Severe hematopoietic alterations in vitro, in bone marrow transplant recipients who develop graft-versus-host disease

Hematopoietic Dysfunction during Graft-Versus-Host Disease: A Self-Destructive Process?

Graft-versus-host disease (GvHD) is a major complication of allogeneic hematopoietic (stem) cell transplantation (HCT). Clinically, GvHD is associated with severe and long-lasting hematopoietic dysfunction, which may contribute to the high mortality of GvHD after HCT. During GvHD, excessive immune activation damages both hematopoietic stem and progenitor cells and their surrounding bone marrow niche, leading to a reduction in cell number and functionality of both compartments. Hematopoietic dysfunction can be further aggravated by the occurrence—and treatment—of HCT-associated complications. These include immune suppressive therapy, coinciding infections and their treatment, and changes in the microbiome. In this review, we provide a structured overview of GvHD-mediated hematopoietic dysfunction, including the targets in the bone marrow, the mechanisms of action and the effect of GvHD-related complications and their treatment. This information may aid in the identification of treatment options to improve hematopoietic function in patients, during and after GvHD.

Low content of clonogenic progenitors on day+18 is associated with acute graft-versus-host disease and predicts transplant-related mortality

A marrow reaction associated with acute-graft-versus-host disease (a-GVHD) has been demonstrated in experimental models; its existence in human transplantation is controversial. The aim of the present study was to investigate whether clonogenic marrow precursors are an early marker for a-GVHD and transplant-related mortality (TRM). We prospectively studied 133 patients for colony-forming units-granulocyte-monocyte (CFU-GM) at day +18/+19 posttransplantation. CFU-GM frequency below the 25th percentile was predictive of an acute GVHD score I°-IV° when evaluated in multivariate logistic regression analysis (odds ratio = 13.551, 95% confidence interval [CI]: 1.583-116.031, p = 0.01). In the group with a clonogenic frequency below the 25th percentile, the cumulative incidence of GVHD grades II-IV was significantly more frequent with respect to the group with a frequency greater than the 25th percentile, 86% versus 54% (Gray test: p = 0.02). In multivariate Cox proportional analysis, a CFU-GM frequency below the 25th percentile at day +18 was associated with reduced overall survival (OS) (hazard ratio = 1.778, 95% CI: 1.022-3.093, p = 0.04). Patients with a frequency of CFU-GM greater than the 25th percentile had increased TRM with respect to patients with a clonogenic cell frequency greater than the 25th percentile (33.5% vs. 13.0%, p = 0.01). Patients were divided based on median content of viable CD34+ cells, and measurement of viable CD34+ cells was predictive for OS (p = 0.005) and TRM (p = 0.003). A weak correlation was observed between CFU-GM frequency in marrow at day +18 and levels of IL-2 receptor (IL-2R) in plasma (r = -0.226, p = 0.03). We conclude that marrow progenitor cell counts, on day +18 may be a useful marker for identifying patients at risk for severe a-GVHD, TRM, and inferior survival.

Immune Reconstitution After Allogeneic Haematopoietic Cell Transplantation: From Observational Studies to Targeted Interventions

Immune reconstitution (IR) after allogeneic haematopoietic cell transplantation (HCT) represents a central determinant of the clinical post-transplant course, since the majority of transplant-related outcome parameters such as graft-vs.-host disease (GvHD), infectious complications, and relapse are related to the velocity, quantity and quality of immune cell recovery. Younger age at transplant has been identified as the most important positive prognostic factor for favourable IR post-transplant and, indeed, accelerated immune cell recovery in children is most likely the pivotal contributing factor to lower incidences of GvHD and infectious complications in paediatric allogeneic HCT. Although our knowledge about the mechanisms of IR has significantly increased over the recent years, strategies to influence IR are just evolving. In this review, we will discuss different patterns of IR during various time points post-transplant and their impact on outcome. Besides IR patterns and cellular phenotypes, recovery of antigen-specific immune cells, for example virus-specific T cells, has recently gained increasing interest, as certain threshold levels of antigen-specific T cells seem to confer protection against severe viral disease courses. In contrast, the association between IR and a possible graft-vs. leukaemia effect is less well-understood. Finally, we will present current concepts of how to improve IR and how this could change transplant procedures in the near future.

Acute GVHD after allogeneic hematopoietic transplantation affects early marrow reconstitution and speed of engraftment

Our aim was to study the influence of acute graft-versus-host disease (a-GVHD) on primary engraftment times after allogeneic transplantation. Primary engraftment and frequency of marrow granulocyte-macrophage colony-forming units and erythroid burst-forming units, at day +18, were studied in 126 allogeneic transplants. Patients were grouped according to the time when a-GVHD treatment with corticosteroids was started. The no-a-GVHD group are those who, during the first 3 months, had no need for a-GVHD treatment; the early-a-GVHD group are those who needed a-GVHD treatment within 19 days; and the postengraftment-a-GVHD group are those who were not on corticosteroid treatment at the time of engraftment but needed it after day +19. The no-a-GVHD group reached a neutrophil count (N) > 0.5 × 10(9)/L in a median of 17.8 days. The postengraftment-a-GVHD group reached N > 0.5 × 10(9)/L in a median of 21.4 days (p = 0.0003). The early-a-GVHD group had N > 0.5 × 10(9)/L in a median of +17.0 days (p = 0.23). When factors important for engraftment were studied in a multivariate analysis, postengraftment a-GVHD was a significant factor in delayed neutrophil and platelet engraftment. Both the early-a-GVHD and postengraftment-a-GVHD groups showed a significant reduction in frequency of granulocyte-macrophage colony-forming units and erythroid burst-forming units found in marrow at day +18. In conclusion, a-GVHD may influence early marrow reconstitution and is a relevant factor for primary myeloid and platelet engraftment.

Functional integrity in vitro of hematopoietic progenitor cells from patients with chronic myeloid leukemia that have achieved hematological remission after different therapeutic procedures

In this study, we have assessed the in vitro growth of hematopoietic progenitor cells (HPC) from chronic myeloid leukemia (CML) patients that have recovered after different treatments. Bone marrow cells were obtained from 33 CML patients, including patients at diagnosis, before treatment (n=12), and patients that have achieved hematological remission (and in most cases a major cytogenetic response) after different therapeutic procedures (n=21), including patients treated with Interferon-alpha (IFN; n=5), imatinib mesylate (IMATINIB; n=8) and patients that received an allogeneic hematopoietic cell transplant (HCT; n=8). Marrow cells were enriched for CD34(+) cells and cultured in a serum- and stroma-free liquid culture system, supplemented with a combination of 8 recombinant cytokines. Normal samples were studied as controls. HPC from CML patients before therapy showed deficient proliferation and expansion potentials in culture (140-fold increase in nucleated cell number and 1.3-fold increase in colony-forming cell number) as compared to normal progenitors (1200-fold increase in nucleated cell number and 25-fold increase in colony-forming cell number). In contrast, HPC from patients treated with IMATINIB showed growth potentials similar to those of normal progenitors. Progenitors from patients after HCT also showed significant proliferation and expansion capacities. Interestingly, progenitors from IFN-treated patients showed proliferation and expansion kinetics similar to those of cells from untreated patients. These results indicate that, although treatment of CML patients with IFN, IMATINIB or HCT resulted in complete hematological remission (and a major cytogenetic response), only patients treated with IMATINIB and, to a lesser extent, with HCT showed a full hematopoietic recovery, as determined by the in vitro growth of HPC in our culture system.

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.

Posttransplant hematopoiesis in patients undergoing sibling allogeneic stem cell transplantation reflects that of their respective donors although with a lower functional capability

We tested the principle of whether patient long-term hematopoiesis following allogeneic stem cell transplantation (allo-SCT) reflects the characteristics of the hematopoiesis of their respective donor. For this purpose, we analyzed bone marrow (BM) hematopoiesis using long-term cultures (LTC), delta assays, and clonogeneic assays as well as CD34+ cells and their subsets by flow cytometry in a series of 37 patients undergoing allo-SCT, and we compared it to that of their respective human leukocyte antigen-matched sibling donors in a paired study performed more than 1 year after the transplant procedure. Interestingly, the main factor that influenced post-allo-SCT BM hematopoiesis in the long term was donor hematopoiesis. Nevertheless, compared to their respective donors, patients exhibited a significantly lower number of colony-forming units granulomonocytic, burst-forming units erythroid, and immature progenitors (CD34++/CD38dim/CD90+/CD133+ cells, LTC-initiating cells, and colonies generated in the delta assay). Moreover, BM stromal function was diminished in patients undergoing allo-SCT compared to their donors. In addition, the presence of chronic graft-versus-host disease under immunosuppressive treatment also conditioned an impaired hematopoietic function. In summary, our study shows that BM hematopoiesis evaluated more than 1 year after an allo-SCT mainly reproduces that of their respective donors, although with a significantly decreased in vitro activity.