Scaffold-based bone tissue engineering in microgravity: potential, concerns and implications

Abstract

One of humanity’s greatest challenges is space exploration, which requires an in-depth analysis of the data continuously collected as a necessary input to fill technological gaps and move forward in several research sectors. Focusing on space crew healthcare, a critical issue to be addressed is tissue regeneration in extreme conditions. In general, it represents one of the hottest and most compelling goals of the scientific community and the development of suitable therapeutic strategies for the space environment is an urgent need for the safe planning of future long-term manned space missions. Osteopenia is a commonly diagnosed disease in astronauts due to the physiological adaptation to altered gravity conditions. In order to find specific solutions to bone damage in a reduced gravity environment, bone tissue engineering is gaining a growing interest. With the aim to critically investigate this topic, the here presented review reports and discusses bone tissue engineering scenarios in microgravity, from scaffolding to bioreactors. The literature analysis allowed to underline several key points, such as the need for (i) biomimetic composite scaffolds to better mimic the natural microarchitecture of bone tissue, (ii) uniform simulated microgravity levels for standardized experimental protocols to expose biological materials to the same testing conditions, and (iii) improved access to real microgravity for scientific research projects, supported by the so-called democratization of space.

Bioceramics/Electrospun Polymeric Nanofibrous and Carbon Nanofibrous Scaffolds for Bone Tissue Engineering Applications

“…Due to the nature of each material, it has advantages or disadvantages, and the choice of a biomaterial is influenced by how closely the biomechanical qualities match those of the implantation location [ 78 ]. In addition, the optimal biomaterial needs to be osteoconductive in vivo, printable, biodegradable, and non-cytotoxic [ 2 ].…”

“…High strength and biocompatibility can be found in metals (such as titanium alloys) and inert ceramics (such as alumina and zirconia), but their usefulness in tissue engineering applications is limited due to their inability to degrade. It has been suggested to employ biodegradable metallic alloys, such as those based on magnesium, iron, and zinc, to get around this restriction [ 78 , 83 ]. Because of their resemblance to the mineral phase of bone, bioactive ceramics (such as hydroxyapatite (HA), tricalcium phosphate, and bioactive glasses) and their combinations have been used extensively.…”

“…From a practical perspective, because of the unique properties of the biomaterial, scaffolds made from that material may have a number of disadvantages. The goal of composite biomaterials is to increase the processability, mechanical qualities, and bioactivity of the final scaffolds in order to better mimic certain traits of the target tissue (e.g., bone), as biological tissues can be thought of as natural composites [ 78 , 86 ]. So, in order to mimic the chemical makeup and mechanical characteristics of bone, composite bone scaffolds may blend inorganic compounds such as bioceramics with organic polymers, such as collagen [ 78 ].…”

“…the chemical makeup and mechanical characteristics of bone, composite bone scaffolds may blend inorganic compounds such as bioceramics with organic polymers, such as collagen [78].…”

Development and Characterization of a low intensity vibrational system for microgravity studies

“…Simulated microgravity experiments, particularly those employing low-and high-intensity vibrational bioreactors, have shown promise in mitigating some of the adverse physiological effects of simulated microgravity 16,17,[19][20][21][22][23][24][25][26][27] . In addition, pharmacological treatments for bone loss resulting from exposure to microgravity are also being tackled and researched in both real and simulated microgravity 10,11,28 .…”