Alexandra Lorenz

The multi-organ chip--a microfluidic platform for long-term multi-tissue coculture.

The ever growing amount of new substances released onto the market and the limited predictability of current in vitro test systems has led to a high need for new solutions for substance testing. Many drugs that have been removed from the market due to drug-induced liver injury released their toxic potential only after several doses of chronic testing in humans. However, a controlled microenvironment is pivotal for long-term multiple dosing experiments, as even minor alterations in extracellular conditions may greatly influence the cell physiology. We focused within our research program on the generation of a microengineered bioreactor, which can be dynamically perfused by an on-chip pump and combines at least two culture spaces for multi-organ applications. This circulatory system mimics the in vivo conditions of primary cell cultures better and assures a steadier, more quantifiable extracellular relay of signals to the cells. For demonstration purposes, human liver equivalents, generated by aggregating differentiated HepaRG cells with human hepatic stellate cells in hanging drop plates, were cocultured with human skin punch biopsies for up to 28 days inside the microbioreactor. The use of cell culture inserts enables the skin to be cultured at an air-liquid interface, allowing topical substance exposure. The microbioreactor system is capable of supporting these cocultures at near physiologic fluid flow and volume-to-liquid ratios, ensuring stable and organotypic culture conditions. The possibility of long-term cultures enables the repeated exposure to substances. Furthermore, a vascularization of the microfluidic channel circuit using human dermal microvascular endothelial cells yields a physiologically more relevant vascular model.

Map design aspects, route complexity, or social background? Factors influencing user satisfaction with indoor navigation maps

Indoor map design is still an uncharted territory. More often than not, existing architectural floor plans are used as visualization means that do not fulfill cartographic requirements. In collaboration between geoinformation science and sociology, we develop and investigate cartographic methods for effective route guidance in indoor environments. The baseline for our evaluation is the annual user studies with up to 1100 participants per year. Since 2009, they were conducted during the “Long Night of Sciences,” a big event where large scientific institutions present themselves to the general public. For the 2011 study, we developed eight maps, which varied in design with respect to two map properties: map perspective and landmark representation. We evaluated the map design features as well as route complexity and sociodemographic characteristics. In order to rate their effect on an user satisfaction as an indicator of navigational success, we carried out a series of analyses of variance. Our results underline the importance of a map design: Map perspective and landmarks alone explain about 30% of the variance in the user satisfaction with maps, which is by far the biggest share in a navigational success.

App-Free Zone: Paper Maps as Alternative to Electronic Indoor Navigation Aids and Their Empirical Evaluation with Large User Bases

Nowadays, mobile devices are widely used as navigation aids, e.g., for car navigation. Their greatest advantage is the ability of automatic position tracking. In indoor environments, this feature is often not available, since indoor localization techniques are not ready for the mass-market yet. What remains is a small display with limited space for route visualizations. In contrast, the variable size of paper allows for the representation of additional context information as a means for spatial understanding and orientation in space, rendering it a valuable alternative presentation medium for indoor navigation aids. Independent of the medium used, provided visualizations must meet specific cartographic requirements like clarity, comprehensibility, and expedience. Within a co-operation between geoinformation science and sociology, we develop and investigate cartographic methods for effective route guidance in indoor environments. Our evaluation base comes from user studies conducted with more than 3,000 visitors, of both genders and aged between 4 and 78 years. These user studies were collected during the “Long Nights of Science” in Berlin in 2009, 2010, 2011, and 2012. We used paper as the presentation medium for our experiments, not only for practical reasons but also because we want to confront our participants with a solution which does not align to the current trend. Within this article we put special focus on media characteristics and users’ media preferences. Therefore, we asked our participants about their opinion on the provided paper maps in contrast to mobile solutions. Based on their answers, we could derive media characteristics relevant from a user’s perspective, as well as the affinities of different user groups. One astonishing outcome was that 11–15 year-old teenagers indicate a much higher tendency towards paper maps than towards smartphone apps.

Dynamic culture of human liver equivalents inside a micro-bioreactor for long-term substance testing

Published by BioMed Central: Materne, Eva-Maria et al.: Dynamic culture of human liver equivalents inside a micro-bioreactor for longterm substance testing. - In: BMC Proceedings. - ISSN 1753-6561 (online). - 7 (2012), suppl. 6, art. P72. - doi:10.1186/1753-6561-7-S6-P72.

Assessment of troglitazone induced liver toxicity in a dynamically perfused two-organ Micro-Bioreactor system

Background The ever-growing amount of new substances released to the market and the limited predictability of current in vitro test systems has led to an ample need for new substance testing solutions. Many drugs like troglitazone, that had to be removed from the market due to drug induced liver injury, show their toxic potential only after chronic long term exposure. But for long-term multiple dosing experiments, a controlled microenvironment is pivotal, as even minor alterations in extracellular conditions may greatly influence the cell physiology. Within our research program, we focused on the generation of a micro-engineered bioreactor, which can be dynamically perfused by an on-chip pump and combines at least two culture spaces for multi-organ applications. This circulatory systems better mimics the in vivo conditions of primary cell cultures and assures steadier, more quantifiable extracellular signaling to the cells.

Towards an autologous iPSC-derived patient-on-a-chip

Microphysiological systems are fundamental for progressing towards a global paradigm shift in drug development through the generation of patient-on-a-chip models. An increasing number of single- and multi-organ systems have been adopted by the pharmaceutical and cosmetic industries for predictive substance testing. These models run on heterogeneous tissues and cell types from different donors. However, a patient is an individual. Therefore, patient-on-a-chip systems need to be built from tissues from one autologous source. Individual on-chip organ differentiation from a single induced pluripotent stem cell source could provide a solution to this challenge. We designed a four-organ chip based on human physiology. It enables the interconnection of miniaturized human intestine, liver, brain and kidney equivalents. All four organ models were predifferentiated from induced pluripotent stem cells from the same healthy donor and integrated into the microphysiological system. The cross talk led to further differentiation over a 14-day cultivation period under pulsatile blood flow conditions in one common medium deprived of growth factors. This model platform will pave the way for disease induction and subsequent drug testing.

Simultaneous evaluation of anti-EGFR-induced tumour and adverse skin effects in a microfluidic human 3D co-culture model

Antibody therapies targeting the epithelial growth factor receptor (EGFR) are being increasingly applied in cancer therapy. However, increased tumour containment correlates proportionally with the severity of well-known adverse events in skin. The prediction of the latter is not currently possible in conventional in vitro systems and limited in existing laboratory animal models. Here we established a repeated dose “safficacy” test assay for the simultaneous generation of safety and efficacy data. Therefore, a commercially available multi-organ chip platform connecting two organ culture compartments was adapted for the microfluidic co-culture of human H292 lung cancer microtissues and human full-thickness skin equivalents. Repeated dose treatment of the anti-EGFR-antibody cetuximab showed an increased pro-apoptotic related gene expression in the tumour microtissues. Simultaneously, proliferative keratinocytes in the basal layer of the skin microtissues were eliminated, demonstrating crucial inhibitory effects on the physiological skin cell turnover. Furthermore, antibody exposure modulated the release of CXCL8 and CXCL10, reflecting the pattern changes seen in antibody-treated patients. The combination of a metastatic tumour environment with a miniaturized healthy organotypic human skin equivalent make this “safficacy” assay an ideal tool for evaluation of the therapeutic index of EGFR inhibitors and other promising oncology candidates.

Automated substance testing for lab-on-chip devices

First published by BioMed Central: Kloke, Lutz ; Schimek, Katharina ; Brincker, Sven ; Lorenz, Alexandra ; Janicke, Annika ; Drewell, Christopher ; Hoffmann, Silke ; Busek, Mathias ; Sonntag, Frank ; Danz, Norbert ; Polk, Christoph ; Schmieder, Florian ; Borchanikov, Alexey ; Artyushenko, Viacheslav ; Baudisch, Frank ; Burger, Mario ; Horland, Reyk ; Lauster, Roland ; Marx, Uwe : Automated substance testing for lab-on-chip devices : From 23rd European Society for Animal Cell Technology (ESACT) Meeting: Better Cells for Better Health Lille, France. 23-26 June 2013. - In: BMC Proceedings. - ISSN 1753-6561 (online). - 7 (2013), suppl. 6, P28. - doi:10.1186/1753-6561-7-S6-P28.

Aspects of vascularization in Multi-Organ-Chips

Background Enormous efforts have been made to develop circulation systems for physiological nutrient supply and waste removal of in vitro cultured tissues. These developments are aiming for in vitro generation of organ equivalents such as liver, lymph nodes and lung or even multi-organ systems for substance testing, research on organ regeneration or transplant manufacturing. Initially technical perfusion systems based on membranes, hollow fibers or networks of micro-channels were used for these purposes. However, none of the currently available systems ensures long-term homeostasis of the respective tissue over months. This is caused by a lack of in vivo-like vasculature which leads to continuous accumulation of protein sediments and cell debris in the systems. Here, we demonstrate a closed and self-contained circulation system emulating the natural blood perfusion environment of vertebrates at tissue level.