No abstract

Stem cell transplantation is emerging as a potential treatment option for acute renal failure (ARF) because of its capability to regenerate tissues and organs. To better understand the mechanism of cell therapy, in vivo tracking cellular dynamics of the transplanted stem cells is needed. In the present study, in vivo monitored magnetically labeled mesenchymal stem cells (MSCs) were transplanted intravascularly into an ARF rat model using a conventional magnetic resonance imaging (MRI) system. Rat bone marrow MSCs were labeled with home synthesized Fe 2 O 3 -PLL, and labeled (n = 6) or unlabeled MSCs (n = 6) were injected into the renal arteries of the rats with ARF induced by the intramuscular injection of glycerol. Using the same technique, labeled MSCs were also injected into the rats assigned to a control group (n = 8). MR images of kidneys were obtained before injection of MSCs as well as immediately, 1, 3, 5, and 8 days afterwards. MR findings were analyzed and compared with histopathological and immunohistochemical results. These results showed that the rat MSCs were successfully labeled with the home synthesized Fe 2 O 3 -PLL. In both renal failure and intact rat models, the labeled MSCs demonstrated a loss of signal intensity in the renal cortex on T2*-weighted MR images, which was visible up to 8 days after transplantation. Histological analyses showed that most of the labeled MSCs that tested positive for Prussian blue staining were in glomerular capillaries, corresponding to the areas where a loss in signal intensity was observed in the MRI. A similar signal intensity decrease was not detected in the rats with unlabeled cells. These data demonstrate that the magnetically labeled MSCs in the rat model of ARF were successfully evaluated in vivo by a 1.5 T MRI system, showing that the mechanisms of stem cell therapy have great potential for future ARF treatment recipients.

Tumor hypoxia is an important reason for the limited therapeutic efficacy of photodynamic therapy (PDT) because of the oxygen requirement of the therapeutic process. PDT consumes tissue oxygen and destroys tumor vasculature, further hampering its own efficacy in promoting tumor deterioration. Therefore, overcoming the photodynamic exacerbation of tumor hypoxia is urgent.Methods: Herein, we report a photodynamic nanoparticle with sustainable hypoxia remission skills by both intratumoral H2O2 catalysis and targeted mitochondrial destruction. The Mn3O4@MSNs@IR780 nanoparticles are formed by absorbing a photosensitizer (IR780) into 90 nm mesoporous silica nanoparticles (MSNs) and capping the surface pores with 5 nm Mn3O4 nanoparticles.Results: These Mn3O4 nanoparticles can accumulate in tumors and respond to the H2O2-enriched tumor microenvironment by decomposing and catalyzing H2O2 into O2. Afterwards, IR780 is released and activated, spontaneously targeting the mitochondria due to its natural mitochondrial affinity. Under laser irradiation, this self-generated oxygen-enhanced PDT can destroy mitochondria and inhibit cell respiration, resulting in sustainable hypoxia remission in tumor tissues and consequently enhancing the therapeutic outcome. In vitro experiments suggest that Mn3O4@MSNs@IR780 exhibited highly mitochondrion-targeted properties and could sustainably inhibit tumor hypoxia. Additionally, the highest photoacoustic signal of HbO2 with the lowest Hb was observed in tumors from mice after PDT, indicating that these nanoparticles can also prevent tumor hypoxia in vivo.Conclusion: Taken together, our study indicated a new approach for overcoming the sustainable hypoxia limitation in traditional PDT by targeted oxygen supplementation and mitochondria destruction.

The effect of mesenchymal stem cell (MSCs)-based therapy on treating acute myocardial infarction (MI) is limited due to poor engraftment and limited regenerative potential. Here we engineered MSCs with integrin-linked kinase (ILK), a pleiotropic protein critically regulating cell survival, proliferation, differentiation, and angiogenesis. We firstly combined ferumoxytol with poly-L-lysine (PLL), and found this combination promisingly enabled MRI visualization of MSCs in vitro and in vivo with good safety. We provided visually direct evidence that intracoronary ILK-MSCs had substantially enhanced homing capacity to infarct myocardium in porcine following cardiac catheterization induced MI. Intracoronary transplantation of allogeneic ILK-MSCs, but not vector-MSCs, significantly enhanced global left ventricular ejection fraction (LVEF) by 7.8% compared with baseline, by 10.3% compared with vehicles, and inhibited myocardial remodeling compared with vehicles at 15-day follow-up. Compared with vector-MSCs, ILK-MSCs significantly improved regional LV contractile function, reduced scar size, fibrosis, cell apoptosis, and increased regional myocardial perfusion and cell proliferation. This preclinical study indicates that ILK-engineered MSCs might promote the clinical translation of MSC-based therapy in post-MI patients, and provides evidence that ferumoxytol labeling of cells combined with PLL is feasible in in vivo cell tracking.

Magnetic resonance imaging (MRI) has proven to be effective in tracking the distribution of transplanted stem cells to target organs by way of labeling cells with superparamagnetic iron oxide particles (SPIO). However, the effect of SPIO upon labeled cells is still unclear on a cellular level. With this study, the proliferation and viability of New Zealand rabbit peripheral blood endothelial progenitor cells (EPCs) labeled with SPIO were evaluated and in vitro images were obtained using a 1.5 T MR scanner. Mononuclear cells (MNCs) were isolated from peripheral blood of the adult New Zealand rabbit and cultured in fibronectin-coated culture flasks, in which EPCs were identified from cell morphology, outgrowth characteristics, and internalization of DiI-Ac-LDL and binding to FITC-UEA I. EPCs were incubated with the self-synthesized poly-L-lysine-conjugated SPIO (PLL-SPIO) particles in a range of concentrations. The prevalence of iron-containing vesicles or endosomes in the cytoplasm of labeled cells was confirmed with Prussian blue staining and transmission electron microscopy. Tetrazolium salt (MTT) assay, cell apoptosis, and cycle detection were assessed to evaluate proliferation and function of various concentrations, magnetically labeled EPCs. The quantity of iron per cell was determined by atomic absorption spectrometry. The cells underwent MRI with different sequences. The result showed that rabbit EPCs were efficiently labeled with the home synthesized PLL-SPIO. There was found to be no statistically significant difference in the MTT values of light absorption measured on the third and fifth days. Between labeled and unlabeled cells, there were also no aberrations found in the cell cycles, apoptosis, or growth curves. The atomic absorption spectrophotometer showed that the intracellular content of Fe decreased as more time elapsed after labeling. The labeled EPCs demonstrated a loss of MRI signal intensity (SI) when compared with the SI of unlabeled cells. These signal changes (ASI) were visible when cells were labeled with more than 5 x 104/ml of SPIO. The change in SI corresponded to the amount of iron in the EPCs, which reached a maximum at T2*WI. These data demonstrate that EPCs from the peripheral blood of the New Zealand rabbit can be effectively labeled with self-synthesized PLL-SPIO with minimal effects on cell proliferation and activity. Magnetically labeled EPCs can be imaged at 1.5 T MR and can therefore be used as an MR tracker of implanted EPCs.