Canine mesenchymal stem cells are effectively labeled with silica nanoparticles and unambiguously visualized in highly autofluorescent tissues

We examined the effect of silica nanoparticle labeling on stem cell morphology, viability and differentiation as compared with those of unlabeled control cells. After 4？h of incubation with silica nanoparticles, they were internalized by canine MSCs without a change in the morphology of cells compared with that of control cells. The viability and proliferation of MSCs labeled with silica nanoparticles were evaluated by a WST-1 assay and trypan blue exclusion. No effects on cell viability were observed, and the proliferation of canine MSCs was not inhibited during culture with silica nanoparticles. Furthermore, adipogenic and osteogenic differentiation of silica nanoparticle-labeled canine MSCs was at a similar level compared with that of unlabeled cells, indicating that silica nanoparticle labeling did not alter the differentiation capacity of canine MSCs. Silica nanoparticle-labeled canine MSCs were injected into the kidneys of BALB/c mice after celiotomy, and then the mice were sacrificed after 2 or 3？weeks. The localization of injected MSCs was closely examined in highly autofluorescent renal tissues. Histologically, canine MSCs were uniformly and completely labeled with silica nanoparticles, and were unambiguously imaged in histological sections.The results of the current study showed that silica nanoparticles are useful as an effective labeling marker for MSCs, which can elucidate the distribution and fate of transplanted MSCs.Adult mesenchymal stem cells (MSCs) are a cellular tool with promising application in both veterinary and human medicine. MSCs have the potential to repair tissues [1-4] and improve the function of damaged organs. Thus, many clinical trials are in progress to evaluate the therapeutic potentials of MSCs for treating renal failure, diabetes mellitus and heart failure [5-9].Tracking of stem cells is essential for evaluating cell replacement and therapeutic strategies [10]. In addition, long-term labeling of stem cells is critical to elucidat