Surgeons freeze organoid units and regenerate TESI for short bowel syndrome

Surgeons at Children's Hospital Los Angeles have conducted a study that could put regenerative tissue treatment for short bowel syndrome one step closer to the bedside. The researchers were able to successfully isolate and store organoid units and later generate tissue-engineered small intestine (TESI) in a mouse model. The groundbreaking results were presented at the 2011 Annual Clinical Congress of the American College of Surgeons.

During the study, surgeons extracted organoid units from the small intestines of young mice. Organoid units are multicellular clusters that contain epithelium, which lines the small intestine, and mesenchyme, which helps to form the connective tissue of the small intestine. After freezing the organoid units for eight weeks at minus 80 degrees Celsius, the researchers then implanted the organoid units into adult mice. The study was led by Allison L. Speer, MD, pediatric surgery research fellow at Children's Hospital Los Angeles working in the laboratory of Tracy C. Grikscheit, MD, FACS.

One week after implantation into the mice, the surgeons were able to see, through immunofluorescence staining, that the regenerated intestine had developed smooth muscle cells and intestinal subepithelial myofibroblasts, which promote the small intestine's development and cell proliferation.

Two weeks after implantation, the researchers observed that enterocytes had developed, which aid nutrient absorption, along with Paneth cells, which are vital to the formation of the epithelium and protection from bacteria.

Some day, the ability to grow TESI from a child's own intestinal cells and then connect the regenerated intestine to the native intestine will be key to reducing the morbidity that often accompanies organ transplant in humans. "Typically, if we were to implant cells from one child into another, the potential for rejection is high," explained Dr. Speer, who is also a surgical resident at the University of Southern California. "The child would require immunosuppressant medications that not only cause side effects, but can also strongly pre-dispose the patient to infections."

However, if the patient's own cells are used, the likelihood of an immune response is reduced. Previous research from the laboratory of Dr. Grikscheit, where Dr. Speer conducted the research, has shown that TESI can be generated from autologous cells in a pre-clinical Yorkshire swine model.

This study, marks the first time that surgeons were able to freeze organoid units, implant them at a later date, and regenerate TESI. This novel long-term storage method will ensure that autologous intestinal cells are available to the most vulnerable patients. "If a child is very sick, we would not be able to implant right away," Dr. Speer explained. "Regeneration of TESI in a child who is critically ill would be extremely difficult. We want to be able to freeze the intestinal cells and implant them later, after the child has recovered."

Short bowel syndrome most commonly occurs in premature newborns after half or more of their small intestine is surgically removed. Short bowel syndrome may result from surgery that is performed to treat birth defects, intestinal injuries, or conditions like necrotizing enterocolitis.

Since the small intestine is where most food and water absorption occurs, people with short bowel syndrome suffer from severe nutrient deficiencies. This leaves patients almost permanently hospitalized and dependent on nutritional support, which can cost up to $100,000 per year. "The number of infants with the condition is increasing as medical advances allow more premature newborns to live longer," Dr. Grikscheit, attending surgeon at Children's Hospital Los Angeles, explained.

"Our goal is to grow larger pieces of intestine for smaller babies faster," Dr. Grikscheit said. "We want to push our system to grow bigger, better intestine for children with short bowel syndrome."

The ability to enhance the small intestine regeneration will help with this goal. "We want to understand how the tissue is forming and what genes are important for it to grow from a cluster of cells into a full-thickness, functional intestine," Dr. Speer said. "If we can provide stimulatory growth factors, we may be able to push the intestinal cells to grow faster and larger. This will be important when we eventually transition this technique to humans."

Both Drs. Speer and Grikscheit said they hope to reproduce these results in more animal models to refine small intestine regeneration and storage. Eventually, they hope to begin testing their techniques with human intestinal cells, ultimately leading to treatment for short bowel syndrome patients. "We get an e-mail a week from families asking us to help their babies, we know there is a need." Dr. Grikscheit said. "We have a lab plan to be in children in 10 years. I truly believe it will happen within the decade."