Cord blood transplantation for adults

3-deazaadenosine (3DA) alleviates senescence to promote cellular fitness and cell therapy efficiency in mice

Cellular senescence is a stable type of cell cycle arrest triggered by different stresses. As such, senescence drives age-related diseases and curbs cellular replicative potential. Here, we show that 3-deazaadenosine (3DA), an S-adenosyl homocysteinase (AHCY) inhibitor, alleviates replicative and oncogene-induced senescence. 3DA-treated senescent cells showed reduced global Histone H3 Lysine 36 trimethylation (H3K36me3), an epigenetic modification that marks the bodies of actively transcribed genes. By integrating transcriptome and epigenome data, we demonstrate that 3DA treatment affects key factors of the senescence transcriptional program. Remarkably, 3DA treatment alleviated senescence and increased the proliferative and regenerative potential of muscle stem cells from very old mice in vitro and in vivo. Moreover, ex vivo 3DA treatment was sufficient to enhance the engraftment of human umbilical cord blood (UCB) cells in immunocompromised mice. Together, our results identify 3DA as a promising drug enhancing the efficiency of cellular therapies by restraining senescence.

Osteogenic Commitment of MSC Is Enhanced after Interaction with Umbilical Cord Blood Mononuclear Cells In Vitro

The effectiveness of stroma-dependent expansion of hematopoietic cells ex vivo may depend on the level of commitment of multipotent mesenchymal stromal cells (MSC). Markers of MSC osteodifferentiation and the level of soluble hematopoiesis regulators were determined during their interaction with umbilical cord blood mononuclears. After 72-h co-culturing, an increase in the expression of ALPL and alkaline phosphatase activity was revealed. In conditioned medium of co-cultures, the levels of osteopontin and osteoprotegerin were elevated and the levels of osteocalcin and sclerostin were reduced. Co-culturing of umbilical cord blood mononuclears with osteocommitted MSC was accompanied by more pronounced increase in the concentration of both positive (GM-CSF and G-CSF) and negative (IP-10, MIP-1α, and MCP-3) regulators of hematopoiesis. Thus, umbilical cord blood mononuclears induced the formation of early osteogenic progenitor phenotype in MSC ex vivo, providing the microenvironmental conditions necessary to support hematopoiesis. Preliminary osteocommitted MSC were more sensitive to the effect of umbilical cord blood mononuclears.

Prenatal selection of cord blood donors according to the estimated fetal weight percentile and new approaches; results of a prospective cohort study

BACKGROUND

Umbilical cord blood (UCB) donation is becoming inefficient and we recently proposed the estimated fetal weight percentile (EFWp) ≥60th as a predictor for a prenatal selection of donors. The aim of this study is to prospectively validate this and to identify new potential prenatal predictive parameters.

STUDY DESIGN AND METHODS

Prospective cohort study of low-risk pregnancies undergoing third trimester ultrasound, whose UCB was collected at delivery (2016-2018) and compared with a historical cohort (2013-2016, N = 869). Several ultrasound parameters (EFWp, amniotic fluid, Doppler evaluation, placental thickness) were assessed ultrasound and perinatal data were collected. The association with standard of high quality of UCB was assessed by logistic regression analysis.

RESULTS

Among 297 cases, 161 (54%) were selected according to the EFWp ≥60th for UCB units' collection. Cellular criteria for banking was achieved in 27 cases (16.8%), with an average increase of 1.7 times compared to the historical cohort (9.8%, P = .009). Selecting donors according to the 60th EFWp resulted in a higher probability of collecting clinical suitable UCB (P = .025). Among prenatal and perinatal parameters, EFWp, amniotic fluid, umbilical vein (UV) velocity, newborn weight and percentile and placental weight were significantly associated with a higher cellular content. At logistic regression analysis, significant contributors of UCB collection, were EFWp at 37-38 weeks ultrasound (OR 1.04; 95% CI: 1-1.08; P = .042) and UV velocity (OR 1.14; 95% CI: 1-1.29; P = .037).

CONCLUSION

The evaluation of the EFWp equal or above 60 and the increased UV velocity can result in higher efficiency of public UCB donation programs.

Nov/CCN3 Enhances Cord Blood Engraftment by Rapidly Recruiting Latent Human Stem Cell Activity

Umbilical cord blood (UCB) has had considerable impact in pediatric stem cell transplantation, but its wider use is limited in part by unit size. Long-term ex vivo culture offers one approach to increase engraftment capacity by seeking to expand stem and progenitor cells. Here, we show brief incubation (8 h) of UCB CD34+ cells with the matricellular regulator Nov (CCN3) increases the frequency of serially transplantable hematopoietic stem cells (HSCs) 6-fold. This rapid response suggests recruitment rather than expansion of stem cells; accordingly, in single-cell assays, Nov increases the clonogenicity of phenotypic HSCs without increasing their number through cell division. Recruitment is associated with both metabolic and transcriptional changes, and tracing of cell divisions demonstrates that the increased clonogenic activity resides within the undivided fraction of cells. Harnessing latent stem cell potential through recruitment-based approaches will inform understanding of stem cell state transitions with implications for translation to the clinic.

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NOV rapidly increases the number of functional HSCs in a single cord blood unit

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This is by direct recruitment without expansion or self-renewal ex vivo

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NOV reduces C-MYC and ROS but increases glycolytic enzymes in HSCs

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Manipulating non-dividing stem cells can alter their state and functional potential

Estimated fetal weight percentile as a tool to predict collection of cord blood units with higher cellular content: implications for prenatal selection of cord blood donors

BACKGROUND

The need for high-cellular-content cord blood units (CBUs) for allogenic transplantation is evident to improve clinical outcomes. In our environment and with current donation programs, very few collected units meet suggested clinical thresholds, making collection programs highly inefficient. To increase the clinical conversion rate, we have assessed factors influencing the cellular content of the cord blood collection and established the estimated fetal weight percentile (EFWp) as a tool to predict which deliveries will obtain higher cellular counts.

STUDY DESIGN AND METHODS

We conducted a retrospective analysis of 11,349 collected CBUs. An analysis of diagnostic efficiency (receiver operating characteristic [ROC] curve) was performed to establish the cutoffs of several obstetric and perinatal variables from which we would obtain more than 1500 × 106 total nucleated cells and 4 × 106 CD34 cells. We then calculated the optimal EFWp cutoff to increase efficiency.

RESULTS

In the univariate analysis, factors positively and significantly associated were a greater neonatal and placental weight and longer weeks of gestation. In the multivariate analysis only neonatal and placental weight remain significant (p < 0.001). The ROC curve analysis showed that the optimal EFWp cutoff is 60, which has the maximum area under the curve. Applying this, donations meeting clinical cellular numbers will increase more than 30% with respect to not using any threshold.

CONCLUSION

The EFWp predicts the quality of the collected CBUs and can be used to make a prenatal selection of the donors, therefore increasing the efficiency of umbilical cord blood collection programs.

Mesenchymal stromal cells' role in tumor microenvironment: involvement of signaling pathways

Mesenchymal stromal cells (MSCs) are adult multipotent stem cells residing as pericytes in various tissues and organs where they can differentiate into specialized cells to replace dying cells and damaged tissues. These cells are commonly found at injury sites and in tumors that are known to behave like " wounds that do not heal." In this article, we discuss the mechanisms of MSCs in migrating, homing, and repairing injured tissues. We also review a number of reports showing that tumor microenvironment triggers plasticity mechanisms in MSCs to induce malignant neoplastic tissue formation, maintenance, and chemoresistance, as well as tumor growth. The antitumor properties and therapeutic potential of MSCs are also discussed.

Comparison of cyclosporine and tacrolimus combined with mycophenolate mofetil in prophylaxis for graft-versus-host disease after reduced-intensity umbilical cord blood transplantation

Umbilical cord blood transplantation with a reduced-intensity conditioning regimen (RIC-UCBT) is used increasingly in patients who have comorbid organ functions and lack human leukocyte antigen-identical donors. We compared the outcomes in 35 patients who received mycophenolate mofetil plus cyclosporine (MMF/CSP, n = 17) or MMF plus tacrolimus (MMF/TAC, n = 18) for graft-versus-host disease (GVHD) prophylaxis after RIC-UCBT. Cumulative incidence of neutrophil engraftment was 94 and 89 % in MMF/CSP and MMF/TAC groups, respectively (p = 0.34). The incidence of pre-engraftment immune reaction did not differ between the MMF/CSP (41 %) and MMF/TAC (39 %, p = 1.00) groups; however, patients in the MMF/TAC group tended to have a lower incidence of grade II-IV acute GVHD than those in MMF/CSP group (28 vs 53 %, p = 0.11). Overall survival (OS) at 1 year was 43 and 60 % in MMF/CSP and MMF/TAC groups, respectively (p = 0.39). Progression-free survival, non-relapse mortality, and relapse rate were comparable between the two groups (p = 0.76, 0.59, and 0.88, respectively). In multivariate analyses, MMF/TAC GVHD prophylaxis was closely associated with improved OS, but not with incidence of engraftment and acute GVHD. These results suggest that more intensive GVHD prophylaxis with MMF/TAC decreased acute GVHD without affecting other clinical outcomes, resulting in improved OS after RIC-UCBT.

Four phases of checks for exclusion of umbilical cord blood donors

AIM

The aim of this study was to analyse umbilical cord blood (UCB) collection over 1 year between October 2008 and September 2009, seeking ways to improve the number of suitable banked UCB units. Four phases of the process were investigated, from the consent form to the banking procedure, paying attention to the discarded UCB units.

MATERIAL AND METHODS

We recruited couples at 35 weeks of gestation and took an accurate history, focusing on genetic, immunological and infectious diseases. We collected UCB from pregnant women who delivered vaginally or by Caesarean section between the 37-41(+6) weeks of gestation. Some units were discarded on the basis of the patients' history, obstetric events or biological criteria. In utero collection was the preferred method of collection.

RESULTS

During the study period, between October 2008 and September 2009, there were 1,477 deliveries in our unit. The number of couples interested in UCB donation was 595 (40.2%-595/1,477). We collected 393 UBC units. We excluded 122 patients at the phase of the history taking, counselling and informed consent (first phase check). Of the 393 units collected, 162 (41.3%) were banked whereas 231 (58.7%) were discarded because they did not fulfil biological criteria (third phase check). The volume of UCB units collected after Caesarean section was greater than the volume of units collected after vaginal delivery (95.4 mL versus 85.0 mL, respectively; p <0.01). The UCB units collected after vaginal delivery contained a higher number of total nucleated cells compared to the units collected after Caesarean section (970x10(6) cells versus 874x10(6) cells, respectively; p=0.037). None of the banked UCB units was discarded at the clinical check 6 months after delivery (fourth phase check).

CONCLUSIONS

Our study shows that strict observance of each of the checks and the collection strategy is important to guarantee the safety of the UCB units and to maximise the cost-benefit ratio. After the appropriate checks we banked UCB units from only 27.2% (162/595) of the couples who gave consent to the procedure and from only 11% (162/1,477) of all the deliveries in the 12 month study period, as 59.8% of couples were not properly informed about UCB donation.

Enhanced engraftment of a very low-dose cord blood unit in an adult haemopoietic transplant by addition of six mismatched viable cord units

The report describes the feasibility of the addition of multiple viable HLA-mismatched unrelated cord blood units, to a low cell number matched unrelated cord, to assist clinical engraftment. An ablative stem cell transplant was performed in an adult with relapsed acute lymphoblastic leukaemia (ALL), using a single HLA-matched cord blood unit (mononuclear cell dose 0.8 × 10⁷), supported by six mismatched cord blood units (one unit per 10 kg recipient weight). No adverse reaction occurred following the infusion of mismatched units and engraftment of the suboptimal-dose matched unit occurred rapidly, with no molecular evidence of engraftment of mismatched cords. Early molecular remission of ALL was demonstrated using a novel PCR for a mitochondrial DNA mutation in the leukaemic clone. The cell dose of the matched cord was well below that recommended to engraft a 70 kg recipient. We suggest that a factor or factors in the mismatched cords enhanced/supported engraftment of the matched cord.

Role of Chk1 in the differentiation program of hematopoietic stem cells

Hematopoietic stem cells (HSC) isolated from umbilical cord blood (UCB) were treated with ionizing radiation (IR) and sensitivity and IR induced checkpoints activation were investigated. No difference in the sensitivity and in the activation of DNA damage pathways was observed between CD133+ HSC and cells derived from them after ex vivo expansion. Chk1 protein was very low in freshly isolated CD133+ cells, and undetectable in ex vivo expanded UCB CD133+ cells. Chk1 was expressed only on day 3 of the ex vivo expansion. This pattern of Chk1 expression was corroborated in CD133+ cells isolated from peripheral blood apheresis collected from an healthy donor. Treatment with a specific Chk1 inhibitor resulted in a strong reduction in the percentage of myeloid precursors (CD33+) and an increase in the percentage of lymphoid precursors (CD38+) compared to untreated cells, suggesting a possible role for Chk1 in the differentiation program of UCB CD133+ HSC.

The Mannheim Cord Blood Bank: Experiences and Perspectives for the Future

SUMMARY: BACKGROUND AND METHODS: As a source of hematopoietic stem cells, cord blood (CB) is an alternative to bone marrow or peripheral blood stem cells (PBSC). The Mannheim Cord Blood Bank has currently stored about 1,750 allogeneic CB units. Here we report our experiences and discuss future perspectives of CB banking. We analyzed CB units for nucleated cell (NC), mononucleated cell (MNC) and CD34+ cell count, volume, colony-forming units (CFU-GM) as well as ethnic background of the donor. Transplanted CB units were analyzed for patient and transplant characteristics and compared to stored CB units. RESULTS: Only 25% of all collected CB units met storage criteria. Main reasons for exclusion were: i) insufficient volume (57.7%), ii) delayed arrival at the processing site (19.2%) and iii) little cell count (7.2%). Up to now 36 CB units have been released for transplantation mainly to children (62%). Transplant indications were hematological diseases, immune deficiencies and metabolic diseases. Transplanted CB units showed significantly higher cell counts compared to stored units (NC: 12.5 vs. 7.2 x 10(8), MNC: 4.7 vs. 2.9 x 10(8), CD34+ cells: 3.3 vs. 1.8 x 10(6), mean; p < 0.001 each) and were found more often in ethnic minority groups (36 vs. 20%; p = 0.04). CONCLUSIONS: Even though cell count and volume are key parameters for the eligibility of CB units, our data indicate that the ethnic background of the donor also plays a major role. Collection and processing of CB should be optimized in order to gain maximum volume and cell counts.

'Not taken in by media hype': how potential donors, recipients and members of the general public perceive stem cell research

BACKGROUND

Views of embryo donors, scientists and members of the general public on embryonic stem cell research (eSCR) have been widely reported. Less is known about views of potential beneficiaries of stem cell therapy and the influence of media 'hype' on perceptions of eSCR among different groups of stakeholders. This study aimed to examine the perceptions of members of the general public as well as two patient groups likely to benefit from eSCR and to explore the role of the media in shaping these views.

METHODS

A qualitative study carried out in Aberdeen, Scotland included 15 people living with Parkinson's disease (PD), 15 people living with diabetes mellitus (DM), 15 couples with infertility and 21 members of the general public who volunteered for the study. Interview transcripts were analysed thematically using grounded theory.

RESULTS

The two patient groups likely to benefit from eSCR in the future differed in their knowledge (mainly gained from the media) and understanding of eSCR. Those living with PD were older, more debilitated and better informed than those with DM who showed limited interest in potential future benefits of eSCR. Infertile couples learnt about eSCR from health professionals who explained the process of embryo donation to them, and had sought no further information. Most of the general public had accessed information on eSCR and believed themselves to be more discerning than others because of their objectivity, intelligence and 'scientific awareness'. Although, the media and internet were primary sources of information for all except couples with infertility, members of all four groups claimed not to be taken in by the media 'hype' surrounding eSCR.

CONCLUSIONS

Those who expected to benefit from eSCR in the future as well as members of the general public differ in their susceptibility to media 'hype', while believing that they are not taken in by exaggerated claims of benefits. As respondents were a selected group who were not drawn from a representative sample, the findings cannot be generalized to a wider population.

A simplified procedure for hematopoietic stem cell amplification using a serum-free, feeder cell-free culture system

Umbilical cord blood (UCB) is increasingly being used as a donor source of hematopoietic stem cells (HSCs) to treat blood malignancies. The main limitation to the widespread use of UCB is the low number of HSCs per unit. To compensate, a strategy of in vitro stem cell amplification has been attempted in different research laboratories. The major hurdle blocking success is the creation of culture conditions that support the growth of hematopoietic stem cells without their differentiation. We have designed a simple culture system for stem and progenitor cell expansion that resulted in an increased number of hematopoietic stem cells that maintain their ability to home to the bone marrow and to permanently engraft.

Umbilical cord blood transplantation after reduced-intensity conditioning for elderly patients with hematologic diseases

Although allogeneic hematopoietic stem cell transplantation is a potentially curative approach for advanced hematologic diseases, its application to elderly people is limited because of their comorbid physical conditions and lower chance of finding suitable related donors. Umbilical cord blood transplantation with reduced-intensity pretransplant conditioning (RI-UCBT) is 1 way to avoid these obstacles. We analyzed elderly patients aged 55 years and older with hematologic diseases who underwent RI-UCBT at our institute to assess feasibility and effectiveness of this treatment approach. Among the 70 patients included, 50 died, 74% of them from nonrelapse causes. Infection was the primary cause of death. Estimated overall survival and progression-free survival at 2 years were both 23%. In multivariate analyses, standard-risk diseases, age younger than 61 years, grade 0-II acute graft-versus-host disease, and the absence of preengraftment immune reaction were significantly associated with better overall survival. RI-UCBT is a potentially curative and applicable approach for elderly patients. Higher mortality, especially from nonrelapse causes, is the biggest problem to be solved to increase the feasibility of this approach.

Human embryonic stem cells: origins, characteristics and potential for regenerative therapy

Stem cells and their use in regenerative therapies are currently hot topics in both biology and medicine. For transfusion scientists the concept of cell therapy is not a new idea but rather a fundamental practice in this field. Bone marrow transplantation was pioneered in the 1960s and relies on the capacity of haemopoietic stem cells in the donated bone marrow to completely reconstitute the blood system of the recipient. Although this capacity of adult (or somatic) stem cells to regenerate the tissue from which they arise is extremely important, the isolation and cultivation of human embryonic stem cells (hESCs) have opened up the possibility to generate any cell or tissue of the body. This characteristic of hESC offers the hope of cell replacement and regenerative therapy for a whole array of diseases, many of which are currently untreatable. However, in order to understand the potential advantages and disadvantages of using stem cells in regenerative medicine, it is necessary to fully understand their origin, characteristics and potential. This review will concentrate particularly on hESCs and their derivation, characterization and capacity to differentiate into clinically useful tissue including haemopoietic lineages.

Expanding the role of umbilical cord blood transplantation

Umbilical cord blood has become a valuable alternative source of haematopoietic stem cells for allogeneic transplantation. However, largely because of the impact of cell dose on engraftment, risk of transplant-related mortality and survival, progress in the field has been largely restricted to children. Nevertheless, substantial clinical experience with umbilical cord blood transplantation clearly establishes its safety and effectiveness in young patients with a variety of malignant and non-malignant diseases. Although less well established in adults, new strategies are now being explored to address the obstacle of cell dose. This article reviews the state of the art and future directions with umbilical cord blood as a source of haematopoietic stem cells for transplantation in both children and adults.

[Donors selection and retrieval of units in an umbilical cord blood bank]

BACKGROUND AND OBJECTIVE

Umbilical cord blood (UCB) contains hematopoietic stem cells that can be used as an alternative to bone marrow transplantation in certain cases. This study was designed to investigate the influence of obstetric, neonatal and collection factors on the hematopoietic content of UCB donations.

MATERIAL AND METHOD

A total of 391 consecutive maternal-neonatal pairs were evaluated during the prepartum period in the maternity ward at La Fe University Hospital. Maternal, neonatal and collection factors influencing cord blood quality measured as volume, total nucleated cells count, CD34+ cells and colony forming units were analyzed in 2,000 UCB collections.

RESULTS

32.5% of UCB potential donors were excluded, mainly due to obstetrical reasons. Among the collected units, 56% were discarded before cryopreservation, mainly due to low cell counts. In the multivariate analysis, placental weight was a predictor variable for total nucleated cells, CD34+ cells and colony forming units, while the mode of collection influenced the total nucleated cells and CD34+ cell counts.

CONCLUSIONS

The collection of UCB units before placental delivery (using the birth weight as an estimation of the placental weight) could be added to standard cord blood donors criteria in order to improve the bank efficiency.

Infectious complications following unrelated cord blood transplantation

INTRODUCTION

Infections following cord blood transplantation are just beginning to be defined in the literature. This review will outline infections at death, the epidemiology of individual infections, and the impact of stem cell source.

METHODS

A review of studies published since 2000.

RESULTS

Based on registry data, most studies demonstrate an approximate rate of infection at death of 30-40% among cord blood recipients. Bacterial infections often occur prior to engraftment and increase among patients with graft failure. In addition, there is delayed recovery of the immune response among patients with graft-versus-host disease that leads to viral infections at later time points. The risk of serious infection among children receiving umbilical cord blood (UCB) grafts is comparable to that of children receiving unmanipulated marrow and is lower than that of recipients of a T-cell-depleted stem cell source. Among adult patients, despite an overall higher incidence of serious infections after UCB transplantation as compared with unrelated donor grafts, non-relapse mortality and overall survival were not significantly different between haematopoietic stem cell sources.

CONCLUSIONS

Further studies are needed to confirm these observations and determine whether the risk of infection for cord blood recipients is comparable to that of recipients of unmanipulated marrow.

[Therapeutic applications and promises of cellular and tissue engineering. What strategic choice for the Etablissement Français du Sang?]

A new medical field, known as regeneration medicine, is developing and attracting more and more researchers and practitioners. Whereas hematopoietic cell-based therapies have already proven their efficacy in numerous--malignant or not--diseases, non-hematopoietic cell-based therapies have not. They can be useful to dozens, if not hundreds, of patients with various disorders, such as cardiopathy, diabetes, some types of cancer, osteoarticular and neurodegenerative disorders. In these fields, numerous clinical applications are possible for mesenchymal stem cells. Cell and tissue (corneas, bone, skin) therapy products require the definition of pharmaceutical standards with new European requirements in terms of quality and safety. The legitimacy of the Etablissement Français du Sang (EFS) in cell and tissue engineering activities is established, it is recognized by most specialists and by regulatory authorities and has been asserted by the orientations of its "contrat d'objectifs et de moyens". An independent committee has been set up by the EFS President to define an EFS-specific strategy. This committee made up of qualified specialists was required to draw up a rational organization plan for these activities, in order for EFS to be in a position to produce cells and tissues according to pharmaceutical standards. The committee proposals are based on economic data and an inventory of existing cell and tissue engineering activities. Public/private partnerships are required and efforts must focus towards the industrial valorization of EFS expertise in R&D activities and staff know-how. Implementing such a new organization requires national management and the cooperation of institutional actors (university hospitals, cancer treatment centers, universities). For the success of this approach, EFS personnel must be convinced of its legitimacy and new skills must be encouraged. With its numerous assets, EFS can be ambitious and assert itself as a major actor in cell and tissue engineering in Europe.

Umbilical cord blood transplantation for myeloid malignancies

PURPOSE OF REVIEW

To review the available data on the outcomes of pediatric and adult patients with acute myeloid leukemia, myelodysplastic syndrome and chronic myelogenous leukemia after umbilical cord blood transplantation.

RECENT FINDINGS

The literature shows that after umbilical cord blood transplantation the relapse rate, disease-free survival and overall survival of patients with myeloid malignancies is similar to other hematopoietic stem cells sources. Disease status at the time of transplantation is found in several studies to be a very important determinant of long-term outcome. Newer strategies such as double umbilical cord blood transplant and utilization of nonmyeloblative conditioning regimens show promising results.

SUMMARY

Umbilical cord blood is a valuable alternative source of hematopoietic stem cells for transplantation of patients with myeloid malignancies who need an allogeneic transplant, but lack a suitable sibling donor.

Umbilical Cord Blood (UCB) Transplantation: An Alternative to the Use of Unrelated Volunteer Donors?

Cryopreserved umbilical cord blood (UCB) from 4-6/6 HLA-A,B antigen and DRB1 allele matched unrelated neonatal donors contains sufficient numbers of hematopoietic stem cells (HSC) to engraft most younger pediatric patients with leukemia. Recent data demonstrate promising results in larger children and adults, as well as in patients with nonmalignant disorders. As a result, the number of UCB transplantations (UCBT) being performed is increasing dramatically. UCB has the clear benefits of rapid availability and a reduced stringency of requirement for HLA match. The latter attribute has the potential to extend the donor pool, which is of great importance for racial and ethnic minorities. Furthermore, new preparative regimens combined with double-unit grafts have been associated with improved engraftment and survival in larger children and adults, making UCBT a viable potential alternative to unrelated volunteer donor transplantation, especially in preference to transplantation using mismatched volunteers. This review summarizes the current status of unrelated donor UCBT and describes both the challenges and current areas of research associated with this HSC source.