by George Taniwaki

Current donor kidney preservation technology

Kidney transplant surgery has a rather unusual characteristic. It is normally performed on an emergency basis, but it is not a critical life-saving procedure. Let me explain.

Once a person is diagnosed with end-stage renal disease (ESRD), they will require immediate renal replacement therapy or else they will die. However, that doesn’t mean they need an immediate transplant. That’s because dialysis technology is now quite reliable and dialysis equipment is widely available in all major cities. In fact, a patient can live several years on dialysis. Thus, kidney transplant surgery is usually performed as an elective procedure rather than a critical procedure.

Most kidneys come from deceased donors and the quality of the organ is dependent on the length of time it lacks blood circulation. There are two stages for measuring this time. The first is the time the kidney is cut off from circulation while still inside the body of the deceased donor (known as warm ischemia time). The seconds is the time the kidney is kept cool in a preservative solution (known as cold ischemia time).

Current preservation solutions are not very effective and the number of cells in the organ that die while the organ is not getting blood flow can be quite high. If the ischemia time is too long, the organ function is reduced which worsens patient outcomes (Arch. Surgery Sep 2000). And as the transport time increases, the more likely it is that the receiving surgeon will reject the organ and it must be discarded (Amer. J. Transpl. May 2007). Thus, there is often a large rush and expense to fly organs to the receiving hospitals. Meanwhile the receiving hospitals need to contact the recipients and quickly get them to the hospitals and prepared for surgery. (Note that this urgency only applies to deceased donor surgery. Live donor surgery like mine can be scheduled days or weeks in advance.)

A better solution may be the solution

An article in today’s Tech. Rev. points to an interesting collaboration between Hemant Thatte, a cardiothoracic researcher at Harvard’s medical school, with three students from Harvard’s business school. The students became aware of Mr. Thatte’s experimental preservative solution called Somah (Circulation Nov 2009) that can extend the time organs can be preserved prior to transplantation, or conversely, improve the quality of the organs for a given ischemia time. In a study using pig hearts, after 4 hours of storage at 4°C, hearts preserved with Somah had much better cell structure and function than those preserved using the standard solution.

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Heart perfusion test. Photo from Harvard

The students decided to write a business plan for this preservative solution. They formed a company called Hibergenica and are seeking $5 million in venture capital financing to complete medical studies and file for FDA approval. Their collaboration was featured at the Univ. Res. Entrepreneurship Symp. 2010 held recently in Cambridge.

The business plan projects the market for preservative solution to grow from $30 million today to $200 million if Somah can be sold for five times the price of the current solution and some market growth occurs because more organs that would normally be discarded are instead preserved and shipped to a distant transplant center.

Warm perfusion

The Tech. Rev. article points out that there is another competitor worth watching. TransMedics in nearby Andover has developed the first portable warm blood perfusion system. By pumping oxygenated blood and a preservative solution through the harvested organ, it avoids the damage caused by ischemia. In fact, the company claims that by using their device, an organ can be resuscitated and its function improved while waiting for transplantation.

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 Warm perfusion test. Photo from TransMedics

[Update: Clinical trials have started for the TransMedics device, see this Nov 2010 blog post.]

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