And the beat goes on: Dead rat hearts get second chance

Minnesota researchers have found a way to grow new functioning heart tissue from tissue taken off of dead rats. The procedure called whole organ decellularization could some day allow scientists to grow specialized organs so they can be transplanted into human bodies matched for just the right organs.

U.S. biologist Doris Taylor, who is the director of the University of Minnesota Center for Cardiovascular Repair, at the UM Stem Cell Institute, and her team of researchers used a biotechnology process called decellularization.

In the process they washed away existing heart cells with detergents and other chemicals from the muscle and blood vessels within the hearts of dead rats. What was left was a basic collagen structure—a scaffolding of tubes that once was the blood vessels within the organ. Taylor’s team injected the collagen structure with immature heart cells from newly born rats. The tissue structure was then fed a solution of nutrients and left to grow on its own. In about four days the heart tissue began to contract. A pacemaker was used to stabilize the contractions of the heart, along with the introduction of fluids and pressure. Within eight days, the new heart was pumping on its own.

Taylor stated, within a Reuters article, "The hope ultimately—although we've got a ways to go—is that we could take a scaffold from a pig or a cadaver and then take stem or progenitor cells from your body and actually grow a self-derived organ.” She also stated that other organs, such as kidneys, livers, lungs, muscles, and pancreases, could be potentially generated in the same way, by using the basic structure from organs of human cadavers and the stem cells from the recipients themselves. In this way, the new heart would be very similar to the cells of its new owner, with less likelihood of being rejected after it is transplanted.

Taylor noted that such a regenerative method could be used on a human within ten years. According to an article on Bloomberg.com, Taylor stated, “The heart is just a beautiful, elegant organ, and it would be very difficult to recreate it. We started thinking, `Wouldn't it be cool if we could just take the cells out and put new cells in?’.

The research of Taylor and her colleagues has been written up in the January 13, 2008 issue of the journal Nature Medicine. The title of their article is “Perfusion-decellularized matrix: using nature's platform to engineer a bioartificial heart.”

Her team consists of Harald C. Ott, Thomas S Matthiesen, Saik-Kia Goh, Lauren D. Black, Stefan M. Kren, and Theoden I. Netoff.

The abstract to the paper states: “About 3,000 individuals in the United States are awaiting a donor heart; worldwide, 22 million individuals are living with heart failure. A bioartificial heart is a theoretical alternative to transplantation or mechanical left ventricular support. Generating a bioartificial heart requires engineering of cardiac architecture, appropriate cellular constituents and pump function.”

It continues: “We decellularized hearts by coronary perfusion with detergents, preserved the underlying extracellular matrix, and produced an acellular, perfusable vascular architecture, competent acellular valves and intact chamber geometry. To mimic cardiac cell composition, we reseeded these constructs with cardiac or endothelial cells. To establish function, we maintained eight constructs for up to 28 d by coronary perfusion in a bioreactor that simulated cardiac physiology. By day 4, we observed macroscopic contractions. By day 8, under physiological load and electrical stimulation, constructs could generate pump function (equivalent to about 2% of adult or 25% of 16-week fetal heart function) in a modified working heart preparation."