Primitive and proximal hepatic stem cells

Patent Number: 7,413,897

The liver is one of the organs that has been demonstrated to respond to stem cell therapy both in animal models and in clinical trials.  It is known that the liver has endogenous stem cells, but also that bone marrow stem cells can differentiate into liver cells.  In fact, it is published that bone marrow stem cell administered intravenously to patients with liver failure induce a therapeutic benefit.

The current patent covers a type of stem cell that exists endogenously in the liver.  The first independent claims essentially states that what is covered is: liver stem cells that possess the marker Ep-CAM (an epithelial marker involved functionally in cell adhesion), lack expression of alpha-fetoprotein, are capable of giving rise to proximal hepatic stem cells, which in turn are capable of differentiating into either hepatocytic progeny or biliary progeny.  The dependent claims cover expression of AC133, c-kit, and several other molecules that are generally associated with endogenous tissue stem cells.

This patent is interesting because others have discussed some similar tissue specific stem cells in other areas of the body.  For example, in the brain expression of CD133 denotes a neural stem cell phenotype.  Other tissue specific stem cells may be purified based on the side population phenotype. 

One of the strengths of the current patent is that liver cells in general are inherently of weaker immunogenicity as opposed to other organs.  In addition to in vivo use extracorporeal technologies are becoming increasingly advanced and cells such as the ones covered in the patent will become more and more valuable for entities making artificial livers.

View this patent on the USPTO website.