Alkylating chemotherapeutic agents cyclophosphamide and melphalan cause functional injury to human bone marrow-derived mesenchymal stem cells.

The adverse effects of melphalan and cyclophosphamide on hematopoietic stem cells are well-known; however, the effects on the mesenchymal stem cells (MSCs) residing in the bone marrow are less well characterised. Examining the effects of chemotherapeutic agents on patient MSCs in vivo is difficult due to variability in patients and differences in the drug combinations used, both of which could have implications on MSC function. As drugs are not commonly used as single agents during high-dose chemotherapy (HDC) regimens, there is a lack of data comparing the short- or long-term effects these drugs have on patients post treatment. To help address these problems, the effects of the alkylating chemotherapeutic agents cyclophosphamide and melphalan on human bone marrow MSCs were evaluated in vitro. Within this study, the exposure of MSCs to the chemotherapeutic agents cyclophosphamide or melphalan had strong negative effects on MSC expansion and CD44 expression. In addition, changes were seen in the ability of MSCs to support hematopoietic cell migration and repopulation. These observations therefore highlight potential disadvantages in the use of autologous MSCs in chemotherapeutically pre-treated patients for future therapeutic strategies. Furthermore, this study suggests that if the damage caused by chemotherapeutic agents to marrow MSCs is substantial, it would be logical to use cultured allogeneic MSCs therapeutically to assist or repair the marrow microenvironment after HDC.

Chemotherapy-induced mesenchymal stem cell damage in patients with hematological malignancy.

Hematopoietic recovery after high-dose chemotherapy (HDC) in the treatment of hematological diseases may be slow and/or incomplete. This is generally attributed to progressive hematopoietic stem cell failure, although defective hematopoiesis may be in part due to poor stromal function. Chemotherapy is known to damage mature bone marrow stromal cells in vitro, but the extent to which marrow mesenchymal stem cells (MSCs) are damaged by HDC in vivo is largely unknown. To address this question, the phenotype and functional properties of marrow MSCs derived from untreated and chemotherapeutically treated patients with hematological malignancy were compared. This study demonstrates a significant reduction in MSC expansion and MSC CD44 expression by MSCs derived from patients receiving HDC regimens, thus implicating potential disadvantages in the use of autologous MSCs in chemotherapeutically pretreated patients for future therapeutic strategies. The clinical importance of these HDC-induced defects we have observed could be determined through prospective randomized trials of the effects of MSC cotransplantation on hematopoietic recovery in the setting of HDC with and without hematopoietic stem cell rescue.

Serial chimerism analyses indicate that mixed haemopoietic chimerism influences the probability of graft rejection and disease recurrence following allogeneic stem cell transplantation (SCT) for severe aplastic anaemia (SAA): indication for routine assessment of chimerism post SCT for SAA.

Ninety-one patients were studied serially for chimeric status following allogeneic stem cell transplantation (SCT) for severe aplastic anaemia (SAA) or Fanconi Anaemia (FA). Short tandem repeat polymerase chain reaction (STR-PCR) was used to stratify patients into five groups: (A) complete donor chimeras (n = 39), (B) transient mixed chimeras (n = 15) (C) stable mixed chimeras (n = 18), (D) progressive mixed chimeras (n = 14) (E) recipient chimeras with early graft rejection (n = 5). As serial sampling was not possible in Group E, serial chimerism results for 86 patients were available for analysis. The following factors were analysed for association with chimeric status: age, sex match, donor type, aetiology of aplasia, source of stem cells, number of cells engrafted, conditioning regimen, graft-versus-host disease (GvHD) prophylaxis, occurrence of acute and chronic GvHD and survival. Progressive mixed chimeras (PMCs) were at high risk of late graft rejection (n = 10, P < 0.0001). Seven of these patients lost their graft during withdrawal of immunosuppressive therapy. STR-PCR indicated an inverse correlation between detection of recipient cells post-SCT and occurrence of acute GvHD (P = 0.008). PMC was a bad prognostic indicator of survival (P = 0.003). Monitoring of chimeric status during cyclosporin withdrawal may facilitate therapeutic intervention to prevent late graft rejection in patients transplanted for SAA.

Influence of donor/recipient sex matching on outcome of allogeneic hematopoietic stem cell transplantation for aplastic anemia.

BACKGROUND: Increased risk of transplant related mortality in male recipients of female hematopoietic stem cell grafts and in vitro reactivity of lymphocytes against H-Y encoded gene products in females with rejected male grafts have been documented. An increased rejection of male grafts in female recipients is not reported for solid organ or stem cell transplants and the role of H-Y as transplantation antigen has been controversial. METHODS: Data from 1481 patients with a hematopoietic stem cell transplant for aplastic anemia reported from 154 centers in 28 countries were analyzed. Outcome was compared between patients with donors of the same or opposite sex. RESULTS: Survival at 5 years was significantly better in patients with donors from the same sex: 68% vs. 60% (P = 0.001). Male patients with female donors had a decreased survival (relative risk of death 1.52, P < 0.001) and an increased risk of severe graft-versus-host disease (relative risk 1.33, P = 0.03) compared to recipients of sex-matched grafts. Female patients with male donors had a decreased survival (relative risk of death 1.44, P = 0.01) and an increased risk of rejection (relative risk 2.20, P = 0.01) compared to recipients of sex-matched grafts. In a subgroup analysis, the negative effects of donor/recipient sex-mismatching appeared confined to patients receiving conditioning regimens not containing antithymocyte globulin. CONCLUSIONS: These data confirm H-Y as a clinically relevant transplantation antigen, in both the graft-versus-host and the host-versus-graft direction. Wherever possible, donor-recipient sex-matching should be integrated into donor selection algorithms.

Adult stem cell therapy beyond haemopoietic stem cell transplantation? An update.

The lifesaving potential of haemopoietic stem cell transplantation for the treatment of haematological malignancies and other life threatening disorders of the haemopoietic stem cell is universally accepted. In contrast, the use of adult marrow derived stem cells for tissue repair strategies in degenerative disease or after tissue damage are only in the early stages of evolution. A range of opinion exists within the general public and the scientific community about whether research with human embryonic stem cells is ethically acceptable. Further, the current paucity of human embryonic stem cell data has lead investigators to consider adult marrow as a potential source of stem cells to treat a wide range of degenerative disease and damaged tissues. Target disorders include osteoarthritis, diabetes mellitus, Parkinson's disease, ischaemic heart disease and retinal degeneration. Obvious advantages of this approach, if successful, would be fewer ethical hurdles compared with embryonic stem cells. Treatment with the patients own marrow stem cells would eliminate the possibility of allogeneic rejection.

Bone marrow-derived mesenchymal stem cells.

Human mesenchymal stem cells (MSCs) contribute to the regeneration of mesenchymal tissues, and are essential in providing support for the growth and differentiation of primitive hemopoietic cells within the bone marrow microenvironment. Techniques are now available to isolate human MSCs and manipulate their expansion in vitro under defined culture conditions without change of phenotype or loss of function. Mesenchymal stem cells have generated a great deal of interest in many clinical settings, including that of regenerative medicine, immune modulation and tissue engineering. Studies have already demonstrated the feasibility of transplanted MSCs providing crucial new cellular therapy. In this review, many aspects of the MSC will be discussed, with the main focus being on clinical studies that describe the potential of MSCs to treat patients with hematological malignancies who are undergoing chemotherapy and/or radiotherapy.

Outcome of pregnancy and disease course among women with aplastic anemia treated with immunosuppression.

BACKGROUND: Aplastic anemia may develop during pregnancy and sometimes improves spontaneously after delivery. The effects of pregnancy on aplastic anemia after immunosuppressive treatment and of aplastic anemia on the outcome of pregnancy have not been described. OBJECTIVE: To determine the outcome of pregnancy and the disease course among women with aplastic anemia who received immunosuppressive therapy. DESIGN: Retrospective multicenter study. SETTING: Twelve centers participating in the European Group for Blood and Marrow Transplantation. PATIENTS: 36 women who received immunosuppressive therapy to treat aplastic anemia. MEASUREMENTS: Outcomes of pregnancy and aplastic anemia and blood counts before, during, and after delivery. RESULTS: The 36 pregnancies resulted in 34 live births (one set of twins), 2 elective abortions, and 1 spontaneous abortion. Of the 36 pregnancies, 22 were uncomplicated and 14 involved medical complications. Seven pregnancies (19%) were complicated by relapse of aplastic anemia, and 5 patients without relapse (14%) needed transfusions during delivery. After delivery, 3 of the 7 patients who had relapse recovered spontaneously and 3 recovered after retreatment. One patient who did not respond to treatment died of aplastic anemia. A woman with aplastic anemia and paroxysmal nocturnal hemoglobinuria had a fatal cerebral thrombosis after delivery. Women with uneventful pregnancies had better prepregnancy remission status (8 complete and 11 partial remissions) and a higher median platelet count (146 x 10(9) cells/L) than did women with complicated pregnancies (2 complete remissions, 8 partial remissions, and 4 cases of paroxysmal nocturnal hemoglobinuria; median platelet count, 92 x 10(9) cells/L). CONCLUSIONS: Successful pregnancy with normal outcome is possible in women with aplastic anemia previously treated with immunosuppression. Complications appear to be more likely in patients with low platelet counts and paroxysmal nocturnal hemoglobinuria-associated aplastic anemia.

Matched-related donor transplantation for sickle cell disease: report from the Center for International Blood and Transplant Research.

We report outcomes after myeloablative haematopoietic cell transplantation (HCT) from human leucocyte antigen (HLA)-matched sibling donors in 67 patients with sickle cell disease transplanted between 1989 and 2002. The most common indications for transplantation were stroke and recurrent vaso-occlusive crisis in 38% and 37% of patients respectively. The median age at transplantation was 10 years and 67% of patients had received >10 red blood cell transfusions before HCT. Twenty-seven percent of patients had a poor performance score at transplantation. Ninety-four percent received busulfan and cyclophosphamide-containing conditioning regimens and bone marrow was the predominant source of donor cells. Most patients achieved haematopoietic recovery and no deaths occurred during the early post-transplant period. Rates of acute and chronic graft-versus-host disease were 10% and 22% respectively. Sixty-four of 67 patients are alive with 5-year probabilities of disease-free and overall survival of 85% and 97% respectively. Nine patients had graft failure with recovery of sickle erythropoiesis, eight of who had recurrent sickle-related events. This report confirms and extends earlier reports that HCT from HLA-matched related donors offers a very high survival rate, with few transplant-related complications and the elimination of sickle-related complications in the majority of patients who undergo this therapy.

Cytokine expansion culture of cord blood CD34+ cells induces marked and sustained changes in adhesion receptor and CXCR4 expressions.

Recent studies have demonstrated defective bone marrow homing of hematopoietic stem cells after cytokine expansion culture. Adhesion receptors (ARs) are essential to the homing process, and it is possible that cytokine culture modulates AR expression. We studied changes in expression of very late antigen-4 (VLA-4), VLA-5, L-selectin, leukocyte function-associated antigen-1 (LFA-1), CD44, and the stromal cell-derived factor-1 (SDF-1) receptor, CXCR4, during cytokine culture of cord blood (CB) CD34(+) cells. Expression of ARs was studied by flow cytometry on CB CD34(+) cells in whole blood, after purification and during culture for up to 10 days. Cells were cultured with stem cell factor (SCF), thrombopoietin (TPO), Flt3-ligand (Flt3), and G-CSF. Results showed that 80% or more of uncultured CD34(+) cells were positive for VLA-4, L-selectin, LFA-1, CD44, and CXCR4 while 50% were positive for VLA-5. Purification of CD34(+) cells did not affect AR expression, but cytokines increased expression three- to nine-fold throughout the 10-day culture period. In contrast, expression of CXCR4 decreased. Expression changes of ARs and CXCR4 on CD34(+)/CD38(-) cells mirrored those of the total CD34(+) population. The results indicate that cytokine culture significantly increases AR expression on CB CD34(+) cells, which may be related to the decrease in homing of cytokine-cultured hematopoietic stem cells.

Cobblestone area-forming cells in human cord blood are heterogeneous and differ from long-term culture-initiating cells.

The long-term culture-initiating cell (LTC-IC) assay is a physiological approach to the quantitation of primitive human hematopoietic cells. The readout using identification of cobblestone area-forming cells (CAFC) has gained popularity over the LTC-IC readout where cells are subcultured in a colony-forming cell assay. However, comparing the two assays, cord blood (CB) mononuclear cell (MNC) samples were found to contain a higher frequency of CAFC than LTC-IC (126 +/- 83 versus 40 +/- 31 per 10(5) cells, p = 0.0001). Overall, 60% of week-5 cobblestones produced by CB MNC were not functional LTC-IC and were classified as "false." Separation of CB MNC using immunomagnetic columns showed that false cobblestones were CD34(-)/lineage(+). Purified CD34(+) cells, as expected, gave very similar readouts in the two assays, with 4,084 and 3,468/10(5) cells being CAFC and LTC-IC, respectively. CD34(-)/lineage(-) cells did not form cobblestones or become CD34(+) on stroma or in cytokine culture. Human CB MNC contain a population of mature lineage(+) cells, possibly mature T or B cells, which, although producing cobblestone areas (CA), are not functional LTC-IC. The CAFC readout by this method, therefore, is unreliable for estimation of primitive hematopoietic cells by limiting dilution analysis in whole human CB or MNC and also may not detect CD34(-) CA stem cells.

Interleukin-10 and tumor necrosis factor alpha region haplotypes predict transplant-related mortality after unrelated donor stem cell transplantation.

Certain cytokine gene polymorphisms have been shown to correlate with outcome of human leukocyte antigen (HLA) identical sibling donor stem cell transplantation (SCT), but in unrelated donor SCT such information is scarce. We have studied the association between cytokine gene polymorphism and transplant-related mortality (TRM) in 182 unrelated SCTs performed at a single center. We found association of polymorphism in the tumor necrosis factor alpha (TNF alpha) and interleukin-10 (IL-10) gene and TRM. Both the TNFd4 allele and the TNF alpha -1031C alleles are associated with high risk for TRM. Statistical analysis showed that both polymorphisms were present on a single haplotype. This haplotype was associated with high risk of TRM when present in recipient or donor, 55% (43%-67%) compared with 21% (12%-30%) when absent from both (P <.01). A further allele associated with this haplotype, TNFa5, is also associated with increased risk of TRM. For IL-10, presence of the donor R2-G-C-C haplotype was associated with decreased risk of TRM, 61% (43%-79%) versus 34% (25%-43%), P =.01. In contrast, possession of the R3-G-C-C haplotype by the donor predicted reduced risk of TRM, 30% (19%-41%, 95% CI) versus 53% (40%-66%, 95% CI), P =.01. No independent associations of cytokine polymorphisms with acute graft-versus-host disease were shown.

Adult bone marrow is a rich source of human mesenchymal 'stem' cells but umbilical cord and mobilized adult blood are not.

In postnatal life, mesenchymal stem cells (MSC) self-replicate, proliferate and differentiate into mesenchymal tissues, including bone, fat, tendon, muscle and bone marrow (BM) stroma. Possible clinical applications for MSC in stem cell transplantation have been proposed. We have evaluated the frequency, phenotype and differentiation potential of MSC in adult BM, cord blood (CB) and peripheral blood stem cell collections (PBSC). During culture, BM MSC proliferated to confluence in 10-14 d, maintaining a stable non-haemopoietic phenotype, HLA class-1+, CD29+, CD44+, CD90+, CD45-, CD34- and CD14 through subsequent passages. Using the colony forming unit fibroblasts assay, the estimated frequency of MSC in the BM nucleated cell population was 1 in 3.4 x 10(4) cells. Both adipogenic and osteogenic differentiation of BM MSC was demonstrated. In contrast, CB and PBSC mononuclear cells cultured in MSC conditions for two passages produced a population of adherent, non-confluent fibroblast-like cells with a haemopoietic phenotype, CD45+, CD14+, CD34-, CD44-, CD90- and CD29-. In paired experiments, cultured BM MSC and mature BM stroma were seeded with CB cells enriched for CD34+. Similar numbers of colony-forming units of granulocytes-macrophages were produced by MSC-based and standard stroma cultures over 10 weeks. We conclude that adult BM is a reliable source of functional cultured MSC, but CB and PBSC are not.

Identification of the CD33-related Siglec receptor, Siglec-5 (CD170), as a useful marker in both normal myelopoiesis and acute myeloid leukaemias.

Sialic acid-binding immunoglobulin-like lectin (Siglec)-5 or CD170 is a CD33-related receptor, containing cytoplasmic immune receptor-based tyrosine signalling motifs, that has previously been reported to be myeloid-specific like CD33 and thus may be useful in the characterization of both normal and malignant haemopoiesis. This study showed that Siglec-5 had a distinct expression pattern to CD33 both on normal myeloid cells and in acute myeloid leukaemia (AML). In normal bone marrow and cord blood, myeloid cells predominantly expressed Siglec-5 at the later stages of granulocytic differentiation. Siglec-5 was not expressed at significant levels by CD34+ progenitors either from bone marrow or mobilized peripheral blood. During in vitro myeloid differentiation of cord blood purified CD34+ cells, Siglec-5 was upregulated later than CD33. Siglec-5 expression remained absent or very low on cultured CD34+ cells, unlike CD33, which was present on almost all CD34+ cells by day 4. However, analysis of blasts from 23 patients with AML revealed aberrant expression of Siglec-5 with CD34 in 50% (seven of 14) of patients with CD34+ AML; 61% (14 of 23) of AML cases were positive for Siglec-5 with an increased frequency in the French-American-British subtypes M3-5 (80%) compared with M0-2 (25%). All 13 acute lymphoblastic leukaemic (ALL) samples tested, including a CD33+ ALL, were Siglec-5 negative. These results support the further evaluation of Siglec-5 antibodies in the diagnosis and monitoring of AML.

Chromosome translocations and covert leukemic clones are generated during normal fetal development.

Studies on monozygotic twins with concordant leukemia and retrospective scrutiny of neonatal blood spots of patients with leukemia indicate that chromosomal translocations characteristic of pediatric leukemia often arise prenatally, probably as initiating events. The modest concordance rate for leukemia in identical twins ( approximately 5%), protracted latency, and transgenic modeling all suggest that additional postnatal exposure and/or genetic events are required for clinically overt leukemia development. This notion leads to the prediction that chromosome translocations, functional fusion genes, and preleukemic clones should be present in the blood of healthy newborns at a rate that is significantly greater than the cumulative risk of the corresponding leukemia. Using parallel reverse transcriptase-PCR and real-time PCR (Taqman) screening, we find that the common leukemia fusion genes, TEL-AML1 or AML1-ETO, are present in cord bloods at a frequency that is 100-fold greater than the risk of the corresponding leukemia. Single-cell analysis by cell enrichment and immunophenotype/fluorescence in situ hybridization multicolor staining confirmed the presence of translocations in restricted cell types corresponding to the B lymphoid or myeloid lineage of the leukemias that normally harbor these fusion genes. The frequency of positive cells (10(-4) to 10(-3)) indicates substantial clonal expansion of a progenitor population. These data have significant implications for the pathogenesis, natural history, and etiology of childhood leukemia.

Effect of tolerance to noninherited maternal antigens on the occurrence of graft-versus-host disease after bone marrow transplantation from a parent or an HLA-haploidentical sibling.

In haploidentical transplantation, the mismatched haplotype of the donor can originate from either of the parents. We refer to such mismatched haplotypes as noninherited maternal antigens (NIMA haplotype) or noninherited paternal antigens (NIPA haplotype). To determine whether exposure to maternal HLA antigens benefits patients undergoing bone marrow transplantation, we analyzed graft failure and graft-versus-host disease (GVHD) after transplantations from parental or haploidentical sibling donors. We studied 269 patients receiving 1 or 2 HLA-A, -B, -DR antigen-mismatched sibling or parental non-T-cell-depleted bone marrow transplants for acute myelogenous leukemia, acute lymphoblastic leukemia, or chronic myelogenous leukemia between 1985 and 1997 that were reported to the International Bone Marrow Transplant Registry. Included were 121 (45%) NIMA-mismatched and 148 (55%) NIPA-mismatched transplantations. Sixty-three (52%) of the NIMA-mismatched transplants and 69 (47%) of the NIPA-mismatched transplants were from haploidentical sibling donors. Sibling transplantations mismatched for NIMA had similar rates of graft failure but lower rates of acute GVHD (P <.02) than NIPA-mismatched sibling transplantations. In the first 4 months after transplantation, mother-to-child transplantations involved significantly less chronic GVHD than father-to-child transplantations (P <.02). Treatment-related mortality (TRM) was significantly higher after parental transplantations (P =.009 for mother; P =.03 for father) than after haploidentical sibling transplantations mismatched for the NIMA. Non-T-cell-depleted bone marrow transplants donated by haploidentical siblings to recipients mismatched for NIPA and transplants donated by parents caused more acute and chronic GVHD and TRM than transplants donated by haploidentical siblings mismatched for NIMA.