Tissue engineering of blood vessels
In the aging society, diseases related to cardiac and peripheral arteries become the major cause of death to the people. Some patients can be treated with medical care to maintain a living; however, those who have severe arterial problems, they must undergo surgical reconstruction to replace the diseased arteries with some healthy artieres that can have functions. A good substitute for a blood vessel must be strong, compliant, good suture retention, biocompatible, non-toxic, and low thrombogenicity.
There are some options for the substitutes. One option is to use autologous veins from the patient’s self. Mainly the autologous veins come from the saphenous veins of the patient’s legs. However, most patients’ saphenous veins are not suitable for their arterial replacements. Another option is the prosthetic conduit, such as ePTFE or Dacron. However, prosthetic conduits have very high chance of thrombosis in human bodies. Moreover, prosthetic conduits are dead, and they cannot respond to the living environment. They cannot healed when damaged. Thus, it is necessary to develop and grow a living, small-diametered blood vessel and implant it into human bodies. In human-made tissue engineered blood vessel, there are three components: a scaffold, the matrix, and the endothelial cell lining. The scaffold either prosthetic is biological; it provides mechanical supports and constructs the shape of the blood vessel. The matrix helps the endothelial cells to attach. The living endothelial cells develop to healthy, antithrombogenic blood vessel which provides blood flow. Endothelial progenitor cells(EPCs) are seeded on the scaffold in some cases. EPCs Different types of scaffolds are tried: nature scaffolds, permanent synthetic scaffolds, biodegradable synthetic scaffolds. For biodegradable synthetic scaffolds, polymers PGA are used as scaffolds. Then, they are lined up with endothelial cells. After awhile, the grafts look very similar to native arteries morphologically.
The reason I chose this paper is that I am really interested in finding the best substitute for a disease human artery. People eat too well, and a lot of people suffer conditions with ill arteries. This paper gives researchers several pathways into finding a good engineered blood vessel, and it also gives cons and pros for different types of scaffolds. Personally, I think biodegradable synthetic scaffolds will be the most useful and the best materials because they will be degraded after implanted into human bodies, which thus affects humans the least. Also, the materials are not very expensive and can be mass-produced.
11 comments:
Interesting paper, it is sure to have wide applications in fields, such as medicine. I was just wondering what issues determine whether a patient's saphenous veins is appropriate or not for surgical reconstruction? Does it have to do with differences in thickness or other properties?
sounds like a great alternative to autologous veins and prosthetic conduit. What are the limitations, if any, are there with this process as to the efficiency with respect to the length or thickness that can be achieved?
I've heard that this method can replace the traditional heart bypass surgery. However, since the materials used to make the vessels are biodegradable polymers. What will happen when they degrade in the body. Is there some kind of stem cells to be implanted together with the polymer so they can form the tissue or is there other methods to deal with the degradation of the biomaterial?
The paper states that the grafts morphologically resemble native arteries, but are they functionally similar enough to successfully replace native arteries? Additionally, what are the long term differences in scaffolds seeded with EPCs versus scaffolds implanted without EPCs?
The scaffold provides some kind of structure and support. When it degrades, do the cells and ECM maintain the structure or lose rigidity? If its mechanical properties become less desirable, how will that affect the blood vessel in the long run?
Hi. Panda:
Some patients do not have appropriate saphenous veins for surgical reconstruction because their saphenous are abnormal, poor quality, or lack of veins due to prior surgery.
to Ranjani
It might take sometimes for the cells to develop into a blood vessel. Also, right now, one of the limitations on the engineered blood vessel is the size. There is still no way to engineer a blood vessel with very small diameters.
To Yisu Jiang:
Biodegradable materials, such as PLLA, PGA, provide a scaffold for the stem cells to seed. In some methods, the materials will be degraded even before implanted into bodies. However, sometimes, engineered blood vessels have their biodegradable materials with them when implanted, and the biodegradable scaffold provides some mechanical strength for the vessel. After a few months, the scaffold will be degraded with no harm to the body
To Kate:
I think when the grafts just get implanted into the body, they are considered very weak in their mechanical strength, so they still need the scaffolds to provide them some strength. After the grafts are inside the body for awhile, they begin to gain more strengths and become fully developed as real blood vessels. So far, in many rat trials, the grafts behave the same as the native arteries.
For the scaffolds seeded with EPCs versus those without EPCs, I don't know the answer about it
The cells around the scaffold will maintain their shape and function after it is degraded. I think the blood vessel will have the same mechanical properties as normal native cells after it is degraded
My grandfather got a severe staph infection in his leg after a saphenous vein was removed during heart surgery. Therefore, it is my "unbiased" opinion that engineered blood vessels would be a wonderful breakthrough that could save many lives. I'm just wondering if the seeded EPCs are autologous or from a donor and how long before implantation does the scaffold need to be seeded with cells?
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