In sexually reproducing animals all gametes of either sex arise from primordial germ cells (PGC). PGC represent a small cell population, appearing early during embryo development. They represent a key cell population responsible for the survival and the evolution of a species. Indeed, the production of gametes will assure fertilisation and therefore the establishment of the next generation. Until recently only few laboratories were working on PGC biology. A new interest emerged since these cells have the ability to function as pluripotent stem cells when established as cell lines. Indeed, like embryonic stem cells (ESC), embryonic germ cells (EGC) are able to differentiate in a wide variety of tissues. In vivo, EGC are able, after injection into a host blastocyst cavity to colonise the inner cell mass and to participate in embryonic development. In vitro studies in human and mouse have also shown their capacity to differentiate into a large variety of cell types allowing the study of processes involved in cardiomyocyte, haematopoietic, neuronal and myogenic differentiation pathways. We present here the last updates of PGC ontogeny focusing mainly on the murine model.

Stem cells are undifferentiated cells, with the ability to self renew and to differentiate into specialised cells. Besides embryonic stem cells, adult, fetal and umbilical cord blood (UB) stem cells are to be distinguished. These cells are multipotent. Embryonic germ cells (EG) that also are fetal stem cells have proven to be truly pluripotent, since they are able to give derivatives of the three primitive embryonic layers. EG cells have a normal karyotype, and exhibit remarkable long-term proliferative potential. Fetal stem cells and UB cells have already been used in cell therapy trials (e.g., Parkinson's disease, congenital immunodeficiencies and hemopathies). The applications in the field of reproductive biology will lead to a better understanding of genomic imprinting with EG cells. The obstetrician and gynaecologist could act a central part in the production and study of fetal stem cells, using tissues from aborted fetuses or collecting cord blood stem cells.

Many degenerative diseases are not curable by means of classical medicine. The long term objective of cell therapy is to treat the patients with their own stem cells that could be either purified from the diseased organ or from "reservoirs" of stem cells such as that constituted by the bone marrow. The existence of stem cells in the organs or reservoirs is now established in vitro and in some cases, in animal models. Numbers of technical problems linked to the scarcity of these cells still delay the clinical use of purified stem cells. However, clinical protocols using heterogeneous cell populations have already started to treat a growing number of diseases. In some case, autologous cells can be used, as it is the case for bone marrow transplantation in blood diseases. Mesenchymal cells, also purified from the bone marrow are currently used in orthopaedic diseases. Because these cells reveal a broad differentiation potential, active research programs explore their possible use for treatment of other diseases. Bone marrow also contains vascular stem cells that could be active in reappearing defective vessels responsible for ischaemic diseases. Indeed, clinical trials in which bone marrow cells are injected in the cardiac muscle of patients with myocardial infarction or in the leg muscle (gastrocnemius) of patients with hind limb ischaemia have already started. Artificial skin prepared from skin biopsies is used for the reconstitution of the derma of severely burned patients. Clinical trials have also started, using allogenic cells. The patients must be treated by immunosuppressive drugs. Neurodegenerative diseases such as Parkinson have been successfully treated by intra-cerebral injection of foetal neurones. Pancreatic islets implanted in the liver have shown to re-establish a normal glycaemia in diabetic patients. However, all these clinical trials use differentiated cells or at least progenitors which display differentiation potential and lifetime much more restricted than those of stem cell. Numbers of laboratories are currently working to improve stem cell purification and expansion. This is a prerequisite to use these stem cells as a more efficient second generation cell therapy product.

To show the advantages of the in vivo HRT2 confocal microscope corneal module for studying the superficial and peripheral corneal and conjunctival epithelia.

Therapeutic intensification of small cell lung cancer (SCLC) relies on either the simultaneous and repeated administration of a greater number of drugs without cross-resistance, or to the use of classical combinations with greater intensity, either by increasing the doses in each cycle or by reducing the intervals between cycles. The authors review the trials concerning disseminated SCLC: eight randomised studies have compared a standard regimen with an intensified regimen: only one has demonstrated a benefit in terms of survival with the intensified regimen. They will then discuss the problem of intensification of the chemotherapy in the particular case of localised SCLC, which requires the combination of chemotherapy and thoracic radiotherapy: two studies were in favour of the intensified regimen. Lastly, intensification, associating massive doses of polychemotherapy with autologous bone marrow graft or re-injection of hematopoietic stem cells, increases the response rate at the price of a significant increase in toxicity and costs, without benefit in terms of survival.

Use of adipose tissue transfer in plastic and reconstructive surgery is not new, and has been the subject of numerous studies. Transfer of autologous adipose tissue was reported for the first time at the end of the 19th century. Ideas and techniques have greatly changed during the last century. Adipocyte transfer has attracted renewed interest in recent years, due in particular to the development of Lipostructure by Coleman, who introduced a procedure based on strict methodology and the use of specific material. The history of adipose tissue transfer is retraced through the works of various authors and briefly recounted by highlighting the major landmarks of its advance. The evolution of ideas and techniques can be divided into three periods. The period before the introduction of lipoaspiration was termed "open surgery", when adipose tissue was harvested by surgical excision. The next period is that following the discovery of lipoaspiration, called the "unrefined" period, during which adipose tissue was obtained by aspiration and reinjected without preparation. During the third period, following the works of Coleman, the adipose tissue now undergoes non-traumatic refinement before grafting; this period is called "non-traumatic refined". Various studies have shown that this technique causes little damage to the cells and have demonstrated survival of the tissue transferred. Discovery of the developmental capacities of the various lineages from a mesodermal stem cell, and in vitro culture of these cells, opens up new research perspectives and clinical applications. From this precursor cell, adipocytes, osteoblasts, chondrocytes, myocytes and neurone-like cells can be developed. The future of autologous reconstruction appears promising.

THE SITUATION: Islet transplantation stands as a promising curative treatment for type 1 diabetes. Improvements of this still experimental procedure were recently obtained through the modification of the immunosuppressive regimen and the increase of the islet mass delivered to the patient. Several centers have now reported rates of insulin-independence of 80% and beyond after one year, although these cohorts of patients are limited, and the results restricted to experienced centers.

Stem cells are undifferentiated cells, with the ability to self renew and to differentiate into specialised cells. Embryonic stem cells (ES) have proven to be truly pluripotent, since they are able to give derivatives of the three primitive embryonic layers. Human ES have a normal karyotype, maintain high telomerase activity, and exhibit remarkable long-term proliferative potential, providing the possibility for unlimited expansion in culture. Though human ES cell-based transplantation therapy holds great promises to successfully treat a variety of diseases (e.g., Parkinson's disease, diabetes, and heart failure) many barriers remain in the way of successful clinical trials. Less spectacular, the applications in the field of reproductive biology are also outstanding: stem cell biology will lead us to a better understanding of the cellular and molecular mechanisms of events such as infertility, failure of implantation, genomic imprinting and meiosis. The obstetrician and gynaecologist could act an important part in the production and study of embryonic stem cells. However, these data have to be integrated in the ethical and juridical background of embryonic stem cell research in France.

Stem cells display important capacities of self renewing, proliferation and differentiation. Because those present in the embryo have the more remarkable properties, their potential use in the therapy of until now incurable degenerative diseases have been envisioned. Embryonic stem (ES) cells are located in the inner mass of the balstocyst at early stages of the development. Even in long-term cultures they still retain their undifferentiated features. Under specific culture conditions, ES cells can be committed into a variety of differentiation pathways, giving rise to large amounts of cells corresponding to different tissues (neurones, cardiomyocytes, skeletal muscle, etc.). However, producing these tissues from already established ES cell lines would lead to immune rejection when transplanted to patients. To prevent this pitfall and using the expertise accumulated by animal cloning by nucleus transfer, it has been proposed to adapt this technique to human ES cells. The therapeutic cloning consists in transferring the nucleus of somatic stem cells isolated from the patient into an enucleated oocyte, to allow blastocyst development from which ES cells will be derived. From these stem cells, compatible tissues will be then produced. The problem is that it is in theoretically possible to reimplant the cloned blastocyst into a surrogate mother for obtaining a baby genetically identical to the donor. This is called reproductive cloning. This worrying risk raises important ethic and legal questions.

Neuroendocrine differentiation can be identified in a subset of human breast carcinomas, either as scattered cells or as a predominant neuroendocrine component. We report a case of an invasive breast carcinoma largely composed of neuroendocrine cells. Eight years after a left mammary lumpectomy for a pT2N1MO SBR III invasive ductal carcinoma, a 67-years-old woman presented with a metastastic neuroendocrine sternal mass. To establish a relationship between mammary carcinoma and bone metastasis, histological slides of both the breast tumor and axillary lymph nodes were reviewed, and an immunohistochemical study was performed. They showed that: a) the mammary carcinoma was composed of a majority of small and large neuroendocrine cells synaptophysin +, NCAM+, chromogranin - (80%), associated with 2 other differentiated non endocrine components, one of metaplastic squamous carcinoma (10%) and the other of ductal carcinoma (10%); b) 4 axillary lymph nodes were involved by the ductal component which contained few NCAM + but synaptophysin - cells; c) Estrogen and progesterone receptors and HER2 were negative in the breast tumor and the metastatic nodes. We discuss the histogenesis of composite mammary carcinomas with neuroendocrine differentiation, the outcome of each component and the prognostic relevance of such a diagnosis.

Hematodermic CD4/CD56 neoplasm is a recently described entity. This name has been initially proposed by the French Study Group on Cutaneous Lymphomas which established the primary anatomoclinical and pathogenic and cytogenic bases of the disease in 1999. This descriptive and provisional name allowed conceptualizing the entity by its main clinical and phenotypical characteristics. The first case in the literature goes back to 1994. Since that time, several other cases have been published. The expression of CD56 led most of the authors to propose an NK-cell lineage origin. In the last WHO classification of lymphomas, the entity was indexed under the name of "blastic NK-cell lymphoma". However, the authors underlined that there were currently no clues to the etiology of blastic NK-cell lymphoma and that the precise lineage of this disease was still unresolved. At the clinical level the main characteristics of the disease are the skin tropism and the occurrence of a leukemic phase at any time during the course of the disease. The median age is 59 but pediatric cases do exist. At the morphological level skin biopsy shows a monomorphous cell proliferation simulating a pleomorphic T cell cutaneous lymphoma. The diagnosis is based on phenotypic criteria which require frozen tissue. Currently, the main characteristics are the expression of CD4 and CD56 antigens while the main defined lineage specific markers are negative (B-cell, T-cell, NK-cell and myeloid-cell lineages). The origin of the tumor cells still remains uncertain but the plasmacytoid dendritic cell is presently a very serious candidate. The tumor cells share a great phenotypical homology and particularly the expression of the CD123 antigen. Functional homologies have also been demonstrated with tumor cells in vitro. Outcome of CD4/CD56 hematodermic neoplasms is very bad. The median time of survival is 14 months irrespective of the treatment given. Conventional chemotherapies used for the treatment of aggressive lymphomas or acute myeloid leukemias are quickly inefficient.

Confocal microscopy offers important advantages compared to conventional epifluorescence microscopy. It works as an "optical microtome" leading to a accurate image resolution of a defined focal plane. Furthermore, the addition of a Nipkow disk on the confocal microscope greatly accelerates the image acquisition, up to 30 frames per second. Nevertheless, the software-assisted mathematical restoration of images acquired using a wide-field microscope allows to get images with a resolution similar to the one obtained in confocal microscopy. These imaging technologies allowed us to monitor on line cardiac differentiation of murine embryonic stem (ES) cells within 3D structures called embryoid bodies. The high rate acquisition of images using the confocal microscope equipped with a Nipkow disk allows to monitor calcium spiking in differentiating cardiomyocytes within embryoid bodies.

Heart failure is becoming a major issue for public health in western countries and the effect of currently available therapies is limited. Therefore cell transplantation was developed as an alternative strategy to improve cardiac structure and function. This review describes the multiple cell types and clinical trials considered for use in this indication. Most studies have been developed in models of post-ischemic heart failure. The transplantation of fetal or neonatal cardiomyocytes has proven to be functionally successful, but ethical as well as immunological and technical reasons make their clinical use limited. Recent reports, however, suggested that adult autologous cardiomyocytes could be prepared from stem cells present in various tissues (bone marrow, vessels, adult heart itself, adipose tissue). Alternatively, endothelial progenitors originating from bone marrow or peripheral blood could promote the neoangiogenesis within the scar tissue. Hematopietic stem cells prepared from bone marrow or peripheral blood have been proposed but their differentiation ability seems limited. Finally, the transplantation of skeletal muscle cells (myoblasts) in the infarcted area improved myocardial function, in correlation with the development of skeletal muscle tissue in various animal models. The latter results paved the way for the development of a first phase I clinical trial of myoblast transplantation in patients with severe post-ischemic heart failure. It required the scale-up of human cell production according to good manufacturing procedures, started in june 2000 in Paris and was terminated in november 2001, and was followed by several others. The results were encouraging and prompted the onset of a blinded, multicentric phase II clinical trial for skeletal muscle cells transplantation. Meanwhile, phase I clinical trials also evaluate the safeness and efficacy of various cell types originating from the bone marrow or the peripheral blood. However, potential side effects related to the biological properties of the cells or the delivery procedures are being reported. High quality clinical trials supported by strong pre-clinical data will help to evaluate the role of cell therapy as a potential treatment for heart failure.

AL amyloidosis is a rare disorder characterised by tissue deposition of a fibrillary proteinaceous material, formed from monoclonal immunoglobulin light (or exceptionally heavy) chains. Although it may complicate multiple myeloma or B-cell lymphomas, AL amyloidosis is often associated with a low burden of clonal plasma cells ("primitive" AL amyloidosis). The mechanisms involved in the formation of AL amyloid deposits remain unclear, but are probably related to structural peculiarities of monoclonal immunoglobulin light chains. AL amyloidosis is usually a systemic disease, often revealed by renal involvement, the most common complication of the disease. The longterm prognosis of AL amyloidosis is poor, mainly related to amyloid restrictive cardiomyopathy leading to congestive heart failure. Oral melphalan and prednisone is considered the standard treatment for AL amyloidosis, but with limited increase in the median survival. High-dose intra-venous melphalan with autologous stem cell transplantation is an effective treatment, aimed at eliminating the clonaly expanded plasma cells, which has been shown to induce complete hematologic remissions and to prolong survival. However, the tolerability of such treatment is low, limiting its use to selected patients. The development of new drugs, able to interfere with amyloid fibril deposition, may provide a new therapeutic approach.