TY - GEN A1 - Herzog, Natalie A1 - Katzenberger, Nadine A1 - Martin, Frank A1 - Schmidtke, Kai-Uwe A1 - Küpper, Jan-Heiner T1 - Generation of cytochrome P450 3A4-overexpressing HepG2 cell clones for standardization of hepatocellular testosterone 6β-hydroxylation activity T2 - Journal of Cellular Biotechnology Y1 - 2015 U6 - https://doi.org/10.3233/JCB-15002 SN - 2352-3697 SN - 2352-3689 VL - 1 IS - 1 SP - 15 EP - 26 ER - TY - GEN A1 - Martin, Frank A1 - Lehmann, Mario A1 - Sack, Ulrich A1 - Anderer, Ursula T1 - In vitro development of personalized cartilage microtissues uncovers an individualized differentiation capacity of human chondrocytes T2 - Experimental Biology and Medicine KW - Articular cartilage KW - 3D culture KW - microtissue KW - scaffold-free KW - personalized differentiation KW - responder/non-responder KW - personalized diagnostic platform Y1 - 2017 U6 - https://doi.org/10.1177/1535370217728498 SN - 1535-3702 VL - 242 IS - 18 SP - 1746 EP - 1756 ER - TY - CHAP A1 - Martin, Frank A1 - Lehmann, Mario A1 - Anderer, Ursula ED - Daskalaki, Adriani T1 - Generation of scaffold free 3-D cartilage-like microtissues from human chondrocytes T2 - Medical Advancements in Aging and Regenerative Technologies: Clinical Tools and Applications KW - Cartilage Repair Strategies KW - Engineering cartilage-like microtissues without scaffolds KW - Redifferentiation of chondrocytes in a three-dimensional environment KW - S100 protein as marker for chondrogenic development Y1 - 2013 SN - 978-1-4666-2506-8 SP - 169 EP - 194 PB - IGI Global CY - Hershey, PA, USA ER - TY - GEN A1 - Lehmann, Mario A1 - Martin, Frank A1 - Mannigel, Kerstin A1 - Kaltschmidt, Kristin A1 - Sack, Ulrich A1 - Anderer, Ursula T1 - Three-dimensional scaffold-free fusion culture: the way to enhanced chondrogenesis of in vitro propagated human articular chondrocytes T2 - European Journal of Histochemistry KW - in vitro cartilage KW - 3-D cell culture KW - fusion culture technique KW - tissue engineering KW - cell differentiation KW - extracellular matrix KW - immunohistochemistry Y1 - 2013 U6 - https://doi.org/10.4081/ejh.2013.e31 SN - 2038-8306 SN - 1121-760X VL - 57 IS - 4 SP - 205 EP - 215 ER - TY - GEN A1 - Martin, Frank A1 - Lehmann, Mario A1 - Schläger, Peter A1 - Sack, Ulrich A1 - Anderer, Ursula T1 - Differentiation capacity of chondrocytes in microtissues depends on TGF-ß subtyp T2 - Journal of biochips & tissue chips : JBTC KW - microtissues KW - differentiation of chondrocytes KW - TGF-β subtypes KW - BMP-7 Y1 - 2012 U6 - https://doi.org/10.4172/2153-0777.S2-002 SN - 2153-0777 N1 - Special Issue Article VL - S2 IS - 002 ER - TY - CHAP A1 - Lehmann, Mario A1 - Voß, Fränzi A1 - Martin, Frank A1 - Schläger, Peter A1 - Anderer, Ursula T1 - Chondrogenic microtissues in the lab & for the clinic T2 - 3D cell culture 2016, book of abstracts, DECHEMA Biotechnologie KW - in vitro cartilage defect KW - in vitro therapy model KW - chondrocyte-derived cell line Y1 - 2016 SN - 978-3-89746-182-6 SP - 52 EP - 53 PB - DECHEMA e.V. CY - Frankfurt am Main ER - TY - CHAP A1 - Lehmann, Mario A1 - Martin, Frank A1 - Scholka, Jenny A1 - Petto, Carola A1 - Wittenburg, Gretel A1 - Sack, Ulrich A1 - Anderer, Ursula T1 - Human chondrocytes and dental pulp stem cells enhance their chondrogenic differentiation potential via a two-step fusion culture technique T2 - Tissue Engineering, Part A, Vol. 21, Suppl. 1 KW - in vitro chondrogenesis KW - dental pulp stem cells KW - scaffold-free 3D culture KW - two-step fusion technique Y1 - 2015 U6 - https://doi.org/10.1089/ten.tea.2015.5000.abstracts SP - S-268 EP - S-269 ER - TY - CHAP A1 - Lehmann, Mario A1 - Voß, Fränzi A1 - Martin, Frank A1 - Richter, Heiko A1 - Anderer, Ursula T1 - Chondrogenic microtissues with a lower differentiation degree used as in vitro transplants show improved integration in the tissue repair process in an in vitro therapy culture system T2 - Regenerative Medicine KW - chondrogenic microtissues KW - in vitro therapy culture system KW - transplant integration KW - therapy mimicry Y1 - 2015 SN - 1746-0751 VL - 10 IS - 7S SP - S. 53 ER - TY - GEN A1 - Martin, Frank A1 - Neubert, Annemarie A1 - Lutter, Anne-Helen A1 - Scholka, Jenny A1 - Hentschel, Erik A1 - Richter, Heiko A1 - Anderer, Ursula T1 - MTS, WST-8, and ATP viability assays in 2D and 3D cultures: Comparison of methodologically different assays in primary human chondrocytes T2 - Clinical Hemorheology and Microcirculation N2 - BACKGROUND: Tissue engineering enables the production of three-dimensional microtissues which mimic naturally occurring conditions in special tissues. These 3D culture systems are particularly suitable for application in regenerative medicine or experimental pharmacology and toxicology. Therefore, it is important to analyse the cells in their 3D microenvironment with regard to viability and differentiation. Tetrazolium assays (WST-8 and MTS) are still the methods of choice for estimating the number of living, metabolically active cells, with WST-8 being cell-impermeable compared to MTS. In contrast to these methods, the ATP assay is an endpoint method based on the luciferase-induced reaction of ATP with luciferin after cell lysis. OBJECTIVE:We compared three methodologically different proliferation/toxicity assays (MTS, WST-8, ATP) in monolayer (2D) and 3D culture systems to improve the technically challenging determination of the number of viable cells. METHODS: Chondrocytes were isolated from human articular cartilage. Three different test systems (MTS, WST-8, ATP) were applied to monolayer cells (2D, varying cell numbers) and spheroids (3D, different sizes) in 96-well plates. The intracellular ATP concentration was determined by luciferase-induced reaction of ATP with luciferin using a luminometer. Formazan formation was measured spectrophotometrically after different incubation periods. Evaluation was performed by phase contrast microscopy (toxicity), correlation of cell count and ATP concentration or absorption signal (Gompertz function) and propidium iodide (PI) staining to proof the cell lysis of all cells in spheroids. RESULTS: In 2D culture, all three assays showed a good correlation between the number of seeded cells and the ATP concentration or absorption data, whereas the MTS-assay showed the lowest specificity. In 3D culture, the spheroid sizes were directly related to the number of cells seeded. The absorption data of the WST-8 and MTS assay correlated only for certain spheroid size ranges, whereas the MTS-assay showed again the lowest specificity. Only the measured intracellular ATP content showed a linear correlation with all spheroid sizes ranging from 100–1000 µm. The WST-8 assay revealed the second-best sensitivity which allows the measurement of spheroids larger than 240 µm. Phase contrast observation of monolayer cells showed toxic effects of MTS after 6 h incubation and no signs of toxicity of WST-8. Staining with propidium iodide showed complete lysis of all cells in a spheroid in the ATP assay. CONCLUSION: Among tetrazolium-based assays, WST-8 is preferable to MTS because of its non-toxicity and better sensitivity. When determining the number of viable cells in the 2D system, caution is advised when using the ATP assay because of its two-phase slope of the correlation graph concerning cell number and intracellular ATP. In 3D systems of human chondrocytes, the ATP-assay is superior to the other two test systems, as the correlation graph between cell number and intracellular ATP is biphasic. Since differentiation processes or other metabolic events can influence the results of proliferation and toxicity assays (determination of viable cells), this should be taken into account when using these test systems. KW - ATP assay KW - MTS KW - WST-8 KW - Human chondrocytes KW - Spheroid KW - 3D culture KW - 2D culture Y1 - 2024 UR - https://journals.sagepub.com/doi/abs/10.3233/CH-248101 U6 - https://doi.org/10.3233/CH-248101 SN - ISSN 1386-0291 VL - 88 SP - 3 EP - 19 PB - IOS Press ER -