Transplantation of highly purified CD34+ progenitor cells from alternative donors in children with refractory severe aplastic anaemia

Collagen biomaterial stimulates the production of extracellular vesicles containing microRNA-21 and enhances the proangiogenic function of CD34+ cells

CD34⁺ cells are promising for revascularization therapy, but their clinical use is limited by low cell counts, poor engraftment, and reduced function after transplantation. In this study, a collagen type I biomaterial was used to expand and enhance the function of human peripheral blood CD34⁺ cells, and potential underlying mechanisms were examined. Compared to the fibronectin control substrate, biomaterial-cultured CD34⁺ cells from healthy donors had enhanced proliferation, migration toward VEGF, angiogenic potential, and increased secretion of CD63⁺CD81⁺ extracellular vesicles (EVs). In the biomaterial-derived EVs, greater levels of the angiogenic microRNAs (miRs), miR-21 and -210, were detected. Notably, biomaterial-cultured CD34⁺ cells had reduced mRNA and protein levels of Sprouty (Spry)1, which is an miR-21 target and negative regulator of endothelial cell proliferation and angiogenesis. Similar to the results of healthy donor cells, biomaterial culture increased miR-21 and -210 expression in CD34⁺ cells from patients who underwent coronary artery bypass surgery, which also exhibited improved VEGF-mediated migration and angiogenic capacity. Therefore, collagen biomaterial culture may be useful for expanding the number and enhancing the function of CD34⁺ cells in patients, possibly mediated through suppression of Spry1 activity by EV-derived miR-21. These results may provide a strategy to enhance the therapeutic potency of CD34⁺ cells for vascular regeneration.-McNeill, B., Ostojic, A., Rayner, K. J., Ruel, M., Suuronen, E. J. Collagen biomaterial stimulates the production of extracellular vesicles containing microRNA-21 and enhances the proangiogenic function of CD34⁺ cells.

Alternative donor HSCT in refractory acquired aplastic anemia - prevention of graft rejection and graft versus host disease by immunoablative conditioning and graft manipulation

Early alternative donor HSCT is a potentially curative therapeutic option for patients with AAA not responding to IST. Seven patients (median age at diagnosis, 11 yr) with refractory AAA without a MSD underwent HSCT from matched unrelated (n = 6) or haploidentical (n = 1) donors. Conditioning regimens included CY (n = 7), muromonab-CD3/ATG (n = 7), TT (n = 6), FLU (n = 5), and TLI (n = 2). Grafts were either CD34 purified and/or CD3/19 depleted and contained a median of 10.17 × 10(6) /kg CD34 and 5.5 × 10(4) /kg CD3 cells. All patients engrafted rapidly. Median time to leukocyte engraftment was 10 days. With a median follow-up of 26 (range, 11-153) months, six patients are alive and well with complete donor hematopoiesis. One heavily pretreated patient developed GVHD grade III and died from progressive renal failure (resulting from microangiopathic hemolytic anemia) and disseminated aspergillosis. Early alternative donor HSCT can help to avoid complications from prolonged IST and presumably improve survival of patients with refractory AAA. Administration of high doses of CD34 purified and/or CD3/19 depleted stem cells following novel immunoablative conditioning may prevent graft rejection and GVHD. However, a long interval from diagnosis to HSCT seems to be associated with poor outcome.

Single-Center Experience: immunosuppressive therapy as frontline treatment for 33 children with acquired severe aplastic anemia

The authors retrospectively analyzed the records of 33 children with acquired severe aplastic anemia (SAA) diagnosed from July 1998 to October 2007 and first treated by immunosuppressive therapy (IST). Serial hematologic parameters, complications, transfusion requirements, and time to response were assessed. Allogeneic hematopoietic stem cell transplantation (HSCT) was attempted in 7 patients after failure of IST (n = 6) or relapse following an initial response to IST (n = 1). One child died of post-transplant lymphoproliferative disorder. Thirty of the 33 patients are alive and well after a median follow-up of 45 months (range, 7-116 months). Overall (transfusion-independent) response to IST was 73% (24/33). The actuarial 5 years survival rate was 89.4%. In this study, all patients with SAA received IST as standard front-line therapy. Approximately three-fourths of patients with SAA have durable recovery and excellent overall survival.

Allogeneic haemopoietic stem cell transplantation in children: what alternative donor should we choose when no matched sibling is available?

Allogeneic haemopoietic stem cell transplantation has provided curative therapy for life-threatening malignant and non-malignant diseases in children for over 40 years. Only 25% of children in whom an allograft is indicated have the ideal option of a human leucocyte antigen-identical sibling donor. Substantial advances in the use of alternative donors (unrelated volunteer donors, haploidentical family donors and unrelated umbilical cord blood donors) now make it possible for almost all children to benefit from this life-saving treatment. Each donor choice is associated with distinct advantages and disadvantages, which have greater or lesser importance in different diseases. We review the current status of alternative donor transplantation for haematological malignancies, primary immunodeficiencies, inherited metabolic disorders and bone marrow failure syndromes and outline the current UK consensus donor selection algorithms for these disease groups.

Acquired aplastic anemia in childhood

In comparison to past decades, children who have acquired aplastic anemia (AA) enjoy excellent overall survival that reflects improvements in supportive care, more accurate exclusion of children who have alternate diagnoses, and advances in transplantation and immunosuppressive therapy (IST). Matched sibling-donor hematopoietic stem cell transplants (HSCT) routinely provide long-term survival in the range of 90%, and 75% of patients respond to IST. In this latter group, the barriers to overall and complication-free survival include recurrence of AA, clonal evolution with transformation to myelodysplasia/acute myelogenous leukemia, and therapy-related toxicities. Improvements in predicting responses to IST, in alternative-donor HSCT, and in rationalizing therapy by understanding the pathophysiology in individual patients are likely to improve short- and long-term outcomes for these children.

Establishing an oral anticoagulant monitoring service in a multiethnic developing country

We describe the establishment of an International Normalized Ratio (INR)-based system for monitoring oral anticoagulant therapy in a multiethnic developing country. There was significant variation in geometric mean normal prothrombin time among ethnic groups: 12.7 s for Indians, 13.4 s for Africans and 13.7 s for subjects of mixed ancestry. About 4129 INR measurements were performed in the first 2 years. The majority (55.2%) of achieved INRs were subtherapeutic. We found 31 (0.8%) instances of severe overanticoagulation (INR > 8.0). There were no bleeding manifestations in 24 (77%) of them. Only two experienced life-threatening haemorrhage. The management of bleeding and excessive anticoagulation was not always in accordance with international recommendations. The high incidence of underanticoagulation in Trinidad and Tobago may be due to genetically determined warfarin resistance or underdosing. Oral anticoagulant monitoring in Trinidad and Tobago could benefit from the centralization of such services to designated clinics with specialized staff and computer-assisted dosing which adopt internationally accepted guidelines for practice.

Recent improvement in outcome of unrelated donor transplantation for aplastic anemia

The aim was to determine whether outcome of unrelated donor transplantation for severe aplastic anemia has improved in recent years and whether this is due to patient selection or better transplant technology. We analyzed 498 patients transplanted during 1990-2005. By running univariate regression models dichotomizing year of transplantation we defined 1998 as the year of the most significant change in survival. Five-year survival increased from 32+/-8% before 1998 to 57+/-8% after 1998 (P<0.0001). When comparing the cohort before (n=149) and after 1998 (n=349), there were no differences except for older age, and more frequent use of PBSCs, after 1998. High-resolution HLA typing data were unavailable. After 1998, there was less graft failure (11 vs 26%, P<0.0001), less acute GvHD (cumulative incidence 28 vs 37%, P=0.02) and less chronic GvHD (22 vs 38%, P=0.004). In multivariate analyses adjusting for differences in age, HLA-mismatch, performance score and time to transplantation, there was no change in the year of transplant effect (relative risk of death in transplants after 1998: 0.44 (95% confidence interval 0.33-0.59)). There is no evidence for patient selection to explain significantly improved survival in patients transplanted after 1998. We speculate that this is due to better donor matching.

An update on the management of severe idiopathic aplastic anaemia in children

The current outlook for a child with severe idiopathic aplastic anaemia (AA) is very much better than in previous decades. In part, this may reflect better differentiation of idiopathic and inherited marrow failure. For children with idiopathic AA and a human leucocyte antigen (HLA)-matched sibling donor (MSD), allogeneic haematopoietic stem-cell transplantation (AHSCT) is the primary therapy of choice, offering long-term disease-free survival of 90%, although graft-versus-host disease remains a cause of long-term morbidity. A greater treatment challenge remains for those children without a MSD. Combination immunosuppressive therapy (IST) is associated with response rates of 70% or more. However, relapse and clonal evolution with transformation to myelodysplasia or acute myeloid leukaemia remain significant problems after IST and long-term event-free survival rates are less impressive. For children who do not have a sustained response to IST, alternate donor AHSCT should be considered. New HLA typing technologies, novel stem cell sources, reduced-intensity conditioning and graft engineering have reduced toxicity and improved the outcome after alternate donor AHSCT. Emerging therapies that capitalise on recent advances in our understanding of the pathophysiology of idiopathic AA and the immunobiology of AHSCT and IST may further improve the long-term outcome of this disease.

Current concepts in the pathophysiology and treatment of aplastic anemia

Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Almost universally fatal just a few decades ago, aplastic anemia can now be cured or ameliorated by stem-cell transplantation or immunosuppressive drug therapy. The pathophysiology is immune mediated in most cases, with activated type 1 cytotoxic T cells implicated. The molecular basis of the aberrant immune response and deficiencies in hematopoietic cells is now being defined genetically; examples are telomere repair gene mutations in the target cells and dysregulated T-cell activation pathways. Immunosuppression with antithymocyte globulins and cyclosporine is effective at restoring blood-cell production in the majority of patients, but relapse and especially evolution of clonal hematologic diseases remain problematic. Allogeneic stem-cell transplant from histocompatible sibling donors is curative in the great majority of young patients with severe aplastic anemia; the major challenges are extending the benefits of transplantation to patients who are older or who lack family donors. Recent results with alternative sources of stem cells and a variety of conditioning regimens to achieve their engraftment have been promising, with survival in small pediatric case series rivaling conventional transplantation results.

Bone marrow transplants from mismatched related and unrelated donors for severe aplastic anemia

For patients with acquired severe aplastic anemia without a matched sibling donor and not responding to immunosuppressive treatment, bone marrow transplantation from a suitable alternative donor is often attempted. We examined risks of graft failure, graft-versus-host disease and overall survival after 318 alternative donor transplants between 1988 and 1998. Sixty-six patients received allografts from 1-antigen and 20 from >1-antigen mismatched related donors; 181 from matched and 51 from mismatched unrelated donors. Most patients were young, had had multiple red blood cell transfusions and poor performance score at transplantation. We did not observe differences in risks of graft failure and overall mortality by donor type. The probabilities of graft failure at 100 days after 1-antigen mismatched related donor, >1-antigen mismatched related donor, matched unrelated donor and mismatched unrelated donor transplants were 21, 25, 15 and 18%, respectively. Corresponding probabilities of overall survival at 5 years were 49, 30, 39 and 36%, respectively. Although alternative donor transplantation results in long-term survival, mortality rates are high. Poor performance score and older age adversely affect outcomes after transplantation. Therefore, early referral for transplantation should be encouraged for patients who fail immunosuppressive therapy and have a suitable alternative donor.

Making therapeutic decisions in adults with aplastic anemia

The management of adults presenting with aplastic anemia (AA) requires careful exclusion of other causes of bone marrow failure. Late-onset inherited forms of AA may present in adulthood with subclinical disease. Recent long-term studies of HLA identical sibling donor BMT show excellent survival for patients under the age of 40 years, but chronic graft-versus-host disease (GVHD) is still a major problem, impacting on quality of life. Recent improvements in outcome after matched unrelated donor BMT may reflect better donor matching and use of reduced intensity conditioning regimens. For patients treated with immunosuppressive therapy (IST), antithymocyte globulin (ATG) and cyclosporin (CSA) remain the standard regimen with excellent overall survival but less impressive failure-free survival due to nonresponse, relapse and later clonal disorders. The benefit of adding granulocyte colony-stimulating factor (G-CSF) to ATG and CSA is unclear and being assessed in a further prospective European study. Patients who are refractory to conventional IST and currently ineligible for BMT represent difficult management problems. For these patients, new approaches to transplantation are being evaluated, such as fludarabine-based conditioning regimens and the potential use of double umbilical cord blood transplants, but there is a need for new immunosuppressive agents. Improved supportive care is likely to be a major factor in improved outcome of all AA patients whether treated with IST or BMT. Robust predictive factors for response to IST are needed to help in decision making at diagnosis and to help justify exploring novel approaches to therapy.

Haematopoietic stem cell transplantation to treat aplastic anaemia

Aplastic anaemia (AA) consists of pancytopenia and empty bone marrow. Its incidence varies worldwide but predominates in developing countries. Diverse aetiologies are involved, with autoimmunity at the centre of the picture. For the 70% of patients with the severe and very severe forms of AA and who lack a human leukocyte antigen (HLA)-matched sibling, immunosuppressive therapy (IST) is key in treating the disease, with a remission rate close to 70%, an 80-90% 5-year survival rate in responding patients and a relapse rate close to 10%. For the 30% with a sibling donor available, haematopoietic stem cell transplant (HSCT) from bone marrow or peripheral blood has up to a 90% chance of cure, with a 5-10% graft rejection/failure rate. Patients who fail IST (25-30%) and lack a sibling donor can benefit from CD34(+)-enriched, partially T cell-depleted unrelated stem cell transplants, with a general survival rate up to 37%, the newest source of stem cells for this modality being cord blood. Non-myeloablative, irradiation-free conditioning regimens offer appreciable benefits, and new immunosuppressive agents, such as fludarabine and alemtuzumab, have been incorporated with promising preliminary results. Graft-versus-host disease, graft failure and infections remain significant challenges in HSCT for which innovative treatment strategies are being developed at present.

Transplantation of CD34+ selected peripheral blood to HLA-identical sibling patients with aplastic anaemia: results from a single institution

We evaluated the use of CD34+ selected allogeneic peripheral blood as a source of hematopoietic progenitors for allogeneic transplantation in 11 patients with aplastic anemia (AA). The median age was 17 years (range, 6--9), and the median time between diagnosis and transplant 1 month (range, 1--4). Conditioning consisted of cyclophosphamide (50 mg/kg per day) on days--7 to--4 and antithymocyte globulin (30 mg/kg per day) on days--4 to--2 in nine patients. Total lymphoid irradiation was added to the preparative regimen for two. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine A and prednisone. Median doses of CD34+ and CD3+ cells infused were 3.91 x 10(6) and 0.3 x 10(6)/kg, respectively. The median time taken to achieve a neutrophil count >0.5 x 10(9)/l was 12 days and to recover a platelet count >20 x 10(9)/l, 13 days. Two patients developed acute GVHD grade I--II and one developed limited chronic GVHD. There were two treatment-related deaths. At a median follow-up of 44 months (range, 4--3), nine patients were alive with sustained and complete engraftment. This is a promising procedure in patients with AA, resulting in a rapid hematopoietic recovery, a low transplant-related mortality, and a low incidence of GVHD.

Non-radiotherapy conditioning with stem cell transplantation from alternative donors in children with refractory severe aplastic anemia

Conditioning including total body/lymphoid irradiation is widely used to prevent graft rejection in patients with refractory severe aplastic anemia (SAA) undergoing hemopoietic cell transplantation (HCT) from alternative donors and or after graft manipulation. To reduce regimen-related toxicity we transplanted three children with refractory SAA after conditioning with radiotherapy-free regimens. Conditioning included fludarabine 175-180 mg/m2 in all patients. In addition, patient 1 (failing two previous grafts) received thiotepa 10 mg/kg and Campath-1H 60 mg/m2; patient 2 cyclophosphamide 120 mg/kg, thiotepa 15 mg/kg and OKT-3 0.1 mg/kg/day for 4 weeks; and patient 3 cyclophosphamide 120 and ATG 90 mg/kg. Stem cell source was unmanipulated marrow from the same unrelated donor as for the two previous transplantations in patient 1 and CD34+-purified peripheral blood stem cells from an HLA-matched unrelated donor and from the haploidentical mother in patients 2 and 3. Only patient 1 received graft-versus-host disease (GVHD) prophylaxis with cyclosporine A and mycophenolate mofetil. Follow-up is now 30, 51, and 15 months. None of the patients developed GVHD. All patients have normal counts with complete donor chimerism. Fludarabine-based conditioning is powerfully immunosuppressive and may be used for children with refractory SAA undergoing HCT from alternative donors even after rejection following previous HCT.

Unrelated donor bone marrow transplantation for children with severe aplastic anemia: minimal GVHD and durable engraftment with partial T cell depletion

Both increased graft rejection and increased graft vs host disease (GVHD) remain obstacles to success for unrelated donor (URD) BMT for patients with SAA. Partial T cell depletion (PTCD) may decrease the risk of severe GVHD, while still maintaining sufficient donor T lymphocytes to ensure engraftment. We report on 12 patients with SAA who underwent PTCD URD BMT. All patients had failed medical therapy or relapsed following initial responses, and were transfusion dependent. The median age was 6 years, and there were five males. Donors were matched for four patients, and mismatched for eight. All patients received total body irradiation with either Ara-C or thiotepa and cyclophosphamide. PTCD was accomplished using monoclonal antibody T10B9 or OKT3 and complement. All patients engrafted, with a median time of 18 days to ANC >500. Only one patient had greater than grade II acute GVHD; two patients had limited and one patient extensive chronic GVHD. Nine patients are alive and transfusion independent at a median months post BMT. Three patients died from infection or renal failure. This series suggests that an aggressive immunosuppressive conditioning regimen with PTCD results in successful engraftment and minimal GVHD in pediatric patients with SAA, even with HLA mismatched donors.