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Mitochondrial DNA (mtDNA) is a highly potent inflammatory trigger and is reportedly found outside the cells in blood in various pathologies. Platelets are abundant in blood where they promote hemostasis. Although lacking a nucleus, platelets contain functional mitochondria. On activation, platelets produce extracellular vesicles known as microparticles. We hypothesized that activated platelets could also release their mitochondria. We show that activated platelets release respiratory-competent mitochondria, both within membrane-encapsulated microparticles and as free organelles. Extracellular mitochondria are found in platelet concentrates used for transfusion and are present at higher levels in those that induced acute reactions (febrile nonhemolytic reactions, skin manifestations, and cardiovascular events) in transfused patients. We establish that the mitochondrion is an endogenous substrate of secreted phospholipase A2 IIA (sPLA2-IIA), a phospholipase otherwise specific for bacteria, likely reflecting the ancestral proteobacteria origin of mitochondria. The hydrolysis of the mitochondrial membrane by sPLA2-IIA yields inflammatory mediators (ie, lysophospholipids, fatty acids, and mtDNA) that promote leukocyte activation. Two-photon microscopy in live transfused animals revealed that extracellular mitochondria interact with neutrophils in vivo, triggering neutrophil adhesion to the endothelial wall. Our findings identify extracellular mitochondria, produced by platelets, at the midpoint of a potent mechanism leading to inflammatory responses.

Mitochondrial DNA (mtDNA) is a highly potent inflammatory trigger and is reportedly found outside the cells in blood in various pathologies. Platelets are abundant in blood where they promote hemostasis. Although lacking a nucleus, platelets contain functional mitochondria. On activation, platelets produce extracellular vesicles known as microparticles. We hypothesized that activated platelets could also release their mitochondria. We show that activated platelets release respiratory-competent mitochondria, both within membrane-encapsulated microparticles and as free organelles. Extracellular mitochondria are found in platelet concentrates used for transfusion and are present at higher levels in those that induced acute reactions (febrile nonhemolytic reactions, skin manifestations, and cardiovascular events) in transfused patients. We establish that the mitochondrion is an endogenous substrate of secreted phospholipase A2IIA (sPLA2-IIA), a phospholipase otherwise specific for bacteria, likely reflecting the ancestral proteobacteria origin of mitochondria. The hydrolysis of the mitochondrial membrane by sPLA2-IIA yields inflammatory mediators (ie, lysophospholipids, fatty acids, and mtDNA) that promote leukocyte activation. Two-photon microscopy in live transfused animals revealed that extracellular mitochondria interact with neutrophils in vivo, triggering neutrophil adhesion to the endothelial wall. Our findings identify extracellular mitochondria, produced by platelets, at the midpoint of a potent mechanism leading to inflammatory responses.

Platelets play a crucial role in the maintenance of hemostasis, as well as in thrombosis. Upon activation, platelets release small membrane-bound microparticles (MPs) containing bioactive proteins and genetic materials from their parental cells that may be transferred to, and exert potent biological effects in, recipient cells of the circulatory system. Platelets have been shown to contain an abundant and diverse array of microRNAs, and platelet-derived MPs are the most abundant microvesicles in the circulation. Here we demonstrate that human platelets activated with thrombin preferentially release their miR-223 content in MPs. These MPs can be internalized by human umbilical vein endothelial cells (HUVEC), leading to the accumulation of platelet-derived miR-223. Platelet MPs contain functional Argonaute 2 (Ago2)•miR-223 complexes that are capable of regulating expression of a reporter gene in recipient HUVEC. Moreover, we demonstrate a role for platelet MP-derived miR-223 in the regulation of 2 endogenous endothelial genes, both at the messenger RNA and protein levels. Our results support a scenario by which platelet MPs may act as intercellular carriers of functional Ago2•microRNA complexes that may exert heterotypic regulation of gene expression in endothelial cells, and possibly other recipient cells of the circulatory system.

Platelets play a crucial role in the maintenance of hemostasis, as well as in thrombosis. Upon activation, platelets release small membrane-bound microparticles (MPs) containing bioactive proteins and genetic materials from their parental cells that may be transferred to, and exert potent biological effects in, recipient cells of the circulatory system. Platelets have been shown to contain an abundant and diverse array of microRNAs, and platelet-derived MPs are the most abundant microvesicles in the circulation. Here we demonstrate that human platelets activated with thrombin preferentially release their miR-223 content in MPs. These MPs can be internalized by human umbilical vein endothelial cells (HUVEC), leading to the accumulation of platelet-derived miR-223. Platelet MPs contain functional Argonaute 2 (Ago2)•miR-223 complexes that are capable of regulating expression of a reporter gene in recipient HUVEC. Moreover, we demonstrate a role for platelet MP-derived miR-223 in the regulation of 2 endogenous endothelial genes, both at the messenger RNA and protein levels. Our results support a scenario by which platelet MPs may act as intercellular carriers of functional Ago2•microRNA complexes that may exert heterotypic regulation of gene expression in endothelial cells, and possibly other recipient cells of the circulatory system.

CD8+ CTLs are thought to play a role in the control of follicular lymphoma (FL). Yet, the link between CTL tissue distribution, activation status, ability to kill FL cells in vivo, and disease progression is still elusive. Pretreatment lymph nodes from FL patients were analyzed by IHC (n = 80) or by 3-color confocal microscopy (n = 10). IHC revealed a rich infiltrate of CD8+ granzyme B+ (GrzB) cells in FL interfollicular spaces. Accordingly, confocal microscopy showed an increased number of CD3+CD8+GrzB+ CTLs and a brighter GrzB staining in individual CTL in FL samples compared with reactive lymph nodes. CTLs did not penetrate tumor nodules. In 3-dimensional (3-D) image reconstructions, CTLs were detected at the FL follicle border where they formed lytic synapse-like structures with FL B cells and with apoptotic cells, suggesting an in situ cytotoxic function. Finally, although GrzB expression in CTLs did not correlate with risk factors, high GrzB content correlated with prolonged progression free-survival (PFS) after rituximab-combined chemotherapy. Our results show the recruitment of armed CTLs with a tumor-controlling potential into FL lymph nodes and suggest that CTL-associated GrzB expression could influence PFS in FL patients having received rituximab-combined chemotherapy.

CD8+CTLs are thought to play a role in the control of follicular lymphoma (FL). Yet, the link between CTL tissue distribution, activation status, ability to kill FL cells in vivo, and disease progression is still elusive. Pretreatment lymph nodes from FL patients were analyzed by IHC (n = 80) or by 3-color confocal microscopy (n = 10). IHC revealed a rich infiltrate of CD8+granzyme B+(GrzB) cells in FL interfollicular spaces. Accordingly, confocal microscopy showed an increased number of CD3+CD8+GrzB+CTLs and a brighter GrzB staining in individual CTL in FL samples compared with reactive lymph nodes. CTLs did not penetrate tumor nodules. In 3-dimensional (3-D) image reconstructions, CTLs were detected at the FL follicle border where they formed lytic synapse-like structures with FL B cells and with apoptotic cells, suggesting an in situ cytotoxic function. Finally, although GrzB expression in CTLs did not correlate with risk factors, high GrzB content correlated with prolonged progression free-survival (PFS) after rituximab-combined chemotherapy. Our results show the recruitment of armed CTLs with a tumor-controlling potential into FL lymph nodes and suggest that CTL-associated GrzB expression could influence PFS in FL patients having received rituximab-combined chemotherapy.

Milpied: Celgene: Honoraria, Research Funding.

Umbilical cord blood transplantation (UCBT) is an alternative in the absence of related or unrelated HLA-matched donor. Defects in the mechanisms of immuno-surveillance, due to the absence of antigen-experienced lymphoid subsets transferred in the cord blood unit (CBU), render recipients more prone to viral infections. Our center conducted a clinical trial testing the benefit of ex vivoamplification of the CD34+ fraction (using SCF, FLT3L, TPO and GCSF) enriched from one CBU on hematopoietic reconstitution, while the CD34- fraction was infused at the same time as the expanded fraction (NCT01034449). We intended to simultaneously evaluate the potential impact of such a procedure on the immune reconstitution following freeze-thaw cycle for the CD34- fraction and on the expansion potential of lymphoid progenitors from CD34+ fraction.

Adults patients with an indication for SCT and unable to tolerate MAC (age>45, comorbidities, previous high-dose therapy) were included after inform consent if no Id sibling, no MUD 9 (C or DQ mismatch accepted) to 10/10 HLA matches and no CBU fulfilling the HLA matching (≥ 4/6) and richness (≥ 3 to 4 × 107 TNC/kg before thawing) criteria were available. RIC consisted of Flu (40 mg/m2/d × 5d), Cyclophosphamide (50 mg/kg × 1d) ICT 2 Gy. GVHD prevention consisted of MMF (d-3 to d28) and CSA from d-3. Graft engineering: 1 CBU with > 2 TNC/kg < 3 and 4 to 6 HLA compatibilities was thawed, CD34+ cells were selected through magnetic device (Miltenyi) and submitted to ex-vivo expansion in SF medium ( HPO1-Macopharma) supplemented with SCF, Flt3l, G-CSF and TPO during 12 days, starting d-12 of the transplantation (Ivanovic, Cell Transplant 2011) CD34 neg cells were cryopreserved. On d0, expanded cells were washed and resuspended in HSA 4% and upon viability and sterility were injected to the pt. Cd34 neg cells were thawed and injected to the pt 3 h later.From 03/2010 to 06./2011 8 pts have been included, med age 55y.o. (26–64) with AL: 3, Hodgkin's: 2, MDS: 3. Pts had received 1 to 3 lines of Tx (med:2). For 1 pt the expanded product was contaminated and this pt then received a back-up unmanipulated CBU. He engrafted correctly and is AW at 14 m with full donor chimerism. For the 7 other pts, the ex-vivo median fold expansion of CD34+ cells and TNC was 39 (29–75) and 390 (127–526) respectively, leading to a graft that contained 1.3 to 13 × 106 CD34+ cells/kg (med: 2 × 106/kg). The CD34 neg counterpart contained 3 × 106 CD3+/kg (1–5) and 0,9 × 106 CD19+ cells/kg (0,3–1,5). At d42, 6/7 pts who received the expanded graft engrafted with ≥99% donors cells. A 2d RIC was performed followed by a double CBU transplant in the patient who did not engraft. That 2d graft again failed to engraft. However the patient remains alive at 9m. For the 6 pts who engrafted with the expanded product the time to reach 500, 1000 PMN's and 20 000 plts/mm3 was 7d (6–19), 8d (6–21) and 24d (0–39) respectively. The chimerism on WBC and CD3+cells (evaluated on d 15, 42, 60, 100, 180, 365) remains full donor up to 1 year + after transplant (1y+: 2 pts; 6m+: 1pt; 180d+: 1 pt; 60d+: 1pt) or to relapse (at 1y) in the one pt who relapsed. Five pts experienced an AGVHd (grade III-IV: 1 pt). With a median FU of 10m (2 to 18m) 7 pts are alive, 6 wo disease. One pt died 1y after transplant from relapse.Ex-vivo expansion of a single CBU is feasible and reproducible. Transplantation of the expanded product together with the CD34 neg counterpart of the same CBU produces rapid, complete and sustained donor engraftment after RIC in adults.No relevant conflicts of interest to declare.

Abstract 486

Since the mid 1985 the combination of hematopoietic growth factors and/or chemotherapy is applied to allow mobilization of CD34+ cells from marrow to the blood. (pHSC). Once harvested, this cell population, containing both progenitors (pHSC) and stem cells (HSC), has become the common source for autologous or/and allogeneic transplantations procedures. Indeed, the new development of cell-based therapies in hematologic settings requires the understanding of mechanism involved in HSC migration and cell cycle kinetics during mobilisation.With respect to the percentage and absolute number of CD34+ cells after Granulocyte-Colony Stimulating Factor mobilisation (G-CSF) the patients (Pts) and healthy donors were divided in two groups: Good mobilizers (GM) and poor mobilizers (PM). We studied in their CD34+ cells: cell cycle (Ki67/IP staining), clonogenic and ex vivo expansion potential, aldehyde deshydrogenase activity (Aldefluor), expression of some adhesion molecules relevant for CD34+cells mobilisation as: VLA-4, LFA-1 and CXCR4.Twenty Two Pts (Myeloma=13 and Lymphoma=9) and 9 healthy donors underwent G-CSF mobilisation with or without chemotherapy. CD34+ cells were purified using the MACS cell isolation kit and Mini-Macs columns obtaining a purity of more than 88%. Based on the percentage of circulating CD34+, 2 populations of subjects were identified (<0.1 %: PM and >0.1%: GM). Total white blood cells number was higher in PM arm (48.8 G/l) than in GM arm (36.75) (p= 0.03). The median pCD34+ cell was higher in GM (60: 31-153) than in PM (35: 11-64) (p= 0.001). Interestingly, PM showed more G0 cells than GM with mean percentages 46±10 and 31±10 respectively (p=0.004). Indeed, the percentage of the S/G2/M fraction of CD34+ cells was higher in GM (2±0.9) than in PM (0.69±0.7) (p= 0.002). Moreover, there was a trend to observe a higher total nucleated cells fold expansion potential in PM arm 27±11 versus 17±13 in GM (p=0.06). It should be stressed that those results were observed also when Pts and healthy donors were studied separately. Analysis of ALDH activity revealed an unexpected population of CD34+ cells that were ALDH+ despite their CD133 negativity. These CD34+ALDH+CD133− cells were present in both patients and healthy donors but were more pronounced in pts (38% in PM versus 9% in GM; p= 0.01). Moreover, GM among healthy donors showed more cells expressing VLA-4 (87 % versus 61 % in PM arm, p= 0.05)These results suggest important phenotypic and functional variations in CD34+ cells between PM and GM (cell cycle, expression of CD133 by ALDH+ cells) as well as some differences between the healthy donors and pts (VLA-4 expression and clonogenic capacity).No relevant conflicts of interest to declare.

Abstract 2143