The protist cultural renaissance.

Protists are key players in the biosphere. Here, we provide a perspective on integrating protist culturing with omics approaches, imaging, and high-throughput single-cell manipulation strategies, concluding with actions required for a successful return of the golden age of protist culturing.

Correction to: Current strategies of mechanical stimulation for maturation of cardiac microtissues.

[This corrects the article DOI: 10.1007/s12551-021-00841-6.].

3D Printed Dual-Porosity Scaffolds: The Combined Effect of Stiffness and Porosity in the Modulation of Macrophage Polarization.

Tissue regeneration evolves toward the biofabrication of sophisticated 3D scaffolds. However, the success of these will be contingent to their capability to integrate within the host. The control of the mechanical or topographical properties of the implant appears as an ideal method to modulate the immune response. However, the interplay between these properties is yet not clear. Dual-porosity scaffolds with varying mechanical and topographical features are created, and their immunomodulatory properties in rat alveolar macrophages in vitro and in vivo in a rat subcutaneous model are evaluated. Scaffolds are fabricated via additive manufacturing and thermally induced phase separation methods from two copolymers with virtually identical chemistries, but different stiffness. The introduction of porosity enables the modulation of macrophages toward anti-inflammatory phenotypes, with secretion of IL-10 and TGF-ß. Soft scaffolds (<5 kPa) result in a pro-inflammatory phenotype in contrast to stiffer (>40 kPa) scaffolds of comparable porosities supporting a pro-healing phenotype, which appears to be related to the surface spread area of cells. In vivo, stiff scaffolds integrate, while softer scaffolds appear encapsulated after three weeks of implantation, resulting in chronic inflammation after six weeks. The results demonstrate the importance of evaluating the interplay between topography and stiffness of candidate scaffolds.

Current strategies of mechanical stimulation for maturation of cardiac microtissues.

The most advanced in vitro cardiac models are today based on the use of induced pluripotent stem cells (iPSCs); however, the maturation of cardiomyocytes (CMs) has not yet been fully achieved. Therefore, there is a rising need to move towards models capable of promoting an adult-like cardiomyocytes phenotype. Many strategies have been applied such as co-culture of cardiomyocytes, with fibroblasts and endothelial cells, or conditioning them through biochemical factors and physical stimulations. Here, we focus on mechanical stimulation as it aims to mimic the different mechanical forces that heart receives during its development and the post-natal period. We describe the current strategies and the mechanical properties necessary to promote a positive response in cardiac tissues from different cell sources, distinguishing between passive stimulation, which includes stiffness, topography and static stress and active stimulation, encompassing cyclic strain, compression or perfusion. We also highlight how mechanical stimulation is applied in disease modelling.