Abstract
Microgravity induces a number of significant physiological changes in the cardiovascular, nervous, immune systems, as well as the bone tissue of astronauts. Changes in cell adhesion properties are one aspect affected during long-term spaceflights in mammalian cells. Cellular adhesion behaviors can be divided into cell–cell and cell–matrix adhesion. These behaviors trigger cell–cell recognition, conjugation, migration, cytoskeletal rearrangement, and signal transduction. Cellular adhesion molecule (CAM) is a general term for macromolecules that mediate the contact and binding between cells or between cells and the extracellular matrix (ECM). In this review, we summarize the four major classes of adhesion molecules that regulate cell adhesion, including integrins, immunoglobulin superfamily (Ig-SF), cadherins, and selectin. Moreover, we discuss the effects of spaceflight and simulated microgravity on the adhesion of endothelial cells, immune cells, tumor cells, stem cells, osteoblasts, muscle cells, and other types of cells. Further studies on the effects of microgravity on cell adhesion and the corresponding physiological behaviors may help increase the safety and improve the health of astronauts in space.
Highlights
Microgravity is a state in which the gravitational force acting in any single direction is negligible
We introduce the biological functions of cell adhesion and summarize the roles of the four major classes of cellular adhesion molecules (CAMs) on cell adhesion, namely the integrins, immunoglobulin superfamily (Ig-SF) proteins, cadherins, and selectin in regulating cell adhesion
Gene profile analysis of human umbilical vein endothelial cells (HUVECs) cultured on the international space station (ISS) revealed that the expression of cell adhesion, such as vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1, and CD44 showed significant changes of expression compared with ground-based control cultures, along with the depolymerization of microtubules and actin filaments in endothelial cells, which is accompanied by the decreased secretion of pro-angiogenetic and pro-inflammatory cytokines [61,62]
Summary
Microgravity is a state in which the gravitational force acting in any single direction is negligible. The absence of gravity in space (zero gravity) can be simulated as microgravity on earth, for which many ground-based tools were developed. Researchers are investigating the effects of microgravity on the physiological state of cells and the underlying mechanisms using earth-based simulation techniques. The biological effects of weightlessness on the human body have been recognized and investigated since the earliest space flights, forming one of the most important research directions in the field of aerospace medicine. During both short- and long-term space flight, astronauts are exposed to several risk factors related to radiation and the absence of gravity. The effects of microgravity on the adhesion of endothelial cells, immune cells, cancer cells, stem cells, osteoblasts, muscle cells, and other types of cells both during spaceflight and under simulated conditions, are reviewed
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