Roadblocks confronting widespread dissemination and deployment of Organs on Chips.

Organ on Chip platforms hold significant promise as alternatives to animal models or traditional cell cultures, both of which poorly recapitulate human pathophysiology and human level responses. Within the last 15 years, we have witnessed seminal scientific developments from academic laboratories, a flurry of startups and investments, and a genuine interest from pharmaceutical industry as well as regulatory authorities to translate these platforms. This Perspective identifies several fundamental design and process features that may act as roadblocks that prevent widespread dissemination and deployment of these systems, and provides a roadmap to help position this technology in mainstream drug discovery.

SliceChip: a benchtop fluidic platform for organotypic culture and serial assessment of human and rodent pancreatic slices.

Enzymatically isolated pancreatic islets are the most commonly used ex vivo testbeds for diabetes research. Recently, precision-cut living slices of human pancreas are emerging as an exciting alternative because they maintain the complex architecture of the endocrine and exocrine tissues, and do not suffer from the mechanical and chemical stress of enzymatic isolation. We report a fluidic pancreatic SliceChip platform with dynamic environmental controls that generates a warm, oxygenated, and bubble-free fluidic pathway across singular immobilized slices with continuous deliver of fresh media and the ability to perform repeat serial perfusion assessments. A degasser ensures the system remains bubble-free while systemic pressurization with compressed oxygen ensures slice medium remains adequately oxygenated. Computational modeling of perfusion and oxygen dynamics within SliceChip guide the system's physiomimetic culture conditions. Maintenance of the physiological glucose dependent insulin secretion profile across repeat perfusion assessments of individual pancreatic slices kept under physiological oxygen levels demonstrated the culture capacity of our platform. Fluorescent images acquired every 4 hours of transgenic murine pancreatic slices were reliably stable and recoverable over a 5 day period due to the inclusion of a 3D-printed bioinert metallic anchor that maintained slice position within the SliceChip. Our slice on a chip platform has the potential to expand the useability of human pancreatic slices for diabetes pathogenesis and the development of new therapeutic approaches, while also enabling organotypic culture and assessment of other tissue slices such as brain and patient tumors.

Spermatogonial Stem Cells and In Vitro Spermatogenesis: How Far Are We from a Human Testis on a Chip?

An in vitro testis model will provide a superior platform for studying the testis microenvironment and molecular mechanisms that affect male fertility. The ultimate aim is to provide reproductive hope for children diagnosed with cancer who were sterilized by aggressive gonadotoxic therapies.

Acrylic-based culture plate format perfusion device to establish liver endothelial-epithelial interface.

Microphysiological Systems (MPSs) or organs-on-chips, are microfluidic devices used to model human physiology in vitro. Polydimethylsiloxane (PDMS) is the most widely used material for organs-on-chips due to its established fabrication methods and biocompatibility properties. However, non-specific binding of small molecules limits PDMS for drug screening applications. Here, we designed a novel acrylic-based MPS to capture the physiological architecture that is observed universally in tissues across the body: the endothelial-epithelial interface (EEI). To reconstruct the EEI biology, we designed a membrane-based chip that features endothelial cells on the underside of the membrane exposed to mechanical shear from the path of media flow, and epithelial cells on the opposite side of the membrane protected from flow, as they are in vivo. We used a liver model with a hepatic progenitor cell line and human umbilical vein endothelial cells to assess the biological efficacy of the MPS. We computationally modeled the physics that govern the function of perfusion through the MPS. Empirically, efficacy was measured by comparing differentiation of the hepatic progenitor cells between the MPS and 2D culture conditions. We demonstrated that the MPS significantly improved hepatocyte differentiation, increased extracellular protein transport, and raised hepatocyte sensitivity to drug treatment. Our results strongly suggest that physiological perfusion has a profound effect on proper hepatocyte function, and the modular chip design motivates opportunities for future study of multi-organ interactions.

Muscle tissue engineering in fibrous gelatin: implications for meat analogs.

Bioprocessing applications that derive meat products from animal cell cultures require food-safe culture substrates that support volumetric expansion and maturation of adherent muscle cells. Here we demonstrate scalable production of microfibrous gelatin that supports cultured adherent muscle cells derived from cow and rabbit. As gelatin is a natural component of meat, resulting from collagen denaturation during processing and cooking, our extruded gelatin microfibers recapitulated structural and biochemical features of natural muscle tissues. Using immersion rotary jet spinning, a dry-jet wet-spinning process, we produced gelatin fibers at high rates (~ 100 g/h, dry weight) and, depending on process conditions, we tuned fiber diameters between ~ 1.3 ± 0.1 µm (mean ± SEM) and 8.7 ± 1.4 µm (mean ± SEM), which are comparable to natural collagen fibers. To inhibit fiber degradation during cell culture, we crosslinked them either chemically or by co-spinning gelatin with a microbial crosslinking enzyme. To produce meat analogs, we cultured bovine aortic smooth muscle cells and rabbit skeletal muscle myoblasts in gelatin fiber scaffolds, then used immunohistochemical staining to verify that both cell types attached to gelatin fibers and proliferated in scaffold volumes. Short-length gelatin fibers promoted cell aggregation, whereas long fibers promoted aligned muscle tissue formation. Histology, scanning electron microscopy, and mechanical testing demonstrated that cultured muscle lacked the mature contractile architecture observed in natural muscle but recapitulated some of the structural and mechanical features measured in meat products.