Biomedical Engineering Reference
In-Depth Information
fiblasts,
58
stellate cells,
59
fetal hepatocytes,
60
and pancreatic islet
cells.
61
21.5.3
Cell Sources
Cell sources are very important for liver tissue engineering because
itisnecessarytochoosecellsthatdemonstratetheparticularpheno-
typeofinterest.
62
Thevariouscellsourcesareprimaryhumanhepa-
tocytes, stem cells, immortalized human hepatocytes, the human
hepatomacellline,andprimaryxenogenichepatocytes.Thevarious
cell sources for livertissue engineering are discussed.
Human hepatocytes seem to be the natural choice, and they are
very biocompatible to host for liver tissue engineering, although
there are scarce, owing to a competing demand of liver transplan-
tation, and there is the logistic problem of obtaining good-quality
hepatocytes and cryopreservation of the cells.
63
However, liver-
specific functions of the daughter cells after replication of adult
human hepatocytes
in vitro
is generally unstable.
Xenotransplantation utilized hepatocytes of animals. The pri-
mary animal hepatocytes engraft e
ciently and, being fully differ-
entiated, can produce immediate metabolic support. The rodent
hepatocytes have an apparently unlimited proliferative poten-
tial, although they have constitutive telomerase activity.
64
Primary
porcine hepatocytes have been widely used because they exhibit
P450 function and synthesis of urea, albumin, and other proteins
and are activated by growth factors, similar to human hepato-
cytes, although they have several limitations such as the risk of
xenozoonisis
65
and immunerejection by the patient.
62
Anew,promisingwayisthediscoveryofliverstemcells,because
stem cells are an unique source of self-renewing cells within the
human body and there are some stem cells present within
66
as
well as outside the liver,
67
which can differentiate into fully mature
hepatocytes. Hepatic stem cells were identified to exist in adult
rodent and human liver by coexpression of stem cell and hepato-
cytic lineage markers. Hepatic oval cells are thought to share with
hematopoietic stem cells.
68
Liver stem cells are also described as
bipolarbecausetheycoexpressbiliaryandhepatocyticmarkersand
Search WWH ::
Custom Search