Transplantation of unrelated donor umbilical cord blood utilizing double-unit grafts for five teenagers with transfusion-dependent thalassemia

Pretransplant myeloid and immune suppression, reduced toxicity conditioning with posttransplant cyclophosphamide: Initial outcomes of novel approach for matched unrelated donor hematopoietic stem cell transplant for hemoglobinopathies

Hematopoietic stem cell transplant (HSCT) is currently the only curative option for thalassemia major (TM) and sickle cell disease (SCD). We report our experience of using pretransplant immune suppression (PTIS), augmented Johns Hopkins conditioning, and posttransplant cyclophosphamide (PTCy) as graft-versus-host disease (GvHD) prophylaxis for matched unrelated donor (MUD) transplant in TM/SCD. At a median follow-up of 307.5 days (range 251-395), all patients (three TM, one SCD) are alive and disease free. MUD HSCT with PTIS, augmented Johns Hopkins conditioning, and PTCy as GvHD prophylaxis is a promising way of treating patients with hemoglobinopathies with low regimen-related toxicity (RRT), no risk of graft failure (GF) and minimal GvHD rates.

Feasibility of cord blood bank in high altitude Abha: preclinical impacts

We explored the possibility of the cryo-storage of cord blood hematopoietic stem cells (CBHPSC) with respect to the quantity, quality and biologic efficacy of high altitude (HA) region Abha against sea level (SL) region. The results of the post-processed total nucleated cell count was 8.03 ± 0.31 × 10⁷ and 8.44 ± 0.23 × 10⁷ cells in the HA and SL regions respectively. The mean post processing viability of the nucleated cells was about 87.03 ± 1.39 (HA) and 88.33 ± 1.55% (SL) while post thaw cells were 85.61 ± 1.44 (HA) and 86.58 ± 1.61% (SL) after transient cryo-storage. The proliferation of CBHSCs after thawing were comparable between the HA and SL regions. The results of the colony forming unit (CFU) assays of CFU-E, CFU-GEMM, CFU-GM and BFU-E were comparable between HA and SL in both fresh and post thaw, while a declining trend with viability was significant. The differentiation capability of post thaw samples into adipocytes and osteocytes were comparable between HA and SL regions. Overall from the results, it can be evidenced that HA cord blood collection, processing or storage does not hinder the quality or biological efficacy of the CBHPSC.

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.

Indiscernible Benefit of Double-Unit Umbilical Cord Blood Transplantation in Children: A Single-Center Experience from Hong Kong

Double-unit umbilical cord blood (DU-UCB) may extend the use of UCB transplantation and improve clinical outcomes. Data in the literature show that single-unit dominance happened in a vast majority of recipients, and the mechanism is unknown. We examined the clinical relevance and engraftment kinetics of DU-UCB transplant in 65 consecutive children who underwent unrelated single-unit ( n = 25) and double-unit ( n = 40) UCB transplantation for various hematological malignancies ( n = 45) and nonmalignant disorders ( n = 20). Our result showed no discernible benefit to children receiving double-unit transplant over those receiving single-unit transplant when the total nucleated cell (TNC) doses are ≥2.5 × 107/kg, in terms of the hastening of the engraftment of neutrophils and platelets, reduction of nonengraftment, disease recurrence, early mortality, and graft-versus-host disease, despite significantly higher numbers of TNCs in double units. Further analyses demonstrated that the phenomena were not associated with underlying disease, duration of UCB storage, postthaw viability, HLA disparity, ABO incompatibility, gender, or doses of TNCs, CD34+ cells, CD3+ cells, or colony-forming units. Engrafting units in DU-UCB transplants were notably associated with higher CD34+ cell dose. Chimerism studies demonstrated that single-unit dominance started before neutrophil engraftment in DU-UCB transplants. Data from the study suggested no advantage of infusing double-unit UCB, if an adequately dosed single-unit UCB is available. Successful prediction of the dominant graft would optimize algorithms of UCB selection and maximize the long-term engraftment of chosen units.

Unrelated donor hematopoietic stem cell transplantation for the treatment of non-malignant genetic diseases: An alemtuzumab based regimen is associated with cure of clinical disease; earlier clearance of alemtuzumab may be associated with graft rejection

Hematopoietic stem cell transplantation (HSCT) with matched unrelated donors (MUD), offers potentially curative therapy for patients with non-malignant genetic diseases. In this pilot study conducted from 2006 to 2014, we report the outcomes of 15 patients with non-malignant genetic diseases who received a myeloablative regimen with a reduced cyclophosphamide dose, adjunctive serotherapy and MUD HSCT [intravenous alemtuzumab (52 mg/m(2) ), busulfan (16 mg/kg), fludarabine (140mg/m(2) ), and cyclophosphamide (105 mg/kg)]. Graft-versus-host-disease (GVHD) prophylaxis consisted of tacrolimus/cyclosporine and methylprednisolone. Median (range) time to neutrophil engraftment (>500 cells/µL) and platelet engraftment (>20,000/mm(3) ) were 15 (12-28) and 25 (17-30) days, respectively. At a median follow-up of 2 (0.2-5.4) years, the overall survival (OS) was 93.3% (95% CI: 0.61-0.99) and disease-free survival (DFS) was 73.3% (95% CI: 0.44-0.89). Among this small sample, earlier alemtuzumab clearance was significantly associated with graft rejection (P = 0.047), earlier PHA response (P = 0.009) and a trend toward earlier recovery of recent thymic emigrants (RTE) (P = 0.06). This regimen was associated with durable donor engraftment and relatively low rates of regimen related toxicity (RRT); future alemtuzumab pharmacokinetic studies may improve outcomes, by allowing targeted alemtuzumab clearance to reduce graft rejection and promote more rapid immune reconstitution.

Plasma-depleted versus red cell-reduced umbilical cord blood

Umbilical cord blood banks use two methods to store frozen umbilical cord blood (UCB): red cell reduction (RCR) or plasma depletion (PD). The RCR method centrifuges cord blood in hetastarch or albumin to isolate 21 ml of cord blood containing mostly white blood cells, adds 4 ml of 50% dimethyl sulfoxide (DMSO), and then freezes the resulting 25 ml of cell suspension. The PD method removes plasma, saves all the cells, and freezes the cells in 10% DMSO. PD UCB units are cheaper to process but more expensive to store and somewhat more troublesome to thaw. However, when properly thawed and washed, PD UCB units have as many or more total nucleated cells (TNCs), CD34(+) cells, and colony-forming units (CFU) than RCR units. Two studies suggest that PD units have 20-25% more TNCs, MNCs, and CD34(+) cells, as well as two to three times more CFU than RCR units. Higher TNC, CD34(+), and CFU counts predict engraftment rate with faster neutrophil and platelet recovery. PD units have high engraftment rates with low mortality and high disease-free survival, comparable with clinical results of treatments with RCR units. One recent series of studies suggests that PD units are more effective for treating thalassemia with 2-year survival rates of 88%, disease-free survival rates of 74%, and 100% cure rate for children under age 7, compared to only 61% overall survival and 23% disease-free survival rate in thalassemic children treated with RCR units. These findings suggest that PD units not only have more TNCs, CD34(+) cells, and CFU than RCR units but also have high engraftment rates and may be more effective for treating certain conditions such as β-thalassemia.

Unrelated donor cord blood transplantation for non-malignant disorders in children and adolescents

This study analyzes the data reported to the Korean Cord Blood Registry between 1994 and 2008, involving children and adolescents with non-malignant diseases. Sixty-five patients were evaluated in this study: SAA (n = 24), iBMFS, (n = 16), and primary immune deficiency/inherited metabolic disorder (n = 25). The CI of neutrophil recovery was 73.3% on day 42. By day 100, the CI of acute grade II-IV graft-versus-host disease was 32.3%. At a median follow-up of 71 months, five-yr OS was 50.7%. The survival rate (37.5%) and CI of neutrophil engraftment (37.5%) were lowest in patients with iBMFS. Deaths were mainly due to infection, pulmonary complications, and hemorrhage. In a multivariate analysis, the presence of >3.91 × 10(5) /kg of infused CD34 + cells was the only factor consistently identified as significantly associated with neutrophil engraftment (p = 0.04) and OS (p = 0.03). UCBT using optimal cell doses appears to be a feasible therapy for non-malignant diseases in children and adolescents for whom there is no appropriate HLA-matched related donor. Strategies to reduce transplant-related toxicities would improve the outcomes of UCBT in non-malignant diseases.

Hematopoietic stem-cell transplantation for sickle cell disease: current evidence and opinions

With rapidly expanding evidence of benefit reported by several groups, allogeneic hematopoietic stem-cell transplantation has become an acceptable treatment option for sickle cell disease. It is currently the only curative therapy available. Hematopoietic stem-cell transplantation was offered primarily as a therapeutic option for severe sickle cell disease in the context of myeloablative matched sibling donor transplants over the last two decades and helped to establish the benefits of transplantation for this disorder. While this approach provided proof of principle, the disadvantages and limitations of transplantation became evident along the way. It has been recognized that transplantation for sickle cell disease does not need to adhere strictly to the principles of transplantation for malignant disorders, such as achievement of full donor cell chimerism. As reviewed here, in recent years the transplant community has set out to explore ways to make stem-cell transplantation more available to patients with the disease, define indications and better timing, and offset toxicities with novel approaches to conditioning and better supportive care.

Insights and hopes in umbilical cord blood stem cell transplantations

Over 20.000 umblical cord blood transplantations (UCBT) have been carried out around the world. Indeed, UCBT represents an attractive source of donor hematopoietic stem cells (HSCs) and, offer interesting features (e.g., lower graft-versus-host disease) compared to bone marrow transplantation (BMT). Thereby, UCBT often represents the unique curative option against several blood diseases. Recent advances in the field of UCBT, consisted to develop strategies to expand umbilical stem cells and shorter the timing of their engraftment, subsequently enhancing their availability for enhanced efficacy of transplantation into indicated patients with malignant diseases (e.g., leukemia) or non-malignant diseases (e.g., thalassemia major). Several studies showed that the expansion and homing of UCBSCs depends on specific biological factors and cell types (e.g., cytokines, neuropeptides, co-culture with stromal cells). In this review, we extensively present the advantages and disadvantages of current hematopoietic stem cell transplantations (HSCTs), compared to UBCT. We further describe the importance of cord blood content and obstetric factors on cord blood selection, and report the recent approaches that can be undertook to improve cord blood stem cell expansion as well as engraftment. Eventually, we provide two majors examples underlining the importance of UCBT as a potential cure for blood diseases.

Analysis of 120 pediatric patients with nonmalignant disorders transplanted using unrelated plasma-depleted or -reduced cord blood

BACKGROUND

Unrelated cord blood (CB) is an important stem cell source for unrelated hematopoietic cell transplantation (HCT) of patients with nonmalignant disorders. Processing methods to prepare red blood cell-reduced CB units incur significant nucleated cell loss. In contrast, plasma depletion or reduction (PDR) processing of CB units entails the removal of only a portion of the plasma with minimal nucleated cell loss. However, there are relatively limited data regarding outcomes of CB transplants using units processed by PDR.

STUDY DESIGN AND METHODS

A Center for International Blood and Marrow Transplant Research (CIBMTR)-audited analysis was performed on 120 pediatric patients with nonmalignant disorders transplanted between November 2001 and January 2008 at 29 US and 17 international centers using PDR CB units from two CB banks.

RESULTS

Transplant characteristics were as follows: median age, 3.5 years (range, 0.1-14 years); median patient weight, 15 kg (range, 4-61 kg); 58% male; HLA matches (intermediate-resolution HLA-A and HLA-B and high-resolution HLA-DRB1) of the units used in these patients six of six in 26, five of six in 48, four of six in 47, and three of six or two of six in 6; median prefreeze total nucleated cell dose, 10.5×10(7)/kg; median prefreeze CD34+ dose, 3.7×10(5)/kg; and nonmyeloablative regimen in 24%. The median times to myeloid and platelet engraftment were 21 and 49 days, respectively. The cumulative incidence of reported Grade II to IV acute graft-versus-host disease (aGVHD) was 38±5%, and 19±4% had Grade III to IV aGVHD. The Kaplan-Meier estimates of 3-year transplant-related mortality, overall survival, and disease-free survival were 20±4, 79±4, and 70±6%, respectively.

CONCLUSION

These data demonstrate the effectiveness of PDR CB units for HCT.

Cell recovery comparison between plasma depletion/reduction- and red cell reduction-processing of umbilical cord blood

BACKGROUND AIMS

Limited cell dose has hampered the use of cord blood transplantation (CBT) in adults. One method of minimizing nucleated cell loss in cord blood (CB) processing is to deplete or reduce plasma but not red blood cells - plasma depletion/reduction (PDR).

METHODS

The nucleated cell loss of PDR was studied, and determined to be less than 0.1% in the discarded supernatant plasma fraction in validation experiments. After testing and archival sampling, the median nucleated cell recovery for PDR processing was 90%, and median CD34(+) cell recovery 88%. In a CB bank inventory of 12 339 products with both pre- and post-processing total nucleated cells (TNC), PDR processing resulted in median post-processing TNC recoveries of 90.0% after testing and archival samples removal. Using the same 10 CB units divided into two halves, we compared directly the recovery of PDR against hydroxyethyl starch red cell reduction (RCR) for TNC, CD34(+) cells and colony-forming units (CFU-GM, CFU-E, CFU-GEMM and total CFU) after parallel processing. We also compared the loss of very small embryonic-like stem cells (VSEL).

RESULTS

We demonstrated significantly higher recoveries using PDR for TNC (124%), CD34(+) cells (121%), CFU-GM (225%), CFU-GEMM (201%), total CFU (186%) and VSEL (187%). The proportion of high TNC products was compared between 10 912 PDR and 38 819 RCR CB products and found to be 200% higher for products that had TNC ≥150 × 10(7) (P = 0.0001) for the PDR inventory.

CONCLUSIONS

Our data indicate that PDR processing of CB provides a significantly more efficient usage of this valuable and scarce resource.

Umbilical cord blood transplantation for thalassemia major

Hematopoietic cell transplantation is curative therapy for thalassemia major. Although the clinical application of hematopoietic cell transplantation has relied on marrow collected from related and unrelated donors as the primary source of donor hematopoietic cells, umbilical cord blood (UCB) is an alternative source of hematopoietic cells and represents a suitable allogeneic donor pool in the event that a marrow donor is not available. Progress in developing UCB transplantation for thalassemia is reviewed and the most likely areas of future clinical investigation are discussed.

Dynamic adhesion of umbilical cord blood endothelial progenitor cells under laminar shear stress

Late outgrowth endothelial progenitor cells (EPCs) represent a promising cell source for rapid reendothelialization of damaged vasculature after expansion ex vivo and injection into the bloodstream. We characterized the dynamic adhesion of umbilical-cord-blood-derived EPCs (CB-EPCs) to surfaces coated with fibronectin. CB-EPC solution density affected the number of adherent cells and larger cells preferentially adhered at lower cell densities. The number of adherent cells varied with shear stress, with the maximum number of adherent cells and the shear stress at maximum adhesion depending upon fluid viscosity. CB-EPCs underwent limited rolling, transiently tethering for short distances before firm arrest. Immediately before arrest, the instantaneous velocity decreased independent of shear stress. A dimensional analysis indicated that adhesion was a function of the net force on the cells, the ratio of cell diffusion to sliding speed, and molecular diffusivity. Adhesion was not limited by the settling rate and was highly specific to α(5)β(1) integrin. Total internal reflection fluorescence microscopy showed that CB-EPCs produced multiple contacts of α(5)β(1) with the surface and the contact area grew during the first 20 min of attachment. These results demonstrate that CB-EPC adhesion from blood can occur under physiological levels of shear stress.

Hematopoietic stem cell transplantation for sickle cell disease: current practice and emerging trends

Allogeneic HSCT controls sickle cell disease (SCD)-related organ damage and is currently the only curative therapy available. Over the last 2 decades, HSCT has been limited largely to myeloablative matched sibling donor (MSD) procedures that are feasible only in a minority of patients. As the natural history of the disease has evolved, it is clear that subsets of patients with severe disease are at risk for sudden death, devastating CNS and pulmonary complications, and debilitating vasoocclusive crises. For these patients, the benefits of transplantation can outweigh the risks if HSCT can be safely and successfully performed with low early and late toxicities. This review describes advances and ongoing investigation of HSCT for SCD from the perspectives of recipient age and presentation, donor stem cell source, intensity of conditioning, family and medical perspectives, and other variables that influence outcome. Ultimately, HSCT should be viewed as a viable treatment option for SCD on par with other therapies for select patients who can benefit from the procedure.

Overcoming the barriers to umbilical cord blood transplantation

Umbilical cord blood (UCB) transplantation (UCBT) has seen a marked increase in utilization in recent years, especially in the pediatric population; however, graft failure, delayed engraftment and profound delay in immune reconstitution leads to significant morbidity and mortality in adults. The lack of cells available for post-transplant therapies, such as donor lymphocyte infusions, has also been considered a disadvantage. To overcome the cell-dose barrier, the combination of two UCB units is becoming commonplace in adolescent and adult populations, and is currently being studied in pediatrics as well. In some studies, the use of two UCB units appears to have a positive impact on outcomes; however, engraftment is still suboptimal. A possible additional way to improve outcome and extend applicability of UCBT is via ex vivo expansion. Studies to develop optimal expansion conditions are still in the exploratory phase; however, recent studies suggest expanded UCB is safe and can improve outcomes. The ability to transplant across HLA disparities, rapid procurement time and decreased graft-versus-host disease (GvHD) seen with UCBT makes it a promising stem cell source and, while barriers exist, consistent progress is being made to overcome them.

Transplant outcomes in bone marrow failure syndromes and hemoglobinopathies

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only potential cure for most bone marrow (BM) failure syndromes and hemoglobinopathies. Over the past decade, umbilical cord blood (UCB) has been used more frequently as a stem cell source in patients who lack a suitable BM donor. Although graft failure remains a significant problem, UCB transplantation (UCBT) using the optimal conditioning regimen can be a salvage treatment for patients without a suitable BM donor and warrants evaluation in further prospective studies.

Characterization of umbilical cord blood-derived late outgrowth endothelial progenitor cells exposed to laminar shear stress

Endothelial progenitor cells isolated from umbilical cord blood (CB-EPCs) represent a promising source of endothelial cells for synthetic vascular grafts and tissue-engineered blood vessels since they are readily attainable, can be easily isolated, and possess a high proliferation potential. The objective of this study was to compare the functional behavior of late outgrowth CB-EPCs with human aortic endothelial cells (HAECs). CB-EPCs and HAECs were cultured on either smooth muscle cells in a coculture model of a tissue-engineered blood vessels or fibronectin adsorbed to Teflon-AF-coated glass slides. Late outgrowth CB-EPCs expressed endothelial cell-specific markers and were negative for the monocytic marker CD14. CB-EPCs have higher proliferation rates than HAECs, but are slightly smaller in size. CB-EPCs remained adherent under supraphysiological shear stresses, oriented and elongated in the direction of flow, and expressed similar numbers of alpha(5)beta(1) and alpha(v)beta(3) integrins and antithrombotic genes compared to HAECs. There were some differences in mRNA levels of E-selectin and vascular cell adhesion molecule 1 between CB-EPCs and HAECs; however, protein levels were similar on the two cell types, and CB-EPCs did not support adhesion of monocytes in the absence of tumor necrosis factor-alpha stimulation. Although CB-EPCs expressed significantly less endothelial nitric oxide synthase protein after exposure to flow than HAECs, nitric oxide levels induced by flow were not significantly different. These results suggest that late outgrowth CB-EPCs are functionally similar to HAECs under flow conditions and are a promising cell source for cardiovascular therapies.

Umbilical cord blood transplantation for non-malignant diseases

Many factors, including lower risk of GVHD, rapid availability of 4/6-6/6 matched cord blood (CB) units and incremental gains in the outcomes, have led to an increasing use of CB transplantation (CBT) to treat many patients who lack fully matched adult BM donors. A large electronically searchable worldwide inventory of publicly banked CB units allows for quicker donor identification and selection. In this review, we examine the current status and cumulative experience of related and unrelated donor CBT for the treatment of non-malignant diseases, including hemoglobinopathies, BM failure syndromes, primary immunodeficiency diseases (PIDs) and inherited metabolic disorders (IMDs), and conclude that CBT offers a promising and effective therapy for these diseases. Future strategies to facilitate earlier diagnosis and to decrease transplant-related risks should further improve the short- and long-term outcomes. Every effort should be made to perform transplantation early in the course of disease before extensive damage to various tissues and organs ensues.

Transplantation of unrelated donor umbilical cord blood for nonmalignant diseases: a single institution's experience with 45 patients

The potential benefits of unrelated donor bone marrow transplantation are offset by the immunologic complications of graft-versus-host disease (GVHD) and infection. We used cryopreserved umbilical cord blood (UCB) as a strategy to reduce the risks of GVHD and treatment-related mortality (TRM) and improved survival. Data on 45 patients with median age of 4.5 years who received transplants between October 2003 and February 2009 for the treatment of nonmalignant diseases were evaluated. As of May 15, 2009, the median follow-up was 25 months (range: 3-66). The majority (82%) of patients received an HLA-mismatched graft. The median infused total nucleated cell dose was 7.6 x 10(7)/kg and CD34(+) count 4.0 x 10(5)/kg. Primary graft failure was encountered after 4 transplantations (8%). Log-rank tests and Cox regression analyses were used to determine the effects of various demographic, graft-related, and treatment factors on engraftment, GVHD, TRM, graft failure, and survival. Incidences of neutrophil and platelet engraftment were 88% and 82%, respectively. The incidence of severe grade III-IV acute GVHD (aGVHD) was 42%. Five-year overall survival (OS) and disease-free survival (DFS) were 88.1% and 77.1%, respectively. The cumulative incidence of TRM at 2 years was 12.0%. When cell dose and other factors are optimal, unrelated CBT is a promising approach for curative therapy of nonmalignant diseases.

Quantitative monitoring of multi-donor chimerism: a systematic, validated framework for routine analysis

Despite therapeutic advantages, double-donor (DD) HSCTs present technical problems for molecular chimerism (CHM) monitoring. These DD chimeras contain three matched DNAs, so that the genomes of donor(s) and recipient often share the same alleles. In the STR assay, shared recipient/donor alleles are common and have identical physico-chemical properties. As a consequence of the latter, they co-migrate in the same band ('shared peak'), which prevents measuring each allele separately. Without individual allelic measurements, the direct calculation of the chimeric recipient/donor DNA ratio is precluded. This is the first study to document and systematically examine these problems. Its goal was to provide a validated framework for accurate, routine monitoring based on a stepwise analytic paradigm for approximating percent CHM (%CHM) from shared STR-alleles. Analysis of STR-DNA from DD loci showed that at least four of six alleles were typically shared. Despite such extensive allelic sharing, we show how simple arithmetic procedures can be applied for standardized calculation of %CHM based on peak measurements. Criteria for selecting loci suitable for such analysis are provided. Validation of the computational results required analyzing 18 'informative' loci with pre-established reference values for %CHM. In all cases, the results for %CHM, calculated from peak measurements, were +/-5% of the reference value. The conclusions of the study are as follows: (1) Multi-donor chimeras, with shared alleles, can be accurately and simply analyzed within the usual limits of STR measurement error; (2) by examining these various facets of DD CHM analysis, this novel study has provided a basis for standardized, routine quantitative monitoring using the STR/VNTR assay.

Current status of hematopoietic stem cell transplantation in Taiwan

In Taiwan, hematopoietic SCT (HSCT) has been used to treat patients with hematological diseases since 1983. Since then, more than 2200 patients have undergone HSCT in 15 large hospitals. The disease entities included acute leukemia in 37% of cases, non-Hodgkin's lymphoma in 26%, CML in 10%, multiple myeloma in 7% and severe aplastic anemia in 6%. The conditioning regimens used were mainly myeloablative (84% of cases). Non-myeloablative regimens were fludarabine-based. The average age of allogeneic recipients was at least 10 years older than those in the era before their application. The grafts of all patients were derived from peripheral blood in 85% of cases, BM in 13% and cord blood (CB) in 2%. Forty percent of HSCT patients received autologous grafts, whereas more than 25% of allogeneic HSCT patients received grafts from unrelated donors, and overall, there were more than 200 Taiwan HSCT recipients. Currently, CB has been used successfully in pediatric patients with thalassemia major and also in adult patients with hematological malignancy. After transplantation, there was a relatively lower prevalence of acute GVHD. However, a relatively higher proportion of hepatitis B carriers in the recipients had led to a higher incidence of viral reactivation and clinical hepatitis, which was dramatically decreased following lamivudine prophylaxis. In conclusion, HSCT has been successfully adapted to routine clinical care in Taiwan. Several important findings contributing to the progress of HSCT in the past two decades have also been noticed on this island.

Cord blood stem cell transplantation for haemoglobinopathies

Despite improvements in supportive care, patients with beta-thalassaemia major or sickle cell disease (SCD) may benefit from haematopoietic stem cell transplantation at some point during their lives. Human leucocyte antigen (HLA)-matched sibling bone marrow donors are not always available and alternative sources of stem cells have been sought, including related and unrelated donor cord blood transplants (CBT). The outcome of CBT from related donors for the treatment of both thalassaemia major and SCD is now approaching that for bone marrow transplantation, with around 90% of patients surviving disease-free. The main complication is graft rejection, which may be reduced by increasing pretransplant immune suppression. Transplant-related mortality following HLA-identical matched related donor CBT is extremely low but is significant in the small series of unrelated and/or mis-matched donor CBT. The principal limitation to extending the use of CB stem cells for the cure of haemoglobinopathies is the need to better understand the mechanisms of action and optimal conditioning regimens used to secure long-term engraftment while minimizing morbidity and mortality. Further biological studies and clinical trials are needed to address this aim.