The ovary, which was created in a laboratory from cells donated by hospital patients, can mimic a real ovary by growing over the eggs and allowing them to mature.
The researchers said the breakthrough could allow eggs to be taken from women before they were exposed to chemotherapy or radiation and then developed in the artificial structure.
Scientists hope it could also help answer questions about how ovaries work and enable experiments on what causes problems for egg maturation and health.
The researchers, from Brown University and Woman & Infants Hospital in America, grew the donor cells into honeycomb shapes before placing human egg cells in the holes.
Within days the cells had enveloped the immature eggs and they were able to grow to full maturity, according to the study in the Journal of Assisted Reproduction and Genetics.
Sandra Carson, professor of obstetrics and gynaecology at Brown University, wrote: “An ovary is composed of three main cell types, and this is the first time that anyone has created a 3-D tissue structure with triple cell line. This is really very, very new and is the first success in using 3-D tissue engineering principles.”
Neil McClure, professor of Obstetrics and Gynaecology at Queen’s University, Belfast, said: “This certainly has the potential to provide a very good way of maturing very immature eggs in the lab to the point where they can be used for assisted reproduction.
“There are lots of studies that need to be done but it is a huge step forward and a very novel technique that has the potential to give hope to young women who are going to be undergoing treatment which will prevent them having children naturally.”
Professor Richard Fleming, director of the GCRM fertility unit in Glasgow, said the development could have “great practical implications” on fertility treatment by maturing eggs more reliably.
He said: “It is a significant step along a long pathway but really quite an important one.
“If you try to mature eggs in a Petri dish the structure tends to collapse rather than sticking to itself. This is trying to improve the proportion of the immature eggs that get through to the mature stage.”
But other experts said the new development did not yet represent a ‘real’ artificial ovary” because it did not contain primordial follicles, which develop eggs in real ovaries.
Professor Bill Ledger, a fertility expert from Sheffield University, said: “We have no idea why a primordial follicle will rest for 30 years or more then decide to begin to develop and eventually release its egg. If we did, then we could try to lengthen a woman’s fertile lifespan or restore fertility to women after treatment with chemotherapy.
“The artificial structure does not contain primordial follicles, nor have they shown that it can regulate the ‘awakening’ of primordial follicles in an orderly manner, as in the normal ovary, so I don’t think its quite accurate to label it as an artificial ovary.”