Scientists have succeeded in growing a man-made womb lining in the lab -- or organoids -- paving the way for new insights into the early stages of pregnancy and menstrual problems such as endometriosis.

The organoids were cultured in a dish from cells taken using tissue from the endometrium -- the mucosal lining of the uterus -- reproducing the endometrial gene patterns and maintaining the organoids for several months. The findings, detailed in the journal Nature Cell Biology, may help understand the early stages of pregnancy and conditions such as endometriosis -- a painful condition that affects 176 million women worldwide. 

The organoids also respond to female sex hormones and early pregnancy signals, secreting what are collectively known as 'uterine milk' proteins that nourish the embryo during the first months of pregnancy, the researchers said. "These organoids provide a major step forward in investigating the changes that occur during the menstrual cycle and events during early pregnancy when the placenta is established," said lead author Margherita Turco from the University of Cambridge. 

There's increasing evidence that complications of pregnancy, such as restricted growth of the foetus, stillbirth and preeclampsia -- which appear later in pregnancy -- have their origins around the time of implantation when the placenta begins to develop.  Research in animal species such as mice and sheep has shown that factors secreted by the endometrial glands are critical for enabling a developing fertilised egg (known as the 'conceptus') to implant into the wall of the uterus. 

The conceptus sends signals to the endometrial glands that then stimulate the development of the placenta.  In this way, the conceptus is able to stimulate its own development through a 'dialogue' with the mother; if it fails, the result is the loss of the pregnancy or severe growth restriction of the foetus, the researchers explained.

The study will also help researchers to model and understand diseases of the endometrium, including cancer of the uterus and endometriosis.