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Heart disease is the leading cause of death worldwide and imposes a significant burden on healthcare systems globally. A major hurdle to the development of more effective therapeutics is the reliance on animal models that fail to faithfully recapitulate human pathophysiology. The predictivity of in vitro models that lack the complexity of in vivo tissue remain poor as well. To combat these issues, researchers are developing organ-on-a-chip models of the heart that leverage the use of human induced pluripotent stem cell-derived cardiomyocytes in combination with novel platforms engineered to better recapitulate tissue- and organ-level physiology. The integration of novel biosensors into these platforms is also a critical step in the development of these models, as they allow for increased throughput, real-time and longitudinal phenotypic assessment, and improved efficiency during preclinical disease modeling and drug screening studies. These platforms hold great promise for both improving our understanding of heart disease as well as for screening potential therapeutics based on clinically relevant endpoints with better predictivity of clinical outcomes. In this review, we describe state-of-the-art heart-on-a-chip platforms, the integration of novel biosensors into these models for real-time and continual monitoring of tissue-level physiology, as well as their use for modeling heart disease and drug screening applications. We also discuss future perspectives and further advances required to enable clinical trials-on-a-chip and next-generation precision medicine platforms.

Prior to cancer cell invasion, the structure of the extracellular matrix (ECM) surrounding the tumor is remodeled, such that circumferentially oriented matrix fibers become radially aligned. This predisposed radially aligned matrix structure serves as a critical regulator of cancer invasion. However, a biomimetic 3D model recapitulating a tumor's behavioral response to these ECM structures is not yet available. In this study, we have developed a phase-specific, force-guided method to establish a 3D dual topographical tumor model in which each tumor spheroid/organoid is surrounded by radially aligned collagen I fibers on one side and circumferentially oriented fibers on the opposite side. A coaxial rotating cylinder system was employed to construct the dual fiber topography and to pre-seed tumor spheroids/organoids within a single device. This system enables the application of different force mechanisms in the nucleation and elongation phases of collagen fiber polymerization to guide fiber alignment . In the nucleation phase, fiber alignment is enhanced by a horizontal laminar Couette flow driven by the inner cylinder rotation . In the elongation phase, fiber growth is guided by a vertical gravitational force to form a large aligned collagen matrix gel (35 × 25 × 0.5 mm) embedded with >1000 tumor spheroids. The fibers above each tumor spheroid are radially aligned along the direction of gravitational force in contrast to the circumferentially oriented fibers beneath each tumor spheroid/organoid, where the presence of the tumor interferes with the gravity-induced fiber alignment. After tumor invasion, there are more disseminated multicellular clusters on the radially aligned side, compared to the side of the tumor spheroid/organoid facing circumferentially oriented fibers. These results indicate that our 3D dual topographical model recapitulates the preference of tumors to invade and disseminate along radially aligned fibers. We anticipate that this 3D dual topographical model will have broad utility to those studying collective tumor invasion and that it has the potential to identify cancer invasion-targeted therapeutic agents.

Cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs) offer tremendous potential when used to engineer human tissues for drug screening and disease modeling; however, phenotypic immaturity reduces assay reliability when translating in vitro results to clinical studies. To address this, we have developed hybrid hydrogels comprised of decellularized porcine myocardial extracellular matrix (dECM) and reduced graphene oxide (rGO) to provide a more instructive microenvironment for proper cell and tissue development. A tissue-specific protein profile was preserved post-decellularization, and through the modulation of rGO content and degree of reduction, the mechanical and electrical properties of the hydrogels could be tuned. Engineered heart tissues (EHTs) generated using dECM-rGO hydrogel scaffolds and hiPSC-derived cardiomyocytes exhibited significantly increased twitch forces and had increased expression of genes that regulate contractile function. Improvements in various aspects of electrophysiological function, such as calcium-handling, action potential duration, and conduction velocity, were also induced by the hybrid biomaterial. dECM-rGO hydrogels could also be used as a bioink to print cardiac tissues in a high-throughput manner, and these tissues were utilized to assess the proarrhythmic potential of cisapride. Action potential prolongation and beat interval irregularities was observed in dECM-rGO tissues at clinical doses of cisapride, indicating that the enhanced electrophysiological function of these tissues corresponded well with a capability to produce physiologically relevant drug responses.

Three-dimensional microelectrode arrays (3D MEAs) have emerged as promising tools to detect electrical activities of tissues or organs in vitro and in vivo, but challenges in achieving fast, accurate, and versatile monitoring have consistently hampered further advances in analyzing cell or tissue behaviors. In this review, we discuss emerging 3D MEA technologies for in vitro recording of cardiac and neural cellular electrophysiology, as well as in vivo applications for heart and brain health diagnosis and therapeutics. We first review various forms of recent 3D MEAs for in vitro studies in context of their geometry, materials, and fabrication processes as well as recent demonstrations of 3D MEAs to monitor electromechanical behaviors of cardiomyocytes and neurons. We then present recent advances in 3D MEAs for in vivo applications to the heart and the brain for monitoring of health conditions and stimulation for therapy. A brief overview of the current challenges and future directions of 3D MEAs are provided to conclude the review.

Coordinated extracellular matrix spatiotemporal reorganization helps regulate cellular differentiation, maturation, and function in vivo, and is therefore vital for the correct formation, maintenance, and healing of complex anatomic structures. In order to evaluate the potential for cultured cells to respond to dynamic changes in their in vitro microenvironment, as they do in vivo, the collective behavior of primary cardiac muscle cells cultured on nanofabricated substrates with controllable anisotropic topographies was studied. A thermally induced shape memory polymer (SMP) was employed to assess the effects of a 90° transition in substrate pattern orientation on the contractile direction and structural organization of cardiomyocyte sheets. Cardiomyocyte sheets cultured on SMPs exhibited anisotropic contractions before shape transition. 48 hours after heat-induced shape transition, the direction of cardiomyocyte contraction reoriented significantly and exhibited a bimodal distribution, with peaks at ~ 45 and −45 degrees (P < 0.001). Immunocytochemical analysis highlighted the significant structural changes that the cells underwent in response to the shift in underlying topography. The presented results demonstrate that initial anisotropic nanotopographic cues do not permanently determine the organizational fate or contractile properties of cardiomyocytes in culture. Given the importance of surface cues in regulating primary and stem cell development, investigation of such tunable nanotopographies may have important implications for advancing cellular maturation and performance in vitro, as well as improving our understanding of cellular development in response to dynamic biophysical cues.

The aim of this study is to elucidate the relationship of laryngeal electromyography (LEMG) and computed tomographic (CT) parameters to improve the prognosis of recurrent laryngeal nerve injury. 22 patients clinically suspected of having recurrent laryngeal nerve injury were examined with LEMG and CT studies. Bilateral thyroarytenoid (TA) muscles were examined and findings were interpreted by a single blind technique. Laryngeal CT image analysis of the ventricle dilation symmetry determined TA muscle atrophy. Finally, a follow-up laryngoscopic examination determined improvement of vocal fold movement. Ventricle dilation symmetry and the dichotomized TA muscle atrophy parameter significantly relate to the improvement of vocal fold movement ( χ 2 =4.029, P =0.039, and χ 2 =3.912, P =0.048, respectively). When the severity of vocal fold impairment was classified as severe TA muscle atrophy or none/discrete MUAP recruitment, it was found to significantly relate with the improvement of vocal fold movement ( χ 2 =6.712, P =.010). From this study, image analysis of the ventricle dilation symmetry to determine the severity of TA muscle atrophy shows promise for the improved prognosis of vocal fold immobility.

Adult stem cells hold great promise as a source of diverse terminally differentiated cell types for tissue engineering applications. However, due to the complexity of chemical and mechanical cues specifying differentiation outcomes, development of arbitrarily complex geometric and structural arrangements of cells, adopting multiple fates from the same initial stem cell population, has been difficult. Here, we show that the topography of the cell adhesion substratum can be an instructive cue to adult stem cells and topographical variations can strongly bias the differentiation outcome of the cells towards adipocyte or osteocyte fates. Switches in cell fate decision from adipogenic to osteogenic lineages were accompanied by changes in cytoskeletal stiffness, spanning a considerable range in the cell softness/rigidity spectrum. Our findings suggest that human mesenchymal stem cells (hMSC) can respond to the varying density of nanotopographical cues by regulating their internal cytoskeletal network and use these mechanical changes to guide them toward making cell fate decisions. We used this finding to design a complex two-dimensional pattern of co-localized cells preferentially adopting two alternative fates, thus paving the road for designing and building more complex tissue constructs with diverse biomedical applications.

Duchenne Muscular Dystrophy (DMD) is a wasting disease of striated muscle resulting from membrane fragility. We modeled DMD cardiac disease using urine-derived cells from a patient, reprogrammed to induced pluripotent stem cells (hiPSCs) and differentiated into cardiomyocytes (DMD-hiPSC-CMs). DMD-hiPSC-CMs were dystrophin-deficient (exon 50 deletion) and manifested physiological consequences of the disease such as calcium-handling abnormalities. Here we report, for the first time, isolation and functional characterization of myofibrils from hiPSC-CMs to study DMD cardiomyopathy.At day 20 post-differentiation, DMD-hiPSC-CMs and control hiPSC-CMs (from a healthy volunteer) were replated onto fibronectin-coated nanopatterned coverslides and cultured until day 80. Both DMD- and controls-CMs exhibited more mature morphology with aligned myofibrils and clearly defined Z-bands, cell lengths of 100-150µm and widths of 40µm. For mechanical measurements, cells were harvested and skinned in a rigor solution containing Triton 1% for 5 minutes.Control hiPSC-CM myofibrils had mechanical and kinetic proporties more similar to human fetal skeletal (Racca, 2013) or cardiac myofibrils than human adult cardiac myofibrils. Preliminary data for DMD-hiPSC-CMs showed lower force development, prolonged duration of early, slow phase relaxation kinetics (tREL slow), but no differences in the other kinetic properties. Preliminary data from intact DMD-hiPSC-CMs paced at 1Hz showed no difference in the rate of cell shortening, but depressed magnitude and prolonged relaxation (t50). We previously reported (Xuan G, 2014) prolongation of Ca2+ transient decay.Together these data suggest DMD-hiPSC-CMs have slower relaxation due to both myofibril properties and Ca2+ sequestration, compared with control hiPSC-CMs, and both cell lines have myofibril mechanic and kinetic properties more similar to fetal than adult myofibrils.In conclusion, we demonstrated that isolated functional myofibrils from hiPSC-CMs can be obtained after growing on nano-patterned surfaces in culture to study cardiac diseases in vitro.