Organ Farming

March 14, 2014

By Medical Discovery News

Imagine that a patient needs an organ, like an airway to their lungs called a trachea. A scientist harvests some of the patient’s cells and attaches them to a scaffold the proper shape and size for the tube. The cells and scaffolds are placed into a tissue reactor and – ta da! – in a week or two there is an organ ready for the surgeon to transplant into the patient. While it sounds like a chapter from “Brave New World,” this science fiction scenario is a growing reality.

Bladders and ears have been grown in the laboratory, and hearts, eyes, and kidneys and other organs are in progress. These organs are close to the natural ones they’re copying – some even have their own immune system. In April 2013, surgeons at the Children’s Hospital of Illinois implanted a bioengineered trachea into a two-year-old child. This was the first surgery of its kind in the United States and one of only six worldwide.

The patient receiving the transplant was a girl named Hannah Warren who was born without a trachea, commonly called a windpipe. Since birth, she’s had a plastic pipe inserted in her mouth that went down into her lungs, allowing her to breathe. She could not eat normally or even speak. With few options available, this type of congenital defect has always meant an early death; only a few children live past the age of six.  

Bioengineered organs could change that. The key is stem cells – cells that are at an early stage of development and through the influence of their environment can produce the many specialized cells of organs and tissues. In this case, doctors harvested the girl’s immature stem cells from the marrow inside her bones. The stem cells were taken to the lab and allowed to adhere to a plastic fiber model precisely the size (about one-half inch in diameter) and structure of the trachea she needed. Once placed in an incubator called a tissue bioreactor, the stem cells colonized the plastic and started growing. While they were growing, cells communicated with neighboring cells and worked together to produce all the cells needed for a functioning trachea. 

At the end of this process, Dr. Paolo Macchiarini implanted the trachea with promising results. Since the cells in the bioengineered trachea were based on ones from her body, her immune system didn’t recognize it as foreign and reject it, a big worry for transplant recipients. Without a plastic pipe in her mouth, Hannah was able to smile for the first time.

Unfortunately, while her trachea functioned well after the surgery, her esophagus never recovered. She underwent a second surgery to fix her esophagus and died from complications. Macchiarini said that her death was not due to the implanted trachea but her own “very fragile” tissue. He called Hannah a “pioneer” in the field of regenerative medicine and plans to conduct similar operations.

The next step for bioengineered organs is clinical trials leading to Food and Drug Administration approval. This would give more scientists and physicians the opportunity to improve organ “farming” and extend this field into a therapy that could benefit many.

For a link to this story, click here.

Sponges for Toxins

Sept. 6, 2013

By Medical Discovery News

People reach to sponges for soaking up messes, washing the dishes, and cleaning appliances. But sponges can also clean up toxins – inside the body, no less.

For years, scientists have worked to develop methods to remove toxins that destroy cells and tissues. This has been a challenge due the variety of infectious agents and poisons that produce toxins. Recently, a significant advance using nanosponges could lead to the removal of many life-threatening toxins from the bloodstream. 

Nanosponges, developed by bioengineers at the University of California-San Diego, work much like their name implies – they are designed to absorb specific substances. These nanoparticles can remove toxins produced by bacteria such as the common skin infection Staphylococcus aureus, even the antibiotic-resistant MRSA strain. These bacteria produce something called pore-forming toxins. These toxins attack cells by inserting themselves in the cell membranes, creating holes in the surface of the cell, and allowing cell contents to leak out or large amounts of external water to rush in.

In either case, this causes the cell to die. Significant or rapid loss of cells results in the damage seen during disease processes. Nanosponges work by absorbing dangerous toxins, thereby preventing them from destroying cells. To work at this level, nanosponges must be super small – 85 nanometers in diameter, about 90 times smaller than a red blood cell.  

A major issue with all drugs delivered by the bloodstream is how to prevent the immune system from removing them. Since the immune system’s job is to remove foreign agents, it is a challenge to thwart its attacks long enough for a drug to do its job. Nanosponges can overcome this with a clever technique called cloaking. Just like the enchanted invisibility cloak Harry Potter uses, nanosponges become “invisible” to the immune system by blending in with their surroundings. The nanosponge is coated with pieces of the membranes of red blood cells. This makes them look like smaller versions of red blood cells and not foreign invaders to the immune system. Cloaking is so effective that the nanosponges can still be detected in the blood 72 hours after injection, long enough to remove pore-forming toxins in the blood before the nanosponge is removed by the liver. And since they are much smaller than human cells, it’s safe to use a large dose where nanosponges outnumber red blood cells. 

The pore-forming toxins usually attack red blood cells, but when they attach to a nanosponge in disguise, they are trapped by the nanosponge’s core, which is made of a polymer called poly lactic co-glycolic acid. Each nanosponge can trap about 30 – 900 toxin molecules, depending on the type of toxin. A remarkable 90 percent of animals survived a lethal dose of MRSA toxin when they received nanosponge injections. 

MRSA is just the beginning. With this platform technology, scientists can jump into using nanosponges with other toxins as well, even bee venom. If the clinical trials in humans have similar results, nanosponges could revolutionize the way doctors treat these diseases. 

For a link to this story, click here.