Increase in endogenous thrombopoietin in healthy donors after automated plateletpheresis

Clonal hematopoiesis in frequent whole blood donors

Healthy volunteer donors are committed to contributing key medical resources. Repeated, regular donation of whole blood represents a specific trigger of hematopoietic stress. Hematopoietic stem cells (HSCs) are known to respond to environmental triggers by altering their differentiation and/or proliferative behavior. This can manifest in long-term changes in the clonal dynamics of HSCs, such as the age-associated expansion of HSCs carrying somatic mutations in genes associated with hematologic cancers-that is, clonal hematopoiesis (CH). A recent study revealed a higher prevalence of CH in frequent donors driven by low-risk mutations in genes encoding for epigenetic modifiers, with DNMT3A and TET2 being the most common. No difference in the prevalence of known preleukemic driver mutations was detected between the cohorts, underscoring the safety of repetitive blood donations. Functional analyses suggest a link between the presence of selected DNMT3A mutations found in the frequent donor group and the responsiveness of the cells to the molecular mediator of bleeding stress, erythropoietin (EPO), but not inflammation. These findings define EPO as one of the environmental factors that provide a fitness advantage to specific mutant HSCs. Analyzing CH prevalence and characteristics in other donor cohorts will be important to comprehensively assess the health risks associated with the different types of donation.

Frequent plateletpheresis donations & its effect on haematological parameters: An observational study

Background & objectives:

The well-being of donors undergoing frequent plateletpheresis has been a matter of concern. The aim of this study was to analyze the effect of frequent plateletpheresis on the haematological parameters (HP) of repeat donors.

Methods:

The study was conducted during February 2016 to March 2017 on all the repeat plateletpheresis donors undergoing the 2^nd plateletpheresis within a month of the first in a tertiary care centre. Donors repeating plateletpheresis 3^rd and 4^th times were also studied. The values of the HP observed on follow up after plateletpheresis done on three different separators were compared.

Results:

HPs of the 98 donors were similar at follow up except mean platelet volume (P<0.05). Of the 98 donors, 35 were followed up within a week and 63 were followed up within 8-30 days. No significant alteration was found in the HPs except a significant difference in the variation of platelet counts of the two groups (P=0.025). In 34 donors who presented 3^rd time for plateletpheresis (mean gap between 1^st and 3^rd plateletpheresis=31 days), no significant differences in the HPs were found except the platelet distribution width (P<0.05). Minimal difference in the HP was found in the baseline and the follow up of 3^rd plateletpheresis i.e., at 4^th plateletpheresis donation. Plateletpheresis through all the three cell separators used had similar effects on the follow up HPs.

Interpretation & conclusions:

Repeated plateletpheresis can be done without any detrimental effects on the cell counts of the plateletpheresis donors. The three cell separators yielded similar post-donation follow up haematological parameters.

Effect of plateletpheresis on postdonation serum thrombopoietin levels and its correlation with platelet counts in healthy voluntary donors

BACKGROUND:

Thrombopoietin (TPO) is regulated by a feedback mechanism between megakaryocytes and platelets. This is important in plateletpheresis donors to compensate for donation-associated platelet loss.

AIMS AND OBJECTIVES:

The aim and objective of this study were to investigate changes in serum TPO levels in healthy plateletpheresis donors and its correlation with platelet recovery pattern.

MATERIALS AND METHODS:

Out of 50 plateletpheresis donors recruited in the study over 1 year, only 29 completed follow-up and were further analyzed. Plateletpheresis procedures were performed on two types of cell separators (TRIMA ACCEL^®, Terumo BCT Lakewood Colorado and AMICUS^®, Fresenius Kabi, Germany). Platelet parameters were estimated pre- and post-platelet donation, at 3^rd- and 5^th-day postdonation. Serum TPO levels were determined using quantitative sandwich enzyme-linked immunosorbent assay technique (Raybiotech, USA) as per the protocol of the manufacturer.

RESULTS:

The majority of donors (72%) in our study were first-time donors. The baseline platelet count was 226 ± 44 × 10³/μl with a significant decline (30%; P < 0.001) in postdonation phase and remained below baseline on the 3^rd and 5^th day. The serum TPO levels increased significantly (P < 0.001) from a baseline of 227.81 (interquartile range [IQR]: 176.06) pg/ml to 269.94 (IQR: 110.68) pg/ml postdonation and remained elevated from baseline levels on the 3^rd and 5^th day. An inverse relation was observed between change in serum TPO levels and platelet count during postdonation phase which was not statistically significant (P > 0.05).

CONCLUSION:

Serum TPO levels increase significantly post plateletpheresis donation corresponding to decrease in platelet counts showing that TPO plays a vital role in compensatory mechanism after platelet loss.

Low-Volume Leukapheresis in Non-Cytokine-Stimulated Donors for the Collection of Mononuclear Cells

Background

There is an increasing demand for products containing mononuclear cells (MNCs) for cellular immune therapy. Hence, leukapheresis is increasingly performed in healthy volunteer donors.

Methods

We evaluated 147 low-volume leukapheresis procedures from 77 healthy non-cytokine-stimulated donors. Complete blood counts (CBCs) of the donors were measured before and directly after the procedures as well as from the MNC products. Follow-up CBCs were collected from donors within 21 days.

Results

The product hematocrit within a range from 1.2 to 6.0% did not correlate with the collection efficiency of any cell population or the granulocyte and platelet yield. There was a strong correlation between the CBC values before leukapheresis and the cell yield of lymphocytes and monocytes as well as a perfect negative correlation between cell recruitment and cell loss in all cell populations. Furthermore, we observed a significant decrease in the CBC values in all cell populations directly after leukapheresis, which recovered within a mean of 16.1 days (SD ± 2.1 days) and even showed a significant increase in granulocytes and platelets.

Conclusion

Low-volume leukapheresis is feasible for the collection of MNCs in which the product hematocrit is negligible for the collection efficiency, cell yield, or contamination of residual cells under operational settings recommended by the manufacturer. Our data suggests that cell recruitment is regulated by the number of cells removed, which may also be the stimulus to induce granulo- and thrombopoiesis within the first days after leukapheresis.

Haemostatic parameters, platelet activation markers, and platelet indices among regular plateletpheresis donors

OBJECTIVE

Plateletpheresis is generally a safe procedure for platelet donation. Studies on the effects of haemostatic parameters and possible association between automated plateletpheresis and hypercoagulable state are limited. Hence, this study aimed to investigate the effects of plateletpheresis on regular donors using haemostatic parameters, i.e. natural anticoagulant proteins, platelet indices, and platelet activation markers.

METHODS

A total of 139 participants (plateletpheresis donors and normal controls) were recruited and divided into two groups: Group 1 participants who underwent tests for haemostatic and platelet indices and Group 2 participants who underwent tests for platelet activation markers using CD62P and PAC-1 monoclonal antibodies.

RESULTS

A significant mild shortening of prothrombin time and platelet activation were demonstrated (by increased CD62P and PAC-1 markers) among regular plateletpheresis donors as compared to healthy controls. The current pre-donation platelet count of plateletpheresis donors was significantly lower than their mean baseline platelet count obtained before their first plateletpheresis procedure. However, no significant differences were observed for the other platelet parameters (platelet count, mean platelet volume, platelet distribution width, activated partial thromboplastin time, protein C, protein S, antithrombin, and von Willebrand Factor antigen) between plateletpheresis donors and healthy controls.

CONCLUSION

This study concludes that regular plateletpheresis is a safe procedure. A possibility of mild platelet activation among regular donors requires further confirmation. However, pre-analytical platelet and FVII activations could occur in vitro contributing to these findings.

Effects of plateletpheresis on blood coagulation parameters in healthy donors at National Blood Centre, Kuala Lumpur, Malaysia

Plateletpheresis is a method used to remove platelet from the body either from random volunteer donors, patient's family members or HLA matched donors. A cross sectional study was carried out on 59 plateletpheresis donors aged between 18 and 55 years at National Blood Center (NBC), Kuala Lumpur. We compared the blood parameters before and after plateletpheresis and we found that the platelet count, FVIII, fibrinogen and thrombophilia markers anti-thrombin (AT), protein C and protein S were significantly reduced (p<0.05) with prolonged PT and APTT. There were significant changes in blood coagulation parameters but it is within acceptable range.

A biomathematical model of human thrombopoiesis under chemotherapy

Intensification of cytotoxic chemotherapy enhances the outcome of several malignancies but is limited by haematotoxicity. While neutropenia and anaemia can be treated with supportive growth factor applications, thrombocytopenia remains a dose-limiting side effect due to the lack of clinically approved pharmaceutical growth factors. Hence, it is necessary to assess the degree of thrombocytopenia of newly designed intensified regimens in the planning phase of a clinical trial. We present a simple ordinary differential equations model of thrombopoiesis under chemotherapy which maps the dynamics of stem cells, CFU-Mk, megakaryocytes and platelets in spleen and circulation. Major regulatory cytokine of thrombopoiesis is thrombopoietin (TPO) whose production and consumption is explicitly modelled. TPO acts by increasing the number of mitoses of CFU-Mk and increasing the mass and maturation of megakaryocytes. Chemotherapy is modelled by a drug-dose and cell-stage specific acute cell loss. Most of the cell kinetic parameters of the model were taken from literature. Parameters regarding TPO regulation and chemotherapy toxicity were estimated by fitting the predictions of the model to time series data of platelets received from large clinical data sets of patients under seven different chemotherapies. We obtained a good agreement between model and data for all scenarios. Parameter estimates were biologically plausible throughout. For validation, the model also explains data of TPO and platelet dynamics after thrombopheresis taken from literature. We used the model to make clinically relevant predictions. Regarding thrombocytopenia we estimated that the CHOP regimen for the treatment of high-grade non-Hodgkin's lymphoma can be time-intensified to a cycle duration of 12 days while the time-intensified CHOEP regimen would result in severe cumulative toxicity. We conclude that our proposed model proved validity for both, different chemotherapeutic regimens and thrombopheresis as well. It is useful to assess the thrombocytopenic risk in the planning phase of a clinical trial.

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.

Complications of donor apheresis

A decreasing blood donor pool in the presence of increasing blood transfusion demands has resulted in the need to maximally utilize each blood donor. This has led to a trend in the increasing use of automated blood collections. While apheresis donation shares many reactions and injuries with whole blood donation, because of the differences, unique complications also exist. Overall, evidence in the literature suggests that the frequency of reactions to apheresis donation is less than that seen in whole blood donation, though the risk of reactions requiring hospitalization is substantially greater. The most common apheresis-specific reaction is hypocalcemia due to citrate anticoagulation, which, while usually mild, has the potential for severely injuring the donor. Other reactions to apheresis donation are uncommon (e.g., hypotension) or rare (e.g., air embolism). More worrisome, and in need of additional study, are the long-term effects of apheresis donation. Recent evidence suggests that repeated apheresis platelet donations may adversely effect thrombopoiesis as well as bone mineralization. Granulocyte donation has also been implicated in unexpected long-term consequences.

Volunteer donor apheresis

Volunteer donor apheresis has evolved from early plasmapheresis procedures that collected single components into technically advanced multicomponent procedures that can produce combinations of red blood cells, platelets, and plasma units. Blood collection and utilization is increasing annually in the United States. The number of apheresis procedures is also increasing such that single donor platelet transfusions now exceed platelet concentrates from random donors. Donor qualifications for apheresis vary from those of whole blood. Depending on the procedure, the donor weight, donation interval, and platelet count must be taken into consideration. Adverse effects of apheresis are well known and fortunately occur in only a very small percentage of donors. The recruitment of volunteer donors is one of the most challenging aspects of a successful apheresis program. As multicomponent apheresis becomes more commonplace, it is important for collection centers to analyze the best methods to recruit and collect donors.

Kinetics of CFU-Mk after automated plateletpheresis

BACKGROUND AND OBJECTIVES

Platelet count, thrombopoetin (TPO) level and the compartment of megakaryocyte progenitor cells (CFU-Mk) are major determinants in the regulation of thrombopoiesis. The aim of this study was to investigate the potential changes in the compartment of CFU-Mk and their correlation with serum TPO levels and platelet count after plateletpheresis.

MATERIALS AND METHODS

Twelve healthy individuals were randomly assigned to undergo single-donor plateletpheresis. A collagen-based in vitro culture system was used to determine the number of peripheral blood (PB) CFU-Mk before and after donation and on days 1, 4 and 7 thereafter. TPO levels were measured by a specific enzyme-linked immunosorbent assay and whole blood counts were performed using an automated cell counter.

RESULTS

The pre-apheresis platelet count (mean +/- SEM: 276 +/- 13 x 10(9)/l) decreased after plateletpheresis to a nadir of 194 +/- 8 x 10(9)/l (P < 0.001), showed a gradual increase on days 1 and 4, and reached pre-apheresis values by day 7 (280 +/- 11). The serum TPO levels were found to be significantly increased on days 1 and 7 as compared to baseline levels (baseline value 103.3 +/- 18.5 pg/ml versus day-1 value 135.8 +/- 25.8 pg/ml and day-7 value 132 +/- 30.19 pg/ml; P < 0.03 and P < 0.03, respectively). The numbers of CFU-Mk in PB were significantly elevated on day 4 only (125 +/- 21 colonies/ml of PB versus pre-apheresis values of 68 +/- 18 colonies/ml of PB, P < 0.005).

CONCLUSIONS

These findings suggest that platelet loss during plateletpheresis affects thrombopoiesis at the progenitor cell level, probably through alterations in TPO plasma concentrations.

The role of the liver in the production of thrombopoietin compared with erythropoietin

The liver plays an important role in the production of haemopoietic hormones. It acts as the primary site of synthesis of erythropoietin (EPO) in the fetal stage, and it is the predominant thrombopoietin (TPO)-producing organ for life. In contrast to that of EPO and other liver proteins, the hepatic synthesis of TPO is influenced little by external signals. Hepatocytes express the TPO gene in a constitutive way, i.e. irrespective of the level of platelets in blood. Megakaryocytes and platelets remove the hormone from blood by means of their high-affinity TPO receptors. Normally, the plasma level of TPO is relatively low ( approximately 10(-12) mol/l). However, in thrombocytopenic states due to marrow failure or bleeding, the concentration of circulating TPO may increase greatly. The simple feedback regulation by TPO and its target cells is efficient in maintaining constant platelet numbers in healthy people. Persisting thrombocytopenia develops only in severe liver or marrow failure. On the other hand, an increase in circulating TPO and interleukin 6 (IL-6) may cause reactive thrombocytosis in inflammatory diseases, including cancer. The indications for recombinant human thrombopoietin (rHuTPO) therapy and its impact on transfusion medicine are still under investigation.

The influence of automated plateletpheresis on systemic levels of hematopoietic growth factors

BACKGROUND

Megakaryocytopoiesis and platelet production are regulated by several hematopoietic growth factors. The present study focuses on the effects of automated plateletpheresis on systemic levels of different hematopoietic growth factors.

STUDY DESIGN AND METHODS

Platelet count, mean platelet volume, and serum levels of thrombopoietin, erythropoietin, interleukin-1beta, interleukin-6, and stem cell factor in 21 healthy donors were measured before platelet collection, after the first half of the apheresis procedure, at the end of apheresis, and on Days 1, 2, and 7 thereafter.

RESULTS

Thrombopoietin levels (initial level: 49.5 +/- 25.5 pg/mL) showed a significant increase between measurements taken at the end of apheresis and Day 1 (56.9 +/- 26.7 pg/mL; p = 0.01). There was a highly significant decrease in stem cell factor levels during apheresis (p<0.0005), reaching preapheresis values (1679 +/- 210 pg/mL) on Day 1. A highly significant increase in erythropoietin levels (initial level: 7.5 +/- 4.0 U/L) was seen after apheresis (p<0.0005 on Days 1 and 2). The level remained significantly elevated until Day 7 (p = 0.004). Interleukin-1beta and interleukin-6 levels (before donation: 1.4 +/- 1.8 pg/mL and 1.1 +/- 0.7 pg/mL, respectively) did not change during the observation period. Thrombopoietin levels correlated consistently and inversely with stem cell factor levels after apheresis (Day 1, r = -0.46, p = 0.035; Day 2, r = -0.50, p = 0.02; Day 7, r = -0.50, p = 0.02).

CONCLUSION

The data show a coordinated response of the hematopoietic system to platelet loss. It is suggested that the decrease in serum stem cell factor levels during apheresis reflects the consumption of stem cell factor by early hematopoietic progenitors that expand to initiate early megakaryocytopoiesis. The temporary increase in thrombopoietin is the result of platelet loss and serves as a stimulus for subsequent thrombopoiesis. The pronounced elevation of erythropoietin after apheresis suggests a role for this primarily erythropoietic cytokine in thrombopoiesis, too.

Endogenous serum levels of thrombopoietic cytokines in healthy whole-blood and platelet donors: implications for plateletpheresis

Serum concentrations of the thrombopoiesis-enhancing cytokines thrombopoietin (TPO), erythropoietin (EPO), interleukin (IL)-6 and IL-11 were determined in 119 healthy whole-blood (WBD) and 101 platelet donors (PD) prior to donation. The 90% TPO reference interval in WBD of 64-867 pg/ml (median 163, 100% range 45-7572) was significantly higher than in PD of 56-524 (median 122, range 44-801, P = 0.004), whereas their platelet counts were lower (P < 0.001). EPO levels were not different (WBD 7.7 +/- 3.8, PD 8.0 +/- 4.9 IU/l), IL-6 and IL-11 were below the detection limit in >/=90% of cases (IL-6 < 3.2 pg/ml, IL-11 < 31.2 pg/ml). None of the cytokines correlated with platelet counts, other blood parameters, or in the PD group with the frequency of platelet donations within the last 6 months. We conclude that plateletpheresis does not lead to a lasting increase of thrombopoietic cytokines and provide reference data for potential platelet mobilization strategies with recombinant growth factors.