Efficient removal of platelets from peripheral blood progenitor cell products using a novel micro-chip based acoustophoretic platform

Background

Excessive collection of platelets is an unwanted side effect in current centrifugation-based peripheral blood progenitor cell (PBPC) apheresis. We investigated a novel microchip-based acoustophoresis technique, utilizing ultrasonic standing wave forces for the removal of platelets from PBPC products. By applying an acoustic standing wave field onto a continuously flowing cell suspension in a micro channel, cells can be separated from the surrounding media depending on their physical properties.

Study Design and Methods

PBPC samples were obtained from patients (n = 15) and healthy donors (n = 6) and sorted on an acoustophoresis-chip. The acoustic force was set to separate leukocytes from platelets into a target fraction and a waste fraction, respectively. The PBPC samples, the target and the waste fractions were analysed for cell recovery, purity and functionality.

Results

The median separation efficiency of leukocytes to the target fraction was 98% whereas platelets were effectively depleted by 89%. PBPC samples and corresponding target fractions were similar in the percentage of CD34+ hematopoetic progenitor/stem cells as well as leukocyte/lymphocyte subset distributions. Median viability was 98%, 98% and 97% in the PBPC samples, the target and the waste fractions, respectively. Results from hematopoietic progenitor cell assays indicated a preserved colony-forming ability post-sorting. Evaluation of platelet activation by P-selectin (CD62P) expression revealed a significant increase of CD62P+ platelets in the target (19%) and waste fractions (20%), respectively, compared to the PBPC input samples (9%). However, activation was lower when compared to stored blood bank platelet concentrates (48%).

Conclusion

Acoustophoresis can be utilized to efficiently deplete PBPC samples of platelets, whilst preserving the target stem/progenitor cell and leukocyte cell populations, cell viability and progenitor cell colony-forming ability. Acoustophoresis is, thus, an interesting technology to improve current cell processing methods.     

Cryopreserving human peripheral blood progenitor cells

High-dose chemotherapy followed by autologous peripheral blood progenitor cell (PBPC) transplantation is used in the treatment of chemosensitive malignancies. Cryopreservation of PBPC in 10% dimethyl sulfoxide (DMSO) has been the standard procedure in most institutions. Infusion of PBPC cryopreserved with DMSO can be associated with toxic reactions such as vomiting, cardiac dysfunction, anaphylaxia and acute renal failure. The grade of toxicity experienced by patients is related to the amount of DMSO present in the PBPC. Cryopreservation with lower DMSO concentrations would be expected to reduce the toxicity. In recent studies done with PBPC cells cryopreserved with 5%, 4% and 2% DMSO, using 10% DMSO as a reference control, CD34+ cells were investigated for preservation of viability, apoptosis, and necrosis. Also preservation of mature colony-forming (CFU) cells, specifically mature myeloid, erythroid progenitors, CFU-megakaryocytes and long-term culture-initiating cells (LTC-ICs) were investigated, using 5% and 10% DMSO as cryoprotectant. All samples were frozen in a rate-controlled programmed freezer and stored in the vapor phase of liquid nitrogen until used. Conclusion: 5% DMSO is the optimal concentration for cryopreserving human PBPC in vitro. Consequently, some hospitals have started using 5% DMSO as cryoprotectant for the autologous PBPC as a standard procedure.     

Effects of long-term cryopreservation on peripheral blood progenitor cells

Background aimsThe long-term stability of cryopreserved peripheral blood progenitor cells is an important issue for patients experiencing disease relapse. However, there is no consensus on how to evaluate the long-term effects of cryopreservation. We describe the effect of cryopreservation on viability and progenitor colony activity from 87 individual samples processed at the Scripps Green Hospital Stem Cell Processing Center (La Jolla, CA, USA).MethodsWe randomly selected 87 peripheral blood hematopoietic stem cell (PBHSC) samples from 60 patients and evaluated the effect of cryopreservation on sample viability and red and white cell colony activity after < 24 h and 7, 10 and 15 years of cryopreservation. Viability was assayed via trypan blue dye exclusion and activity was measured following 14 days of culture.ResultsAn age at collection older than 50 years may result in suboptimal activity and viability following long-term cryopreservation, while gender and disease status had no effect. Cryopreservation did not significantly affect white or red cell activity following 10 years of cryopreservation. However, for samples stored longer than 10 years, viability and activity significantly decreased. We noted a positive association between higher pre-cryopreservation %CD34 count and colony activity.ConclusionsCryopreservation of peripheral blood progenitor cells for up to 10 years results in no loss of clonogenic capacity, as determined by culture activity, although longer durations of storage may affect activity. Until validated methods are developed, cryopreserved grafts should be evaluated based on pre-freeze CD34⁺ cell counts as assayed by flow cytometry, and post-thaw sample evaluation should be reserved for patients identified as poor mobilizers.     

Nycthemeral variations of thyroxine levels in the quail: effect of ambient temperature

Plasma T4 levels were determined at 2 hr intervals in male quail reared under 18 L6-24 : 6D and 26 +/- 1 degrees C. Low thyroxinemia (4.7 -5.7 mg/ml) was observed during the light phase of the photoperiod. T4 levels were sharply increasing during the first part of the dark period, up to a peak (9.2 ng/ml) at 3 a.m., and decreased again by the last part of the night. Exposure to 4 degrees C for 30 min resulted in different effects on thyroxinemia according to the time of the day. During the light phase (i.e., low resting T4 levels), cold- induced thyroxinemia was significantly increased (50% approximately). Similar effects were observed during the last part of the night. On the contrary, no thyroid response to cold could be detected during the beginning of the dark period, when basal thyroxine concentrations were sharply increasing. Participation of feed back mechanisms in such a phenomenon is suggested.U     

Temperature regulation following nickel intoxication in the mouse: effect of ambient temperature

1. The purpose of this study was to examine the interaction between ambient temperature (Ta) and the effects of nickel chloride on the thermoregulatory system of the mouse. 2. Male mice of the BALB/c strain were injected with nickel chloride at dosages of 0, 0.1, 1.0, 2.5, 5.0 and 10.0 mg/kg intraperitoneally and placed in an environmental chamber set at a Ta of either 10, 20, 30 or 35 degrees C for 60 min. Colonic temperature was then measured after one hour of exposure at a given Ta. 3. The thermoregulatory effects of nickel chloride were highly dependent on Ta. Nickel chloride had no effect on body temperature at Ta's of 30 and 35 degrees C. 4. 10 mg/kg dosage of nickel chloride caused a significant reduction in colonic temperature at a Ta of 20 degrees C. At a Ta of 10 degrees C the 5 and 10 mg/kg dosages of nickel chloride caused a significant lowering of body temperature. 5. Using segmented linear regression techniques it was shown that the threshold dose of nickel chloride for causing hypothermia was 9.6 and 3.3 mg/kg at Ta's of 20 and 10 degrees C, respectively. 6. This study has shown that two stressors, low Ta and nickel chloride intoxication, when applied independently have no effect on body temperature; however, when applied simultaneously, they have a significant toxic effect on thermoregulation.     

Different radiosensitive megakaryocytic progenitor cells exist in steady-state human peripheral blood

CD34 antigen is a novel marker for human hematopoietic stem/progenitor cells. In the present study, two cell fractions, CD34low and CD34high, were prepared from steady-state human peripheral blood on the basis of CD34 antigen expression. The colony-forming unit megakaryocytes (CFU-Meg) contained in each cell fraction were compared for X-radiation sensitivity and cytokine action. The content of CD34+CD45+ cells in the CD34low and CD34high cell fractions was 74.8% and 88.8%, respectively, and the frequency of thrombopoietin (TPO)-supported CFU-Meg in the CD34low cell fraction was 1.9 times higher than that in CD34high. The CFU-Meg in CD34high were more radiosensitive than those in CD34low, indicating that steady-state human peripheral blood contains different types of CFU-Meg. However, no significant differences were observed between cell fractions in the radiation survival curves of CFU-Meg stimulated by TPO plus cytokines except granulocyte colony-stimulating factor (G-CSF). TPO plus interleukin 3 was the optimal combination for survival of both types of CFU-Meg after X irradiation. The present study also demonstrated that TPO plus G-CSF is able to increase the survival of irradiated CD34low CFU-Meg. These results suggest that two megakaryocytic progenitor populations with different radiosensitivity and cytokine responses are found in steady-state human peripheral blood.     

Prediction of CD34(+) cell yield in hematopoietic cell products from children by peripheral blood CD34(+) cell counts

Background aimsPeripheral blood stem cells (PBSC) are increasingly used as an alternative to bone marrow in autologous transplantations. In adult patients, the peripheral blood CD34 ⁺ cell count is a good predictor of CD34 ⁺ cell yield in apheresis. However, the determinants of stem cell yield in the pediatric population have not been well established.MethodsWe retrospectively studied 396 apheresis procedures in 301 pediatric patients. Receiver operating characteristic (ROC) curves based on pre-apheresis peripheral blood CD34 ⁺ cell counts were generated to facilitate prediction of the optimal timing of PBSC collection. The associations between CD34 ⁺ cell yield and age and mobilization regimen were analyzed.ResultsSignificant differences in CD34 ⁺ cell yield among different age groups were observed. Furthermore, higher CD34 ⁺ cell yields were obtained in patients receiving chemotherapy as part of the mobilization regimen than those without chemotherapy. A correlation was noted between the CD34 ⁺ cell yield and blood surrogate markers, including white blood cell count, absolute neutrophil count and pre-apheresis peripheral blood CD34 ⁺ cell count. Cut-off values of > 35 CD34 ⁺ cells/μL in patients < 15 years old and > 45 CD34 ⁺ cells/μL in patients ≥ 15 years old were strong predictors of an adequate PBSC collection in one apheresis session. For clinical use, ROC curves and tables were generated to assist advance planning for PBSC collection.ConclusionsThe pre-apheresis peripheral blood CD34 ⁺ cell count is most useful in predicting PBSC yield. Our new cut-off values have better operating characteristics for children than the conventional value of 20 CD34 ⁺ cells/μL used for adults.     

Long-term effects of cryopreservation on clinically prepared hematopoietic progenitor cell products

Background aimsThe question of how long hematopoietic progenitor cells (HPCs) destined for clinical applications withstand long-term cryopreservation remains unanswered. To increase our basic understanding about the stability of HPC products over time, this study focused on characterizing long-term effects of cryopreservation on clinically prepared HPC products.MethodsCryovials (n = 233) frozen for an average of 6.3 ± 14.2 years (range, 0.003–14.6 years) from HPC products (n = 170) representing 75 individual patients were thawed and evaluated for total nucleated cells (TNCs), cell viability, viable CD34+ (vCD34+) cells and colony-forming cells (CFCs). TNCs were determined by use of an automated cell counter, and cell viability was measured with the use of trypan blue exclusion. Viable CD34 analysis was performed by means of flow cytometry and function by a CFC assay.ResultsSignificant losses in TNCs, cell viability, vCD34+ cells and CFC occurred on cryopreservation. However, once frozen, viable TNCs, vCD34+ cells and CFC recoveries did not significantly change over time. The only parameter demonstrating a change over time was cell viability, which decreased as the length of time that an HPC product was stored frozen increased. A significant negative correlation (correlation coefficient = −0.165) was determined between pre-freeze percent granulocyte content and post-thaw percent viability (n = 170; P = 0.032). However, a significant positive correlation was observed between percent viability at thaw and pre-freeze lymphocyte concentration.ConclusionsOnce frozen, HPC products were stable for up to 14.6 years at <−150°C. Post-thaw viability was found to correlate negatively with pre-freeze granulocyte content and positively with pre-freeze lymphocyte content.     

成人外周血内皮祖细胞的分离、扩增及鉴定

目的: 从健康成人外周血中分离获取内皮祖细胞(endothelial progenitor cell ,EPC),并探索EPC体外扩增所需的条件.方法: 密度梯度离心法获取外周血单个核细胞,接种在人纤维连接蛋白包被培养板,用含VEGF的培养液培养7 d,收集贴壁细胞,激光共聚焦显微镜和流式细胞仪鉴定EPC.结果: 从成人外周血可分离获得EPC; 激光共聚焦显微镜可成功鉴定EPC;VEGF和人纤维连接蛋白对该细胞的生长有促进作用.结论: 外周血EPC的分离获取及其体外扩增条件的初步认识,为EPC的进一步研究及临床应用奠定了基础.     

Allogeneic peripheral blood stem cell transplantation

Granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSC) are now widely used instead of bone marrow for autologous transplantation due to earlier hematopoietic recovery after transplant. The low toxicity of G-CSF has prompted phase I and II studies to evaluate PBSC for allogeneic transplantation; these studies have demonstrated that engraftment of neutrophils, red blood cells and platelets is faster with peripheral blood cells compared to marrow. In randomized studies comparing mobilized PBSC and marrow for allogeneic transplantation, most trials have confirmed significantly earlier engraftment with PBSC and similar risks of acute graft-vs.-host disease (GVHD). In some trials, an increase of 10-15% in grade II-IV GVHD has been noted with PBSC. All studies showed a trend towards more chronic GVHD with PBSC. Some randomized studies have shown improved survival and disease-free survival with the use of PBSC due to lowered transplant-related mortality and fewer relapses in recipients of PBSC as a result of improved immune reconstitution and a graft-vs.-leukemia (GVL) effect. This survival benefit is most apparent in patients with more advanced hematologic malignancies, but further studies are needed to define the relative benefits of PBSC for patients with less advanced disease. The GVL effect of PBSC is currently being exploited with the use of non-ablative allografts.     

The effect of ambient temperature on beta-adrenergic responsiveness in rats.

The responses of tail skin and colonic temperatures of female rats to ambient temperatures of 20, 22, 24, 26, 28, and 30 degrees C were measured. Within this range, colonic temperature was stable while tail skin temperature increased linearly with increasing ambient temperature. Administration of the beta-adrenergic agonist, d,l-isoproterenol, at 10.0, 25.0, and 62.5 micrograms/kg, sc, at each ambient temperature was accompanied by increases in tail skin and colonic temperatures that were dependent on both the dose of isoproterenol administered and the ambient temperature. The integrated responses of tail skin temperature following administration of the three doses of isoproterenol were maximal at an ambient temperature of 26 degrees C while the integrated responses of colonic temperature were maximal at 30 degrees C. The results suggest that tests of beta-adrenergic responsiveness using this technique should be performed at an ambient temperature of 26 degrees C for maximal sensitivity.