Aims of conditioning

Physical performance before and after hematopoietic stem cell transplantation in pediatric patients: a potential role for prehabilitation

The trajectory of hematopoietic stem cell transplantation (HSCT) is often accompanied by physically disabling complications that impair physical performance of pediatric patients. However, knowledge about when impairments in physical performance arise and the factors contributing to these impairments is limited. Therefore, we conducted a retrospective analysis of physical performance 100 days post-HSCT in patients aged 3-18 years. Additionally, we aim to elucidate the relationship between pre- and post-HSCT physical performance and to unravel the impact of intensive HSCT procedures on post-HSCT physical performance. To explore associations between physical performance outcomes post-HSCT and covariates, linear regression models were estimated. Seventy-seven patients were included with a median age of 11.8 years (interquartile range: 5.9, 14.8). Patients had lower hip flexion muscle strength and appendicular skeletal muscle mass and a slower rising from the floor time 100 days post-HSCT compared to average values of the normal population. Pre-HSCT physical performance was positively associated with physical performance post-HSCT, independent of age, the cumulative glucocorticoids dosage administered and the total duration of hospitalization during the HSCT trajectory. This explorative study highlights the potential role of prehabilitation in enhancing physical performance of pediatric HSCT patients.

Fludarabine, busulfan, and melphalan conditioning regimen in allogeneic hematopoietic stem cell transplantation for adult patients with myeloid malignancies: A multicenter retrospective study

Relapse remains the main cause of treatment failure in patients with myeloid malignancies even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We observed a particularly low incidence of relapse in patients prepared with fludarabine, busulfan and melphalan in our previous study and this multicenter retrospective analysis aimed to confirm the feasibility of the regimen and to identify the potential prognostic factors. This study was performed using registry data from adults patients with myeloid malignancies who underwent their first allo-HSCT following fludarabine(≥100 mg/m2), busulfan (≥3.2 mg/kg) and melphalan (≥100 mg/m2) based conditioning at nine transplantation centers in China between Jan. 2020 and Mar. 2022. A total of 221 consecutive patients (AML n = 171, MDS-IB-1 or 2 n = 44, CMML n = 6) with median age of 46 were enrolled in this study. The median follow-up was 507 days for survivors. The 2-year NRM, CIR, OS and DFS were 10.6% ± 2.2%, 14.8% ± 3.3%, 79.4% ± 3.7% and 74.6% ± 3.7%, respectively. In multivariate analyses, high HCT-CI (≥3) was the only independent factor for higher NRM [hazard ratio (HR), 2.96; 95% confidence interval (CI), 1.11 to 7.90; p = 0.030] and ECOG score ≥2 was the only independent factor for inferior OS (HR, 2.43; 95%CI, 1.15 to 5.16; p = 0.020) and DFS (HR, 2.12; 95%CI, 1.13 to 4.02; p = 0.020). AML diagnosis and positive measurable residual disease (MRD) at transplantation were predictors for higher CIR (HR = 7.92, 95%CI 1.05-60.03, p = 0.045; HR = 3.64, 95%CI 1.40-9.44, p = 0.008; respectively), while post-transplantation cyclophosphamide based graft-versus-host disease prophylaxis was associated with lower CIR (HR = 0.24 95%CI 0.11-0.54, p = 0.001). The intensity of conditioning regimen did not impact CIR, NRM, DFS and OS. These results supported that double alkylating agents of busulfan and melphalan based conditioning regimens were associated with low relapse rate and acceptable NRM in adult patients with myeloid malignancies. The optimal dose remained to be confirmed by further prospective studies.

Fludarabine melphalan versus fludarabine treosulfan for reduced intensity conditioning regimen in allogeneic hematopoietic stem cell transplantation: a retrospective analysis

Various reduced-intensity conditioning (RIC) regimens are used to decrease toxicity while providing comparable outcomes to myeloablative regimens. We compared toxicity and outcomes between two RIC regimens, fludarabine with melphalan (Flu-Mel) and fludarabine with treosulfan (Flu-Treo), retrospectively over a 10-year period in two donor groups, matched related donor (MRD)/matched unrelated donor (MUD) and haploidentical (Haplo) transplants. The study included 138 patients, of which 105 received MRD/MUD (Flu-Mel: 94, Flu-Treo: 11) and 33 Haplo (Flu-Mel: 17, Flu-Treo: 16) transplants. In the MRD/MUD group, 44 (47%) of patients who received Flu-Mel had grade 3/4 oral mucositis compared to 1 (9%) who received Flu-Treo (P = 0.02). Corresponding numbers in the Haplo group were 7 (41%) and 1 (6%). Grade 3/4 diarrhoea was more frequent with Flu-Mel than Flu-Treo in the Haplo group (41% vs 6%; P = 0.039), but not the MRD/MUD group. Median follow-up time for all patients was 4.8 years. Five-year OS in the MRD/MUD group was 62% with Flu-Mel versus 53% with Flu-Treo (P = 0.0694). Similarly, 5-year OS was 41% with Flu-Mel and 28% with Flu-Treo (P = 0.770) in the Haplo group. Severe mucositis and diarrhoea were significantly less frequent with Flu-Treo than Flu-Mel. Flu-Treo provided comparable outcomes to Flu-Mel in all donor transplants.

Total marrow irradiation versus total body irradiation using intensity-modulated helical tomotherapy

BACKGROUND

Total body irradiation (TBI) is often a component of the conditioning regimen prior to hematopoietic stem cell transplantation in patients with hematological malignancies. However, total marrow irradiation (TMI) could be an alternative method for reducing radiation therapy-associated toxicity, as it specifically targets the skeleton and thus could better protect organs at risk. Here, we compared dosimetric changes in irradiation received by the target volume and organs at risk between TBI and TMI plans.

MATERIALS AND METHODS

Theoretical TMI plans were calculated for 35 patients with various hematological malignancies who had already received TBI in our clinic. We then statistically compared irradiation doses between the new TMI plans and existing TBI plans. We examined whether TMI provides greater protection of organs at risk while maintaining the prescribed dose in the targeted skeletal area. We also compared beam-on times between TBI and TMI.

RESULTS

TMI planning achieved significant reductions in the mean, minimum, and maximum irradiation doses in the lungs, kidneys, liver, spleen, and body (i.e., remaining tissue except organs and skeleton). In particular, the mean dose was reduced by 49% in the liver and spleen and by 55-59% in the kidneys. Moreover, TMI planning reduced the corpus beam-on time by an average of 217 s.

CONCLUSION

TMI planning achieved significant dose reduction in organs at risk while still achieving the prescribed dose in the target volume. Additionally, TMI planning reduced the beam-on time for corpus plans despite a high modulation factor.

Gonadal-sparing total body irradiation with the use of helical tomotherapy for nonmalignant indications

Background

The aim was to demonstrate the feasibility and technique of gonadal sparing total body irradiation (TBI) with helical tomotherapy. Total body irradiation is a common part of the conditioning regimen prior to allogeneic stem cell transplantation. Shielding or dose-reduction to the gonads is often desired to preserve fertility, particularly in young patients undergoing transplant for non-malignant indications. Helical tomotherapy (HT) has been shown to be superior to traditional TBI delivery for organ at risk (OA R) doses and dose homogeneity.

Materials and methods

We present two representative cases (one male and one female) to illustrate the feasibility of this technique, each of whom received 3Gy in a single fraction prior to allogeneic stem cell transplant for benign indications. The planning target volume (PTV) included the whole body with a subtraction of OA Rs including the lungs, heart, and brain (each contracted by 1cm) as well as the gonads (testicles expanded by 5 cm and ovaries expanded by 0.5 cm).

Results

For the male patient we achieved a homogeneity index of 1.35 with a maximum and median planned dose to the testes of 0.53 Gy and 0.35 Gy, respectively. In-vivo dosimetry demonstrated an actual received dose of 0.48 Gy. For the female patient we achieved a homogeneity index of 1.13 with a maximum and median planned dose to the ovaries of 1.66 Gy and 0.86 Gy, respectively.

Conclusion

Gonadal sparing TBI is feasible and deliverable using HT in patients with non-malignant diseases requiring TBI as part of a pre-stem cell transplant conditioning regimen.

Emerging strategies for enhancing the homing of hematopoietic stem cells to the bone marrow after transplantation

Bone marrow failure is the primary cause of death after nuclear accidents or intentional exposure to high or low doses of ionizing radiation. Hematopoietic stem cell transplantation is the most potent treatment procedure for patients suffering from several hematopoietic malignancies arising after radiation injuries. Successful hematopoietic recovery after transplantation depends on efficient homing and subsequent engraftment of hematopoietic stem cells in specific niches within the bone marrow. It is a rapid and coordinated process in which circulating cells actively enter the bone marrow through the process known as transvascular migration, which involves the tightly regulated relay of events that finally leads to homing of cells in the bone marrow. Various adhesion molecules, chemokines, glycoproteins, integrins, present both on the surface of stem cells and sinusoidal endothelium plays a critical role in transvascular migration. But despite having an in-depth knowledge of homing and engraftment and the key events that regulate it, we are still not completely able to avoid graft failures and post-transplant mortalities. This deems it necessary to design a flawless plan for successful transplantation. Here, in this review, we will discuss the current clinical methods used to overcome graft failures and their flaws. We will also discuss, what are the new approaches developed in the past 10-12 years to selectively deliver the hematopoietic stem cells in the bone marrow by adopting proper targeting strategies that can help revolutionize the field of regenerative and translational medicine.

Bronchiolitis obliterans after allogeneic hematopoietic stem cell transplantation: The effect of NOD2/CARD15 mutations in a Tunisian population

Bronchiolitis obliterans (BO) is a serious lung complication that can develop after allogenic stem cell transplantation. It has been suggested that single nucleotide polymorphisms (SNPs) that affect the NOD2/CARD15 gene impair its function and result in an uncontrolled innate immune response in the recipient, thereby leading to BO. One hundred eighty-one donor-recipient pairs were analyzed for the association between NOD2 gene variants (SNP8 [Arg702Trp], SNP12 [Gly908Arg], and SNP13 [Leu1007fsinsC]) and the occurrence of BO. Ten patients (2.8%) developed this complication. The incidence of BO increases in recipient variant patient group from 4.7% to 23% in donor Wild-type group in SNP8 (p < 0.001). The incidence rose to 19% when the recipient carried the SNP12 variant (p < 0.001) in the Tunisian population. Analyses demonstrated that recipient NOD2CARD15 variants (SNP8 and SNP12) present a greater risk in developing BO than recipients without mutation. Our study demonstrated that NOD2/CARD15 typing may be useful in identifying patients at high risk for BO.

Alloreactive Regulatory T Cells Allow the Generation of Mixed Chimerism and Transplant Tolerance

The induction of donor-specific transplant tolerance is one of the main goals of modern immunology. Establishment of a mixed chimerism state in the transplant recipient has proven to be a suitable strategy for the induction of long-term allograft tolerance; however, current experimental recipient preconditioning protocols have many side effects, and are not feasible for use in future therapies. In order to improve the current mixed chimerism induction protocols, we developed a non-myeloablative bone-marrow transplant (NM-BMT) protocol using retinoic acid (RA)-induced alloantigen-specific Tregs, clinically available immunosuppressive drugs, and lower doses of irradiation. We demonstrate that RA-induced alloantigen-specific Tregs in addition to a NM-BMT protocol generates stable mixed chimerism and induces tolerance to allogeneic secondary skin allografts in mice. Therefore, the establishment of mixed chimerism through the use of donor-specific Tregs rather than non-specific immunosuppression could have a potential use in organ transplantation.

Pushing the envelope-nonmyeloablative and reduced intensity preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic cell transplantation (HCT) was originally developed to allow delivery of myeloablative doses of chemotherapy and radiotherapy. With better understanding of disease pathophysiology, the graft vs malignancy (GVM) effect of allogeneic hematopoietic transplantation and toxicities associated with myeloablative conditioning (MAC) regimens, the focus shifted to developing less toxic conditioning regimens to reduce treatment-related morbidity without compromising survival. Although HCT with MAC is preferred to reduced intensity conditioning (RIC) for most patients ⩽60 years with AML/myelodysplastic syndrome and ALL, RIC and nonmyeloablative (NMA) regimens allow HCT for many otherwise ineligible patients. Reduced intensity preparative regimens have produced high rates of PFS for diagnoses, which are highly sensitive to GVM. Relapse of the malignancy is the major cause of treatment failure with RIC/NMA HCT. Incorporation of novel agents like bortezomib or lenalidomide, addition of cellular immunotherapy and use of targeted radiation therapies could further improve outcome. In this review, we discuss commonly used RIC/NMA regimens and promising novel regimens.

A well-tolerated regimen of 800 cGy TBI-fludarabine-busulfan-ATG for reliable engraftment after unmanipulated haploidentical peripheral blood stem cell transplantation in adult patients with acute myeloid leukemia

Eighty adult patients with acute myeloid leukemia (AML) received peripheral blood T cell-replete HLA haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Disease status at transplantation was either first or second complete remission (CR, n = 69) or relapse/refractory (n = 11). Identical transplant-related procedures with conditioning regimen consisting of fractionated 800 cGy total body irradiation (TBI), fludarabine (30 mg/m(2)/day for 5 days), busulfan (3.2 mg/kg/day for 2 days), and antithymocyte globulin (1.25 mg/kg/day on days -4 to -1) and graft-versus-host disease (GVHD) prophylaxis with tacrolimus and methotrexate were used in all patients. Recovery of neutrophil (median, 11 days) and platelet (median, 10 days) counts was achieved in all patients with full donor chimerism (≥ 99%), and no delayed engraftment failure was observed. The cumulative incidence of grades III to IV acute GVHD and moderate to severe chronic GVHD was 11.2% and 26.3%, respectively. A donor CD8(+) and CD4(+) T cell dose above the median value was significantly associated with the incidences of grades II to IV acute GHVD and moderate to severe chronic GVHD, respectively. After a median follow-up of 28 months for survivors, the 2-year cumulative incidences of relapse (n = 20) and nonrelapse mortality (n = 10) were 26.6% and 12.2%, respectively. Although all but 1 patient in relapse/refractory status died, the 2-year overall and progression-free survival of patients in first CR was 82.5% and 75.1%, respectively. We suggest the strategy of fractionated 800 cGy TBI-based conditioning with unmanipulated peripheral blood stem cell grafts seems feasible with favorable outcomes for adult patients with AML undergoing haplo-HSCT in CR.

Neurologic complications of bone marrow transplantation

Although bone marrow transplantation has been recognized as an effective therapy for malignant and nonmalignant blood disorders, the modality has also been associated with side-effects and complications. Among these adverse events, neurologic complications emerged as an important and frequent source of treatment-related morbidity and mortality. The survival of patients who died from complications related to central nervous system abnormalities appears to be shorter compared to those who died from non-neurological complications. The incidence of neurologic complications appears to correlate with the degree of human leukocyte antigen (HLA) disparity and the risk status of the underlying disease. Nonrelapse mortality associated with reduced intensity regimens is lower compared to myeloablative conditioning regimens. However, reduced intensity regimens are still associated with significant incidence of complications, including graft-versus-host disease, opportunistic infections, organ toxicity, and neurologic complications. Complications of sepsis-related encephalopathy in mechanically ventilated patients are frequently either overlooked or misdiagnosed. Obtaining a microbiological diagnosis through body fluid cultures or tissue identification is important in order to identify the source of infection and guide an effective antimicrobial therapy. However, pursuing a microbiological diagnosis must not delay the administration of antibiotics and resuscitation of a patient with septic shock.

Hematopoietic stem cell transplantation for systemic lupus erythematosus

Two streams of research are at the origin of the utilization of hematopoietic stem cell transplantation (HSCT) for severe autoimmune diseases (SADs). The allogeneic approach came from experimental studies on lupus mice, besides clinical results in coincidental diseases. The autologous procedure was encouraged by researches on experimental neurological and rheumatic disorders. At present the number of allogeneic HSCT performed for human SADs can be estimated to not over 100 patients, and the results are not greatly encouraging, considering the significant transplant-related mortality (TRM) and the occasional development of a new autoimmune disorder and/or relapses notwithstanding full donor chimerism. Autologous HSCT for refractory SLE has become a major target. Severe cases have been salvaged, TRM is low and diminishing, and prolonged clinical remissions are obtainable. Two types of immune resetting have been established, "re-education" and regulatory T cell (Tregs) normalization. Allogeneic HSCT for SLE seems best indicated for patients with disease complicated by an oncohematologic malignancy. Autologous HSCT is a powerful salvage therapy for otherwise intractable SLE. The duration of remission in uncertain, but a favorable response to previously inactive treatments is a generally constant feature. The comparison with new biological agents, or the combination of both, are to be ascertained.

Effects of Pre-conditioning Dose on the Immune Kinetics and Cytokine Production in the Leukocytes Infiltrating GVHD Tissues after MHC-matched Transplantation

Background

Graft-versus-host disease (GVHD) is a huddle for success of hematopoietic stem cell transplantation. In this study, effects of irradiation dose on immune kinetics of GVHD were investigated using B6 → BALB.B system, a mouse model for GVHD after MHC-matched allogeneic transplantation.

Methods

BALB.B mice were transplanted with bone marrow and spleen cells from C57BL/6 mice after irradiation with different doses. Leukocytes residing in the peripheral blood and target organs were collected periodically from the GVHD hosts for analysis of chimerism formation and immune kinetics along the GVHD development via flow cytometry. Myeloid cells were tested for production of IL-17 via flow cytometry.

Results

Pre-conditioning of BALB.B hosts with 900 cGy and 400 cGy resulted in different chimerism of leukocytes from the blood and affected survival of GVHD hosts. Profiles of leukocytes infiltrating GVHD target organs, rather than profiles of peripheral blood leukocytes (PBLs), were significantly influenced by irradiation dose. Proportions of IL-17 producing cells in the infiltrating Gr-1⁺ or Mac-1⁺ cells were higher in the GVHD hosts with high does irradiation than those with low dose irradiation.

Conclusion

Pre-conditioning dose affected tissue infiltration of leukocytes and cytokine production by myeloid cells in the target organs.

Expansion and activation kinetics of immune cells during early phase of GVHD in mouse model based on chemotherapy conditioning

In the present paper, we have investigated early pathophysiological events in graft-versus-host disease (GVHD), a major complication to hematopoietic stem cell transplantation (HSCT). BLLB/c female mice conditioned with busulfan/cyclophosphamide (Bu-Cy) were transplanted with allogeneic male C57BL/6. Control group consisted of syngeneic transplanted Balb/c mice. In allogeneic settings, significant expansion and maturation of donor dendritic cells (DCs) were observed at day +3, while donor T-cells CD8+ were increased at day +5 (230%) compared to syngeneic HSCT. Highest levels of inflammatory cytokines IL-2, IFN-gamma, and TNF-alfa at day +5 matched T-cell activation. Concomitantly naïve T-cells gain effecr-memory phenotype and migrated from spleen to peripheral lymphoid organs. Thus, in the very early phase of GHVD following Bu-Cy conditioning donor, DCs play an important role in the activation of donor T cells. Subsequently, donor naïve T-cells gain effector-memory phenotype and initiate GVHD.

Pediatric immunohematopoietic stem cell transplantation at a tertiary care center in Cape Town

INTRODUCTION AND STUDY DESIGN: We conducted a retrospective analysis of consecutive referrals of patients under 18 years of age undergoing immunohematopoietic stem cell transplantation to assess the influence of age, diagnosis, graft type and gender on survival. We also contrasted program activity and outcome to that reported from a state hospital in the same geographical area over a comparable period.

METHODS

Conditioning employed either a sequential combination of fractionated 12Gy whole body and 6Gy total nodal irradiation separated by 120mg/kg of cyclophosphamide in patients over 15 years of age. Alternatively, the latter agent was combined initially with oral busulphan and later the intravenous equivalent. Neuroblastoma cases were prepared using a different regimen. In allografts the harvested product underwent ex vivo T-cell depletion with the humanized version of anti-CD 52 monoclonal antibody designated Campath 1H. No additional immunosuppression was given except where matched unrelated volunteer donors were employed.

RESULTS

Sixty-eight procedures were carried out in 61 patients over a 6-year period. Of 11 with acute myeloid leukemia, 8 are alive and well whereas 8 of the 14 with the lymphoblastic variant have died. Of the remaining 12 with hematologic malignancy, all but 2 are alive. Ten of the 17 with aplasia are alive as are all with thalassemia or sickle cell disease. None of the four variables tested affected survival.

CONCLUSION

Our analysis indicates that the standardized preparative regimen, coupled with a now well-established immunosuppressive regimen, is as effective in patients under 18 years of age as in adults. Our analysis also indicates that in a resource-scarce or developing country, it is mandatory to limit high-risk and relatively expensive procedures to active teams that enjoy international accreditation, whether these be in the state or private sector.

Defining the intensity of conditioning regimens: working definitions

Defining conditioning regimen intensity has become a critical issue for the hemopoietic stem cell transplant (HSCT) community. In the present report we propose to define conditioning regimens in 3 categories: (1) myeloablative (MA) conditioning, (2) reduced-intensity conditioning (RIC), and (3) nonmyeloablative (NMA) conditioning. Assignment to these categories is based on the duration of cytopenia and on the requirement for stem cell (SC) support: MA regimens cause irreversible cytopenia and SC support is mandatory. NMA regimens cause minimal cytopenia, and can be given also without SC support. RIC regimens do not fit criteria for MA or NMA regimens: they cause cytopenia of variable duration, and should be given with stem cell support, although cytopenia may not be irreversible. This report also assigns commonly used regimens to one of these categories, based upon the agents, dose, or combinations. Standardized classification of conditioning regimen intensities will allow comparison across studies and interpretation of study results.

Reduced-intensity conditioning regimen workshop: defining the dose spectrum. Report of a workshop convened by the center for international blood and marrow transplant research

During the 2006 BMT Tandem Meetings, a workshop was convened by the Center for International Blood and Marrow Transplant Research (CIBMTR) to discuss conditioning regimen intensity and define boundaries of reduced-intensity conditioning (RIC) before hematopoietic cell transplantation (HCT). The goal of the workshop was to determine the acceptance of available RIC definitions in the transplant community. Participants were surveyed regarding their opinions on specific statements on conditioning regimen intensity. Questions covered the "Champlin criteria," as well as operational definitions used in registry studies, exemplified in clinical vignettes. A total of 56 participants, including transplantation physicians, transplant center directors, and transplantation nurses, with a median of 12 years of experience in HCT, answered the survey. Of these, 67% agreed that a RIC regimen should cause reversible myelosuppression when administered without stem cell support, result in low nonhematologic toxicity, and, after transplantation, result in mixed donor-recipient chimerism at the time of first assessment in most patients. Likewise, the majority (71%) agreed or strongly agreed that regimens including < 500 cGy of total body irradiation as a single fraction or 800 cGy in fractionated doses, busulfan dose < 9 mg/kg, melphalan dose <140 mg/m(2), or thiotepa dose < 10 mg/kg should be considered RIC regimens. However, only 32% agreed or strongly agreed that the combination of carmustine, etoposide, cytarabine, and melphalan (BEAM) should be considered a RIC regimen. These results demonstrate that although HCT professionals have not reached a consensus on what constitutes a RIC regimen, most accept currently used criteria and operational definitions. These results support the continued use of current criteria for RIC regimens until a consensus statement can be developed.

Bone mass and microarchitecture of irradiated and bone marrow-transplanted mice: influences of the donor strain

Total body irradiation and bone marrow transplantation induced dramatic trabecular bone loss and cortical thickening in mice. Transplanted cells were engrafted in bone marrow, along trabeculae, and in periosteal and endosteal envelopes. None of the osteocytes were of donor origin. Bone microarchitecture of transplanted mice changed to tend toward the donor phenotype.

INTRODUCTION

Osteopenia and osteoporosis are complications of bone marrow transplants (BMT) attributed to related chemotherapy. However, the specific influence of total body irradiation (TBI) is unknown.

METHODS

We investigated the effects of TBI and BMT on bone mass and microarchitecture by micro-CT. Eighteen C57Bl/6 (B6) mice receiving lethal TBI had a BMT with marrow cells from green fluorescent protein--transgenic-C57Bl/6 (GFP) mice. Transplanted (T(GFP)B6), B6, and GFP mice were euthanized 1, 3, and 6 months after BMT or at a related age.

RESULTS

T(GFP)B6 presented a dramatic bone loss compared with B6 and did not restore their trabecular bone mass over time, despite a cortical thickening 6 months after BMT. Serum testosterone levels were not significantly reduced after BMT. During aging, GFP mice have less trabeculae, thicker cortices, but a narrower femoral shaft than B6 mice. From 3 months after BMT, cortical characteristics of T(GFP)B6 mice differed statistically from B6 mice and were identical to those of GFP mice. GFP(+) cells were located along trabecular surfaces and in periosteal and endosteal envelopes, but none of the osteocytes expressed GFP.

CONCLUSION

Our findings suggest that engrafted cells did not restore the irradiation-induced trabecular bone loss, but reconstituted a marrow microenvironment and bone remodeling similar to those of the donor. The effects of irradiation and graft on bone remodeling differed between cortical and trabecular bone.

The effect of administration order of BU and CY on engraftment and toxicity in HSCT mouse model

Conditioning regimens are an important issue determining the outcome of hematopoietic stem cell transplantation (HSCT). Less toxicity, early engraftment and no relapse are the aims of efficient conditioning. Our objective was to investigate the long-term effects of BU-CY and their administration order on the toxicity and chimerism in a mouse model of HSCT. Female BALB/c mice were treated with either BU (15 mg/kg/day x 4)-CY (100 mg/kg/day x 2) or CY-BU. Treated mice were transplanted with Sca-1+ cells from male BALB/c mice. Until 90 days after HSCT, the animals were monitored for body weight and analyzed for cellular phenotype of the thymus, spleen and BM, total chimerism, the spleen chimerism of DCs and T regulatory (Treg) cells, and hepatotoxicity. BU-CY and CY-BU treatments exerted comparable myeloablative and immunosuppressive effects. The long-term engraftment of donor cells in the BM and thymus regeneration showed the same features in both groups. However, the two regimens differed; in general, hepatotoxicity and chimerism of DC and Treg cells. In the long term, BU-CY, but not CY-BU caused a marked decrease in body weight and a significant increase in the activities of the liver enzymes, particularly aspartate amino transferase (AST). We conclude that the alteration of the administration order of BU-CY to CY-BU not only gives the same level of engraftment but also reduces the toxicity of the conditioning regimen that might be valuable specially in young patients who are undergoing HSCT.

Prevention of acute and chronic allograft rejection with CD4+CD25+Foxp3+ regulatory T lymphocytes

A major challenge in transplantation medicine is controlling the very strong immune responses to foreign antigens that are responsible for graft rejection. Although immunosuppressive drugs efficiently inhibit acute graft rejection, a substantial proportion of patients suffer chronic rejection that ultimately leads to functional loss of the graft. Induction of immunological tolerance to transplants would avoid rejection and the need for lifelong treatment with immunosuppressive drugs. Tolerance to self-antigens is ensured naturally by several mechanisms; one major mechanism depends on the activity of regulatory T lymphocytes. Here we show that in mice treated with clinically acceptable levels of irradiation, regulatory CD4+CD25+Foxp3+ T cells stimulated in vitro with alloantigens induced long-term tolerance to bone marrow and subsequent skin and cardiac allografts. Regulatory T cells specific for directly presented donor antigens prevented only acute rejection, despite hematopoietic chimerism. By contrast, regulatory T cells specific for both directly and indirectly presented alloantigens prevented both acute and chronic rejection. Our findings demonstrate the potential of appropriately stimulated regulatory T cells for future cell-based therapeutic approaches to induce lifelong immunological tolerance to allogeneic transplants.

Radiation protocols determine acute graft-versus-host disease incidence after allogeneic bone marrow transplantation in murine models

PURPOSE

Effects of radiation sources used for total body irradiation (TBI) on Graft-versus-Host Disease (GvHD) induction were examined.

MATERIALS AND METHODS

In a T cell receptor (TCR) transgenic mouse model, single fraction TBI was performed with different radiation devices ((60)Cobalt; (137)Cesium; 6 MV linear accelerator), dose rates (0.85; 1.5; 2.9; 5 Gy/min) and total doses before allogeneic bone marrow transplantation (BMT). Recipients were observed for 120 days. Different tissues were examined histologically.

RESULTS

Acute GvHD was induced by a dose rate of 0.85 Gy/min ((60)Cobalt) and a total dose of 9 Gy and injection of 5 x 10(5) lymph node cells plus 5 x 10(6) bone marrow cells. Similar results were obtained using 6 MV linear accelerator- (linac-) photons with a dose rate of 1.5 Gy/min and 0.85 Gy/min, a total dose of 9.5 Gy and injection of same cell numbers. TBI with (137)Cesium (dose rate: 2.5 Gy/min) did not lead reproducibly to lethal acute GvHD.

CONCLUSIONS

Experimental TBI in murine models may induce different immunological responses, depending on total energy, total single dose and dose rate. GvHD might also be induced by TBI with low dose rates.

Survival of transplanted neural progenitor cells enhanced by brain irradiation

OBJECT

Authors of previous studies have reported that adult transplanted neural progenitor cells (NPCs) are suitable for brain cell replacement or gene delivery. In this study, the authors evaluated survival and integration of adult rat-derived NPCs after transplantation and explored the potential impact on transplant survival of various mechanical and biological factors of clinical importance.

METHODS

Adult female Fischer 344 rats were used both as a source and recipient of transplanted NPCs. Both 9L and RG2 rat glioma cells were used to generate in vivo brain tumor models. On the 5th day after tumor implantation, NPCs expressing green fluorescent protein (GFP) were administered either intravenously (3.5 x 10(7) cells) or by stereotactic injection (1 x 10(4)-1 x 10(6) cells) into normal or tumor-bearing brain. The authors evaluated the effect of delivery method (sharp compared with blunt needles, normal compared with zero-volume needles, phosphate-buffered saline compared with medium as vehicle), delivery sites (intravenous compared with intratumoral compared with intraparenchymal), and pretreatment with an immunosuppressive agent (cyclosporin) or brain irradiation (20-40 Gy) on survival and integration of transplanted NPCs.

RESULTS

Very few cells survived when less than 10(5) cells were transplanted. When 10(5) cells or more were transplanted, only previously administered brain irradiation significantly affected survival and integration of NPCs. Although GFP-containing NPCs could be readily detected 1 day after injection, few cells survived 4 days to 1 week unless preceded by whole-brain radiation (20 or 40 Gy in a single fraction), which increased the number of GFP-containing NPCs within the tissue more than fivefold.

CONCLUSIONS

The authors' findings indicate that most NPCs, including those from a syngeneic autologous source, do not survive at the site of implantation, but that brain irradiation can facilitate subsequent survival in both normal and tumor-bearing brain. An understanding of the mechanisms of this effect could lead to improved survival and clinical utility of transplanted NPCs.

The Impact of Chimerism Patterns and Predonor Leukocyte Infusion Lymphopenia on Survival following T Cell-Depleted Reduced Intensity Conditioned Transplants

Donor leukocyte infusions (DLI) are frequently required following reduced intensity conditioned (RIC) allografts to convert mixed chimerism (MC) to full donor chimerism (FDC). The rationale is to break tolerance and maximize the graft-versus-leukemia responses. We analyzed the impact of chimerism in 125 recipients of RIC (Alemtuzumab containing) transplants. Four patterns of chimerism were seen: (1) always 100% donor chimerism (54%), (2) persisting MC (22%), (3) MC with subsequent development of FDC (18%), (4) lost donor chimerism (6%). Forty-five (36%) patients received DLI. Chimerism patterns and pre-DLI lymphocyte counts (pDLI[Ly]) were significantly associated with DLI responsiveness. Complete disease responses were seen in 6 of 17 (35%) group A patients, 9 of 10 (90%) group C patients, and 0 of 6 group B patients (P = .027), supporting reports that chimerism response is a surrogate marker for disease response. In those with MC, pDLI(Ly) were significantly lower in DLI responsive than nonresponsive patients (P = .044). At 2 years, group C patients had a significant survival advantage (P = .009) compared to all other groups. In conclusion, the chimerism pattern was the best indicator of improved survival in this cohort (ie, MC later converting to FDC). In those with MC, response to DLI therapy was associated with a low lymphocyte count pre-DLI.

Diabetes, hypertension, and cardiovascular events in survivors of hematopoietic cell transplantation: a report from the bone marrow transplantation survivor study

We ascertained the prevalence of self-reported late occurrence of diabetes, hypertension, and cardiovascular (CV) disease in 1089 hematopoietic cell transplantation (HCT) survivors who underwent HCT between 1974 and 1998, survived at least 2 years, and were not currently taking immunosuppressant agents and compared them with 383 sibling controls. All subjects completed a 255-item health questionnaire. The mean age at survey completion was 39.3 years for survivors and 38.6 years for siblings; mean follow-up was 8.6 years. Adjusting for age, sex, race, and body mass index (BMI), survivors of allogeneic HCT were 3.65 times (95% confidence interval [CI], 1.82-7.32) more likely to report diabetes than siblings and 2.06 times (95% CI, 1.39-3.04) more likely to report hypertension compared with siblings but did not report other CV outcomes with any greater frequency. Recipients of autologous HCTs were no more likely than siblings to report any of the outcomes studied. Allogeneic HCT survivors were also more likely to develop hypertension (odds ratio [OR]=2.31; 95% CI, 1.45-3.67) than autologous recipients. Total body irradiation (TBI) exposure was associated with an increased risk of diabetes (OR=3.42; 95% CI, 1.55-7.52). Thus, HCT survivors have a higher age- and BMI-adjusted risk of diabetes and hypertension, potentially leading to a higher than expected risk of CV events with age.

Low-dose total body irradiation causes clonal fluctuation of primate hematopoietic stem and progenitor cells

Due to high frequency of side effects caused by high-dose total body irradiation (TBI) the nonmyeloablative regimen together with cytotoxic agents is currently used especially for elderly patients. However, immediate and long-term effects of low-dose irradiation used in allogeneic transplantation on stem cells is less well known. We have studied the effect of low-dose 3 Gy TBI on the number of hematopoietic stem cell (HSC) clones contributing simultaneously to granulocyte production in rhesus macaque. The number of clones after 3 Gy TBI decreased markedly by 2 to 3 weeks after 3 Gy TBI, followed by a period of clonal instability, and recovery to almost pre-3 Gy TBI clonal diversity. The clones accounting for this recovery contributed before 3 Gy TBI, suggesting the profound initial impact of TBI was on a pool of progenitor cells, whereas most of the more primitive HSCs remained unaffected and were able to again contribute to hematopoiesis after recovery. Clonal fluctuation may indirectly suggest the presence of short-term/long-term HSC populations in rhesus macaque bone marrow as reported in a mouse model. The results indicate that even low-dose irradiation affects hematopoietic clonal dynamics and have implications for design of conditioning regimens for transplantation purposes.