Basement membrane properties and their recapitulation in organ-on-chip applications.

Drug discovery and toxicology is a complex process that involves considerable basic research and preclinical evaluation. These depend highly on animal testing which often fails to predict human trial outcomes due to species differences. Coupled with ethical concerns around animal testing, this leads to a high demand for improved in vitro cell culture platforms. Current research efforts, in this regard, however, are facing a challenge to provide physiologically relevant in vitro human organ models for a reliable assessment of the physiological responses of the body to drug compounds and toxins. The latest development in in vitro cell culture models, organ-on-chips (OOCs), seek to introduce more realistic models of organ function. Current OOCs often use commercial porous polymeric membranes as a barrier membrane for cell culture which is challenging due to the poor replication of the physiological architectures. Better recapitulation of the native basement membrane (BM) characteristics is desirable for modelling physical (e.g. intestine, skin and lung) and metabolic (e.g. liver) barrier models. In this review, the relevance of the physical and mechanical properties of the membrane to cell and system behaviour is elucidated. Key parameters for replicating the BM are also described. This review provides information for future development of barrier organ models focusing on BM-mimicking substrates as a core structure.

Characterization of a novel bioreactor system for 3D cellular mechanobiology studies.

In vitro engineering systems can be powerful tools for studying tissue development in response to biophysical stimuli as well as for evaluating the functionality of engineered tissue grafts. It has been challenging, however, to develop systems that adequately integrate the application of biomimetic mechanical strain to engineered tissue with the ability to assess functional outcomes in real time. The aim of this study was to design a bioreactor system capable of real-time conditioning (dynamic, uniaxial strain, and electrical stimulation) of centimeter-long 3D tissue engineered constructs simultaneously with the capacity to monitor local strains. The system addresses key limitations of uniform sample loading and real-time imaging capabilities. Our system features an electrospun fibrin scaffold, which exhibits physiologically relevant stiffness and uniaxial alignment that facilitates cell adhesion, alignment, and proliferation. We have demonstrated the capacity for directly incorporating human adipose-derived stromal/stem cells into the fibers during the electrospinning process and subsequent culture of the cell-seeded constructs in the bioreactor. The bioreactor facilitates accurate pre-straining of the 3D constructs as well as the application of dynamic and static uniaxial strains while monitoring bulk construct tensions. The incorporation of fluorescent nanoparticles throughout the scaffolds enables in situ monitoring of local strain fields using fluorescent digital image correlation techniques, since the bioreactor is imaging compatible, and allows the assessment of local sample stiffness and stresses when coupled with force sensor measurements. In addition, the system is capable of measuring the electromechanical coupling of skeletal muscle explants by applying an electrical stimulus and simultaneously measuring the force of contraction. The packaging of these technologies, biomaterials, and analytical methods into a single bioreactor system has produced a powerful tool that will enable improved engineering of functional 3D ligaments, tendons, and skeletal muscles. Biotechnol. Bioeng. 2016;113: 1825-1837. © 2016 Wiley Periodicals, Inc.

Advanced cell therapies with and without scaffolds.

Tissue engineering and regenerative medicine aim to produce tissue substitutes to restore lost functions of tissues and organs. This includes cell therapies, induction of tissue/organ regeneration by biologically active molecules, or transplantation of in vitro grown tissues. This review article discusses advanced cell therapies that make use of scaffolds and scaffold-free approaches. The first part of this article covers the basic characteristics of scaffolds, including characteristics of scaffold material, fabrication and surface functionalization, and their applications in the construction of hard (bone and cartilage) and soft (nerve, skin, blood vessel, heart muscle) tissue substitutes. In addition, cell sources as well as bioreactive agents, such as growth factors, that guide cell functions are presented. The second part in turn, examines scaffold-free applications, with a focus on the recently discovered cell sheet engineering. This article serves as a good reference for all applications of advanced cell therapies and as well as advantages and limitations of scaffold-based and scaffold-free strategies.