Low-dose pesticide mixture induces senescence in normal mesenchymal stem cells (MSC) and promotes tumorigenic phenotype in premalignant MSC

Humans are chronically exposed to multiple environmental pollutants such as pesticides with no significant evidence about the safety of such poly-exposures. We exposed mesenchymal stem cells (MSC) to very low doses of mixture of seven pesticides frequently detected in food samples for 21 days in vitro. We observed a permanent phenotype modification with a specific induction of an oxidative stress-related senescence. Pesticide mixture also induced a shift in MSC differentiation towards adipogenesis but did not initiate a tumorigenic transformation. In modified MSC in which a premalignant phenotype wasinduced, the exposure to pesticide mixture promoted tumorigenic phenotype both in vitro andin vivo after cell implantation, in all nude mice. Our results suggest that a commoncombination of pesticides can induce a premature ageing of adult MSC, and as such couldaccelerate age-related diseases. Exposure to pesticide mixture may also promote thetumorigenic transformation in a predisposed stromal environment

Pericyte-Like Progenitors Show High Immaturity and Engraftment Potential as Compared with Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) and pericyte progenitors (PPs) are both perivascular cells with similar multipotential properties regardless of tissue of origin. We compared the phenotype and function of the 2 cell types derived from the same bone-marrow samples but expanded in their respective media – pericyte conditions (endothelial cell growth medium 2 [EGM-2]) for PPs and standard medium (mesenchymal stem cell medium [MSM]) for MSCs. After 3 weeks of culture, whatever the expansion medium, all cells showed similar characteristics (MSC markers and adipo-osteo-chondroblastic differentiation potential), although neuronal potential was greater in EGM-2– than MSM-cultured cells. As compared with MSM-cultured MSCs, EGM-2–cultured PPs showed higher expression of the pericyte-specific antigen 3G5 than a-smooth muscle actin. In addition, EGM-2–cultured PPs showed an immature phenotype, with upregulation of stemness OCT4 and SOX2 proteins and downregulation of markers of osteoblastic, chondroblastic, adipocytic and vascular smooth muscle lineages. Despite having less effective in vitro immunosuppression capacities than standard MSCs, EGM-2–cultured PPs had higher engraftment potentials when combined with biomaterials heterotopically-transplanted in Nude mice. Furthermore, these engrafted cells generated more collagen matrix and were preferentially perivascular or lined trabeculae as compared with MSM-cultured MSCs. In conclusion, EGM-2–cultured PPs are highly immature cells with increased plasticity and engraftment potential

Safety Concern between Autologous Fat Graft, Mesenchymal Stem Cell and Osteosarcoma Recurrence

Background: Osteosarcoma is the most common malignant primary bone tumour in young adult treated by neo adjuvant chemotherapy, surgical tumor removal and adjuvant multidrug chemotherapy. For correction of soft tissue defect consecutive to surgery and/or tumor treatment, autologous fat graft has been proposed in plastic and reconstructive surgery. Principal Findings: We report here a case of a late local recurrence of osteosarcoma which occurred 13 years after the initial pathology and 18 months after a lipofilling procedure. Because such recurrence was highly unexpected, we investigated the possible relationship of tumor growth with fat injections and with mesenchymal stem/stromal cell like cells which are largely found in fatty tissue. Results obtained in osteosarcoma pre-clinical models show that fat grafts or progenitor cells promoted tumor growth. Significance: These observations and results raise the question of whether autologous fat grafting is a safe reconstructive procedure in a known post neoplasic context

Expression et régulation de la protéine anti-apoptotique Mcl-1 dans le myélome multiple (implications clinico-biologiques)

La protéine anti-apoptotique Mcl-1 joue un rôle majeur dans la survie des cellules myélomateuses. Nous montrons que la surexpression de Mcl-1 est corrélée à la rechute et à une survie plus courte des patients. Le complexe Mcl-1/Bim est important dans la régulation de l'apoptose dans les plasmocytes malins. En effet, Mcl-1 se lie à Bim et neutralise son effet pro-apoptotique. De plus, l'interaction de Mcl-1 et Bina confère aux deux protéines une stabilité mutuelle par protection de l'ubiquitination et de la dégradation par le protéasome. En effet, la diminution de l'expression de Bim ou de Mcl-1 par shRNA interférence induit une augmentation de la dégradation de Mcl-1 et de Bim dans les cellules shBim et shMcl-1 respectivement. Le Bortézomib est un inhibiteur spécifique du protéasome nouvellement introduit dans le traitement des myélomes multiples (MM) en rechute. L'apoptose induite par le Bortézomib est associée à un clivage de Mcl-1 et à la modification de ses interactions avec les protéines BH3 seulement . En effet, le Bortézomib induit une accumulation de Noxa, une augmentation du complexe Mcl-1/Noxa et une diminution du complexe Mcl-1/Bim. Ainsi, la sensibilité au Bortézomib des cellules myélomateuses peut être expliquée par le déplacement de Bim, BH3 seulement activatrice, par Noxa, BH3 seulement sensibilisatrice, du complexe Mcl-1/Bim, ce qui induit l'activation de Bax/Bak. La régulation de Mcl-1 via son clivage ou via ses interactions protéiques avec les protéines BH3 seulement contribue à réguler l'apoptose des plasmocytes myélomateux.Mcl-1 is a major survival protein for multiple myeloma (MM) cells. Mcl-1 overexpression of Mcl-1 in vivo is correlated with relapse and shorter survival. Mcl-1/Bim complexes are critical in myeloma cells. Mcl-1 neutralizes the pro-apoptotic function of Bim and prevents activation of death effectors. The interaction between Mcl-1 and Bim confers to themselves mutual protection. Indeed, down-regulation of Mcl-1 by sh- RNA leads to unligated Bim to ubiquitin-proteasome- degradation and reciprocally for unliganded Mcl-1 in shBim cells. Bortezomib, a specific proteasome inhibitor, has been approved for the treatment of relapsed or refractory MM. Bortezomib-induced apoptosis, in MM cells, was associated with Mcl-1 cleavage, Noxa induction and caspase activation. Under Bortezomib treatment, Mcl-1/Noxa complexes were highly increased and Mcl-1/Bim interaction were disrupted. Thus, in MM cells, the mechanistic basis for bortezomib sensitivity can be explained mainly by a model in which the sensitizer Noxa can displace Bim, a BH3-only activator, from Mcl-1, thus leading to Bax/Bak activation. The regulation of Mcl-1 via its cleavage or its interactions with "BH3 only" proteins contributes to control apoptosis induction in MM.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

The Osteosarcoma Microenvironment: A Complex but Targetable Ecosystem

International audienceOsteosarcomas are the most frequent primary bone sarcomas, affecting mainly children, adolescents, and young adults, and with a second peak of incidence in elderly individuals. The current therapeutic management, a combined regimen of poly-chemotherapy and surgery, still remains largely insufficient, as patient survival has not improved in recent decades. Osteosarcomas are very heterogeneous tumors, both at the intra-and inter-tumor level, with no identified driver mutation. Consequently, efforts to improve treatments using targeted therapies have faced this lack of specific osteosarcoma targets. Nevertheless, these tumors are inextricably linked to their local microenvironment, composed of bone, stromal, vascular and immune cells and the osteosarcoma microenvironment is now considered to be essential and supportive for growth and dissemination. This review describes the different actors of the osteosarcoma microenvironment and gives an overview of the past, current, and future strategies of therapy targeting this complex ecosystem, with a focus on the role of extracellular vesicles and on the emergence of multi-kinase inhibitors

Gastric cancer cell death analyzed by live cell imaging of spheroids

International audienceAbstract Gastric cancer (GC) is the third cause of cancer-related mortality worldwide and is often diagnosed at advanced stages of the disease. This makes the development of more comprehensive models and efficient treatments crucial. One option is based on repurposing already marketed drugs as adjuvants to chemotherapy. Accordingly, we have previously developed the combination of docetaxel and the cholesterol-lowering drug, lovastatin, as a powerful trigger of HGT-1 human GC cells’ apoptosis using 2D cultures. Because 3D models, known as spheroids, are getting recognized as possibly better suited than 2Ds in toxicological research, we aimed to investigate the efficacy of this drug combination with such a model. We established monocellular spheroids from two human (GC) cell lines, HGT-1 and AGS, and bicellular spheroids from these cells mixed with cancer-associated fibroblasts. With these, we surveyed drug-induced cytotoxicity with MTT assays. In addition, we used the Incucyte live imaging and analysis system to follow spheroid growth and apoptosis. Taken together, our results showed that the lovastatin + docetaxel combination was an efficient strategy to eliminate GC cells grown in 2D or 3D cultures, lending further support in favor of repurposing lovastatin as an adjuvant to taxane-based anticancer treatment

Bone regeneration strategies with bone marrow stromal cells in orthopaedic surgery

International audienceBone is the most transplanted tissue human with 1 million procedures every year in Europe. Surgical interventions for bone repair are required for varied reasons such as trauma resulting non-union fractures, or diseases including osteoporosis or osteonecrosis. Autologous bone grafting is the gold standard in bone regeneration but it requires a second surgery with associated pain and complications, and is also limited by harvested bone quantity. Synthetic bone substitutes lack the osteoinductive properties to heal large bone defects. Cell therapies based on bone marrow or ex vivo expanded mesenchymal stromal stem cells (MSCs) in association with synthetic calcium phosphate (CaP) bone substitutes may be alternatives to autologous bone grafting. This manuscript reviews the different conventional biological and synthetic bone grafting procedures as well as the more recently introduced cell therapy approaches used in orthopaedic surgery for bone regeneration. Some clinical studies have demonstrated safety and efficacy of these approaches but regeneration of large bone defects remain challenging due to the absence of rapid and adequate vascularisation. Future directions in the field of bone regeneration are presented, such as testing alternative cell sources or in situ fabrication of vascularized bone grafts in patients

Response of soil and vegetation in a warm-temperate Pine forest to intensive biomass harvests, phosphorus fertilisation, and wood ash application

The objective of this study was to assess the effects of different intensities of biomass harvesting, and the possible effects of compensation methods, on forest functioning. To do so, we carried out a split-plot experiment (SW France) crossing four different intensities of biomass harvesting (Stem-Only Harvest [SOH], Aboveground Additional Harvest [AAH], Belowground Additional Harvest [BAH], and Whole-Tree Harvest [WTH]) and three compensation methods (control [C], wood ash application [A] and phosphorus fertilisation [P]). The experimental treatments were followed by the plantation of pines (Pinus pinaster). The environmental consequences of treatments on soil and vegetation were evaluated 11 years after the tree plantation.Despite their low additional biomass exports (+10 % for AAH to +34 % for WTH), the non-conventional harvest practices exported much higher quantities of nutrients than the conventional SOH technique (+145 % of exported N in WTH). Additional biomass harvests impacted the soil organic matter content, with negative effects on P-organic, soil cation exchange capacity, exchangeable Ca, and most extractible nutrients. However, tree nutritional status was improved by P-fertiliser or wood ash. We observed a positive effect of wood ash application on soil pH and nutrient content but, like additional harvests, wood ash application decreased the pool of soil organic carbon (~10 %).Overall, the experiment showed that exporting more forest biomass due to the additional harvesting of biomass had negative consequences on the ecosystem biogeochemistry. Additional harvests have impoverished the soil, and decreased the soil organic carbon content. Importantly, applying nutrients as fertiliser or wood ash did not compensate for all the negative impacts of biomass exports and the method of wood ash recycling in forests could even decrease the soil organic carbon

Early fracture healing is delayed in the Col1a2+/G610C osteogenesis imperfecta murine model

International audienceOsteogenesis imperfecta (OI) is a rare heritable skeletal dysplasia mainly caused by type I collagen abnormalities and characterized by bone fragility and susceptibility to fracture. Over 85% of the patients carry dominant mutations in the genes encoding for the collagen type I α1 and α2 chains. Failure of bone union and/or presence of hyperplastic callus formation after fracture were described in OI patients. Here we used the Col1a2+/G610C mouse, carrying in heterozygosis the α2(I)-G610C substitution, to investigate the healing process of an OI bone. Tibiae of 2-month-old Col1a2+/G610C and wild-type littermates were fractured and the healing process was followed at 2, 3, and 5 weeks after injury from fibrous cartilaginous tissue formation to its bone replacement by radiography, micro-computed tomography (µCT), histological and biochemical approaches. In presence of similar fracture types, in Col1a2+/G610C mice an impairment in the early phase of bone repair was detected compared to wild-type littermates. Smaller callus area, callus bone surface, and bone volume associated to higher percentage of cartilage and lower percentage of bone were evident in Col1a2+/G610C at 2 weeks post fracture (wpf) and no change by 3 wpf. Furthermore, the biochemical analysis of collagen extracted from callus 2 wpf revealed in mutants an increased amount of type II collagen, typical of cartilage, with respect to type I, characteristic of bone. This is the first report of a delay in OI bone fracture repair at the modeling phase