RNA interference-mediated gene regulation in stem cells offers great potential in regenerative medicine. In this study, we developed a theranostic platform for efficient delivery of small RNAs [small interfering RNA (siRNA)/microRNA (miRNA)] to human mesenchymal stem cells (hMSCs) to promote differentiation, and meanwhile, to specifically label the transfected cells for the in vivo tracking purpose. We encapsulated indocyanine green (ICG) in a nonionic surfactant vesicle, termed "niosome", that is mainly composed of a nonionic surfactant sorbitan monooleate (Span 80) and a cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). This novel ICG-containing niosome system (iSPN) demonstrated highly efficient siRNA and miRNA delivery in hMSCs. Specific inhibition of miR-138, a negative regulator of osteoblast differentiation, was achieved by iSPN/miR-138, which significantly promoted osteogenesis of hMSCs. Furthermore, iSPN exhibited OFF/ON activatable fluorescence upon cellular internalization, resulting in efficient near-infrared labeling and the capability to dynamically monitor stem cells in mice. In addition, iSPN/siRNA achieved simultaneous long-term cell tracking and in vivo gene silencing after implantation in mice. These results indicate that our theranostic niosomes could represent a promising platform for future development of stem cell-based therapy.

Long noncoding RNAs (lncRNAs), which serve as important and powerful regulators of various biological activities, have gained widespread attention in recent years. Emerging evidence has shown that some lncRNAs play important regulatory roles in osteoblast differentiation of mesenchymal stem cells (MSCs), suggesting a potential therapeutic strategy for bone fracture. As a recently identified lncRNA, linc-ROR was reported to mediate the reprogramming ability of differentiated cells into induced pluripotent stem cells (iPSCs) and human embryonic stem cells (ESCs) self-renewal. However, other functions of linc-ROR remain elusive. In this study, linc-ROR was found to be upregulated during osteogenesis of human bone-marrow-derived MSCs. Ectopic expression of linc-ROR significantly accelerated, whereas knockdown of linc-ROR suppressed, osteoblast differentiation. Using bioinformatic prediction and luciferase reporter assays, we demonstrated that linc-ROR functioned as a microRNA (miRNA) sponge for miR-138 and miR-145, both of which were negative regulators of osteogenesis. Further investigations revealed that linc-ROR antagonized the functions of these two miRNAs and led to the de-repression of their shared target ZEB2, which eventually activated Wnt/β-catenin pathway and hence potentiated osteogenesis. Taken together, linc-ROR modulated osteoblast differentiation by acting as a competing endogenous RNA (ceRNA), which may shed light on the functional characterization of lncRNAs in coordinating osteogenesis.