Boost of CD34+-selected peripheral blood cells without further conditioning in patients with poor graft function following allogeneic stem cell transplantation.

BACKGROUND AND OBJECTIVES: A proportion of patients develop poor graft function (PGF) following an allogeneic hemopoietic stem cell transplant (HSCT). It is uncertain whether a boost of donor marrow or blood cells is beneficial in terms of trilineage recovery and non-relapse-related mortality (NRM). DESIGN AND METHODS: The aim of this study was to compare outcomes in patients with PGF and full donor chimerism following an allogeneic HSCT who did or did not receive a boost of donor stem cells. The study included patients with primary PGF--i.e. those failing to achieve sustained graft function- and secondary PGF--i.e. those developing PGF after complete hematologic recovery. We studied 54 patients with PGF: 20 patients received no further donor cell infusion (group A), 14 received a boost of unmanipulated marrow or blood cells from the original donor, without further conditioning (group B), and 20 received donor cells after CD34 selection without conditioning (group C). The three groups were comparable for disease phase, patients' age, donor type, primary or secondary PGF, full donor chimerism and duration of PGF. RESULTS: Trilineage recovery was seen in 40%, 36% and 75% of the patients in, respectively, groups A, B and C (p=0.02). In multivariate Cox analysis trilineage recovery was more frequent in patients with secondary PGF (RR of complete recovery 2.82, p=0.01) and in patients receiving CD34+-selected cells (RR of complete recovery 3.0; p=0.007). There was no effect of donor type on hematologic recovery. The rate of NRM was 55%, 64%, 20% in groups A, B and C, respectively (p=0.06) and was highly correlated with trilineage recovery (RR 0.36, p<0.0001). PGF was the primary cause of death in 30%, 21% and 10% of the patients in the three groups, graft-versus-host disease (GVHD) in 5%, 36%, and 10%. INTERPRETATIONS AND CONCLUSIONS: In patients with poor graft function (a) a boost of CD34+-selected peripheral blood donor cells is associated with a high chance of trilineage recovery and a low risk of acute GVHD; (b) a boost of unmanipulated donor cells does not seem to offer a survival advantage over no infusion of cells; and (c) NRM is lower when using peripheral blood cells for the boost. These data may be useful when discussing second stem cell donations for patients with poor graft function.

T-cell suppression mediated by mesenchymal stem cells is deficient in patients with severe aplastic anemia.

OBJECTIVE: To compare the suppressive effect of mesenchymal stem cells (MSC), derived from normal individuals or severe aplastic anemia patients (SAA), on T-cell activation. PATIENTS AND METHODS: We studied bone marrow MSC from 19 healthy donors and 23 SAA patients in different phases of the disease: at diagnosis (n = 3), following immunosuppressive therapy (IS) (n = 16), or after a bone marrow transplant (BMT) (n = 4). MSC were tested for T-cell suppression in the following assays: mixed lymphocyte reaction (MLR), phytohemaglutinin (PHA)-primed cultures, activation surface markers, gamma-IFN production, hematopoietic colony formation (CFC), production of cyclic ADP-ribose (cADPR). RESULTS: The abnormalities of SAA MSC included: 1) significantly lower suppression of T-cell proliferation induced by alloantigens (p = 0.009) or PHA (p = 0.006); 2) impaired capacity to suppress CD38 expression on PHA-primed T cells (p = 0.001); 3) impaired ability to suppress gamma-IFN production in PHA cultures, resulting in an 11-fold higher gamma-IFN concentration; 4) no preventive effect on T cell-mediated inhibition of CFC; and 5) significantly reduced (p = 0.009) production of cADPR, a universal calcium mobilizer. MSC-mediated suppression of PHA-induced T-cell proliferation was restored to control levels in 3 of 4 patients post-BMT. CONCLUSION: The ability of MSC to downregulate T-cell priming, proliferation, and cytokine release is deficient in patients with SAA, persists indefinitely after immunosuppressive therapy, but seems to be restored after BMT. Whether these abnormalities are relevant to the pathogenesis of aplastic anemia remains to be determined.

Cyclic ADP-ribose generation by CD38 improves human hemopoietic stem cell engraftment into NOD/SCID mice.

Cyclic ADP-ribose (cADPR) is a potent and universal intracellular calcium mobilizer, recently shown to behave as a new hemopoietic cytokine stimulating the in vitro proliferation of both committed and uncommitted human hemopoietic progenitors (HP). Here, we investigated the effects of cADPR on engraftment of hemopoietic stem cells (HSC) into irradiated NOD/SCID mice. Two different protocols were used: i) a 24 h in vitro priming of cord blood-derived mononuclear cells (MNC) with micromolar cADPR, followed by their infusion into irradiated mice (both primary and secondary transplants); and ii) co-infusion of MNC with CD38-transfected, cADPR-generating, irradiated murine 3T3 fibroblasts. We demonstrated a dual effect of cADPR on human HP in vivo: i) enhanced proliferation of committed progenitors, responsible for improvement of short-term engraftment; ii) expansion of HSC, with increased long-term human engraftment into secondary recipients and a significantly higher expansion factor of CD34+ progenitors in mice co-infused with MNC and CD38+ 3T3 fibroblasts. These results hold promise for the possible therapeutic use of cADPR, and of cADPR-producing stroma, to achieve long-term expansion of human HSC, that is, those HP capable of self-renewal and responsible for repopulation of the bone marrow.

Intra-bone marrow injection of bone marrow and cord blood cells: an alternative way of transplantation associated with a higher seeding efficiency.

OBJECTIVE: Intravenous (IV) injection is currently the normal method for transplanting hematopoietic cells. However, the problem of seeding efficiency and homing is relevant especially when a limited number of stem cells is available. Intra-bone marrow (IBM) injection of bone marrow cells (BMCs) may overcome this problem. MATERIALS AND METHODS: Irradiated (750 cGy) C57BL/6J mice were transplanted with 1 x 10(5) BMCs harvested from transgenic mice expressing an enhanced version of the green fluorescent protein (EGFP+) via IBM or with 1 x 10(6) EGFP+ BMCs via IV. Irradiated (320 cGy) NOD/SCID mice were transplanted with 1 x 10(6) human cord blood (CB) cells via IBM or with 1 x 10(7) human CB cells via IV. RESULTS: In C57BL/6J mice after 90 days, the fraction of EGFP+ cells harvested was 37% and 53% in IV-treated and IBM-treated (contralateral tibia and femur in the IBM) mice, respectively: the expansion folds were 114 and 1760, respectively. In NOD/SCID mice, the percentages of CD45+ cells and CD45+/CD34+ cells were, at 30 days, 3.3% and 0.3% in IV-treated mice, and 4.4% and 1.1% in IBM-treated mice. At 60 days, the percentages of CD45+ cells and CD45+/CD34+ cells were 2.1% and 0.3% in IV-treated mice and 1.4% and 0.4% in IBM-treated mice. At day 90 the percentages of CD45+ cells and CD45+/CD34+ cells were 3% and 0.3% in IV-treated mice and 2.3% and 0.4% in IBM-treated mice. CONCLUSION: Our data demonstrate that IBM transplantation is associated with a seeding efficiency 15 times greater than IV transplantation. IBM transplantation may improve the results of transplant and may be useful in several settings: 1) when a limited number of hematopoietic progenitors are available; and 2) in experiments aiming to place in the bone marrow stem cells of other lineages (CNS, muscle, etc.).

Concentrative uptake of cyclic ADP-ribose generated by BST-1+ stroma stimulates proliferation of human hematopoietic progenitors.

Cyclic ADP-ribose (cADPR) is an intracellular calcium mobilizer generated from NAD(+) by the ADP-ribosyl cyclases CD38 and BST-1. cADPR, both exogenously added and paracrinally produced by a CD38(+) feeder layer, has recently been demonstrated to stimulate the in vitro proliferation of human hemopoietic progenitors (HP) and also the in vivo expansion of hemopoietic stem cells. The low density of BST-1 expression on bone marrow (BM) stromal cells and the low specific activity of the enzyme made it unclear whether cADPR generation by a BST-1(+) stroma could stimulate HP proliferation in the BM microenvironment. We developed and characterized two BST-1(+) stromal cell lines, expressing an ectocellular cyclase activity similar to that of BST-1(+) human mesenchymal stem cells, the precursors of BM stromal cells. Long term co-culture of cord blood-derived HP over these BST-1(+) feeders determined their expansion. Influx of paracrinally generated cADPR into clonogenic HP was mediated by a concentrative, nitrobenzylthioinosine- and dipyridamole-inhibitable nucleoside transporter, this providing a possible explanation to the effectiveness of the hormone-like concentrations of the cyclic nucleotide measured in the medium conditioned by BST-1(+) feeders. These results suggest that the BST-1-catalyzed generation of extracellular cADPR, followed by the concentrative uptake of the cyclic nucleotide by HP, may be physiologically relevant in normal hemopoiesis.

Transplant-related mortality and long-term graft function are significantly influenced by cell dose in patients undergoing allogeneic marrow transplantation.

We have studied the impact of cell dose on short- and long-term graft function and outcome in 905 patients undergoing an unmanipulated allogeneic bone marrow transplantation (BMT) from an HLA-identical sibling (n = 735), a one-antigen mismatched related donor (n = 35), or a matched unrelated donor (n = 135). Median number of nucleated cells infused was 3.4 x 10(8)/kg (25th percentile 2.4 x 10(8)/kg, 75th percentile 5 x 10(8)/kg). Patients were stratified according to cells infused in 3 groups: < or = 2.4 x 10(8)/kg (n = 247; low dose); >2.4 x 10(8)/kg and < or = 5 x 10(8)/kg (n = 452; intermediate dose); and >5 x 10(8)/kg (n = 206; high dose). Patients receiving high cell dose had significantly higher platelet counts on days +20, +50, +100, +180, and +365 after BMT (P <.01) and higher white blood cell counts on days +50, +100, and +180 after BMT (P <.01) as compared with other patients. The actuarial 5-year transplant-related mortality (TRM) was 41% versus 36% versus 28% (P =.01); overall survival was 45% versus 51% versus 56% (P =.0008); and disease-free survival was 41% versus 42% versus 48%, respectively, (P =.04) in patients receiving low, intermediate, or high cell dose. The cell dose effect was more pronounced in patients older than 30 years of age, with advanced disease, with chronic myeloid leukemia, and with alternative donors. In multivariate Cox analysis on TRM, cell dose was a significant predictor (P =.002; relative risk 0.6) together with donor type (P =.0001), year of transplantation (P =.0001), conditioning regimen (P =.02), and recipient age (P =.02). In conclusion, transplantation of high marrow cell dose is associated with reduced transplant mortality and improved survival and results in improved graft function both short and long term.