Successful cord blood transplantation for sickle cell anemia from a sibling who is human leukocyte antigen-identical: implications for comprehensive care

Choice of Donor Source and Conditioning Regimen for Hematopoietic Stem Cell Transplantation in Sickle Cell Disease

In the United States, one out of every 500 African American children have sickle cell disease (SCD), and SCD affects approximately 100,000 Americans. Significant advances in the treatment of this monogenetic disorder have failed to substantially extend the life expectancy of adults with SCD over the past two decades. Hematopoietic stem cell transplantation (HSCT) remains the only curative option for patients with SCD. While human leukocyte antigen (HLA) matched sibling HSCT has been successful, its availability is extremely limited. This review summarizes various conditioning regimens that are currently available. We explore recent efforts to expand the availability of allogeneic HSCT, including matched unrelated, umbilical cord blood, and haploidentical stem cell sources. We consider the use of nonmyeloablative conditioning and haploidentical donor sources as emerging strategies to expand transplant availability, particularly for SCD patients with complications and comorbidities who can undergo neither matched related transplant nor myeloablative conditioning. Finally, we show that improved conditioning agents have improved success rates not only in the HLA-matched sibling setting but also alternative donor settings.

The case for HLA-identical sibling hematopoietic stem cell transplantation in children with symptomatic sickle cell anemia

This article has a companion Counterpoint by DeBaun and Clayton.

Curative approaches for sickle cell disease: A review of allogeneic and autologous strategies

Despite sickle cell disease (SCD) first being reported >100years ago and molecularly characterized >50years ago, patients continue to experience severe morbidity and early mortality. Although there have been substantial clinical advances with immunizations, penicillin prophylaxis, hydroxyurea treatment, and transfusion therapy, the only cure that can be offered is hematopoietic stem cell transplantation (HSCT). In this work, we summarize the various allogeneic curative approaches reported to date and discuss open and upcoming clinical research protocols. Then we consider gene therapy and gene editing strategies that may enable cure based on autologous HSCs.

Alternative Donor/Unrelated Donor Transplants for the β-Thalassemia and Sickle Cell Disease

Considerable progress with respect to donor source has been achieved in allogeneic stem cell transplant for patients with hemoglobin disorders, with matched sibling donors in the 1980s, matched unrelated donors and cord blood sources in the 1990s, and haploidentical donors in the 2000s. Many studies have solidified hematopoietic progenitors from matched sibling marrow, cord blood, or mobilized peripheral blood as the best source-with the lowest graft rejection and graft versus host disease (GvHD), and highest disease-free survival rates. For patients without HLA-matched sibling donors, but who are otherwise eligible for transplant, fully allelic matched unrelated donor (8/8 HLA-A, B, C, DRB1) appears to be the next best option, though an ongoing study in patients with sickle cell disease will provide data that are currently lacking. There are high GvHD rates and low engraftment rates in some of the unrelated cord transplant studies. Haploidentical donors have emerged in the last decade to have less GvHD; however, improvements are needed to increase the engraftment rate. Thus the decision to use unrelated cord blood units or haploidentical donors may depend on the institutional expertise; there is no clear preferred choice over the other. Active research is ongoing in expanding cord blood progenitor cells to overcome the limitation of cell dose, including the options of small molecule inhibitor compounds added to ex vivo culture or co-culture with supportive cell lines. There are inconsistent data from using 7/8 or lower matched unrelated donors. Before routine use of these less matched donor sources, work is needed to improve patient selection, conditioning regimen, GvHD prophylaxis, and/or other strategies.

Stem Cell and Related Therapies: Nurses and midwives representing all parties

Nurses and midwives are part of health care in all the stages of our lives from preconception to death. Recent scientific advances have introduced new techniques of screening and diagnosis linked to stem cell isolation and therapies. These could affect us at any age and therefore nurses will be involved as carers and patients advocates for these techniques. In this article stem cell techniques and therapies are outlined, as well as some of the ethical challenges faced by various nursing groups, whether in adult, learning difficulties, mental health, paediatric, primary care, public health or health visiting areas. Nurses have to understand the ethical issues and the rights of all parties (donor, recipient and families), which may conflict with each other, to be able to weigh up the benefits and costs to each group involved. Answers have to be found on a case-by-case basis within local moral frameworks and law. Nurses represent all parties in these therapies and act as advocates for every patient group. They need to act in an interprofessional environment to promote the best interests of all their clients, both clinically and ethically.

Hematopoietic stem cell transplantation for patients with sickle cell disease: progress and future directions

Research has solidified matched sibling marrow, cord blood, or mobilized peripheral blood as the best source for allogeneic hematopoietic stem cell transplantation for patients with sickle cell disease, with low graft rejection and graft-versus-host disease (GVHD) and high disease-free survival rates. Fully allelic matched unrelated donor is an option for transplant-eligible patients without HLA-matched sibling donors. Unrelated cord transplant studies reported high GVHD and low engraftment rates. Haploidentical transplants have less GVHD, but improvements are needed to increase the low engraftment rate. The decision to use unrelated cord blood units or haploidentical donors depends on institutional expertise.

Unrelated donor allogeneic hematopoietic stem cell transplantation for patients with hemoglobinopathies using a reduced-intensity conditioning regimen and third-party mesenchymal stromal cells

Allogeneic hematopoietic stem cell transplantation for patients with a hemoglobinopathy can be curative but is limited by donor availability. Although positive results are frequently observed in those with an HLA-matched sibling donor, use of unrelated donors has been complicated by poor engraftment, excessive regimen-related toxicity, and graft-versus-host disease (GVHD). As a potential strategy to address these obstacles, a pilot study was designed that incorporated both a reduced-intensity conditioning and mesenchymal stromal cells (MSCs). Six patients were enrolled, including 4 with high-risk sickle cell disease (SCD) and 2 with transfusion-dependent thalassemia major. Conditioning consisted of fludarabine (150 mg/m(2)), melphalan (140 mg/m(2)), and alemtuzumab (60 mg for patients weighing > 30 kg and .9 mg/kg for patients weighing <30 kg). Two patients received HLA 7/8 allele matched bone marrow and 4 received 4-5/6 HLA matched umbilical cord blood as the source of HSCs. MSCs were of bone marrow origin and derived from a parent in 1 patient and from an unrelated third-party donor in the remaining 5 patients. GVHD prophylaxis consisted of cyclosporine A and mycophenolate mofetil. One patient had neutropenic graft failure, 2 had autologous hematopoietic recovery, and 3 had hematopoietic recovery with complete chimerism. The 2 SCD patients with autologous hematopoietic recovery are alive. The remaining 4 died either from opportunistic infection, GVHD, or intracranial hemorrhage. Although no infusion-related toxicity was seen, the cotransplantation of MSCs was not sufficient for reliable engraftment in patients with advanced hemoglobinopathy. Although poor engraftment has been observed in nearly all such trials to date in this patient population, there was no evidence to suggest that MSCs had any positive impact on engraftment. Because of the lack of improved engraftment and unacceptably high transplant-related mortality, the study was prematurely terminated. Further investigations into understanding the mechanisms of graft resistance and development of strategies to overcome this barrier are needed to move this field forward.

Stem cell transplantation for treatment of sickle cell disease: bone marrow versus cord blood transplants

PURPOSE

The transplantation of stem cells harvested from bone marrow and cord blood for the treatment of sickle cell disease (SCD) is reviewed.

SUMMARY

Current treatment options have lengthened the lifespan of patients with SCD. Hydroxyurea is the standard of care for the management of SCD, but it does not prevent serious complications in all patients. For those patients with severe disease, stem cell transplantation may be an appropriate curative option. However, less than one third of these patients find an appropriate matched related bone marrow donor. Cord blood offers a more readily available source of stem cells for transplantation. Donor morbidity is eliminated, since the cells come from banked cords, and the harvesting process is noninvasive for the donor. Another advantage of cord blood transplantation is the lower occurrence of graft-versus-host disease (GVHD). One disadvantage of transplantation with cord blood includes delayed time to engraftment. Due to the mortality associated with stem cell transplantation, it may be most appropriate to reserve the procedure for patients who have a more severe course of SCD.

CONCLUSION

Although bone marrow, peripheral blood, and cord blood transplantation has been successfully performed in patients with SCD, data remain limited regarding the optimal preparative regimens, the most appropriate stem cell source, and the type of GVHD prophylaxis to be used after transplantation. More data are warranted before this treatment approach can be recommended as a standard of care for SCD.

Allogeneic hematopoietic stem cell transplantation for sickle cell disease: the time is now

Although sickle cell disease (SCD) has a variable clinical course, many patients develop end-organ complications that are associated with significant morbidity and early mortality. Myeloablative allogeneic HSCT (allo-HSCT) is curative but has been historically performed only in children younger than 16 years of age. Modest modifications in the conditioning regimen and supportive care have improved outcome such that the majority of children with a suitable HLA-matched sibling donor can expect a cure from this approach. However, adult patients have been excluded from myeloablative allo-HSCT because of anticipated excess toxicity resulting from accumulated disease burden. Efforts to use nonmyeloablative transplantation strategies in adults logically followed but were initially met with largely disappointing results. Recent results, however, indicate that nonmyeloablative allo-HSCT in adult patients with SCD allows for stable mixed hematopoietic chimerism with associated full-donor erythroid engraftment and normalization of blood counts, and persistence in some without continued immunosuppression suggests immunologic tolerance. The attainment of tolerance should allow extension of these potentially curative approaches to alternative donor sources. Efforts to build on these experiences should increase the use of allo-HSCT in patients with SCD while minimizing morbidity and mortality.

Hematopoietic stem cell transplantation for hemoglobinopathies: current practice and emerging trends

Despite improvements in the management of thalassemia major and sickle cell disease, treatment complications are frequent and life expectancy remains diminished for these patients. Hematopoietic stem cell transplantation (HSCT) is the only curative option currently available. Existing results for HSCT in patients with hemoglobinopathy are excellent and still improving. New conditioning regimens are being used to reduce treatment-related toxicity and new donor pools accessed to increase the number of patients who can undergo HSCT.

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.

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.

Hematopoietic cell transplantation: a curative option for sickle cell disease

Sickle cell disease is associated with considerable morbidity and premature mortality. Hematopoietic cell transplantation offers the possibility of cure and is associated with excellent results in pediatric patients receiving stem cell transplantation from a matched sibling donor. Reduced intensity conditioning regimen have the potential to further reduce regimen related morbidity and mortality. Improved understanding of the natural history of complications such as stroke and pulmonary hypertension, effects of treatments, such as hydroxyurea and blood transfusions, as well as the impact of transplantation on organ damage are likely to influence the timing and indication of transplantation. Improvements in preparative regimen may enable the safe use of alternate source of stem cells such as unrelated matched donors and further improve the applicability and acceptability of this treatment.

Hematopoietic cell transplantation for sickle cell disease: state of the art

Sickle cell disease is associated with considerable morbidity and premature mortality. Hematopoietic cell transplantation offers the possibility of cure and is associated with excellent results in pediatric patients receiving stem cell transplantation from a matched sibling donor. A reduced-intensity conditioning regimen has the potential to further reduce regimen-related morbidity and mortality. Improved understanding of the natural history of complications, such as stroke and pulmonary hypertension, effects of treatments such as hydroxyurea and blood transfusions, as well as the impact of transplantation on organ damage, are likely to influence the timing and indication of transplantation. Improvements in preparative regimens may enable the safe use of an alternative source of stem cells, such as unrelated matched donors, and further improve the applicability and acceptability of this treatment.

Pain Management of Sickle Cell Disease

Management of sickle cell disease continues to be primarily palliative, including supportive, symptomatic, and preventive approaches to therapy. There are three major types of sickle cell pain: acute, chronic, and neuropathic pain. The acute painful episode is the insignia of the disease and the most common cause of hospitalization. Its management entails the use of nonpharmacologic and pharmacologic modalities. Pain management should follow certain principles that include an assessment stage, treatment stage, reassessment stage, and adjustment stage. Chronic sickle cell pain may be due to certain complications of the disease, such as leg ulcers and avascular necrosis; intractable chronic pain may be due to central sensitization. Management of chronic pain should take a multidisciplinary approach.

Milestones in the development of pediatric hematopoietic stem cell transplantation--50 years of progress

In the 1950s, the first infusions of hematopoietic stem cells were given as a form of treatment for childhood leukemia. This heralded the beginning of a field that has expanded to include the treatment of immune deficiencies, a variety of leukemias and solid tumors, and then genetic diseases. A number of milestones are highlighted, particularly in regard to the use of alternative sources of hematopoietic stem cells such as unrelated donors, peripheral blood stem cells and umbilical cord stem cells. In addition, newer techniques of using non-myeloablative preparative regimens helped to reduce the toxicity and long-term consequences of hematopoietic stem cell transplant. Many diseases now benefit from the replacement of the marrow stem cells and the provision of a new immune system and improved immune surveillance.

Sickle cell disease: the neurological complications

The genetic cause of sickle cell disease has been known for decades, yet the reasons for its clinical variability are not fully understood. The neurological complications result from one point mutation that causes vasculopathy of both large and small vessels. Anemia and the resultant cerebral hyperemia produce conditions of hemodynamic insufficiency. Sickled cells adhere to the endothelium, contributing to a cascade of activated inflammatory cells and clotting factors, which result in a nidus for thrombus formation. Because the cerebrovascular reserve becomes exhausted, the capacity for compensatory cerebral mechanisms is severely limited. There is evidence of small-vessel sludging, and a relative deficiency of nitric oxide in these vessels further reduces compensatory vasodilatation. Both clinical strokes and silent infarcts occur, affecting motor and cognitive function. New data suggest that, in addition to sickle cell disease, other factors, both environmental (eg, hypoxia and inflammation) and genetic (eg, mutations resulting in thrombogenesis), may contribute to a patient's stroke risk. The stroke risk is polygenic, and sickle cell disease can be considered a model for all cerebrovascular disease. This complex disease underscores the potential intellectual and practical distance between the determination of molecular genetics and effective clinical application and therapeutics.

Sickle cell anaemia: progress in pathogenesis and treatment

The phenotypic expression of sickle cell anaemia varies greatly among patients and longitudinally in the same patient. It influences all aspects of the life of affected individuals including social interactions, intimate relationships, family relations, peer interactions, education, employment, spirituality and religiosity. The clinical manifestations of sickle cell anaemia are protean and fall into three major categories: anaemia and its sequelae;pain and related issues; andorgan failure including infection. Recent studies on the pathogenesis of sickle cell anaemia have centred on the sequence of events that occur between polymerisation of deoxy haemoglobin (Hb) S and vaso-occlusion. Cellular dehydration, inflammatory response and reperfusion injury seem to be important pathophysiological mechanisms. Management of sickle cell anaemia continues to be primarily palliative in nature, including supportive, symptomatic and preventative approaches to therapy. Empowerment and education are the major aspects of supportive care. Symptomatic management includes pain management, blood transfusion and treatment of organ failure. Pain managment should follow certain priniciples that include assessment, individualisation of therapy and proper utilisation of opioid and nonopioid analgesics in order to acheive adequate pain relief. Blood selected for transfusion should be leuko-reduced and phenotypically matched for the C, E and Kell antigens. Exchange transfusion is indicated in patients who are transfused chronically in order to prevent or delay the onset of iron-overload. Acute chest syndrome is the most common form of organ failure and its management should be agressive, including adequate ventilation, multiple antibacterials and simple or exchange blood transfusion depending on its severity. Preventitive therapy includes prophylactic penicillin in infants and children, blood transfusion (preferably exchange transfusion) in patients with stroke, and hydroxyurea in patients with frequent acute painful episodes. Bone marrow and cord blood transplantation have been successful modalities of curative therapy in selected children with sickle cell anaemia. Newer approaches to preventative therapy include cellular rehydration with agents that inhibit the Gardos channel or the KCl co-transport channel. Curative gene therapy continues to be investigational at the level of the test tube and transgenic mouse models.