Spheroid cultures of human hepatoblastoma cells (HuH-6 line) and their application for cytotoxicity assay of alcohols

Laser-based 3D bioprinting for spatial and size control of tumor spheroids and embryoid bodies

3D multicellular aggregates, and more advanced organotypic systems, have become central tools in recent years to study a wide variety of complex biological processes. Most notably, these model systems have become mainstream within oncology (multicellular tumor spheroids) and regenerative medicine (embryoid bodies) research. However, the biological behavior of these in vitro tissue surrogates is extremely sensitive to their aggregate size and geometry. Indeed, both of these geometrical parameters are key in producing pathophysiological gradients responsible for cellular and structural heterogeneity, replicating in vivo observations. Moreover, the fabrication techniques most widely used for producing these models lack the ability to accurately control cellular spatial location, an essential component for regulating homotypic and heterotypic cell signaling. Herein, we report on a 3D bioprinting technique, laser direct-write (LDW), that enables precise control of both spatial patterning and size of cell-encapsulating microbeads. The generated cell-laden beads are further processed into core-shelled structures, allowing for the growth and formation of self-contained, self-aggregating cells (e.g., breast cancer cells, embryonic stem cells). Within these structures we demonstrate our ability to produce multicellular tumor spheroids (MCTSs) and embryoid bodies (EBs) with well-controlled overall size and shape, that can be designed on demand. Furthermore, we investigated the impact of aggregate size on the uptake of a commonly employed ligand for receptor-mediated drug delivery, Transferrin, indicating that larger tumor spheroids exhibit greater spatial heterogeneity in ligand uptake. Taken together, these findings establish LDW as a versatile biomanufacturing platform for bioprinting and patterning core-shelled structures to generate size-controlled 3D multicellular aggregates. STATEMENT OF SIGNIFICANCE: Multicellular 3D aggregates are powerful in vitro models used to study a wide variety of complex biological processes, particularly within oncology and regenerative medicine. These tissue surrogates are fabricated using environments that encourage cellular self-assembly. However, specific applications require control of aggregate size and position to recapitulate key in vivo parameters (e.g., pathophysiological gradients and homotypic/heterotypic cell signaling). Herein, we demonstrate the ability to create and spatially pattern size-controlled embryoid bodies and tumor spheroids, using laser-based 3D bioprinting. Furthermore, we investigated the effect of tumor spheroid size on internalization of Transferrin, a common ligand for targeted therapy, finding greater spatial heterogeneity in our large aggregates. Overall, this technique offers incredible promise and flexibility for fabricating idealized 3D in vitro models.

Metabolic Reprogramming and the Recovery of Physiological Functionality in 3D Cultures in Micro-Bioreactors

The recovery of physiological functionality, which is commonly seen in tissue mimetic three-dimensional (3D) cellular aggregates (organoids, spheroids, acini, etc.), has been observed in cells of many origins (primary tissues, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and immortal cell lines). This plurality and plasticity suggest that probably several basic principles promote this recovery process. The aim of this study was to identify these basic principles and describe how they are regulated so that they can be taken in consideration when micro-bioreactors are designed. Here, we provide evidence that one of these basic principles is hypoxia, which is a natural consequence of multicellular structures grown in microgravity cultures. Hypoxia drives a partial metabolic reprogramming to aerobic glycolysis and an increased anabolic synthesis. A second principle is the activation of cytoplasmic glutaminolysis for lipogenesis. Glutaminolysis is activated in the presence of hypo- or normo-glycaemic conditions and in turn is geared to the hexosamine pathway. The reducing power needed is produced in the pentose phosphate pathway, a prime function of glucose metabolism. Cytoskeletal reconstruction, histone modification, and the recovery of the physiological phenotype can all be traced to adaptive changes in the underlying cellular metabolism. These changes are coordinated by mTOR/Akt, p53 and non-canonical Wnt signaling pathways, while myc and NF-kB appear to be relatively inactive. Partial metabolic reprogramming to aerobic glycolysis, originally described by Warburg, is independent of the cell’s rate of proliferation, but is interwoven with the cells abilities to execute advanced functionality needed for replicating the tissues physiological performance.

Elasticity and safety of alkoxyethyl cyanoacrylate tissue adhesives

Cyanoacrylate glues are easily applied to wounds with good cosmetic results. However, they tend to be brittle and can induce local tissue toxicity. A series of cyanoacrylate monomers with a flexible ether linkage and varying side-chain lengths was synthesized and characterized for potential use as tissue adhesives. The effect of side-chain length on synthesis yield, physical and mechanical properties, formaldehyde generation, cytotoxicity in vitro and biocompatibility in vivo were examined. The incorporation of etheric oxygen allowed the production of flexible monomers with good adhesive strength. Monomers with longer side-chains were found to have less toxicity both in vitro and in vivo. Polymerized hexoxyethyl cyanoacrylate was more elastic than its commercially available and widely used alkyl analog 2-octyl cyanoacrylate, without compromising biocompatibility.