Extracellular Vesicle microRNAs Contribute to the Osteogenic Inhibition of Mesenchymal Stem Cells in Multiple Myeloma

Abstract

Osteolytic bone disease is the major complication associated with the progression of multiple myeloma (MM). Recently, extracellular vesicles (EVs) have emerged as mediators of MM-associated bone disease by inhibiting the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Here, we investigated a correlation between the EV-mediated osteogenic inhibition and MM vesicle content, focusing on miRNAs. By the use of a MicroRNA Card, we identified a pool of miRNAs, highly expressed in EVs, from MM cell line (MM1.S EVs), expression of which was confirmed in EVs from bone marrow (BM) plasma of patients affected by smoldering myeloma (SMM) and MM. Notably,we found that miR-129-5p, which targets different osteoblast (OBs) differentiation markers, is enriched in MM-EVs compared to SMM-EVs, thus suggesting a selective packaging correlated with pathological grade. We found that miR-129-5p can be transported to hMSCs by MM-EVs and, by the use of miRNA mimics, we investigated its role in recipient cells. Our data demonstrated that the increase of miR-129-5p levels in hMSCs under osteoblastic differentiation stimuli inhibited the expression of the transcription factor Sp1, previously described as a positive modulator of osteoblastic differentiation, and of its target the Alkaline phosphatase (ALPL), thus identifying miR-129-5p among the players of vesicle-mediated bone disease.

Exosomes in the Pathogenesis and Treatment of Multiple Myeloma in the Context of the Bone Marrow Microenvironment

“…LncRNA RUNX2 antisense RNA 1 (RUNX2-AS1), amphiregulin, and miR-129-5p were identified to be specifically enriched in MM-EXs. Upon internalization of the exosomes by MSC, these molecules reduced RUNX2 splicing efficiency, activated the epidermal EGFR pathway, and downregulated the expression of the transcription factor Sp1, respectively ( 37 – 39 ). Each pathway has been demonstrated to decrease the osteogenic potential of MSCs, increase osteoclastogenesis, and contribute to osteoblast deficiency.…”

Emerging Insights on the Biological Impact of Extracellular Vesicle-Associated ncRNAs in Multiple Myeloma

“…In recent years, increasing evidence has shown that EVs, and specifically their ncRNA content, are responsible for the onset of bone disease since they can promote osteoclast activation and inhibit the osteogenic differentiation of mesenchymal stem cells (MSCs) [75][76][77][78][79].…”

“…Similarly, in a recent study, we identified a panel of miRNAs packed in MM-EVs from MM cell lines or primary plasma cells from bone marrow aspirates that can negatively regulate osteogenesis [79]. Among them, we identified and characterized miR-129-5p, which targets various mRNAs involved in osteoblast differentiation [81][82][83][84].…”

“…Among them, we identified and characterized miR-129-5p, which targets various mRNAs involved in osteoblast differentiation [81][82][83][84]. Moreover, we observed that this miRNA is transferred to MSCs by MM-EVs, causing a downregulation of SP-1, a transcription factor implicated in osteogenesis through the targeting of alkaline phosphatase (ALPL) [79] and also involved in MM cell proliferation [85].…”

“…In our recent study, we found higher levels of miR-129-5p in vesicles isolated from the bone marrow of MM patients than in SMM [79]; since this miRNA targets different mRNAs involved in osteoblast differentiation [81][82][83][84], its presence in plasma EVs could be relevant to discriminate between the two pathological conditions.…”