During menopause a woman’s ovaries stop working—leading to hot flashes, sleep problems, weight gain, and worse, bone deterioration.

Now scientists are exploring whether transplanting lab-made ovaries might stop those symptoms. In one of the first efforts to explore the potential of such a technique, researchers say they used tissue engineering to construct artificial rat ovaries able to supply female hormones like estrogen and progesterone.

The work, carried out at Wake Forest Baptist Medical Center, suggests a potential alternative to the synthetic hormones millions of women take after reaching middle age. A paper describing the findings was published Tuesday in Nature Communications.

When tested in rats, the pieces of tissue, known as organoids, were better than traditional hormone replacement drugs at improving bone health and preventing weight gain. The treatment was also as good as hormone drugs at maintaining healthy tissue in the uterus.

Clinical trials of artificial ovaries are not likely to happen soon. For one thing, it is uncertain where the cells needed to build the organoids would come from. Emmanuel Opara, a professor at Wake Forest who led the research, says younger women might need to donate the tissue.

Women going through menopause, as well as those who have undergone cancer treatment or had their ovaries removed for medical purposes, lose the ability to produce important hormones, including estrogen and progesterone. Lower levels of these hormones can affect a number of different body functions.

To counteract unpleasant symptoms, many women turn to combinations of hormone replacement medications—synthetic estrogen and progestin. But hormone replacement carries an increased risk of heart disease and breast cancer, so it’s not recommended for long-term use. Opara thinks artificial ovaries could be safer and more effective.

To engineer the organoids, Opara and his colleagues combined two cell types—granulosa and theca cells. They collected samples of these cells from female rats that had their ovaries removed and grew them in the lab so they eventually formed three-dimensional tissue.

Within a week of implantation, the artificial ovaries started secreting estrogen, progesterone, and two other natural hormones not found in current hormone replacement drugs.

Cynthia Stuenkel, a clinical professor of medicine at the University of California, San Diego, and a spokeswoman for the Endocrine Society, says the report is “fascinating” but sees a downside if such treatments really reverse menopause. She wonders if the hormones would be enough to bring back a woman’s period and the symptoms that often come along with it.