Advances in Microgravity Directed Tissue Engineering.

Tissue engineering aims to generate functional biological substitutes to repair, sustain, improve, or replace tissue function affected by disease. With the rapid development of space science, the application of simulated microgravity has become an active topic in the field of tissue engineering. There is a growing body of evidence demonstrating that microgravity offers excellent advantages for tissue engineering by modulating cellular morphology, metabolism, secretion, proliferation, and stem cell differentiation. To date, there have been many achievements in constructing bioartificial spheroids, organoids, or tissue analogs with or without scaffolds in vitro under simulated microgravity conditions. Herein, the current status, recent advances, challenges, and prospects of microgravity related to tissue engineering are reviewed. Current simulated-microgravity devices and cutting-edge advances of microgravity for biomaterials-dependent or biomaterials-independent tissue engineering to offer a reference for guiding further exploration of simulated microgravity strategies to produce engineered tissues are summarized and discussed.

Spinal cord tissue engineering via covalent interaction between biomaterials and cells.

Noncovalent interactions between cells and environmental cues have been recognized as fundamental physiological interactions that regulate cell behavior. However, the effects of the covalent interactions between cells and biomaterials on cell behavior have not been examined. Here, we demonstrate a combined strategy based on covalent conjugation between biomaterials (collagen fibers/lipid nanoparticles) and various cells (exogenous neural progenitor cells/astrocytes/endogenous tissue-resident cells) to promote neural regeneration after spinal cord injury (SCI). We found that metabolic azido-labeled human neural progenitor cells conjugated on dibenzocyclooctyne-modified collagen fibers significantly promoted cell adhesion, spreading, and differentiation compared with noncovalent adhesion. In addition, dibenzocyclooctyne-modified lipid nanoparticles containing edaravone, a well-known ROS scavenger, could target azide-labeled spinal cord tissues or transplanted azide-modified astrocytes to improve the SCI microenvironment. The combined application of these covalent conjugation strategies in a rat SCI model boosted neural regeneration, suggesting that the covalent interactions between cells and biomaterials have great potential for tissue regeneration.