Bioartificial liver device
Encyclopedia
A bioartificial liver device (BAL) is an artificial extracorporeal
supportive device for an individual who is suffering from acute liver failure.
s, with embedded hepatocytes (liver cell
s) that perform the functions of a normal liver
. They process oxygenated blood plasma
, which is separated from the other blood
constituents.
Several types of BALs are being developed, including hollow fiber systems and flat membrane sheet systems.
, which is injected into a series of hollow fibers. In the case of collagen, the suspension is then gelled within the fibers, usually by a temperature change. The hepatocytes then contract the gel by their attachment to the collagen matrix, reducing the volume of the suspension and creating a flow space within the fibers. Nutrient media is circulated through the fibers to sustain the cells. During use, plasma is removed from the patients blood. The patient's plasma is fed into the space surrounding the fibers. The fibers, which are composed of a semi-permeable membrane, facilitate transfer of toxins, nutrients and other chemicals between the blood and the suspended cells. The membrane also keeps immune bodies, such as immunoglobulins, from passing to the cells to
prevent an immune system rejection.
), is that metabolic functions (such as lipid
and plasma lipoprotein
synthesis, regulation of carbohydrate
homeostasis
, production of serum albumin
and clotting factors, etc.), in addition to detoxification, can be replicated without the use of multiple devices. There are currently several BAL devices currently in clinical trials.
A series of studies in 2004 showed that a BAL device reduced mortality by about half in acute liver failure cases. The studies, which covered 171 patients in the U.S. and Europe, compared standard supportive care to the use of a bioreactor device using pig liver cells.
Extracorporeal
An extracorporeal medical procedure is a medical procedure which is performed outside the body.-Circulatory procedures:A procedure in which blood is taken from a patient's circulation to have a process applied to it before it is returned to the circulation...
supportive device for an individual who is suffering from acute liver failure.
Use
The purpose of BAL-type devices, currently, is not to permanently replace liver functions, but to serve as a supportive device, either allowing the liver to regenerate properly upon acute liver failure, or to bridge the individual's liver functions until a transplant is possible.Function
BALs are essentially bioreactorBioreactor
A bioreactor may refer to any manufactured or engineered device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This...
s, with embedded hepatocytes (liver cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s) that perform the functions of a normal liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. They process oxygenated blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
, which is separated from the other blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
constituents.
Several types of BALs are being developed, including hollow fiber systems and flat membrane sheet systems.
Hollow fiber system
One type of BAL is similar to kidney dialysis systems that employ a hollow fiber cartridge. Hepatocytes are suspended in a gel solution, such as collagenCollagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, which is injected into a series of hollow fibers. In the case of collagen, the suspension is then gelled within the fibers, usually by a temperature change. The hepatocytes then contract the gel by their attachment to the collagen matrix, reducing the volume of the suspension and creating a flow space within the fibers. Nutrient media is circulated through the fibers to sustain the cells. During use, plasma is removed from the patients blood. The patient's plasma is fed into the space surrounding the fibers. The fibers, which are composed of a semi-permeable membrane, facilitate transfer of toxins, nutrients and other chemicals between the blood and the suspended cells. The membrane also keeps immune bodies, such as immunoglobulins, from passing to the cells to
prevent an immune system rejection.
Comparison to liver dialysis
The advantages of using a BAL, over other dialysis-type devices (e.g. liver dialysisLiver dialysis
Liver dialysis is a detoxification treatment for liver failure and has shown promise for patients with hepatorenal syndrome. It is similar to hemodialysis and based on the same principles...
), is that metabolic functions (such as lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
and plasma lipoprotein
Lipoprotein
A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...
synthesis, regulation of carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
homeostasis
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
, production of serum albumin
Human serum albumin
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin constitutes about half of the blood serum protein...
and clotting factors, etc.), in addition to detoxification, can be replicated without the use of multiple devices. There are currently several BAL devices currently in clinical trials.
A series of studies in 2004 showed that a BAL device reduced mortality by about half in acute liver failure cases. The studies, which covered 171 patients in the U.S. and Europe, compared standard supportive care to the use of a bioreactor device using pig liver cells.
See also
- Artificial extracorporeal liver supportArtificial extracorporeal liver supportArtificial extracorporeal liver support is term that is used to describe measures that are used to carry-out liver function and are outside of the body.Devices that support liver function outside of the body are:*Liver dialysis*Bioartificial liver devices...
- Liver dialysisLiver dialysisLiver dialysis is a detoxification treatment for liver failure and has shown promise for patients with hepatorenal syndrome. It is similar to hemodialysis and based on the same principles...
- Tissue engineeringTissue engineeringTissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...