Rainer Ordemann

Acute graft-versus-host disease does not require alloantigen expression on host epithelium

Alloantigen expression on host antigen-presenting cells (APCs) is essential to initiate graft-versus-host disease (GvHD); therefore, alloantigen expression on host target epithelium is also thought to be essential for tissue damage. We tested this hypothesis in mouse models of GvHD using bone-marrow chimeras in which either major histocompatibility complex class I or class II alloantigen was expressed only on APCs. We found that acute GvHD does not require alloantigen expression on host target epithelium and that neutralization of tumor necrosis factor-α and interleukin-1 prevents acute GvHD. These results pertain particularly to CD4-mediated GvHD but also apply, at least in part, to CD8-mediated GvHD. These results challenge current paradigms about the antigen specificity of GvHD effector mechanisms and confirm the central roles of both host APCs and inflammatory cytokines in acute GvHD.

Treatment of refractory acute GVHD with third-party MSC expanded in platelet lysate-containing medium

Mesenchymal stem cells have been shown to mediate immunomodulatory effects. They have been used in patients with steroid-refractory acute GVHD (aGVHD), but their relevance as a therapeutic agent targeting aGVHD has still to be defined. In this case series, we report 13 patients with steroid-refractory aGVHD who received BM-derived MSC expanded in platelet lysate-containing medium from unrelated HLA disparate donors. MSC were characterized by their morphological, phenotypical and functional properties. All tested preparations suppressed the proliferation of in vitro activated CD4+ T cells. MSC were transfused at a median dosage of 0.9 × 106/kg (range 0.6–1.1). The median number of MSC applications was 2 (range 1–5). Only two patients (15%) responded and did not require any further escalation of immunosuppressive therapy. Eleven patients received additional salvage immunosuppressive therapy concomitant to further MSC transfusions, and after 28 days, five of them (45%) showed a response. Four patients (31%) are alive after a median follow-up of 257 days, including one patient who initially responded to MSC treatment. In our patient cohort, response to MSC transfusion was lower than in the series reported earlier. However, our experience supports the potential efficacy of MSC in the treatment of steroid-refractory aGVHD.

Host Dendritic Cells Alone Are Sufficient to Initiate Acute Graft-versus-Host Disease

Alloantigen expression on host APCs is essential to initiate graft-vs-host disease (GVHD); however, critical APC subset remains to be elucidated. We compared the ability of dendritic cells (DCs) and B cells to initiate acute GVHD by an add-back study of MHC class II-expressing APCs (II+/+) into MHC class II-deficient (II−/−) mice that were resistant to CD4-dependent GVHD. Injection of host-derived, but not donor-derived, II+/+ DCs or host-derived II+/+ B cells, was sufficient to break GVHD resistance of II−/− mice and induced lethal acute GVHD. By contrast, host-derived II+/+ B cells, both naive and LPS stimulated, failed to induce activation or tolerance of donor CD4+ T cells. Similarly, in a model of CD8-dependent GVHD across MHC class I mismatch injection of allogeneic DCs, but not B cells, induced robust proliferation of donor CD8+ T cells and broke GVHD resistance of chimeric recipients in which APCs were syngeneic to donors. These results demonstrate that host-derived DCs are critical in priming donor CD4+ and CD8+ T cells to cause GVHD, and selective targeting of host DCs may be a promising strategy to prevent GVHD.

Rapamycin extends murine lifespan but has limited effects on aging.

Aging is a major risk factor for a large number of disorders and functional impairments. Therapeutic targeting of the aging process may therefore represent an innovative strategy in the quest for novel and broadly effective treatments against age-related diseases. The recent report of lifespan extension in mice treated with the FDA-approved mTOR inhibitor rapamycin represented the first demonstration of pharmacological extension of maximal lifespan in mammals. Longevity effects of rapamycin may, however, be due to rapamycins effects on specific life-limiting pathologies, such as cancers, and it remains unclear if this compound actually slows the rate of aging in mammals. Here, we present results from a comprehensive, large-scale assessment of a wide range of structural and functional aging phenotypes, which we performed to determine whether rapamycin slows the rate of aging in male C57BL/6J mice. While rapamycin did extend lifespan, it ameliorated few studied aging phenotypes. A subset of aging traits appeared to be rescued by rapamycin. Rapamycin, however, had similar effects on many of these traits in young animals, indicating that these effects were not due to a modulation of aging, but rather related to aging-independent drug effects. Therefore, our data largely dissociate rapamycins longevity effects from effects on aging itself.

Ruxolitinib in corticosteroid-refractory graft-versus-host disease after allogeneic stem cell transplantation: A multicenter survey

Despite major improvements in allogeneic hematopoietic cell transplantation over the past decades, corticosteroid-refractory (SR) acute (a) and chronic (c) graft-versus-host disease (GVHD) cause high mortality. Preclinical evidence indicates the potent anti-inflammatory properties of the JAK1/2 inhibitor ruxolitinib. In this retrospective survey, 19 stem cell transplant centers in Europe and the United States reported outcome data from 95 patients who had received ruxolitinib as salvage therapy for SR-GVHD. Patients were classified as having SR-aGVHD (n=54, all grades III or IV) or SR-cGVHD (n=41, all moderate or severe). The median number of previous GVHD-therapies was 3 for both SR-aGVHD (1–7) and SR-cGVHD (1–10). The overall response rate was 81.5% (44/54) in SR-aGVHD including 25 complete responses (46.3%), while for SR-cGVHD the ORR was 85.4% (35/41). Of those patients responding to ruxolitinib, the rate of GVHD-relapse was 6.8% (3/44) and 5.7% (2/35) for SR-aGVHD and SR-cGVHD, respectively. The 6-month-survival was 79% (67.3–90.7%, 95% confidence interval (CI)) and 97.4% (92.3–100%, 95% CI) for SR-aGVHD and SR-cGVHD, respectively. Cytopenia and cytomegalovirus-reactivation were observed during ruxolitinib treatment in both SR-aGVHD (30/54, 55.6% and 18/54, 33.3%) and SR-cGVHD (7/41, 17.1% and 6/41, 14.6%) patients. Ruxolitinib may constitute a promising new treatment option for SR-aGVHD and SR-cGVHD that should be validated in a prospective trial.

Role of CXCR3-induced donor T-cell migration in acute GVHD

OBJECTIVE The chemokine receptor CXCR3 has an important role in the migration of effector T cells. To investigate the role of CXCR3 on donor cells in acute graft vs host disease (GVHD) we used a well-defined experimental bone marrow transplantation (BMT) model where acute GVHD is mediated by donor CD8(+) T cells against minor histocompatibility antigens. METHODS; Lethally irradiated C3H.SW recipients were transplanted from either wild-type B6 or CXCR3(-/-) B6 donors. Donor T-cell expansion was analyzed in the spleen and small intestine of recipients by FACS. Donor T-cell function was analyzed by cytokine secretion. The severity of acute GVHD was assessed by histopathological analysis of intestine and liver, GVHD clinical scores, and survival after BMT. RESULTS Significantly higher numbers of donor CD8(+) CXCR3(-/-) T cells were found in the spleen on days +7 and +14 compared to donor wild-type T cells. By contrast, the number of CD8(+) T cells in the small bowel of BMT recipients from CXCR3(-/-) donors was sevenfold lower than from wild-type donors. Systemic concentrations of INF-gamma and TNF-alpha were equivalent between groups. Animals that received CXCR3(-/-) donor T cells demonstrated diminished GI tract and liver damage and showed improved survival after BMT compared to recipients of wild-type donor cells (43% vs 0%, p<0.001). CONCLUSION The migration of donor CD8(+) T cells to GVHD target organs such as the intestine depends on the expression of CXCR3 and contributes significantly to GVHD damage and overall mortality.

Hematopoietic stem cells in co-culture with mesenchymal stromal cells - modeling the niche compartments in vitro

Background Hematopoietic stem cells located in the bone marrow interact with a specific microenvironment referred to as the stem cell niche. Data derived from ex vivo co-culture systems using mesenchymal stromal cells as a feeder cell layer suggest that cell-to-cell contact has a significant impact on the expansion, migratory potential and ‘stemness’ of hematopoietic stem cells. Here we investigated in detail the spatial relationship between hematopoietic stem cells and mesenchymal stromal cells during ex vivo expansion. Design and Methods In the co-culture system, we defined three distinct localizations of hematopoietic stem cells relative to the mesenchymal stromal cell layer: (i) those in supernatant (non-adherent cells); (ii) those adhering to the surface of mesenchymal stromal cells (phase-bright cells) and (iii) those beneath the mesenchymal stromal cells (phase-dim cells). Cell cycle, proliferation, cell division and immunophenotype of these three cell fractions were evaluated from day 1 to 7. Results Phase-bright cells contained the highest proportion of cycling progenitors during co-culture. In contrast, phase-dim cells divided much more slowly and retained a more immature phenotype compared to the other cell fractions. The phase-dim compartment was soon enriched for CD34+/CD38− cells. Migration beneath the mesenchymal stromal cell layer could be hampered by inhibiting integrin β1 or CXCR4. Conclusions Our data suggest that the mesenchymal stromal cell surface is the predominant site of proliferation of hematopoietic stem cells, whereas the compartment beneath the mesenchymal stromal cell layer seems to mimic the stem cell niche for more immature cells. The SDF-1/CXCR4 interaction and integrin-mediated cell adhesion play important roles in the distribution of hematopoietic stem cells in the co-culture system.

Enhanced allostimulatory activity of host antigen-presenting cells in old mice intensifies acute graft-versus-host disease

Older bone marrow transplantation (BMT) recipients are at heightened risk for acute graft-versus-host disease (GVHD) after allogeneic BMT, but the causes of this association are poorly understood. Using well-characterized murine BMT models we have explored the mechanisms of increased GVHD in older mice. GVHD mortality, morbidity, and pathologic and biochemical indices were all worse in old recipients. Donor T cell responses were significantly increased in old recipients both in vivo and in vitro when stimulated by antigen-presenting cells (APCs) from old mice, which also secreted more TNF-alpha and IL-12 after LPS stimulation. In a B6 --> B6D2F1 model, CD4(+) donor T cells but not CD8(+) T cells mediated more severe GVHD in old mice. We confirmed the role of aged APCs in GVHD using B6D2F1 BM chimeras created with either old or young BM. Four months after chimera creation, allogeneic BMT from B6 donors caused significantly worse GVHD in old BM chimeras. APCs from these mice also stimulated greater responses from allogeneic cells in vitro. These data demonstrate a hitherto unsuspected mechanism of amplified donor T cell responses by aged allogeneic host APCs that increases acute GVHD in aged recipients in this BMT model.

Direct contact with mesenchymal stromal cells affects migratory behavior and gene expression profile of CD133+ hematopoietic stem cells during ex vivo expansion

OBJECTIVE To investigate the impact of direct contact between mesenchymal stromal cells (MSCs) and CD133(+) hematopoietic stem cells in terms of expansion potential, differentiation, migratory capacity, and gene expression profile. MATERIALS AND METHODS CD133(+)-purified hematopoietic progenitor cells were cultured for 7 days on subconfluent MSCs supplemented with growth-factor-containing medium. After ex vivo expansion, nonadherent and adherent cells were collected and analyzed separately. RESULTS The adherent cell population was less differentiated than the nonadherent fraction. CXCR4 was upregulated in the adherent fraction, which was associated with a higher migration capacity toward a stromal cell-derived factor-1 gradient. Colony-forming unit granulocyte-macrophage and long-term culture-initiation cell assays demonstrated a higher clonogenicity and repopulating capacity of the adherent fraction. Genes involved in adhesion, cell-cycle control, motility, and self-renewal were more highly expressed in the adherent fraction. CONCLUSION Adhesion and direct cell-to-cell contact with an MSC feeder layer supports ex vivo expansion, migratory potential, and stemness of CD133(+) hematopoietic progenitor cells.

Assessment of dysplastic hematopoiesis: lessons from healthy bone marrow donors

Background According to WHO 2008 guidelines, the required percentage of cells manifesting dysplasia in the bone marrow to qualify as significant is 10% or over in one or more hematopoietic cell lineages, but this threshold is controversial. No ‘normal’ values have been established. Therefore, we investigated dyshematopoiesis in bone marrow aspirate squash preparations of 120 healthy bone marrow donors. Design and Methods Bone marrow squash slides of 120 healthy unrelated bone marrow donors were examined independently by 4 experienced morphologists. Samples were taken from the first aspiration during the harvest. Bone marrow preparation and assessment were performed according to WHO recommendations and ICSH guidelines. Results More than 10% dysmyelopoiesis could be detected in 46% of bone marrow aspirate squash preparations with 26% in 2 or more cell lineages and 7% in 3 cell lineages in healthy bone marrow donors. Donors under the age of 30 years exhibited more dysgranulopoietic changes and dysmegakaryopoietic changes (P<0.001) compared to the older donors. Female donors showed more dysgranulopoietic changes than male donors (P=0.025). The concordance rate between the 4 investigators was modest in dysgranulopoiesis but poor in dyserythropoiesis and dysmegakaryopoiesis. Conclusions The poor reliability of the 10% cut off was partly related to the proximity of the current criteria to the observed cut-off mean values of the normal population. These findings question the current WHO threshold of the 10% or over necessary for the percentage of cells manifesting dysplasia to be considered significant, and suggest that either a higher threshold would be more appropriate or different thresholds should be set for each lineage.