Background: As a hallmark driver of multiple myeloma (MM), MM bone disease (MBD) is unique in that it is characterized by severely impaired osteoblast activity resulting from blocked osteogenesis in bone marrow-derived mesenchymal stem cells (BM-MSCs). The mechanisms underlying this preferential blockade are incompletely understood.Methods: miRNA expression of MM cell-derived extracellular vesicles (MM-EVs) was detected by RNA sequencing. MM-EVs impaired osteogenesis and exacerbated MBD were in vitro and in vivo validated by histochemical staining, qPCR and micro-CT. We additionally examined the correlation between CD138+ circulating EVs (cirEVs) count and bone lesion in de novo MM patients.Results: Here, by sequencing and bioinformatics analysis, we found that MM-EVs were enriched in various molecules negatively regulating osteogenesis. We experimentally verified that MM-EVs inhibited BM-MSC osteogenesis, induced elevated expression of miR-103a-3p inhibiting osteogenesis in BM-MSCs, and increased cell viability and interleukin-6 secretion in MM cells. In a mouse model, MM-EVs that were injected into the marrow space of the left tibia led to impaired osteogenesis and exacerbated MBD and MM progression. Furthermore, the levels of CD138+ cirEVs in the peripheral blood were positively correlated with the number of MM bone lesions in MM patients.Conclusions: These findings suggest that MM-EVs play a pivotal role in the development of severely impaired osteoblast activity, which represents a novel biomarker for the precise diagnosis of MBD and a compelling rationale for exploring MM-EVs as a therapeutic target.

Insect fat body is the organ for intermediary metabolism, comparable to vertebrate liver and adipose tissue. Larval fat body is disintegrated to individual fat body cells and then adult fat body is remodeled at the pupal stage. However, little is known about the dissociation mechanism. We find that the moth Helicoverpa armigera cathepsin L (Har-CL) is expressed heavily in the fat body and is released from fat body cells into the extracellular matrix. The inhibitor and RNAi experiments demonstrate that Har-CL functions in the fat body dissociation in H. armigera. Further, a nuclear protein is identified to be transcription factor Har-Relish, which was found in insect immune response and specifically binds to the promoter of Har-CL gene to regulate its activity. Har-Relish also responds to the steroid hormone ecdysone. Thus, the dissociation of the larval fat body is involved in the hormone (ecdysone)-transcription factor (Relish)-target gene (cathepsin L) regulatory pathway.

Adenosine modulates various vascular functions such as vasodilatation and anti-inflammation. The local concentration of adenosine in the vicinity of adenosine receptors is fine tuned by 2 classes of nucleoside transporters: equilibrative nucleoside transporters (ENTs) and concentrative nucleoside transporters (CNTs). In vascular smooth muscle cells, 95% of adenosine transport is mediated by ENT-1 and the rest by ENT-2. In endothelial cells, 60%, 10%, and 30% of adenosine transport are mediated by ENT-1, ENT-2, and CNT-2, respectively. In vitro studies show that glucose per se increases the expression level of ENT-1 via mitogen-activating protein kinase-dependent pathways. Similar results have been demonstrated in diabetic animal models. Hypertension is associated with the increased expression of CNT-2. It has been speculated that the increase in the activities of ENT-1 and CNT-2 may reduce the availability of adenosine to adenosine receptors, thereby weakening the vascular functions of adenosine. This may explain why patients with diabetes and hypertension suffer greater morbidity from ischemia and atherosclerosis. No oral hypoglycemic agents can inhibit ENTs, but an exception is troglitazone (a thiazolidinedione that has been withdrawn from the market). ENTs are also sensitive to dihydropyridine-type calcium-channel blockers, particularly nimodipine, which can inhibit ENT-1 in the nanomolar range. Those calcium-channel blockers are noncompetitive inhibitors of ENTs, probably working through the reversible interactions with allosteric sites. The nonsteroidal anti-inflammatory drug sulindac sulfide is a competitive inhibitor of ENT-1. In addition to their original pharmacological actions, it is believed that the drugs mentioned above may regulate vascular functions through potentiation of the effects of adenosine.