Early apoptosis in CD34+ cells as a potential heterogeneity in quality of cryopreserved umbilical cord blood

Current and Future Perspectives for the Cryopreservation of Cord Blood Stem Cells

Hematopoietic stem cell (HSC) transplantation is a well-established procedure for the treatment of many blood related malignancies and disorders. Before transplantation, HSC are collected and cryopreserved until use. The method of cryopreservation should preserve both the number and function of HSC and downstream progenitors responsible for long- and short-term engraftment, respectively. This is especially critical for cord blood grafts, since the cell number associated with this stem cell source is often limiting. Loss of function in cryopreserved cells occurs following cryoinjuries due to osmotic shock, dehydration, solution effects and mechanical damage from ice recrystallization during freezing and thawing. However, cryoinjuries can be reduced by 2 mitigation strategies; the use of cryoprotectants (CPAs) and use of control rate cooling. Currently, slow cooling is the most common method used for the cryopreservation of HSC graft. Moreover, dimethyl-sulfoxide (DMSO) and dextran are popular intracellular and extracellular CPAs used for HSC grafts, respectively. Yet, DMSO is toxic to cells and can cause significant side effects in stem cells' recipients. However, new CPAs and strategies are emerging that may soon replace DMSO. The aim of this review is to summarise key concepts in cryobiology and recent advances in the field of HSC cryobiology. Other important issues that need to be considered are also discussed such as transient warming events and thawing of HSC grafts.

Inhibition of ice recrystallization during cryopreservation of cord blood grafts improves platelet engraftment

BACKGROUND

Platelet engraftment following cord blood (CB) transplantation remains a significant hurdle to this day. The uncontrolled growth of ice, a process referred to as ice recrystallization, is one of several mechanisms that lead to cell loss and decreased potency during freezing and thawing. We hypothesized that reducing cell damage induced by ice recrystallization in CB units (CBUs) would reduce losses of stem and progenitor cells and therefore improve engraftment. We previously demonstrated that the ice recrystallization inhibitor (IRI) N-(2-fluorophenyl)-D-gluconamide (IRI 2) increases the postthaw recovery of CB progenitors. Herein, we set out to ascertain whether IRI 2 can enhance platelet and bone marrow engraftment activity of hematopoietic stem cells (HSCs) in cryopreserved CBUs using a serial transplantation model.

STUDY DESIGN AND METHODS

CBUs were processed following standard volume/red blood cell reduction procedure and portions frozen with dimethyl sulfoxide (DMSO) supplemented or not with IRI 2. Thawed CB samples were serially transplanted into immunodeficient mice.

RESULTS

Our results show that supplementation of DMSO with IRI 2 had several beneficial effects. Specifically, higher levels of human platelets were observed in the peripheral blood (p < 0.05; n = 4) upon transplant of CBUs preserved with the IRIs. In addition, human BM chimerism and the number of human CFU progenitors in the bone marrow were superior in IRI 2 recipients compared to DMSO recipients. Moreover, IRI 2 had no negative impact on the multilineage differentiation and self-renewal activities of HSCs.

DISCUSSION

Taken together, these results demonstrate that supplementation of a hematopoietic graft with IRI can improve the postthaw engraftment activities of HSCs.

Comparison and correlation among in vitro and in vivo assays to assess cord blood quality according to delivery temperature and time after collection

Cord blood (CB) has been used as an alternative source for unrelated allogeneic hematopoietic stem cell transplantation. To determine which assay was useful for predicting the successful outcome of CB transplantation, CBs were grouped according to the temperature (4 °C, 24 °C, and 37 °C) and time (24, 48, and 72 h) after collection. The viability, early apoptosis, and colony forming units (CFUs) were ascertained for the total nucleated cells (TNCs) and CD34+ cells; in addition, the engraftment of infused CD34+ cells in NSG mice was determined. The viability of the TNCs and CD34+ cells and total CFUs were significantly decreased whereas the early apoptosis was significantly increased in the 72 h group at 37 °C compared to that of the 24 h group at 24 °C. The viability and early apoptosis of the TNCs correlated with those of CD34+ cells. In addition, the viability and early apoptosis correlated with the number of granulocyte/monocyte progenitor CFUs. In transplanted NSG mice, the frequency of human CD45+ cells decreased in the 72 h group at 24 °C compared to that of the 24 h group at 24 °C and was negatively correlated with early apoptosis of TNCs and CD34+ cells. This study demonstrated that the early apoptosis of TNCs and CD34+ cells constitutes a useful marker for predicting the engraftment of HSCs and may provide helpful data for standard assessment regarding CB quality by analyzing the correlation between in vitro and in vivo assays using NSG mice.

The influence of temperature treatment before cryopreservation on the viability and potency of cryopreserved and thawed CD34+ and CD45+ cord blood cells

BACKGROUND

Hematopoietic stem cell (HSC) viability and potency is crucial for qualified cord blood (CB) transplants. This study analyzes time and temperature condition before cryopreservation for the viability of CD34⁺/CD45⁺ cells after cryopreservation.

METHODS

Cell viabilities were determined by antibody co-staining with 7-aminoactinomycin D detecting necrotic cells, and subsequent flow cytometric analysis. Additionally, Annexin V staining for determination of apoptotic cells and colony-forming unit (CFU) assays for testing functional potency of HSCs were performed.

RESULTS

For all cell types assessed (CD45⁺/CD34⁺ cells, lymphocytes and granulocytes), the highest viabilities were obtained for CB maintained at 4°C or room temperature (RT; 22 ± 4°C) and cryopreserved directly after collection. Starting material were CB units with an age of 24.7 ± 3.5 h after birth. Post-thaw CD34⁺ cell results were > 90% after temperature treatment of t = 24 h (48 h total age) and > 70% after t = 48 h (72 h total age) at 4°C (48 h, 91.4 ± 5.5%; 72 h, 75.0 ± 12.0%) and RT (48 h, 84.2 ± 9.7%; 72 h, 72.6 ± 0.6%). Viabilities for 30°C samples were < 80% after t = 24 h (48 h total age, 79.8 ± 3.1%) and < 50% after t = 48 h of treatment (72 h total age, 46.8 ± 14.3%). Regarding CFU recovery of pre-freeze (without volume reduction) and thawed CB, a trend toward the highest recoveries was observed at 4°C/RT. The difference between 4°C (77.5 ± 12.0%) and 30°C samples (53.9 ± 4.8%) was shown to be significant in post-thaw samples after t = 24 h treatment (48 h total age; P = 0.0341).

DISCUSSION

Delays between collection and cryopreservation should be minimized because increasing time reduces numbers of viable cells and CFUs before/after cryopreservation. CB units should be maintained at 4°C/RT to retain the highest possible potency of the cells after thawing.

Small-Molecule Ice Recrystallization Inhibitors Improve the Post-Thaw Function of Hematopoietic Stem and Progenitor Cells

The success of hematopoietic stem cell transplantation depends in part on the number and the quality of cells transplanted. Cryoinjuries during freezing and thawing reduce the ability of hematopoietic stem and progenitor cells (HSPCs) to proliferate and differentiate after thawing. Up to 20% of the patients undergoing umbilical cord blood (UCB) transplant experience delayed or failed engraftment, likely because of the inadequate hematopoietic potency of the unit. Therefore, the optimization of cryopreservation protocols, with an emphasis on the preservation of HSPCs, is an important issue. Current protocols typically utilize a 10% dimethyl sulfoxide cryoprotectant solution. This solution ensures 70-80% post-thaw cell viability by diluting intracellular solutes and maintaining the cell volume during cryopreservation. However, this solution fails to fully protect HSPCs, resulting in the loss of potency. Therefore, a new class of cryoprotectants (N-aryl-d-aldonamides) was designed and assessed for the ability to inhibit ice recrystallization and to protect HSPCs against cryoinjury. Several highly active ice recrystallization inhibitors were discovered. When used as additives to the conventional cryoprotectant solution, these nontoxic small molecules improved the preservation of functionally divergent hematopoietic progenitors in the colony-forming unit and long-term culture-initiating cell assays. By contrast, structurally similar compounds that did not inhibit ice recrystallization failed to improve the post-thaw recovery of myeloid progenitors. Together, these results demonstrate that the supplementation of cryopreservation solution with compounds capable of controlling ice recrystallization increases the post-thaw function and potency of HSPCs in UCB. This increase may translate into reduced risk of engraftment failure and allow for greater use of cryopreserved cord blood units.

Cord blood collection and processing with hydroxyethyl starch or non-hydroxyethyl starch

BACKGROUND

Collection and processing characteristics influencing quality of cord blood (CB) units play an essential role to cord blood banks (CBBs). At many CBBs, volume reduction is performed using hydroxyethyl starch (HES) and the Sepax (Biosafe) automated cell processing system. Due to the withdrawal of HES from the European market, a validation of the nonHES protocol was performed.

METHODS

This partially retrospective study identified CB characteristics such as gestational age and CB volume/cell count correlated with higher quality. For the nonHES validation, CB was analyzed for total nucleated cell (TNC), mononuclear cell (MNC) recovery, hematocrit (HCT) and colony-forming units (CFUs). Viabilities of CD34(+) and CD45(+) cells were determined by 7-aminoactinomycin D (7-AAD) and AnnexinV (AnnV) staining and compared for 21 mL and 42 mL buffy coat (BC) samples applying the HES/nonHES protocol.

RESULTS

Factors affecting the potency of CB transplants were the gestational age and the volume reduction to a defined BC volume. High initial cell counts and CB volumes correlated negatively with post-processing TNC recovery for lower BC volumes. Post-processing HES and nonHES results were comparable, but nonHES revealed a significantly lower post-thaw recovery of viable CD34(+) cells measured by 7-AAD/AnnV (21 mL: 45.4 ± 16.4%; 42 mL: 67.3 ± 14.5%) as compared with HES (21 mL: 72.7 ± 14.4%, P = 0.0164; 42 mL: 83.4 ± 14.7%, P = 0.0203).

DISCUSSION

Due to the lower post-thaw CD34(+) cell viability (AnnV(-)/7-AAD(-)) for nonHES samples, the use of HES is recommended, ideally combined with a high BC volume. The post-processing HCT has no statistically significant impact on the post-thaw CD34(+) cell viability (AnnV(-)/7-AAD(-)).

Attached Segment has Higher CD34+ Cells and CFU-GM than the Main Bag after Thawing

A contiguous segment attached to the cord blood unit (CBU) is required for verifying HLA types, cell viability, and, possibly, potency before transplantation since such a segment is considered to be representative of the CBU. However, little is known regarding the characteristics of contiguous segments in comparison to main bag units due to the difficulty experienced in accessing a large number of cryopreserved CBUs. In this study, we used 245 nonconforming CBUs for allogeneic transplantation. After thawing the cryopreserved CBU, the number of total nucleated cells (TNCs), CD34+ cells, and CFUs in CB from main bags and segments, as well as cell viability and apoptosis, were examined. The comparative analysis showed that the number of TNCs was significantly higher in CB from main bags, whereas the numbers of CD34+ cells and CFU-GM were significantly higher in CB from segments. While the cell viability of TNCs in segments was higher, the proportion of apoptotic TNCs was also higher. In contrast, no difference was observed between the proportion of apoptotic CD34+ cells in main bags and segments. In the correlation analysis, the numbers of TNCs, CD34+ cells, and CFU-GM in main bags were highly correlated with those in segments, indicating that CB from segments is indeed representative of CB in main bags. Taken together, we conclude that segments have higher CD34+ cells and CFU-GM and lower TNCs than the main cryopreserved bag, although the two compartments are highly correlated with each other.

Postthaw characterization of umbilical cord blood: markers of storage lesion

BACKGROUND

The continued growth in the uses of umbilical cord blood (UCB) will require the development of meaningful postthaw quality assays. This study examines both conventional and new measures for assessing UCB quality after long-term storage.

STUDY DESIGN AND METHODS

The first arm of the study involved thawing UCB in storage for short (approx. 1 year) and long periods of time (>11 years). Conventional postthaw measures (colony-forming units [CFU], total nucleated cell counts, CD34+45+) were quantified in addition to apoptosis. The second arm of the study involved taking units stored in liquid nitrogen and imposing a storage lesion by storing the units in -80°C for various periods of time. After storage lesion, the units were thawed and assessed.

RESULTS

In the first arm of the study, there was little difference in the postthaw measures between UCB stored for short and long periods of time. There was a slight increase in the percentage of CD34+45+ cells with time in storage and a reduction in the number of cells expressing apoptosis markers. When moved from liquid nitrogen to -80°C storage, the nucleated cell count varied little but there was a distinct decrease in frequency of CFUs and increase in percentage of cells expressing both early and late markers of apoptosis.

CONCLUSION

Nucleated cell counts do not reflect damage to hematopoietic progenitors during long-term storage. Expression of caspases and other markers of apoptosis provide an early biomarker of damage during storage, which is consistent with other measures such as CFU and percentage of CD34+45+ cells.

Quality of cord blood cryopreserved for up to 5 years

Background

Although cord blood (CB) is a well-known source of hematopoietic stem cells, uncertainties exist regarding the quality of cryopreserved CB. We investigated the changes in quality of CB units according to the duration of cryopreservation.

Methods

We analyzed CB units that were rejected from the Seoul Metropolitan Government Public Cord Blood Bank inventory after conventional processing, because of unsuitability for allogeneic transplantation. Two hundred CB units that were cryopreserved from 1 year to 5 years were selected. After thawing the cryopreserved CB units, the total nucleated cell (TNC) count, CD34+ cell count, number of colony-forming units (CFU), aldehyde dehydrogenase (ALDH) level, cell viability, and apoptosis were analyzed. We conducted a comparative analysis to identify the presence of statistically significant differences in the recovery rates of the TNC and CD34+ cell counts and to compare the results of ALDH level, the cell viability test, the apoptosis test, and CFU analysis among groups according to the duration of cryopreservation.

Results

The recovery rates of the TNC count, the CD34+ cell count, and cell viability did not differ significantly according to the duration of cryopreservation. ALDH analysis, the cell viability test, and the apoptosis test did not reveal any increasing or decreasing trend according to the duration of cryopreservation. Further, the numbers of CFU-granulocyte/macrophage and CFU-granulocyte/erythrocyte/macrophage/megakaryocyte did not differ significantly according to the duration of cryopreservation.

Conclusion

These results suggest that the quality of CB is not affected by cryopreservation for up to a period of 5 years.

Storage time affects umbilical cord blood viability

BACKGROUND

Cryopreserved umbilical cord blood (CB) is increasingly used as a cell source to reconstitute marrow in hematopoietic stem cell transplant patients. Delays in cryopreservation may adversely affect cell viability, thereby reducing their potential for engraftment after transplantation.

STUDY DESIGN AND METHODS

The impact of delayed cryopreservation for up to 3 days on the viability of both CD45+ and CD34+ cell populations in 28 CB donations with volumes of 58.40 ± 15.4 mL (range, 39.4-107.4 mL) was investigated to establish whether precryopreservation storage time could be extended from our current time of 24 to 48 hours in line with other CB banks. Viability was assessed on 3 consecutive days, both before and after cryopreservation, by flow cytometry using 7-aminoactinomycin D (7-AAD) and annexin V methods.

RESULTS

The results using 7-AAD and annexin V indicated the viability of CD34+ cells before cryopreservation remained high (>92.33 ± 4.11%) over 3 days, whereas the viability of CD45+ cells decreased from 86.36 ± 4.97% to 66.24 ± 7.78% (p < 0.0001) by Day 3. Storage time significantly affected the viability of CD34+ cells after cryopreservation. Using 7-AAD, the mean CD34+ cell viability decreased by approximately 5% per extra day in storage from 84.30 ± 6.27% on Day 1 to 79.01 ± 7.44% (p < 0.0057) on Day 2 and to 73.95 ± 7.54% (p < 0.0001) on Day 3. With annexin V staining CD34+ cell viability fell by approximately 7% per extra day in storage from 77.17 ± 8.47% on Day 1 to 69.56 ± 13.30% (p < 0.0194) on Day 2 and to 62.89 ± 15.22% (p < 0.0002) on Day 3.

CONCLUSION

This study demonstrates that extended precryopreservation storage adversely affects viability and should be avoided.

The Assessment of Parameters Affecting the Quality of Cord Blood by the Appliance of the Annexin V Staining Method and Correlation with CFU Assays

The assessment of nonviable haematopoietic cells by Annexin V staining method in flow cytometry has recently been published by Duggleby et al. Resulting in a better correlation with the observed colony formation in methylcellulose assays than the standard ISHAGE protocol, it presents a promising method to predict cord blood potency. Herein, we applied this method for examining the parameters during processing which potentially could affect cord blood viability. We could verify that the current standards regarding time and temperature are sufficient, since no significant difference was observed within 48 hours or in storage at 4°C up to 26°C. However, the addition of DMSO for cryopreservation alone leads to an inevitable increase in nonviable haematopoietic stem cells from initially 14.8% ± 4.3% to at least 30.6% ± 5.5%. Furthermore, CFU-assays with varied seeding density were performed in order to evaluate the applicability as a quantitative method. The results revealed that only in a narrow range reproducible clonogenic efficiency (ClonE) could be assessed, giving at least a semiquantitative estimation. We conclude that both Annexin V staining method and CFU-assays with defined seeding density are reliable means leading to a better prediction of the final potency. Especially Annexin V, due to its fast readout, is a practical tool for examining and optimising specific steps in processing, while CFU-assays add a functional confirmation.

Effects of telomerase activity and apoptosis on ex vivo expansion of cord blood CD34(+) cells

OBJECTIVE

Ex vivo expansion of CD34(+) cells has become critically important in order to obtain sufficient haematopoietic stem cells for clinical application. Among major regulators involved in ex vivo expansion, telomerase activity and apoptosis have been revealed to be closely linked to cell cycle progression. However, all exact roles remain to be elucidated. Here, change in telomerase activity and level of apoptosis in cord blood (CB) CD34(+) cells were evaluated together with specific cell population growth rate during ex vivo culture.

MATERIALS AND METHODS

CD34(+) cells isolated from human CB were expanded ex vivo over a 28-day period. Besides monitoring cell proliferation kinetics of the CD34(+) cells, changes in telomerase activity and apoptotic levels were investigated. Several relevant genes were quantified by qRT-PCR during the culture period.

RESULTS

Significant elevation of telomerase activity had close relationship to activation of CB CD34(+) cell expansion. Peak apoptotic level was accompanied by a remarkable decline in cell-specific growth rate, and apoptotic level of differentiated CD34(-) population was significantly higher than that of the CD34(+) population.

CONCLUSION

Although telomerase activity was activated during the culture, expansion of CB CD34(+) cells seemed to be more susceptible to apoptotic suppression when cultured ex vivo, which implied that apoptosis may serve as a rate-limiting factor involved in controlling expansion efficiency.

Immunophenotyping of hematopoietic progenitor cells: Comparison between cord blood and adult mobilized blood grafts

AIM

To study the immunophenotype of hematopoietic progenitor cells from cord blood (CB) grafts (n = 39) in comparison with adult apheresis grafts (AG, n = 229) and pre-apheresis peripheral blood (PAPB) samples (n = 908) using flow cytometry analysis.

METHODS

First, we performed a qualitative analysis of CD34+ cell sub-populations in both CB and PAPB grafts using the standardized ISHAGE protocol and a wide panel of 20 monoclonal antibodies. Next, we studied some parameters, such as the age of mothers and the weight of newborns, which can influence the quality and the quantity of CD34+ cells from CB.

RESULTS

We found that the percentage of apoptotic cells was high in CB in comparison to PAPB (PAPB: 4.6% ± 2.6% vs CB: 53.4% ± 5.2%, P < 0.001). In CB, the weight of newborn and the age of the mother have the influence on CD34+ cells. The follow-up of Ag CD133 in the ISHAGE double platform protocol in association with CD45, CD34 and the 7'AAD shows an equal rate between the two cell populations CD133+CD45+CD34+ high and CD34+CD45+ high with a higher percentage. So, is the inclusion of Ac CD133 necessary in the present panel included in the ISHAGE method? Last part, we showed a significant presence of interferon γ in CB in comparison to PAPB, the annexin showing the high number of apoptotic cells in CB.

CONCLUSION

This study demonstrates that many different obstetric factors must be taken into account when processing and cryo-banking umbilical CB units for transplantation.

Increased apoptosis in cryopreserved autologous hematopoietic progenitor cells collected by apheresis and delayed neutrophil recovery after transplantation: a nested case-control study

BACKGROUND AIMS

Delayed neutrophil recovery following autologous hematopoietic stem cell transplantation (aHSCT) increases transplant-related morbidity. Apoptosis induced by cryopreservation and thawing of hematopoietic progenitor cells collected by apheresis (HPC-A) was investigated in this nested case-control study as a factor associated with delayed neutrophil recovery following aHSCT.

METHODS

Among patients with lymphoma who underwent aHSCT between 2000 and 2007 (n = 326), 13 cases of primary delayed neutrophil recovery and 22 age- and sex-matched controls were identified. Apoptosis and viability were measured using multiparameter flow cytometry, and colony-forming capacity was determined using semi-solid methylcellulose assays.

RESULTS

HPC-A grafts from cases and controls had similar percentages of viable mononuclear cells (MNC) and CD34+ progenitor cells, as determined by standard 7AAD dye exclusion methods measured before and after cryopreservation. Patients with delayed neutrophil recovery received increased numbers of apoptotic MNC (P = 0.02) but similar numbers of apoptotic CD34+ cells per kilogram measured after thawing. Apoptosis was more pronounced in MNC compared with CD34+ cells after thawing, and apoptosis was negligible in freshly collected HPC-A products. Patients with delayed neutrophil recovery had fewer total colony-forming unites (CFU) and CFU-granulocyte-macrophages (GM) per 10(5) viable post-thaw MNC compared with controls (P < 0.05).

CONCLUSIONS

Increased numbers of apoptotic MNC in thawed HPC-A products are associated with delayed neutrophil recovery after aHSCT. Studies that address factors contributing to increased apoptosis are needed, and measuring apoptosis in thawed HPC-A may have a role in the assessment of graft adequacy.

Carbohydrate-mediated inhibition of ice recrystallization in cryopreserved human umbilical cord blood

Cryopreservation of human umbilical cord blood (UCB) typically involves the cryoprotectant dimethylsulfoxide (DMSO), however, infusional toxicity and reductions in cell viability remain a concern. Ice recrystallization (IR) is an important source of cryopreservation-induced cellular injury and limits the stem cell dose in UCB units. Carbohydrates have wide-ranging intrinsic IR inhibition (IRI) activity related to structural properties. We investigated the impact of carbohydrate IRI on cell viability, induction of apoptosis and hematopoietic progenitor function in cryopreserved UCB. Mononuclear cells (MNCs) from UCB were cryopreserved in storage media containing specific carbohydrates (200mM) and compared to 5% DMSO. Samples were analyzed under conditions of high IR ('slow' thaw) and low IR ('fast' thaw). Thawed samples were analyzed for viability and apoptosis by flow cytometry and hematopoietic function using colony-forming unit (CFU) assays. IRI of carbohydrate solutions was determined using the 'splat cooling' assay. Greater IRI capacity of carbohydrates correlated with increased yield of viable MNCs (r(2)=0.92, p=0.004) and CD34(+) cells (r(2)=0.96, p=0.019) after thawing under conditions of high IR. The correlations were less apparent under conditions of low IR. Carbohydrates with greater IRI modulate the induction of early apoptosis during thawing, especially in CD34+ cells (r(2)=0.96, p=0.0001) as compared to total mononuclear cells (p=0.006), and preserve CFU capacity in vitro (r(2)=0.92, p=<0.0001). Our results suggest that carbohydrates with potent IRI increase the yield of non-apoptotic and functional hematopoietic progenitors and provide a foundation for the development of novel synthetic carbohydrates with enhanced IRI properties to improve cryopreservation of UCB.

Quality rather than quantity: the cord blood bank dilemma

Growing inventories of cord blood units have facilitated access to umbilical cord cell transplantation for many patients lacking conventional stem cell donors. They are in principle 'off-the-shelf', 'fit-for-use', as well as safe and effective therapy products. Cellular enumeration is used as a surrogate of graft potency, and users rely on the rigorous assessment carried out in banks to avoid poor engraftment after thawing (loss of cells or poor function), when the patient's situation is critical. However, in practice, when units are selected, initially on the basis of HLA matching and cell dose assessment, their absolute quality remains uncertain. Unfortunately, quality-related issues (particularly related to viability) are not uncommon in cord blood transplantation. The reasons for potency failures are diverse, but a lack of thorough validation during critical steps of the process and of appropriate use of quality-control tools for timely detection of problematic units are significant contributors. Moreover, incongruence between different sets of standards and regulations, and lack of common quality systems between banks result in a highly heterogeneous international inventory. Therefore, this complicates the matter for the end user of the product. To ameliorate this situation, it is essential to improve quality at each of the critical manufacturing steps wherein potency can be threatened, thereby creating homogeneous inventories of units with excellent quality and quantity.

Two-way trafficking of Annexin V positive cells between mother and fetus: determination of apoptosis at delivery

OBJECTIVES

The aim of this study was to quantitate apoptosis in maternal circulation and umbilical cord blood (UCB) at delivery. The proportion of fetal cells in maternal blood as well as that of maternal cells in UCB was also determined.

MATERIAL AND METHODS

Three milliliters of peripheral blood was collected from nine women during labor. Five women delivered males and four delivered females. Immediately after delivery, 3 mL UCB was collected. Ten microliters was used to quantitate apoptosis by the ethidium bromide assay (EthBr) and from the remaining blood, Annexin V positive cells were isolated by MACS.

RESULTS

The Median apoptosis rate in maternal samples was 25% (19-34) and in UCB 20% (16-28). Annexin V positive cells were present in all samples analyzed. As shown by Fluorescence in situ hybridization (FISH) in maternal samples, cells with an XY hybridization pattern were identified in cases with male newborns in a median concentration of 1.7% (1.6-2.1). On the corresponding UCB, a median of 1.2% (0.8-1.6) XX cells were detected.

CONCLUSION

The study demonstrates the existence of a bidirectional transfer of fetal and maternal cells under apoptosis across the placenta and provides useful information regarding use of UCB for transplantation.