Saturday, 15 December 2012

ACT announces human stem cell clinical trial

Advanced Cell Technology, a biotechnology company from Massachusetts, has started the process to receive regulatory approval of what they claim to be the first human clinical trial involving stem cells. They will be using induced pluripotent stem cells to create platelets, the cells that form clots and stop bleeding.

Many people could benefit from this clinical trial, as repeated platelet transfusions are employed for many different conditions including various types of leukaemia and anaemia. Without platelet transfusions, most of these patients would eventually die. However, in many cases the patient starts to develop antibodies that attack the donated platelets, making each transfusion less and less efficient.

The upcoming stem cell clinical trial from ACT aims to solve this exact problem. If everything goes by the book the body won't attack the platelets as foreign cells, as they will share the same genetic code. Alan Michelson, who will be one of the leading researchers said:

"This would really be a dramatic advance in medicine, but it remains to be seen if this would be successful" 

For the moment, the company is thinking in small numbers. At first they want 16 people to participate in the clinical trial. Eight of them will receive platelets made from induced pluripotent stem cells and 8 will receive standard platelet transfusions containing donated cells (control group). By using induced pluripotent stem cells, the company also avoids all the ethical issues associated with embryonic stem cells, as this type of stem cell originates from the patient's own body and not from embryos. Robert Lanza, the company's chief scientific officer, said:

"It doesn't require any embryos. It doesn't require eggs. It doesn't require any destruction of embryos"

She also said that the company has the means to produce enough platelets for the clinical trial, however it will "take time to scale up for widespread use".

picture of two platelets surrounded by blood cells
Image from a microscope showing two platelets (purple) surrounded by red blood cells

During the trial, all stem cell derived platelets will be marked with a special chemical that will allow researchers to better examine them. Blood will be drawn and analysed in a common basis, in order to check the function of the new platelets.  If the trial yields positive results, "the potential impact would be great," said stem cell researcher Cynthia Dunbar.

According to officials, ACT is ready to take action and start the stem cell trials even by the end of 2013. All it needs, is approval.

When "playing" with stem cells, researchers have to face many challenges. One of them is preventing genetic abnormalities that may lead to cancer. Platelets have the advantage of not carrying DNA molecules, thus  their capacity to become cancerous cells is limited, if any. According to Hames Thomson, one of the pioneers in the field of induced pluripotent stem cells, there is still a small chance that stray cells with DNA could contaminate a batch of platelets. He explains:

"You have to manipulate the cells quite a bit, so I think you'll have to overcome the safety concerns of the FDA and other regulatory bodies," 

Lanza stated that "multiple measures" will be taken to prevent any contamination risks, one of them being that the platelets will be first irradiated.

Platelets (also known as thrombocytes), are small, irregularly shaped cells that don't have a nucleus. They are 2–3 ┬Ám in diameter and circulate in the blood of mammals. They have a significant role in homoeostasis, leading to the formation of blood clots. If their number is too low, excessive bleeding may occur whereas when too high, blood clots may form (thrombosis), resulting in events like a stroke, myocardial infarction, pulmonary embolism etc.

Various conditions may lead to a constant low number of platelets, requiring platelet transfusions in a regular basis. Some examples are multiple myeloma, aplastic anaemia, AIDS, hypersplenism, ITP and sepsis.

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