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To quantify and visualize both bone formation and resorption within osteochondral explants cultured ex vivo is challenging with the current analysis techniques. An approach that enables monitoring of bone remodeling dynamics is longitudinal microcomputed tomography (µCT), a non‐destructive technique that relies on repeated µCT scanning and subsequent registration of consecutive scans. In this study, a two‐compartment culture system suitable for osteochondral explants that allowed for µCT scanning during ex vivo culture was established. Explants were scanned repeatedly in a fixed orientation, which allowed assessment of bone remodeling due to adequate image registration. Using this method, bone formation was found to be restricted to the outer surfaces when cultured statically. To demonstrate that the culture system could capture differences in bone remodeling, explants were cultured statically and under dynamic compression as loading promotes osteogenesis. No quantitative differences between static and dynamic culture were revealed. Still, only in dynamic conditions, bone formation was visualized on trabecular surfaces located within the inner cores, suggesting enhanced bone formation towards the center of the explants upon mechanical loading. Taken together, the ex vivo culture system in combination with longitudinal µCT scanning and subsequent registration of images demonstrated potential for evaluating bone remodeling within explants. [ABSTRACT FROM AUTHOR]

To reduce animal experimentation and to overcome translational issues in cartilage tissue engineering, there is a need to develop an ex vivo human tissue‐based approach. This study aims to demonstrate that a human osteochondral explant at different stages of osteoarthritis (OA) can be kept in long‐term culture while preserving its viability and composition. Osteochondral explants with either a smooth or fibrillated cartilage surface, representing different OA stages, were harvested from fresh human tibial plateaus. Explants were cultured for 2 or 4 weeks in a double‐chamber culture platform. The biochemical content of the cartilage of cultured explants did not significantly change over a period of 4 weeks and these findings were supported by histology. Chondrocytes mostly preserved their metabolic activity during culture and active bone and marrow were found in the periphery of the explants, while metabolic activity was decreased in the bone core in cultured explants compared to fresh explants. In fibrillated explants, chondrocyte viability decreased in the periphery of the sample in cultured groups compared to fresh explants (fresh, 94 ± 6%; cultured, 64% ± 17%, 2 weeks, and 69% ± 17%, 4 weeks; P <.05). Although biochemical and histological results did not show changes within the cartilage tissue, the viability of the explants should be carefully controlled for each specific use. This system provides an alternative to explore drug treatment and implant performance under more controlled experimental conditions than possible in vivo, in combination with clinically relevant human osteochondral tissue. [ABSTRACT FROM AUTHOR]

To replicate functional liver tissue in vitro for drug testing or transplantation, 3D tissue engineering requires representative cell models as well as scaffolds that not only promote tissue production but also are applicable in a clinical setting. Recently, adult liver-derived liver organoids are found to be of much interest due to their genetic stability, expansion potential, and ability to differentiate toward a hepatocyte-like fate. The current standard for culturing these organoids is a basement membrane hydrogel like Matrigel (MG), which is derived from murine tumor material and apart from its variability and high costs, possesses an undefined composition and is therefore not clinically applicable. Here, a cellulose nanofibril (CNF) hydrogel is investigated with regard to its potential to serve as an alternative clinical grade scaffold to differentiate liver organoids. The results show that its mechanical properties are suitable for differentiation with overall, either equal or improved, functionality of the hepatocyte-like cells compared to MG. Therefore, and because of its defined and tunable chemical definition, the CNF hydrogel presents a viable alternative to MG for liver tissue engineering with the option for clinical use., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An ex vivo aneurysm model that closely resembles the in vivo situation can provide an important tool for testing therapies. The model should mimic a variety of conditions, such as in vivo hemodynamics and native arterial structure and characteristics, avoiding animal experimentation.  Therefore, the aim of this study is to develop an ex vivo aneurysm model by vessel wall stiffening to be used to assess treatment strategies. Porcine carotid arteries from slaughterhouse animals were used to evaluate the acute effect of different concentrations of Rose Bengal on distensibility. This sono-sensitive compound was activated by several ultrasound frequencies, resulting in stiffening of the treated arteries of which the most effective combination was selected. In a pulsatile ex vivo vascular bioreactor treated and control porcine carotid arteries were subjected to physiological conditions for 10 days. During culture, hemodynamics showed increased mean pressure and decreased pulsatility in treated arteries compared to controls. Change in vessel morphology and significant increase of distal diameter was observed in the treated arteries but not in the controls. Histology of treated arteries revealed dissection-like lesions distally and aneurysm-like structure proximally. Finally, a stent graft was deployed in one treated artery and cultured demonstrating the feasibility of testing endovascular devices in the model. In conclusion, we developed an ex vivo model reproducing the onset of aneurysm formation. This could represent a promising tool for early stage device testing thereby reducing the need for animal studies.