A human in vitro model that mimics the renal proximal tubule.

Human in vitro-manufactured tissue and organ models can serve as powerful enabling tools for the exploration of fundamental questions regarding cell, matrix, and developmental biology in addition to the study of drug delivery dynamics and kinetics. To date, the development of a human model of the renal proximal tubule (PT) has been hindered by the lack of an appropriate cell source and scaffolds that allow epithelial monolayer formation and maintenance. Using extracellular matrices or matrix proteins, an in vivo-mimicking environment can be created that allows epithelial cells to exhibit their typical phenotype and functionality. Here, we describe an in vitro-engineered PT model. We isolated highly proliferative cells from cadaveric human kidneys (human kidney-derived cells [hKDCs]), which express markers that are associated with renal progenitor cells. Seeded on small intestinal submucosa (SIS), hKDCs formed a confluent monolayer and displayed the typical phenotype of PT epithelial cells. PT markers, including N-cadherin, were detected throughout the hKDC culture on the SIS, whereas markers of later tubule segments were weak (E-cadherin) or not (aquaporin-2) expressed. Basement membrane and microvilli formation demonstrated a strong polarization. We conclude that the combination of hKDCs and SIS is a suitable cell-scaffold composite to mimic the human PT in vitro.

RETRACTED: Vascularised human tissue models: a new approach for the refinement of biomedical research.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Author(s). (a) The authors have duplicated at least one figure from a paper that had already appeared in: • Engineered Liver-Like Tissue on a Capillarized Matrix for Applied Research. TISSUE ENGINEERING; Volume 13, Number 11, 2007 Engineered Liver-Like Tissue on a Capillarized Matrix for Applied Research. KIRSTIN LINKE, JOHANNA SCHANZ, JAN HANSMANN, THORSTEN WALLES, HERWIG BRUNNER, & HEIKE MERTSCHING Apparently, no permission was obtained to re-publish the image, as the authors did not provide us with a copy of a release issued by Mary Ann Liebert Inc. with an authorization to re-publish the figure initially published in Linke et al. (2007) in J. Biotechnology. In this case, this infringes on the copyright of Mary Ann Liebert Inc. The authors stated on Feb. 11 2017 in an email to the Editor in Chief: "Between 2007 and 2010 we modified the culture conditions in out (Chief Editor comment: this means "our") tissue models. These changes did not influence the morphology and 3 D arrangement of the cells. However, they changed the long term function of out (Chief Editor comment: this means "our") tissue models." Therefore, they implied that the figures shown in the 2010 paper demonstrate that there were no changes in the "morphology and 3 D arrangement of the cells" when comparing the culture conditions. It would, in our opinion, be impossible to demonstrate the similarities in the two different culture conditions by using the same figures as in the 2007 article, as both instances only show the result of the original culture condition. (b) The authors have also (self)plagiarized significant text sections from: • Genes Nutr. 2009 September; 4(3): 165-172 Penza, Jeremic, Montani, Unkila, Caimi, Mazzoleni, Diego Di Lorenzo PMCID: PMC2745740 DOI: 10.1007/s12263-009-0214-7 Springer-Verlag 2009 • Van den Belt K, Berckmans P, Vangenechten C, Verheyen R, Witters H (2004) Comparative study on the in vitro/in vivo estrogenic potencies of 17beta-estradiol, estrone, 17alpha-ethynylestradiol and nonylphenol. Aquat Toxicol 66(2):183­195 • Generation and Transplantation of an Autologous Vascularized Bioartificial Human Tissue. (2009) Clinical and Translational Research Transplantation; 27 July 2009 - Volume 88 - Issue 2 - pp 203-210 Heike Mertsching, Johanna Schanz, Volker Steger, Markus Schandar, Martin Schenk, Jan Hansmann, Iris Dally, Godehard Friedel, & Thorsten Walles One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data and text should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process

Generation and transplantation of an autologous vascularized bioartificial human tissue.

BACKGROUND: The lack of transplant vascularization forecloses the generation and clinical implementation of bioartificial tissues. We developed techniques to generate a bioartificial human tissue with an innate vascularization. The tissue was implanted clinically as proof of concept to evaluate vascular network thrombogenicity and tissue viability after transplantation. METHODS: A porcine small bowl segment was decellularized in a two-step procedure, preserving its vascular structures. The extracellular matrix was characterized quantitatively for DNA residues and protein composition. The vascular remainings were reseeded with human endothelial cells in a dynamic tissue culture. The engineered tissue was characterized by (1) histology, (2) immune-histology, (3) life-dead assay, and (4) metabolic activity. To evaluate the tissue capabilities, it was implanted clinically and recovered after 1 week. RESULTS: Tissue preparation with sodium desoxycholate monohydrate solution resulted in an incomplete decellularization. Cell residues were removed by additional tissue incubation with DNAse. The human endothelial cells formed a viable endothelium inside the primarily porcine extracellular matrix, expressing CD31, Flk-1, and vascular endothelium-cadherin. The metabolic activity of the bioartificial tissue increased continuously over time in vitro. Clinical tissue transplantation confirmed vessel patency and tissue viability for 1 week. CONCLUSIONS: The feasibility to bioengineer a human tissue with an innate vascularization has been shown in vitro and the clinical setting. These results may open the door for the clinical application of various sophisticated bioartificial tissue substitutes and organ replacements.

Engineered liver-like tissue on a capillarized matrix for applied research.

Liver tissue that is functional and viable for several weeks in vitro represents an auspicious test system for basic and applied research. In this study, a coculture system for hepatocytes (HCs) and microvascular endothelial cells (mECs) was generated applying tissue-engineering techniques, establishing the basis for a new bioartificial liver in vitro model. Porcine mECs were seeded on a decellularized porcine jejunal segment with preserved vascular structures. Porcine HCs were seeded onto this vascularized scaffold, and the resulting coculture was maintained for 3 weeks in vitro. Tissue morphology and differentiation was monitored using histology and immunohistochemistry. Tissue metabolism was monitored using daily assessment of urea and lactate production. HC monolayer cultures served as controls. The 2-stage seeding procedure resulted in a 3-dimensional coculture system harboring HC cell clusters in multiple cell layers lining the generated mEC-seeded capillary structures. It was viable for 3 weeks, and HCs maintained their morphology and differentiation. Biochemical testing revealed stable metabolic activity of the tissue culture. In contrast, HCs cultured in monolayer showed morphological dedifferentiation and an unfavorable metabolic state. Our mEC-HC coculture represents a new approach toward a functional bioartificial liver-like tissue applicable as a test system for basic and applied research.

Engineering of a vascularized scaffold for artificial tissue and organ generation.

Tissue engineering is an emerging field in regenerative medicine to overcome the problem of end-stage organ failure. However, complex tissues and organs need a vascular supply to guaranty graft survival and render bioartificial organ function. Here we developed methods to decellularize porcine small bowl segments and repopulate the remaining venous and arterial tubular structures within these matrices with allogeneic porcine endothelial progenitor cells. Cellular adherence and vitality was characterized by quantitative 2-[18F]-fluoro-2'-desoxy-glucose (FDG) positron emission tomography (PET) and subsequent immunohistological work up. The generated matrices showed insulin-dependent FDG uptake predominantly in the region of the former vascular structures. Stain for vitality and the specific endothelial markers CD31, VE-Cadherin and Flk-1 matched this functional finding. Providing evidence for vitality up to 3 weeks post reconstitution and typical endothelial differentiation, these results indicate that our generated matrix allows the generation of complex bioartificial tissues and organs for experimental and future clinical application.

Experimental generation of a tissue-engineered functional and vascularized trachea.

OBJECTIVE: We sought to grow in vitro functional smooth muscle cells, chondrocytes, and respiratory epithelium on a biologic, directly vascularized matrix as a scaffold for tracheal tissue engineering. METHODS: Ten- to 15-cm-long free jejunal segments with their own vascular pedicle were harvested and acellularized from donor pigs (n = 10) and used as a vascular matrix. Autologous costal chondrocytes, smooth muscle cells, and respiratory epithelium and endothelial progenitor cells were first cultured in vitro and then disseminated on the previously acellularized vascular matrix. Histologic, immunohistologic, molecular imaging, and Western blotting studies were then performed to assess cell viability. RESULTS: The endothelial progenitor cells re-endothelialized the matrix to such an extent that endothelial cell viability was uniformly documented through 2-(18F)-fluoro-2'-deoxyglucose positron emission tomography. This vascularized scaffold was seeded with functional (according to Western blot analysis) smooth muscle cells and successfully reseeded with viable ciliated respiratory epithelium. Chondrocyte growth and production of extracellular cartilaginous matrix was observed as soon as 2 weeks after their culture. CONCLUSIONS: The fundamental elements for a bioartificial trachea were successfully engineered in vitro in a direct vascularized 10- to 15-cm-long bioartificial matrix. Future experimental work will be directed to give them a 3-dimensional aspect and a biomechanical profile of a functioning trachea.