Biomedical subjects

Yair Reisner

Publications and source records attributed to Yair Reisner.

32 records · Page 2Linked to original sources

PubMed2004

Engraftment of human early kidney precursors.

Kidney transplantation has been one of the major medical advances of the past 30 years; however, it is becoming increasingly apparent that the supply of organs is limited and will not improve with current medical practice. This review summarizes recent data whereby precursors of the adult kidney found in embryos and fetal tissue have been grafted into murine hosts to examine their feasibility as an alternative source for renal transplantation. When obtained at specific time points during human gestation, kidney precursors meet with specific demands; they grow tremendously, differentiate exclusively along the nephric lineage with no evidence of malignant transformation, become vascularised, to a larger extent, by host vessels, and produce urine in host animals. In addition, they exhibit decreased immunogenicity compared to adult counterparts. Organogenesis is best achieved when utilizing early undifferentiated progenitors rather than later-gestation kidneys. Nevertheless, in order for these transplants to be applicable for human transplantation, both a functional urinary anastomosis and derivation of blood supply sufficient to correct biochemical abnormalities remain to be established.

Animals↗

PubMed2004

Embryonic committed stem cells as a solution to kidney donor shortage.

The number of human kidney transplants has increased rapidly in recent years, but the need greatly exceeds organ availability. Induction of appropriate kidney differentiation and growth from stem or progenitor cell populations represents an attractive option to combat chronic kidney donor shortage. In an analogy to haematopoietic stem cells, which are much more efficient in giving rise to blood than to other cell types, if any at all, renal stem cells could afford an unlimited source for regenerating nephrons. While a single nephrogenic stem cell has not been characterised, indirect evidence suggests that a renal stem cell population is contained within the metanephric mesenchyme, which along with a branch of the Wolffian duct represents the direct precursor of the mature kidney. Human tissue fragments derived from these developing precursors can regenerate renal structures when grafted into mice. Moreover, recent data pinpoints a window of time in human and pig kidney development that may be optimal for transplantation into mature recipients. 'Window' transplants are defined by their remarkable ability to grow, differentiate and undergo vascularisation, achieving successful organogenesis of urine-producing miniature kidneys with no evidence of transdifferentiation into non-renal cell types, lack of tumourigenicity and reduced immunogenicity compared with adult counterparts. In contrast, 'non-window' transplants (earlier or later in gestation) can form teratomas or are more prone to immune rejection and are less suitable for organogenesis. Hopefully, the use of stage-specific early human and porcine kidney precursors to cultivate mature kidney cells in vivo, possibly in conjunction with other modalities of stem cell technology and tissue engineering, will prove valuable to sustain life in patients with failing kidneys.

Animals↗

PubMed2003

Anti-third-party veto CTLs overcome rejection of hematopoietic allografts: synergism with rapamycin and BM cell dose.

Several bone marrow cells and lymphocyte subpopulations, known as "veto cells," were shown to induce transplantation tolerance across major histocompatibility antigens. Some of the most potent veto cells are of T-cell origin, and in particular a very strong veto activity was documented for cytotoxic T-lymphocyte (CTL) lines or clones. However, these cells also possess marked graft-versus-host (GVH) reactivity. In the present study we evaluated a new approach to deplete CTLs of antihost clones by stimulating the donor T cells against third-party stimulators in the absence of exogenous interleukin 2 (IL-2). We demonstrate that such CTLs are depleted of GVH reactivity while maintaining marked veto activity in vitro. Furthermore, marked synergism was exhibited between the veto CTLs and rapamycin when tested in a murine model, which measures T-cell-mediated bone marrow allograft rejection, or in sublethally irradiated allogeneic hosts. Our results suggest that engraftment of early progenitors could be enhanced by using host-nonreactive anti-third-party CTLs, in conjunction with nonmyeloablative rapamycin-based conditioning protocols, thereby significantly reducing the toxicity of allogeneic transplantation.

Animals↗

PubMed2003

Lupus manifestations in severe combined immunodeficient (SCID) mice and in human/mouse radiation chimeras.

The objective of this study was to develop a human lupus model. To this end we have established and compared two models: (1) severe combined immunodeficient (SCID) mice reconstituted with peripheral blood lymphocytes (PBL) of either systemic lupus erythematosus (SLE) patients or healthy controls and (2) lethally irradiated BALB/c mice radioprotected with bone marrow of SCID mice, to which human PBL were transferred (human/mouse chimera). Engraftment was successful in most (78.4%) recipient mice as determined by the levels of human IgG measured. In about 50% of either SCID mice or human/mouse chimeras that were successfully engrafted with PBL of SLE patients, significant anti-dsDNA autoantibodies, mostly of the IgG1 and IgG2 isotypes, were determined. Interestingly, in a significant number (84.5%) of recipients of PBL of the healthy controls, anti-dsDNA antibodies were observed as well, suggesting that PBL of at least some of the healthy controls have the potential to develop SLE-associated autoantibodies under the appropriate stimulatory conditions. Glomerular immune deposits (human IgG, mouse C3) were detected in 70-80% of SCID mice with human DNA specific antibodies and in a third of the human/mouse chimeras. Thus, SLE serology and glomerular pathology were reproducibly demonstrated in two models of human SLE. These models should allow the evaluation of potential therapies for the treatment of lupus patients.

Animals↗

PubMed2003

Hematopoietic stem cell transplantation across major genetic barriers: tolerance induction by megadose CD34 cells and other veto cells.

Studies in mice and humans demonstrate that transplantation of hematopoietic progenitors in numbers larger than commonly used ("megadose" transplants) overcomes major genetic barriers. In vitro studies suggest that veto cells, within the population of hematopoietic progenitors, facilitate this favorable outcome. Thus, when purified CD34(+) cells were added to bulk mixed-lymphocyte reactions (MLRs) they suppressed CTLs against the donor's stimulators, but not against stimulators from a third party. This tolerizing activity depends on cell contact and can be blocked by the caspase inhibitor BD-FMK, suggesting that the effector host T cells are deleted by apoptosis upon interaction with the CD34(+) cells. Early myeloid CD33(+) cells generated by short-term ex vivo expansion of CD34(+) cells also exhibit veto activity, and these cells can be grown in large numbers. Tolerance induction can be further enhanced by other veto cells. Perhaps the most potent veto cell is the CD8+ CTL. However, this cell is also associated with marked GVHD (graft-versus-host disease. GVHD can be separated from the veto activity by generating anti-third party CTLs under IL2 deprivation. Under such selective pressure only the stimulated clones which make IL2 can survive, while anti-host clones die. In vivo studies show that such anti-third party veto CTLs can be used safely for tolerance induction without GVHD.

Animals↗

PubMed2002

Human and porcine early kidney precursors as a new source for transplantation.

Kidney transplantation has been one of the major medical advances of the past 30 years. However, tissue availability remains a major obstacle. This can potentially be overcome by the use of undifferentiated or partially developed kidney precursor cells derived from early embryos and fetal tissue. Here, transplantation in mice reveals the earliest gestational time point at which kidney precursor cells, of both human and pig origin, differentiate into functional nephrons and not into other, non-renal professional cell types. Moreover, successful organogenesis is achieved when using the early kidney precursors, but not later-gestation kidneys. The formed, miniature kidneys are functional as evidenced by the dilute urine they produce. In addition, decreased immunogenicity of the transplants of early human and pig kidney precursors compared with adult kidney transplants is demonstrated in vivo. Our data pinpoint a window of human and pig kidney organogenesis that may be optimal for transplantation in humans.

Adult↗

PubMed2002

Tolerance induction by megadose hematopoietic progenitor cells: expansion of veto cells by short-term culture of purified human CD34(+) cells.

Stem cell-dose escalation is one way to overcome immune rejection of incompatible stem cells. However, the number of hematopoietic precursors required for overcoming the immune barrier in recipients pretreated with sublethal regimens cannot be attained with the state-of-the-art technology for stem cell mobilization. This issue was addressed by the observation that cells within the human CD34(+) population are endowed with veto activity. In the current study, we demonstrated that it is possible to harvest about 28- to 80-fold more veto cells on culturing of purified CD34(+) cells for 7 to 12 days with an early-acting cytokine mixture including Flt3-ligand, stem cell factor, and thrombopoietin. Analysis of the expanded cells with fluorescence-activated cell-sorter scanning revealed that the predominant phenotype of CD34(+)CD33(-) cells used at the initiation of the culture was replaced at the end of the culture by cells expressing early myeloid phenotypes such as CD34(+)CD33(+) and CD34(-)CD33(+). These maturation events were associated with a significant gain in veto activity as exemplified by the minimal ratio of veto to effector cells at which significant veto activity was detected. Thus, whereas purified unexpanded CD34(+) cells exhibited veto activity at a veto-to-effector cell ratio of 0.5, the expanded cells attained an equivalent activity at a ratio of 0.125. The availability of novel sources of veto cells such as those in this study might contribute to the realization of immunologic tolerance in "minitransplants," without any risk of graft-versus-host disease.

Antigens, CD↗

PubMed2002

T cells from newborn humans are fully capable of developing into cytotoxic T lymphocyte effector cells in adoptive hosts.

BACKGROUND: The finding of reduced incidence of graft-versus-host disease (GVHD) associated with cord blood transplantation, compared to unrelated allogeneic bone marrow, could be related to the lower number of T cells infused in the cord blood (CB) inoculum or it might represent an intrinsic property of CB T cells. We investigated the in vivo function of human cord blood mononuclear cells (CBMC) after their adoptive transfer into lethally irradiated BALB/c radioprotected with severe combined immunodeficiency (SCID) mouse bone marrow. METHODS: The ability of human CBMC to engraft and produce antigen-specific alloreactive cytotoxic T lymphocytes (CTLs) and antibodies was determined by FACS, 51Chromium-release assay, and ELISA. RESULTS: Recipients of human CBMC showed engraftment of high levels of both CD14+ and CD3+ cells. Human cells recovered from the peritoneal cavity of chimeric mice, 1 week after immunization with irradiated allogeneic cells, showed adult-level human CTL response against the immunizing cells, without further stimulation in vitro. In contrast, immunization with the tetanus (TT) antigen did not lead to the generation of anti-TT immunoglobulins (Ig) in the cord blood chimera. Furthermore, whereas the addition of purified adult T cells to the cord blood inoculum resulted in the enhancement of human Ig production of both IgG and IgM subclasses, it could not induce antigen-specific antibodies after immunization. CONCLUSION: This report demonstrates in mice for the first time the generation of classical human alloreactive CTLs, derived from cord blood cells. The alloreactivity exhibited by the cord blood mononuclear cells is not different from that displayed by cells originating from adult blood. Any reduction in the observed GVHD associated with cord blood transplants might therefore represent a quantitative difference in the total number of T cells infused.

Adoptive Transfer↗

PubMed2002

Transplants across human leukocyte antigen barriers.

Clinical experience with full haplotype-mismatched stem cell transplants has a 20-year history. Early results in leukemia patients were disappointing because of a high incidence of severe graft-versus-host disease (GvHD) in T-replete transplants or high rejection rates in T-cell-depleted transplants. The breakthrough came with introduction of a megadose T-cell-depleted progenitor cell transplant following a high-intensity conditioning regimen and the realization that donor natural killer (NK) cell alloreactivity also plays a role in facilitating engraftment and in preventing relapse. Treating end-stage patients inevitably confounded clinical outcome in early pilot studies. Today, high-risk acute leukemia patients are treated at less advanced stages of disease, receive a reasonably well-tolerated conditioning regimen, and benefit from advances in post-transplant immunological reconstitution. These factors have markedly reduced transplant-related mortality. Overall, event-free survival (EFS) and transplant-related mortality (TRM) compare favorably with reports from unrelated matched transplants. T-cell-depleted megadose stem cell transplant from a mismatched family member, who is immediately available, can now be offered as a viable option to candidates with high-risk acute leukemias.

HLA Antigens↗

PubMed2002

Human colon adenocarcinoma in the SCID/CB6 radiation chimera is susceptible to adoptive transfer of allogeneic human peripheral blood mononuclear cells.

The aim of this study was to develop a murine model of human colon carcinoma (hCC) and to ascertain the potential of cellular immunotherapy in this model. Fragments of hCC obtained at surgery from 6 patients were transplanted under the kidney capsule of lethally irradiated CB6 mice radioprotected with severe combined immunodeficient (SCID) mice bone marrow. Tumor xenografts conserved their malignant behavior in the new environment, invading the mouse kidney parenchyma and expanding into the peritoneal cavity and adjacent tissues. Their growth was typically exponential, and they expanded to dimensions that allowed their subsequent fragmentation and passage to further preconditioned mice. Human carcinoembryonic antigen (hCEA) was detected on the implanted tumor and at occasionally spontaneous lung metastases. Most significantly, high levels of this tumor marker were detected in the sera of tumor-bearing mice, providing a useful tool, which allowed long-term experiments, monitoring of tumor progression, and its response to some treatment modalities. For instance, complete resection of the transplanted tumors, by means of nephrectomy, resulted in the disappearance of hCEA from mice sera within 2 weeks. Similarly, adoptive transfer of allogeneic human peripheral blood mononuclear cells (PBMC) into the peritoneum of tumor-bearing mice, resulted in their rapid engraftment, infiltration of tumor mass, and a significant drop of hCEA levels in mice serum, accounting for inhibition of tumor growth. We suggest that this novel model of human colon carcinoma affords the opportunity for in vivo evaluation of different preclinical treatment modalities, particularly, those involving manipulation with immune effector cells.

Adenocarcinoma↗

PubMed2002

Engraftment and differentiation of human metanephroi into functional mature nephrons after transplantation into mice is accompanied by a profile of gene expression similar to normal human kidney development.

Metanephroi, the embryonic precursors of the adult kidney, can be induced in vivo to grow and develop. Despite their potential clinical utility for transplantation, the ability of human metanephroi to differentiate after transplantation into functional mature nephrons is mostly unknown. To address this, 70-d human metanephroi were transplanted into NOD/SCID mice; global gene expression patterns that underlie development of human metanephric transplants were analyzed and compared with normal human kidney development. In addition, functionality of the grafts was assessed by dimercaptosuccinic acid radioisotope scans at different times after transplantation. The results of hybridization to cDNA arrays when RNA was derived from normal human kidneys at 8, 12, 16, and 20 wk gestation demonstrated that a subset of 240 genes changed substantially with time. The induced genes can be classified as cell cycle regulators, transcription and growth factors, and signaling, transport, adhesion, and extracellular matrix molecules. Strikingly, clustering analysis of global gene expression at 2, 6, and 10 wk after metanephric transplantation revealed an expression profile that characterizes normal human kidney development. Moreover, maturation of the transplants was accompanied by an increased uptake of dimercaptosuccinic acid. Nevertheless, expression levels of specific genes were mostly found to be suppressed in the transplants compared with the normal kidneys. These data provide insights into human kidney development and support the possibility of the transplantability of human metanephroi. Understanding of the molecular regulation of the transplanted developing metanephroi might lead to the development of strategies aimed at increasing the levels of specific genes, nephron endowment, and graft function.

Animals↗

PubMedDate not supplied

Crossing the HLA barriers.

Studies in mice and humans demonstrate that transplantation of hematopoietic progenitors in numbers larger than commonly used ("megadose" transplants) overcomes major genetic barriers. In vitro studies suggest that veto cells, within the population of hematopoietic progenitors, facilitate this favorable outcome. Thus, when purified CD34+ cells were added to bulk mixed-lymphocyte reactions (MLRs), they suppressed CTLs against donor's stimulators but not against stimulators from a third party. This tolerizing activity depends on cell contact and can be blocked by the caspase inhibitor BD-FMK, suggesting that the effector host T cells are deleted by apoptosis upon interaction with the CD34+ cells. Early myeloid CD33+ cells generated by short-term ex vivo expansion of CD34+ cells also exhibit veto activity, and these cells can be grown in large numbers. Tolerance induction can be further enhanced by other veto cells. Perhaps the most potent veto cell is the CD8+ CTL. However, this cell is also associated with marked graft-versus-host disease (GVHD). GVHD can be separated from the veto activity by generating anti-third party CTLs under IL2 deprivation. Under such selective pressure, only the stimulated clones which make IL2 can survive, while anti-host clones die. In vivo studies show that such anti-third party veto CTLs can be used safely for tolerance induction without GVHD.

Animals↗

PubMedDate not supplied

Fourth International Workshop on Haploidentical Transplants, Naples, Italy, July 8-10, 2004.

Many patients with high-risk hematological malignancies or with incurable inborn errors do not have an HLA-matched sibling and cannot find an HLA-matched donor for an allogeneic hematopoietic stem cell transplantation (SCT). Transplantation strategies using mismatched haploidentical family donors have been an important development. Although the procedure has saved patients from certain death, it is still beset by major problems like life-threatening infections--due to profound immunodeficiency following T-cell depletion and to disease relapse. At every International Workshop on Haploidentical Transplants, new data are presented, showing how scientists are attempting to improve the outcomes of mismatched transplants while reducing the severity of complications.The fourth Workshop continues in this tradition of presenting ground-breaking research. It opened with presentations of the current results with unrelated volunteer and umbilical cord blood transplants and proceeded to a session with the results of haploidentical transplants in the world with series of patients with high-risk acute leukemia, ranging in number from well over 100 in Perugia, Italy, and 80 in Haifa, Israel, to smaller groups in Europe and the United States. The session on graft engineering presented the latest results in the search for the optimal graft. The graft-vs.-leukemia effect in the haploidentical transplant was discussed in depth. Subsequently, attention focussed on one of the major problems in haploidentical transplant, that is, the delay in immunological recovery. The Workshop closed with presentations on tolerance induction that was followed by the results of ongoing registration studies being performed by the Italian GIMEMA group and the European Bone Marrow Transplant group.

Cord Blood Stem Cell Transplantation↗

PubMedDate not supplied

Hematopoietic stem cell transplantation from alternative sources in adults with high-risk acute leukemia.

Since 75% of patients with high-risk acute leukemia do not have a human leukocyte antigen (HLA)-identical sibling, alternative sources for hematopoietic stem cell transplantation (HSCT) are matched unrelated donors (MUD), unrelated umbilical cord blood (UD-UCB) and one HLA haplotype mismatched family members (haploidentical). The chance of finding a suitable donor in the international voluntary donor registries is limited by frequency of the HLA phenotype and the time required to identify the right donor from a potential panel, to establish eligibility and to harvest the cells. In adult MUD recipients, event-free survival ranges up to 50% and refers only to patients who undergo transplant, without taking into account those who do not find a donor. Umbilical cord blood offers the advantages of easy procurement, the absence of risks to donors, the reduced risk of transmitting infections, immediate availability of cryopreserved samples and acceptance of mismatches at two of the six antigens. Although UD-UCB transplantation is a viable option for children, it is seldom considered for adults. The great divergency between body weight and the number of hematopoietic cells in a standard cord blood unit, particularly if associated with a two-antigen mismatch, increases the risk of graft failure and delays hematopoietic reconstitution. Work on full-haplotype mismatched transplants has been proceeding for over 20 years. Originally, outcome in leukemia patients was disappointing because of high incidence of severe graft-vs.-host disease in T-replete transplants and high rejection rates in T-cell-depleted transplants. The breakthrough came with the use of a megadose of T-cell-depleted progenitor cells after a high-intensity conditioning regimen. Treating end-stage patients inevitably confounded clinical outcome in the early pilot studies. Today, high-risk acute leukemia patients are treated at less advanced stages of disease, receive a reasonably well tolerated conditioning regimen, and benefit from advances in post-transplant immunological reconstitution. All these factors contribute to markedly reduce transplant-related mortality. Overall, event-free survival and transplant-related mortality compare favorably with reports from unrelated matched transplants. T-cell-depleted megadose stem cell transplant from a mismatched family member, who is immediately available, can be offered as a viable option to candidates with high-risk acute leukemias.

Acute Disease↗