Stem cells coaxed into regenerating bone while leaving tumors out

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The UC San Diego team added adenosine to their stem cell culture medium (pictured) to create osteoblasts(Credit: UC San Diego Jacobs Schools of Engineering)

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A team of scientists at the University of California, San Diego (UC San Diego) has found a simple but effective way of encouraging stem cells to regenerate bone tissue. With successful animal tests already in the bag, the findings could have a big impact on the treatment of bone defects, and for healing traumatic bone injuries.

Pluripotent stem cells are extremely versatile, with the capability of becoming any type of cell found in the body, a process known as differentiation. In 2012, a Johns Hopkins study saw the development of a technique to regress blood cells into pluripotent stem cells, and over the years we've seen them used to create functional intestinal tissue, grow human retinas, and much more.

Despite past successes in utilizing the versatile stem cells, coaxing them to develop into a particular type of cell is anything but simple. The UC San Diego team describes the process as being akin to following a very complex recipe, with a long list of ingredients and a complex set of steps. That complexity can make using pluripotent stem cells time consuming and expensive.

There's also a risk of tissue created from pluripotent stem cells developing teratomas once transplanted. These tumors, which contain various different types of organ tissue, can occur when errors slip into the cell development process, causing uncontrollable differentiation.

The researchers were able to guide the stem cells into becoming osteoblasts, seen here in an artificially colored image(Credit: Varghese Lab, UC San Diego)

In contrast to the complexities usually involved in pluripotent stem cell differentiation, the UC San Diego team was able to create functional osteoblasts – bone-building cells – by adding a single molecule that occurs naturally in the body, known as adenosine, to their growth medium.

The research builds on the team's previous work, where they added calcium phosphate to stem cells, producing a metabolic molecule, which then broke down into adenosine, eventually signaling the stem cells to develop into osteoblasts. The new work was essentially an attempt to cut out as many steps of the process as possible, making it much quicker and simpler.

The researchers tested out the cells in laboratory mice with bone defects, where they found that the osteoblasts successfully formed new bone tissue without any teratoma formation occurring.

As to exactly how the adenosine promotes bone regeneration, there's still some sleuthing to be done. The team currently believes that the receptor on the stem cells' surface which the adenosine binds to, known as the A2bR receptor, is central to the process. Right now though, the exact workings of the mechanism are still something of a mystery.

Full details of the research are published online in the journal Science Advances.

Source: UC San Diego

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