Compressive molding of engineered tissues via thermoresponsive hydrogel devices

Directed biomechanical compressive forces enhance fusion efficiency in model placental trophoblast cultures

The syncytiotrophoblast is a multinucleated structure that arises from fusion of mononucleated cytotrophoblasts, to sheath the placental villi and regulate transport across the maternal-fetal interface. Here, we ask whether the dynamic mechanical forces that must arise during villous development might influence fusion, and explore this question using in vitro choriocarcinoma trophoblast models. We demonstrate that mechanical stress patterns arise around sites of localized fusion in cell monolayers, in patterns that match computational predictions of villous morphogenesis. We then externally apply these mechanical stress patterns to cell monolayers and demonstrate that equibiaxial compressive stresses (but not uniaxial or equibiaxial tensile stresses) enhance expression of the syndecan-1 and loss of E-cadherin as markers of fusion. These findings suggest that the mechanical stresses that contribute towards sculpting the placental villi may also impact fusion in the developing tissue. We then extend this concept towards 3D cultures and demonstrate that fusion can be enhanced by applying low isometric compressive stresses to spheroid models, even in the absence of an inducing agent. These results indicate that mechanical stimulation is a potent activator of cellular fusion, suggesting novel avenues to improve experimental reproductive modelling, placental tissue engineering, and understanding disorders of pregnancy development.

Biohybrid Hydrogels for Tumoroid Culture

Tumoroids are 3D in vitro models that recapitulate key features of in vivo tumors, such as their architecture - hypoxic center and oxygenated outer layer - in contrast with traditional 2D cell cultures. Moreover, they may be able to preserve the patient-specific signature in terms of cell heterogeneity and mutations. Tumoroids are, therefore, interesting tools for improving the understanding of cancer biology, developing new drugs, and potentially designing personalized therapeutic plans. Currently, tumoroids are most often established using basement membrane extracts (BME), which provide a multitude of biological cues. However, BME are characterized by a lack of well-defined composition, limited reproducibility, and potential immunogenicity as a consequence of their natural origin. Synthetic polymers can overcome these problems but lack structural and biochemical complexity, which can limit the functional capabilities of organoids. Biohybrid hydrogels consisting of both natural and synthetic components can combine their advantages and offer superior 3D culture systems. In this review, it is summarized efforts devoted to producing tumoroids using different types of biohybrid hydrogels, which are classified according to their crosslinking mechanism.