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There is increasing evidence that surface curvature at a near-cell-scale influences cell behaviour. Epithelial or endothelial cells lining small acinar or tubular body lumens, as those of the alveoli or blood vessels, experience such highly curved surfaces. In contrast, the most commonly used culture substrates for in vitro modelling of these human tissue barriers, ion track-etched membranes, offer only flat surfaces. Here, we propose a more realistic culture environment for alveolar cells based on biomimetically curved track-etched membranes, preserving the mainly spherical geometry of the cells' native microenvironment. The curved membranes were created by a combination of three-dimensional (3D) micro film (thermo)forming and ion track technology. We could successfully demonstrate the formation, the growth and a first characterization of confluent layers of lung epithelial cell lines and primary alveolar epithelial cells on membranes shaped into an array of hemispherical microwells. Besides their application in submerged culture, we could also demonstrate the compatibility of the bioinspired membranes for air-exposed culture. We observed a distinct cellular response to membrane curvature. Cells (or cell layers) on the curved membranes reveal significant differences compared to cells on flat membranes concerning membrane epithelialization, areal cell density of the formed epithelial layers, their cross-sectional morphology, and proliferation and apoptosis rates, and the same tight barrier function as on the flat membranes. The presented 3D membrane technology might pave the way for more predictive barrier in vitro models in future., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Despite the clinical success of intrahepatic islet transplantation in treating type 1 diabetes, factors specific to this transplantation site hinder long-term insulin independence. The adoption of alternative, extravascular sites likely improve islet survival and function, but few locations are able to sufficiently confine islets in order to facilitate engraftment. This work describes a porous microwell scaffold with a well-defined pore size and spacing designed to guarantee islet retention at an extrahepatic transplantation site and facilitate islet revascularization. Three techniques to introduce pores were characterized: particulate leaching; solvent casting on pillared wafers; and laser drilling. Our criteria of a maximum pore diameter of 40 μm were best achieved via laser drilling. Transplantation studies in the epididymal fat of diabetic mice elucidated the potential of this porous scaffold platform to restore blood glucose levels and facilitate islet engraftment. Six out of eight mice reverted to stable normoglycemia with a mean time to remission of 6.2 ± 3.2 days, which was comparable to that of the gold standard of renal subcapsular islet grafts. In contrast, when islets were transplanted in the epididymal fat pad without a microwell scaffold, only two out of seven mice reverted to stable normoglycemia. Detailed histological evaluation four weeks after transplantation found a comparable vascular density in scaffold-seeded islets, renal subcapsular islets and native pancreatic islets. However, the vascularization pattern in scaffold-seeded islets was more inhomogeneous compared to native pancreatic islets with a higher vascular density in the outer shell of the islets compared to the inner core. We also observed a corresponding decrease in the beta-cell density in the islet core. Despite this, our data indicated that islets transplanted in the microwell scaffold platform were able to maintain a viable beta-cell population and restore glycemic control. Furthermore, we demonstrated that the microwell scaffold platform facilitated detailed analysis at a subcellular level to correlate design parameters with functional physiological observations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Bioactive scaffolds for tissue engineering call for demands on new materials which can enhance traditional biocompatibility requirements previously considered for clinical implantation. The current commercially available thermoplastic materials, such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL) and their copolymers, have been used to fabricate scaffolds for regenerative medicine. However, these polymers have limitations including lacking of broadly tuning mechanical and degradable properties, and activation of specific cell-scaffold interactions, which limit their further application in tissue engineering. In the present study, electrospun scaffolds were successfully fabricated from a new class of block poly(butylene succinate)-based (PBS-based) copolyesters containing either butylene thiodiglycolate (BTDG) or butylene diglycolate (BDG) sequences. The polyesters displayed tunable mechanical properties and hydrolysis rate depending on the molecular architecture and on the kind of heteroatom introduced along the polymer backbone. To investigate their potential for skeletal regeneration, human mesenchymal stromal cells (hMSCs) were cultured on the scaffolds in basic, osteogenic and chondrogenic media. Our results demonstrated that PBS-based copolyesters containing thio-ether linkages (i.e. BTDG segments) were more favorable for chondrogenesis of hMSCs than those containing ether linkages (i.e. BDG sequences). In contrast, PBS-based copolyesters containing ether linkages showed enhanced mineralization. Therefore, these new functional scaffolds might hold potential for osteochondral tissue engineering applications., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In vitro-generated tissues hold significant promise in modern biology since they can potentially mimic physiological and pathological tissues. However, these are currently structurally and functionally of limited complexity and necessitate self-organization and recapitulation of tissue development mechanisms in vitro. Tools derived from nano- and microfabrications along with bottom-up strategies are emerging to allow the fabrication of primitive tissues structures that can remodel overtime. Subsequently, clues are accumulating to show that, beyond genetic material, both intrinsic tissue architectures and microenvironmental cues can lead to morphogenesis related mechanisms in vitro. The question arises, however, as how we may design and assemble structures prone to adequate tissue remodeling, predict and manipulate those developmental mechanisms in vitro? Systems integrating architectural, physical and molecular cues will allow more systematic investigation of basic principles of tissue morphogenesis, differentiation or maintenance and will feedback to reproduce the dynamic of tissue development in vitro and form more complex tissues.