Building blocks of microphysiological system to model physiology and pathophysiology of human heart.

Microphysiological systems (MPS) are drawing increasing interest from academia and from biomedical industry due to their improved capability to capture human physiology. MPS offer an advanced in vitro platform that can be used to study human organ and tissue level functions in health and in diseased states more accurately than traditional single cell cultures or even animal models. Key features in MPS include microenvironmental control and monitoring as well as high biological complexity of the target tissue. To reach these qualities, cross-disciplinary collaboration from multiple fields of science is required to build MPS. Here, we review different areas of expertise and describe essential building blocks of heart MPS including relevant cardiac cell types, supporting matrix, mechanical stimulation, functional measurements, and computational modelling. The review presents current methods in cardiac MPS and provides insights for future MPS development with improved recapitulation of human physiology.

Hyaluronic acid based next generation bioink for 3D bioprinting of human stem cell derived corneal stromal model with innervation.

Corneal transplantation remains gold standard for the treatment of severe cornea diseases, however, scarcity of donor cornea is a serious bottleneck. 3D bioprinting holds tremendous potential for cornea tissue engineering (TE). One of the key technological challenges is to design bioink compositions with ideal printability and cytocompatibility. Photo-crosslinking and ionic crosslinking are often used for the stabilization of 3D bioprinted structures, which can possess limitations on biological functionality of the printed cells. Here, we developed a hyaluronic acid-based dopamine containing bioink using hydrazone crosslinking chemistry for the 3D bioprinting of corneal equivalents. First, the shear thinning property, viscosity, and mechanical stability of the bioink were optimized before extrusion-based 3D bioprinting for the shape fidelity and self-healing property characterizations. Subsequently, human adipose stem cells (hASCs) and hASC-derived corneal stromal keratocytes were used for bioprinting corneal stroma structures and their cell viability, proliferation, microstructure and expression of key proteins (lumican, vimentin, connexin 43,α-smooth muscle actin) were evaluated. Moreover, 3D bioprinted stromal structures were implanted intoex vivoporcine cornea to explore tissue integration. Finally, human pluripotent stem cell derived neurons (hPSC-neurons), were 3D bioprinted to the periphery of the corneal structures to analyze innervation. The bioink showed excellent shear thinning property, viscosity, printability, shape fidelity and self-healing properties with high cytocompatibility. Cells in the printed structures displayed good tissue formation and 3D bioprinted cornea structures demonstrated excellentex vivointegration to host tissue as well asin vitroinnervation. The developed bioink and the printed cornea stromal equivalents hold great potential for cornea TE applications.

Novel method to produce a layered 3D scaffold for human pluripotent stem cell-derived neuronal cells.

BACKGROUND: Three-dimensional (3D) in vitro models have been developed into more in vivo resembling structures. In particular, there is a need for human-based models for neuronal tissue engineering (TE). To produce such a model with organized microenvironment for cells in central nervous system (CNS), a 3D layered scaffold composed of hydrogel and cell guiding fibers has been proposed. NEW METHOD: Here, we describe a novel method for producing a layered 3D scaffold consisting of electrospun poly (L,D-lactide) fibers embedded into collagen 1 hydrogel to achieve better resemblance of cells' natural microenvironment for human pluripotent stem cell (hPSC)-derived neurons. The scaffold was constructed via a single layer-by-layer process using an electrospinning technique with a unique collector design. RESULTS: The method enabled the production of layered 3D cell-containing scaffold in a single process. HPSC-derived neurons were found in all layers of the scaffold and exhibited a typical neuronal phenotype. The guiding fiber layers supported the directed cell growth and extension of the neurites inside the scaffold without additional functionalization. COMPARISON WITH EXISTING METHODS: Previous methods have required several process steps to construct 3D layer-by-layer scaffolds. CONCLUSIONS: We introduced a method to produce layered 3D scaffolds to mimic the cell guiding cues in CNS by alternating the soft hydrogel matrix and fibrous guidance cues. The produced scaffold successfully enabled the long-term culture of hPSC-derived neuronal cells. This layered 3D scaffold is a useful model for in vitro and in vivo neuronal TE applications.