Protection of living tissues and organs is very important to ensure a successful transplant. Storage of living tissue from donor tissue removal to transplantation is one of the most important factors for successful tissue transplantation. The purpose of living tissue storage is to preserve the viability of mammalian cells, and various methods have been developed to extend the period in which donor tissue can be stored without losing cell integrity. Today, low temperature is used as the primary organ protection method. Generally, cells are kept frozen at -196 ° C. Survival after such storage was increased by controlled temperature freezing. However, as with ES cells (embryonic stem cells), EG cells (embryonic genital cells), and induced pluripotent stem (iPS) cells, cell survival after freezing may be low, ie 20-40%.
Being able to protect these cells more successfully provides a great advantage for researchers in the field of stem cell research. Being able to protect other cells such as platelets from freezing in the long term is also beneficial. Likewise, research in extending time interventions for transplantation of solid organs and the development of optimal perfusion fluids that protect against ischemia continue to be an active area of research. These studies are looking for various preservation solutions to protect organs. Many organs after transplantation suffer from the generation of free radicals following reperfusion. Restoration of blood flow becomes a trigger for injury. And then lipid peroxidation of the biomembrane leads to membrane failure and as a result the transplanted organ fails. A logical target in this case is a protective fluid that limits cell damage by preventing peroxylipide formation. Such a protection fluid limits cell division and reproduction.
Storage at room temperature can also potentially prevent damage to the small vessel endothelium seen during freezing and delicate tissues such as the cornea that do not survive freezing well. These tissues can be kept for 4 to 24 hours. In addition, thanks to advances in tissue engineering, cultured skin and cartilage have reached the level of clinical application and demanded long-term storage techniques for optimum use. Transplantation of xenogenic organs from genetically engineered animal donors can likewise benefit from the possibility of longer-term organ preservation. The polyphenols in green tea have been found to promote the preservation of tissues such as blood vessels, cornea, nerves, islet tissues, articular cartilage, and myocardium at room temperature. In the case of hematopoietic stem cells, more polyphenols suppress the differentiation of cells into erythrocytes, T and B cells. These findings raise the possibility of a new method for the tissue bank that does not require freezing.
Research has been done on green tea polyphenols applications. In the field of transplant medicine, there have been difficult problems associated with graft tissues and organs, including loss of viability and function, hyperplasia and immunological rejection of grafted tissues after transplantation. To overcome these problems, it is recommended to use a protection medium containing EGCG, which has been shown to be antioxidative. Polyphenols have recently gained attention as components of functional foods, since the 1980s they have been shown to have various bioactivities such as anticancer activity, antimicrobal and anti-virus activity. Therefore, there are polyphenols for a variety of applications. However, no research has been done on the use of polyphenols for the preservation of various tissues and organs. It is believed that such applications are possible, an interesting phenomenon has recently been found regarding the effects of polyphenols on mammalian cells and living tissues. This weherein describes the effects of polyphenols on living cells and tissues and presents possible applications for the protection of polyphenols.
Protection Solutions for Organ and Tissue Transplantation
Polyphenols have a hydroxyl group attached to the 2nd carbon and completely different properties from other phenolic chemicals such as hydroxybenzene. It is possible to classify these polyphenols as flavonoid hydrolysis type tannins and other polyphenols. Various chemical compounds are known within the polyphenol group. Representative members include catechin found in green tea and oolong tea, and anthocyanin, the red pigment in red wine. The antioxidant effects of green tea polyphenol and catechin as well as proanthocyanidine are particularly effective and these substances are known to be associated with a lower morbidity in heart disease. In addition, it has been reported that the proliferation of cancer cells is suppressed by polyphenols. The success rate of organ transplantation has increased in the last decade due to advances in surgical techniques and the development of new immunosuppressive agents. For example, 4 million transplants were performed in 2002 in the USA, where transplantation is often performed with organs or tissues taken from brain-dead donors.
Donor organs or tissues are routinely transported in various preservation solutions. UW (University of Wisconsin) solution and Euro-Collins solution are the most frequently used first and second protection solutions. These preservation solutions are mainly used for transport of the kidneys, liver or pancreas. However, they cannot protect organs at 4 degrees for more than 24 hours. In light of the increasing demand for donor organs and tissues, there is an urgent need for better preservation solutions, research and development of such solutions. When organs or tissues are isolated from a donor, their blood circulation stops and their physiological activity rapidly decreases. Varying degrees of ischemia are common for these organs, and free radicals are produced upon resumption of blood flow. This leads to lipid peroxidation of the cell membrane, causing membrane damage and various dysfunctions in the transplanted organs.
Developing a protection solution that can minimize oxidation and cell damage can solve this problem. One of the traditional methods used to solve this problem has been frost protection. Although viable tissues and cells are routinely preserved at -196 ° C, freezing and subsequent thawing causes some structural damage. For example, frozen blood vessels often have damage that makes their transplant difficult, and corneas cannot be preserved at 4 degrees for more than a week without significant damage. Studies show that cell damage is mainly caused by activated oxygen molecules that arise from freezing and thawing processes. But it also shows that it occurs even after exposure to normal temperatures after removing living tissue and cells from the donor.
Recent advances in tissue engineering are now at the peak of providing clinically useful cultured skin, cartilage and corneaspecimens. However, these cultured tissues also require preservation, and better methods for long-term preservation would be beneficial to ensure their successful application in the clinical field. To this end, the antioxidant polyphenol is presented as a means of EGCG, which prevents cell damage associated with organ and tissue protection. By using EGCG, longer storage and more successful transplantation can be achieved by protecting living tissues and organs.
Control of Mammalian Cell Proliferation
To study the effects of EGCG on cell proliferation, the rat fibroblast cell line, L-929, was grown in EMEM (with kanamycin 60 mg / l) supplemented with 10% fetal bovine serum. A cell proliferation test was performed at a density of 1.76 x 10 cells, 5 cells / ml. Polyphenol (250 µg / ml concentration) was added to another culture system as a control. Although the effects of polyphenol in the rat fibroblast culture cell proliferation is still active, the polyphenol system, cells are rounded. The cell population was increased to 1 x 10 6 / ml onthe four days after culturing the cells, but proliferation decreased after 1 week of treatment and continued when the polyphenol was removed from the culture medium.
The effects of polyphenol on the cell cycle have also been evaluated. For cells treated with polyphenol, the cell number in S phase reached 0 after 9 hours in culture, although the cell number in the G0, G1 and G2 / M-phases increased. A similar phenomenon was observed in porcine hepatocytes and, in addition, the viable cell population was not reduced. Good results were also obtained for the protective effects of green tea polyphenol against reactive oxygen species that cause oxidative stress in cultured rat calvarial osteoblasts.
Author: Ozlem Guvenc Agaoglu