Embryonic stem cells (ESC) are self-renewal and pluripotent cells that are able to differentiate in vitro into several cell types in favourable conditions. Technical protocols for in vitro gametes production have been developed in mice and human species. The functionality of such differentiated cells is not always analysed and an early meiotic arrest is a current observation. These kinds of experimentations have also been tested from human induced pluripotent stem cells (IPSC). However, differentiation ends shortly at the primordial germ cell stage.

The freezing phase is a critical step of the freezing process of the hematopoietic stem cells. To standardize the decrease of the temperature, the use of a programmable freezer is recommended. There is no available protocol, neither to describe exactly the validation of a programmable freezer, nor to prove the performance of the freezing/thawing step of the grafts.

High-dose chemotherapy with stem cells support has largely improved in terms of hematopoietic stem and progenitor cells harvest procedures as well as in those, which target or manipulate the cellular composition of autologous graft. Optimal preparative regimens and supportive care had lead to better use of autologous transplantation procedure. For other patients assigned to hematopoietic transplantation, availability of allogeneic donors appears to be an interesting alternative source of hematopoietic stem cells. Since three decades, hematopoietic growth factors development has allowed mobilization optimization and collection of peripheral hematopoietic stem cells leading to reduced days of hospitalization and less blood products requirements, being more cost-effective for patients in autologous transplantation settings and for stem cell collection facilities in allogeneic ones. New perspectives include, besides ex vivo manipulation of graft, development of mobilizing drugs in order to perform transplantation even in poor mobilizers patients. An important goal is achieved with the description of genetic polymorphisms related to optimal mobilization of stem cells. New approach using more promising and selective agents called chemokines, such as plerixafor the main leader among these agents are now available and appear complementary for alternative approach using cytokines alone (G-CSF, GM-CSF, SCF). The aim of this review is to assess the evolution of theses biotechnologies and their role in different steps of autologous transplantation and allogeneic stem cells collection.

In Tunisia as in France, the legislator recognized the organ harvesting as of public health priority. To promote it, cells of coordination are created, and controlled by regulatory texts. There are differences in the strategy of organ harvesting in minor but whether he is alive or dead, he is well protected by law. Organ harvesting in alive child is prohibited in both Tunisia and France but the haematopoietic cells one is authorized. In the minor deceased organ harvesting obeys common principles, appearing in the bioethical law (France) and the law n°91-22 of March 25, 1991 (Tunisia) with a difference in the procedure of the assent of the legal guardian.

To compare H1N1 (2009) influenza A infection characteristics between transplant recipient patients and non-transplanted patients. To assess the evolution of transplanted patients up to 6 months following infection.

As for hemopoietic stem cells, it is thought although not formally demonstrated that bone marrow mesenchymal stem cells (BMMSC) reside in a specific microenvironment or niche characterized by a low O(2) tension. In support of this hypothesis is the observation that MSC can be amplified in vitro under 1-8% O(2) while retaining multipotent capacities. Culture in hypoxic condition may therefore be useful in therapy as the low number of MSC is a major limitation to their use in regenerative medicine and to a lesser extent in the treatment of some autoimmune and overt inflammatory diseases. However hypoxia may modify MSC with significant effects on their metabolism and gene expression hence modifications in their differentiation abilities to mature in specialized cells. This review discusses the various effects of hypoxia on the fate and behavior of MSC and potential clinical applications of culture under hypoxic conditions in regenerative medicine and immune/inflammatory disorders.

Microglia are the resident macrophage population of the central nervous system (CNS). Adequate microglia function is crucial for the homeostasis of the CNS in health and disease, as they represent the first line of defence against pathogens, contributing to immune responses, but are also involved in tissue repair and remodeling. It is therefore crucial to better understand microglia origin and homeostasis. Much controversy remains regarding the nature of microglial progenitors, as the exact contribution and persistence of embryonic and post-natal hematopoietic progenitors to the adult microglial pool in the steady state remained unclear. In this study, we show that post-natal hematopoietic progenitors do not significantly contribute to microglia homeostasis in the adult brain in mice. In vivo lineage tracing studies established that adult microglia derives from primitive hematopoietic progenitors that arise before embryonic day 8. These results identify microglia as an ontogenically distinct population in the mononuclear phagocyte system and have implications for the use of embryonically-derived microglial progenitors for the treatment of various brain disorders.

Mobilization is the biological phenomenon by which hematopoietic stem and progenitor cells (HSPC) transiently egress the bone marrow compartment and circulates in peripheral blood. The biological significance of this phenomenon is incompletely understood, although it is likely to be a component of physiological responses to various forms of stress, and needs for tissue repair. Some of the molecular actors that regulate HSPC mobilization have been unravelled. In addition, some of the inter-individual variability of this phenomenon can be ascribed to clinical as well as to biological parameters. The key role of the interaction between the chemokine SDF-1/CXCL12 and its receptor CXCR-4 has made it an attractive target for pharmacological agents. Recently, plerixafor, the first of its kind, obtained marketing authorization from the U.S. then the European health authorities, on the basis of its activity to increase the mobilization induced by rhG-CSF in patients treated for lymphoid malignancies and who are candidates for high-dose chemotherapy supported with autologous HSPC transplantation.

The Hydra model system is well suited to decipher the mechanisms underlying adult regeneration, specifically those that were robust enough to be maintained across evolution. After mid-gastric bissection head regeneration in Hydra relies on apoptosis-induced compensatory proliferation via the release of Wnt3 by the apoptotic interstitial cells and activation of the β-catenin pathway in the surrounding cycling interstitial cells. As apoptosis-induced compensatory proliferation is also at work in Drosophila regenerating imaginal discs, Xenopus tadpole regenerating their tail and mice regenerating their skin or their liver, this mechanism might represent an evolutionarily-conserved way to launch a regenerative response. However after decapitation, the analysis of the activation of the canonical Wnt pathway in decapitated Hydra showed that apoptosis-induced compensatory proliferation does not take place in this context. Given that the proportion of interstitial stem cells is significantly higher in the middle part than in the upper part of the body column, this suggested that the route taken to regenerate a structure as complex as the head dramatically varies according to the homeostatic status of the tissue at the time of injury. From these observations, we propose a tri-modular model for animal regeneration where the first module or "wound healing module" is followed by a transient module named "inducing module of regeneration" that allows the recruitment of the third module named "re-development module", necessary for repatterning the missing structure. We claim that among these three modules, the inducing module of regeneration is the most drastically constrained by the homeostatic conditions of any given tissue or organ at the time of injury and therefore the most variable.

Late relapses (> 10 years) of breast cancer are mainly observed in ER positive tumors. The yearly relapse rate is still 0.5 % after 10 years. These relapses occurred even if adjuvant chemotherapy was given. Consequently, a better knowledge of the metastatic process is warranted in order to define better treatment options. We will discuss here a case of hormonosensitive breast cancer relapsing 20 years after the initial treatment. We will discuss the most recent data concerning late relapses. New hypotheses concerning disseminated tumoral cells and circulating cells will be reported. We will also review data about stem cells, tumor initiating cells and dormancy state.

The metastatic process generates circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) in bone marrow and other organs which can remain as occult metastases. Various methods and systems have been developed to allow the isolation and identification of those cells but major technical limitations still exist. Research on CTCs is a nevertheless tremendously growing field of cancer research because of their potential clinical applications. CTCs indeed convey predictive information for the development of metastasis and recurrence, and prognostic information regarding patient survival. CTCs enumeration could also be used to monitor the effectiveness of adjuvant treatments. Moreover, enhancing our basic understanding of the metastatic process, CTCs, and DTCs in particular, are thought to contain subpopulations of cells with stem cells properties that would be responsible for relapses.

Metastases formation is a complex process involving genetic and epigenetic modifications leading to several molecular pathway dysfunctions and alterations in the production and fonction of a panel of molecular mediators. Recent studies have shed light on the importance of multiple interactions occuring between tumor cells and host cells involved in the elaboration of a microenvironment permissive for tumor cell survival and growth. These tumor-host interactions are decisive, not only in the primary tumor, but also in secondary sites colonized by tumor cells. Cancer appears more and more as a sytemic disease in which tumor cell is one of the pawn in the game. System of defense are rapidly overwhelmed and tumor cells hijack host cells to promote their dissemination that likely occurs at earlier stages than initially anticipated. In the present review, we describe the novel concepts of metastases formation based on recent transcriptomic analyses and new insights acquired on the tumor microenvironment in the primary tumor and in secondary foci.

Vascularisation is a key for success in bone tissue engineering. Creating a functional vascular network is an important concern so as to ensure vitality in regenerated tissues. Many strategies were developed to achieve this goal. One of these is cellular growth technique by perfusion bioreactor chamber. These new technical requirements came along with improved media and chamber receptacles: bioreactors (chapter 2). Some bone tissue engineering processes already have clinical applications but for volumes limited by the lack of vascularisation. Resorbable or non-resorbable membranes are an example. They are used separately or in association with bone grafts and they protect the graft during the revascularization process. Potentiated osseous regeneration uses molecular or cellular adjuvants (BMPs and autologous stem cells) to improve osseous healing. Significant improvements were made: integration of specific sequences, which may guide and enhance cells differentiation in scaffold; nano- or micro-patterned cell containing scaffolds. Finally, some authors consider the patient body as an ideal bioreactor to induce vascularisation in large volumes of grafted tissues. "Endocultivation", i.e., cellular culture inside the human body was proven to be feasible and safe. The properties of regenerated bone in the long run remain to be assessed. The objective to reach remains the engineering of an "in vitro" osseous free flap without morbidity.

Distraction osteogenesis is a tissue engineering technique based on Ilizarov's study on long bones. McCarthy transposed it rapidly to facial bones. His results in cranial and maxillofacial surgery are good and reproducible. However, the current protocols are long and the devices used are bulky. Finding new devices and association with other tissue engineering techniques should improve distraction osteogenesis and the patient's comfort.