November 12, 2007

C.U. Developing Artificial Vascular System

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Imagine being able to grow new tissue in a laboratory from cells that can later be used to repair damaged organs. This possibility is becoming a reality, as Cornell researchers make remarkable strides with the development of an artificial microvascular system.
This technology mimics the vascular system of the human body, carrying oxygen, sugar, proteins and growth factors to cells contained within a scaffold. The system is composed of microchannels embedded in a water-based gel, holding millions of living cells which can be formed to fit desired shapes.
“Whereas most microfabrication is done into silicon or glass, here we are microfabricating into a living tissue to put in these capillaries,” said Prof. Abraham Stroock, chemical and bio-molecular engineering, a co-author of the study, “and we can then use these capillaries as the microvascular system to keep the tissue alive and direct the tissue towards the desired structure and biological function.”
The research is a key development in tissue engineering, as past technology could not adequately circulate vital fluids among cells within a scaffold.
“One of the limitations of growing tissue outside the body is that they’re not hooked up to a vascular system that nourishes them in the body,” said Prof. Lawrence Bonassar, biomedical engineering, another co-author of the study. “We can create an artificial vascular system to keep these tissues alive for longer and potentially make larger tissues than can be made with other existing technology.”
This research has implications for patients in need of tissue repair or replacement.
“We’re trying to grow a piece of living tissue that one day could be implanted back into a patient to repair a defect or an injured sight, or even replace a defective organ or tissue,” Stroock said.
This system can also be used to distribute varying nutrients to specific cells, enabling researchers to manipulate which cells develop into specific tissues. This may prove extremely useful for patients who, for example, require a sample containing both cartilage and bone for a knee replacement. This type of technique may be feasible within three to five years, according to Prof. Jason Spector of Weill Cornell Medical College.
Along with tissue engineering and implantation, complete organ growth and transplants using the new technology may be possible sometime in the future, as well.
“One of the main limitations of building tissue like liver or pancreas or kidney is the fact that they are vascularized inside the body,” said Bonassar. “Growing them outside the body or even taking them fully grown from outside the body and inserting them requires some connection to a vascular system. In many ways, this [microvascular system] could potentially be a very enabling technology for those kinds of efforts.”
The relationship between engineering and clinical medicine gives hope to the numerous patients currently in need of organ transplant or repair.
Lavonne Turner, marketing development manager for the International Association for Organ Donation, agreed that this research is promising, citing that “at the moment, there are over 96,000 people on the national donor registry.”
Furthermore, tissue developed by this technology may serve as a replacement for current animal testing procedures.
“These [tissues] can be used as a way to basically minimize the number of animal experiments that need to be done. Instead of doing an experiment on an animal to test for skin sensitivity or toxicity, if we have something that operates outside the body just like that tissue, then we can screen on that tissue rather than on that animal,” Bonassar said.
There still remain obstacles standing in the way of tissue growth and replacement using this technology.
“We need to figure out how to get these things that look like blood vessels to hook up to the blood vessels of the body,” Bonassar said.
Spector’s recent partnership with Bonassar and Stroock is designed to bring this clinical aspect to the study. The researchers received a seed grant in order to continue their study on how to clinically apply this technology and attach the microchannels to native blood vessels.
“These microchannels are analogous to capillaries within tissues. Even though this is an improvement, the ultimate goal is to build something that not only has microchannels but where the microchannels can coalesce into a larger microvessel that we can attach to blood vessels already present in the body,” Spector said.
Additionally, although this technology could be used to cultivate various tissues from stem cells, critical information required to treat conditions is still lacking. Spector used diabetes as an example, pointing out that researchers have yet to identify the actual stem cell that produces insulin.
“Once they do identify the insulin producing stem cell, we can move ahead and try to integrate that into our platform,” Spector said.