Exosomes are a heterogeneous group of cell-derived membranous structures, which mediate crosstalk interaction between cells. Recent studies have revealed a close relationship between exosomes and bone homeostasis. It is suggested that bone cells can spontaneously secret exosomes containing proteins, lipids and nucleic acids, which then to regulate osteoclastogenesis and osteogenesis. However, the network of regulatory activities of exosomes in bone homeostasis as well as their therapeutic potential in bone injury remain largely unknown. This review will detail and discuss the characteristics of exosomes, the regulatory activities of exosomes in bone homeostasis as well as the clinical potential of exosomes in bone injury.

Indo-Pacific humpback dolphins (Sousa chinensis) live in coastal waters that have experienced considerable anthropogenic disturbances. Specifically, along the coasts of highly urbanized regions, available habitats have decreased in both space and scale. This study used Maxent software to simulate the distribution of suitable habitats for S. chinensis during the dry and wet seasons in Xiamen Bay. We also aimed to identify key environmental factors influencing habitat distribution, with the goal of using our results to analyze conservation gaps and propose adjustments. We found that during the dry season, S. chinensis were mainly distributed in the Western Harbor, Jiulong River Estuary, and the mouth of Tongan Bay. During the wet season, they were distributed in the south of Western Harbor, Jiulong River Estuary, and around the Wuyu and Dadeng-Xiaodeng Islands. Nekton density, chlorophyll-a concentration, sea surface temperature, slope, and salinity are the primary factors affecting S. chinensis distribution in Xiamen Bay. To better protect the species, the existing Tongan Bay reserve should be expanded during dry seasons, and suitable habitats in the Jiulong River Estuary should be turned into a seasonal protected region. Similarly, during wet seasons, the original Western Harbor portion of the reserve should increase to include the Jiulong River Estuary, northwest of the Wuyu Islands and south of the Dadeng-Xiaodeng Islands. In addition to this dynamic seasonal management of reserve size, we also recommend developing multiple-use protected areas and establishing a joint protection mechanism between local governments. In conclusion, our model offers important guidance on improving conservation measures of S. chinensis in Xiamen Bay.

Osteocytes are the terminally differentiated bone cells resulted from bone formation. Although there are two distinct processes of bone formation, intramembranous and endochondral ossifications contributing to the formation of calvarial and long bones, it is not clear whether the distinct pathways determine the differences between calvaria and femoral cortical bone derived osteocytes. In the present study, we employed confocal structured illumination microscopy and mRNA‐sequencing analysis to characterize the morphologic and transcriptomic expression of osteocytes from murine calvaria and mid‐shaft femoral cortical bone. Structured illumination microscopy and geometric modelling showed round shaped and irregularly scattered calvarial osteocytes compared to spindle shaped and orderly arrayed cortical osteocytes. mRNA‐sequencing analysis indicated different transcriptomic profiles between calvarial and cortical osteocytes and provided evidence that mechanical response of osteocytes may contribute to geometrical differences. Furthermore, transcriptomic analysis showed that these two groups of osteocytes come from distinct pathways with 121 ossification‐related genes differentially expressed. Analysis of correlation between ossification and osteocyte geometries via a Venn diagram showed that several genes related to ossification, cytoskeleton organization and dendrite development were differentially expressed between calvarial and cortical osteocytes. Finally, we demonstrated that aging disrupted the organization of dendrites and cortical osteocytes but had no significant effects on calvarial osteocytes. Together, we conclude that calvarial and cortical osteocytes are different in various aspects, which is probably the consequence of their distinct pathways of ossification.

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