Hematopoietic stem cells, which share with other stem cells of adult tissues the ability to maintain constant the number and diversity of differentiated mature cells throughout adult life offer a fabulous system to analyze mechanisms controlling cell proliferation and differentiation. Cytokines controlling the differentiation of intermediate progenitors into mature cells of the various lineages have been characterized and have been widely used, in vitro as in vivo, to increase the output of differentiated cells. In contrast, despite significant technological advances, molecular events associated with the stem cell decisions first to either self-renew or differentiate, and then to irreversibly commit to one of the lymphoid or of the myeloid pathways are still very badly understood. This is partly explained by the lack of reliable assays, particularly in humans, to assess stem cell activity, and by the difficulty to dissect the composition of molecular complexes regulating gene expression in these very rare cells. Despite these limitations, recent evidence suggests that there is some flexibility in the initial decisions of stem cells, and that extracellular factors may influence stem cell fate. If this is confirmed, it may then become possible to propose new therapeutic strategies based on the manipulation of stem cell properties.

Since many years, the ability to harvest and then graft haematopoietic stem cells in man has allowed to treat with success several lethal diseases in haematology and oncology. Progress in cell biology recently made possible the obtention of human stem cells, particularly of embryonic origin which, theoretically, have all the potentialities of development. Therefore, in spite of other many obstacles still ahead, the perspective of using elements produced from such cells for therapeutic purpose seems closer.

It has been known for many years now that the vocal centers in the hyperstriatum (cortex) of birds with seasonal song behaviour are the site of neuronal generation and, thus, that stem cells capable of giving rise to real neurons exist in the adult. Since then, the notion that neuronal progenitors exist in the adult has been extended to mammals. It seems that the number of brain regions in which neuronal generation is taking place is limited. In addition to the olfactory epithelium where olfactory receptors are under constant renewal, the sites of neuronal regeneration are the olfactory bulb, the dentate gyrus of the hippocampus, the associative cortex--in the macaque--and the cerebellum. Although this represents only a limited number of regions and neuronal types (primarily GABAergic interneurons), the observation that new neurons can be created throughout life raises the possibility to use them in replacement therapy in the human.

Mammalian cells in culture can be modified by gene transfer and these procedures are routinely used in experimental biology. Yet, efficient approaches to modify certain complex cell populations, stem cells or cells organized within a tissue are still lacking. The hurdles to gene transfer can be listed by describing the pathway of a nucleic acid molecule, from the external medium towards the cell nucleus where its encoded information will be expressed. The requirements include the necessity to compact the size of the macromolecule, to overcome electrostatic repulsion, to cross a series of membranes and to establish itself permanently. Viruses have evolved to achieve these goals and understanding their strategies for cell invasion allows to design vectors for gene transfer. Chemicals or biochemicals able to bind DNA, as well as physical methods inducing changes in the structure of membranes can also be useful for gene transfer. The outcome of gene transfer technologies and their improvement pave the way to inovative medical applications and provide powerful tools for exploring the living world.

The birth of physiologically normal and fertile animal of several mammalian species following the transfer of somatic nuclei into recipient enucleated oocytes has stimulated researches on the functional plasticity of cells available from living organisms. This experimental approach, termed cloning, has up to a low efficiency. It however allows the study of mechanisms compatible with the reacquisition of an undifferentiated nuclear status and contributes to researches aimed at controlling the fate of stem cells for therapeutically applications.

X-linked severe combined immunodeficiency (SCID-X1) is a recessive hereditary disorder in which early T and Natural Killer (NK) lymphocyte development is blocked. The genetic disorder results from mutations in the common gamma c chain that participates in several cytokine receptors including the interleukin-2 (Il-2), Il-4, Il-7, Il-9, Il-15 receptors. SCID-X1 offers a reliable model for gene therapy as it is a lethal condition that is, in many cases, curable by allogeneic bone marrow transplantation. We have shown that retrovirus-mediated transfer of the gamma c cDNA induced gamma c chain expression and restored the function of the high-affinity IL-2 receptor on SCI-X1 EBV-transformed B-cell lines. We have the designed culture conditions to study NK-cell and T-cell development of CD34+ hematopoietic progenitor cells. In the culture systems, gamma c transduced CD34+ marrow cells from two SCID-X1 patients were able to mature into CD56+ and/or CD16+ NK cells and into CD4+ TCR alpha beta+ T cells. These preclinical results set the basis for a clinical study of ex-vivo gamma c gene transfer into CD34+ cells from SCID-X1 patients.

The diagnosis and management of acute myeloid leukemia (AML) in the elderly is reviewed, including the basic aspects of epidemiology, cytogenetics, and prognostic factors. AML at higher ages is associated with several unique biologic and clinical characteristics. It generally arise from an early level of hematopoietic stem cells, and has a particularly high incidence of poor prognostic karyotypes. Effective treatment of the elderly patient with AML remains a challenging task. The importance of therapeutic approaches and promising new drugs is summarized. Prospective randomized studies clearly demonstrate that elderly patients benefit from intensive induction therapy. Hematopoietic growth factors accelerate the recovery from treatment-induced neutropenia and may improve the outcome. In patients not eligible for intensive chemotherapy, prospective studies testing different palliative or moderately intensive treatments are needed to improve quality of life and survival. New treatment strategies need to be developed to further improve on the therapeutic perspectives for elderly patients with AML.

Analysis of the legislation concerning xenotransplantation and constitution of stem cell banks reveals an absence of status common to embryos and animals. They do not have any legal status, they are not assimilated to objects, but benefit from protective measures. Xenotransplantation is regulated by a set of rules, while embryo research is currently prohibited in France, but is regulated in other countries. Bioethical legislation raises difficulties related to the early stage of its development and its perverse effects. The consultation process prior to defining legislation must take into account the international dimension and the necessary progress of scientific research.

Two types of epithelial cells derived from a unique embryonic stem cell coexist in the liver: hepatocytes, which form the liver parenchyma, and cholangiocytes which line intrahepatic bile ducts. Both cell types represent more than 70% and around 3% of hepatic cells, respectively. Initially secreted in the canalicular space formed by the apical domain of hepatocytes, bile is subsequently collected and modified in bile ducts. Both types of epithelia can regenerate as a result of differentiated cell proliferation. However, massive or chronic injury may induce the emergence and proliferation of oval cells, a heterogeneous population of small cells expressing embryonic markers that may subsequently differentiate into hepatocytes or cholangiocytes. Oval cells may also give rise to hepatocellular or cholangiocellular carcinomas. They may derive not only from hepatic cells (including hepatocytes and cholangiocytes themselves), but also from extrahepatic haematopoietic stem cells.

Our study is retrospective. We report the results of conventional chemotherapy ins previosly untreated patients with myeloma. Survival and prognostic factors were analysed in 109 patients diagnosed from 1983 to 1992. The median age was 65 years, 87 patients (80%) were including in the stage III according the Durie Salmon staging system. The median survival time was 27 months and 10 years survival rate is 3.66%. In the univariate analysis, two prognostic variables were retained namely the hemoglobin and creatinine level. The study suggest that conventional therapy is a good treatment for old patients. However, patients younger than 55 years, must benefit from intensive chemotherapy supported by autologous bone marrow, pheripheral blood stem cells, or allogenic bone marrow transplantation. A considerable encrace in duration of remission and survival is possible.

Four hematopoietic growth factors have marketing approval in France: filgrastime (G-CSF), malgraostime (GM-CSF), lenograstime (glycolysated G-CSF) and erythropoietin. A standards, options and recommendations document has not yet been established for erythropoietin which is excluded from this report. Administration of hematopoietic growth factors can be proposed in five clinical situations: primary prophylaxis, secondary prophylaxis, curative care, after myeloablative chemotherapy and hematopoietic stem cell grafting, and finally mobilization of peripheral stem cells. Primary prophylaxis: excepting therapeutic trials, the use of hematopoietic growth factors is recommended for clinical situations where a significant incidence of neutropenia with fever has been reported in randomized trials and in rare cases where there is an increased risk of severe infectious complications. Hematopoietic growth factors are indispensable for increasing the quality of cytapheresis peripheral stem cell harvesting.

A multicentric study involving 12 centers was made to investigate the results of peripheral stem cell collection carried out between 1996 and 1997 from 655 patients with hemopathic syndromes or malignant tumors, The aim of this investigation was to determine the predictive factors for transplant quality, and to thereby optimize collection procedures.

Frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17) are related to pathogenic mutations of the Tau gene. One of these, located at codon 279, results in an asparagine to lysine substitution. It was detected in three unrelated families from different origins. This mutation affects splicing, allowing exon 10 to be incorporated more frequently in the Tau transcripts, causing an abnormal preponderance of three-over four-repeat isoforms in soluble tau and the presence of the four-repeat isoforms in the insoluble tau. To better understand this newly described pathology, we analysed data from the three previously reported families. The American family, described as "pallido-ponto-nigral degeneration" is a large family which has been extensively studied (13 neuropathological studies). The Japanese family was initially presented as "pallidonigroluysian degeneration with iron deposition" and recently found to be related to N279 K mutation. We reported clinical, pathological and genetic data from the French family. Clinical particularities are ocular movements alterations with vertical supranuclear palsy, extrapyramidal signs (rigidity, dyskinesia, with atypical resting and postural tremor) and progressive dementia. Partial or no L-DOPA responsiveness is noted. These features led to discuss progressive supranuclear palsy, in some cases. There is no amyotrophy, nor any sensibility to neuroleptics, both signs being observed in other FTDP-17 syndromes. Neuropathology and immunohistochemistry confirm the presence of Tau immunolabeled inclusions, affecting mainly neurons in brain stem nuclei and glial cells in supratentorial white matter. Neuronal loss, which is moderate in frontal and temporal cortex, is severe in substantia nigra and globus pallidum. It is variable in other subcortical structures. In these structures, it is associated with iron deposition. This latter may participate in the degenerative process of cells and led to death in some specific neurons. The selectivity of neuronal death in hereditary diseases, when compared to data concerning sporadic neurodegenerative diseases which share similar clinical signs and neuropathological lesions, reinforces the hypothesis of an increased vulnerability of some neuronal populations which express specific sets of tau isoforms. Neurons particularly involved in these diseases express exclusively exon 10 + tau isoforms.

Despite different therapeutic modalities (surgery, hormones therapy, chemotherapy), 5-year survival in patients with malignant adrenocortical carcinoma remains only 10% to 20%. Bone marrow grafts may be proposed to intensify treatment.

Myelodysplastic syndromes (MDS) are clonal disorders of pluripotent hematopoietic stem cells. MDS occur predominantly over the age of 60 years. The diagnosis of MDS is based on the examination of both blood films and bone marrow aspirate. Diseases such as vitamin B12 and/or folate deficiency, or cytotoxic therapy leading to a marrow dysplasia should be ruled out. Five subtypes are described in the FAB classification : refractory anaemia or refractory cytopenia, refractory sideroblastic anaemia, refractory anaemia with excess of blasts, refractory anaemia with excess of blasts in transformation, chronic myelomonocytic leukaemia. This FAB classification is based on a small number of parameters: percentage of blood and marrow blasts, percentage of ringed sideroblasts and blood monocytes. The anaemia is typically normo- or macrocytic, non regenerative, and in half cases is associated with neutropenia and/or thrombocytopenia. During blood film examination, cell abnormalities have to be notified, i.e. anisocytosis, poikilocytosis of red cells, morphological abnormalities of neutrophils including hypogranulation, hypolobulation, abnormal large platelets. The prognostic and the treatment of MDS depend on the subtype of the FAB classification, the patient's age, the percentage of marrow blasts, the importance of cytopenia, the presence or not of cytogenetic abnormalities and the existence or not of HLA-identical donor.

The association of osteogenic stem cells to a synthetic carrier makes possible the elaboration of bioartificial tissue. Numerous phosphocalcic ceramics does not trigger a foreign body reaction when implanted in bone tissue and thus, a number of materials are available osteogenic stem cell carriers to replace the bone tissue. Several methods can be used to harvest these cells. Their multiplication in vitro can lead to the appearance of anomalies of their metabolism or their karyotype. The culture method also seems to have a major influence on their appearance. The presence of these anomalies could explain the variability of results in terms of bone extracellular matrix synthesis after cell reimplantation. The surgical technique used for the implantation is also of influence. A method suppressing the in vitro period has been developed to avoid any cell metabolism modification. This method allows for a very reproducible bone synthesis in ectopic site. The availability of human embryonic stem cells could help to develop cell graft techniques for bone reconstruction.

In transfusion medicine, flow cytometry (FCM) is a methodology combining laser radiation, optics and a computerized treatment of numerous results. We can measure size, cellularity and fluorescence intensity of cells or particles in suspension after the binding of appropriate fluorescent antibodies or fluorescent dyes. The main utilisation of FCM in transfusion medicine is for quality control of the process of leukocyte reduction in red cell concentrates or in platelet units, using commercial kits. In addition, it is used for the enumeration of CD 34 positive cells before bone marrow transplantation and for control of platelet function in platelet units. For clinical investigations, FCM may be used for red cell phenotyping, essentially to detect minor populations (chimerism), for the estimation of red cell survival, or for the detection of fetal erythrocytes. In the field of platelet immunology, FCM is an essential tool for detecting platelet antibodies (auto or allo), for platelet phenotyping or for cross-matching. In the future perhaps, FCM will permit us to detect bacterial contamination or prion protein in transfused blood cells.