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

TGF-β and BMP signaling in osteoblast,skeletal development,and bone formation,homeostasis and disease

INTRODUCTIONThe transforming growth factor-β （TGF-β） superfamily com- prises TGF-βs, Activin, bone morphogenetic proteins （BMPs） and other related proteins. TGF-β superfamily members act through a heteromeric receptor complex,, comprised of type I and type II receptors at the cell surface that transduce intracellular signals via Smad complex or mitogen-activated protein kinase （MAPK） cascade.

RANKL signaling in bone marrow mesenchymal stem cells negatively regulates osteoblastic bone formation

RANKL signaling is essential for osteoclastogenesis. Its role in osteoblastic differentiation and bone formation is unknown. Here we demonstrate that RANK is expressed at an early stage of bone marrow mesenchymal stem cells(BMSCs) during osteogenic differentiation in both mice and human and decreased rapidly. RANKL signaling inhibits osteogenesis by promoting β-catenin degradation and inhibiting its synthesis. In contrast, RANKL signaling has no significant effects on adipogenesis of BMSCs.Interestingly, conditional knockout of rank in BMSCs with Prx1-Cre mice leads to a higher bone mass and increased trabecular bone formation independent of osteoclasts. In addition, rank: Prx1-Cre mice show resistance to ovariectomy-(OVX) induced bone loss. Thus, our results reveal that RANKL signaling regulates both osteoclasts and osteoblasts by inhibition of osteogenic differentiation of BMSCs and promotion of osteoclastogenesis.

All-optical two-channel polarization-multiplexing format conversion from QPSK to BPSK signals in a silicon waveguide

All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit/s polarization multiplexing(Pol-MUX) non-return-to-zero quadrature phase-shift keying(QPSK) signal to Pol-MUX binary phase-shift keying(BPSK) signals by using phase-doubled four-wave mixing effects with two polarization-angled pumps in a silicon waveguide. The eye diagrams and constellation diagrams of the original QPSK sequences and the converted BPSK sequences of each channel are clearly observed on the two polarization states. Moreover,the bit error rates(BERs) of the two converted idlers are measured. The power penalties of all these converted BPSK sequences on both X and Y polarization states are less than 3.4 dB at a BER of 3.8 × 10^(-3).