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Recent studies have demonstrated that erythropoietin (EPO) has extensive nonhematopoietic biological functions. However, little is known about how EPO regulates bone formation, although several studies suggested that EPO can affect bone homeostasis. In this study, we investigated the effects of EPO on the communication between osteoclasts and osteoblasts through the ephrinB2/EphB4 signaling pathway. We found that EPO slightly promotes osteoblastic differentiation with the increased expression of EphB4 in ST2 cells. However, EPO increased the expression of Nfatc1 and ephrinB2 but decreased the expression of Mmp9 in RAW264.7 cells, resulting in an increase of ephrinB2-expressing osteoclasts and a decrease in resorption activity. The stimulation of ephrinB2/EphB4 signaling via ephrinB2-Fc significantly promoted EPO-mediated osteoblastic differentiation in ST2 cells. EphB4 knockdown through EphB4 shRNA inhibited EPO-mediated osteoblastic phenotypes. Furthermore, in vivo assays clearly demonstrated that EPO efficiently induces new bone formation in the alveolar bone regeneration model. Taken together, these results suggest that ephrinB2/EphB4 signaling may play an important role in EPO-mediated bone formation.

We present a systematic study of low-frequency noise in Au nanoparticle chemosensors. All the sensors we have studied exhibit 1∕f-type noise at low frequencies. The magnitude of the 1∕f noise was smaller in devices with a larger device area, indicating that the 1∕f noise is caused by intrinsic processes. The noise amplitude was found to be strongly temperature dependent between 40–300K, with a local peak at around 100K, and weakly dependent below 40K. The noise data could not be fit by a single activated process indicating that multiple noise processes must be present in our sensors.

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