Limbus damage in ocular graft-versus-host disease

Graft-versus-host disease (GVHD) is the major cause of morbidity and mortality among patients undergoing allogeneic hematopoietic stem cell transplantation. Although animal models have been clearly established for the study of skin, liver, and gut, currently there is no equivalent experiemental model for analyzing ocular involvement, which is rather common, especially among patients diagnosed with chronic GVHD. In the current study we have developed a murine model of ocular GVHD and, for the first time, we describe the histopathologic features involving cornea and limbus, which could play a role in the physiopathology of the disease at the ocular level. Our results represent a major finding that allows us to define a model for evaluating new therapeutic strategies for treating ocular GVHD prior to their use in clinical setting.

Short-term endothelial progenitor cell colonies are composed of monocytes and do not acquire endothelial markers

BACKGROUND

The aim of this study was to identify circulating endothelial progenitor cells (EPC) with colony-forming capacity and compare them with the monocytic-macrophage lineage.

METHODS

Forty-two healthy donors were analyzed. EPC were cultured with VEGF and b-FGF. Sequential studies were performed on days +7 (colonies) +21 and +35. Monocytic cells were cultured using the same conditions as EPC until day +21 or alternatively by adding IGF.

RESULTS

The number of EPC colonies was higher in BM than in mobilized or steady-state PB. Using EPC medium, monocytic cells formed cord-like structures but no colonies. However, colonies grew when IGF was added to the medium. By immunocytochemistry, colonies showed CD45, CD31 and lysozyme but no vWF. Colonies were CD4+, CD13+dim, CD14+, CD15++, CD16-/+dim, CD31+dim, CD33+dim, CD45+, CD105-/+dim, lysozyme+ and VE-cadherin+, and constantly negative for CD34, CD133 and KDR, when flow cytometry was used. The immunophenotype of pre-cultured and cultured monocytes was similar to that described for EPC.

DISCUSSION

Our results suggest that the so-called 'EPC' obtained at 7 days of culture belong to the monocyte-macrophage lineage, as they share immunophenotypic and molecular features.

Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is the most common and severe complication among patients surviving >100 days after allogeneic transplantation. It starts with the expansion of donor T cells in response to alloantigens or autoantigens that are unchecked by normal thymic or peripheral mechanisms of deletion. The T cells induce damage to target organs either directly through cytolytic attack, inflammatory cytokines and fibrosis, or by promoting B cell activation and production of autoantibodies. HLA disparity, donor and patient age and sex, source of progenitor cells, graft composition and previous acute GVHD are the main factors that predict the risk of developing cGVHD. Once the diagnosis has been established, patients needing treatment (extensive cGVHD) must be identified. Poor prognostic factors such as extensive skin involvement, thrombocytopenia and progressive-type onset of cGVHD must be considered in order to define the immunosuppressive treatment requirements. Prednisone, together with a calcineurin inhibitor such as ciclosporin or tacrolimus, can be considered the standard regimen as primary treatment for cGVHD. Using that approach, among high-risk patients (identified as those with extensive cGVHD plus thrombocytopenia) 3-year survival reached 52%. Concerning salvage regimens, to date there is no clear standard regimen for cGVHD treatment, the best choice being to enter the patient into a clinical trial. Immunosuppressive drugs that inhibit T cell activation, proliferation or survival, such as mycophenolate mofetil, the anti-interleukin-2 alpha receptor antagonist daclizumab, sirolimus (rapamycin), extracorporeal photopheresis and pentostatin (deoxycoformycin), among other agents, have been used with a very wide range of complete responses ranging from 5% to 50%. In addition, anti-cytokine or B cell inhibitors such as etanercept or rituximab have also been evaluated. The severe immunosuppression induced by those drugs increases the risk of infectious complications and may have a deleterious effect on the graft versus tumour effect after transplant so that newer strategies based on the selective depletion of alloreactive T cells and induction of more specific immunotolerance against host tissues are required.

Long-term bone marrow culture data are the most powerful predictor of peripheral blood progenitor cell mobilization in healthy donors

BACKGROUND AND OBJECTIVES

There is wide interindividual variation in progenitor cell mobilization. The present study was aimed to analyze steady state hematopoiesis in healthy donors and its influence on hematopoietic progenitor cell (HPC) mobilization.

DESIGN AND METHODS

Bone marrow (BM) was aspirated from 72 healthy donors prior to administration of recombinant human granulocyte colony-stimulating factor (G-CSF). Analyses of CD34+ cells and semisolid cultures as well as long-term cultures were performed from BM or leukapheresis products.

RESULTS

Male donors showed a higher number of BFU-E (p=0.007) and committed progenitors (p=0.05), a better stromal layer (p=0.02), and higher long-term bone marrow culture (LT-BMC) counts (p<0.05) when compared to those in female donors. When correlating the culture pattern of the BM with the data from the leukapheresis products, we observed that the number of the immature progenitors in BM correlated significantly with both the number of CD34 + cells and CFU-GM in the first leukapheresis. Univariate analysis revealed that the following variables had a beneficial impact on the number of CD34+ cells: male sex, body weight >73 Kg, G-CSF schedule and results of LT-BMC, although in the multivariate analysis only the number of CFU-GM obtained after LT-BMC showed a significant influence (p<0.001).

INTERPRETATION AND CONCLUSIONS

These results confirm the interindividual variation in HPC mobilization among healthy subjects, with LT-BMC counts being the most reliable predictor, expressing the behavior of the immature progenitors and their relationship with the microenvironment.