Megakaryocytes: Regulators of Bone Mass and Hematopoiesis

poster abstractEmerging evidence demonstrates that megakaryocytes (MK) play a key role in regulating skeletal homeostasis and hematopoiesis. Recent reports show that MK reside in close proximity to hematopoietic stem cells (HSC). Genetic depletion of MK resulted in mitotic activation of HSC suggesting that MK maintain HSC quiescence. Other studies demonstrated that following irradiation, surviving MK migrate to endosteal surfaces where osteoblast (OB) lineage cells dramatically increase and promote engraftment of transplanted HSC. Here we investigated if MK directly impact hematopoiesis or whether they indirectly support HSC function through their interaction with OB-lineage cells. Our data suggests that LSK (Lin-Sca+CD117+, an enriched HSC population) co-cultured with MK and OB generate significantly higher numbers of colony forming cells (HSC function) compared to LSK cocultured with either MK or OB alone. The functionality of this in vitro data was confirmed in vivo with transplantation studies which showed increased engraftment in mice transplanted with LSK cells co-cultured with OB and MK compared to LSK cells co-cultured with OB alone. To test if loss of MK negatively impacts osteoblastogenesis, we generated conditional knockout mice where cMpl, the receptor for the main MK growth factor, thrombopoietin (TPO), was deleted in MK (cMplfl/fl x PF4Cre). Unexpectedly, these mice exhibited a 10-fold increase in platelet numbers, megakaryocytosis, a dramatic expansion of phenotypically defined hematopoietic precursors, and a remarkable 20-fold increase in the bone volume fraction. Collectively, these data indicate that while MK modulate HSC function, this activity is in part mediated through interactions with OB and suggest a complex role for TPO and MK in HSC regulation. While work is needed to further elucidate mechanisms, understanding the coordinated interaction between MK, OB, HSC, and TPO/Mpl should inform the development of novel treatments to enhance HSC recovery following myelosuppressive injuries, as well as bone loss diseases, such as osteoporosis

Ultrafast Atomic Diffusion Inducing a Reversible (2√3×2√3)R30°↔(√3×√3)R30° Transition on Sn/Si(111)∶B

Dynamical phase transitions are a challenge to identify experimentally and describe theoretically. Here, we study a new reconstruction of Sn on silicon and observe a reversible transition where the surface unit cell divides its area by a factor of 4 at 250 °C. This phase transition is explained by the 24-fold degeneracy of the ground state and a novel diffusive mechanism, where four Sn atoms arranged in a snakelike cluster wiggle at the surface exploring collectively the different quantum mechanical ground states.This work was supported by the French Agence Nationale de la Recherche (ANR) under Contract SurMott, No. NT-09-618999, and by Spanish Ministerio de Economía y Competitividad, Project No. MAT2014-59966-R

Osteomacs interact with megakaryocytes and osteoblasts to regulate murine hematopoietic stem cell function

Networking between hematopoietic stem cells (HSCs) and cells of the hematopoietic niche is critical for stem cell function and maintenance of the stem cell pool. We characterized calvariae-resident osteomacs (OMs) and their interaction with megakaryocytes to sustain HSC function and identified distinguishing properties between OMs and bone marrow (BM)–derived macrophages. OMs, identified as CD45+F4/80+ cells, were easily detectable (3%-5%) in neonatal calvarial cells. Coculture of neonatal calvarial cells with megakaryocytes for 7 days increased OM three- to sixfold, demonstrating that megakaryocytes regulate OM proliferation. OMs were required for the hematopoiesis-enhancing activity of osteoblasts, and this activity was augmented by megakaryocytes. Serial transplantation demonstrated that HSC repopulating potential was best maintained by in vitro cultures containing osteoblasts, OMs, and megakaryocytes. With or without megakaryocytes, BM-derived macrophages were unable to functionally substitute for neonatal calvarial cell–associated OMs. In addition, OMs differentiated into multinucleated, tartrate resistant acid phosphatase–positive osteoclasts capable of bone resorption. Nine-color flow cytometric analysis revealed that although BM-derived macrophages and OMs share many cell surface phenotypic similarities (CD45, F4/80, CD68, CD11b, Mac2, and Gr-1), only a subgroup of OMs coexpressed M-CSFR and CD166, thus providing a unique profile for OMs. CD169 was expressed by both OMs and BM-derived macrophages and therefore was not a distinguishing marker between these 2 cell types. These results demonstrate that OMs support HSC function and illustrate that megakaryocytes significantly augment the synergistic activity of osteoblasts and OMs. Furthermore, this report establishes for the first time that the crosstalk between OMs, osteoblasts, and megakaryocytes is a novel network supporting HSC function

Understanding reliever overuse in patients purchasing over-the-counter short-acting beta2 agonists : an Australian community pharmacy-based survey

Peer reviewedPublisher PD

Conjugation with L, L-diphenylalanine Self-Assemblies Enhances In Vitro Antitumor Activity of Phthalocyanine Photosensitizer

We present the synthesis and characterization of new peptide conjugates obtained by hierarchical co-assembly of L,L-diphenylalanine (FF) and zinc phthalocyanine complexes (ZnPc) in water. Self-assembly capabilities under defined conditions were investigated by scanning electron microscopy, and photophysical properties were evaluated using UV-Vis and fluorescence spectroscopy. AFM observations demonstrated that these ZnPcs form different highly ordered arrays on the crystalline faces of the FF microplates and that surface roughness significantly changes with the presence of differently substituted phthalocyanine units. XRD assays showed that the overall molecular packing of the conjugates is organized according to a hexagonal symmetry, with ZnPcs hosted in the interstices of the peptide phase. In vitro photodynamic studies were conducted on human breast cancer MCF-7 cells to investigate both cellular uptake and cytotoxicity. It was shown that FF self-assemblies are not toxicity and enhance accumulation of ZnPc in MCF-7 cells, improving apoptotic cell death upon irradiation. Our findings demonstrate enhancement of ZnPc antitumor efficiency by FF conjugates and a proof-of-concept for new photosensitizer carriers based on peptide conjugates

Soft drink and juice consumption and renal cell carcinoma incidence and mortality in the European Prospective Investigation into Cancer and Nutrition

Background: Renal cell carcinoma (RCC) accounts for more than 80% of kidney cancers in adults, and obesity is a known risk factor. Regular consumption of sweetened beverages has been linked to obesity and several chronic diseases, including some types of cancer. It is uncertain whether soft drink and juice consumption is associated with risk of RCC. We investigated the associations of soft drink and juice consumption with RCC incidence and mortality in the European Prospective Investigation into Cancer and Nutrition (EPIC). Methods: A total of 389,220 EPIC participants with median age of 52 years at recruitment (1991–2000) were included. Cox regression yielded adjusted HRs and 95% confidence intervals (CI) for RCC incidence and mortality in relation to intakes of juices and total, sugar-sweetened, and artificially sweetened soft drinks. Results: A total of 888 incident RCCs and 356 RCC deaths were identified. In models including adjustment for body mass index and energy intake, there was no higher risk of incident RCC associated with consumption of juices (HR per 100 g/day increment = 1.03; 95% CI, 0.97–1.09), total soft drinks (HR = 1.01; 95% CI, 0.98–1.05), sugar-sweetened soft drinks (HR = 0.99; 95% CI, 0.94–1.05), or artificially sweetened soft drinks (HR = 1.02; 95% CI, 0.96–1.08). In these fully adjusted models, none of the beverages was associated with RCC mortality (HR, 95% CI per 100 g/day increment 1.06, 0.97–1.16; 1.03, 0.98–1.09; 0.97, 0.89–1.07; and 1.06, 0.99–1.14, respectively). Conclusions: Consumption of juices or soft drinks was not associated with RCC incidence or mortality after adjusting for obesity

Dietary intake of advanced glycation endproducts and risk of hepatobiliary cancers: A multinational cohort study

Advanced glycation endproducts (AGEs) may contribute to liver carcinogenesis because of their proinflammatory and prooxidative properties. Diet is a major source of AGEs, but there is sparse human evidence on the role of AGEs intake in liver cancer etiology. We examined the association between dietary AGEs and the risk of hepatobiliary cancers in the European Prospective Investigation into Cancer and Nutrition prospective cohort (n = 450 111). Dietary intake of three AGEs, Nε -[carboxymethyl]lysine (CML), Nε -[1-carboxyethyl]lysine (CEL) and Nδ -[5-hydro-5-methyl-4-imidazolon-2-yl]-ornithine (MG-H1), was estimated using country-specific dietary questionnaires linked to an AGEs database. Cause-specific hazard ratios (HR) and their 95% confidence intervals (CI) for associations between dietary AGEs and risk of hepatocellular carcinoma (HCC), gallbladder and biliary tract cancers were estimated using multivariable Cox proportional hazard regression. After a median follow-up time of 14.9 years, 255 cases of HCC, 100 cases of gallbladder cancer and 173 biliary tract cancers were ascertained. Higher intakes of dietary AGEs were inversely associated with the risk of HCC (per 1 SD increment, HR-CML = 0.87, 95% CI: 0.76-0.99, HR-CEL = 0.84, 95% CI: 0.74-0.96 and HR-MH-G1 = 0.84, 95% CI: 0.74-0.97). In contrast, positive associations were observed with risk of gallbladder cancer (per 1 SD, HR-CML = 1.28, 95% CI: 1.05-1.56, HR-CEL = 1.17; 95% CI: 0.96-1.40, HR-MH-G1 = 1.27, 95% CI: 1.06-1.54). No associations were observed for cancers of the intra and extrahepatic bile ducts. Our findings suggest that higher intakes of dietary AGEs are inversely associated with the risk of HCC and positively associated with the risk of gallbladder cancer