The immunosuppressive activity of mesenchymal stromal cells (MSCs) is well documented. However, the therapeutic benefit is completely unpredictable, thus raising concerns about MSC efficacy. One of ...the affecting factors is the unresolved conundrum that, despite being immunosuppressive, MSCs are undetectable after administration. Therefore, understanding the fate of infused MSCs could help predict clinical responses. Using a murine model of graft-versus-host disease (GvHD), we demonstrate that MSCs are actively induced to undergo perforin-dependent apoptosis by recipient cytotoxic cells and that this process is essential to initiate MSC-induced immunosuppression. When examining patients with GvHD who received MSCs, we found a striking parallel, whereby only those with high cytotoxic activity against MSCs responded to MSC infusion, whereas those with low activity did not. The need for recipient cytotoxic cell activity could be replaced by the infusion of apoptotic MSCs generated ex vivo. After infusion, recipient phagocytes engulf apoptotic MSCs and produce indoleamine 2,3-dioxygenase, which is ultimately necessary for effecting immunosuppression. Therefore, we propose the innovative concept that patients should be stratified for MSC treatment according to their ability to kill MSCs or that all patients could be treated with ex vivo apoptotic MSCs.
Bone marrow-derived mesenchymal stromal cells (MSCs) represent a population of nonhematopoietic cells, which play a crucial role in supporting hematopoiesis and can differentiate into various cell ...types such as osteocytes, chondrocytes, adipocytes, and myocytes. Due to their differentiation capability, MSCs emerge as promising candidates for therapeutic applications in tissue engineering. In addition, they display immunomodulatory properties that have prompted consideration of their potential use for treatment modalities aimed at the inhibition of immune responses. In this context, MSCs efficiently inhibit maturation, cytokine production, and T-cell stimulatory capacity of dendritic cells (DCs). They also markedly impair proliferation, cytokine secretion, and cytotoxic potential of natural killer cells and T lymphocytes. Furthermore, MSCs are able to inhibit the proliferation of B cells and their capacity to produce antibodies. Various animal models confirm the immunomodulatory properties of MSCs. Thus, administered MSCs prolong the survival of skin and cardiac allografts and ameliorate acute graft-versus-host disease (GVHD) as well as experimental autoimmune encephalomyelitis. Clinical studies enrolling patients with severe acute GVHD reveal that the administration of MSCs results in significant clinical responses. Due to their immunomodulatory capability and their low immunogenicity, MSCs represent promising candidates for the prevention and treatment of immune-mediated diseases.
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.
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.
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 beta1 or CXCR4.
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.
We report a prospective multicenter phase II study of haploidentical hematopoietic stem cell transplantation using CD3/CD19-depleted grafts after reduced intensity conditioning with fludarabine, ...thiotepa, melphalan and OKT-3.
Sixty-one adults with a median age of 46 years (range 19-65 years) have been enrolled. Diagnoses were acute myeloid leukemia (n=38), acute lymphoblastic leukemia (n=8), non-Hodgkin's lymphoma (n=6), myeloma (n=4), chronic myeloid leukemia (n=3), chronic lymphatic leukemia (n=1) and myelodysplastic syndrome (n=1). Patients were considered high risk because of refractory disease (n=18), cytogenetics (n=6), complete remission (≥ 2) (n=9), chemosensitive relapse in partial remission (n=4) or relapse after prior hematopoietic stem cell transplantation (n=15 allogeneic, n=8 autologous, n=1 both). At haploidentical hematopoietic stem cell transplantation, 30 patients were in complete remission and 31 in partial remission. Grafts contained a median of 7.0 × 10(6) (range 3.2-22) CD34(+) cells/kg, 4.2 × 10(4) (range 0.6-44) CD3(+) T cells/kg and 2.7 × 10(7) (range 0.00-37.3) CD56(+) cells/kg.
Engraftment was rapid with a median of 12 days to granulocytes more than 0.5 × 10(9)/L (range 9-50 days) and 11 days to platelets more than 20 × 10(9) (range 7-38 days). Incidence of grade IIIV acute graft-versus-host-disease and chronic graft-versus-host-disease was 46% and 18%, respectively. Non-relapse mortality on Day 100 was 23% and 42% at two years. Cumulative incidence of relapse/progression at two years was 31%. Kaplan-Meier estimated 1-year and 2-year overall survival with median follow up of 869 days (range 181-1932) is 41% and 28%, respectively.
This regimen allows successful haploidentical hematopoietic stem cell transplantation with reduced intensity conditioning in high-risk patients lacking a suitable donor. (clinicaltrials.gov identifier:NCT00202917).
Summary
Combinatory therapeutic approaches of different targeted therapies in acute myeloid leukaemia are currently under preclinical/early clinical investigation. To enhance anti‐tumour effects, we ...combined the tyrosine kinase inhibitor (TKI) midostaurin and T‐cell mediated immunotherapy directed against CD33. Clinically relevant concentrations of midostaurin abrogated T‐cell mediated cytotoxicity both after activation with bispecific antibodies and chimeric antigen receptor T cells. This information is of relevance for clinicians exploring T‐cell mediated immunotherapy in early clinical trials. Given the profound inhibition of T‐cell functionality and anti‐tumour activity, we recommend specific FLT3 TKIs for further clinical testing of combinatory approaches with T‐cell based immunotherapy.
This retrospective study assessed the use and long-term outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in patients with severe autoimmune diseases (ADs), reported to the ...European Society for Blood and Marrow Transplantation (EBMT) registry.
Between 1997 and 2014, 128 patients received allogeneic HSCT for various hematological (
= 49) and non-hematological (
= 79) refractory ADs. The median age was 12.7 years (0.2-62.2). Donors were syngeneic for seven, matched related for 46, unrelated for 51, haploidentical for 15, and cord blood for nine patients.
The incidence of grades II-IV acute graft-vs.-host disease (GvHD) was 20.8% at 100 days. Cumulative incidence of chronic GvHD was 27.8% at 5-years. Non-relapse mortality (NRM) was 12.7% at 100-days. Overall survival (OS) and Progression-Free Survival (PFS) were 70.2 and 59.4% at 5-years, respectively. By multivariate analysis, age <18 years, males, and more recent year of transplant were found to be significantly associated with improved PFS. Reduced conditioning intensity was associated with a lower NRM. On a subgroup of 64 patients with detailed information a complete clinical response was obtained in 67% of patients at 1-year.
This large EBMT survey suggests the potential of allogeneic HSCT to induce long-term disease control in a large proportion of refractory ADs, with acceptable toxicities and NRM, especially in younger patients.
Graft versus host disease (GvHD) remains a major complication after allogeneic hematopoietic stem cell transplantation and is the main cause of transplant-related mortality. In addition to visceral ...organ involvement, concomitant myelosuppression has been repeatedly described and the extent of cytopenia has been introduced into GvHD scoring systems. Both hematopoietic cells and cells that form the hematopoietic stem and progenitor cell niche have been identified as targets of GvHD. Although several contributing factors have been previously described, the pathophysiology of GvHD-mediated myelosuppression remains largely unclear and to date, no specific therapeutic interventions have achieved routine clinical application. This review focuses on the bone marrow as a target of GvHD, the factors that contribute to myelosuppression, and the possible therapeutic approaches.
The bone marrow (BM) microenvironment provides critical physical cues for hematopoietic stem and progenitor cell (HSPC) maintenance and fate decision mediated by cell-matrix interactions. However, ...the mechanisms underlying matrix communication and signal transduction are less well understood. Contrary, stem cell culture is mainly facilitated in suspension cultures. Here, we used bone marrow-mimetic decellularized extracellular matrix (ECM) scaffolds derived from mesenchymal stromal cells (MSCs) to study HSPC-ECM interaction. Seeding freshly isolated HSPCs adherent (AT) and non-adherent (SN) cells were found. We detected enhanced expansion and active migration of AT-cells mediated by ECM incorporated stromal derived factor one. Probing cell mechanics, AT-cells displayed naïve cell deformation compared to SN-cells indicating physical recognition of ECM material properties by focal adhesion. Integrin αIIb (CD41), αV (CD51) and β3 (CD61) were found to be induced. Signaling focal contacts via ITGβ3 were identified to facilitate cell adhesion, migration and mediate ECM-physical cues to modulate HSPC function.
We report a novel, noncovalent hydrogel system crosslinked solely by receptor–ligand interactions between biotin and avidin. The simple hydrogel synthesis and functionalization together with the ...widespread use of biotinylated ligands in biosciences make this versatile system suitable for many applications. The gels possess a range of tunable physical properties, including stiffness, lifetime, and swelling. The erosion rates, unexpectedly fast compared to the kinetic parameters for biotin–avidin, are explored in terms of stretching tensions on the polymers, a concept well‐known on the single‐molecule level, but largely unexplored in supramolecular systems. As proof of utility, the gels were functionalized with different peptide sequences to control human mesenchymal stromal cell morphology in 3D culture.
Teach an old dog new tricks: Chemically simple hydrogels, crosslinked solely by the interactions between avidin tetramers and biotinylated PEG chains, offer practical and theoretical insights. These customizable networks support human cells in 3D culture and possess a range of tunable physical properties (see scheme). The gels demonstrate how even tiny forces can disrupt nature's strongest noncovalent interaction in a supramolecular network.
Human cells from acute myeloid leukemia (AML) patients are frequently transplanted into immune-compromised mouse strains to provide an in vivo environment for studies on the biology of the disease. ...Since frequencies of leukemia re-initiating cells are low and a unique cell surface phenotype that includes all tumor re-initiating activity remains unknown, the underlying mechanisms leading to limitations in the xenotransplantation assay need to be understood and overcome to obtain robust engraftment of AML-containing samples. We report here that in the NSG xenotransplantation assay, the large majority of mononucleated cells from patients with AML fail to establish a reproducible myeloid engraftment despite high donor chimerism. Instead, donor-derived cells mainly consist of polyclonal disease-unrelated expanded co-transplanted human T lymphocytes that induce xenogeneic graft versus host disease and mask the engraftment of human AML in mice. Engraftment of mainly myeloid cell types can be enforced by the prevention of T cell expansion through the depletion of lymphocytes from the graft prior transplantation.
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