How Do You Grow A Heart?

Friday, July 12, 2013

 Regenerative Medicine
Researchers today are looking to engineer entire new organs, to enable transplants without the risk of rejection by the recipient's immune system. The strategy using tissue engineering, involves removing all the cells from a donor organ then to take the protein scaffold left behind and repopulate it with stem cells immunologically matched to the patient in need.

How do you make a working human heart? Scientists can turn stem cells into beating heart cells, but getting them to organize into a full heart organ requires a scaffold.

 At the Massachusetts General Hospital in Boston, Harald Ott and his team are reusing the scaffold that nature provides in a process known as tissue engineering. In the video above, Brendan Maher from Nature finds out how the technique could be used to develop parts of the heart, like the aortic root and valve, for transplant.

regenerative medicine tissue engineering
Image Source: Nik Spencer / Nature

What is Tissue Engineering?

Tissue engineering is the study of the growth of new connective tissues, or organs, from cells and a collagenous scaffold to produce a fully functional organ for implantation back into the donor host.

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This technique allows organs to be grown from implantation (rather than transplantation) and thereby eliminates the possibility of imunological rejection of the organ. 

The starting point for any tissue-engineered organ is the harvesting of small amounts of tissue from the future recipient of the tissue engineered organ. With today's induced pluripotent stem cell (iPS) techniques getting better and better, soon this may soon be as simple as providing a few drops of blood.

Cells from biopses or other sources are then cultured from explants or a collagenase digestion to create a "cell bank". These cells are then further cultured on collagenous substrates, under the correct physiological conditions, to form  the tissue engineered parts for implantation. 

The process is carried out in a tissue culture facility as in the video above to maintain a sterile environment. Cellular biochemical and physical activity can be enhanced by the addition of growth factors or cytokines, also by the use of physical stimulation. The tensioning-Culture Force Monitor applies minute physical loads to stimulate the resident cell population in the collagenous scaffold into bio-chemical and bio-physical activity normally associated with organogenesis and tissue repair.

tissue engineering

After further tissue culture under the correct conditions, the resident cells in the tissue engineered part will disolve the original collagen scaffold and secrete a new collagen rich neo-tissue, the construct can then be implanted back into the patient from whom the cells were originally removed. 

The techniques now being perfected to create a heart, will one day be used potentially for any organ, or could be used to develop bionic and transhuman body augmentation systems that will readily be accepted into the body.

One other key potential use of tissue engineering is in the development of in vitro meat.

For now, a key path to realizing personalized regenerative medicine is potentially available with the development of techniques like tissue engineering.