Effects of Prolonged Exposure to Microgravity on Human Mesenchymal Stem Cells Function

Abstract

Microgravity in spaceflight is known to cause many physiological responses that negatively affect bone formation and maintenance in astronauts, as reported for six decades during space travels. Space experiments in LEO (low-Earth orbit) aborad the international space station or research satellites were conducted to further the knowledge on the effect of microgravity on living cells and laboratory animals. Although, they are severely limited by high costs, flight opportunities, and restricted procedures. Therefore, Earth-based weightlessness-inducing techniques such as head-tilt bedrest, hindlimb suspension, and microgravity simulation devices allowed research to be conducted extensively in space medicine, cellular and molecular studies. As precursors for osteogenic formation and regeneration, scientists studied human bone marrow mesenchymal stem cells (hBMSCs) to investigate their response to microgravity, observing changes in differentiation lineage, proliferation rate, adherence capability, and cytoskeleton. Experiments on isolated hBMSCs in vitro utilized cellular microgravity simulators such as 2D/3D clinostats, rotatory wall vessel bioreactors, or magnetic levitation systems, where cells are kept in a constant free-fall, rendering them weightless and producing similar effects of spaceflight. These experiments lasted from hours to 20 days of weightlessness, during which the authors observed cell morphology and cytoskeletal changes, measured levels of osteogenic and adipogenic differentiation markers, in addition to expression levels of specific transcription factors and signaling cascades transducers. Despite the advantages of these simulation techniques, they offered much data that future LEO studies could build upon to advance space biomedical fields. This study summarises the reported finding of microgravity experiments on human BMSCs.