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BackgroundHuman adipose-derived stromal cells (hASCs) represent a multipotent cell stromal cell type with proven capacity to differentiate along an osteogenic lineage. This suggests that they may be used to heal defects of the craniofacial or appendicular skeleton. We sought to substantiate the use of undifferentiated hASCs in the regeneration of a non-healing mouse skeletal defect.Methodology/Principal FindingsHuman ASCs were harvested from female lipoaspirate. Critical-sized (4 mm) calvarial defects were created in the parietal bone of adult male nude mice. Defects were either left empty, treated with an apatite coated PLGA scaffold alone, or a scaffold with human ASCs. MicroCT scans were obtained at stratified time points post-injury. Histology, in situ hybridization, and histomorphometry were performed. Near complete healing was observed among hASC engrafted calvarial defects. This was in comparison to control groups that showed little healing (*P<0.01). Human ASCs once engrafted differentiate down an osteogenic lineage, determined by qRT-PCR and histological co-expression assays using GFP labeled cells. ASCs were shown to persist within a defect site for two weeks (shown by sex chromosome analysis and quantified using Luciferase+ ASCs). Finally, rBMP-2 was observed to increase hASC osteogenesis in vitro and osseous healing in vivo.Conclusions/SignificanceHuman ASCs ossify critical sized mouse calvarial defects without the need for pre-differentiation. Recombinant differentiation factors such as BMP-2 may be used to supplement hASC mediated repair. Interestingly, ASC presence gradually dissipates from the calvarial defect site. This study supports the potential translation for ASC use in the treatment of human skeletal defects.

The study of the chemical and biological properties of CeO2 NPs (CNPs) has expanded recently due to its therapeutic potential, and the methods used to synthesize these materials are diverse. Moreover, conflicting reports exists regarding the toxicity of CNP. To help resolve these discrepancies, we must first determine whether CeO2 NPs made by different methods are similar or different in their physiochemical and catalytic properties. In this paper, we have synthesized several forms of CNPs using identical precursors through a wet chemical process but using different oxidizer/reducer H2O2 (CNP1), NH4OH (CNP2) or hexamethylenetetramine (HMT-CNP1). Physiochemical properties of these CeO2 NPs were extensively studied and found to be different depending on the preparation methods. Unlike CNP1 and CNP2, HMT-CNP1 were readily taken into endothelial cells and their aggregation can be visualized using light microscopy. Exposure to HMT-CNP1 also reduced cell viability (MTT) at a 10-fold lower concentration than CNP1 or CNP2. Surprisingly, exposure to HMT-CNP1 led to substantial decreases in the ATP levels. Mechanistic studies revealed that HMT-CNP1 exhibited substantial ATPase (phosphatase) activity. Though CNP2 also exhibits ATPase activity, CNP1 lacked ATPase activity. The difference in catalytic (ATPase) activity of different CeO2 NPs preparation may be due to differences in their morphology and oxygen extraction energy. These results suggest the combination of increased uptake and ATPase activity of HMT-CNP1 may underlie the biomechanism of the toxicity of this preparation of CNPs, and may suggest ATPase activity should be considered when synthesizing CNPs for use in biomedical applications.

Nanotechnology is becoming an important field of biomedical and clinical research and the application of nanoparticles in disease may offer promising advances in treatment of many diseases, especially cancer. Malignant melanoma is one of the most aggressive forms of cancer and its incidence is rapidly increasing. Redox-active cerium oxide nanoparticles (CNP) are known to exhibit significant antitumor activity in cells derived from human skin tumors in vitro and in vivo, whereas CNP is nontoxic and beyond that even protective (antioxidative) in normal, healthy cells of the skin. As the application of conventional chemotherapeutics is associated with harmful side effects on healthy cells and tissues, the clinical use is restricted. In this study, we addressed the question of whether CNP supplement a classical chemotherapy, thereby enhancing its efficiency without additional damage to normal cells. The anthracycline doxorubicin, one of the most effective cancer drugs, was chosen as reference for a classical chemotherapeutic agent in this study. Herein, we show that CNP enhance the antitumor activity of doxorubicin in human melanoma cells. Synergistic effects on cytotoxicity, reactive oxygen species generation, and oxidative damage in tumor cells were observed after co-incubation. In contrast to doxorubicin, CNP do not cause DNA damage and even protect human dermal fibroblasts from doxorubicin-induced cytotoxicity. A combination of classical chemotherapeutics with nongenotoxic but antitumor active CNP may provide a new strategy against cancer by improving therapeutic outcome and benefit for patients.