Esmail D. Zanjani - US grants

The major objectives of this research proposal are 1) to study mechanisms that control erythropoietin (Ep) production and erythropoiesis in the mammalian fetus, 2) to investigate factors that favor hepatic rather than renal Ep formation, 3) to evaluate the kinetics (delay or acceleration) of the liver-kidney switch of Ep formation, and 4) to assess the in vivo effects of various agents and conditions on the type (fetal or adult) and relative concentration of hemoglobin in different hematopoietic organs during fetal growth and development. These studies will be performed in fetal, newborn and adult sheep before and after treatment with androgens and thyroid hormones; following induction of chronic anemia and polycythemia, chronic partial hepatectomy and/or bilateral nephrectomy, and thyroid gland ablation. In addition, the influence of maternal hypoxia on erythropoiesis in normal and polycythemic fetuses will be investigated.

The major objectives of this research proposal are 1) to study mechanisms that control erythropoietin (Ep) production and erythropoiesis in the mammalian fetus, 2) to investigate factors that favor hepatic rather than renal Ep formation, 3) to evaluate the kinetics (delay or acceleration) of the liver-kidney switch of Ep formation, and 4) to assess the in vivo effects of various agents and conditions on the type (fetal or adult) and relative concentration of hemoglobin in different hematopoietic organs during fetal growth and development. These studies will be performed in fetal, newborn and adult sheep before and after treatment with androgens and thyroid hormones; following induction of chronic anemia and polycythemia, chronic partial hepatectomy and/or bilateral nephrectomy, and thyroid gland ablation. In addition, the influence of maternal hypoxia on erythropoiesis in normal and polycythemic fetuses will be investigated.

The conceptual basis of bone marrow transplantation (BMT) rests on reconstitution of hemopoiesis after depletion of marrow from defective or undesirable stem cells. A few hundred stem cells (HSC) could be sufficient for this purpose. This requires purification/enrichment of HSC. To achieve this end a reliable assay system for measuring the in vivo repopulating ability of the human HSC is needed. Available in vitro techniques for assaying human HSC, reflect the cells differentiation potential and not its repopulating ability. Our preliminary work, using transplantation in preimmune fetal sheep suggests that this system may offer a suitable vehicle for assaying human HSC in a xenograft assay. The proposed studies use the pre-immune fetal sheep as a model to: 1) Establish an assay system for human hematopoietic stem cells (HSC) that permits the qualitative and quantitative evaluation of human HSC activity in vivo. Available in vitro clonogenic assays for hematopoietic progenitors can explore the developmental potential of human HSC, but not their in vivo reconstitutive ability. 2) Identify the in vitro clonogenic assay(s) that can best predict the in vivo reconstituting ability of human HSC by comparing the in vitro clonogenic potential of a source of HSC with its in vivo engraftment activity. 3) Assess the in vitro systems for long term culture of bone marrow (LTBMC), and the available enrichment schemes for their ability to provide expanded/purified populations of HSC capable of long-term hematopoietic reconstitution in vivo. 4) Increase the efficiency of HSC engraftment by a) the use of hematopoietic growth factors IL-3, GM-CSF, and IL-6, and b) the experimental modulation of the "homing" mechanism by the use of synthetic neoglycoproteins of defined specificities, monoclonal antibodies to "homing" proteins, as well as, IL-3, GM-CSF, and IL-6. It is hoped that these studies will clarify the mechanism(s) regulating HSC activity in vivo, and narrow the gap between fundamental knowledge of HSC and its application in clinical bone marrow transplantation.

Gene therapy involving the transfer of a functioning exogenous gene into appropriate somatic cells (e.g. hematopoietic stem cells - HSC) of an organism offers a precise means of treating a number of genetic diseases. Most genetic disorders in human can now be diagnosed early in gestation. In addition, procedures for directly accessing the fetus during much of the intrauterine life have been well established. It is thus possible to treat these patients quite early in gestation before the disease process has had a chance to clinically compromise the patient. The insertion of genes into hematopoietic cells has been greatly facilitated by the use of retroviral vectors. Our preliminary studies using a in utero retroviral gene transfer / HSC transplantation protocol in sheep and monkey fetuses indicate that this approach may offer a suitable procedure for applying somatic cell gene therapy before birth. The long term objective of the proposed studies is to investigate the possibility of using an in utero approach to somatic cell gene therapy that will result in the long term transfer/expression of a normal functioning gene in large animals. Specifically, we plan to use the sheep as a large animal model to: 1) Delineate the conditions the will allow the most efficient transfer of a retroviral-mediated exogenous gene into circulating hematopoietic stem cells (HSC) of fetal sheep by examining the effects of hematopoietic growth factors, time and sequence of incubation, multiplicity of infection, etc. on HSC transduction in vitro and in vivo; 2) Evaluate the safety and efficacy of multiple gene transfer procedures in sheep fetuses by comparing the efficiency of gene transfer/expression in newborn lambs that were given either 1, 2 or 3 gene therapy treatments before birth; and 3) Determine whether efficient transfer of the NeoR gene into hematopoietic and other cells can be achieved by the direct administration of the recombinant retrovirus to fetal sheep, by assessing the transfer/expression of the NeoR in marrow, blood, liver, lungs, thymus, etc. of the fetus and the newborn at intervals following the administration of the retroviral vector to sheep fetuses intraperitoneally or via the yolk sac. It is hoped that with the techniques developed here it will become possible to treat genetic diseases including those involving hemoglobin synthesis in humans early during development.

DESCRIPTION (provided by applicant): In utero stem cell transplantation (IUSCT) offers a potential therapeutic option for the treatment of a wide variety of congenital diseases that can be diagnosed early in gestation. Until recently this approach has been limited to hematopoietic reconstitution using hematopoietic stem cells (HSC). However, the identification and functional characterization of other stem cells such as neuronal stem cells or mesenchymal stem cells and the findings suggestive of trans-differentiation events or reversibility of stem cell commitment brought on by environmental influences among others raise the possibility of their use in prenatal transplantation to correct non-hematopoietic cellular/organ abnormalities. The dramatic increase in the frequency of prenatal diagnosis of a variety of human congenital abnormalities creates the clinical opportunities for IUSCT. This and the highly receptive environment of the developing fetus provide the main rationale for in utero stem cell therapy. Yet, despite promising experimental results in normal and disease animal models, the clinical experience with IUSCT thus far has been disappointing with the only clear successes being achieved in X-SCID patients where a selective advantage for donor T-cell development exists. In all other cases where host HSC compete favorably with donor HSC, donor cell engraftment has been too low to benefit the patient. The studies proposed here are designed to make IUSCT broadly applicable to disease entities in which normal host hematopoietic competition is present by the creation of a "homing" environment more "friendly" to the donor HSC, and by the use of sources of HSC that show a greater propensity to engraft the fetus. To achieve this, we propose to 1) establish the parameters that permit increased donor HSC engraftment/activity by co-transplantation of autologous stroma/MSC in the human/sheep xenograft model, 2) develop an allogeneic sheep-to-sheep IUSCT model in sheep using sheep cord blood and autologous stroma, and 3) determine whether the improved donor cell engraftment/activity can beneficially influence the disease process in fetal sheep with ceroid lipofuscinosis (Batten's disease). It is hoped that the proposed studies will help devise IUSCT strategies for the treatment of a variety of congenital disorders that will result in the engraftment/expression of donor HSC at therapeutic levels without cytoablation and without GVHD.

DESCRIPTION (Adapted from the applicant's abstract) Hematopoietic stem cells (HSC) are characterized by their ability to undergo self-renewal and multi-lineage differentiation. A variety of in vitro assays have been used to assess and predict the in vivo potential of HSC from different human sources for these characteristics. It is understood, however, that the in vivo long-term proliferative potential of human HSC is generally not fully addressed by in vitro assays. The investigators have developed a large animal model of human hematopoiesis in sheep which permits the engraftment and multilineage differentiation of human HSC following transplantation in utero. In this model, they have reported (a) the long-term engraftment of human fetal and purified adult HSC, (b) the development of graft versus host disease (GVHD) with light density mononuclear cells (LMNC) from human post-natal sources, and (c) the induction of donor (human)-specific tolerance in chimeric lambs. The overall aims of the studies proposed here are to use the preimmune fetal/tolerized sheep as a model to investigate and compare the in vivo potential of native and ex- vivo expanded HSC from human cord blood, bone marrow, and peripheral blood with regards to (1) the long-term (stable) engraftment, self-renewal, and differentiation in non- myeloablated and myeloablated hosts, and (2) the development of GVHD in this human/sheep xenograft model. From each source the investigators plan to compare the in vivo activity of HSC present in light density mononuclear cells (LMNC), T-depleted LMNC, CD34+-enriched, and highly purified, sorted fractions under "normal" and cytokine-induced "stressed" conditions. It is hoped that these studies will help identify the source(s) and HSC preparation(s) likely to provide long- term in vivo reconstitution and with low risks of GVHD and HSC exhaustion.

DESCRIPTION; This will be held in Portland, Oregon in the Summer of 1998. The objectives are: (1) to assemble speakers and participants consisting of basic scientists and clinicians from diverse backgrounds and interests, including stem cell biology, gene therapy of hematopoietic stem cells, genetic diseases, immunology, transplantation biology, obstetrics, fetal surgery, neonatology and medical ethicists; (2) to present and discuss the latest finding on in utero hematopoietic stem cell transplantation and gene therapy; (3) to identify and fully discuss controversial issues related to clinical application of this technology; (4) to foster interdisciplinary collaborations; and (5) to identify areas in need of additional basic and preclinical research as a prerequisite for continued clinical progress. Major topics to be discussed include (a) stem cell biology and transplantation; (b) stem cell gene therapy; (c) animal studies of in utero stem cell transplantation; (d) GVHD and induction of tolerance; (e) in utero gene transfer in animal models; (f) clinical experiences with gene therapy and in utero stem cell transplantation; and (g) medical ethics of in utero stem cell transplantation and gene therapy.

Although human hematopoietic stem cells (HSC) can be characterized by their activity in vitro and by their phenotypic expression of one or more antigens, they are most rigorously defined by their ability to reconstitute the hematopoietic system for the lifetime of the recipient under normal and (occasional) stress conditions. Because ethical and practical considerations prevent the testing of limiting numbers of human HSC in human recipients as has been successfully used for murine HSC, a number of surrogate assays using immunodeficient mice or preimmune fetal sheep have been developed to assess the in vivo engraftment and differentiation potentials of human HSC subsets. Of these, the fetal sheep model offers certain unique opportunities such as long-term observation, competitive engraftment, serial transfers, and provision of an early hematopoietic environment suitable for assessing the engraftment potential of putative HSC from embryonic sources, that are not easily achievable in the existing xenogeneic mouse assays. These attributes and the ability to achieve significant engraftment with relatively small numbers of human HSC from fetal, cord blood and adult sources have been used to advantage to assess the in vivo potential of human HSC subsets on a cell-per-cell basis. However, sheep require approved animal facilities not easily available in a majority of institutions. We have made the model available to a number of investigators often without cost. These collaborations have helped fine tune the model and establish its biological relevance as an assay for human HSC. The purpose of this application is to secure long-term funding for this large animal model by investigating 1) the effect of "humanizing" the model by pre- transplantation of human stromal/MSC cells on the engraftment and differentiation efficiency of human HSC; 2) human stem cell plasticity by studying the hematopoietic potential of human neuronal stem cells; and 3) whether mobilized human blood HSC differ from marrow HSC with regard to their engraftment potential on a cell-per-cell basis and whether any deficiency may be overcome by the use of large numbers of blood HSC. We also plan to determine whether the model can serve to detect HSC activity during human embryonic and early fetal development. We hope that these efforts will improve the availability and reliability of the sheep model, and develop new information with regard to the environmental control of HSC engraftment and/or differentiation in this model.

embryo /fetus surgery; model design /development; hematopoietic stem cells; biological models; hematopoiesis; sheep; bone marrow transplantation; tissue donors; graft versus host disease; metabolism disorder; disease /disorder prevention /control; blood disorder; cytokine; cell population study; T cell receptor; receptor binding; monoclonal antibody; karyotype; flow cytometry;

[unreadable] DESCRIPTION (provided by applicant): The goal of this project is to produce "humanized" livers in large animal models such as sheep and pigs that can serve as a reliable source of significant numbers of functional human hepatocytes. The isolated human hepatocytes and/or "humanized" livers can be used for drug toxicity studies as well as for possible clinical use in patients with liver failure. Transplantation of human bone marrow (BM) CD34+ cells from normal donors of diverse genetic background into pre-immune fetal sheep/pigs can be used to generate human liver cells for use in drug toxicity studies (the aim of the present application), and from specific patients to produce livers and/or cells autologous to the patient (future goal requiring proof-of-principle studies). Feasibility data is presented demonstrating that the transplantation of CD34+ cells from human BM, mobilized peripheral blood, and cord blood into this non-injury pre-immune fetal sheep model resulted in the robust formation of relatively large numbers of human liver cells that synthesize and secret human albumin into circulation. In this human/sheep xenograft model donor (human) hepatopoiesis persists long-term (> 2years) without apparent loss of number or function. In the phase I effort we propose to determine: 1) the optimal gestational age of the sheep fetus, and 2) the optimal concentration of human bone marrow CD34+ cells for obtaining the highest percentages of human hepatocytes. Phase II effort will focus on efficient isolation, characterization, and maintenance of human liver cells from the "humanized" liver. [unreadable] [unreadable]