Human heart muscle cells show changes in the way they operate in space, although they behave normally within 10 days after returning to the Earth, according to a study. The research, published in the journal Stem Cell Reports, examined the cell-level cardiac function and gene expression in human heart cells cultured aboard the International Space Station (ISS) for 5.5 weeks, India Today reports.

Exposure to microgravity altered the expression of thousands of genes, but largely normal patterns of gene expression reappeared within 10 days after returning to the Earth, the researchers said.

"Our study is novel because it is the first to use human induced pluripotent stem cells to study the effects of spaceflight on human heart function," said Joseph C Wu of Stanford University School of Medicine in the US.

"Microgravity is an environment that is not very well understood, in terms of its overall effect on the human body, and studies like this could help shed light on how the cells of the body behave in space, especially as the world embarks on more and longer space missions such as going to the Moon and Mars," Wu said.

Past studies have shown that spaceflight induces physiological changes in cardiac function, including reduced heart rate, lowered arterial pressure, and increased cardiac output.

However, to date, most cardiovascular microgravity physiology studies have been conducted either in non-human models or at tissue, organ, or systemic levels.

Relatively little is known about the role of microgravity in influencing human cardiac function at the cellular level.