Low intensity pulsed ultrasound (LIPUS) is one of the methods used to stimulate bone regeneration. This technique is still not well known or explained. The expression of several proteins (VEGF, IL-8, FGF-β, IL-1 β) or genes (ALP and OP) was increased after being exposed to weak ultrasounds, whereas IL-6 and TNF-α were not affected. The purpose of this study was to verify and understand the mechanisms involved in this stimulation, and more specifically to understand if the stimulation concerned only cellular differentiation factors or if it also affected transcription of stem cells into osteoblasts.

Because of its high prevalence and social impact, hearing impairment is a major public health problem. Whatever the cause--heredity, acoustic trauma, aminoglycoside antibiotics, noise exposure or aging--the hearing impairment is often caused by an irreversible loss of sensory hair cells. So far, hearing aids and cochlear implants are the only possibility to "treat" profound deafness. With the advent of regenerative medicine, extensive studies aimed to repair, regenerate or replace lost hair cells have been initiated. Recently, Stefan Heller and colleagues described a guidance protocol to induce mouse embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) to differentiate into mechanosensitive hair cells. The resulting hair cells hold promise as a tool for hair cell molecular physiology and physiopathology, drug discovery, and possibly also hair cell replacement. The next challenges, alternative strategies, their limitations and prospects are also discussed.

This presentation reports a series of data dealing with recurrent genetic abnormalities and gene expression profiles that characterize primary glioblastomas and secondary glioblastomas resulting from the transformation of low grade tumors (grade II and III astrocytomas and oligodendrogliomas). The most recent aspects of the concept of tumor stem cells that may explain the relentless growth of GBM will be reported. Molecular features of tumor neoangiogenesis will be described. Epigenetic alterations and deregulation of gene expression by microRNAs (miRs) will be also included. Some aspects of tumor predisposition will be also discussed. Finally, a short description of exosomes as vectors of tumor information will be presented.

Genomic DNA displays a non canonical structure prone to be damaged and modified by genotoxic stresses, which are induced either by the endogenous metabolism or attacks from environment or therapeutic pressure. Several molecular pathways allow cells to repair such DNA lesions. Additional mechanisms have been selected to bypass such damage at the price of mutations. The maintenance of the genome is thus mediated by the respect of a balance between accurate and inaccurate DNA transactions. This review deals with the tumor suppressor role of such equilibrium, as well as the impact of an unbalance on carcinogenesis.

A 56 year-old, multiparous woman suffering from a myeloproliferative syndrome, who had received multiple red blood cell and platelet transfusions, was the recipient of an allograft of peripheral blood stem cells derived from her HLA-A, B, DR, DQ and DP and ABO identical sister, following myeloablative conditioning. The persistence of severe, isolated thrombopenia resistant to platelet transfusions led to the discovery of anti-HLA class I allo-immunisation. As HLA compatible platelet transfusions did not result in satisfactory platelet increments, we then discovered the simultaneous presence of anti-HPA-1a allo-immunisation. Genotyping of the HPA-1 systems of the patient (HPA-1B/B) and her sister (HPA-1A/B) enabled us to elucidate the mechanism underlying the persistent thrombopenia and the inefficacy of transfusion. In fact, only transfusion of HPA-1B/B platelets (HLA compatible or incompatible) proved to be efficacious. To reduce the level of anti-HPA-1a antibodies, we performed plasmapheresis sessions and used an anti-CD20 monoclonal antibody. It was only on achieving total haematopoietic chimerism, through rapid interruption of the immunosuppression, that we obtained spontaneous normalisation of the platelet count. The present case emphasises the necessity, before undertaking any allograft of haematopoietic stem cells - even if the latter come from a strictly HLA identical member of the family - of performing a search for eventual anti-HPA allo-immunisation.

In order to accomplish its differentiation program, the nucleus of a multipotent cell must be sequentially reprogrammed to acquire and maintain new gene expression patterns. When a stem cell is committed to differentiate towards a given lineage, global genome reprogramming involves both repression of non-affiliated genes and selective activation of genes involved in the establishment of the lineage. Accumulating evidence indicates that lineage specific gene expression is determined not only by the availability of specific transcription factors, but also by epigenetic modifications including both local modifications of DNA and chromatin structure, as well as global topological changes in chromosomes and genes positioning in the nucleus. Combined, these different levels of gene regulation allow for fine controls that integrate environmental and intracellular signals to establish appropriate gene expression programs, and hence ultimately determine the identity of the cell. Therefore, epigenetic modifications most likely precede gene activation and play a critical role in the choices of a stem cell to continue to self-renew or to differentiate. However, the cause-effect relationship between chromatin structure, nuclear architecture and cell-fate decisions is still a matter of debate. The pericentromeric heterochromatin compartment will be presented as one of the best studied examples to understand the impact of and positioning of a gene on its transcription. We will set the influence of heterochromatin compartments in the context of hematopoietic differentiation of human multipotent progenitors.

More than 20 years ago, the finding of a population of cells with the ability of self-renewal and differentiation inside teratocarcinomas (embryonic carcinoma cells) would allow their direct derivation from preimplantation embryos (embryonic stem cells, ESC). The phenomenal pluripotency properties of those cells and the therapeutical potential of their human counterparts triggered a massive interest from the scientific community. The research on the field of pluripotent stem cells improved a lot and many ES-like pluripotent stem cells of several embryonic and adult sources were described. Next step has been the reprogramming of terminally differentiated cells into embryonic cells, with the aim to produce patient-specific stem cells. The recent breakthrough has been the in vitro reprogramming of adult cells into ES cell-like cells named induced pluripotent stem cells (iPSC), using four transcription factors (Oct4, Sox2, Klf4, c-Myc). Even though some challenges remain, we are now one step closer to the eventuality to use these cells for clinical purposes. In this review we propose to analyse the several pluripotent stem cells existing today.

Radiation burn is a determinist effect of localized irradiation. The lesion is in good correlation with absorbed dose. Radiation burn is different from thermal burn. The evolution is spatiotemporal unpredictable with successive inflammatory waves and recurrence of necrosis. The conventional surgical treatment is rarely efficient because each surgical operative act seems to stimulate the inflammatory waves and fibro-necrosis process. The lesion can escape to this conventional surgical treatment. The new therapeutic approach combines surgery and cellular therapy with local administration of autologous mesenchymal stem cells. From 5 years, cell therapy have been an adjuvant treatment of surgery. This association is a therapeutic innovation, it's now the recommendation for conservative surgery of this very serious radiation burn.

Chimerism analysis after allogeneic haematopoietic stem cell transplantation has been used to document engraftment and to adapt therapy promptly. The aim of this study was to document engraftment and to detect as soon as possible relapse in patients with acute myeloid leukaemia who underwent stem cell transplantation. Real-time quantitative polymerase chain reaction is a highly sensitive and reproducible technology. It is useful in some disease to target selected sub-populations in order to have an earlier detection of relapse on cell fractions. In the acute myeloid leukaemia (n=65), analysis of the chimerism on whole peripheral blood cells and bone marrow cells, CD3+ cells, specific myeloid CD33+ cells (from blood) and CD34+ cells (from bone marrow) is of importance. After transplant, 25 patients relapsed (38%), three massively, with chimerism detection in whole blood and bone marrow and 22 insidiously following two different schemes (GRI and GRII). In GRI, (n=13): chimerism of CD33+ and CD34+ cellular fractions allowed an early detection of relapse in 100% of cases undetected in whole cells whereas in GRII (n=9): myeloid cells could identified relapse in 89% of cases when whole blood cells and CD3+ cells expressed a mixed chimerism. This study highlighted the importance of sub-cellular population chimerism documentation enable to ascertain a stable engraftment and to detect early relapse. The selection of sub-cellular population studied with high sensitive technology allows a rapid and efficient intervention before the onset of clinical signs in patient with acute myeloid leukaemia and could improve the patient's follow-up.

Glioblastomas are the most malignant gliomas of the central nervous system. Currently, numerous studies are attempting to decipher their genetic and epigenetic modifications, to identify the cells at the origin of gliomagenesis, and to better understand the molecular bases responsible for invasion and angiogenesis processes.

Selection criteria for embryo transfer is an essential step in ART. Evaluation of pronuclear morphology, evaluation of zygote, embryo cleavage, quality of blastomeres predict the viability of embryos. Multinucleation in cleavage stage embryos is associated with a lower implantation and pregnancy rate.

"Dose-painting" radiotherapy allows for a heterogeneous delivery of radiation within the tumour volume by targeting radioresistant areas defined by functional imaging. Within gross tumour volume, it is possible to define one or more target volumes based on biology (biological target volume [BTV]) and to apply a strategy of intensity modulated radiation therapy (IMRT) that will deliver a higher dose to these regions. In this review of the literature, we will highlight the biological elements responsible for radioresistance, and how to image them, then we will detail the radiotherapy techniques necessary for this approach, before presenting clinical results in various situations (head and neck tumours, prostate, brain tumours, etc.). Despite many difficulties that make dose-painting IMRT unusable in routine nowadays, biology-guided radiation therapy represents one of the major pathways of development of radiotherapy in the coming years.

We report the third case of spontaneous monochorionic dizygous pregnancy, discovered on foetal sex discordance. Blood group testing on the female twin revealed a hematopoietic chimera. The mechanism of monochorionic dizygous formation could be the fusion of two independent zygotes at a late morula stage. A single placental mass with vascular anastomosis then develops. Stem cells exchanged during early foetal life can thus lead to chimeras, in similar conditions to stem cell transfusion in adults. Immaturity of the foetal immune system allows cell graft in the other twin's marrow. Assisted reproductive procedures are believed to promote such pregnancies.

Today, haematopoietic stem cell graft from placental blood concerns more than 15 % of allogeneic grafts. An inter-laboratory study of the quality control of defrosted cord blood units has been coordinated by the French society for cell and tissue bioengineering (SFBCT), with the cord blood bank of Bourgogne Franche-Comté and controlled by the French health products safety agency (Afssaps). The aim of this study is to ensure the inter-laboratory reproducibility of the quality controls practised by the banks during defrosting. The cellular outputs were analyzed according to the defrosting techniques, according to the method used in flow cytometry: single-platform (SP) versus double-platform (DP), or the product nature, i.e. in total blood or miniaturized.

The autologous peripheral blood stem cells (CSP) are used as a support to the restoration of the hematopoiesis in oncohematology. The objective of this work, carried out in the laboratory of cryobiology at the Center Regional of Blood Transfusion, Casablanca, is to assess the short- and long-term results of this type of autograft.

Acute lymphoblastic leukemia is a malignant disorder of lymphoid progenitor cells. Advances in our understanding of lymphoblastic leukemia have mainly come from new molecular technologies and genomics. This article describes recent advances in our understanding of maturation arrest of leukemic cells, initial and subsequent gene defects and rearrangements, the role of chemokines, and lymphoid cell homing. These advances point to new ways of targeting leukemic cells.

The use of alternative methods to animal testing are an integral part of the 3Rs concept (refine, reduce, replace) defined by Russel & Burch in 1959. These approaches include in silico methods (databases and computer models), in vitro physicochemical analysis, biological methods using bacteria or isolated cells, reconstructed enzyme systems, and reconstructed tissues. Emerging "omic" methods used in integrated approaches further help to reduce animal use, while stem cells offer promising approaches to toxicologic and pathophysiologic studies, along with organotypic cultures and bio-artificial organs. Only a few alternative methods can so far be used in stand-alone tests as substitutes for animal testing. The best way to use these methods is to integrate them in tiered testing strategies (ITS), in which animals are only used as a last resort.