Neural stem cells have recently been found in the central nervous system of adult rodents and humans. In defined conditions, these multipotent cells can generate the three major cell types of the nervous system (neurons, oligodendrocytes and astrocytes). These findings raise questions on the functional role of neural stem cells in the adult brain, and point to the possibility of novel therapeutic approaches. We have been investigating the functional consequences of neural stem cells for the adult circuits of the olfactory system. We are currently investigating this unexpected juvenile characteristic for cognitive functions. For instance, we are exploring the potential of brain adaptation brought into play by adult neurogenesis. Our most recent studies show that neurogenesis contributes to long-term adjustment of the mature brain. Many questions remain to be answered, however. To what extent can we distinguish and compare neuronal production during embryogenesis and adulthood? How does a newborn cell migrate and find its target? How is cellular fate decided? By showing correlations between the regenerative capacities and cognitive functions of the adult brain, our results have interesting implications for the use of endogenous neuronal stem cells for brain repair in patients with neurodegenerative diseases or brain injury due to stroke or trauma.

The unique properties of stem cells are opening the door for the development of new therapeutic approaches notably in oncology and regenerative medicine. Embryonic stem cells are theoretically very promising for that purpose. However, autologous stem cells derived from blood and bone marrow are the ones which have been tested in clinical trials. Amongst these, adult mesenchymal stromal cells (MSCs) possess particularly attracting properties, as they are easily expanded in vitro and possess the potential to differentiate into multiple cell lineages. Moreover, MSCs can be genetically modified and utilized as a biopharmaceutical. Several research groups are currently investigating both the fundamental properties of MSCs and applicable therapies derived from their use, particularly in cardiology but also in cancer and immunomodulation. Recently, we described that under appropriate stimulation, MSCs can behave as potent antigen-presenting cells (APCs) which is of interest in our understanding of hematopoietic system immunobiology. In addition, the antigen-presenting functions of MSC could theoretically be exploited as a new therapeutic tool in cancer therapy in order to amplify immune responses against tumor-specific antigens. In addition, genetically-modified MSCs are widely tested in preclinical studies and we will here present our results regarding IL2-producing MSCs as an anticancer agent. In Canada, the activities within the field of progenitor and stem cell therapeutics has been consolidated within the National Canadian Stem Cell Network which groups researchers, clinicians, engineers and ethicists, all dedicated to study this new promising pharmaceutical avenue.

With Ham, Leeuwenhoek discovered animalcules in human semen in 1677, without theoretical interpretations. Discussions focused on the respective role of ovum and animalcules during two centuries with erroneous doctrines. Modern ideas on status and origin of animalcules are associated with the development of the cell theory. Animalcules became spermatozoa. In 1875, Hertwig observed that the head of spermatozoon becomes a pronucleus and combines with the female pronucleus, thus establishing the concept that fertilization is the conjugation of two cells. During the first half of 20th century, endocrinology and genetics influenced management of infertile couples. Cryopreservation, analyses of ultrastructural morphology improved knowledges of normal and abnormal male gametes. In Vitro Fertilization and more IntraCytoplasmic Sperm Injection opened new views on the role of spermatozoa in human generation. Genetics and procreation were more and more so linked that each perspective of further advances shocked ethical considerations as transgression of natural biology. The future of spermatozoon in human reproductive programs remains a mystery according to, for example, experimental development using stem cell cultures.

The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases.

Contrary to the long-held dogma according to which the adult mammalian brain does not produce neurons anymore, neuronal turnover has been reported in two discrete areas of the adult brain: the hippocampus and the olfactory bulb. Adult-generated neurons are produced from neural stem cells located in the hippocampal subgranular zone and the subventricular zone of the lateral ventricles. Recently, number of genetic and epigenetic factors that modulate proliferation of stem cells, migration, differentiation and survival of newborn neurons have been characterized. We know that neurogenesis increases in the diseased brain, after stroke or after traumatic brain injury. Importantly, progenitors from the subventricular zone, but not from the subgranular zone, are incorporated at the sites of injury, where they replace some of the degenerated neurons. Thus, the central nervous system has the capacity to regenerate itself after injury and, today, researchers develop strategies aimed at promoting neurogenesis in diseased areas. This basic research is attracting a lot of attention because of the hope that it will lead to regeneration and reconstruction therapy for the damaged brain. In this review, we discuss major findings concerning the organization of the neurogenic niche located in the subventricular zone and examine both intrinsic and extrinsic factors that regulate adult neurogenesis. Then, we present evidences for the intrinsic capability of the adult brain for cell replacement, and shed light on recent works demonstrating that one can greatly enhance appropriate brain cell replacement by using molecular cues known to endogenously control proliferation, migration, differentiation and/or survival of subventricular zone progenitors. Finally, we review some of the advantages and limits of strategies aimed at using endogenous progenitors and their relevance to human clinics.

Hematopoietic growth factors are usually administered in autologous and allogeneic stem cell transplantation. RhuG-CSF and rhuEPO are the most frequently used, either for mobilization of peripheral stem cells or after transplantation for the improvement of hematologic recovery. G-CSF (filgrastim or lenograstim) can be administered alone or in combination with stem cell factor to enhance stem cells mobilization. IL-3 and sargramostim are not used anymore. The protocol of administration of rhuG-CSF is well established. Furthermore, stem cell transplantation with peripheral cells is less expensive than with bone marrow. RhuEPO (erythropoietin) is not effective in mobilization. After transplantation, filgrastim or lenograstim can shorten the neutropenic period and decrease infectious complications. The potential effect of these growth factors on the incidence and the severity of GvHD is still unknown and under debate. The use of rhuEPO after transplantation might be of interest to reduce the need of red blood cell transfusion. Some studies suggest that the administration of rhuEPO should start before delivering the conditioning regimen. The new long acting growth factors such as pegfilgrastim are still under evaluation and their use in mobilization seems promising.

Neutropenia and its subsequent infectious complications represent the most common dose-limiting toxicity of cancer chemotherapy. Febrile neutropenia (FN) occurs with common chemotherapy regimens in 25 to 40 % of treatment-naive patients, and its severity depends on the dose intensity of the chemotherapy regimen, the patient's prior history and comorbidities. Neutropenia is associated with the risk of life-threatening infections as well as chemotherapy dose reductions and delays that may compromise treatment outcome. One of the first, most important and sustained applications of recombinant DNA technology in medicine was the cloning and introduction into clinical practice of several glycoprotein factors involved in the regulation of hematopoiesis. Colony-stimulating factors (CSFs) such as granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are now an integral part of the prevention of potentially life-threatening FN. Important uses of CSFs in oncology are prevention of FN after chemotherapy, treatment of FN, collection of CSF-mobilised peripheral stem cells and support following peripheral stem cells transplantation. This article reviews the data supporting the clearly clinical applications of CSFs in oncology.

Granulocyte colony stimulating factors (G-CSF) are largely used in the treatment of hematologic disorders to improve both the myelosuppression which might directly result from the disease or indirectly induced by the numerous chemotherapy regimen. G-CSF reduces the depth and duration of neutropenia in lymphoma patients and thus allows the design of more dose intense chemotherapy regimen which were shown to improve outcome particularly in patients with diffuse large B-cell and Hodgkin's lymphoma. G-CSF has been studied in patients with acute leukemias (ALL and AML) both concomitantly to induction chemotherapy to sensitize leukemic cells and after chemotherapy to reduce the duration of neutropenia and incidence of severe infection but it's benefit in these settings is still controversial. Myelodysplastic syndromes (MDS) can benefit from G-CSF in association with erythropoietin, particularly for patients with relative good prognosis according to the IPSS score at diagnosis. Still, an improvement of Quality of life needs to be demonstrated in the vue of the cost of these strategies. In aplastic anemia (AA), G-CSF has been used as a support during infection or in association with immunosuppressive treatments but caution is needed regarding the risk of clonal evolution in AA. The benefit of low dose G-CSF in chronic severe neutropenia is well established but the long term consequences of continuous G-CSF support are not known. Finally, G-CSF given alone or after chemotherapy as become one of the key components of hematopoietic stem cell mobilization allowing the use of high dose therapies with autologous or allogeneic stem cell support.

The function of the central nervous system (CNS) is in great part depending on glial cells as, for instance, radial glial cells give rise to cortical neurons, and oligodendrocytes synthesize an immense specialized membrane that enwraps axons to make myelin internodes. Myelin allows fast saltatory conduction of action potentials along myelinated nerve tracts and assures the survival of axons. Oligodendrocytes precursors (OP) emerge during development, first in the spinal cord and later in the telencephalon from multipotential neural precursors in germinative zones around the cerebral ventricles. Morphogens and specific growth factors stimulate the growth, migration and survival of OPs toward axons, culminating in myelination. Such precursors can be isolated from human brain and persist in the adult CNS, allowing some degree of remyelination in the course of a demyelinating disease caused by an infectious agent or inflammation such as multiple sclerosis (MS). These remyelinating cells can recapitulate some molecular events of myelination while new OPs are generated by neural stem cells in the subventricular zones and niches. This natural repair process often decreases with time in man, raising questions about the appropriateness of rodent animal models where remyelination is robust. The challenge today in MS is to develop a pharmacology of myelin repair by endogenous precursors which, if successful, might be more likely to result in clinical benefits than transplantation of myelin-forming cells, shown to be so efficient in rodent models.

The human hair follicle is a unique appendage which results from epithelio-mesenchymal interactions initiated around the 3rd month of development. This appendage has a very complex structure, with more than 20 different cell types distributed into 6 main compartments, namely the connective tissue sheath, the dermal papilla, the outer root sheath, the inner root sheath, the shaft and the sebaceous gland. The pigmentation unit, responsible for hair color, is made of fully active melanocytes located on top of the dermal papilla. This complex appendage has a unique behavior in mammals since, after a hair production phase, it involutes in situ before entering a resting phase after which it renews in a cyclical but stochastic fashion, out of a double reservoir of pluripotent stem cells also to able regenerate epidermis. The pigmentation unit also renews in a cyclical fashion, out of a melanocyte progenitor reservoir which progressively declines with time, provoking the hair whitening process. Finally, the shape of the hair shaft is programmed from the bulb. The hair follicle thus behaves as a fully autonomous skin appendage with its own hormonal control, its own autocrine and paracrine network, its own cycle, appearing as an incredibly complex and stable structure which summarizes the main rules of tissue homeostasis.

Over 50% of all cancer patients presently receive radiotherapy at one stage in their treatment course. Inevitably skin is one of the most frequently damaged tissue due to its localization and constant turn-over. Our present goal is to reduce radiation-induced complications in human skin through stem cell therapy, particulary in human epidermis. Mesenchymal Stem Cells (MSCs) have been shown to be multipotent cells able to engraft in many tissues after injury. Herein, we isolated human MSCs and tested their capability to improve skin wound healing after irradiation. This potential was assessed in NOD/SCID mice which received 30 Gy locally on the thigh. This dose caused within 3 weeks local epidermis necrosis which was repaired within 13 weeks. MSCs were intravenously injected in irradiated mice 24 hours after exposure. Clinical scoring throughout 6 weeks gave indications that human MSCs reduced the extent of damage and accelerated the wound healing process. We show by quantitative qPCR and histological studies the presence of human MSCs derived cells into the scar. Human MSCs homed to the damaged skin and participated to the wound healing process. These results open prospects for cellular therapy by MSCs in irradiated epithelial tissues and could be extended to the whole general field of cutaneous cicatrization, particularly after burns.

Multiple myeloma is a blood disease that is often easy to diagnose, relying on a combination of an excessive medullary plasmacytosis, a serum and/or urinary monoclonal immunoglobulin and one or several signs of organ involvement (anemia, renal failure, bone lesions, hypercalcaemia, infections). The beta2m, serum albumin, and certain chromosomal anomalies of the malignant clone are the essential prognostic factors. Intensive treatment with auto-transplantation of stem cells of peripheral blood is a significant development from which patients less than or equal to 65 years of age have benefited. The diphosphonates are combined with chemotherapy in order to limit the effect on bones, and recombinant erythropoietin is used in certain patients. Above all, therapeutic progress has been made thanks to thalidomide, bortezomib and lenalidomide, even if the optimal utilisation of these molecules is still to be determined.

Waldenström's macroglobulinemia associates a serum monoclonal IgM and a lymphoplasmacytic infiltration of bone marrow, spleen, lymph nodes and various organs. Clinical symptoms are related either to the lymphoid disorder or to the physico-chemical characteristics or antibody activity of the monoclonal IgM. Visceral infiltration may target stomach small bowel, lungs, exocrine glands or skin. Major complications include bone marrow failure, auto-immune cytopenia, occurrence of large cell lymphoma and infections (related either to the humoral immunodeficiency or to chemotherapy). Asymptomatic macroglobulinemia does not deserve any treatment. Otherwise, alkylating agents or nucleoside analogues are first line agents. The benefit of monoclonal antibodies, high dose chemotherapy followed by auto or allogenic stem cell graft is currently assessed.