NEW DELHI: Pigs could soon become the new source for organs and cells for humans.
With shortage of organs and cells from dead people restricting transplantation, scientists say organs from genetically-modified pigs equipped with genes to protect them from the human immune response is all set to power the next medical revolution.
Pig heart valves and tissues for orthopedic (ligament reconstruction) and general surgical (small intestinal submucosa for bladder repair) procedures are being used in patients even in India. However, these are tissues from which pig cells have been removed. Post-transplantation, the tissues are repopulated with human recipient cells.
Although these procedures represent a form of xenotransplantation or cross-species transplantation, the future, doctors say, is nigh when viable pig organs and cells will continue to function after clinical transplantation.
Dr Soma Guha Takurtha, cardiac surgeon at Frontier Lifeline Hospital in Chennai, who has been using pig tissues on humans, said, "We are often called vertical pigs. This is because the size of pig organs - heart, liver, pancreas and kidneys - match well, making them anatomically similar. Transgenic pigs are the future source of organs for humans."
She added, "However, the tissues on use are devoid of pig cells and are repopulated with human cells. Once we know how to mute a carbohydrate antigen that causes rejection of pig organs in humans, organs can be transplanted as they are."
A research published in "The Lancet" on Friday, Dr Burcin Ekser and Dr David Cooper from Thomas Starzl Transplantation Institute of the University of Pittsburgh, says results of pre-clinical transplantation of organs from genetically-modified pigs into non-human primates - islets, neuronal cells, hepatocytes or corneas are encouraging with survival times greater than one year in all cases.
Risk of transfer of an infectious microorganism to the recipient is also small, they said.
The scientists said many disorders could be treated with clinical xenotransplantation. Islets could also be transplanted to treat diabetes, neuronal cells for patients with neurodegenerative diseases such as Parkinson's, hepatocytes for hepatic failure, corneas and neuroretinal cells for patients with various forms of blindness and even red blood cells for transfusion.
"With successful storage methods, pig corneas, islets and cells (including red blood cells) could be successfully transported from a developed country where genetically engineered animals would be bred and housed to a developing country where need for the biological product is great," they said in the Lancet.
They added, "The need for a new source of organs and cells for clinical transplantation has been clear for decades. Tissues such as pancreatic islets and neuronal cells from deceased human donors have never been sufficient. Xenotransplantation (pigs to people) could resolve this issue."
There is an increasing availability of pigs that have undergone genetic modifications to protect tissues to be transplanted from human immune response. However, significant barriers need to be overcome before pig organ xenotransplantation can become a clinical therapy, "although clinical trials of pig islet, neuronal-cell and corneal xenotransplantation are imminent. A government regulated clinical trial of pig islet transplantation is taking place in New Zealand," the study said.
A diabetic monkey has survived for more than a year supported only by pig islets, suggesting that the technique will be physiologically successful. A potential problem arises for Type 1 diabetes patients, whose autoimmune response could destroy the new grafts over time (just as the patients' own pancreatic islet cells were destroyed).
However, regular re-transplantation could occur if this happened. Researchers are also studying 'encapsulated' islets. These islets are shielded from the body's immune system in a capsule, so that immunosuppression is not necessary.
Early trials have shown that transplantation of pig neuronal cells into non-human primates with a model of Parkinson's disease significantly improves locomotor function.
With shortage of organs and cells from dead people restricting transplantation, scientists say organs from genetically-modified pigs equipped with genes to protect them from the human immune response is all set to power the next medical revolution.
Pig heart valves and tissues for orthopedic (ligament reconstruction) and general surgical (small intestinal submucosa for bladder repair) procedures are being used in patients even in India. However, these are tissues from which pig cells have been removed. Post-transplantation, the tissues are repopulated with human recipient cells.
Although these procedures represent a form of xenotransplantation or cross-species transplantation, the future, doctors say, is nigh when viable pig organs and cells will continue to function after clinical transplantation.
Dr Soma Guha Takurtha, cardiac surgeon at Frontier Lifeline Hospital in Chennai, who has been using pig tissues on humans, said, "We are often called vertical pigs. This is because the size of pig organs - heart, liver, pancreas and kidneys - match well, making them anatomically similar. Transgenic pigs are the future source of organs for humans."
She added, "However, the tissues on use are devoid of pig cells and are repopulated with human cells. Once we know how to mute a carbohydrate antigen that causes rejection of pig organs in humans, organs can be transplanted as they are."
A research published in "The Lancet" on Friday, Dr Burcin Ekser and Dr David Cooper from Thomas Starzl Transplantation Institute of the University of Pittsburgh, says results of pre-clinical transplantation of organs from genetically-modified pigs into non-human primates - islets, neuronal cells, hepatocytes or corneas are encouraging with survival times greater than one year in all cases.
Risk of transfer of an infectious microorganism to the recipient is also small, they said.
The scientists said many disorders could be treated with clinical xenotransplantation. Islets could also be transplanted to treat diabetes, neuronal cells for patients with neurodegenerative diseases such as Parkinson's, hepatocytes for hepatic failure, corneas and neuroretinal cells for patients with various forms of blindness and even red blood cells for transfusion.
"With successful storage methods, pig corneas, islets and cells (including red blood cells) could be successfully transported from a developed country where genetically engineered animals would be bred and housed to a developing country where need for the biological product is great," they said in the Lancet.
They added, "The need for a new source of organs and cells for clinical transplantation has been clear for decades. Tissues such as pancreatic islets and neuronal cells from deceased human donors have never been sufficient. Xenotransplantation (pigs to people) could resolve this issue."
There is an increasing availability of pigs that have undergone genetic modifications to protect tissues to be transplanted from human immune response. However, significant barriers need to be overcome before pig organ xenotransplantation can become a clinical therapy, "although clinical trials of pig islet, neuronal-cell and corneal xenotransplantation are imminent. A government regulated clinical trial of pig islet transplantation is taking place in New Zealand," the study said.
A diabetic monkey has survived for more than a year supported only by pig islets, suggesting that the technique will be physiologically successful. A potential problem arises for Type 1 diabetes patients, whose autoimmune response could destroy the new grafts over time (just as the patients' own pancreatic islet cells were destroyed).
However, regular re-transplantation could occur if this happened. Researchers are also studying 'encapsulated' islets. These islets are shielded from the body's immune system in a capsule, so that immunosuppression is not necessary.
Early trials have shown that transplantation of pig neuronal cells into non-human primates with a model of Parkinson's disease significantly improves locomotor function.
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