Real-world clinical characterization, healthcare resource utilization and productivity loss in chronic graft versus host patients exposed to extracorporeal photopheresis in Sweden.

BACKGROUND: Extracorporeal photopheresis (ECP) is frequently used to treat moderate-severe chronic graft versus host disease (cGVHD), however limited data exists describing ECP treatment effects on healthcare and societal costs. We aimed to characterize clinical and health economic outcomes and productivity loss in cGVHD patients exposed to ECP. METHODS: We identified 2708 patients aged ≥ 18 years with a record of allogeneic hematopoietic stem cell transplantation (HSCT) in the Swedish Patient Register between 2006 and 2020. Patients exposed to ECP from 3-months post HSCT (index) were included (n= 183). Data was linked to the Prescribed Drug Register, the Cause of Death Register, and the Longitudinal Integrated Database for Health Insurance and Labor Market Studies (LISA). RESULTS: The median patient age at index was 51 years (IQR1-3; 38-61). In the 3-month period before ECP initiation compared to 9-12 months post-ECP, the cumulative three-month dose per patient decreased prednisolone/prednisone (1,381 mg vs. 658 mg, p < 0.001) and cyclosporin (12,242 mg vs. 3,501 mg, p < 0.001). Infection incidence also decreased over the same period (79.2% vs 59.1%, p < 0.001). Time spent in healthcare decreased from 68.9% to 22.1% from the first and fifth follow-up year respectively, and corresponding annual healthcare cost reduced from €27,719 to €1,981. Among patients < 66 years of age, sickness-related workplace absence decreased from 73.2% to 31.9% between the first and fifth follow-up year, with median annual productivity loss decreasing from €20,358 to €7,211 per patient. CONCLUSIONS: ECP was associated with reduced use of corticosteroids, immunosuppressive agents, and fewer infections. Furthermore, cost and healthcare utilization decreased over time.

Label-free separation of neuroblastoma patient-derived xenograft (PDX) cells from hematopoietic progenitor cell products by acoustophoresis.

BACKGROUND: Graft-contaminating tumor cells correlate with inferior outcome in high-risk neuroblastoma patients undergoing hematopoietic stem cell transplantation and can contribute to relapse. Motivated by the potential therapeutic benefit of tumor cell removal as well as the high prognostic and diagnostic value of isolated circulating tumor cells from stem cell grafts, we established a label-free acoustophoresis-based microfluidic technology for neuroblastoma enrichment and removal from peripheral blood progenitor cell (PBPC) products. METHODS: Neuroblastoma patient-derived xenograft (PDX) cells were spiked into PBPC apheresis samples as a clinically relevant model system. Cells were separated by ultrasound in an acoustophoresis microchip and analyzed for recovery, purity and function using flow cytometry, quantitative real-time PCR and cell culture. RESULTS: PDX cells and PBPCs showed distinct size distributions, which is an important parameter for efficient acoustic separation. Acoustic cell separation did not affect neuroblastoma cell growth. Acoustophoresis allowed to effectively separate PDX cells from spiked PBPC products. When PBPCs were spiked with 10% neuroblastoma cells, recoveries of up to 98% were achieved for PDX cells while more than 90% of CD34+ stem and progenitor cells were retained in the graft. At clinically relevant tumor cell contamination rates (0.1 and 0.01% PDX cells in PBPCs), neuroblastoma cells were depleted by more than 2-log as indicated by RT-PCR analysis of PHOX2B, TH and DDC genes, while > 85% of CD34+ cells could be retained in the graft. CONCLUSION: These results demonstrate the potential use of label-free acoustophoresis for PBPC processing and its potential to develop label-free, non-contact tumor cell enrichment and purging procedures for future clinical use.

Using the World Apheresis Association Registry Helps to Improve the Treatment Quality of Therapeutic Apheresis.

Therapeutic apheresis (TA) is prescribed to patients that suffer from a severe progressive disease that is not sufficiently treated by conventional medications. A way to gain more knowledge about this treatment is usually by the local analysis of data. However, the use of large quality assessment registries enables analyses of even rare findings. Here, we report some of the recent data from the World Apheresis Association (WAA) registry. Data from >104,000 procedures were documented, and TA was performed on >15,000 patients. The main indication for TA was the collection of autologous stem cells (45% of patients) as part of therapy for therapy. Collection of stem cells from donors for allogeneic transplantation was performed in 11% of patients. Patients with indications such as neurological diseases underwent plasma exchange (28%). Extracorporeal photochemotherapy, lipid apheresis, and antibody removal were other indications. Side effects recorded in the registry have decreased significantly over the years, with approximately only 10/10,000 procedures being interrupted for medical reasons. CONCLUSION: Collection of data from TA procedures within a multinational and multicenter concept facilitates the improvement of treatment by enabling the analysis of and feedback on indications, procedures, effects, and side effects.

The combination of clofarabine, etoposide, and cyclophosphamide shows limited efficacy as a bridge to transplant for children with refractory acute leukemia: results of a monitored prospective study.

Clofarabine has been shown to effectively induce remission in children with refractory leukemia. We conducted a prospective trial (clinicval.trials.gov NCT01025778) to explore the use of clofarabine-based chemotherapy as a bridge-to-transplant approach. Children with refractory acute leukemia were enrolled to receive two induction courses of clofarabine, etoposide, and cyclophosphamide (CloEC). Responding patients were scheduled for T-cell depleted haploidentical hematopoietic stem cell transplantation (HSCT). The primary objective was to improve survival by achieving sufficient disease control to enable stem cell transplantation. Secondary objectives were to evaluate safety and toxicity. Seven children with active disease entered the study. Two children responded to induction courses and underwent transplantation. Five children did not respond to induction: one died in progression after the first course; two received off-protocol chemotherapy and were transplanted; and two succumbed to progressive leukemia. All transplanted children engrafted and no acute skin graft-versus-host disease > grade I was observed. One child is alive and well 7.5 years after the first CloEC course. One child developed fulminant adenovirus hepatitis and died in continuous complete remission 7 months after start of induction. Two children relapsed and died 6.5 and 7.5 months after enrollment. Infection was the most common toxicity. CloEC can induce responses in some patients with refractory acute leukemia but is highly immunosuppressive, resulting in substantial risk of life-threatening infections. In our study, haploidentical HSCT was feasible with sustained engraftment. No clinically significant organ toxicity was observed. Also, repeating CloEC probably does not increase the chance of achieving remission.

Low incidence of hemorrhagic cystitis following ex vivo T-cell depleted haploidentical hematopoietic cell transplantation in children.

Hemorrhagic cystitis (HC) is a debilitating complication following allogenic hematopoietic cell transplantation (HCT). HLA disparity and T-cell depletion have been implicated as risk factors for HC. However, reports on the incidence and risk factors for HC in ex vivo T-cell depleted haploidentical HCT (haploHCT) in children are lacking. We studied 96 haploHCT procedures performed in 83 children between 2002 and 2017. Sixty-three patients were diagnosed with a malignant disease and 20 with nonmalignant disease. All but three patients with SCID underwent myelotoxic and/or lymphotoxic conditioning therapy. Grafts were CD3+ (36.5%) or TcRαß+ (63.5%) depleted to prevent graft versus host disease (GvHD). Fourteen patients (14.6%) were diagnosed with HC; 12 (12.5%) had clinically significant stage II-IV HC. All patients with HC had BK viruria and/or viremia. Increasing age and chemotherapeutic treatment prior to conditioning were identified as risk factors for HC. Immune recovery did not significantly differ between patients with and without HC. Thus, we report a low incidence of HC in pediatric haploHCT using ex vivo T-cell depletion. The combination of a reduced toxicity conditioning regimen, and typically absent pharmaceutical post-HCT GvHD prophylaxis in our patients might have contributed to the decreased the risk of HC, despite HLA disparity.

Label-free neuroblastoma cell separation from hematopoietic progenitor cell products using acoustophoresis - towards cell processing of complex biological samples.

Processing of complex cell preparations such as blood and peripheral blood progenitor cell (PBPC) transplants using label-free technologies is challenging. Transplant-contaminating neuroblastoma cells (NBCs) can contribute to relapse, and we therefore aimed to provide proof-of-principle evidence that label-free acoustophoretic separation can be applied for diagnostic NBC enrichment and removal ("purging") from human blood and PBPC products. Neuroblastoma cells spiked into blood and PBPC preparations served as model systems. Acoustophoresis enabled to enrich NBCs from mononuclear peripheral blood cells and PBPC samples with recovery rates of up to 60-97%. When aiming at high purity, NBC purities of up to 90% were realized, however, compromising recovery. Acoustophoretic purging of PBPC products allowed substantial tumour cell depletion of 1.5-2.3 log. PBPC loss under these conditions was considerable (>43%) but could be decreased to less than 10% while still achieving NBC depletion rates of 60-80%. Proliferation of cells was not affected by acoustic separation. These results provide first evidence that NBCs can be acoustically separated from blood and stem cell preparations with high recovery and purity, thus indicating that acoustophoresis is a promising technology for the development of future label-free, non-contact cell processing of complex cell products.

Haploidentical Stem Cell Transplantation for Refractory/Relapsed Neuroblastoma.

Pediatric patients with refractory or relapsed metastatic neuroblastoma (NBL) have a poor prognosis despite autologous stem cell transplantation (SCT). Allogeneic SCT from a haploidentical donor has a remarkable alloreactive effect in patients with leukemia; thus, we evaluated this approach in children with very high-risk NBL. We analyzed data from 2 prospective phase I/II trials. A total of 26 patients with refractory (n = 5), metastatic relapsed (n = 20), or locally relapsed MYCN-positive (n = 1) NBL received a median of 17 × 106/kg T/B cell-depleted CD34+ stem cells with 68 × 103/kg residual T cells and 107 × 106/kg natural killer cells. The conditioning regimen comprised melphalan, fludarabine, thiotepa, OKT3, and a short course of mycophenolate mofetil post-transplantation. Engraftment occurred in 96% of the patients. Event-free survival and overall survival at 5 years were 19% and 23%, respectively. No transplantation-related mortality was observed, and the single death was due to progression/subsequent relapse. The median duration of follow-up was 8.1 years. Patients in complete remission before SCT had a significantly better prognosis than those with residual tumor load (P < .01). All patients with progressive disease before SCT relapsed within 1 year. Grade II and grade III acute graft-versus-host disease (GVHD) occurred in 31% and 12% of the patients, respectively. Chronic limited and extensive GVHD occurred in 28% and 10%, respectively. Our data indicate that haploidentical SCT is a feasible treatment option that can induce long-term remission in some patients with NBL with tolerable side effects, and may enable the development of further post-transplantation therapeutic strategies based on the donor-derived immune system.

Transplantation of Haploidentical TcRaß-Depleted Hematopoietic Cells Allows for Optimal Timing and Sustained Correction of the Metabolic Defect in Children With Infantile Osteopetrosis.

In osteopetrosis, osteoclast dysfunction can lead to deafness, blindness, bone marrow failure, and death. Hematopoietic cell transplantation (HCT) is currently the only curative treatment, but outcome remains disappointing. Although a rapid progression toward HCT is detrimental to prevent further progress of disease manifestations, 70% of cases lack an HLA-matched sibling and require alternative stem cell sources. We present two cases of osteopetrosis that successfully received an HCT with haploidentical TcRαß-depleted cells from one of the parents. These cases showed no further disease progression, had restoration of functional osteoclasts, and illustrate this approach to enable prompt HCT with ready available parental donors and rapid and sustained hematological, including osteoclast, recovery. © 2016 American Society for Bone and Mineral Research.

Novel treatment of severe combined immunodeficiency utilizing ex-vivo T-cell depleted haploidentical hematopoietic stem cell transplantation and CD45RA+ depleted donor lymphocyte infusions.

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment available for severe combined immunodeficiency (SCID); although, there is a high incidence of severe infections and an increased risk of graft-versus host-disease (GvHD) with HSCT. Early intervention is a crucial prognostic factor and a HLA-haploidentical parental donor is often available. Haploidentical HSCT protocols utilizing extensively ex vivo T-cell depleted grafts (CliniMACs system) have proven efficient in preventing GvHD, but cause a delay in early T-cell recovery that increases the risk of viral infections. Here, we present a novel approach for treating SCID that combines selective depletion of GvHD-inducing alpha/beta (α/ß) T-cells from the haploidentical HSCT graft with a subsequent donor lymphocyte infusion (DLI) enriched for CD45RO+ memory T-cells. RESULTS: Our patient was diagnosed with SCID (T-B + NK+ phenotype). At 9 months of age, he received a T cell receptor(TCR)α/ß-cell depleted graft from his haploidentical mother, following a reduced intensity conditioning regimen with no additional GvHD prophylaxis. Engraftment was rapid with complete donor chimerism and no signs of GvHD. However, at 12 weeks post HSCT, the patient was still T-cell lymphopenic with clinical symptoms of multiple severe viral infections. Consequently, therapeutic DLIs were initiated for enhanced anti-viral immunity. The patient was treated with CD45RA+ depleted haploidentical maternal donor lymphocytes enriched from unmobilized whole blood, and a total T-cell dose of no more than 25 x10(3) CD3+ cells/kg with >99.9% purity of CD3 + CD45RO+ memory T-cells was transferred. Following the DLI, a prompt increase in CD3 + CD4+ and CD3 + CD8+ counts was observed with a subsequent clearance of viral infections. No acute or chronic GvHD was observed. CONCLUSIONS: Automated depletion of CD45RA+ naïve T-cells from unmobilized whole blood is a simple and rapid strategy to provide unmanipulated DLIs, with a potentially broad repertoire of pathogen specific memory T-cells. In the haploidentical setting, CD45RA+ depleted DLIs can be safely administered at low T-cell doses for efficient enhancement of viral immunity and limited risk of GvHD. We demonstrate the successful use of this approach following TCR-α/ß-cell depleted HSCT for the treatment of SCID.

Affinity-Bead-Mediated Enrichment of CD8+ Lymphocytes from Peripheral Blood Progenitor Cell Products Using Acoustophoresis.

Acoustophoresis is a technique that applies ultrasonic standing wave forces in a microchannel to sort cells depending on their physical properties in relation to the surrounding media. Cell handling and separation for research and clinical applications aims to efficiently separate specific cell populations. Here, we investigated the sorting of CD8 lymphocytes from peripheral blood progenitor cell (PBPC) products by affinity-bead-mediated acoustophoresis. PBPC samples were obtained from healthy donors (n = 4) and patients (n = 18). Mononuclear cells were labeled with anti-CD8-coated magnetic beads and sorted on an acoustophoretic microfluidic device and by standard magnetic cell sorting as a reference method. CD8 lymphocytes were acoustically sorted with a mean purity of 91% ± 8% and a median separation efficiency of 63% (range 15.1%⁻90.5%) as compared to magnetic sorting (purity 91% ± 14%, recovery 29% (range 5.1%⁻47.3%)). The viability as well as the proliferation capacity of sorted lymphocytes in the target fraction were unimpaired and, furthermore, hematopoietic progenitor cell assay revealed a preserved clonogenic capacity post-sorting. Bead-mediated acoustophoresis can, therefore, be utilized to efficiently sort less frequent CD8+ lymphocytes from PBPC products in a continuous flow mode while maintaining cell viability and functional capacity of both target and non-target fractions.

Efficient purification of CD4+ lymphocytes from peripheral blood progenitor cell products using affinity bead acoustophoresis.

Processing of peripheral blood progenitor cells (PBPC) for clinical transplantation or research applications aims to effectively isolate or deplete specific cell populations, utilizing primarily magnetic or fluorescence activated sorting methods. Here, we investigated the performance of microfluidic acoustophoresis for the separation of lymphocyte subsets from PBPC, and present a novel method for affinity-bead-mediated acoustic separation of cells which can otherwise not be acoustically discriminated. As the acoustic force on a particle depends on particle size, density and compressibility, targeting of cells by affinity specific beads will generate cell-bead complexes that exhibit distinct acoustic properties relative to nontargeted cells and are, thus, possible to isolate. To demonstrate this, PBPC samples (n = 22) were obtained from patients and healthy donors. Following density gradient centrifugation, cells were labeled with anti-CD4-coated magnetic beads (Dynal) and isolated by acoustophoresis and, for comparison, standard magnetic cell sorting technique in parallel. Targeted CD4+ lymphocytes were acoustically isolated with a mean (±SD) purity of 87 ± 12%, compared with 96 ± 3% for control magnetic sorting. Viability of sorted cells was 95 ± 4% (acoustic) and 97 ± 3% (magnetic), respectively. The mean acoustic separation efficiency of CD4+ lymphocytes to the target fraction was 65 ± 22%, compared with a mean CD4+ lymphocyte recovery of 56 ± 15% for magnetic sorting. Functional testing of targeted CD4+ lymphocytes demonstrated unimpaired mitogen-mediated proliferation capacity and cytokine production. Hematopoietic progenitor cell assays revealed a preserved colony forming ability of nontarget cells post sorting. We conclude that the acoustophoresis platform can be utilized to efficiently isolate bead-labeled CD4+ lymphocytes from PBPC samples in a continuous flow format, with preserved functional capacity of both target and nontarget cells. These results open up for simultaneous affinity-bead-mediated separation of multiple cell populations, something which is not possible with current standard magnetic cell separation technology. © 2014 International Society for Advancement of Cytometry.

Efficient removal of platelets from peripheral blood progenitor cell products using a novel micro-chip based acoustophoretic platform.

BACKGROUND: Excessive collection of platelets is an unwanted side effect in current centrifugation-based peripheral blood progenitor cell (PBPC) apheresis. We investigated a novel microchip-based acoustophoresis technique, utilizing ultrasonic standing wave forces for the removal of platelets from PBPC products. By applying an acoustic standing wave field onto a continuously flowing cell suspension in a micro channel, cells can be separated from the surrounding media depending on their physical properties. STUDY DESIGN AND METHODS: PBPC samples were obtained from patients (n = 15) and healthy donors (n = 6) and sorted on an acoustophoresis-chip. The acoustic force was set to separate leukocytes from platelets into a target fraction and a waste fraction, respectively. The PBPC samples, the target and the waste fractions were analysed for cell recovery, purity and functionality. RESULTS: The median separation efficiency of leukocytes to the target fraction was 98% whereas platelets were effectively depleted by 89%. PBPC samples and corresponding target fractions were similar in the percentage of CD34+ hematopoetic progenitor/stem cells as well as leukocyte/lymphocyte subset distributions. Median viability was 98%, 98% and 97% in the PBPC samples, the target and the waste fractions, respectively. Results from hematopoietic progenitor cell assays indicated a preserved colony-forming ability post-sorting. Evaluation of platelet activation by P-selectin (CD62P) expression revealed a significant increase of CD62P+ platelets in the target (19%) and waste fractions (20%), respectively, compared to the PBPC input samples (9%). However, activation was lower when compared to stored blood bank platelet concentrates (48%). CONCLUSION: Acoustophoresis can be utilized to efficiently deplete PBPC samples of platelets, whilst preserving the target stem/progenitor cell and leukocyte cell populations, cell viability and progenitor cell colony-forming ability. Acoustophoresis is, thus, an interesting technology to improve current cell processing methods.

High-dose iodine-131-metaiodobenzylguanidine with haploidentical stem cell transplantation and posttransplant immunotherapy in children with relapsed/refractory neuroblastoma.

We evaluated the feasibility and efficacy of using high-dose iodine-131-metaiodobenzylguanidine ((131)I-MIBG) followed by reduced-intensity conditioning (RIC) and transplantation of T cell-depleted haploidentical peripheral blood stem cells (designated haplo-SCT) to treat relapsing/refractory neuroblastoma (RRNB). Five RRNB patients were enrolled: 4 with relapse (3 after autologous SCT) and 1 with induction therapy failure. The preparative regimen included high-dose (131)I-MIBG on day -20, followed by fludarabine (Flu), thiotepa, and melphalan (Mel) from day -8 to -1. Granulocyte-colony stimulating factor (G-CSF)-mobilized, T cell-depleted haploidentical paternal stem cells were infused on day 0 together with cultured donor mesenchymal stem cells. A single dose of rituximab was given on day +1. After cessation of short immunosuppression (mycophenolate, OKT3), 4 children received donor lymphocyte infusion (DLI). (131)I-MIBG infusion and RIC were well tolerated. All patients engrafted. No primary acute graft-versus-host disease (aGVHD) was observed. Four children developed aGVHD after DLI and were successfully treated. Analysis of immunologic recovery showed fast reappearance of potentially immunocompetent natural killer (NK) and T cells, which might have acted as effector cells responsible for the graft-versus-tumor (GVT) effect. Two children are alive and well, with no evidence of disease 40 and 42 months after transplantation. One patient experienced late progression with new bone lesions (sternum) 38 months after haplo-SCT, and is being treated with local irradiation and reinstituted DLI. One patient rejected the graft, was rescued with autologous backup, and died of progressive disease 5 months after transplantation. Another child relapsed 7 months after transplantation and died 5 months later. High-dose (131)I-MIBG followed by RIC and haplo-SCT for RRNB is feasible and promising, because 2 of 5 children on that regimen achieved long-lasting remission. Further studies are needed to evaluate targeted therapy and immune-mediated tumor control in high-risk neuroblastoma.

Rapid and effective CD3 T-cell depletion with a magnetic cell sorting program to produce peripheral blood progenitor cell products for haploidentical transplantation in children and adults.

BACKGROUND: Effective T-cell depletion is a prerequisite for haploidentical peripheral blood progenitor cell (PBPC) transplantation. This study was performed to investigate the performance of magnetic cell sorting-based direct large-scale T-cell depletion, which is an attractive alternative to standard PBPC enrichment procedures. STUDY DESIGN AND METHODS: PBPCs were harvested from 11 human leukocyte antigen (HLA)-haploidentical donors. T cells labeled with anti-CD3-coated beads were depleted with a commercially available magnetic separation unit (CliniMACS, Miltenyi Biotec) with either the Depletion 2.1 (D2.1, n=11) or the novel Depletion 3.1 (D3.1, n=12) program. If indicated, additional CD34+ selections were performed (n=6). Eleven patients received T-cell-depleted grafts after reduced-intensity conditioning. RESULTS: The median log T-cell depletion was better with the D2.1 compared to the D3.1 (log 3.6 vs. log 2.3, p<0.05) and was further improved by introducing an immunoglobulin G (IgG)-blocking step (log 4.5 and log 3.4, respectively). The D3.1 was superior to the D2.1 (p<0.05) in median recovery of CD34+ cells (90% vs. 78%) and in median recovery of CD3- cells (87% vs. 76%). The median processing times per 10(10) total cells were 0.90 hours (D2.1) and 0.35 hours (D3.1). The transplanted grafts (directly T-cell-depleted products with or without positively selected CD34+ cells) contained a median of 10.5 x 10(6) per kg CD34+, 0.93x10(5) per kg CD3+, and 11.6x10(6) per kg CD56+. Rapid engraftment was achieved in 10 patients. The incidences of acute graft-versus-host disease were less than 10 percent (Grade I/II) and 0 percent (Grade III/IV). CONCLUSION: The novel D3.1 program with IgG blocking enables highly effective, time-saving large-scale T-cell depletion. Combining direct depletion techniques with standard CD34+ selection enables the composition of grafts optimized to the specific requirements of the patients.

Isolation and characterization of human myeloid progenitor populations--TpoR as discriminator between common myeloid and megakaryocyte/erythroid progenitors.

OBJECTIVE: The common myeloid progenitor (CMP) and its progeny, the granulocyte/monocyte progenitor (GMP) and megakaryocyte/erythrocyte progenitor (MEP), have been isolated based on the surface expression of CD34, IL-3Ralpha, and CD45RA. However, high resolution of IL-3Ralpha- and IL-3Ralphalo cells required to adequately separate the CMP and MEP populations is difficult to achieve. The aim of this study was to find a complementary surface marker to obtain a better separation of these two populations and to further characterize the acquired progenitor populations. MATERIALS AND METHODS: To evaluate the thrombopoietin receptor (TpoR) as a candidate marker, CD19-/CD34+/IL-3Ralphalo/-/CD45RA-/TpoR- (CMP), CD19-/CD34+/IL-3Ralphalo/CD45RA+/TpoR- (GMP), and CD19-/CD34+/IL-3Ralphalo/-/CD45RA-/TpoR+ (MEP) cells from human bone marrow were sorted to semisolid cultures for colony assays, and in addition analyzed for their surface expression of other growth factor receptors (GFRs) and sorted to real-time RT-PCR for gene expression analysis. RESULTS: The colony-formation and gene expression assays showed that inclusion of TpoR as a marker gave a distinct and reproducible separation of the myeloid progenitors. Furthermore, most GFR surface expression correlated to gene expression, but there were also striking discrepancies, in particular for the common beta-chain of the IL-3R, GM-CSFR, and IL-5R and for TpoR. CONCLUSION: Our data establish the TpoR as an important tool for isolation of the myeloid progenitors and demonstrate that the surface expression of GFRs cannot be predicted by their gene expression. Importantly, the refined isolation of CMPs will allow more detailed studies of regulatory mechanisms steering CMPs towards erythropoiesis vs granulopoiesis in steady state and response to peripheral demands.

Clonogenicity, gene expression and phenotype during neutrophil versus erythroid differentiation of cytokine-stimulated CD34+ human marrow cells in vitro.

With the objective to correlate clonogenicity, gene expression and phenotype during differentiation, human bone marrow CD34(+) cells were cultured in vitro to stimulate erythroid or neutrophil development, and sorted into five subpopulations according to their surface expression of CD15/CD33 and blood group antigen A/CD117 respectively. Sorted cells were cultured in methylcellulose and analysed by real-time reverse transcription polymerase chain reaction for expression of neutrophil and erythroid marker genes. Surface expression of CD15 coincided with restriction to neutrophil/monocyte differentiation and A antigen with restriction to erythroid differentiation. GATA-2 mRNA was down-regulated during both neutrophil and erythroid maturation, whereas GATA-1, SCL, ABO, erythropoietin receptor, Kell, glycophorin A, beta-globin and alpha-haemoglobin stabilizing protein were up-regulated during erythroid differentiation and silenced during neutrophil differentiation. CCAAT/enhancer-binding protein (C/EBP)-alpha, PU.1, granulocyte colony-stimulating factor receptor, PR3, C/EBP-epsilon and lactoferrin were sequentially expressed during neutrophil differentiation but rapidly down-regulated during the early erythroid stages. Nuclear factor erythroid-derived 2 (NF-E2) and glycophorin C were expressed both during neutrophil and erythroid differentiation. Our data support the notion of early expression of several lineage-associated genes prior to actual lineage commitment, defined by surface expression of CD15 and A antigen as markers for definitive neutrophil/monocyte and erythroid differentiation respectively. Previous findings, primarily from cell lines and mouse models, have been extended to adult human haematopoiesis.