Bone is not a static tissue. It is constantly remodeled, broken down by osteoclast cells and built up by osteoblast cells. The loss of bone mass and strength with age, osteoporosis, is the result of an imbalance in the activities of osteoclasts and osteoblasts, too much destruction and too little creation. This imbalance, as for all aspects of aging, is the result of many deeper overlapping layers of cause and effect, not fully mapped and understood. Thus most approaches to therapy tend to involve ways to force greater activity of osteoblasts or suppress the activity of osteoclasts, rather than delving in search of root causes. The open access paper here is an example of this type of work, outlining an approach to stimulate greater osteoblast activity in mice.
In recent years, promising therapeutic approaches to treat osteoporosis are mainly focused on targeting the functions of skeletal stem cells and osteoblasts. A more detailed understanding of bone biology has led to the identification of novel therapeutic targets with enhanced molecular insights into the communication between bone-forming osteoblasts and bone-resorbing osteoclasts as well as the orchestrating signaling network. Thus, it is necessary to develop new approaches to stimulate osteoblast activity. In the present study, we demonstrate that bone marrow stem cell (BMSC) derived exosomes carrying the long non-coding RNA (lncRNA) MALAT1 could effectively stimulate the osteoblast activity. Our results highlighted the potential of exosomal MALAT1 to prevent osteoporosis in mouse models.
A key finding of the current study indicated that BMSCs-derived exosomal MALAT1 could potentially promote osteoblast activity. Exosomes could actively transport and transfer information between miRNAs, proteins, and mRNAs to target cells, thus affecting their behaviors and strongly modifying the entire microenvironment. Consistent with previous reports, we observed the protective role of exosome-mediated delivery of MALAT1 in disease. Furthermore, we detected that the upregulation of MALAT1 could attenuate the symptoms of osteoporosis in mice. Existing literature has suggested that lncRNAs play critical roles in the initiation and pathogenesis of osteoporosis. For instance, a recent study demonstrated that lncRNA MEG3 suppressed the osteogenic differentiation of mesenchymal stem cells in postmenopausal osteoporosis.
Our study provides evidence that BMSC-derived exosomal MALAT1 may contribute to enhanced osteogenic activity and alleviated symptoms of osteoporosis in the mouse model by acting as a miR-34c sponge to upregulate SATB2 expression. These results provide a broader understanding of the pathogenesis of osteoporosis as well as novel therapeutic strategies for its treatment.