Inspiration And Expert Advice: Expert Columns
Studies Say Pig Islets Good Source of Insulin
By Daniel Trecroci
We have all heard that saying “dog is a man’s best friend.” If you have type 1 diabetes and you are looking for an islet-cell transplantation procedure, though, the pig might trump the pooch in the best-pal department.
Studies have confirmed that you can transplant islets into a person with type 1 diabetes and those transplanted islet cells — with the help of anti-rejections medications — can produce insulin. With a shortage of human-donor tissue, however, making islet transplantation a wide-scale procedure has its shortcomings.
But What if You Could Use Islets from a Non-human Source?
Enter xenotransplantation — or, the transplantation of living cells, tissues or organs from one species to another. Experts say that xenotransplantation could essentially provide an unlimited supply of islet cells (“islets”) for transplantation. According to MicroIslet Inc., — a biotechnology company engaged in the research, development and commercialization of patented technologies in the field of transplantation therapy for patients with diabetes — pig insulin differs from human insulin by a single amino acid, making their islets ideal for transplantation into a human.
A Controversial Topic, Despite its Promise
The concept of transplanting pig islets into humans has been met with resistance in the past because of rejection issues as well as concerns over something known as Porcine Endogenous Retrovirus (PERV) infection. In the 1990s, British virologist Robin A. Weiss demonstrated that PERV can infect human cells in a test tube. As a result, Britain and a few other countries declared a moratorium on xenotransplants.
In a January 23, 2008 post on the blog Diabetes Information http://aboutdiabetes4u.blogspot.com, Wayne Channon, director of Cells4Life Ltd, which specializes in umbilical cord blood collection, wrote that PERV transmission has been a focus of several conflicting studies.
“Some studies report no transmission following transplantation of living [pig] tissue into human patients and no evidence of transmission when [pig] islets are co-incubated with permissive human stem cells in vitro. Contrary to these reports, [PERV] transmission was frequently observed between cultured [PERV]-producing [pig] cells or specific pathogen-free [pig] islets and human or mouse cells in vivo.”
Pig Islets Would be Microencapsulated for Protection
MicroIslet says that its proprietary xenotransplantation technology may overcome many of the obstacles that have plagued islet transplantation. To protect transplanted cells from rejection by the patient’s immune system, MicroIslet has developed a unique method of microencapsulation (known as MicroIslet-P), which coats pig islets with a “highly biocompatible biopolymer derived from seaweed.”
According to MicroIslet, “This covering around the islets effectively blocks a patient’s immune system from recognizing the transplanted material as foreign.”
“Safety wise, we have seen no adverse events associated with MicroIslet-P to date, in any animal model,” says Keith B. Hoffman, Ph.D., a MicroIslet spokesperson.
MicroIslet-P has been tested in hundreds of rodents and is currently completing a trial with 19 monkeys.
“… all monkeys tested to date, post-implant, have demonstrated efficacy as evidenced by decreases in insulin requirements needed to maintain their blood glucose levels at a healthy concentration,” says Hoffman.
As far as PERV is concerned, Hoffman says that in studies conducted by MicoIslet — as well as many other groups around the world — there has been no evidence of PERV infection in any test animal to date.
“The patients transplanted with MicroIslet-P will be monitored for possible PERV transmission,” says Hoffman
Hoffman adds that MicroIslet’s pigs are raised in a barrier facility and are tested for viruses and other potential diseases monthly. Their diet is a specially prepared vegetarian diet, and their water and air are purified on site.
How the Procedure is Done
According to Hoffman, when human clinical trials begin, participants will receive the pig islets through a minimally invasive method.
“The islet cell transplant infusion will be conducted in an outpatient setting in a procedures room in the hospital,” says Hoffman. “The microencapsulated islet cells will be transplanted into the [abdomen] cavity using a guided catheter. The patient will be closely monitored in the hospital for a period of 48 hours and released thereafter.
Participants will be monitored for a period of six months for blood glucose levels and daily insulin requirement. They will also be required to take anti-rejection medications.
Hoffman encourages xenotransplantation detractors to “look at the data again,” saying that “the proof of concept for xenotransplantation with islet cells is now well established… If the FDA approves MicroIslet’s [investigational new drug application] submission later this year, the detractors will have a much harder time arguing that a safe, effective, path forward exists. We are in total alignment with the FDA to ensure that xenotransplantation treatments can be safe and useful for patients.”
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