Differential involvement of Wnt signaling in Bmp regulation of cancellous versus periosteal bone growth

Bone morphogenetic proteins （Bmp） are well-known to induce bone formation following chondrogenesis, but the direct role of Bmp signaling in the osteoblast lineage is not completely understood. We have recently shown that deletion of the receptor Bmprla in the osteoblast lineage with Dmpl-Cre reduces osteoblast activity in general but stimulates proliferation of preosteoblasts specifically in the cancellous bone region, resulting in diminished periosteal bone growth juxtaposed with excessive cancellous bone formation. Because expression of sclerostin （SOST）, a secreted Wnt antagonist, is notably reduced in the Bmprla- deficient osteocytes, we have genetically tested the hypothesis that increased Wnt signaling might mediate the increase in cancellous bone formation in response to Bmprla deletion. Forced expression of human SOST from a Dmpl promoter fragment partially rescues preosteoblast hyperproliferation and cancellous bone overgrowth in the Bmprla mutant mice, demonstrating functional interaction between Bmp and Wnt signaling in the cancellous bone compat^a-tent. To test whether increased Wnt signaling can compensate for the defect in periosteal growth caused by Bmprla deletion, we have generated compound mutants harboring a hyperactive mutation （A214V） in the Wnt receptor Lrp5. However, the mutant Lrp5 does not restore periosteal bone growth in the Bmprla-deficient mice. Thus, Bmp signaling restricts cancellous bone accrual partly through induction of SOST that limits preosteoblast proliferation, but promotes periosteal bone growth apparently independently of Wnt activation.

AFF1 and AFF4 differentially regulate the osteogenic differentiation of human MSCs

AFF1 and AFF4 belong to the AFF （AF4/FMR2） family of proteins, which function as scaffolding proteins linking two different transcription elongation factors, positive elongation factor b （P-TEFb） and ELL1/2, in super elongation complexes （SECs）. Both AFF1 and AFF4 regulate gene transcription through elongation and chromatln remodeling. However, their function in the osteogenic differentiation of mesenchymal stem cells （MSCs） is unknown. In this study, we show that small interfering RNA （siRNA）-mediated depletion of AFF1 in human MSCs leads to increased alkaline phosphatase （ALP） activity, enhanced mineralization and upregulated expression of osteogenic-related genes. On the contrary, depletion of AFF4 significantly inhibits the osteogenic potential of MSCs. In addition, we confirm that overexpression of AFF1 and AFF4 differentially affects osteogenic differentiation in vitro and MSC-mediated bone formation in vivo. Mechanistically, we find that AFFI regulates the expression of DKK1 via binding to its promoter region. Depletion of DKK1 in HA-AFFl-overexpressing MSCs abrogates the impairment of osteogenic differentiation. Moreover, we detect that AFF4 is enriched in the promoter region of ID1. AFF4 knockdown blunts the BRE luciferase activity, SP7 expression and ALP activity induced by BMP2 treatment. In conclusion, our data indicate that AFF1 and AFF4 differentially regulate the osteogenic differentiation of human MSCs.AFF1 and AFF4 belong to the AFF （AF4/FMR2） family of proteins, which function as scaffolding proteins linking two different transcription elongation factors, positive elongation factor b （P-TEFb） and ELL1/2, in super elongation complexes （SECs）. Both AFFI and AFF4 regulate gene transcription through elongation and chromatln remodeling. However, their function in the osteogenic differentiation of mesenchymal stem cells （MSCs） is unknown. In this study, we show that small interfering RNA （siRNA）-mediated depletion of AFF1 in human MSCs leads to increased alkaline phosphatase （ALP） activity, enhanced mineralization and upregulated expression of osteogenic-related genes. On the contrary, depletion of AFF4 significantly inhibits the osteogenic potential of MSCs. In addition, we confirm that overexpression of AFF1 and AFF4 differentially affects osteogenic differentiation in vitro and MSC-mediated bone formation in vivo. Mechanistically, we find that AFFI regulates the expression of DKK1 via binding to its promoter region. Depletion of DKK1 in HA-AFFl-overexpressing MSCs abrogates the impairment of osteogenic differentiation. Moreover, we detect that AFF4 is enriched in the promoter region of ID1. AFF4 knockdown blunts the BRE luciferase activity, SP7 expression and ALP activity induced by BMP2 treatment. In conclusion, our data indicate that AFF1 and AFF4 differentially regulate the osteogenic differentiation of human MSCs.

RANKL-RANK signaling regulates osteoblast differentiation and bone formation

In the recent two decades, it has been well elucidated that receptor activator of nuclear factor-κB ligand （RANKL; also known as TNFSF11） binding to its receptor RANK （also known as TNFRSF11A） drives osteoclast development as the crucial signaling pathway.;However, accumulating evidence also implies that

Alpl prevents bone ageing sensitivity by specifically regulating senescence and differentiation in mesenchymal stem cells

Mutations in the liver/bone/kidney alkaline phosphatase(Alpl) gene cause hypophosphatasia(HPP) and early-onset bone dysplasia,suggesting that this gene is a key factor in human bone development. However, how and where Alpl acts in bone ageing is largely unknown. Here, we determined that ablation of Alpl induces prototypical premature bone ageing characteristics, including bone mass loss and marrow fat gain coupled with elevated expression of p16INK4A(p16) and p53 due to senescence and impaired differentiation in mesenchymal stem cells(MSCs). Mechanistically, Alpl deficiency in MSCs enhances ATP release and reduces ATP hydrolysis. Then, the excessive extracellular ATP is, in turn, internalized by MSCs and causes an elevation in the intracellular ATP level, which consequently inactivates the AMPKα pathway and contributes to the cell fate switch of MSCs. Reactivating AMPKα by metformin treatment successfully prevents premature bone ageing in Alpl+/-mice by improving the function of endogenous MSCs.These results identify a previously unknown role of Alpl in the regulation of ATP-mediated AMPKα alterations that maintain MSC stemness and prevent bone ageing and show that metformin offers a potential therapeutic option.

miR-23a/b regulates the balance between osteoblast and adipocyte differentiation in bone marrow mesenchymal stem cells

Age-related osteoporosis is associated with the reduced capacity of bone marrow mesenchymal stem cells （BMSCs） to differentiate into osteoblasts instead of adipocytes. However, the molecular mechanisms that decide the fate of BMSCs remain unclear. In our study, microRNA-23a, and microRNA-23b （miR-23a/b） were found to be markedly downregulated in BMSCs of aged mice and humans. The overexpression of miR-23a/b in BMSCs promoted osteogenic differentiation, whereas the inhibition of miR-23a/b increased adipogenic differentiation. Transmembrane protein 64 （Tmem64）, which has expression levels inversely related to those of miR-23a/b in aged and young mice, was identified as a major target of miR-23a/b during BMSC differentiation. In conclusion, our study suggests that miR-23a/b has a critical role in the regulation of mesenchymal lineage differentiation through the suppression of Tmem64.

circ_0003204 regulates the osteogenic differentiation of human adipose-derived stem cells via miR-370-3p/HDAC4 axis

Human adipose-derived stem cells(hASCs)are a promising cell type for bone tissue regeneration.Circular RNAs(circRNAs)have been shown to play a critical role in regulating various cell differentiation and involve in mesenchymal stem cell osteogenesis.However,how circRNAs regulate hASCs in osteogenesis is still unclear.Herein,we found circ_0003204 was significantly downregulated during osteogenic differentiation of hASCs.Knockdown of circ_0003204 by si RNA or overexpression by lentivirus confirmed circ_0003204 could negatively regulate the osteogenic differentiation of hASCs.We performed dual-luciferase reporting assay and rescue experiments to verify circ_0003204 regulated osteogenic differentiation via sponging miR-370-3p.We predicted and confirmed that miR-370-3p had targets in the 3′-UTR of HDAC4 m RNA.The following rescue experiments indicated that circ_0003204 regulated the osteogenic differentiation of hASCs via miR-370-3p/HDAC4 axis.Subsequent in vivo experiments showed the silencing of circ_0003204 increased the bone formation and promoted the expression of osteogenic-related proteins in a mouse bone defect model,while overexpression of circ_0003204 inhibited bone defect repair.Our findings indicated that circ_0003204 might be a promising target to promote the efficacy of hASCs in repairing bone defects.

Correlation between receptor-interacting protein 140 expression and directed differentiation of human embryonic stem cells into neural stem cells

Overexpression of receptor-interacting protein 140（RIP140） promotes neuronal differentiation of N2 a cells via extracellular regulated kinase 1/2（ERK1/2） signaling.However,involvement of RIP140 in human neural differentiation remains unclear.We found both RIP140 and ERK1/2 expression increased during neural differentiation of H1 human embryonic stem cells.Moreover,RIP140 negatively correlated with stem cell markers Oct4 and Sox2 during early stages of neural differentiation,and positively correlated with the neural stem cell marker Nestin during later stages.Thus,ERK1/2 signaling may provide the molecular mechanism by which RIP140 takes part in neural differentiation to eventually affect the number of neurons produced.

Biomechanical forces in atherosclerosis-susceptible and -resistant regions of human vasculature differentially regulate endothelial vaso-protective phenotypes

Introduction Atherosclerosis is a potentially life-threatening disease of large arteries that is strongly associated with systemic risk factors such as hypercholesterolemia,hypertension,smoking,and diabetes. However,atherosclerosis develops as a

Restructuring and differentiated regulatory policies in China’s petroleum industry

China’s petroleum industry is monopolistic in its main business activities.However,the reasonability of this monopoly needs to be discussed according to its technical and economic characters.Research results show that the petroleum pipeline transportation business is naturally monopolistic while other businesses are competitive.Those business activities which can be open to competition but are in fact monopolistic are so owing to administrative order,and run inefficiently as a consequence.In order to improve productive efficiency and reduce efficiency losses,we propose three restructuring patterns of the petroleum industry-the Access Control Model,the Ownership Separation Model,and the Mutual-benefit Network Model.These three models have both advantages and disadvantages.Considering the prevailing practices in the petroleum industry in China,we think that the best choice is the Access Control Model.In order to improve restructuring effects of regulatory patterns,we design three differentiated regulatory policies,including differentiated entry regulation policies,differentiated price regulation policies,and differentiated distribution of different ownership enterprises policies.

Molecular regulation of development and differentiation in Streptomyces

Development and differentiation is an important and leading research field in modern biology. Streptomyces has a complicated life cycle of morphological differentiation including the spore germination, aerial mycelium and spore formation. Each developmental stage has a distinguished morphological feature which greatly facilitates the identification of developmental mutants, the complementary cloning and the spatial and temporal expression of the genes involved in differentiation. This characteristic of Streptomyces is comparatively superior to other pro-karyotic bacteria such as Escherichia coli, Bacillus sub-tilis and Myxococcus xanthus. Moreover, Streptomyces also possesses a complicated physiological differentiation in which it produces a wide variety of secondary metabolites (more than half of the 12 000 or so known antibiotics), including many important antibiotics used in medi-