Stem cell treatment left woman with bone growing around one eye

It sounds like a nightmare. A California woman complains to her doctor about pain in one of her eyes. She leaves his office six-and-a-half hours later after surgery to remove small chunks of bone growing in her eyelid.

In a recent report in Scientific American, the doctor described how the woman "could not open her right eye without considerable pain and that every time she forced it open, she heard a strange click - a sharp sound, like a tiny castanet snapping shut."

As it turned out, the woman had received a new-fangled "stem cell treatment", whereby her own mesenchymal stem cells were extracted by liposuction from her abdomen and injected into her face.

Her cosmetic surgeons in Beverly Hills had told her new tissue would replace the old and that the therapy would prompt a release of chemicals that would reverse the signs of ageing.

We do not know if her skin improved but she did end up with bits of bone growing around one eye.

This is the reason why: mesenchymal stem cells are "multipotent", which means they can grow into different types of cells, including fat, cartilage and bone.

Such stem cells have been used in clinical treatments for conditions including cartilage defects and neurodegenerative disorders.

Adipose tissue, including abdominal fat, is a particularly rich source of mesenchymal stem cells, containing 500 times more stem cells per gram of fat than per gram of bone marrow. Autologous fat transfer - when a patient's fat cells are harvested to be implanted somewhere else - has been used successfully to treat facial lipodystrophy, a condition in which fat is lost from the face region. For this reason, autologous fat transfer is used for facial sculpturing in cosmetic surgery.

But the woman's stem cells were doing more than what she had paid for. The California woman reportedly paid around US$20,000 for the procedure. Her doctors apparently decided to finish the surgery by smoothing out her wrinkles with dermal filler, commonly used in minor cosmetic procedures. Unfortunately, the doctors missed the fact that the principal component of the dermal filler was calcium hydroxylapatite, a naturally-occurring mineral found in teeth and bone that can prompt mesenchymal stem cells to turn into bone.

Calcium hydroxylapatite is biodegradable, naturally broken down by the body. For this reason, it is widely used as filler and in medical implants.

In dermal fillers, calcium hydroxylapatite may promote new tissue formation, depending on the surrounding environment. When injected into the dermal layer of the skin, it supports the formation of new collagen, though usually without forming bones.

However, the hapless woman's surgeons had injected her face with mesenchymal stem cells that do not normally reside in the face. I suppose the doctors were not exaggerating when they said her stem cells would replace old tissue. Still, she probably was not counting on having unwanted bones formed in her face.

When the stem cells encountered the calcium hydroxylapatite, they turned into bone tissue, resulting in bits of bone growing around the woman's eye. These bone fragments were grinding against each other every time she opened and closed her eyes, making a clicking sound.

Some might declare that those vain enough to have stem cells injected for cosmetic purposes deserve what they get. However, this example is a sobering reminder that while stem cells hold enormous potential for regenerative medicine, scientists are only just beginning to understand how they function.

Living cells are constantly reacting to their surrounding environment. When taken and put in a new place, they may act in unpredictable ways.

Scientists and clinicians are working to collect preclinical data to assess the safety of stem cell therapies. However, there are doctors eager to make a quick buck by offering untested stem-cell treatment to unsuspecting customers.

Fortunately, the bones around the California woman's eye were removed in an operation, and the woman was said to have fully recovered.

Nonetheless, it is likely that some abdominal fat stem cells linger in her face, and it is possible that if stimulated, they could develop into bone or cartilage at a later date.

David Tan is a research scientist at the A*STAR Institute of Medical Biology, Singapore. He holds a PhD in stem cell biology from the University of Cambridge.