Increasing progress has been made in the understanding of the biology of mast cells. The precursors of mast cells leave the bone marrow in a non-differentiated form as CD34+ cells. The presence of mast cells growth and differentiation factors controls in tissues maturation of different mast cells phenotypes. The main factors are the mast cell growth factor SCF (stem cell factor), NGF (Nerve Growth Factor), and IL-3 (Interleukin-3). The potential role of each of these factors in the airways is discussed. An altered production of these growth factors in the airways of asthmatic patients might be the cause of the presence of an increased number of mast cells and of phenotypic modifications in the bronchi of these patients.

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of a stem cell, involving myeloid, erythroid, megacaryocyte, lymphoid B-cells and "natural killer" cells. The hallmark of CML is the Philadelphia (Ph) chromosome which is a shortened chromosome 22 (22q-) resulting from a reciprocal translocation involving chromosome 9 and chromosome 22, designed t (9;22) (q34;q11). This translocation juxtaposes parts of two genes; ABL on chromosome 9 and BCR (breakpoint cluster region) on chromosome 22. Transcription of the BCR/ABL fusion gene results in an hybrid mRNA that is translated into a 210 kDa or 190 kDa protein, depending on the location of the breakpoint in the bcr region. This protein plays a key role in CML: its tyrosine-kinase activity, that differs from the normal ABL product, may be involved in leukemic cell growth. Nonetheless, the loss of the negative cell growth regulation by c-ABL, or BCR/ABL fusion protein interaction with other cellular genes (such as RAS or c-MYC) could also be involved in CML pathophysiology. A better understanding of the molecular mecanisms of CML could lead to specific treatment, such as tyrosine-kinase inhibitors, synthetic oligodeoxynucleotides, or site-specific DNA-binding proteins designed against BCR/ABL oncogenic fusion sequence.

Formerly an exceptional treatment, transplantation of haematopoietic stem cells from an HLA (major histocompatibility complex) identical sibling donor is now an effective treatment of acute leukaemia, with well established indications. It still entails the drawback of severe toxicity, but progress has been made in the last 15 years, particularly with regard to improved prevention and treatment of host-versus-graft disease and severe cytomegalovirus infection. Given the improvement in registries of volunteer donors and the reliability of HLA typing using molecular biology, in some cases transplantation can be made using unrelated donors. Autologous transplantation of haematopoietic stem cells entails less toxicity. On the other hand, the autologous transplanted patient does not benefit from the "graft versus leukaemia" reaction observed after an allogeneic graft, and relapses are thus much more common than after allografting. The indications of autologous transplantation are still debated and are the subject of numerous prospective studies.

The skin may be considered as well as a target and an iniator of self immune reactions. Two to 5% of the epidermal cells are Langerhans cells (LC) which are the only cells to specifically take, process and present the antigens to lymphocytes in order to induce an immune response. Such an ability and location of these cells enhance their role in antigenic stimulations and immuno-allergic reactions. TNF alpha was showed to potentiate the effect of GM-CSF for the generation of LC from their CD34+ precursors. Originated from the bone marrow, the LC colonize the epithelia where they act as antigen presenting cells by taking, processing antigens, and migrating to lymph nodes where they sensitize T cells. In vitro incubation of LC mimics their phenotypic, morphologic and functional maturation (enhanced accessory function) while they are migrating in vivo to lymph nodes where they are called interdigitating cells. Animal models might clarify such an hypothesis. Mechanisms leading to the LC immigration or the emigration from epithelia in order to play their immune functions remain obscure. Although LC are purified with difficulty and no immortalized human cell lines exist, these cells are still an ideal APC dendritic cell model. They will certainly be considered, in the next future, as the pivotal role of vaccinal strategy.

Dendritic Cells (DC) are professional antigen presenting cells, necessary during the initiation of immune responses. The study of the role of DC in the establishment of this response has long been tempered by the difficulties to purify DC in sufficient numbers. In vitro generation of DC, from CD34+ hematopoietic progenitors in human and mice, should permit to clarify the relationships between the different DC types isolated in vivo and their roles. GM-CSF has been described to play a key role in the propagation of DC. In human, in association with TNF alpha, it allows the generation of DC from CD34+ progenitors. Those in vitro generated DC are capable of receptor mediated endocytosis and can present soluble antigen to specific T cell clones and activate naive T cells. During activation of naive T cells CD86 (on DC)--CD28 (on T lymphocyte) interaction seems to play a critical role. Interestingly, DC express a functional CD40, which triggering upregulates expression of CD80 and CD86 and induces cytokine production, indicating a reciprocal talk between DC and T cells during the course of antigen presentation. Finally, in vitro generated DC interact directly with B cells, activated through their CD40 antigen, leading to enhanced growth, differentiation (IgM production) and preferential isotype switch towards IgA. Thus, in the extrafollicular area of secondary lymphoid organs, in addition to prime naive T cells, DC might also directly provide costimulatory signals involved during the initiation of primary B cell responses.

Development of megakaryocyte (MK) from CD34+ cord blood (CB) cells in both plasma clot culture and liquid culture was significantly inhibited by human platelet factor 4 (PF4) and human transforming growth factor beta 1 (TGF beta 1). Inhibition of cell growth by PF4 was reversible judging from the fact that the CD34+ cells preincubated with PF4 could regenerate colonies after washing and replating into the cultures. By contrast, TGF beta 1-pretreated CD34+ cells gave rise to few colonies following replating. Moreover, incubation of CD34+ cells with PF4 in liquid culture caused an increase in the number of both stem cell factor (SCF)-binding cells and CD34 antigen-bearing cells, and exhibited greater capacity to form MK colonies than control after the treatment of 5-FU. In vivo in mice, twice injections of PF4 at 40 micrograms/kg resulted in a significant increase in the number of colony-forming cells with high proliferative potential (HPP-CFC) and colony-forming unit-megakaryocyte (CFU-MK) in bone marrow. In exponentially growing human erythroleukemia cells (HEL), the addition of PF4 prolonged cell cycle progression and therefore resulted in an increased cell population in S phase, as determined by flow cytometric analysis. Different from PF4, TGF beta 1 blocked more cells in G1 phase. These results demonstrate that PF4 and TGF beta 1 inhibit MK development from CD34+ CB cells by different mechanisms and suggest that PF4, unlike TGF beta 1, exerts its inhibitory effect on cell growth in a reversible and S phase-specific manner by which it protects stem cells and MK progenitor cells from 5-FU cytotoxicity.

This paper describes the adaptation of the MTT assay to hypoxic conditions in order to test the in vitro effect of piracetam on hypoxic cells and particularly on the radiosensitivity of hypoxic cells since this drug has shown clinical effect on acute and chronic hypoxia. The V79 cell line was selected by reference to preliminary hypoxic experiments using clonogenic assay and euoxic experiments using clonogenic and MTT assays. Cell growth and survival in our hypoxic conditions were assessed using MTT assay with an enclosure and special 48-well plates both made of glass. Growth curves on glass versus reference polystyrene plates were comparable and confirm the validity of using special glass plates. Growth curves on glass plates after 1-hour exposure to nitrogen versus air were comparable, so there is no bias effect due to gas composition. Survival curves using MTT versus reference clonogenic assay were comparable after radiation exposure in eu- and hypoxic conditions, and confirm the validity of our original technique for creating hypoxia. The Oxygen Enhancement Ratio was of about 3 for 1-hour hypoxic exposure. Piracetam gave no cytotoxic effect up to 10 mM of piracetam. Growth curves after continuous drug exposure and 1-hour euoxic versus hypoxic exposure gave no cytotoxic effect up to 10 mM of piracetam. Survival curves after continuous drug exposure to 10 mM of piracetam gave no significant effect on the radiosensitivity of hypoxic V79 cells using MTT or clonogenic assay. However, this does not preclude a potential in vivo effect of piracetam on the radiosensitivity owing to its action on microcirculation and its rheologic properties. The adaptation of the MTT assay to hypoxic irradiation conditions yields the easy screening of radiosensitizing drugs: shorter incubation, semi-automatic method and simultaneous analysis with different serial concentrations thanks to the special 48-well glass plates.

High dose chemotherapy with autologous blood stem cell rescue becomes widely used for patients with hematologic malignancies and solid tumors. Recently, it has been demonstrated that stem cells characterized by the CD34 antigenic marker could be positively selected using an anti CD34 monoclonal antibody and an avidin biotin immunoabsorption device. We report our experience of twelve selections and ten grafts. A CD34+ cells enrichment of 1.9 log (purity: 72%) and a CFU-GM cells concentration of 1.6 log have been obtained. In ten transplanted patients, the hematological recovery was similar to that obtained with non selected blood stem cells. The CD34+ cells purification allows mini graft infusion and purge of residual tumor cells implicated in relapse after autologous stem cells transplantation.

Eighty-four patients with locally advanced, non metastatic squamous cell carcinoma of head and neck or esophagus, were included in a multicentric double-blind randomized trial, comparing goralatide (12.5 or 62.5 micrograms/kg/day, d1-d4) to placebo, associated with carboplatin (400 mg/m2, d1) and 5-fluorouracile (1 g/m2/d continuous IV over 96 hours). Haematological toxicity was analysed on 221 cycles of chemotherapy. All but one patient were evaluable because of early death without haematological toxicity. No significant difference was observed for mean nadir of leukocytes, granulocytes, platelets counts and hemoglobin level. Duration of haematological toxicity was no significantly different for the two groups of patients. Anemia and lymphopenia were more frequent in the goralatide treated patients. Clinical and biological tolerability of goralatide was excellent.

The aim of this study was to compare anxiety, pain and discomfort of cancer patients submitted to two procedures of hematopoietic stem cells collection: peripheral blood stem cells collection (PBSCC) or bone marrow collection (BMC). Patients, randomized (July 1993-February 1994), in view of autograft, to receive the first procedure or the second one, completed self-administered questionnaires before, during and after the procedure. Anxiety was evaluated by State-Trait Anxiety Inventory. Pain was assessed using visual analogical scale (VAS) and McGill Pain questionnaire. Before the procedure, in comparison with PBSCC patients (n = 40), BMC patients (n = 25) experienced more State-anxiety due to the procedure approach (p < 0.01) and more trouble or inconvenience for having to come and stay at the hospital (p < 0.0001). During the procedure, pain related to BMC, as assessed by VAS, is significatively higher than pain induced by PBSCC, whichever the access used (p < 0.001). The McGill total score is twice as high for BMC patients than for patients submitted to PBSCC with femoral catheter (n = 19). The latter patients significatively reported more pain than patients without femoral catheter (n = 21). At the discharge from hospital, 32% of BMC patients judged the procedure quite difficult vs 5% of PBSCC patients (p < 0.05). These results explain a higher acceptability of the peripheral blood stem cells collection.

Paclitaxel (Taxol) and docetaxel (Taxotere) are the first representatives of a new class of antitumor compounds. These two taxoids are clinically active against breast, ovarian and lung cancers. Taxoids are highly complex diterpenoids form natural origin. Preclinical and clinical developments have been made possible after a long and sustained chemical effort: paclitaxel is extracted from the barks of the Pacific yew tree Taxus brevifolia whereas docetaxel is prepared by hemisynthesis starting from 10-deacetyl-baccatin III, an inactive precursor found in the needles of the European yew tree Taxus baccata. These two drugs are active in various in vitro and in vivo preclinical models (cell lines, cloning of human tumor stem cells, murine grafted tumors, human xenografts). Taxoids constitute a new class of antimitotic agents different from vinca-alkaloids: on the one hand, paclitaxel and docetaxel can be considered as inhibitors of the reaction of depolymerization of microtubules into tubulin; on the other hand, vinca-alkaloids inhibit reaction of polymerization of tubulin into microtubules. An active program of medicine chemistry is done in various pharmaceutical and academic Institutions with two objectives: knowledge of structure-activity relationships and selection of new candidates for clinical trials.

The discovery of PTHrP was the result of research on the mechanisms by which some cancers cause hypercalcemia (humoral hypercalcemia of malignancy) without necessarily metastasizing to bone. PTHrP is also present in various normal adult and fetal tissues. Its concentration is normally very low (picomolar) in blood, but it is more abundant in milk (nanomolar concentration). PTHrP seems able to exert autocrine/paracrine as well as endocrine effects on bone metabolism. A major role for PTHrP in regulation of fetal bone metabolism has been demonstrated in mice. Homologous recombination has been used in these rodents to remove the major coding exon from one copy of the mouse PTHrP gene in embryonic stem cells. Subsequently generated chimeric mice transmit the mutant PTHrP allele through the germline. Homozygous mutants died immediately after birth and had a multitude of skeletal abnormalities. So PTHrP seems necessary to embryonic development of the skeleton. PTHrP (1-34), like PTH (1-34) fragments, might be responsible for both bone resorption and formation. Although the effects of the carboxyl-terminal fragments are still controversial, PTHrP (107-111) fragment seems able to inhibit osteoclast activity. PTHrP (1-34), whose 8 of the first 13 amino-acids are identical with those in PTH (1-34), acts through the same receptor as PTH on osteoblasts and renal cells membrane. The PTHrP/PTH receptor sequence is now well established. PTHrP-receptor coupling is mediated by cyclic AMP and/or inositols-phosphate. The consequent activation of protein kinase A and intracellular calcium or protein kinase C, respectively, locally induces growth factors or cytokines secretion, responsible for the observed effects. The role of PTHrP appears important during pregnancy and lactation, when it stimulates fetal bone growth by increasing calcium transport from the dam to its fetus and maternal bone resorption allowing calcium supply for milk production, respectively. Such a role would be particularly important in domestic ruminants, which are often simultaneously pregnant and lactating. The role of PTHrP during aging (especially in post-menopausal women in which bone loss may induce osteoporosis) remains unknown and might be of peculiar interest since PTHrP (1-34) and (107-111) are able to restore bone loss induced by ovariectomy in rats.

Isolated angiitis of the central nervous system (IAC) is an idiopatic, recurrent vasculitis confined to the CNS involving small blood vessels. We describe the clinical, angiographic, and neuropathological data in two patients with IAC and delineate the main clinical and neuropathological features in both cases as well as the importance of a complete autopsy for discovering subclinical vasculitic lesions outside the CNS. Patient 1 concerned a 40 year-old-man that evolved for the last three years, initially with focal seizures, headache, and neurological focal deficits, later on the left sided hemihyposthesia and preferentially left parieto-occipital dysfunctions. He presented an oligoclonal band in CSF with slight hyperproteinorraquia and 25 lymphocytes. A cerebral angiography was compatible with angiitis and a leptomeningeal/cerebral biopsy showed lymphocytic vasculitis in the leptomeningeal and intraparenchymatous cerebral small vessels. These results lead to start a treatment with Cyclophosphamide associated to high dose of steroids. The patient clearly improved and now is almost asymptomatic. Patient 2 concerned a 67 year-old-man that evolved for 4 years with encephalic ischemic lesions distributed and confined throughout the brain stem and cerebellum, temporary remissions occurred and the patient required high-dose steroids and Cyclophosphamide to improve. Conventional and MRI angiographies only suggested the diagnosis that was confirmed at autopsy. The patient died after a massive pulmonary thromboembolism and a complete necropsic study showed abundant lymphocytic infiltrates, without granulomatous lesions, in the intraparenchymatous and leptomeningeal cerebral small vessels specially at the brain stem and cerebellar level where many demyelinated greyish areas and few infarctions were to be seen. The inflammatory cells were, in both cases, predominantly CD4+ T lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystic Fibrosis (CF) and AIDS are primary candidate disorders to be treated by gene therapy, owing to their lethality and the absence of efficient clinical treatments. Treatment of CF by gene therapy will require the transfer of the functional CFTR cDNA into the diseased human airway epithelia since mutations within the CFTR gene are responsible for CF. We have therefore cloned the human CFTR cDNA and developed a recombinant E1-deleted adenoviral vector carrying a CFTR expression cassette. We demonstrated in vitro the ability of this vector to efficiently transduce human lung cells isolated from CF patients and to correct their phenotype. Efficient in, vivo delivery of the CFTR cDNA to the airways of cotton rats and rhesus monkeys was also obtained and no dissemination of the recombinant viral vector in other tissues than the airways was observed. We have therefore designed a phase I clinical trial involving CF patients. In contrast to the monogenic CF disease, the mechanisms of AIDS pathogenesis still remain poorly understood. Such limited knowledge of the disease constitutes a serious restriction to the development of a rational gene therapy strategy for AIDS. Since HIV, the causative agent of AIDS, predominantly infects cells of the hematopoietic system, pluri- or multipotent stem cells may constitute potential targets for the introduction of a foreign anti-HIV gene that will inhibit HIV replication and/or spread. Reimplantation of the genetically modified stem cells into asymptomatic HIV-infected patients should theoretically allow the repopulation of the host's immune system with mature CD4+ cells expressing novel molecules that interfere with viral replication, thus slowing the progression of AIDS. We identified several new transdominant inhibitors derived from the viral TAT and REV proteins and showed their ability to confer to human CD4 lymphocytes resistance against HIV1 infection. Retroviral vectors carrying these potential therapeutic genes have been developed and are currently being tested in vivo in newly developed transgenic animal models, in humanized SCID mice and in macaques.

In vertebrate embryos, all hemopoietic tissues that are successively active during ontogeny (fetal liver, thymus, spleen and bone marrow) are colonized by extrinsic hemopoietic stem cells (HSC). The exception to this rule is the yolk sac (YS) whose progenitors arise in situ. Moreover, the YS is the first hemopoietic site to appear in the embryo. In consequence, it was considered as the primary source of the HSC that transfer from one site to the other until the demonstration that, in birds, the source of definitive HSC was located in the aortic region of the embryo. To assess a possible contribution of intraembryonic sites to mouse hemopoietic development, we developed an in vitro approach that permits the detection of multipotent hemopoietic progenitors in the region surrounding the dorsal aorta. This new site, the paraaortic splanchnopleura (P-Sp), is active from the 10 somite stage to the stage of fetal liver colonization by HSC. The in vitro analysis of the hemopoietic potential of the P-Sp revealed that: 1) progenitors present in this region are multipotent since a single micromanipulated P-Sp cell can give rise to mature B and T lymphocytes and various myeloid cells, when cultivated in appropriate conditions; 2) the P-Sp is the only intraembryonic site endowed with this potential; 3) numbering progenitors present in the YS and P-Sp indicated that precursors appear in both locations at the 10-12 somite stage reaching 15 in each site at 9.5 dpc (25 somites), shortly before the beginning of fetal liver colonisation. During a cytological study of the 9-11 dpc embryo aimed to disclose the cellular basis for our experimental results, two potential hemopoietic sites were uncovered. Cells clusters that resemble avian intraaortic hemopoietic clusters were found in the arteries located close to the coelomic cavity (dorsal aorta, umbilical and omphalomesenteric arteries). Moreover, groups of cells strikingly similar to YS blood islands were uncovered in the mesentery. All these sites are located in areas formed from the P-Sp and are fully developed at the onset of fetal liver colonization. These hemogenic sites most probably develop from the hemopoietic precursors present in the P-Sp.

In a search for assays that might facilitate identification of pluripotent stem cells with extended potentialities, we analysed the properties of hematopoietic progenitor cells detected in the extraembryonic yolk sac and in the intraembryonic part of human embryos between approximately 28 and 45 days of development. Cells from the yolk sac, the liver rudiment and the remainder of the embryo were plated in semi solid methylcellulose colony-assays supplemented with combinations of cytokines. Large BFU-E-derived colonies as well as granulocytic colonies were detected in every yolk sac sample. Interestingly, progenitor cells were also detected in the intraembryonic part, outside the liver and a subclass of these progenitors were detected that generated large granulomacrophagic colonies capable of generating secondary colonies when replated. These were preferentially located in the embryo. Colony-assays initiated with CD34+ cells sorted from the different tissues confirmed these data. These results first indicate that embryonic progenitors exhibit unique phenotypic features, and second, analysis of the distribution of progenitors between the different tissues may suggest the existence of other sites of hematopoietic production. More detailed analysis of the potentialities of these progenitors should now be assessed in vitro in cocultures assays and in vivo by reconstituting immunodeficient mice.

Immunohistochemistry was used to detect markers of the vascular, stromal and hematopoietic cell compartments in the human embryo and early fetus, from 3 to 15 weeks of gestation. CD34 expression was consistently observed at the surface of vascular endothelial cells from off earliest stages tested, at the single exception of embryonic liver blood vessels. Yolk sac hematopoiesis was very transient and limited to primitive erythropoiesis. Clusters of erythroblasts, monocytes and granulocytes appeared from 4 to 5 weeks of gestation in the liver rudiment. The early development of the bone marrow was marked by the rapid invasion, at 8 weeks, of long bone cartilaginous rudiments by CD68+ osteoclast precursors, CD34+ endothelial cells and by preosteoblasts, leading to the development of large vascular sinuses between ossifying trabeculae. Endogenous erythro- and granulopoiesis developed from week 11 in primary logettes always organized around an arteriole, in a loose stromal mesenchymal network established between the media of these arterioles and the sinusal endothelium. Round, hematopoietic CD34+ cells were seen occasionally in yolk sac blood vessels. In the liver they were rare and intermingled as single cells in the hepatocyte cords; strikingly, CD34+ hematopoietic cells could seldom be detected in the developing bone marrow. In contrast, compact clusters of non-endothelial, round CD34+ CD45+ hematopoietic cells were detected, during the 5th week of development, in close association with the ventral wall of the dorsal aorta. These cells exhibit phenotypic and functional characteristics of very primitive hematopoietic progenitors. This observation is in striking correlation with the evidence accumulated in animal models that stem cells for the late embryonic and adult hematopoietic systems develop inside the embryo per se, in the vicinity of the dorsal aorta. We thus suggest that these aorta-associated CD34+ cells, that exhibit an anatomic localization similar to that of the intraembryonic stem cells identified in the avian and murine embryo, are the real stem of human hematopoiesis.

Human cord and placental blood provides a rich source of hematopoietic stem cells. On the basis of this finding, umbilical cord blood stem cells have been used to reconstitute hematopoiesis in children with malignant and non malignant diseases after treatment with myeloablative doses of chemoradiotherapy. Early results show, that a single cord blood provides enough hematopoietic stem cells to provide short and long term engraftment, that the incidence and severity of graft versus host disease has been low even in HLA mismatched transplants. These results are encouraging enough, to embark on large scale banking of cord blood for purposes of future allogeneic and autologous stem cell transplantation, to promote studies on the unique properties of fetal and neonatal hematopoiesis, to study the immunological properties of cord blood cells, to initiate investigations on gene transfer into human cord blood cells for future gene therapy trials. This review will briefly summarize the current knowledge on cord blood transplantation as well as the future development of research on this unique source of hematopoietic stem cells.

Chimeras built between a quail embryo and a chick yolk sac have led to the demonstration that, in the avian model, intra-embryonic hemopoietic stem cells (HSC) relay HSC originating from the yolk sac. Converging experimental approaches have localized the emergence of intraembryonic HSC to the region of the aorta. Today's session will be dedicated to reviewing experimental data in mouse and man that clearly indicate that this model of hemopoietic ontogeny is also operating in mammals.