It might sound unlikely, but menstrual blood could hold the secret to treating osteoarthritis, according to new research.

The study, published in Nature Scientific Reports, shows it contains tiny protein particles that can promote the growth of new cartilage, the spongy material that acts like a shock absorber for the body’s joints.

Laboratory tests on bone tissue revealed that the particles – called extracellular vesicles – triggered rapid cartilage growth. The breakthrough, by scientists at the Kaunas University of Technology in Lithuania, could mean donated menstrual blood becomes a rich source of treatment for millions affected by the condition.

Osteoarthritis (the most common form of arthritis) develops when cartilage breaks down, either as a result of injury or from age-related wear and tear.

Symptoms can be eased by losing weight to relieve the load on joints, doing strength exercises to build muscles around damaged joints, and by taking painkillers.

But an estimated one in ten people in the UK end up needing a hip replacement and one in seven a knee replacement.

Both procedures involve major surgery which carry a risk of wound infection, tissue damage and ongoing pain and stiffness in the joint.

In recent years, research has focused on ‘regenerative’ medicine – finding ways to stimulate the regrowth of missing cartilage.

‘Newer alternatives to joint replacement surgeries have been trialled which don’t require artificial joints, but rather use the body’s own cells to regrow damaged tissue,’ says Mark Wilkinson, a professor of orthopaedics at the University of Sheffield and a member of the Regenerative Medicine Discussion Group for the Osteoarthritis Research Society International.

These include cartilage cell transplantation, where healthy cartilage cells from the patient’s knee joint are removed using keyhole surgery, grown in culture, and then grafted back into the knee.

Although available in some UK centres, cartilage transplants are typically only effective for younger patients who have a single area of cartilage loss, usually due to injury rather than arthritis, he explains.

‘Other treatments have also been tried for osteoarthritis, such as stem cell therapy, where the cells can be collected in various ways, such as from body fat or bone marrow.’

Stem cells are ‘master cells’ which have the capacity to turn into virtually any type of tissue.

But collecting them from areas such as bone marrow involves invasive techniques where the soft, jelly-like marrow must be extracted with a long needle in order to harvest them.

However, using donated menstrual blood – which is easily collectable – could be a much more convenient solution.

Menstrual blood stem cells, or mesenchymal stromal cells (MSCs), were discovered more than 20 years ago by Caroline Gargett, a biologist at Monash University in Australia.

She found they were capable of rapidly differentiating into specialised cell types such as bone, cartilage and fat; some could divide into about 100 cells within a week, twice as fast as bone marrow stem cells.

Now the team in Lithuania has found that MSCs in menstrual blood release minute extracellular vesicles – proteins secreted by many types of human stem cells, which play a key role in processes such as tissue repair.

In menstrual blood, they regulate immune responses, repair the womb lining and reduce inflammation.

Researchers used menstrual blood samples from three healthy donors, as well as tissue samples taken from ten female donors with osteoarthritis.

In Petri dishes, they created biological scaffolds, with a biodegradable polyester widely used in tissue engineering, because of its flexibility and mechanical stability.

The extracellular vesicles were then placed on the scaffolds, which were sited on damaged bone samples. This provided the protein particles with the structural support for turning into cartilage.

After three days, the number of cartilage-making cells, called chondrocytes, had increased.

Levels of a type of collagen commonly found in cartilage that help provide structure for the tissue had also increased. Levels of proteoglycans – molecules also found in cartilage which help to support and lubricate the joint – were up too.

Dr Ilona Uzieliene, a researcher at Kaunas University of Technology who co-led the study, told Good Health that whereas transplanted cells might trigger tissue rejection, extracellular vesicles are much less likely to do so.

‘In our studies, they acted mainly as biological “messengers”, stimulating regeneration and reducing inflammation rather than integrating permanently into tissue,’ she said. ‘This makes them potentially safer and more broadly applicable than classical stem cell transplantation approaches.’

Crucially, they can’t divide to form unwanted tissue like cancer.

Professor Wilkinson says the treatment is thought to help patients’ remaining cartilage to heal, rather than the cells themselves developing into cartilage.

Professor Karina Wright, director of the Centre for Science and Technology in Medicine at Keele University, told Good Health: ‘This is an interesting study, but early in terms of translation into a clinical therapy. MSCs have been tested for the treatment of cartilage defects for many years with varying success. More recently, extracellular vesicles have shown some promise.’