.6 percent (96.5-100%), whereas 11.7 percent of RBCs were retained (n = 20). The final yield volume was 33.5 (28-41) mL.

CONCLUSION

In a semi-closed system, dextran sedimentation enabled volume reduction of UCB without significant quantitative and qualitative losses of HPCs.

Endogenous hematopoietic reconstitution induced by human umbilical cord blood cells in immunocompromised mice: implications for adoptive therapy

Human umbilical cord blood (HUCB) cells show promising advantages over bone marrow (BM) cells for a variety of diseases that require transplantation. We observed that lethally irradiated SJL/J mice given a single injection of HUCB cells survive, whereas vehicle-injected mice do not. Because survival is not due to long-term engraftment of HUCB cells, we used this HUCB/mouse model to investigate additional therapeutic benefits of HUCB cells. We investigated the mechanism by which HUCB cells accelerated endogenous hematopoiesis in mice that received either lethal (9.5 Gy) or lower-dose (8.0 Gy) radiation and then were given a single injection of HUCB mononuclear cells. Compared to irradiated control mice, the lethally irradiated, HUCB-injected group showed significant increases in peripheral white blood cell counts, red blood cell indices, and granulocyte-macrophage colony-forming units (CFU-GM) by 3 weeks. In contrast, no significant differences in these parameters were observed between control and HUCB-injected mice that received the lower dose of irradiation. Moreover, regardless of the radiation dose, only HUCB-injected mice exhibited immune responses comparable to those of age-matched normal mice. The clinical relevance of these observations was determined in long-term, culture-initiating cell assays with human BM stem cells and irradiated (gamma-) HUCB cells. CFU-GM colonies were detectable in cultures containing gamma-HUCB cells by day 15, but were undetectable in cultures without gamma-HUCB cells until day 40, suggesting a hematopoietic stimulatory role for HUCB cells. Overall, the results indicate that in addition to their use for transplantation, HUCB cells also may be used as an adjuvant therapy to enhance hematopoietic reconstitution and immunocompetence of the host. This hematopoiesis-enhancing effect represents a heretofore unrecognized function of HUCB cells.

Removal of erythroid cells from umbilical cord blood mononuclear cell preparations using magnetic beads and a monoclonal antibody against glycophorin A

Umbilical cord blood mononuclear cells isolated by density centrifugation are contaminated by erythrocytes and nucleated erythroid precursors which may exceed 50% of the total cell population, and thus interfere with phenotypic, functional and mRNA analyses. Lysis with hypotonic ammonium chloride can overcome this problem, but interferes with lysosomal function and should be avoided when cell preparations are intended for functional studies. The aim of this study was to develop a technique for removing erythroid cells from cord blood mononuclear cell preparations that would be as effective as ammonium chloride lysis but would not affect cellular function. This paper describes a method using 10F7, a mouse monoclonal antibody against human glycophorin A, and magnetic beads coated with anti-mouse immunoglobulin. The population of cord blood mononuclear cells recovered using this technique was of high purity, good yield and viability, and the cells responded appropriately to stimulation in vitro. To maximise cost-effectiveness, purification with magnetic beads could be performed after two density separations to reduce the quantity of beads required.