The number of astronauts involved in long-lasting missions is expected to increase in the future, increasing the chances of injury due to traumatic events or unexpected emergency surgery. In addition, in future space exploration missions, medical evacuation times to earth could become very long. Therefore, tissue repair in weightlessness has become an important topic of study. Wound healing is an intricate process, which is critical for the survival of the organism. It is based on complex interactions between cells, extracellular matrix, cytokines, growth factors, physical and topographical factors and it consists of various phases. The available literature concerning wound healing in conditions of mechanical unloading presents controversial results. However, many studies indicate an impairment of the healing processes.
In this paper, we reported an overview of studies regarding the effects of weightlessness on wound healing, particularly focusing on the behavior of cells involved in the remodelling phase of repair, e.g. fibroblasts and endothelial cells. Indeed, unloading conditions can affect wound healing both indirectly, decreasing the ability of the organism to withstand injuries because of the functional alterations of many organs and systems, and directly, changing the behavior of the cells involved in inflammation, ECM remodelling and tissue regeneration. Based on the studies conducted to date, hypotheses have advanced on what might be the altered cellular and molecular mechanisms that undermine tissue repair in microgravity. Countermeasures to promote tissue repair are also proposed.
However, our knowledge on tissue regeneration patterns in weightlessness is still very limited and further studies are needed to better understand how gravitational alterations affect the healing process, thus opening the way for the development of new therapeutic strategies both for counteracting delayed tissue repair in space and treating on ground chronic wounds, healing delay or failure, fibrous scars, and other pathological conditions derived from defective repair mechanisms.