[COVID-19: Collateral damage in head and neck oncology and preventive measures for future pandemics]. / COVID-19: Kollateralschäden in der Kopf-Hals-Onkologie und Präventivmaßnahmen für künftige Pandemien.

The start of the COVID-19 pandemic led to enormous challenges for global healthcare, as capacities and resources had to be made available quickly for the treatment of COVID-19 patients. As a result, restrictions had to be accepted, especially in the care of oncological patients. The collateral damage of these limitations inevitably also affects patients with head and neck cancer. This review article summarizes the development of tumor incidences during the pandemic, internationally developed guidelines for the care of patients with head and neck cancer and studies on the delay in oncological therapies and mortality. In addition, the effects on the mental health of the patients, the psychosocial consequences and ethical issues are examined. In perspective, preventive measures for such negative collateral effects in future pandemics are discussed using the example of a concept for application software (app)-based digital care for patients with head and neck cancer.

Differentiation Behaviour of Adipose-Derived Stromal Cells (ASCs) Seeded on Polyurethane-Fibrin Scaffolds In Vitro and In Vivo.

Adipose-derived stromal cells (ASCs) are a promising cell source for tissue engineering and regenerative medicine approaches for cartilage replacement. For chondrogenic differentiation, human (h)ASCs were seeded on three-dimensional polyurethane (PU) fibrin composites and induced with a chondrogenic differentiation medium containing TGF-ß3, BMP-6, and IGF-1 in various combinations. In addition, in vitro predifferentiated cell-seeded constructs were implanted into auricular cartilage defects of New Zealand White Rabbits for 4 and 12 weeks. Histological, immunohistochemical, and RT-PCR analyses were performed on the constructs maintained in vitro to determine extracellular matrix (ECM) deposition and expression of specific cartilage markers. Chondrogenic differentiated constructs showed a uniform distribution of cells and ECM proteins. RT-PCR showed increased gene expression of collagen II, collagen X, and aggrecan and nearly stable expression of SOX-9 and collagen I. Rabbit (r)ASC-seeded PU-fibrin composites implanted in ear cartilage defects of New Zealand White Rabbits showed deposition of ECM with structures resembling cartilage lacunae by Alcian blue staining. However, extracellular calcium deposition became detectable over the course of 12 weeks. RT-PCR showed evidence of endochondral ossification during the time course with the expression of specific marker genes (collagen X and RUNX-2). In conclusion, hASCs show chondrogenic differentiation capacity in vitro with the expression of specific marker genes and deposition of cartilage-specific ECM proteins. After implantation of predifferentiated rASC-seeded PU-fibrin scaffolds into a cartilage defect, the constructs undergo the route of endochondral ossification.

Superparamagnetic Iron Oxide Particles (VSOPs) Show Genotoxic Effects but No Functional Impact on Human Adipose Tissue-Derived Stromal Cells (ASCs).

Adipose tissue-derived stromal cells (ASCs) represent a capable source for cell-based therapeutic approaches. For monitoring a cell-based application in vivo, magnetic resonance imaging (MRI) of cells labeled with iron oxide particles is a common method. It is the aim of the present study to analyze potential DNA damage, cytotoxicity and impairment of functional properties of human (h)ASCs after labeling with citrate-coated very small superparamagnetic iron oxide particles (VSOPs). Cytotoxic as well as genotoxic effects of the labeling procedure were measured in labeled and unlabeled hASCs using the MTT assay, comet assay and chromosomal aberration test. Trilineage differentiation was performed to evaluate an impairment of the differentiation potential due to the particles. Proliferation as well as migration capability were analyzed after the labeling procedure. Furthermore, the labeling of the hASCs was confirmed by Prussian blue staining, transmission electron microscopy (TEM) and high-resolution MRI. Below the concentration of 0.6 mM, which was used for the procedure, no evidence of genotoxic effects was found. At 0.6 mM, 1 mM as well as 1.5 mM, an increase in the number of chromosomal aberrations was determined. Cytotoxic effects were not observed at any concentration. Proliferation, migration capability and differentiation potential were also not affected by the procedure. Labeling with VSOPs is a useful labeling method for hASCs that does not affect their proliferation, migration and differentiation potential. Despite the absence of cytotoxicity, however, indications of genotoxic effects have been demonstrated.

Ischemia-Like Stress Conditions Stimulate Trophic Activities of Adipose-Derived Stromal/Stem Cells.

Adipose-derived stromal/stem cells (ASCs) have been shown to exert regenerative functions, which are mainly attributed to the secretion of trophic factors. Upon transplantation, ASCs are facing an ischemic environment characterized by oxygen and nutrient deprivation. However, current knowledge on the secretion capacity of ASCs under such conditions is limited. Thus, the present study focused on the secretory function of ASCs under glucose and oxygen deprivation as major components of ischemia. After exposure to glucose/oxygen deprivation, ASCs maintained distinct viability, but the metabolic activity was greatly reduced by glucose limitation. ASCs were able to secrete a broad panel of factors under glucose/oxygen deprivation as revealed by a cytokine antibody array. Quantification of selected factors by ELISA demonstrated that glucose deprivation in combination with hypoxia led to markedly higher secretion levels of the angiogenic and anti-apoptotic factors IL-6, VEGF, and stanniocalcin-1 as compared to the hypoxic condition alone. A conditioned medium of glucose/oxygen-deprived ASCs promoted the viability and tube formation of endothelial cells, and the proliferation and migration of fibroblasts. These findings indicate that ASCs are stimulated by ischemia-like stress conditions to secrete trophic factors and would be able to exert their beneficial function in an ischemic environment.

Toxicity and Functional Impairment in Human Adipose Tissue-Derived Stromal Cells (hASCs) Following Long-Term Exposure to Very Small Iron Oxide Particles (VSOPs).

Magnetic nanoparticles (NPs), such as very small iron oxide NPs (VSOPs) can be used for targeted drug delivery, cancer treatment or tissue engineering. Another important field of application is the labelling of mesenchymal stem cells to allow in vivo tracking and visualization of transplanted cells using magnetic resonance imaging (MRI). For these NPs, however, various toxic effects, as well as functional impairment of the exposed cells, are described. The present study evaluates the influence of VSOPs on the multilineage differentiation ability and cytokine secretion of human adipose tissue derived stromal cells (hASCs) after long-term exposure. Human ASCs were labelled with VSOPs, and the efficacy of the labelling was documented over 4 weeks in vitro cultivation of the labelled cells. Unlabelled hASCs served as negative controls. Four weeks after labelling, adipogenic and osteogenic differentiation was histologically evaluated and quantified by polymerase chain reaction (PCR). Changes in gene expression of IL-6, IL-8, VEGF and caspase 3 were determined over 4 weeks. Four weeks after the labelling procedure, labelled and unlabelled hASCs did not differ in the gene expression of IL-6, IL-8, VEGF and caspase 3. Furthermore, the labelling procedure had no influence on the multidifferentiation ability of hASC. The percentage of labelled cells decreased during in vitro expansion over 4 weeks. Labelling with VSOPs and long-term intracellular disposition probably have no influence on the physiological functions of hASCs. This could be important for the future in vivo use of iron oxide NPs.

Human Adipose-Derived Mesenchymal Stromal/Stem Cell Spheroids Possess High Adipogenic Capacity and Acquire an Adipose Tissue-like Extracellular Matrix Pattern.

Adipose-derived mesenchymal stromal/stem cells (ASCs) represent a commonly used cell source for adipose tissue engineering. In this context, ASCs have routinely been cultured in conventional 2D culture and applied as single cell suspension for seeding onto scaffold materials or direct injection. However, this approach is associated with the loss of their intrinsic 3D microenvironment and leads to impaired regenerative capacity of the cells. Thus, the application of ASCs as self-assembled 3D spheroids with cells residing in their own matrix is an attractive alternative. However, characterization of the structural features and differentiation capacity of the spheroids is necessary to effectively apply them as building blocks in adipose tissue engineering. In this study, we focus on extracellular matrix (ECM) development in ASC spheroids, as well as adipogenic differentiation in comparison to conventional 2D culture using different induction protocols. Reproducible assembly of ASCs into spheroids was achieved within 24 h using the liquid overlay technique. Undifferentiated spheroids displayed a stromal ECM pattern, with fibronectin, collagen V, and VI as the main components. In the course of adipogenesis, a dynamic shift in the ECM composition toward an adipogenic phenotype was observed, associated with enhanced expression of laminin, collagen I, IV, V, and VI, similar to native fat. Furthermore, adipogenic differentiation was enhanced in spheroids as compared with 2D cultured cells, with the spheroids needing a distinctly shorter adipogenic stimulus to sustain adipogenesis, which was demonstrated based on analysis of triglyceride content and adipogenic marker gene expression. In summary, culturing ASCs as spheroids can enhance their adipogenic capacity and generate adipose-like microtissues, which may be a promising cell delivery strategy for adipose tissue engineering approaches. Impact statement Adipose-derived mesenchymal stromal/stem cells (ASCs) as a widely used cell source for adipose tissue engineering have been shown to be limited in their regenerative capacity when applied as single cells. As an alternative approach, the delivery as spheroids, consisting of cells in a 3D context, may be favorable. However, insights into extracellular matrix (ECM) development and efficient adipogenic differentiation are required for their effective application. In this study, we show that differentiated ASC spheroids develop an ECM, resembling native adipose tissue. Furthermore, the ASC spheroids exhibited a superior differentiation capacity as compared with conventional 2D culture, and required only a short adipogenic induction stimulus. Our results identify ASC-derived spheroids as an attractive cell delivery method for adipose tissue engineering approaches.

Long-Term Impact of Zinc Oxide Nanoparticles on Differentiation and Cytokine Secretion of Human Adipose-Derived Stromal Cells.

Zinc oxide nanoparticles (ZnO-NPs) are widely utilized, for example in manufacturing paints and in the cosmetic industry. In addition, there is raising interest in the application of NPs in stem cell research. However, cytotoxic, genotoxic and pro-inflammatory effects were shown for NPs. The aim of this study was to evaluate the impact of ZnO-NPs on cytokine secretion and differentiation properties of human adipose tissue-derived stromal cells (ASCs). Human ASCs were exposed to the subtoxic concentration of 0.2 µg/mL ZnO-NPs for 24 h. After four weeks of cultivation, adipogenic and osteogenic differentiation procedures were performed. The multi-differentiation potential was confirmed histologically and using polymerase chain reaction (PCR). In addition, the gene expression of IL-6, IL-8, vascular endothelial growth factor (VEGF) and caspase 3 was analyzed. Over the course of four weeks after ZnO-NPs exposure, no significant differences were detected in the gene expression of IL-6, IL-8, VEGF and caspase 3 compared to non-exposed cells. The differentiation was also not affected by the ZnO-NPs. These findings underline the fact, that functionality of ASCs is likely to be unaffected by ZnO-NPs, despite a long-term disposition of NPs in the cells, supposing that the starting concentration was safely in the non-toxic range. This might provide important information for single-use nanomedical applications of ZnO-NPs.

A polydopamine peptide coating enables adipose-derived stem cell growth on the silicone surface of cochlear implant electrode arrays.

The simultaneous application of neurotrophic factors with cochlear implantation is proposed to enhance the bioelectrical interface between electrodes and auditory neurons, and thus improve speech intelligibility in patients with cochlear implants (CIs). In cell-based approaches, the goal is to colonize CIs with cells producing neurotrophic factors. This study aims to evaluate whether a polydopamine (PD) functionalization of the hydrophobic silicone surface of the electrode carrier enables colonization of adipose-derived stem cells known to deliver neurotrophic factors. Surface characteristics of PD-coated silicone samples and electrode carriers were determined, and the proliferation and viability of adipose-derived stem cells (ASCs) on these surfaces were subsequently analyzed. A homogenous PD coating and cell growth with regular morphology was observed on coated silicone samples and electrode arrays. Hydrophilicity and cell viability was significantly enhanced by PD surface modification. Insertion forces of coated electrode arrays did not increase compared with untreated CIs. Hence, PD coating of the silicone surface of CIs might allow for sufficient colonization with ASCs as a continuous source of neurotrophic factors. © 2017 Wiley Periodicals, Inc. J Biomater Res Part A: 106B: 1431-1438, 2018.

Toxicological characterization of ZnO nanoparticles in malignant and non-malignant cells.

The increasing usage of zinc oxide nanoparticles (ZnO-NPs) in industrial applications as well as in consumer products raises concern regarding their potential adverse effects to a greater extend. Numerous studies have demonstrated toxic properties of NPs, however there is still a lack of knowledge concerning the underlying mechanisms. This study was designed to systematically investigate cytotoxicity, apoptosis, cell cycle alterations, and genotoxicity induced by ZnO-NP. Moreover, it was an aim of the investigations to specify the diverse effects of nanoparticle exposure in malignant in comparison with non-malignant cells. Therefore, human head and neck squamous cell carcinoma-derived FaDu cells were incubated with 4-20 µg/ml of ZnO-NPs for 1-48 hr and tested for cell viability, cell cycle alterations, apoptosis and caspase-3 gene expression as a sensitive marker of molecular apoptotic processes with regard to time- and dose-dependent effects. Human mesenchymal bone marrow stem cells were used as non-malignant representatives to examine oxidative stress-related genotoxicity. Results showed a significant reduction in cell viability as well as dose- and time-dependent increase of apoptotic cells following nanoparticle treatment. Likewise, caspase-3 gene expression enhanced already before first apoptotic cells were detectable. It could be observed that doses that were cytotoxic in tumor cells did not reduce viability in stem cells. However, the same concentrations already induced significant DNA damage. The findings of the study suggest to keep a more critical eye on the use of nanoparticles as anti-cancer agents. Yet, additional in vivo studies are needed to assess safety concerns for consumers and patients. Environ. Mol. Mutagen. 59:247-259, 2018. © 2017 Wiley Periodicals, Inc.

Time-Dependent Toxic and Genotoxic Effects of Zinc Oxide Nanoparticles after Long-Term and Repetitive Exposure to Human Mesenchymal Stem Cells.

Zinc oxide nanoparticles (ZnO-NP) are widely spread in consumer products. Data about the toxicological characteristics of ZnO-NP is still under controversial discussion. The human skin is the most important organ concerning ZnO-NP exposure. Intact skin was demonstrated to be a sufficient barrier against NPs; however, defect skin may allow NP contact to proliferating cells. Within these cells, stem cells are the most important toxicological target for NPs. The aim of this study was to evaluate the genotoxic and cytotoxic effects of ZnO-NP at low-dose concentrations after long-term and repetitive exposure to human mesenchymal stem cells (hMSC). Cytotoxic effects of ZnO-NP were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Furthermore, genotoxicity was evaluated by the comet assay. For long-term observation over 6 weeks, transmission electron microscopy (TEM) was applied. The results of the study indicated cytotoxic effects of ZnO-NP beginning at high concentrations of 50 µg/mL and genotoxic effects in hMSC exposed to 1 and 10 µg/mL ZnO-NP. Repetitive exposure enhanced cyto- but not genotoxicity. Intracellular NP accumulation was observed up to 6 weeks. The results suggest cytotoxic and genotoxic potential of ZnO-NP. Even low doses of ZnO-NP may induce toxic effects as a result of repetitive exposure and long-term cellular accumulation. This data should be considered before using ZnO-NP on damaged skin.

Adipose-derived stromal cells enhance auditory neuron survival in an animal model of sensory hearing loss.

BACKGROUND: A cochlear implant (CI) is an electronic prosthesis that can partially restore speech perception capabilities. Optimum information transfer from the cochlea to the central auditory system requires a proper functioning auditory nerve (AN) that is electrically stimulated by the device. In deafness, the lack of neurotrophic support, normally provided by the sensory cells of the inner ear, however, leads to gradual degeneration of auditory neurons with undesirable consequences for CI performance. METHODS: We evaluated the potential of adipose-derived stromal cells (ASCs) that are known to produce neurotrophic factors to prevent neural degeneration in sensory hearing loss. For this, co-cultures of ASCs with auditory neurons have been studied, and autologous ASC transplantation has been performed in a guinea pig model of gentamicin-induced sensory hearing loss. RESULTS: In vitro ASCs were neuroprotective and considerably increased the neuritogenesis of auditory neurons. In vivo transplantation of ASCs into the scala tympani resulted in an enhanced survival of auditory neurons. Specifically, peripheral AN processes that are assumed to be the optimal activation site for CI stimulation and that are particularly vulnerable to hair cell loss showed a significantly higher survival rate in ASC-treated ears. DISCUSSION/CONCLUSION: ASC transplantation into the inner ear may restore neurotrophic support in sensory hearing loss and may help to improve CI performance by enhanced AN survival.

Genotoxic effects of zinc oxide nanoparticles in nasal mucosa cells are antagonized by titanium dioxide nanoparticles.

Titanium dioxide nanoparticles (TiO2-NPs) and zinc oxide nanoparticles (ZnO-NPs) are often used in sunscreens and other consumer products due to their photoprotective properties. However, concern exists regarding them possibly causing cyto- and genotoxic effects. The aim of this study was to assess cyto- and genotoxicity of these nanomaterials after single or combined exposure. For this purpose, a battery of cell culture test systems for human nasal mucosa (monolayer, air-liquid interface and mini organ culture) were exposed to 0.1-20µg/ml of TiO2- and ZnO-NPs alone and in combination. Cytotoxicity was measured by the MTT assay, and DNA damage and repair capacity were investigated using the comet assay. TiO2-NPs did not exhibit any cyto- or genotoxic potential within the tested concentrations. However, results of the study indicated cyto- and genotoxicity resulting from ZnO-NPs. The genotoxicity could be antagonized by TiO2-NPs. Furthermore, the DNA repair capacity after ZnO-NP-induced DNA damage was enhanced by TiO2-NPs. The adsorption of dissolved zinc ions onto TiO2-NPs is discussed as the major antagonistic mechanism. The combination of both metal oxide nanoparticles interferes with the genotoxicity of ZnO-NPs and should be discussed as a reasonable and safe alternative to the sole use of ZnO-NPs in consumer products.