Effect of Total Nucleated and CD34(+) Cell Dose on Outcome after Allogeneic Hematopoietic Stem Cell Transplantation

High CD34-positive cell dose in matched unrelated donor allogeneic hematopoietic stem cell transplant is not associated with graft-versus-host disease or mortality

BACKGROUND

CD34+ stem cells serve as the primary graft source for allogeneic transplants, with a minimum of 2-4 × 106 cells/kg needed for engraftment. There are conflicting data on outcomes at high stem cell doses, with studies limited by few patients receiving doses far above the minimum target.

STUDY DESIGN AND METHODS

In this retrospective, single-center study of patients with hematologic malignancies who underwent matched unrelated donor transplants, we assessed outcomes for engraftment, survival, relapse, and graft-versus-host disease (GVHD) for the highest CD34+ dose quintile (>13 × 106 cells/kg, n = 36) compared to the remaining patients (n = 139). Similar analysis was performed correlating T cell dose and outcomes.

RESULTS

There was no difference between the groups in neutrophil engraftment, with a trend toward faster platelet engraftment. There was no significant difference in mortality (adjusted risk ratio [aRR] = 1.02, 95% confidence interval [CI] = 0.85-1.22), relapse (aRR = 1.10, 95% CI = 0.85-1.42), or overall survival by Kaplan-Meier analysis (p = .44). High CD34+ dose was not associated with higher incidence of acute GVHD (aRR = 0.99 grades II-IV, aRR = 1.18 grades III-IV) or chronic GVHD (aRR = 0.87 overall, RR = 1.21 severe). There was limited correlation between CD34+ and T cell dose (R2 = .073), and there was no significant difference in survival, relapse, or GVHD in the highest T cell dose quintile (n = 33) compared to the remaining quintiles (n = 132).

DISCUSSION

We found no difference in survival, relapse, or GVHD incidence or severity in patients receiving CD34+ doses above prior cutoffs reported in the literature. These data do not support the routine use of graft CD34+ dose reduction.

Graft Failure Incidence, Risk Factors, and Outcomes in Patients Undergoing Non-Myeloablative Allogeneic Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide

Graft failure (GF) is a major complication of allogeneic hematopoietic cell transplantation (alloHCT) that results in significant morbidity and mortality. Post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has emerged as an effective regimen across the spectrum of donor-match settings, but few studies have investigated the characteristics of GF in the setting of PTCy-based GVHD prophylaxis. The objective was to detail the incidence, clinical features, risk factors, and outcomes for patients with primary graft failure (PGF) and secondary graft failure (SGF). In this retrospective study at a single institution, 958 consecutive patients undergoing first nonmyeloablative (NMA) alloHCT with PTCy-based GVHD prophylaxis were analyzed. PGF was defined as a failure to achieve an ANC ≥ 500 cells/m3 by day 30 of transplant in the absence of residual disease. SGF was defined as complete loss of donor chimerism after initial engraftment. The incidences of PGF and SGF were 3.8% (n = 37) and 1.8% (n = 17), respectively. Neither PGF nor SGF were associated with HLA disparity. In a multivariate analysis, risk factors for PGF in this cohort included age ≥ 65 (OR 2.4, 95% CI 1.2 to 4.8, P = .0120), an underlying diagnosis of MDS, MPN, or MDS/MPN overlap (OR 2.8, 95% CI 1.4 to 5.7, P = .0050), post-transplant viremia with HHV-6 (OR 2.9, 95% CI 1.5 to 5.7, P = .0030), and low CD34+ dose (OR 0.7, 95% CI 0.5 to 0.9, P = .0080). Patients with PGF had poor overall survival, driven primarily by a high rate of nonrelapse mortality (59% at 36 months). SGF was associated with use of a bone marrow graft source and a diagnosis of Hodgkin lymphoma. Patients with SGF had excellent clinical outcomes with only one of seventeen patients experiencing relapse and relapse-related mortality. The incidence of PGF and SGF in patients receiving NMA conditioning and PTCy is low and is not impacted by HLA disparities between donors and recipients. PGF is more common in recipients with age ≥ 65, a diagnosis of MDS, MPN, or MDS/MPN-overlap, post-transplant HHV-6 viremia, and low CD34+ cell dose. Low total nucleated cell dose is also a risk factor for PGF in patients receiving a bone marrow graft source. Patients who experience PGF have poor outcomes due to high rates of nonrelapse mortality, whereas patients who experience SGF have excellent long-term outcomes.

Advances in hematopoietic stem cells ex vivo expansion associated with bone marrow niche

Hematopoietic stem cells (HSCs) are an ideal source for the treatment of many hematological diseases and malignancies, as well as diseases of other systems, because of their two important features, self-renewal and multipotential differentiation, which have the ability to rebuild the blood system and immune system of the body. However, so far, the insufficient number of available HSCs, whether from bone marrow (BM), mobilized peripheral blood or umbilical cord blood, is still the main restricting factor for the clinical application. Therefore, strategies to expand HSCs numbers and maintain HSCs functions through ex vivo culture are urgently required. In this review, we outline the basic biology characteristics of HSCs, and focus on the regulatory factors in BM niche affecting the functions of HSCs. Then, we introduce several representative strategies used for HSCs from these three sources ex vivo expansion associated with BM niche. These findings have deepened our understanding of the mechanisms by which HSCs balance self-renewal and differentiation and provided a theoretical basis for the efficient clinical HSCs expansion.

Effects of CD34+ cell dose on engraftment and long-term outcomes after allogeneic bone marrow transplantation

BACKGROUND

The number of CD34+ cells in the graft is generally associated with time to engraftment and survival in transplantation using cord blood or allogeneic peripheral blood stem cells. However, the significance of abundant CD34+ in bone marrow transplantation (BMT) remained unclear.

METHODS

We retrospectively reviewed 207 consecutive adult patients who underwent their first BMT at Jichi Medical University between January 2009 and June 2021.

RESULTS

The median nucleated cell count (NCC) and CD34+ cell dose were 2.17 × 108/kg (range .56-8.52) and 1.75 × 106/kg (.21-5.84), respectively. Compared with 104 patients in the low CD34+ group (below the median), 103 patients in the high CD34+ group (above the median) showed faster engraftment at day +28 in terms of neutrophil (84.6% vs. 94.2%; p =  .001), reticulocyte (51.5% vs. 79.6%; p < .001), and platelet (39.4% vs. 72.8%; p < .001). There were no significant differences in overall survival, relapse, nonrelapse mortality, acute or chronic graft-versus-host disease, or infectious complications between the two groups in univariate and multivariate analyses. Low or high NCC had no significant effect on overall survival, nonrelapse mortality, cumulative incidence of relapse and graft-versus-host disease, either. While a positive correlation was observed between NCC and the CD34+ cell dose, a high CD34+ cell dose was associated with rapid hematopoietic recovery, even in patients with NCC below the median.

CONCLUSION

Measurement of CD34+ cell dose in addition to NCC was useful for predicting hematopoietic recovery, but seemed to have little influence on the long-term outcome in BMT.

Harvest Quality, Nucleated Cell Dose and Clinical Outcomes in Bone Marrow Transplantation: A Retrospective Study

Higher doses of infused nucleated cells (NCs) are associated with improved clinical outcomes in bone marrow transplantation (BMT) recipients. Most clinicians recommend infusing at least 2.0 × 108 NCs/kg. BMT clinicians request a target NC dose, but the harvested NC dose may be below the requested NC dose even before cell processing. We conducted this retrospective study to investigate the quality of bone marrow (BM) harvest and factors that influence infused NC doses at our institution. We also correlated infused NC doses with clinical outcomes. The study population included 347 BMT recipients (median age, 11 years; range, <1 to 75 years) at the University of Minnesota between 2009 and 2019. Underlying diagnoses mainly included 39% malignant and 61% nonmalignant diagnoses. Requested, harvested, and infused NC doses, as well as cell processing data, were obtained from the Cell Therapy Laboratory; clinical outcomes data were obtained from the University of Minnesota BMT Database. BM harvests were facilitated either by our institution (61%) or by the National Marrow Donor Program (39%). Associations of infused doses with baseline characteristics were assessed using the general Wilcoxon test/Pearson's correlation coefficient. The association of infused dose with neutrophil engraftment (absolute neutrophil count >500) by day 42, platelet engraftment (>20,000) by 6 months, acute graft-versus-host disease grade II-IV, and overall survival (OS) at 5 years were evaluated using regression and Kaplan-Meier curves. The median requested NC dose was 3.0 × 108/kg (range, 2 to 8 × 108/kg), and the median harvested and infused NC doses were 4.0 × 108/kg and 3.6 × 108/kg, respectively. Only 7% of donors had a harvested dose below the minimum requested dose. Moreover, the correlation between requested doses and harvested doses was adequate, with a harvested/requested dose ratio <.5 observed in only 5% of harvests. Additionally, the harvest volume and cell processing method were significantly correlated with the infused dose. Harvest volume exceeding the median of 948 mL was related to a significantly lower infused dose (P < .01). Moreover, hydroxyethyl starch (HES)/buffy coat processing (used to reduce RBCs with major ABO incompatibility) led to a significantly lower infused dose (P < .01). Donor age (median, 19 years; range, <1 to-70 years) and sex did not significantly influence the infused dose. Finally, the infused dose was significantly correlated with neutrophil and platelet engraftment (P < .05) but not with 5-year OS (P = .87) or aGVHD (P = .33). In our program's experience, BM harvesting is efficient and meets the requested minimum dose for 93% of recipients. Harvest volume and cell process play significant roles in determining the final infused dose. Minimizing harvest volume and cell processing could lead to increased infused dose and thus improved outcomes. Moreover, a higher infused dose leads to a better rate of neutrophil and platelet engraftment but not to improved OS, which may be linked to the sample size of our study.

Flow Cytometric Characterization of Hematopoietic Stem and Progenitor Cell Subpopulations in Autologous Peripheral Blood Stem Cell Preparations after Cryopreservation

Introduction

Autologous stem cell transplantation is a successful routine procedure with only a small number of non-engraftment cases, although the time to hematopoietic recovery may vary considerably across patients. While CD34 has been the decisive marker for enumerating hematopoietic stem and progenitor cells (HSPCs) for more than 30 years, the impact of CD34-positive cellular subpopulations in autologous HSPC grafts on hematopoietic reconstitution remains unclear.

Methods

The two-color ISHAGE protocol represents the current gold standard for CD34+ cell enumeration but includes only the number of viable CD45+/CD34+ cells relative to the body weight of the recipient. We adapted a multicolor flow cytometry marker panel for advanced characterization of CD34 subpopulations in retained samples of autologous peripheral blood stem cell products (n = 49), which had been cryostored for a wide range from 4 to 15 years. The flow cytometric analysis included CD10, CD34, CD38, CD45, CD45RA, CD133, and viability staining with 7AAD. The findings were correlated with clinical engraftment data, including reconstitution of leukocytes, neutrophils, and platelets after transplantation (TPL).

Results

We demonstrated that the identification of autologous HSPC subpopulations by flow cytometry after cryopreservation is feasible. Regarding the distribution of HSPC subpopulations, a markedly different pattern was observed in comparison to previously published data obtained using fresh autologous material. Our data revealed the largest ratio of lympho-myeloid progenitors (LMPPs) after freezing and thawing, followed by multipotent progenitors and erythroid-myeloid progenitors. A high ratio of LMPPs, representing an immature stage of differentiation, correlated significantly with early neutrophilic granulocyte and leukocyte engraftment (p = 0.025 and p = 0.003). Conversely, a large ratio of differentiated cells correlated with late engraftment of neutrophilic granulocytes (p = 0.024). Overall, successful engraftment was documented for all patients.

Conclusion

We established an advanced flow cytometry panel to assess the differentiation ability of cryostored autologous peripheral blood stem cell grafts and correlated it with timely hematopoietic reconstitution. This approach represents a novel and comprehensive way to identify hematopoietic stem and progenitor subpopulations. It is a feasible way to indicate the engraftment capacity of stem cell products.

Cryopreservation of Allogeneic Hematopoietic Cell Products During COVID-19 Pandemic: Graft Characterization and Engraftment Outcomes

BACKGROUND

The COVID-19 pandemic triggered the deployment of unfamiliar measures to safeguard successful allogeneic hematopoietic cell transplantation (allo-HCT). Among these measures, cryopreservation offered logistical benefits that could outlast the pandemic, including graft availability and timely clinical service. The purpose of this study was to evaluate graft quality and hematopoietic reconstitution in patients transplanted with cryopreserved allogeneic stem cell products during the COVID-19 pandemic.

METHODS

We evaluated 44 patients who underwent allo-HCT using cryopreserved grafts consisting of hematopoietic progenitor cells (HPC) apheresis (A) and bone marrow (BM) products at Mount Sinai Hospital. Comparative analyses of 37 grafts infused fresh during the one-year period preceding the pandemic were performed. Assessment of cellular therapy products included total nucleated cell and CD34+ cell enumeration, viability, and post-thaw recovery. The primary clinical endpoint was the evaluation of engraftment (absolute neutrophil count [ANC] and platelet count) and donor chimerism (presence of CD33+ and CD3+ donor cells) at day +30 and +100 post-transplant. Adverse events related to cell infusion were also analyzed.

RESULTS

Patient characteristics were comparable between the fresh and cryopreserved groups with 2 exceptions in the HPC-A cohort: the number of patients in the cryopreserved group that received haploidentical grafts was 6 times that in the fresh group, and the number of patients in the fresh group with a Karnofsky performance score >90 was double that in the cryopreserved group. The quality of HPC-A and HPC-BM products was not affected by cryopreservation, and all grafts met the release criteria for infusion. The pandemic did not affect the time between collection and cryopreservation (median, 24 hours) and time in storage (median, 15 days). Median time to ANC recovery was significantly delayed in recipients of cryopreserved HPC-A (15 vs 11 days, P = .0121), and there was a trend toward delayed platelet engraftment (24 vs 19 days, P = .0712). The delay in ANC and platelet recovery was not observed when only matched graft recipients were compared. Cryopreservation did not affect the ability of HPC-BM grafts to engraft and reconstitute hematopoiesis, and there was no difference in the rates of ANC and platelet recovery. Achievement of donor CD3/CD33 chimerism was not affected by cryopreservation of either HPC-A or HPC-BM products. Graft failure was observed in only 1 case, a recipient of cryopreserved HPC-BM. Three recipients of cryopreserved HPC-A grafts died before ANC engraftment from infectious complications. Remarkably, 22% of our studied population had myelofibrosis, and almost half received cryopreserved HPC-A grafts with no graft failure observed. Finally, patients receiving cryopreserved grafts were at a higher risk of infusion-related adverse events than those receiving fresh grafts.

CONCLUSIONS

Cryopreservation of allogeneic grafts results in adequate product quality with minimal impact on short-term clinical outcomes, except for an increased risk of infusion-related adverse events. Cryopreservation is a safe option in terms of graft quality and hematopoietic reconstitution with logistical benefits, but additional data are needed to determine long-term outcomes and assess whether this is a suitable strategy for at-risk patients.

Infections and risk factors for infection-related mortality after pediatric allogeneic hematopoietic stem cell transplantation in Mexico: A single center retrospective study

OBJECTIVE

To identify the type of infections and risk factors for infection-related mortality (IRM) after allogeneic hematopoietic stem cell transplantation (HSCT).

METHODS

Retrospective cohort study of patients <16 years of age treated in 2010-2019 was conducted. Unadjusted hazard ratios (HR) and adjusted hazard ratios (aHR) with 95% confidence intervals (95% CIs) were estimated using Cox regression. Cumulative incidence was calculated.

RESULTS

Data for 99 pediatric patients were analyzed. The myeloablative conditioning was the most used regimen (78.8%) and the hematopoietic stem cell source was predominantly peripheral blood (80.8%). Primary graft failure occurred in 19.2% of patients. Frequency of acute graft-versus-host disease was 46.5%. Total of 136 infectious events was recorded, the most common of which were bacterial (76.4%) followed by viral infection (15.5%) and then fungal infection (8.1%). The best predictors for infection subtypes where the following: a) for bacterial infection (the age groups of 10.1-15 years: aHR = 3.33; 95% CI: 1.62-6.85 and. >15 years: aHR = 3.34; 95% CI: 1.18-9.45); b) for viral infection (graft versus host disease: aHR = 5.36; 95% CI: 1.62-17.68), however, for fungal infection statistically significant predictors were not identified. Related mortality was 30% (n = 12). Increased risk for infection-related mortality was observed in patients with unrelated donor and umbilical cord stem cells recipients (HR = 3.12; 95% CI: 1.00-9.85).

CONCLUSIONS

Frequencies of infections and infection-related mortality appear to be similar to those reported. Unrelated donors and stem cells from umbilical cord recipients were associated with a high risk of mortality.

Small volume bone marrow aspirates with high progenitor cell concentrations maximize cell therapy dose manufacture and substantially reduce donor hemoglobin loss

BACKGROUND

Bone marrow (BM) transplantation is a life-saving therapy for hematological diseases, and the BM harbors also highly useful (progenitor) cell types for novel cell therapies manufacture. Yet, the BM collection technique is not standardized.

METHODS

Benchmarking our collection efficiency to BM collections worldwide (N = 1248), we noted a great variability of total nucleated cell (TNC) yields in BM products (HPC-M) with superior performance of our center, where we have implemented a small volume aspirate policy. Thus, we next prospectively aimed to assess the impact of BM collection technique on HPC-M quality. For each BM collection (N = 20 donors), small volume (3 mL) and large volume (10 mL) BM aspirates were sampled at 3 time points and analyzed for cell composition.

RESULTS

Compared to large volume aspirates, small volume aspirates concentrated more TNCs, immune cells, platelets, hematopoietic stem/progenitor cells, mesenchymal stromal cells (MSCs), and endothelial progenitors. Inversely, the hemoglobin concentration was higher in large volume aspirates indicating more hemoglobin loss. Manufacturing and dosing scenarios showed that small volume aspirates save up to 42% BM volume and 44% hemoglobin for HPC-M donors. Moreover, MSC production efficiency can be increased by more than 150%.

CONCLUSIONS

We propose to consider small volume BM aspiration as standard technique for BM collection.

Nomogram for Predicting Early Mortality after Umbilical Cord Blood Transplantation in Children with Inborn Errors of Immunity

PURPOSE

Pediatric patients with inborn errors of immunity (IEI) undergoing umbilical cord blood transplantation (UCBT) are at risk of early mortality. Our aim was to develop and validate a prediction model for early mortality after UCBT in pediatric IEI patients based on pretransplant factors.

METHODS

Data from 230 pediatric IEI patients who received their first UCBT between 2014 and 2021 at a single center were analyzed retrospectively. Data from 2014-2019 and 2020-2021 were used as training and validation sets, respectively. The primary outcome of interest was early mortality. Machine learning algorithms were used to identify risk factors associated with early mortality and to build predictive models. The model with the best performance was visualized using a nomogram. Discriminative ability was measured using the area under the curve (AUC) and decision curve analysis.

RESULTS

Fifty days was determined as the cutoff for distinguishing early mortality in pediatric IEI patients undergoing UCBT. Of the 230 patients, 43 (18.7%) suffered early mortality. Multivariate logistic regression with pretransplant albumin, CD4 (absolute count), elevated C-reactive protein, and medical history of sepsis showed good discriminant AUC values of 0.7385 (95% CI, 0.5824-0.8945) and 0.827 (95% CI, 0.7409-0.9132) in predicting early mortality in the validation and training sets, respectively. The sensitivity and specificity were 0.5385 and 0.8154 for validation and 0.7667 and 0.7705 for training, respectively. The final model yielded net benefits across a reasonable range of risk thresholds.

CONCLUSION

The developed nomogram can predict early mortality in pediatric IEI patients undergoing UCBT.

Day 4 collection of granulocyte colony-stimulating factor-mobilized HLA-matched sibling donor peripheral blood allografts demonstrates no long-term increase in chronic graft-versus-host disease or relapse rates

BACKGROUND AIMS

In a previous pilot study of HLA-matched sibling donor hematopoietic cell transplantation (HCT), the authors determined the feasibility of day 4 versus day 5 granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cell (PBSC) collection compared with a historical cohort. Given identified differences in the PBSC product (day 4 cohort with significantly lower infused total nucleated, mononuclear and CD3 cells compared with other collection cohorts), the authors performed a follow-up study to determine long-term post-HCT outcomes, including detailed characterization of chronic graft-versus-host disease (GVHD).

METHODS

This was a prospective observational study, and the authors collected data on chronic GVHD, staging, sites of involvement and treatments. Performance status, incidence of relapse, overall survival and duration of immunosuppressive therapy (IST) were also evaluated. Data were examined retrospectively. To account for differences in length of follow-up among cohorts, the authors also determined performance status and chronic GVHD staging, sites and treatment at 2 years post-HCT.

RESULTS

At 2 years post-HCT, the overall survival rate was 71.7% in the day 4 cohort compared with 61.5%, 52% and 56% in the day 5, 2-day and historical cohorts, respectively (P = 0.283). The cumulative incidence of chronic GVHD was 65.2% in the day 4 cohort versus 46.4% in the day 5 cohort, 51.1% in the 2-day cohort and 65% in the historical cohort (P = 0.26). There was no significant difference in the maximum overall stage of chronic GVHD (P = 0.513), median number of sites involved (P = 0.401) or cumulative incidence of discontinuation of IST (P = 0.32). Death from chronic GVHD was less common in the day 4 and day 5 cohorts compared with the 2-day and historical cohorts, though this did not reach statistical significance.

CONCLUSIONS

The authors' preliminary results demonstrated that collection of allogeneic matched sibling donor PBSCs on day 4 of G-CSF was feasible, reduced donor exposure to growth factor and was associated with an initial cost savings. Importantly, the authors now demonstrate that transplantation of day 4 mobilized PBSCs is not associated with any adverse outcomes post-HCT, including late effects such as chronic GVHD. Further investigation of donor G-CSF collection algorithms is merited in other HCT settings, including unrelated and mismatched related donors.

The Effect of the COVID-19 Pandemic on Unrelated Allogeneic Hematopoietic Donor Collections and Safety

BACKGROUND AND OBJECTIVES

The COVID-19 pandemic profoundly influenced unrelated donor (UD) allogeneic peripheral blood stem cell (PBSC) collections. Changes included efforts to minimize COVID-19 exposure to donors and cryopreservation of products. The extent to which the efficacy and safety of PBSC donations were affected by the pandemic is unknown.

METHODS

Prospective cohort analysis of PBSC collections comparing pre-pandemic (01 April 2019-14 March 2020) and pandemic (15 March 2020-31 March 2022) eras.

RESULTS

Of a total of 291 PBSC collections, cryopreservation was undertaken in 71.4% of pandemic donations compared to 1.1% pre-pandemic. The mean requested CD34⁺ cell dose/kg increased from 4.9 ± 0.2 × 10⁶ pre-pandemic to 5.4 ± 0.1 × 10⁶ during the pandemic. Despite this increased demand, the proportion of collections that met or exceeded the requested cell dose did not change, and the mean CD34⁺ cell doses collected (8.9 ± 0.5 × 10⁶ pre-pandemic vs. 9.7 ± 0.4 × 10⁶ during the pandemic) remained above requested targets. Central-line placements were more frequent, and severe adverse events in donors increased during the pandemic.

CONCLUSION

Cryopreservation of UD PBSC products increased during the pandemic. In association with this, requested cell doses for PBSC collections increased. Collection targets were met or exceeded at the same frequency, signaling high donor and collection center commitment. This was at the expense of increased donor or product-related severe adverse events. We highlight the need for heightened vigilance about donor safety as demands on donors have increased since the pandemic.

Effect of CD34+ Cell Dose on the Outcomes of Allogeneic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide

The impact of infused CD34⁺ cell dose on outcomes after allogeneic hematopoietic stem cell transplantation (alloHSCT) using standard graft-versus-host disease (GVHD) prophylaxis remains controversial. Information on this subject is scarce for alloHSCT using high-dose post-transplantation cyclophosphamide (PTCy). We aimed to assess the effect of CD34⁺ cell dose in peripheral blood stem cell (PBSC) grafts on the outcome of alloHSCT using PTCy-based GVHD prophylaxis. To do so, we conducted a single-center retrospective analysis of 221 consecutive adult patients who underwent PTCy alloHSCT from HLA-matched sibling donors (MSDs; n = 22), HLA-matched unrelated donors (MUDs; n = 83), mismatched unrelated donors (MMUDs; n = 73), and haploidentical donors (n = 43). Based on the binary partitioning method, 5 × 10⁶/kg was used as the optimal cutoff for CD34⁺ cell dose. According to our institutional protocol, the maximum CD34⁺ cell dose was capped at 8 × 10⁶/kg. The study cohort was divided into 2 groups based on CD34⁺ cell dose: high dose (>5 to 8 × 10⁶/kg) and low dose (≤5 × 10⁶/kg). Patients receiving high-dose CD34⁺-containing grafts had significantly shorter median times to neutrophil engraftment and platelet engraftment compared to those who received low-dose CD34+ (19 days versus 21 days [P = .002] and 16 days versus 22 days [P = .04], respectively). There were no differences between the high-dose and low-dose groups in the cumulative incidence of day +100 acute GVHD (grade II-IV: 25% versus 23% [P = .7]; grade III-IV: 5% versus 4% [P = .4], respectively) or 2-year chronic GVHD (moderate/severe GVHD: 9% versus 6%; P = .5). There was no impact of CD34⁺ cell dose on survival outcomes with the use of MSDs, MUDs, or MMUDs. Recipients of haploidentical alloHSCT using low-dose CD34⁺ cells had significantly worse overall survival (hazard ratio [HR], 6.01; P = .004) and relapse-free survival (HR, 4.57; P = .004). In recipients of PBSC PTCy alloHSCT, infused CD34⁺ cell doses >5 to 8 × 10⁶/kg were associated with faster neutrophil and platelet engraftment, independent of donor type. Our study suggests an impact of CD34⁺ cell dose on survival outcomes only with haploidentical donors, for whom the administration of a CD34⁺ cell dose ≤5 × 10⁶/kg significantly decreased survival outcomes.

Effects of CD34+ cell dose on haematopoietic recovery in acute lymphoblastic leukaemia patients with positive pretransplant measurable residual disease

INTRODUCTION

A higher CD34⁺ cell dose in allografts is associated with faster haematopoietic recovery after allogeneic haematopoietic stem cell transplantation (allo-HSCT). Leukaemia stem cells impair normal bone marrow (BM) niches and induce BM failure during leukemogenesis. However, whether measurable residual disease (MRD), known as the persistence of low-level leukaemic cells, could influence the effects of CD34⁺ cell dose on haematopoietic recovery after transplantation in acute lymphoblastic leukaemia (ALL) patients is unknown.

METHODS

A total of 975 ALL patients were enrolled and classified into pre-HSCT MRD-positive and MRD-negative subgroups. Cox proportional hazard regression models were built for time-to-event outcomes. Multivariate analysis was performed to determine independent influencing factors from the univariate analysis.

RESULTS

An appropriate CD34⁺ cell dose was positively associated with faster haematopoietic recovery in the total ALL population. More importantly, in pre-HSCT MRD-positive ALL patients, a higher CD34⁺ cell dose (≥2.76 × 10⁶ /kg) was related to faster neutrophil (HR 1.330, 95% CI 1.045-1.692, p = 0.021) and platelet engraftment (HR 1.808, 95% CI 1.412-2.316, p < 0.001) in multivariate analysis. CD34⁺ cell dose was a crucial factor associated with either engraftment or transplant outcomes, although we did not demonstrate direct correlations of CD34⁺ cell dose with relapse, TRM, LFS or OS after allo-HSCT.

CONCLUSION

Our results indicated that no additional CD34⁺ stem and progenitor cell harvests were needed to ensure successful haematopoietic recovery in pre-HSCT MRD-positive patients compared to pre-HSCT MRD-negative patients.

Stemness-related genes revealed by single-cell profiling of naïve and stimulated human CD34+ cells from CB and mPB

BACKGROUND

Hematopoietic stem cells (HSCs) from different sources show varied repopulating capacity, and HSCs lose their stemness after long-time ex vivo culture. A deep understanding of these phenomena may provide helpful insights for HSCs.

METHODS

Here, we applied single-cell RNA-seq (scRNA-seq) to analyse the naïve and stimulated human CD34+ cells from cord blood (CB) and mobilised peripheral blood (mPB).

RESULTS

We collected over 16 000 high-quality single-cell data to construct a comprehensive inference map and characterised the HSCs under a quiescent state on the hierarchy top. Then, we compared HSCs in CB with those in mPB and HSCs of naïve samples to those of cultured samples, and identified stemness-related genes (SRGs) associated with cell source (CS-SRGs) and culture time (CT-SRGs), respectively. Interestingly, CS-SRGs and CT-SRGs share genes enriched in the signalling pathways such as mRNA catabolic process, translational initiation, ribonucleoprotein complex biogenesis and cotranslational protein targeting to membrane, suggesting dynamic protein translation and processing may be a common requirement for stemness maintenance. Meanwhile, CT-SRGs are enriched in pathways involved in glucocorticoid and corticosteroid response that affect HSCs homing and engraftment. In contrast, CS-SRGs specifically contain genes related to purine and ATP metabolic process, which is crucial for HSC homeostasis in the stress settings. Particularly, when CT-SRGs are used as reference genes for the construction of the development trajectory of CD34+ cells, lymphoid and myeloid lineages are clearly separated after HSCs/MPPs. Finally, we presented an application through a small-scale drug screening using Connectivity Map (CMap) against CT-SRGs. A small molecule, cucurbitacin I, was found to efficiently expand HSCs ex vivo while maintaining its stemness.

CONCLUSIONS

Our findings provide new perspectives for understanding HSCs, and the strategy to identify candidate molecules through SRGs may be applicable to study other stem cells.

Von Willebrand Factor and Platelet Levels before Conditioning Chemotherapy Indicate Bone Marrow Regeneration following Autologous Hematopoietic Stem Cell Transplantation

Autologous hematopoietic stem cell transplantation (HSCT) is often complicated by hemostatic and thrombotic events associated with endothelial cell injury. Thrombotic complications are affected by a disturbed balance between platelets, circulating von Willebrand factor (VWF), and its specific protease, ADAMTS13. HSCT-associated endothelial dysfunction, impaired hemostasis, and inflammation are interrelated processes, and research on the complex interplay of conditioning regimens from engraftment to bone marrow regeneration remains intensive. This prospective observational study comparing lymphoma and multiple myeloma (MM) patients who underwent autologous HSCT explored how platelet count, VWF level, ADAMTS13 activity, and C-reactive protein (CRP) level as potential markers (1) vary in response to therapy, (2) differ between the 2 groups, and (3) correlate with the remission state at 100 days after HSCT. We correlated the quantitative changes in platelet count and levels of VWF, ADAMTS13, and CRP with one another during HSCT and in the remission state in 45 patients with lymphoma and 59 patients with MM who underwent autologous HSCT between 2010 and 2013 at the University of Debrecen. Samples were collected at the start of conditioning chemotherapy, on the day of stem cell transplantation, and at 5, 11, and 100 days following HSCT. CRP levels peaked when platelet counts dropped to a minimum, and these changes were much more pronounced in the lymphoma group. VWF level was the highest, with lower ADAMTS13 activity, at platelet engraftment in both patient groups equally. Diagnostic evidence indicative of thrombotic complications was not found. In the lymphoma group, VWF level prior to conditioning had statistically significant correlations with platelet count, CRP level, and hemoglobin concentration at the time of bone marrow regeneration (P < .001) and during the remission state (P = .034). In the MM group, platelet count before conditioning was correlated with platelet count (P < .001) and white blood cell count (P = .012) at the time of bone marrow regeneration. The statistically significant correlation of the markers at the time of bone marrow regeneration with the preconditioning VWF levels in lymphoma and with the preconditioning platelet counts in MM might indicate the clinical significance of the bone marrow niches of arterioles and megakaryocytes, respectively, where the stem cells are located and regulated. Because preconditioning VWF levels are associated with remission after HSCT in lymphoma patients, VWF should be screened before conditioning, along with the markers used in HSCT protocols, to optimize personalized treatment and reduce therapeutic risks.

Allogeneic peripheral blood haematopoietic stem cell transplantation for the treatment of dogs with high-grade B-cell lymphoma

Autologous peripheral blood haematopoietic stem cell transplantation (HCT) cures 33%-40% of dogs with high-grade B-cell lymphoma. We hypothesized, based on human allogeneic bone marrow transplantation literature, that transplanting dogs using canine donor leukocyte-matched CD34+ cells would lead to fewer relapses and increased cure rates. We retrospectively reviewed medical records of dogs diagnosed with high-grade B-cell lymphoma who received an identical allogeneic HCT. A total of 15 dogs transplanted at four facilities were identified. Five of fifteen dogs relapsed before transplant. The mean number of donor CD34+ cells/kg harvested and infused into recipient dogs was 8.0 × 10⁶ /kg (range: 2.08 × 10⁶ /kg-2.9 × 10⁷ /kg). The median disease-free interval and overall survival of all dogs was 1095 days (range: 9-2920 days) and 1115 days (range: 9-2920 days), respectively. Two of five dogs, not in remission at transplant, died in the hospital. The median disease-free interval and overall survival of the remaining three dogs was 25 days (range: 15-250 days) and 1100 days (range: 66-1902 days), respectively. The median disease-free interval and overall survival of the 10 dogs who had not relapsed was 1235 days (range: 19-2920 days) and 1235 days (range: 19-2920 days), respectively. One dog died soon after discharge of presumed gastric-dilatation-volvulus. Eight of nine remaining dogs lived >4 yrs post-alloHCT, leading to a cure rate of 89%. Acute graft versus host disease was seen in three dogs. These results suggest that allogeneic HCT can cure ~50% more dogs than those treated with autologous HCT.

Autologous hematopoietic stem cell transplantation in neuromyelitis optica spectrum disorder: A systematic review and meta-analysis

INTRODUCTION

Treatment options for neuromyelitis optica spectrum disorder (NMOSD) are corticosteroids, immunosuppressive drugs, emerging monoclonal antibodies, rituximab, eculizumab, satralizumab, and inebilizumab. Due to disabling and deadly nature of NMOSD, there is a great motivation among physicians for finding new treatment options. Recently, several studies have been conducted on the therapeutic effects of autologous hematopoietic stem cell transplantation (AHSCT) on NMOSD patients.

METHODS

Several databases including PubMed, Scopus, Web of Science, and Google scholar were searched for studies on AHSCT in NMOSD patients.

RESULTS

After screening titles and abstracts, and reviewing full texts, nine studies with 39 severe cases of NMOSD met the criteria of our study. The pooled standardized mean difference (SMD) for EDSS score before and after treatment was -0.81 (95 %CI:-1.07, -0.15; Q = 1.99, P = 0.58, I2 = 0 %). Also, the PFS and RFS were 69 % and 53 % respectively (PFS: 69 %, 95 %CI 42 %, 96 %; Q = 8.63, P = 0.01, I2 = 73.07 %; RFS: 53 %, 95 %CI 27 %, 79 %; Q = 12.33, P = 0.01, I2 = 71.87 %). Also, there were three cases with secondary autoimmune diseases including myasthenia gravis, hyperthyroidism, and thyroiditis.

CONCLUSION

According to the present study, AHSCT could be an alternative therapy for NMOSD in severe cases instead of conventional immunotherapies. However, physicians should pay attention to its serious complications. The diversity of results from the published trials on the efficacy and safety of AHSCT calls for further investigations on determining the ideal AHSCT conditioning and the characteristics of patients.

Association between haploidentical hematopoietic stem cell transplantation combined with an umbilical cord blood unit and graft-versus-host disease in pediatric patients with acquired severe aplastic anemia

Background:

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) based on granulocyte colony-stimulating factor plus anti-thymocyte regimens (‘Beijing Protocol’) provides a salvage treatment for patients of acquired severe aplastic anemia (SAA) in China. However, graft-versus-host disease (GVHD) is a major impediment of haplo-HSCT due to human leukocyte antigen disparity. Recently, haplo-HSCT combined with umbilical cord blood (UCB) (haplo-cord HSCT) is performed in clinical trials to potentially reduce the risk of severe GVHD. Nevertheless, studies comparing GVHD in pediatric patients receiving haplo and haplo-cord HSCT for SAA are limited.

Objective:

The objective of this study was to investigate the impact of UCB co-infusion on GVHD in pediatric patients receiving haplo-HSCT for SAA.

Design:

We conducted a retrospective study of 91 consecutive SAA children undergoing haploidentical transplantation based on the ‘Beijing Protocol’ with or without co-infusion of UCB in our center.

Methods:

All patients received uniform non-myeloablative conditioning and GVHD prophylaxis. We compared baseline characteristics and transplant outcomes between the haplo (n = 35) and haplo-cord (n = 56) recipients.

Results:

All 91 patients achieved hematopoietic recovery from haploidentical donors, with a higher incidence of peri-engraftment syndrome observed with the haplo-cord group as compared with the haplo group (75.0% versus 48.6%, p = 0.029). Notably, the haplo-cord group showed a lower incidence of II–IV acute GVHD (aGVHD) than the haplo group (16.1% versus 42.9%, p = 0.002). Observed incidences of chronic GVHD (cGVHD) and moderate to severe cGVHD in the haplo-cord group were also lower than that in the haplo group (25.6% versus 51.3%, p = 0.019; 16.2% versus 41.3%, p = 0.016, respectively). Haplo-cord HSCT was identified as the only factor associated with a lower incidence of II–IV aGVHD and cGVHD in multivariate analysis. However, no differences were observed between the two groups for infections and survival outcomes.

Conclusion:

Our data indicated that co-infusion of UCB in ‘Beijing Protocol’-based haplo-HSCT may be effective for reducing the risk of severe GVHD in SAA children.

Injectable bone marrow microniches by co-culture of HSPCs with MSCs in 3D microscaffolds promote hematopoietic reconstitution from acute lethal radiation

Hematopoietic syndrome of acute radiation syndrome (h-ARS) is an acute illness resulted from the damage of bone marrow (BM) microenvironment after exposure to radiation. Currently, the clinical management of h-ARS is limited to medication-assisted treatment, while there is still no specific therapy for the hematopoietic injury from high-dose radiation exposure. Our study aimed to assemble biomimetic three-dimensional (3D) BM microniches by co-culture of hematopoietic stem and progenitor cells (HSPCs) and mesenchymal stem cells (MSCs) in porous, injectable and viscoelastic microscaffolds in vitro. The biodegradable BM microniches were then transplanted in vivo into the BM cavity for the treatment of h-ARS. We demonstrated that the maintenance of HSPCs was prolonged by co-culture with MSCs in the porous 3D microscaffolds with 84 μm in pore diameter and 11.2 kPa in Young's modulus compared with 2D co-culture system. Besides, the minimal effective dose and therapeutic effects of the BM microniches were investigated on a murine model of h-ARS, which showed that the intramedullary cavity-injected BM microniches could adequately promote hematopoietic reconstitution and mitigate death from acute lethal radiation with a dose as low as 1000 HSPCs. Furthermore, the mRNA expression of Notch1 and its downstream target gene Hes1 of HSPCs were increased when co-cultured with MSCs, while the Jagged1 expression of the co-cultured MSCs was upregulated, indicating the significance of Notch signaling pathway in maintenance of HSPCs. Collectively, our findings provide evidence that biomimetic and injectable 3D BM microniches could maintain HSPCs, promote hematopoiesis regeneration and alleviate post-radiation injury, which provides a promising approach to renovate conventional HSPCs transplantation for clinical treatment of blood and immune disorders.

Bone Marrow Grafts From Pediatric Donors May Contain A Considerable Number of Hematogones

During CD34 + stem cell count to determine the number of stem cells in the allografts from pediatric donors, we noticed a considerable amount of early hematogones (eHGs) within the stem cell gate in flow cytometry. Since the number of hematogones causes a decrease in the total number of stem cells counted within the graft, we planned a retrospective study to analyze the effect of eHGs on transplant outcomes. We also wanted to show how allografts containing high amounts of early HGs affect transplant outcomes. Quantification of CD34 numbers and the number of eHGs were determined by flow cytometry. Patients were divided into 2 groups according to the number of CD 34+ cells calculated after subtracting the number of hematogones within the allograft. Those who received < 2 × 106/kg CD34+ cells and ≥ 2 × 106/kg were defined as group 1 and 2, respectively. Twenty-six patients and their 26 donors were included in the study. The median age of patients was 6.5 years and 5.4 years in Group 1 and 2, respectively. The median donor age was 9 years in Group 1 and 7 years in Group 2. The ages and genders were similar in the two groups (p > 0.05). The number of nucleated cells given to both groups was not different. The number of early hematogones given to both groups was similar (p = 0.93). The mean times to myeloid and platelet engraftments were also similar in the two groups. In this study, we provided trilineage engraftment to all patients in two groups. We could not find a considerable effect of these eHGs in myeloid and platelet engraftments. However, the number of patients included in our study is low, therefore we suggest a study including a large number of donors in order to confirm our findings.

Influence of graft composition in patients with hematological malignancies undergoing ATG-based haploidentical stem cell transplantation

To determine the influence of graft composition in haplo-HSCT, we summarized the long-term consequences of 251 consecutive transplantations from haploidentical donors. For donor-recipient HLA3/6-matched setting, 125 cases used G-CSF-mobilized BM and PBSCs mixtures, while 126 cases only used G-CSF-mobilized PBSCs in HLA4/6-matched transplantation. On the one hand, we wanted to explore the effect of harvests (CD34+ cells and TNCs dosages) on transplantation outcome in the context of haplo-HSCT no matter HLA4/6 or HLA3/6-matched setting. On the other hand, for patients using G-CSF-mobilized BM and PBSCs combination in HLA3/6-matched setting, we attempted to analyze whether TNCs or CD34+ cells from G-CSF-mobilized BM or G-CSF-mobilized PBSCs play the most paramount role on transplantation prognosis. Collectively, patients with hematologic malignancies receiving G-CSF-primed BM and PBSCs harvests had comparable consequences with patients only receiving G-CSF-mobilized PBSCs. Moreover, when divided all patients averagely according to the total amount of transfused nucleated cells, 3-year TRM of the intermediate group (13.06-18.05×10⁸/kg) was only 4.9%, which was remarkably reduced when compared to lower and higher groups with corresponding values 18.3%, 19.6% (P=0.026). The 3-year probabilities of OS and DFS of this intermediate group were 72.6% and 66.5%, which were slightly improved than the lower and higher groups. Most importantly, these data suggest that the transfused nucleated cells from G-CSF-primed BM above than 5.20×10⁸/kg could achieve remarkably lower TRM in haplo-HSCT receiving G-CSF-mobilized BM and PBSCs harvests. These encouraging results suggested that we could improve the efficacy of haplo-HSCT by adjusting the component and relative ratio of transfused graft cells. Nevertheless, the above findings should be confirmed in a randomized prospective comparative research with adequate follow-up.

Costs of matched-sibling, unrelated, and haploidentical hematopoietic cell transplantation and risk factors for greater financial burden - a Brazilian FACT-accredited single-center analysis

The complexity and costs of hematopoietic cell transplantation (HCT) have increased over the last decades with the popularization of unrelated donor (URD) transplantation and the introduction of haploidentical transplantation with posttransplant cyclophosphamide. Few studies have addressed this issue. The objective of this study was to analyze HCT costs in a single FACT-accredited private non-profit hospital. We included 79 patients who underwent HCT between 2018 and 2020. We have included all costs from admission day until D + 180. We used a lognormal regression. Median age was 53 y/o and most donors were unrelated (51%). Costs were higher with haploidentical donor (42%, p = 0.017, compared with URD), higher HCT-CI (15% for each point, p = 0.0056), and in patients with liver or gastrointestinal GVHD (45%, p = 0.033), and lower in patients who received CD34 > 2.5 × 10E6/kg (42%, p = 0.0038). We built a score based on the following risk factors: HCT-CI > 3, CD34 ≤ 2.5 × 10E6/kg, haploidentical donor, and donor age > 30 y/o. Patients with 2 + risk factors (N = 53) had a median cost of USD 226,156.00, compared with USD 93,048.00 in patients with zero or 1 point (N = 26, p < 0.0001). In summary, we have shown that HCT costs are higher with lower doses of CD34 cells, haploidentical HCT (provided that the costs of stem cell procurement and ATG are not included), and in patients with higher HCT-CI. Prospective and refined cost analyses comparing haploidentical and URD transplants, as well as effective strategies for patients with higher HCT-CI scores, are warranted. We found no difference in costs between URD and MSD transplantation.

Development and clinical translation considerations for the next wave of gene modified hematopoietic stem and progenitor cells therapies

INTRODUCTION

Consistent and reliable manufacture of gene modified hematopoietic stem and progenitor cell (HPSC) therapies will be of the utmost importance as they become more mainstream and address larger populations. Robust development campaigns will be needed to ensure that these products will be delivered to patients with the highest quality standards.

AREAS COVERED

Through publicly available manuscripts, press releases, and news articles - this review touches on aspects related to HSPC therapy, development, and manufacturing.

EXPERT OPINION

Recent advances in genome modification technology coupled with the longstanding clinical success of HSPCs warrants great optimism for the next generation of engineered HSPC-based therapies. Treatments for some diseases that have thus far been intractable now appear within reach. Reproducible manufacturing will be of critical importance in delivering these therapies but will be challenging due to the need for bespoke materials and methods in combination with the lack of off-the-shelf solutions. Continued progress in the field will manifest in the form of industrialization which currently requires attention and resources directed toward the custom reagents, a focus on closed and automated processes, and safer and more precise genome modification technologies that will enable broader, faster, and safer access to these life-changing therapies.

Low hematocrit reduces the efficiency of CD34+ cell collection when using the Spectra Optia continuous mononuclear cell collection procedure

BACKGROUND

CD34⁺ cell collection efficiency (CE) is the determining factor when calculating processed blood volume (PBV) for leukapheresis (LP). However, the factors affecting CE in the continuous mononuclear cell collection (cMNC) protocol performed by the Spectra Optia apheresis system are not well established.

STUDY DESIGN AND METHODS

We retrospectively collected the data from 147 consecutive apheresis procedures across 106 healthy donors and 27 patients completed between July 2016 and December 2020 at the Okayama University Hospital. All procedures were performed using the Optia cMNC protocol.

RESULTS

The median CD34⁺ CE2 was significantly higher in the donor samples (64.3%) than in the patient samples (46.8%) (p < .0001). WBC counts, hematocrit, and platelet counts were all significantly higher in the donors than in the patients, and there was a moderate positive correlation between CD34⁺ CE2 and hematocrit (r = .47, p < .0001), with the equation of the line being y = 1.23x + 12.23. In contrast, there was only a very weak correlation between CD34⁺ CE2 and WBC or platelet count. In addition, low hematocrit correlated with an increased time to interface formation.

CONCLUSION

These data revealed the negative impact of low hematocrit on the efficiency of CD34⁺ cell collection when using the Optia cMNC protocol and suggest that hematocrit values should also be considered when determining PBV.

Post-hematopoietic stem cell transplantation relapse: Role of checkpoint inhibitors

Background and Aims

Despite the revolutionary effects of hematopoietic stem cell transplantation (HSCT) in treating hematological malignancies, post-HSCT relapse is considered a critical concern of clinicians. Residual malignant cells employ many mechanisms to evade immune surveillance and survive to cause relapse after transplantation. One of the immune-frustrating mechanisms through which malignant cells can compromise the antitumor effects is misusing the self-limiting system of immune response by overexpressing inhibitory molecules to interact with the immune cells, leading them to so-called "exhausted" and ineffective. Introduction of these molecules, known as immune checkpoints, and blocking them was a prodigious step to decrease the relapses.

Methods

Using keywords nivolumab, pembrolizumab, and ipilimumab, we investigated the literature to figure out the role of the immune checkpoints in the HSCT setting. Studies in which these agents were administrated for relapse after transplantation were reviewed. Factors such as the interval from the transplant to relapse, previous treatment history, adverse events, and the patients' outcome were extracted.

Results

Here we provided a mini-review discussing the experiences of three immune checkpoints, including nivolumab, pembrolizumab, and ipilimumab, as well as the pros and cons of using their blockers in relapse control after HSCT. In conclusion, it seems that CI therapy seems effective for this population. Future investigations may provide detailed outlook of this curative options.

Cholinergic signals preserve haematopoietic stem cell quiescence during regenerative haematopoiesis

The sympathetic nervous system has been evolutionary selected to respond to stress and activates haematopoietic stem cells via noradrenergic signals. However, the pathways preserving haematopoietic stem cell quiescence and maintenance under proliferative stress remain largely unknown. Here we found that cholinergic signals preserve haematopoietic stem cell quiescence in bone-associated (endosteal) bone marrow niches. Bone marrow cholinergic neural signals increase during stress haematopoiesis and are amplified through cholinergic osteoprogenitors. Lack of cholinergic innervation impairs balanced responses to chemotherapy or irradiation and reduces haematopoietic stem cell quiescence and self-renewal. Cholinergic signals activate α7 nicotinic receptor in bone marrow mesenchymal stromal cells leading to increased CXCL12 expression and haematopoietic stem cell quiescence. Consequently, nicotine exposure increases endosteal haematopoietic stem cell quiescence in vivo and impairs hematopoietic regeneration after haematopoietic stem cell transplantation in mice. In humans, smoking history is associated with delayed normalisation of platelet counts after allogeneic haematopoietic stem cell transplantation. These results suggest that cholinergic signals preserve stem cell quiescence under proliferative stress.

Development of a novel and synthetic HematoMiR technology that broadly modulates quiescence of stem cells and enhances HSC expansion

Hematopoietic stem cell (HSCs) transplantation is the primary therapeutic modality used to treat hematopoietic disorders. It centers on the capability of a small quantity of HSCs to repopulate whole blood lineages. Along with limited availability of suitable donors, the need for sufficient number of donor HSCs is still challenging in clinical relevance. This has been addressed by ex vivo HSC expansion albeit with partial success, and thus development of an alternative strategy that could improve HSC expansion is required. To that end, we aimed to build HematoMiR, an oligo-based technology that broadly targets HSC quiescence factors. Here, we show that HematoMiRs and their combinations targeting over 50 factors involved in HSC quiescence could induce robust ex vivo murine and human HSC expansion. In particular, HematoMiR-5 treatment enhanced cell cycle through down-regulation of negative cell cycle regulators in HSCs. HematoMiR-5 treated HSPCs had reduced DNA damage during the course of ex vivo expansion. Moreover, HematoMiR-5 treatment led to sustained HSC self-renewal ability and a low apoptosis rate. In addition, HematoMiR-5 expanded HSCs demonstrated successful engraftment and repopulation capacity in the recipient animals. Furthermore, combinatorial treatments of HematoMiR-2 and 5 allowed vigorous ex vivo HSC expansion. These findings demonstrate that novel and synthetic HematoMiR technology is feasible for HSC ex vivo expansion through the sequence-dependent modulation of numerous HSC quiescence modulators.

Impact of donor-derived CD34 + infused cell dose on outcomes of patients undergoing allo-HCT following reduced intensity regimen for myelofibrosis: a study from the Chronic Malignancies Working Party of the EBMT

The optimal CD34 + cell dose in the setting of RIC allo-HCT for myelofibrosis (MF) remains unknown. We retrospectively analyzed 657 patients with primary or secondary MF transplanted with use of peripheral blood (PB) stem cells after fludarabine/melphalan or fludarabine/busulfan RIC regimen. Median patient age was 58 (range, 22-76) years. Donors were HLA-identical sibling (MSD) or unrelated (UD). Median follow-up was 46 (2-194) months. Patients transplanted with higher doses of CD34 + cells (>7.0 × 10⁶/kg), had an increased chance of achievement of both neutrophil (hazard ratio (HR), 1.46; P < 0.001) and platelet engraftment (HR, 1.43; P < 0.001). In a model with interaction, for patients transplanted from a MSD, higher CD34 + dose was associated with improved overall survival (HR, 0.63; P = 0.04) and relapse-free survival (HR, 0.61; P = 0.02), lower risk of non-relapse mortality (HR, 0.57; P = 0.04) and higher rate of platelet engraftment. The combined effect of higher cell dose and UD was apparent only for higher neutrophil and platelet recovery rate. We did not document any detrimental effect of high CD34 + dose on transplant outcomes. More bulky splenomegaly was an adverse factor for survival, engraftment and NRM. Our analysis suggests a potential benefit for MF patients undergoing RIC PB-allo-HCT receiving more than 7.0 × 10⁶/kg CD34 + cells.

Association of CD34 Cell Dose with 5-Year Overall Survival after Peripheral Blood Allogeneic Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Higher CD34 cell dose is associated with improved engraftment after peripheral blood allogeneic hematopoietic stem cell transplantation (alloHCT) but also may increase the risk of long-term complications, such as graft-versus-host disease (GVHD). Prior studies examining the relationship between CD34 cell dose and long-term survival outcomes have yielded conflicting results. In this study, we sought to clarify the prognostic impact of CD34 cell dose by examining a large contemporary cohort of patients undergoing alloHCT with a matched sibling peripheral blood stem cell (PBSC) donor. We retrospectively examined the impact of CD34 cell dose on overall survival (OS), neutrophil engraftment, platelet engraftment, treatment-related mortality, relapse, acute GVHD grade II-IV and III-IV, and chronic GVHD in 377 consecutive patients undergoing alloHCT with a PBSC graft source from a matched sibling donor at the University of Minnesota between 2002 and 2015. The patients were classified into 3 groups based on the tertile (T) of CD34 cell dose received: T1, <5 × 10⁶ cells/kg; T2, 5 to 7.5 × 10⁶ cells/kg; and T3, ≥7.5 × 10⁶ cells/kg. Multivariable analysis demonstrated that high CD34 cell dose was associated with superior 5-year OS (hazard ratio [HR], 0.57; P = .01) and more rapid platelet engraftment (HR, 1.70; P < .01). Higher CD34 cell dose also was associated with improved absolute neutrophil count engraftment (T2: HR, 1.54; T3: HR, 1.52; P < .01). There was no association between CD34 cell dose and TRM or relapse at 5 years. Although higher CD34 cell dose was not associated with acute GVHD grade II-IV, it was associated with chronic GVHD (T2: HR, 1.68; T3: HR, 1.50; P = .04). Our data indicate that higher CD34 cell dose (>7.5 × 10⁶/kg) is associated with superior OS at 5 years and improved engraftment but carries an increased risk of chronic GVHD. These data support a target CD34 cell dose goal of 7.5 × 10⁶/kg for sibling PBSC graft donors.

R4 RGS proteins suppress engraftment of human hematopoietic stem/progenitor cells by modulating SDF-1/CXCR4 signaling

Specific R4 RGS members are expressed in human HSPCs and regulated by the SDF-1/CXCR4 axis.

RGS1/13/16 suppress HSPC engraftment, SDF-1 signaling, and key effectors of stem cell trafficking/maintenance.

Homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) into the bone marrow (BM) microenvironment are tightly regulated by the chemokine stromal cell–derived factor-1 (SDF-1) and its G-protein–coupled receptor C-X-C motif chemokine receptor 4 (CXCR4), which on engagement with G-protein subunits, trigger downstream migratory signals. Regulators of G-protein signaling (RGS) are GTPase-accelerating protein of the Gα subunit and R4 subfamily members have been implicated in SDF-1–directed trafficking of mature hematopoietic cells, yet their expression and influence on HSPCs remain mostly unknown. Here, we demonstrated that human CD34⁺ cells expressed multiple R4 RGS genes, of which RGS1, RGS2, RGS13, and RGS16 were significantly upregulated by SDF-1 in a CXCR4-dependent fashion. Forced overexpression of RGS1, RGS13, or RGS16 in CD34⁺ cells not only inhibited SDF-1–directed migration, calcium mobilization, and phosphorylation of AKT, ERK, and STAT3 in vitro, but also markedly reduced BM engraftment in transplanted NOD/SCID mice. Genome-wide microarray analysis of RGS-overexpressing CD34⁺ cells detected downregulation of multiple effectors with established roles in stem cell trafficking/maintenance. Convincingly, gain-of-function of selected effectors or ex vivo priming with their ligands significantly enhanced HSPC engraftment. We also constructed an evidence-based network illustrating the overlapping mechanisms of RGS1, RGS13, and RGS16 downstream of SDF-1/CXCR4 and Gα_i. This model shows that these RGS members mediate compromised kinase signaling and negative regulation of stem cell functions, complement activation, proteolysis, and cell migration. Collectively, this study uncovers an essential inhibitory role of specific R4 RGS proteins in stem cell engraftment, which could potentially be exploited to develop improved clinical HSPC transplantation protocols.

Optimizing selection of double cord blood units for transplantation of adult patients with malignant diseases

Double-unit unrelated cord blood transplantation (DUCBT) is an option in patients for whom a single unit is not sufficient to provide an adequate number of cells. As current guidelines on UCB unit selection are mainly based on single-unit UCB data, we performed a retrospective analysis of 1375 adult recipients of DUCBT for hematologic malignancies to determine optimal criteria for graft selection. Cryopreserved total nucleated cells (TNCs; ≤3.5 vs >3.5 × 107/kg: hazard ratio [HR], 1.53; 30% vs 45%; P = .01), number of HLA mismatches (≥2 vs 0-1: HR, 1.28; 42% vs 48%; P = .01), and ABO compatibility (minor/major ABO incompatibility vs compatibility: HR, 1.28; P = .04) were independent risk factors for OS. Cryopreserved CD34+ cell dose ≥0.7 × 105/kg in the winning UCB was associated with improved OS (HR, 1.34; P = .03). Low TNC (≤3.5 × 107/kg) and CD34+ (≤1.4 × 105/kg) cell doses were related to decreased neutrophil recovery (HR, 0.65 [P = .01] and HR, 0.81 [P = .01], respectively). DUCBT recipients with ≥2 HLA mismatches had a higher incidence of grade II-IV and III-IV acute graft-versus-host disease (HR, 1.26 [P = .03] and 1.59 [P = .02], respectively). Low TNC dose (HR, 1.57; P = .02) and receiving UCB with ≥2 HLA mismatches (HR, 1.35; P = .03) were associated with increased transplant-related mortality. Our data support selecting adequately HLA-matched UCB units with a double-unit cryopreserved TNC dose >3.5 × 107/kg and CD34+ cell dose of ≥0.7 × 105/kg per unit in DUCBT candidates.

The apheresis content analysis in Allo-HSCT represents reliable influential factors on graft-versus-host disease and overall survival

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is an established treatment for hematologic malignancies. However the post-HSCT outcome can be affected by multiple pre-transplant, transplant, and post-transplant factors. The cellular content of graft could be possible factors influencing the graft-versus-host disease (GVHD) and overall survival (OS) as transplantation outcomes.

PURPOSE

The aim of this study was to assess the impact of infused CD34+ cells, CD3+ cells, and MNC count on the patients' survival and incidence of graft-versus-host disease (GVHD).

MATERIAL AND METHODS

We analyzed 87 patients with hematological malignancies who underwent allogeneic hematopoietic stem cell transplantation at the Taleghani Stem Cell Transplantation and Cell therapy center, Tehran, Iran from January 2016 to December 2018. Patients were conditioned with either myeloablative conditioning regimen or reduced-intensity regimen.

RESULT

A CD34⁺ cell dose < 4.35 × 10⁶/kg and CD3⁺ cell dose < 365 × 10⁶/kg was associated with higher survival and lower acute and chronic GVHD incidence, although their association was not statistically significant. Moreover, there was a significant association between MNC count < 6.15 × 10⁸/kg and acute GVHD incidence.

CONCLUSION

Graft cell dose, lower than the cut-off level, could lead to better outcomes after allogeneic transplantation. However, this study showed that future investigations are required in a larger population of patients in order to determine the exact effect of allogeneic graft cell dose on transplantation outcome.

Immune Reconstitution after Haploidentical Donor and Umbilical Cord Blood Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (HCT) is the only potentially curative therapy for a variety of hematologic diseases. However, this therapeutic platform is limited by an initial period when patients are profoundly immunocompromised. There is gradual immune recovery over time, that varies by transplant platform. Here, we review immune reconstitution after allogeneic HCT with a specific focus on two alternative donor platforms that have dramatically improved access to allogeneic HCT for patients who lack an HLA-matched related or unrelated donor: haploidentical and umbilical cord blood HCT. Despite challenges, interventions are available to mitigate the risks during the immunocompromised period including antimicrobial prophylaxis, modified immune suppression strategies, graft manipulation, and emerging adoptive cell therapies. Such interventions can improve the potential for long-term overall survival after allogeneic HCT.

Risk factors and outcomes of diffuse alveolar haemorrhage after allogeneic haematopoietic stem cell transplantation

Diffuse alveolar haemorrhage (DAH) is a life-threatening pulmonary complication occurring after allogeneic haematopoietic stem cell transplantation (allo-HSCT) without an explicit aetiology or a standard treatment. This study aimed to explore the occurrence and prognosis of DAH after allo-HSCT, in addition to comparing discrepancies in the incidence, clinical characteristics and outcomes of DAH between patients undergoing haploidentical HSCT (HID-HSCT) and matched related donor HSCT (MRD-HSCT). We retrospectively evaluated 92 consecutive patients among 3987 patients with a confirmed diagnosis of DAH following allo-HSCT (HID: 71 patients, MRD: 21 patients). The incidence of DAH after allo-HSCT was 2.3%, 2.4% after HID-HSCT and 2.0% after MRD-HSCT (P = 0.501). The prognosis of patients with DAH after transplantation is extremely poor. The duration of DAH was 7.5 days (range, 1-48 days). The probabilities of overall survival (OS) were significantly different between patients with and without DAH within 2 years after transplantation (P < 0.001). According to the Cox regression analysis, a significant independent risk factor for the occurrence of DAH was delayed platelet engraftment (P < 0.001), and a high D-dimer level (>500 ng/ml) was a significant risk factor for the poor prognosis of DAH. HID-HSCT is similar to MRD-HSCT in terms of the outcomes of DAH.

CD34+ cell dose effects on clinical outcomes after T-cell replete haploidentical allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia using peripheral blood stem cells. A study from the acute leukemia working Party of the European Society for blood and marrow transplantation (EBMT)

Previous observations have reported controversial conclusions regarding cell dose and survival endpoints after allogeneic hematopoietic stem cell transplantation (HSCT). We conducted a retrospective analysis on 414 adult patients (median age 54 years, range, 18-74 years) with acute myeloid leukemia (AML) in first and second complete remission. They received a T-cell replete allogeneic HSCT from haploidentical donors, using peripheral blood stem cells, between 2006-2018. Median number of infused CD34+ was 6.58 × 10⁶ /kg (range, 2.2-31.2 × 10⁶ /kg). Graft-vs-host disease (GVHD) prophylaxis was post-transplant cyclophosphamide in 293 patients and anti-lymphocyte serum in 121 patients. Conditioning was myeloablative in 179 patients and reduced-intensity in 235 patients. After a median follow-up of 23.3 months (range, 12.1-41.8 months), 2-year overall survival (OS) was 64.5% (95% CI 59.3%-69.7%) with leukemia-free survival (LFS) of 57.3% (95% CI 51.8%-62.7%) and non-relapse mortality (NRM) of 23.3% (95% CI 19%-27.7%). Grades III-IV acute GVHD day+100 incidence was 14.6% while extensive chronic GVHD was 14.4% at 2-years. Thirteen (3.2%) patients experienced graft failure. We found the optimal CD34+/kg threshold defining high (n = 334) vs low cell dose (n = 80) at 4.96 × 10⁶ . Recipients of >4.96 × 10⁶ /kg CD34+ cells experienced less NRM (Hazard ratio [HR] 0.48; 95% CI 0.30-0.76) and prolonged LFS (HR 0.63; 95% CI 0.43-0.91) and OS (HR 0.60; 95% CI 0.40-0.88) compared to those in the lower cell dose cohort. Larger cohort studies are needed to confirm these findings.

A sticky wicket: Defining molecular functions for CD34 in hematopoietic cells

The CD34 cell surface antigen is widely expressed in tissues on cells with progenitor-like properties and on mature vascular endothelia. In adult human bone marrow, CD34 marks hematopoietic stem and progenitor cells (HSPCs) starting from the bulk of hematopoietic stem cells with long-term repopulating potential (LT-HSCs) throughout expansion and differentiation of oligopotent and unipotent progenitors. CD34 protein surface expression is typically lost as cells mature into terminal effectors. Because of this expression pattern of HSPCs, CD34 has had a central role in the evaluation or selection of donor graft tissue in HSC transplant (HSCT). Given its clinical importance, it is surprising that the biological functions of CD34 are still poorly understood. This enigma is due, in part, to CD34's context-specific role as both a pro-adhesive and anti-adhesive molecule and its potential functional redundancy with other sialomucins. Moreover, there are also critical differences in the regulation of CD34 expression on HSPCs in humans and experimental mice. In this review, we highlight some of the more well-defined functions of CD34 in HSPCs with a focus on proposed functions most relevant to HSCT biology.

The CD34+ Cell Dose Matters in Hematopoietic Stem Cell Transplantation with Peripheral Blood Stem Cells from Sibling Donors

The effect of CD34⁺ cell dose in allogeneic hematopoietic stem cell transplantation (HSCT) on overall survival (OS) and incidence of acute and chronic graft-versus-host disease (GvHD) has not been established and few studies have been performed. Our single center analysis included 189 patients with hematological malignancies who received peripheral blood stem cell (PBSC) grafts from sibling donors. Myeloablative conditioning was used in 88 cases and 101 received reduced intensity conditioning. The median CD34⁺ cell dose was 5.6 × 10⁶/kg (0.6–17.0). In the multivariate analysis, a CD34 cell dose of 6–7 × 10⁶/kg was associated with better OS and lower transplant-related mortality (TRM), while a dose of <5 × 10⁶/kg led to increased relapse and reduced chronic GVHD (cGVHD). A high CD34 cell-dose (>6.5 × 10⁶/kg) correlated with less acute GVHD (aGVHD) II–IV. We conclude that the CD34 cell dose has an impact on the outcome of HSCT from sibling donor PBSCs.

Bone marrow haploidentical transplant with post-transplantation cyclophosphamide: does graft cell content have an impact on main clinical outcomes?

We analyzed data relative to cell content in 88 consecutive patients receiving HLA haploidentical bone marrow (BM) transplants with post-transplantation cyclophosphamide (PT-CY). Median age was 54.5 (range, 17-72); diagnoses were acute leukemia (n = 46), lymphoproliferative disorders (n = 24), myelofibrosis (n = 11) and myelodysplastic syndromes (n = 5). Total nucleated cell (TNC) and CD34+, CD3+, CD4+ and CD8+ cell doses were stratified as higher than first, second and third quartile and the dose effect on various clinical outcomes was assessed. Median time to engraftment was 17 days for neutrophils and 24 days for platelets. To receive a dose of TNC ≥3.2 x 10⁶/kg or CD34+ cells ≥2.7 x 10⁶/kg significantly shortened the time to neutrophil and platelet engraftment and reduced the blood product requirements in the 30-day period after transplantation. Overall, TNC and CD34+ cell doses had no effect on acute graft-versus-host disease (GVHD) incidence, whereas patients receiving higher CD3+ and CD8+ cell doses seemed to have less chronic GVHD. No effect on non-relapse mortality, progression-free survival and overall survival was observed at different cell dose thresholds. These data suggest that in HLA haploidentical BM transplant with PT-CY, appropriate cell doses are relevant to the engraftment. The association between low CD3+/CD8+ cells and chronic GVHD deserves further investigation.

A high CD34+ cell dose is associated with better disease-free survival in patients with low-risk diseases undergoing peripheral blood stem cell transplantation from HLA-matched related donors

To elucidate the impact of infused CD34⁺ cell doses on transplant outcome, we retrospectively analyzed 851 adult patients who received peripheral blood stem cell transplantation (PBSCT) from human leukocyte antigen (HLA)-matched related donors. The patients were divided into high- and low-CD34 groups at the cutoff value of 4.5 × 10⁶/kg. Overall, the high CD34 group showed early neutrophil and platelet recovery. Stratification of disease risks demonstrated that among the patients with low-risk diseases, the high-CD34 group showed better disease-free survival (DFS) (64.9% vs. 55.5%, P = 0.0415) than did the low-CD34 group, without any increase in graft-versus-host disease (GVHD). Meanwhile, a higher CD34⁺ cell dose had no impacts on the outcomes of patients with high-risk diseases. Multivariate analyses for the patients with low-risk diseases revealed that a high CD34⁺ cell dose (hazard ratio [HR] 0.72, P = 0.048) and development of grade III-to-IV acute GVHD (HR 1.64, P = 0.018) were significantly associated with DFS. An excessive dose of CD34⁺ cells (>8.0 × 10⁶/kg) led to an increase in acute GVHD. By stratification of disease risk, a CD34⁺ cell dose between 4.5 and 8.0 × 10⁶/kg can be suggested for patients with low-risk diseases who undergo PBSCT from HLA-matched related donors.

Impact of CD34+ cell dose on reduced intensity conditioning regimen haploidentical hematopoietic stem cell transplantation

OBJECTIVES

Haploidentical hematopoietic stem cell transplant (haplo-SCT) has been associated with higher rates of graft rejection, and a higher dose of CD34+ cell dose is frequently requested. We aim to explore the impact of CD34+ cell dose in peripheral blood stem cell (PBSC) grafts using reduced intensity conditioning (RIC) in haplo-SCT.

METHODS

Sixty-eight consecutive haplo-SCT in adult patients were included. Graft-vs-host disease (GVHD) prophylaxis consisted on ATG, PTCy, and CsA. The cohort was divided in two groups using CD34+ dose of ≥ 9 × 10⁶ CD34+/Kg as cutoff point. Median follow-up was 8.9 months.

RESULTS

Median cell dose infused was 9.32 × 10⁶ CD34+/Kg. Forty (58.8%) recipients received grafts with CD34+ cells ≥9 × 10⁶ /kg. The infusion ≥ 9 × 10⁶ CD34+/Kg cell dose had a negative impact in overall survival (P = .03) after adjusting for age at transplant. The cumulative incidence of acute GVHD and graft failure were not significantly influenced per CD34+ cell dose. Only four recipients had grade III aGVHD, and all of them received grafts with a CD34+ cell dose ≥ 9 × 10⁶ .

CONCLUSION

In RIC haplo-SCT, recipients may not benefit from PBSC grafts with a CD34+/kg cell dose higher than 9 × 10⁶ cells/kg, as it can have an adverse impact in post-transplant outcome.

Risk Factors for Transplant Outcomes in Children and Adolescents with Non-Malignant Diseases Following Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND The objective of this study was the analysis of transplant outcomes and survival in children treated with allogeneic hematopoietic cell transplantation (alloHCT) for non-malignant disorders, with a focus on risk factor analysis of transplant-related mortality (TRM). MATERIAL AND METHODS The treatment outcome was analyzed retrospectively in 10 consecutive years in 4 pediatric transplant centers in Poland. To compare the outcomes, patient data were analyzed according to the diagnosis, age at transplant, donor type, stem cell source, conditioning regimens, transplanted CD34+ cells dose, and pediatric TRM score. RESULTS From 183 analyzed patients, 27 (14.8%) died, all of them due to transplant-related complications. TRM occurred more frequently in matched unrelated donor (MUD) transplant recipients vs. matched sibling donor (MSD) transplant recipients (p=0.02); in peripheral blood (PB) recipients vs. bone marrow (BM) recipients (p=0.004); and in patients receiving >5×10⁶/kg CD34+ cells (p<0.0001). OS differed significantly according to underlying disease comparing to other diagnoses. Lower survival was found in patients transplanted from MUD (p=0.02). OS was higher in patients receiving BM (p=0.001) and in those receiving ≤5×10⁶/kg CD34+ cells (p<0.001). Multivariate analysis showed lower probability of TRM in BM recipients (p=0.04). The probability of TRM was higher in SCID patients (p=0.02) and in patients receiving >5×10⁶/kg CD34+ cells (p=0.0001). CONCLUSIONS Underlying disease, stem cell source, and CD34+ dose higher than 5×10⁶/kg were the most important risk factors for TRM, and they all affected OS.

Strategies for elevating hematopoietic stem cells expansion and engraftment capacity

Hematopoietic stem cells (HSCs) are a rare cell population in adult bone marrow, mobilized peripheral blood, and umbilical cord blood possessing self-renewal and differentiation capability into a full spectrum of blood cells. Bone marrow HSC transplantation has been considered as an ideal option for certain disorders treatment including hematologic diseases, leukemia, immunodeficiency, bone marrow failure syndrome, genetic defects such as thalassemia, sickle cell anemia, autoimmune disease, and certain solid cancers. Ex vivo proliferation of these cells prior to transplantation has been proposed as a potential solution against limited number of stem cells. In such culture process, MSCs have also been shown to exhibit high capacity for secretion of soluble mediators contributing to the principle biological and therapeutic activities of HSCs. In addition, endothelial cells have been introduced to bridge the blood and sub tissues in the bone marrow, as well as, HSCs regeneration induction and survival. Cell culture in the laboratory environment requires cell growth strict control to protect against contamination, symmetrical cell division and optimal conditions for maximum yield. In this regard, microfluidic systems provide culture and analysis capabilities in micro volume scales. Moreover, two-dimensional cultures cannot fully demonstrate extracellular matrix found in different tissues and organs as an abstract representation of three dimensional cell structure. Microfluidic systems can also strongly describe the effects of physical factors such as temperature and pressure on cell behavior.