Breakthrough isolating embryo-quality stem cells from blood

Scientists have developed the first reliable way to extract stem cells from blood without adding contaminating markers

A major breakthrough in stem cell research – a new tool that could allow scientists to harvest stem cells ethically – will be announced at the Institute of Physics’ conference Physics 2005 in Warwick later today (Tuesday 12th April).

Professor Josef Käs and Dr Jochen Guck from the University of Leipzig have developed a procedure that can extract and isolate embryo-quality stem cells from adult blood for the first time. This new technique could unlock the stem cell revolution and stimulate a boom in medical research using stem cells.

Stem cells are cells which have not yet differentiated into specialised tissues such as skin, brain or muscle. They promise a new class of regenerative medicine, which could repair apparently permanent damage such as heart disease or Parkinson’s. The cells are currently taken from aborted human foetuses, an issue which has led to controversy and opposition in many parts of the world. Any alternative source, such as voluntary adult donations, could spark a boom in new cures.

Scientists have known for some time that stem cells exist in adult human blood and certain other tissues. However the only reliable way to separate them involved marking the cells with a chemical dye, rendering them useless for medical purposes. Professor Käs’ technique for the first time uses a physical characteristic of each cell – its stretchiness or elasticity – instead of its biological make-up, to decide whether or not it’s a stem cell. Stem cells don’t need a rigid “cytoskeleton” to hold them in shape, which makes them stretchier than normal cells.

Käs and Guck’s machine uses a powerful beam of infrared laser light to stretch and measure cells one by one. His optical stretcher differs from an existing tool known as optical tweezers in which the light is focused to a sharp point to grab hold of a cell. In contrast, the optical stretcher uses un-focused light. This allows laser beams strong enough to detect stretching to be used without killing the cell.

According to Dr Michael Watts, an expert in haematology and stem cells at University College London, there are just 10,000 primitive cells in the average adult’s bloodstream. Of those, only 500 might have the potential to replace embryonic stem cells. Stem cell research requires millions of these cells.

Bone marrow donors are routinely treated with a drug known as G-CSF which “mobilises” stem cells from the bone marrow into the blood. After G-CSF treatment the donor’s blood is passed through a centrifuge and back into their body, akin to a kidney dialysis machine, harvesting two or three hundred million primitive cells in the process.

Various properties of these primitive cells have been used to try and isolate the 5% or so with the highest stem cell potential, but no single technology has proved completely successful for human stem cells. This is where the optical stretcher could come to the rescue, picking those cells one by one according to the strength of their cytoskeletons. Watts explains that such an advance could have far-reaching consequences for medical treatments. “We could add significantly to our knowledge of stem cell biology toward developing cellular therapies,” he says.

The optical stretcher can already test 3,600 cells per minute. This is not yet fast enough for industrial separation of millions of high grade stem cells, but it promises a realistic alternative to embryo use if it can be scaled up. Meanwhile, it is already being used to isolate low-grade stem cells which can develop into skin. In collaboration with medical professionals in Leipzig, elderly patients are being treated for persistent non-healing wounds. Low-grade stem cells isolated from the patient’s own blood are applied to the wound to kick-start the healing process.