Many drugs have progressed through preclinical and clinical trials and have been available - for years in some cases - before being recalled by the FDA for unanticipated toxicity in humans. One ...reason for such poor translation from drug candidate to successful use is a lack of model systems that accurately recapitulate normal tissue function of human organs and their response to drug compounds. Moreover, tissues in the body do not exist in isolation, but reside in a highly integrated and dynamically interactive environment, in which actions in one tissue can affect other downstream tissues. Few engineered model systems, including the growing variety of organoid and organ-on-a-chip platforms, have so far reflected the interactive nature of the human body. To address this challenge, we have developed an assortment of bioengineered tissue organoids and tissue constructs that are integrated in a closed circulatory perfusion system, facilitating inter-organ responses. We describe a three-tissue organ-on-a-chip system, comprised of liver, heart, and lung, and highlight examples of inter-organ responses to drug administration. We observe drug responses that depend on inter-tissue interaction, illustrating the value of multiple tissue integration for in vitro study of both the efficacy of and side effects associated with candidate drugs.
Abstract Engineering cardiac tissues and organ models remains a great challenge due to the hierarchical structure of the native myocardium. The need of integrating blood vessels brings additional ...complexity, limiting the available approaches that are suitable to produce integrated cardiovascular organoids. In this work we propose a novel hybrid strategy based on 3D bioprinting, to fabricate endothelialized myocardium. Enabled by the use of our composite bioink, endothelial cells directly bioprinted within microfibrous hydrogel scaffolds gradually migrated towards the peripheries of the microfibers to form a layer of confluent endothelium. Together with controlled anisotropy, this 3D endothelial bed was then seeded with cardiomyocytes to generate aligned myocardium capable of spontaneous and synchronous contraction. We further embedded the organoids into a specially designed microfluidic perfusion bioreactor to complete the endothelialized-myocardium-on-a-chip platform for cardiovascular toxicity evaluation. Finally, we demonstrated that such a technique could be translated to human cardiomyocytes derived from induced pluripotent stem cells to construct endothelialized human myocardium. We believe that our method for generation of endothelialized organoids fabricated through an innovative 3D bioprinting technology may find widespread applications in regenerative medicine, drug screening, and potentially disease modeling.
Organ-on-a-chip systems are miniaturized microfluidic 3D human tissue and organ models designed to recapitulate the important biological and physiological parameters of their in vivo counterparts. ...They have recently emerged as a viable platform for personalized medicine and drug screening. These in vitro models, featuring biomimetic compositions, architectures, and functions, are expected to replace the conventional planar, static cell cultures and bridge the gap between the currently used preclinical animal models and the human body. Multiple organoid models may be further connected together through the microfluidics in a similar manner in which they are arranged in vivo, providing the capability to analyze multiorgan interactions. Although a wide variety of human organ-on-a-chip models have been created, there are limited efforts on the integration of multisensor systems. However, in situ continual measuring is critical in precise assessment of the microenvironment parameters and the dynamic responses of the organs to pharmaceutical compounds over extended periods of time. In addition, automated and noninvasive capability is strongly desired for long-term monitoring. Here, we report a fully integrated modular physical, biochemical, and optical sensing platform through a fluidics-routing breadboard, which operates organ-on-a-chip units in a continual, dynamic, and automated manner. We believe that this platform technology has paved a potential avenue to promote the performance of current organ-on-a-chip models in drug screening by integrating a multitude of real-time sensors to achieve automated in situ monitoring of biophysical and biochemical parameters.
The inadequacy of animal models in correctly predicting drug and biothreat agent toxicity in humans has resulted in a pressing need for in vitro models that can recreate the in vivo scenario. One of ...the most important organs in the assessment of drug toxicity is liver. Here, we report the development of a liver-on-a-chip platform for long-term culture of three-dimensional (3D) human HepG2 C3A spheroids for drug toxicity assessment. The bioreactor design allowed for in situ monitoring of the culture environment by enabling direct access to the hepatic construct during the experiment without compromising the platform operation. The engineered bioreactor could be interfaced with a bioprinter to fabricate 3D hepatic constructs of spheroids encapsulated within photocrosslinkable gelatin methacryloyl (GelMA) hydrogel. The engineered hepatic construct remained functional during the 30 days culture period as assessed by monitoring the secretion rates of albumin, alpha-1 antitrypsin, transferrin, and ceruloplasmin, as well as immunostaining for the hepatocyte markers, cytokeratin 18, MRP2 bile canalicular protein and tight junction protein ZO-1. Treatment with 15 mM acetaminophen induced a toxic response in the hepatic construct that was similar to published studies on animal and other in vitro models, thus providing a proof-of-concept demonstration of the utility of this liver-on-a-chip platform for toxicity assessment.
Liver disease affects millions of patients each year. The field of regenerative medicine promises alternative therapeutic approaches, including the potential to bioengineer replacement hepatic ...tissue. One approach combines cells with acellular scaffolds derived from animal tissue. The goal of this study was to scale up our rodent liver decellularization method to livers of a clinically relevant size. Porcine livers were cannulated via the hepatic artery, then perfused with PBS, followed by successive Triton X-100 and SDS solutions in saline buffer. After several days of rinsing, decellularized liver samples were histologically analyzed. In addition, biopsy specimens of decellularized scaffolds were seeded with hepatoblastoma cells for cytotoxicity testing or implanted s.c. into rodents to investigate scaffold immunogenicity. Histological staining confirmed cellular clearance from pig livers, with removal of nuclei and cytoskeletal components and widespread preservation of structural extracellular molecules. Scanning electron microscopy confirmed preservation of an intact liver capsule, a porous acellular lattice structure with intact vessels and striated basement membrane. Liver scaffolds supported cells over 21 days, and no increased immune response was seen with either allogeneic (rat-into-rat) or xenogeneic (pig-into-rat) transplants over 28 days, compared with sham–operated on controls. These studies demonstrate that successful decellularization of the porcine liver could be achieved with protocols developed for rat livers, yielding nonimmunogenic scaffolds for future hepatic bioengineering studies.
Abstract Donor shortage remains a continued challenge in liver transplantation. Recent advances in tissue engineering have provided the possibility of creating functional liver tissues as an ...alternative to donor organ transplantation. Small bioengineered liver constructs have been developed, however a major challenge in achieving functional bioengineered liver in vivo is the establishment of a functional vasculature within the scaffolds. Our overall goal is to bioengineer intact livers, suitable for transplantation, using acellular porcine liver scaffolds. We developed an effective method for reestablishing the vascular network within decellularized liver scaffolds by conjugating anti-endothelial cell antibodies to maximize coverage of the vessel walls with endothelial cells. This procedure resulted in uniform endothelial attachment throughout the liver vasculature extending to the capillary bed of the liver scaffold and greatly reduced platelet adhesion upon blood perfusion in vitro . The re-endothelialized livers, when transplanted to recipient pigs, were able to withstand physiological blood flow and maintained for up to 24 h. This study demonstrates, for the first time, that vascularized bioengineered livers, of clinically relevant size, can be transplanted and maintained in vivo , and represents the first step towards generating engineered livers for transplantation to patients with end-stage liver failure.
Autologous urothelial cells are often obtained via bladder biopsy to generate the bio-engineered urethra or bladder, while urine-derived stem cells (USC) can be obtained by a non-invasive approach. ...The objective of this study is to develop an optimal strategy for urothelium with permeability barrier properties using human USC which could be used for tissue repair in the urinary tract system.
USC were harvested from six healthy adult individuals. To optimize urothelial differentiation, five different differentiation methods were studied. The induced cells were assessed for gene and protein expression markers of urothelial cells via RT-PCR, Western blotting, and immunofluorescent staining. Barrier function and ultrastructure of the tight junction were assessed with permeability assays and transmission electron microscopy (TEM). Induced cells were both cultured on trans-well membranes and small intestinal submucosa, then investigated under histology analysis.
Differentiated USC expressed significantly higher levels of urothelial-specific transcripts and proteins (Uroplakin III and Ia), epithelial cell markers (CK20 and AE1/AE3), and tight junction markers (ZO-1, ZO-2, E-cadherin, and Cingulin) in a time-dependent manner, compared to non-induced USC. In vitro assays using fluorescent dye demonstrated a significant reduction in permeability of differentiated USC. In addition, transmission electron microscopy confirmed appropriate ultrastructure of urothelium differentiated from USC, including tight junction formation between neighboring cells, which was similar to positive controls. Furthermore, multilayered urothelial tissues formed 2 weeks after USC were differentiated on intestine submucosal matrix.
The present study illustrates an optimal strategy for the generation of differentiated urothelium from stem cells isolated from the urine. The induced urothelium is phenotypically and functionally like native urothelium and has proposed uses in in vivo urological tissue repair or in vitro urethra or bladder modeling.
Tissue engineering and cell based liver therapies have utilized primary hepatocytes with limited success due to the failure of hepatocytes to maintain their phenotype in vitro. In order to overcome ...this challenge, hyaluronic acid (HA) cell culture substrates were formulated to closely mimic the composition and stiffness of the normal liver cellular microenvironment. The stiffness of the substrate was modulated by adjusting HA hydrogel crosslinking. Additionally, the repertoire of bioactive molecules within the HA substrate was bolstered by supplementation with normal liver extracellular matrix (ECM). Primary human hepatocyte viability and phenotype were determined over a narrow physiologically relevant range of substrate stiffnesses from 600 to 4600Pa in both the presence and absence of liver ECM. Cell attachment, viability, and organization of the actin cytoskeleton improved with increased stiffness up to 4600Pa. These differences were not evident in earlier time points or substrates containing only HA. However, gene expression for the hepatocyte markers hepatocyte nuclear factor 4 alpha (HNF4α) and albumin significantly decreased on the 4600Pa stiffness at day 7 indicating that cells may not have maintained their phenotype long-term at this stiffness. Function, as measured by albumin secretion, varied with both stiffness and time in culture and peaked at day 7 at the 1200Pa stiffness, slightly below the stiffness of normal liver ECM at 3000Pa. Overall, gel stiffness affected primary human hepatocyte cell adhesion, functional marker expression, and morphological characteristics dependent on both the presence of liver ECM in gel substrates and time in culture.
Organoid and organ-on-a-chip technologies are rapidly advancing towards deployment for drug and toxicology screening applications. Liver and cardiac toxicities account for the majority of drug ...candidate failures in human trials. Liver toxicity generally produces liver cell death, while cardiac toxicity causes adverse changes in heart beat kinetics. In traditional 2D cultures, beating kinetics can be measured by electrode arrays, but in some 3D constructs, quantifying beating kinetics can be more challenging. For example, real time measurements of calcium flux or contractile forces are possible, yet rather complex. In this communication article, we demonstrate a simple sensing system based on software code that optically analyzes video capture files of beating cardiac organoids, translates these files in representations of moving pixels, and quantifies pixel movement activity over time to generate beat kinetic plots. We demonstrate this system using bioengineered cardiac organoids under baseline and drug conditions. This technology offers a non-invasive, low-cost, and incredibly simple method for tracking and quantifying beating behavior in cardiac organoids and organ-on-a-chip systems for drug and toxicology screening.
Summary
Regenerative medicine is poised to become a significant industry within the medical field. As such, the development of strategies and technologies for standardized and automated regenerative ...medicine clinical manufacturing has become a priority. An industry‐driven roadmap toward industrial scale clinical manufacturing was developed over a 3‐year period by a consortium of companies with significant investment in the field of regenerative medicine. Additionally, this same group identified critical roadblocks that stand in the way of advanced, large‐scale regenerative medicine clinical manufacturing. This perspective article details efforts to reach a consensus among industry stakeholders on the shortest pathway for providing access to regenerative medicine therapies for those in need, both within the United States and around the world. Stem Cells Translational Medicine 2018;7:564–568
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