Possible role of minor h antigens in the persistence of donor chimerism after stem cell transplantation; relevance for sustained leukemia remission.

Persistent complete donor chimerism is an important clinical indicator for remissions of hematological malignancies after HLA-matched allogeneic stem cell transplantation (SCT). However, the mechanisms mediating the persistence of complete donor chimerism are poorly understood. The frequent coincidence of complete donor chimerism with graft-versus-leukemia effects and graft-versus-host disease suggests that immune responses against minor histocompatibility antigens (mHags) are playing an important role in suppressing the host hematopoiesis after allogeneic SCT.

Cryopreservation of cord blood CD34+ cells before or after thrombopoietin expansion differentially affects early platelet recovery in NOD SCID mice.

Background: Expansion of human cord blood (CB) CD34+ cells with thrombopoietin (TPO) can accelerate delayed platelet (PLT) recovery after transplantation into immunodeficient mice. Clinical implementation, however, will depend on practical and effective protocols. The best timing of TPO expansion in relation to cryopreservation in this respect is unknown.

No Synergistic Effect of Cotransplantation of MSC and Ex Vivo TPO-Expanded CD34(+) Cord Blood Cells on Platelet Recovery and Bone Marrow Engraftment in NOD SCID Mice.

After cord blood (CB) transplantation, early platelet recovery in immune-deficient mice is obtained by expansion of CB CD34(+) cells with thrombopoietin (TPO) as single growth factor. Moreover, improvement of hematopoietic engraftment has been shown by cotransplantation of mesenchymal stem cells (MSC). We investigated whether a combination of both approaches would further enhance the outcome of CB transplantation in NOD SCID mice.

Thrombopoietin treatment of one graft in a double cord blood transplant provides early platelet recovery while contributing to long-term engraftment in NSG mice.

Human cord blood (CB) hematopoietic stem cell (HSC) transplants demonstrate delayed early neutrophil and platelet recovery and delayed longer term immune reconstitution compared to bone marrow and mobilized peripheral blood transplants. Despite advances in enhancing early neutrophil engraftment, platelet recovery after CB transplantation is not significantly altered when compared to contemporaneous controls. Recent studies have identified a platelet-biased murine HSC subset, maintained by thrombopoietin (TPO), which has enhanced capacity for short- and long-term platelet reconstitution, can self-renew, and can give rise to myeloid- and lymphoid-biased HSCs.

Exploring the use of expanded erythroid cells for autologous transfusion for anemia of prematurity.

Background: Autologous cord blood (CB) red blood cells (RBCs) can partly substitute transfusion needs in premature infants suffering from anemia. To explore whether expanded CB cells could provide additional autologous cells suitable for transfusion, we set up a simple one-step protocol to expand premature CB cells.

Study Design And Methods: CB buffy coat cells and isolated CD34-positive (CD34(pos) ) cells from premature and full-term CB and adult blood were tested with several combinations of growth factors while omitting xenogeneic proteins from the culture medium.

Double umbilical cord blood transplantation: a study of early engraftment kinetics in leukocyte subsets using HLA-specific monoclonal antibodies.

Single cord blood unit (CBU) predominance is usually established within the first month after double umbilical cord blood transplantation (UCBT). However, the kinetics of engraftment of the different leukocyte subsets and the mechanism of graft predominance is largely unknown. To investigate whether a differential engraftment might reveal a specific subset that could play a key role in the mechanism of graft predominance, we studied early engraftment kinetics of different leukocyte subpopulations by flow cytometry using human monoclonal antigen-specific human leukocyte antigen antibodies, directed against mismatched human leukocyte antigen-A or -B antigens between recipient and CBUs.

Validation of human monoclonal HLA Class I antibodies to evaluate the kinetics of donor chimerism in different cell subsets after double-cord-blood transplantation in the NOD/SCID model.

Background: Double-cord-blood transplantation (DCBT) in patients is typically accompanied by predominance of a single unit. The causative mechanism, however, is unknown. Identifying the dynamics of mixed donor chimerism in general and in specific subpopulations may help to resolve this question.

Functional characterization of TPO-expanded CD34+ cord blood cells identifies CD34- CD61- cells as platelet-producing cells early after transplantation in NOD/SCID mice and rCD34+ cells as CAFC colony-forming cells.

Transplantation of thrombopoietin (TPO)-expanded cord blood CD34(+) cells accelerates human platelet recovery in NOD/SCID mice. It is unknown which subpopulations of the TPO-expanded cells mediate accelerated platelet recovery and bone marrow (BM) engraftment. In this study, the contribution of these subpopulations to human platelet appearance in the blood and BM engraftment was studied in NOD/SCID mice.

Gata1 expression driven by the alternative HS2 enhancer in the spleen rescues the hematopoietic failure induced by the hypomorphic Gata1low mutation.

Rigorously defined reconstitution assays developed in recent years have allowed recognition of the delicate relationship that exists between hematopoietic stem cells and their niches. This balance ensures that hematopoiesis occurs in the marrow under steady-state conditions. However, during development, recovery from hematopoietic stress and in myeloproliferative disorders, hematopoiesis occurs in extramedullary sites whose microenvironments are still poorly defined.

Photodynamic treatment with mono-phenyl-tri-(N-methyl-4-pyridyl)-porphyrin for pathogen inactivation in cord blood stem cell products.

Background: Hematopoietic stem cell transplants and culture of hematopoietic progenitor cells require pathogen-free conditions. The application of a method of pathogen inactivation in red blood cells using photodynamic treatment (PDT) was investigated for the decontamination of cord blood stem cell (CBSC) products.

Study Design And Methods: CBSC products, spiked with Gram-positive and Gram-negative bacteria, were treated with PDT using mono-phenyl-tri-(N-methyl-4-pyridyl)-porphyrin (Tri-P(4)) and red light.

A sensitive quantitative single-platform flow cytometry protocol to measure human platelets in mouse peripheral blood.

Background: The NOD/SCID mouse is a widely used model for human cord blood (CB) transplantation. Engraftment is generally estimated with semiquantitative methods, measuring the percentage of human cells among mouse cells. To compare protocols aiming to improve hematopoietic recovery, quantitative methods to enumerate human cells would be preferred.

Ex vivo culture of human CD34+ cord blood cells with thrombopoietin (TPO) accelerates platelet engraftment in a NOD/SCID mouse model.

Objectives: Hematopoietic recovery, in particular platelet reconstitution, can be severely delayed after transplantation with cord blood (CB) stem cells (SC). Expansion of CB SC may be one way to improve the recovery, but there is concern that ex vivo expansion compromises the repopulating ability of SC.

Methods: We used a short-term expansion protocol with TPO as single growth factor.

Reduced growth, increased vascular area, and reduced response to cisplatin in CD13-overexpressing human ovarian cancer xenografts.

Purpose: Expression of aminopeptidase N/CD13 can be detected in several solid tumor types. Thus far, the role of CD13 in ovarian cancer has not been studied. We have investigated the expression pattern and biological function of CD13 in ovarian cancer.

Aminopeptidase inhibitor bestatin stimulates microvascular endothelial cell invasion in a fibrin matrix.

The aminopeptidase inhibitor bestatin has been shown to have anti-angiogenic effects in a number of model systems. These effects are thought to result from inhibition of CD13 activity. Because tumor angiogenesis can evolve in a fibrin-rich stroma matrix we have studied for the first time the effects of bestatin on microvascular endothelial capillary-like tube formation in a fibrin matrix.

Soluble aminopeptidase N/CD13 in malignant and nonmalignant effusions and intratumoral fluid.

Purpose: On the basis of the finding of marked overexpression in angiogenic microvessels, aminopeptidase N/CD13 has recently been suggested to play a prominent role in tumor angiogenesis. A soluble form of CD13 (sCD13) is present in human plasma, but its role in cancer has not been addressed. We hypothesized that sCD13 would be shed by tumor cells and/or endothelial cells lining tumor vessels, giving high levels of sCD13 in intratumoral fluid (TF) deposits and in malignant effusions.

A doxorubicin-CNGRC-peptide conjugate with prodrug properties.

There is increasing interest in the exploitation of molecular addresses for the targeting of tumor imaging or therapeutic agents. A recent study demonstrated anticancer activity in human xenografts of doxorubicin (DOX)-peptide conjugates targeted to the tumor vascular endothelium, among them DOX coupled to the cyclic pentapeptide CNGRC [Science 279 (1998) 377]. In order to learn more about the mechanism of action of this type of DOX-peptide conjugates, we have studied the interaction of DOX-CNGRC with primary human umbilical cord vein endothelial cells (HUVEC) and tumor cells under defined in vitro conditions.