Quality and stability studies of red blood cell concentrates from umbilical cord blood compared to their adult counterparts.

BACKGROUND: Prematurity is a significant health issue due to its incidence and associated complications. Anemia is common in extremely preterm infants (EPI) and often requires transfusions. Red blood cells (RBC) from adult blood (AB) donors have been linked to oxygen-related complications in EPI, leading to the exploration of cord blood (CB) as an alternative source. However, standardization of CB-RBC manufacturing and comparison with AB-RBC characteristics are necessary before clinical studies can be conducted. MATERIALS AND METHODS: This study investigated the quality and characteristics of leukoreduced, gamma-irradiated CB-RBC obtained using a commercial closed system from CB donations not meeting hematopoietic transplantation criteria. CB-RBC units were compared with AB-RBC units, both stored in saline-adenine-glucose-mannitol (SAGM). Various parameters, including hematological and biochemical characteristics, pH, 2,3-DPG levels, blood gases and potential toxicants, were evaluated during storage. RESULTS: CB-RBC units had acceptable initial quality parameters and a hematocrit (55±2%) comparable to AB-RBC. The main finding during storage was a faster rise in hemolysis compared to AB-RBC. Potassium (K+) significantly increased during storage in both sources. As expected, glucose levels decreased, and conversely, lactate levels increased, indicating similar patterns of anaerobic glycolysis during storage. pH decreased, affecting the oxygen dissociation curve due to reduced 2,3-DPG levels. After irradiation at 14 days of storage, CB-RBC were less stable as hemolysis and K+ significantly increased compared to AB-RBC at 24 hours. Phthalate concentrations, indicative of plasticizers, increased during storage, but significantly less in CB compared to AB-RBC. Most metals measured were within acceptable ranges. DISCUSSION: The quality of CB-RBC during storage is primarily influenced by levels of hemolysis and extracellular K+ content. Based on the analyzed parameters, we suggest that the expiration date for CB-RBC stored with SAGM should be set at 14 days, with transfusion occurring within <24 hours after irradiation.

Efficiency assessment of cord blood banking and compatibility with delayed cord clamping.

BACKGROUND: There is debate whether delayed umbilical cord clamping following delivery, the current gold standard, affects the proportion of cord blood units (CBU) suitable for public cord blood banking. This study was designed to assess the impact of delayed cord clamping on the number of CBU suitable for therapeutic uses. MATERIALS AND METHODS: To minimize variability, data from the four most active collection centers within the Programa Concordia (Spain) were included. Data on CBU collected in utero from mothers following normal vaginal deliveries from July 2018 to December 2021 were analyzed. The weight of the collection bags (as a surrogate of volume) and total nucleated cell (TNC) count were analyzed according to three defined clamping times: 30 s, 60 s and ≥120 s. The CBU were stratified as suitable for stem cell transplantation (≥110 g and ≥1,500×106 TNC/unit) or other clinical applications (≥100 g but TNC count below the threshold). RESULTS: - There were 131 (18%), 548 (76%), and 40 (5%) CBU collected at 30 s, 60 s and ≥120 s, respectively. The median weight of the CBU decreased gradually with time, with a significant difference between units collected when the cord was clamped at 30 s or 60 s (p=0.036), so significantly fewer CBU met the minimal weight criterion (100 g) at 60 s than at 30 s (p=0.002). However, this was not reflected by the TNC available, resulting in non-statistical differences in CBU eligible for banking between these times. The major predictor of collection success was the neonate's birth-weight. DISCUSSION: -Despite decreases in the volume of cord blood collected when cord clamping at 30 s or 60 s, TNC count is maintained resulting in similar numbers of CBU eligible for banking. The different clamping delays investigated in this study are, therefore, compatible with public cord blood banking needs.

Development of an in-house bone marrow collection kit: The Catalan bone marrow transplantation group experience.

BACKGROUND AND OBJECTIVES: Bone marrow (BM) harvesting is one of the essential sources of stem cells for haematopoietic stem cell transplantation. In 2019, commercial BM collection kits became unavailable in Europe. Consequently, we created an in-house BM collection kit as an alternative. MATERIALS AND METHODS: We compared two groups of BM collections. The first collections were taken using an in-house kit from June 2022 through February 2023 and the second with a commercial kit from February 2021 through May 2022. These all took place at seven collection centres (CC). We analysed the harvest quality (cell blood count, CD34+ cells, viability, potency and sterility), the incidents occurring with each kit and the time to neutrophil and platelet engraftment in recipients. RESULTS: A total of 23 donors underwent BM harvesting with the in-house kit and 23 with the commercial one. Both cohorts were comparable regarding donor characteristics, CC and time to procedure. No statistical differences were found in harvest quality between the in-house and commercial kits. A new transfusion set was required in three BM harvests (13%) with the in-house kit because of filter clogging. The median time to neutrophil and platelet engraftment was 21 days for both cohorts and 29 days (in-house) and 33 days (commercial), p = 0.284, respectively. CONCLUSION: The in-house BM collection kit offers a real approach to solve the diminished supply of commercial kits. A higher risk of filter clogging was observed compared with commercial kits due to the lack of 850 and 500 µm filters.

A hub-and-spoke model to deliver effective access to chimeric antigen receptor T-cell therapy in a public health network: the Catalan Blood and Tissue Bank experience.

BACKGROUND AIMS: To describe and analyze whether a hub-and-spoke organizational model could efficiently provide access to chimeric antigen receptor (CAR) T-cell therapy within a network of academic hospitals and address the growing demands of this complex and specialized activity. METHODS: The authors performed a retrospective evaluation of activity within the Catalan Blood and Tissue Bank network, which was established for hematopoietic stem cell transplantation to serve six CAR T-cell programs in academic hospitals of the Catalan Health Service. Procedures at six hospitals were followed from 2016 to 2021. Collection shipments of starting materials, CAR T-cell returns for storage and infusions for either clinical trials or commercial use were evaluated. RESULTS: A total of 348 leukocytapheresis procedures were performed, 39% of which were delivered fresh and 61% of which were cryopreserved. The network was linked to seven advanced therapy medicinal product manufacturers. After production, 313 CAR T-cell products were shipped back to the central cryogenic medicine warehouse located in the hub. Of the units received, 90% were eventually administered to patients. A total of 281 patients were treated during this period, 45% in clinical trials and the rest with commercially available CAR T-cell therapies. CONCLUSIONS: A hub-and-spoke organizational model based on an existing hematopoietic stem cell transplantation program is efficient in incorporating CAR T-cell therapy into a public health hospital network. Rapid access and support of growing activity enabled 281 patients to receive CAR T cells during the study period.

Leukocytapheresis variables and transit time for allogeneic cryopreserved hpc: better safe than sorry.

Cryopreservation was recommended to ensure continuity in allogeneic hematopoietic progenitor cells (HPC) transplantation during the COVID-19 pandemic. Several groups have shown no impact on clinical outcomes for patients who underwent HPC transplantation with cryopreserved products during the first months of this pandemic. However, concerns about quality control attributes after cryopreservation have been raised. We investigated, in 155 allogeneic peripheral blood cryopreserved HPC, leukocytapheresis characteristics influencing viable CD34+ and CD3+ cells, and CFU-GM recoveries after thawing. Collection characteristics such as volume, nucleated cells (NC)/mL and hematocrit correlated with viable CD34+ and CD3+ cells recoveries after thawing in univariate analysis but only CD3+ cells remained statistically significant in multivariate analysis (r2 = 0.376; P = < 0.001). Additionally, transit time also showed correlation with viable CD34+ (r2 = 0.186), CD3+ (r2 = 0.376) and CFU-GM recoveries (r2 = 0.212) in multivariate analysis. Thus, diluting leukocytapheresis below 200 × 106 NC/mL, avoiding red cells contamination above 2%, cryopreserving below 250 × 106 NC/mL and minimizing transit time below 36 h, prevented poor viable CD34+ and CD3+ cells, and CFU-GM recoveries. In summary, optimizing leukocytapheresis practices and minimizing transportation time may better preserve the quality attributes of HPC when cryopreservation is indicated.

Improved collection of hematopoietic stem cells and progenitors from Fanconi anemia patients for gene therapy purposes.

Difficulties in the collection of hematopoietic stem and progenitor cells (HSPCs) from Fanconi anemia (FA) patients have limited the gene therapy in this disease. We have investigated (ClinicalTrials.gov, NCT02931071) the safety and efficacy of filgrastim and plerixafor for mobilization of HSPCs and collection by leukapheresis in FA patients. Nine of eleven enrolled patients mobilized beyond the threshold level of 5 CD34+ cells/µL required to initiate apheresis. A median of 21.8 CD34+ cells/µL was reached at the peak of mobilization. Significantly, the oldest patients (15 and 16 years old) were the only ones who did not reach that threshold. A median of 4.27 million CD34+ cells/kg was collected in 2 or 3 aphereses. These numbers were markedly decreased to 1.1 million CD34+ cells/kg after immunoselection, probably because of weak expression of the CD34 antigen. However, these numbers were sufficient to facilitate the engraftment of corrected HSPCs in non-conditioned patients. No procedure-associated serious adverse events were observed. Mobilization of CD34+ cells correlated with younger age, higher leukocyte counts and hemoglobin values, lower mean corpuscular volume, and higher proportion of CD34+ cells in bone marrow (BM). All these values offer crucial information for the enrollment of FA patients for gene therapy protocols.

Cryopreservation of unrelated donor hematopoietic stem cells: the right answer for transplantations during the COVID-19 pandemic?

Cryopreservation was recommended to ensure continuity of unrelated donor (UD) hematopoietic stem cell transplantation (HSCT) during COVID-19 pandemic. However, its impact on clinical outcomes and feasibility was not well known. We compared 32 patients who underwent UD HSCT using cryopreserved peripheral blood stem cells (PBSC) during the COVID-19 pandemic with 32 patients who underwent UD HSCT using fresh PBSC in the previous period. Median neutrophil engraftment was 17.5 and 17.0 days with cryopreserved and fresh grafts, respectively. Non-significant delays were found in platelet recovery days (25.5 versus 19.0; P = 0.192) and full donor chimerism days (35.0 and 31.5; P = 0.872) using cryopreserved PBSC. The rate of acute graft-versus-host disease at 100 days was 41% (95% CI [21-55%]) in cryopreserved group versus 31% (95% CI [13-46%]) in fresh group (P = 0.380). One-hundred days progression-relapse free survival and overall survival did not differ significantly. During COVID-19 pandemic, six frozen UD donations were not transfused and logistical and clinical issues regarding cryopreservation procedure, packaging, and transporting appeared. In summary, UD HSCT with cryopreserved PBSC was safe during this challenging time. More efforts are needed to ensure that all frozen grafts are transplanted and cryopreservation requirements are harmonized.

Clinical evaluation of allogeneic eye drops from cord blood platelet lysate.

BACKGROUND: Current treatments for several corneal lesions show limited efficacy. Here we report the clinical evaluation of the efficacy of a novel eye drop preparation produced in a public cord blood (CB) bank. MATERIALS AND METHODS: In a multicentre, retrospective, consecutive case study we evaluated 33 patients (46 eyes) unresponsive to conventional treatments who required urgent intervention. The patients were given allogeneic eye drops obtained from cord blood platelet lysate (CBED) to treat severe ocular surface lesions under a compassionate use protocol. The CBED were prepared from CB units donated for haematopoietic stem cell transplantation that did not contain the minimum stem cell dose required for this use. Patients were grouped by acute conditions (neurotrophic ulcers: group I; other corneal ulcers: group II; corneal burns: group III), and chronic conditions (ocular graft-versus-host disease: group IV; severe dry eye syndrome: group V). The patients received one or two drops of the product to the affected eye four to six times per day for 19 days. A further 19-day cycle of treatment could be repeated according to the initial clinical response. RESULTS: Patients received a median of 19 CBED vials (interquartile range 19-57, range 19-442) to complete the therapy. Group I-II-III patients showed full and partial ulcer recovery in 25 (78%) and six (19%) eyes respectively. One eye (3%) did not respond to treatment. For groups IV-V improvement was reported for 12 (85%) eyes and lesions worsened on treatment in both eyes (15%) of one patient. No severe adverse events were directly attributed to CBED. DISCUSSION: Promptly available CBED resulted in a well-tolerated allogeneic treatment that showed evidence of efficacy in this cohort of patients. These positive results support further studies on CBED from platelet lysate as a novel product of CB banks. A prospective clinical trial in neurotrophic keratitis (NCT03084861) is ongoing to confirm these preliminary data.

Analysis of Cell Subsets in Donor Lymphocyte Infusions from HLA Identical Sibling Donors after Allogeneic Hematopoietic Cell Transplant.

Donor lymphocytes infusions (DLIs) are a major therapeutic approach to treat relapse and mixed chimerism after allogeneic hematopoietic cell transplant (alloHCT). The impact of the composition regarding different cell subsets in the development of graft-versus-host disease (GVHD) is not fully understood. We performed a cell subsets analysis of 56 DLIs from fully HLA-compatible identical matched sibling donors (MSDs) in 36 alloHCT patients and studied its association with GVHD. A median of one DLI was infused per patient. Fourteen patients (38%) developed GVHD. The cell composition analysis of the first DLI (DLI1) showed that a high dose of B cells (P = .03) and CD27+ B cells (P < .01) was associated with GVHD. We identified DLI dose cutoff points for several cell populations above which GVHD was more frequent (CD8+ TN >3 × 106 cells/kg, CD27+ B cells >2.6 × 106/kg, CD27+ NK >0.35 × 106 cells/kg, and mononuclear cells >0.83 × 108/kg). Noteworthy, the proportion of CD4+ naive T cells (TN) or unselected TN was not linked with GVHD and a DLI1 containing a higher dose of regulatory T cells was not protective for GVHD. We studied several transplant clinical variables and did not find any association with GVHD. Altogether, this study provides a comprehensive analysis of the cell populations in a DLI from MSDs and identifies potential key cell subsets, which provides insight for the understanding of GVHD after DLI.

Analysis of relapse after transplantation in acute leukemia: A comparative on second allogeneic hematopoietic cell transplantation and donor lymphocyte infusions.

Relapse of acute leukemia (AL) after allogeneic hematopoietic cell transplantation (Allo-HCT) entails a dismal prognosis. In this scenario, donor lymphocyte infusions (DLIs) and second Allo-HCT are two major approaches. We compared outcomes of AL patients treated for relapse with DLI or second Allo-HCT after receiving debulking therapy. In total, 46 patients were included in the study; 30 (65%) had acute myeloid leukemia and 16 (35%) had acute lymphoblastic leukemia. The median age was 38 years (range 4-66). Twenty-seven patients received a second Allo-HCT and 19 patients received DLI. The median follow-up of the cohort was 273 days (range 9-7013). Overall survival (OS), disease-free survival (DFS), nonrelapse mortality, and cumulative incidence (CI) of relapse were calculated from DLI or second Allo-HCT date. In univariate analysis, second Allo-HCT was associated with higher OS (p = 0.021) and a trend to higher DFS (p = 0.097) and CI of relapse (p = 0.094) on univariate analysis. However, multivariate analysis showed comparable outcomes between DLI and second Allo-HCT, with the time interval to relapse before DLI or second Allo-HCT the only statistically significant factor with an impact on OS and DFS. Within the DLI cohort, T-cell-depleted Allo-HCT was associated with higher OS (p = 0.003) and DFS (p < 0.001) and lower CI of relapse (p = 0.002) than T-cell-replete Allo-HCT. Overall, in this cohort of AL patients, second Allo-HCT and DLI associated similar outcomes. As in other relapse studies, the length of remission (time to relapse) was identified as a factor with statistical impact on survival. Further studies are warranted.

Post-Thaw Viable CD45+ Cells and Clonogenic Efficiency are Associated with Better Engraftment and Outcomes after Single Cord Blood Transplantation in Adult Patients with Malignant Diseases.

The quantity of cells is widely accepted as the main factor influencing the outcome after umbilical cord blood transplantation (UCBT) however, the quality of the cord blood units (CBUs) has been less studied. In order to determine the impact of qualitative variables in UCBT outcomes, we conducted a multicenter retrospective study in adult patients with hematological malignancies who underwent single UCBT after a common myeloablative conditioning regimen. One hundred and ten patients from 3 institutions [median age, 35 years (range 18-55)] were included. Quantitative (TNC and total CD34+cells) and qualitative variables [viable CD45+ (vCD45+), vCD34+ and clonogenic efficiency [(CLONE), quotient of post-thaw colony-forming units (CFU)] and pre-freeze CD34+ cells predicted engraftment in univariate analysis however, only 2 qualitative variables remained significant in the multivariate analysis. Infusion of more than 2 × 10(7) post-thaw vCD45+ cells per kilogram was significantly associated with faster neutrophil (P = .01), platelet engraftment (P = .01), higher disease-free (P = .01) and overall survival (0.02). In addition, CLONE ≥ 20% predicted a faster neutrophil (P = .005), platelet engraftment (P = .01) and contributed to decrease the non-relapse mortality (P = .02). Our study suggests that the vCD45+ cells dose and CLONE are powerful surrogate markers of graft quality and can potentially help on CBUs selection if tested with representative reference samples.

Few and nonsevere adverse infusion events using an automated method for diluting and washing before unrelated single cord blood transplantation.

Graft dilution and DMSO washing before cord blood (CB) administration using an automated system may offer low incidence of adverse infusion events (AIE), ensuring reproducible cell yields. Hence, we analyzed the incidences and significance of immediate AIE, cellular yield, and engraftment after single CB infusion. One hundred and fifty-seven patients (median age, 20 years; range, 1 to 60) received a single CB unit for treatment of hematologic and nonhematologic malignancies with myeloablative conditioning after graft dilution and washing. The median total nucleated cell (TNC) doses was 3.4 × 10(7)/kg (range, 2 to 26) and the median post-thaw recovery was 84% (range, 45 to 178). The cumulative incidence of neutrophil engraftment at 50 days was 84% (95% confidence interval [CI], 83 to 93). A total of 118 immediate AIE were observed in fifty-two (33%) patients. All reported AIE were transient, graded from 1 to 2 by Common Terminology Adverse Events version 4. The most frequent toxicity was cardiovascular but without any life-threatening reaction. Infused TNC, recipient's weight, and rate of infusion per kilogram were risk factors associated with cardiovascular AIE in multivariate analysis (odds ratio [OR], 1.2 (95% CI, 1.1 to 1.4); P < .001; OR, .94 (95% CI, .9 to .97); P < .001; and OR, 1.5 (95% CI, 1.2 to 1.8); P < .001; respectively). In summary, use of an automated method for graft washing before CB administration showed low incidence of AIE without compromising cell yields and engraftment. Infused TNC dose, recipient's weight, and rate of infusion per kilogram were risk factors associated with infusion reactions.

Thawing of cryopreserved hematopoietic progenitor cells from apheresis with a new dry-warming device.

BACKGROUND: Current thawing techniques of cryopreserved progenitor cells are based on the use of a water bath. The aim of this study has been to assess the progenitor cell viability and the time of hematopoietic engraftment after transplantation of cell products thawed with a new dry-thawing device. STUDY DESIGN AND METHODS: In the preclinical phase, two cryobags from the same patient were thawed with the standard technique and with the dry system method in parallel (n=5, Protocol A and Protocol B, respectively). In the clinical phase, cryobags were thawed with the dry system and the time to hematopoietic engraftment after autologous transplantation (n=52) was compared with those of a control group of patients whose progenitor cell products were thawed with the standard technique (n=52). RESULTS: There were no statistical differences in nuclear and CD34+ cell viability, total colony-forming cells, and cloning efficiency after thawing with Protocols A and B. Days to neutrophil (>0.5×10(9) and >1×10(9) /L) and platelet engraftment (>20×10(9) and >50×10(9) /L) were not different between patients transplanted with products thawed with Protocols A and B. CONCLUSION: Progenitor cell viability and function are preserved with this dry-thawing system. The time to hematopoietic engraftment of patients after transplantation is comparable to those infused with progenitor cells thawed with the water bath technique. Thawing cell products without the use of water and in a dry environment might favor the use of this dry method.

Notch signals contribute to preserve the multipotentiality of human CD34(+)CD38(-)CD45RA(-)CD90(+) hematopoietic progenitors by maintaining T cell lineage differentiation potential.

Notch signals are critical for T-cell development, limiting the differentiation potential of multipotent progenitors arriving in the thymus via the bloodstream. Notch ligands Delta-like and Jagged are expressed in the bone marrow and, consequently, a role in the regulation of early events of adult hematopoiesis has been proposed. However, mice with disruptions in the Notch pathway do not show gross defects in the hematopoietic stem cell compartment, limiting Notch effects at later stages of development. In this study, we identify cord blood CD34(+)CD38(-)CD45RA(-)CD90(+) cells, a recently described population of hematopoietic stem cells, as one of the earliest targets of Notch in human hematopoiesis. Upon Notch activation, CD34(+)CD38(-) cells are blocked in their differentiation at the CD34(+)CD38(-)CD45RA(-)CD90(+) stage. Importantly, population and clonal analysis demonstrate that Delta-like-1 exposure does not affect lymphoid vs myeloid decisions. However, Notch signaling is required before lymphoid commitment to preserve T-cell potential of CD34(+)CD38(-)CD45RA(-)CD90(+) cells. Our experiments also show that in terms of differentiation potential, CD34(+)CD38(-)CD45RA(-)CD90(+) cells cultured in the presence of Notch signals, resemble cells directly isolated from cord blood. These results could have implications for translational efforts in the design of strategies aimed to accelerate immune reconstitution after transplantation.

Generation of induced pluripotent stem cells from human cord blood cells with only two factors: Oct4 and Sox2.

Induced pluripotent stem cells (iPSC) provide an invaluable resource for regenerative medicine as they allow the generation of patient-specific progenitors with potential value for cell therapy. However, in many instances, an off-the-shelf approach is desirable, such as for cell therapy of acute conditions or when the patient's somatic cells are altered as a consequence of a chronic disease or aging. Cord blood (CB) stem cells appear ideally suited for this purpose as they are young cells expected to carry minimal somatic mutations and possess the immunological immaturity of newborn cells; additionally, several hundred thousand immunotyped CB units are readily available through a worldwide network of CB banks. Here we present a detailed protocol for the derivation of CB stem cells and how they can be reprogrammed to pluripotency by retroviral transduction with only two factors (OCT4 and SOX2) in 2 weeks and without the need for additional chemical compounds.

Combined intermittent hypoxia and surface muscle electrostimulation as a method to increase peripheral blood progenitor cell concentration.

BACKGROUND: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilize hematopoietic stem cells (HSC) and increase their presence in peripheral circulation. METHODS: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposure consisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. RESULTS: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. CONCLUSION: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.

Cryopreservation of hematopoietic progenitor cells from apheresis at high cell concentrations does not impair the hematopoietic recovery after transplantation.

BACKGROUND: The high number of nuclear cells (NCs) from hematopoietic progenitor cells-apheresis (HPC-A) requires cryopreservation in large volumes or at high NC concentrations. The effect of NC concentration during cryopreservation has yet to be examined. STUDY DESIGN AND METHODS: In the experimental arm (n = 610, Protocol B), the first HPC-A sample from the patient was cryopreserved in two cryobags and subsequent collections in one cryobag, resulting in high NC concentrations (>100 x 10(6) NCs/mL) in most cases. The effect of NC concentrations at freezing in NC recovery after thawing and engraftment kinetics was analyzed and compared with a group of HPC-A cryopreserved at standard NC concentrations (n = 455, Protocol A). RESULTS: The mean (SD) NC concentration at freezing was 78 (28) x 10(6) per mL (median, 82 x 10(6)/mL; range, 12 x 10(6)-156 x 10(6)/mL) and 183 (108) x 10(6) per mL (median, 156 x 10(6)/mL; range, 16 x 10(6)-678 x 10(6)/mL), for HPC-A cryopreserved according to Protocols A and B, respectively. The NC viabilities of the test vials and HPC-A components after thawing were 88 percent versus 85 percent and 85 percent versus 82 percent, and the cloning efficiency was 49 percent versus 33 percent for Protocols A and B, respectively (p < 0.001). Significant differences were not observed in the recovery of NCs. Days to neutrophil and platelet engraftment were not different between patients transplanted in the standard- (n = 143) or high-cell-concentration group (n = 238). CONCLUSION: The cryopreservation of HPC-A at higher than standard NC concentrations has no adverse impact on hematopoietic reconstitution after transplantation.