الفهرس Only 14 pages are availabe for public view
 |  | from | 199 |  |  |
| | | from | 199 | | |
Abstract
wide variety of chronic injuries to hepatocytes caused by viral hepatitis, alcohol abuse, drugs, autoimmune attack and metabolic diseases might lead to liver cirrhosis. Liver transplantation is considered as the gold standard for the treatment of acute and end-stage chronic liver diseases. With the growing disparity between the number of suitable donor organs and patients waiting for transplantation, due to the limited availability of donor organs, the transplantation of isolated hepatocytes is a versatile, minimally invasive and safe alternative to whole organ replacement.Hepatic and hematopoietic tissues maintain a close association throughout the lifespan of mammals, and stem cells have been identified in adult tissues, including liver, pancreas, brain, heart and epithelial lineages and their potential for treating a wide variety of common and uncommon diseases is almost as limitless as their ability to undergo cell division. Nonetheless, this therapeutic potential will only be fulfilled if stem cells can be isolated and purified in numbers large enough to truly affect organ function. This would mean not only that the cells are present in sufficient number but also that they function as efficiently as the cell population that they are designed to replace. Accordingly, although it is difficult to predict the ultimate utility of stem cell–based therapy at this time, it is not difficult to conclude that this is an enormously important area of scientific research, one that has great potential monetary rewards as well. There are other cell types that may be useful to restore liver function such as hepatocytes themselves, adult liver stem cells, bone marrow derived cells, and human cord blood or fetal human tissue. In contrast, cellular therapy using circulating monocytes has considerable advantages over currently proposed strategies using tissue-specific stem cells and ES cells. Circulating monocytes could be a relatively easy source of autologous cells, as a large number of monocytes can be obtained from living individuals without using invasive procedures. Furthermore, the generation of PCMO from monocytes is technically easy and quick and the ethical dilemma of using ES cells can be bypassed.The term de-differentiation signifies regression of adult already specialized differentiated body cells to a status of stem cells. De-differentiation is characterized as a multistep process that involves the loss of specific cellular traits and the release of silenced genes from repression secondary to reentering the cell cycle. Those PCMO, in contrast to monocytes, can also be induced to become cells of all 3 germ layers suggesting that PCMO represent a dedifferentiated entity.In possible future clinical applications, PCMO derived neohepatocytes may first be generated in vitro and upon autologous transplantation into patients may substitute for their endogenous counterparts. The fact that NeoHep cells can be easily “produced” in vitro in large quantities makes them an attractive source for parenchymal cells to be used in clinical transplantation, for artificial liver devices and as an in vitro tool for preclinical drug testing.