Major strides are being made in replenishing some of the simpler body parts such as bladders and airways " It's a tailored situation, and the biomaterials need to be responsive and to understand or communicate to the body
In the future we might be growing organs such as hearts and livers in the lab for transplants, rather than waiting for donors. Or maybe injecting "smart" materials into the body to tackle injury or chronic disease.
There's a way to go yet before we can generate complex organs on demand in a lab. But simpler organs can already be "grown" outside the body using a patient's own cells.
One way is to take donor tissue and remove the donor's cells, and then grow the patient's own cells on a scaffold in a lab, before implanting it. Italian surgeon Paolo Macchiarini hit the headlines in 2008 when he replaced part of a patient's airway using this procedure.
Another and this time donor-free way is to make a three-dimensional scaffold out of biomaterials in the lab and then encourage patient's cells to grow on that. Surgeon Anthony Atala at Wake Forest University in North Carolina has used this method for patients who needed bladder reconstruction.
"The most success clinically so far has been in the area of soft tissues, such as bladder and airways, and in skin regeneration for burns patients," says Prof Fergal O'Brien, who heads the tissue engineering research group at the Royal College of Surgeons in Ireland. "But the concept of being able to engineer an entire heart or liver or kidney is probably a long way down the line."
Scaffolds for repair works
Rather than growing organs or big chunks of tissue outside the body in the lab, O'Brien's group is developing collagen-based scaffolds that can be implanted into the patient where they can trigger the body's own repair mechanism to encourage replacement tissue to grow.
Their technologies include a bone-graft substitute called HydroxyColl, which is designed to encourage repair in damaged or diseased bone. "Hopefully we will have that in clinical [ human] trials very soon," he says.
For other tissues, such as the softer cartilage that cushions joints, it's likely the body will need a bit more help - possibly stem cells or gene therapy - to encourage long-term repair, he notes. "Really what we are developing is temporary strategies, and ultimately it will be the body itself which will lead to the solution - we engineer a bone or cartilage graft and, over time, the body replaces it with its own bone or cartilage," says O'Brien.
But there are challenges. "It's one thing to create a tissue or organ in the lab, it's a completely different challenge to make sure that the tissue or organ isn't rejected by the body's immune system. Plus the new tissue will also need to build its own blood supply if it is to survive."
For Prof Abhay Pandit, who directs the Science Foundation Ireland-funded Network of Excellence for Functional Biomaterials, getting the right response from the body is paramount. His group at NUI Galway also designs biomaterials that promote healing in the body and then degrade when their job is done. But it is definitely not a one-size-fits-all solution.
"You could be looking at a chronic wound like a bed sore, a damaged heart valve or artery, damaged knees, even a spinal-cord injury," he says. "It's a very tailored situation, and the biomaterials need to be responsive and to understand or communicate to the body in that particular condition."
Getting in early is important, whether you are looking to address damage to nerves, skin or heart muscle, says Pandit. "The body causes a scar, it's a protective mechanism to limit the damage and that is a healthy thing to do," he says. "But we want to stop that scarring process by putting in a biomaterial that can understand what is going on. It's a war against scar - we want the scar to stop, there may be some function left that we can target."
Pandit foresees that more and more "smart" biomaterials will be able to sense and respond to the environment of an injury. "I think we will see more targeted delivery, where you could even inject a biomaterial into the body and it will 'know' where to go to promote healing," he says.
O'Brien reckons that gene therapy has "huge potential" in regenerative medicine, where engineered cells at an injury site could act as tiny factories, making proteins that promote healing.
But he believes it will still be several decades before we see complicated organs being grown or made to order in labs: "I think it's going to be a long, long time before we will see full, multi-scale organs being engineered," he says.
