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BACKGROUND: Endothelial progenitor cells (EPCs) have been identified among hematopoietic tissue-derived progenitor cells that are mobilized into the peripheral blood (PB) as a result of tissue injury. It therefore seems likely that circulating EPCs have therapeutic potential by aiding in the neovascularization of ischemic tissue. This study provides clinical data on the availability of circulating EPCs at steady state and after recombinant human granulocyte-colony-stimulating factor (rHuG-CSF) mobilization and their collection by leukapheresis. STUDY DESIGN AND METHODS: Eight healthy donors underwent rHuG-CSF treatment over 4 days, followed by leukapheresis. Blood samples taken before rHuG-CSF treatment and before apheresis as well as apheresis-collected samples were analyzed by flow cytometry and by real time reverse transcription-polymerase chain reaction for cells expressing EPC-specific surface markers and tissue markers, respectively, and for EPC colony-forming cells. RESULTS: The median PB concentration of CD34+133+ vascular endothelial growth factor receptor-2 (VEGFR-2)-+ EPCs increased 8-fold from steady state to mobilized, and the concentration of CD34+133-VEGFR-2+ EPCs increased by 10-fold. This mobilization pattern was similar to that of hematopoietic CD34+, CD133+, and CD34+117+ progenitor cells. The increase in the median circulating colony-forming unit EPC concentration was 10-fold over baseline. The median absolute number of CD34+133+VEGFR-2+ cells collected by large-volume leukapheresis was 0.8 x 10(6) per kg of body weight. In addition, a small subset of immature CD133+34- cells coexpressing VEGFR-2 was identified in mobilized PB and in the apheresis collection. EPC-specific cells contained in the apheresis product were also identified as expressing mRNA for the CD31 antigen, Tie-2, and VEGFR-2. CONCLUSION: Circulating EPCs represent a novel blood cell component that can be collected by apheresis in large quantities and can be used clinically, either unmanipulated or EPC-selected, for therapeutic vasculogenesis. [ABSTRACT FROM AUTHOR]

Six patients with advanced Hodgkin’s disease in which multiple conventional treatments (median prior chemotherapy regimens: seven), radiation therapy, and a prior autologous stem cell transplantation (SCT) had failed underwent allogeneic SCT following a fludarabine-based conditioning regimen. Median age was 29 years (22–30). Median time to progression after autologous SCT was 6 months (4–21). Disease status at transplant was refractory relapse (n = 3) and sensitive relapse (n = 3). Cell source was filgrastim-mobilized peripheral blood stem cells from an HLA-identical sibling (n = 4) or matched unrelated donor marrow (n = 2). Conditioning regimens were fludarabine–cyclophosphamide–antithymocyte globulin (n = 4), fludarabine–melphalan (n = 1) and fludarabine–cytarabine–idarubicin (n = 1). Myeloid recovery was prompt, with an absolute neutrophil count 500/μl on day 12 (11–15). Median platelet recovery to 20000/μl was on day 9 (0–60). Chimerism studies on day 30 indicated 100% donor-derived hematopoiesis in 4/5 evaluable patients (4/4 non-progressors). All responders (3/3) have ongoing 100% donor-derived chimerism. Acute graft-versus-host disease (GVHD) was diagnosed in 4/6 evaluable patients. Chronic GVHD was present in 2/4 evaluable patients. There were no regimen-related deaths. Overall day 100 transplant-related mortality was 2/6 (33%). Three patients have expired and three are alive and progression-free with a median follow-up of 9 months (6–26) post transplant. We conclude that allogeneic stem cell transplantation with fludarabine-based preparative regimens is feasible in these high-risk, heavily pretreated HD patients. Bone Marrow Transplantation (2000) 26, 615–620. [ABSTRACT FROM AUTHOR]

Background Some transplant-related complications, such as the engraftment syndrome, are thought to be mediated by cytokines released during expansion of hematopoietic progenitors at the time of neutrophil recovery. Since there is an inverse correlation between CD34[sup +] cell dose and time to neutrophil recovery, we sought to determine if peritransplant toxicity and early mortality were adversely affected by high CD34[sup +] cell doses. Methods: The study group included 186 women with breast cancer who received high-dose cyclophosphamide, carmustine, thiotepa and an autologous PBSC transplant. The median CD34[sup +] cell dose was 5.9 × 10[sup 6]/kg (1.0-154.7 × 10[sup 6]/kg). Patients were categorized by CD34[sup +] cell dose (1.0-3.5, 3.6-5.9, 6.0-19.9, and 20.0-154.7 × 10[sup 6]/kg) for assessment of outcomes. Results: Grades 2-4 mucositis occurred in 49%, cardiac toxicity in 7%, pulmonary toxicity in 5%, cystitis in 4%, diarrhea in 3%, renal toxicity in 1%, and central nervous system toxicity in 1%. A Grade 2-4 regimen-related toxicity occurred in 109 patients (59%) and Grade 3-4 in eight patients (4%). Overall survival was 100% at Day 30, 96% at Day 90, and 89% at 1 year. Treatment-related mortality was 3.8%. In multivariate analyses that included prior chemotherapy, disease status, visceral metastases, prior chest radiation and age, CD34[sup +] cell dose group was not an independent risk factor for Grade 2-4 mucositis, Grade 2-4 maximum toxicity, Grade ≥3 cumulative toxicity, 90 day survival or 1 year survival. Discussion: We conclude that CD34[sup +] cell doses >20 × 10[sup 6]/kg do not affect transplant outcome in a negative or positive fashion. [ABSTRACT FROM AUTHOR]

Background Blood stem cells collected by apheresis are largely mononuclear cells in nature, so manipulation of blood stem-cell components freequently requires more time and reagents than for a marrow harvest. Reducing the nucleated cell number in mobilized blood stemcell collections, while preserving hematopoietic progenitor content, would make such manipulations simpler and less costly, but only if debulking procedures were not complex. Methods We evaluated separation of light-density cells and enrichment of CD34 + cells from mobilized peripheral blood stem-cell collections by density gradient centrifugation over buoyant density solution 60 (BDS 60) in a single, closed vessel. Results Fifteen apheresis products from five normal volunteers and eight cancer patients contained 3.44 (range, 1.19-5.51) × 10 10 nucleated cells. Following processing and washing, there was a median 29% recovery of nucleated cells, 79% recovery of CD34 + cells, 2.49-fold enrichment of CD34 + cells, 0.96-log depletion of CD3 + cells, 0.48-log depletion of CD56 + cells, and 0.72-log depletion of CD19 + cells. Results of processing were affected by the variability in composition of the apheresis products. The enrichment of CD34 + cells varied by donor type, and there was a logarithmic relationship between the preprocessing percentage of CD19 + cells and the log reduction in CD19 + cells. Recovery of cells after thawing and washing was acceptable for processed cells cryopreserved at concentrations over the range of 0.01-1.5 × 10 8 /mL. Discussion These results demonstrate a simple method by which an apheresis product of 1-5 × 10 10 cells can be debulked effectively in a single, closed vessel. [ABSTRACT FROM AUTHOR]