Amniotic fluid as a novel source of mesenchymal stem cells for therapeutic transplantationHuman mesenchymal stem cells (MSCs) are multipotent stem cells, able to differentiate into multiple mesenchymal lineages. [1][2][3] Previously, we have shown that human fetal lung-derived MSCs enhance the engraftment of human umbilical cord blood (UCB)-derived CD34 ϩ hematopoietic cells in nonobese diabetic-severe combined immunodeficiency mice. 1 Here we show that secondtrimester amniotic fluid is an abundant source of fetal MSCs that exhibit a phenotype and multilineage differentiation potential similar to that of postnatal bone marrow (BM)-derived MSCs. We suggest that amniotic fluid is an attractive source of MSCs for cotransplantation in conjunction with UCB-derived hematopoietic stem cells.Amniotic fluid was collected transcervically from 6 secondtrimester legal terminations of pregnancy (mean gestational age, 19 weeks [range, 17-22 weeks]) according to a protocol approved by the medical ethical review board of our hospital. Amniotic fluid samples, without visible contamination with blood, were centrifuged for 10 minutes at 1283 rpm. Pellets were resuspended and cultured as described previously. 1 Adherent cells were detached with trypsin/EDTA (ethylenediaminetetraacetic acid) and phenotypically characterized by flow cytometry using fluorescein isothiocyanate-or phycoerythrin-conjugated antibodies. The adipogenic and osteogenic differentiation capacity of culture-expanded MSCs was determined as previously reported. 1 To confirm the fetal origin of cultured cells, a molecular HLA typing was performed on DNA obtained from expanded MSCs, and fetal and maternal blood cells by polymerase chain reaction/sequence-specific oligonucleotide using a reverse dot blot method. 4 MSCs were cultured from all 6 consecutive samples of second-trimester amniotic fluid. A quantity of 2 mL amniotic fluid was sufficient to culture these cells. The expansion potential of amniotic fluid-derived MSCs exceeded that of BM-derived MSCs. As a result, we were able to expand amniotic fluid MSCs to about 180 ϫ 10 6 cells within 4 weeks (3 passages). The phenotype of the culture-expanded amniotic fluid-derived cells was similar to that reported for MSCs derived from secondtrimester fetal tissues and adult BM 1,2 (Table 1). Amniotic fluidderived MSCs showed multilineage differentiation potential into fibroblasts, adipocytes, and osteocytes. Molecular HLA typing of fetal and maternal cells confirmed that the cultured cells were of fetal origin, without detectable contamination of maternal cells (Figure 1).Following allogeneic transplantation, most studies indicate that MSCs remain of host origin, 5 possibly as a result of the low frequency of these cells in stem cell grafts. The frequency of MSCs in UCB is particularly low, and most laboratories have been unable to grow MSCs from UCB. 6,7 Supplementing stem cell grafts with MSCs to promote engraftment has been proposed. Studies in mice and sheep show that engraftment can be promoted by the addition of t...

Key Points The best survival benefit of HSCT is observed in patients with FA who are transplanted before 10 years with bone marrow after a fludarabine-based regimen. Long-term outcome of patients with FA after transplantation is mainly affected by secondary malignancies and chronic graft-versus-host disease.

Mesenchymal stem cells (MSCs) have been demonstrated to exert profound immunosuppressive properties on T cell proliferation. However, their effect on the initiators of the immune response, the dendritic cells (DCs), are relatively unknown. In the present study, the effects of MSCs on the differentiation and function of both monocyte-derived DCs and CD34+-derived DCs were investigated. Monocytes (CD1a-CD14+) were obtained from PB and were cultured with IL-4 and GM-CSF to induce differentiation into CD14-CD1a+ immature DCs. CD34+ hematopoietic progenitor cells were isolated from umbilical cord blood samples and cultured in the presence of GM-CSF, TNF-a, and SCF to generate Langerhans cells, which differentiate directly into CD1a+ DCs, and dermal/interstitial DCs, which differentiate via an intermediate CD14+CD1a- phenotype into CD14-CD1a+ DCs. MSCs were generated from fetal lung tissue as reported previously (Exp. Hematol.2002; 30: 870–878). The phenotype (CD1a, CD14, CD80, CD86, CD83, HLA-DR, CD40) of the cells was analyzed by flow cytometry; cytokine production (IL-12, TNF-α) was examined by enzyme-linked immunosorbent assay (ELISA) and T cell stimulatory capacity was determined by a mixed lymphocyte reaction (MLR). The presence of MSCs during the complete differentiation period completely prevented the generation of immature DCs (CD1a+CD14-) from monocytes in a dose-dependent manner. MSCs in the upper wells of a transwell culture system inhibited the differentiation of monocytes in the lower wells, indicating that the suppressive effect of MSCs was mediated via soluble factors. The inhibitory effect of MSCs on the differentiation of DCs was partially prevented by the addition of neutralizing antibodies to IL-6 and M-CSF, indicating the involvement of these cytokines. Upon removal of MSCs cultured in a transwell after 48h, differentiation of monocytes towards DCs was restored, indicating that the suppressive effect of MSCs was reversible. DCs generated in the presence of MSCs were unresponsive to signals inducing maturation (CD40 ligand, lipopolysaccharide), as demonstrated by the absence of CD83, CD80, CD86 and HLA-DR upregulation and the decreased production of the inflammatory cytokines TNF-α (76%) and IL-12 (79%). In addition, the T cell stimulatory capacity of mature DCs generated in the presence of MSCs was strongly reduced. MSCs also inhibited the generation of DCs from CD34+ progenitor cells by blocking the differentiation of CD14+CD1a- precursors into dermal/interstitial DCs, without affecting the generation of CD1a+ Langerhans cells. The inhibitory effect of MSCs on CD34+ cell differentiation was dose-dependent and resulted in both phenotypical and functional modifications, as demonstrated by a reduced expression of costimulatory molecules (CD80, CD86) and CD83, and hampered capacity to stimulate naïve T-cell proliferation (50,112 ± 1,305 cpm versus 20,412 ± 1,593 cpm). Taken together, these data demonstrate that MSCs, next to the anti-proliferative effect on T cells, have a profound inhibitory effect on the generation and function of both monocyte- and CD34+-derived DCs, indicating that MSCs are able to modulate immune responses at multiple levels.

Adoptive transfer of T cell receptor (TCR)-transduced T cells may be an attractive strategy to target both hematological malignancies and solid tumors. By introducing a TCR, large numbers of T cells with defined antigen (Ag) specificity can be obtained. However, by introduction of a TCR, mixed TCR dimers can be formed. Besides the decrease in TCR expression of the introduced and endogenous TCR, these mixed TCR dimers could harbor potentially harmful specificities. In this study, we demonstrate that introduction of TCRs resulted in formation of neoreactive mixed TCR dimers, composed of the introduced TCR chains pairing with either the endogenous TCR α or β chain. Neoreactivities observed were HLA class I or class II restricted. Most neoreactive mixed TCR dimers were allo-HLA reactive; however, neoreactive mixed TCR dimers with autoreactive activity were also observed. We demonstrate that inclusion of an extra disulfide bond between the constant domains of the introduced TCR markedly reduced neoreactivity, whereas enhanced effectiveness of the introduced TCR was observed. In conclusion, TCR transfer results in the formation of neoreactive mixed TCR dimers with the potential to generate off-target effects, underlining the importance of searching for techniques to facilitate preferential pairing.

Purpose Cytarabine plays a pivotal role in the treatment of patients with acute myeloid leukemia (AML). Most centers use 7 to 10 days of cytarabine at a daily dose of 100 to 200 mg/m2 for remission induction. Consensus has not been reached on the benefit of higher dosages of cytarabine. Patients and Methods The European Organisation for Research and Treatment of Cancer (EORTC) and Gruppo Italiano Malattie Ematologiche dell' Adulto (GIMEMA) Leukemia Groups conducted a randomized trial (AML-12; Combination Chemotherapy, Stem Cell Transplant and Interleukin-2 in Treating Patients With Acute Myeloid Leukemia) in 1,942 newly diagnosed patients with AML, age 15 to 60 years, comparing remission induction treatment containing daunorubicin, etoposide, and either standard-dose (SD) cytarabine (100 mg/m2 per day by continuous infusion for 10 days) or high-dose (HD) cytarabine (3,000 mg/m2 every 12 hours by 3-hour infusion on days 1, 3, 5, and 7). Patients in complete remission (CR) received a single consolidation cycle containing daunorubicin and intermediate-dose cytarabine (500 mg/m2 every 12 hours for 6 days). Subsequently, a stem-cell transplantation was planned. The primary end point was survival. Results At a median follow-up of 6 years, overall survival was 38.7% for patients randomly assigned to SD cytarabine and 42.5% for those randomly assigned to HD cytarabine (log-rank test P = .06; multivariable analysis P = .009). For patients younger than age 46 years, survival was 43.3% and 51.9%, respectively (P = .009; multivariable analysis P = .003), and for patients age 46 to 60 years, survival was 33.9% and 32.9%, respectively (P = .91). CR rates were 72.0% and 78.7%, respectively (P < .001) and were 75.6% and 82.4% for patients younger than age 46 years (P = .01) and 68.3% and 74.8% for patients age 46 years and older (P = .03). Patients of all ages with very-bad-risk cytogenetic abnormalities and/or FLT3-ITD (internal tandem duplication) mutation, or with secondary AML benefitted from HD cytarabine. Conclusion HD cytarabine produces higher remission and survival rates than SD cytarabine, especially in patients younger than age 46 years.