Alpha-l-antitrypsin (alpha1AT) is a plasma protein, produced in the liver that inhibits elastase, alpha1AT-deficiency is an autosomal recessive disorder that affects approximately 105 individuals in the US. Liver injury in alpha1AT-deficiency is caused by the hepatotoxic effects of mutant alpha1AT retained within the endoplasmic reticulum (ER) of hepatocytes, and emphysema by uninhibited proteolytic damage to elastic tissue in the lung parenchyma. Orthoptic liver transplantation is the only curative therapy for alpha1AT-mediated liver disease. If a reliable source of hepatocytes were available, they could conceivably be used to replace 20-25% of the host liver, elevating plasma levels of alpha1AT to greater than 10 muM, and preventing pulmonary toxicity due to alpha1AT-deficiency. We have identified multipotent adult progenitor cells, or MAPC, that can be cultured from human, mouse and rat bone marrow (BM). Single MAPC differentiate into mesodermal, neuroectoderm-like cells and functioning hepatocyte-like cells in vitro. MAPC do not form tumors when infused IV, IM or SQ, but differentiate in response to local cues into hematopoietic cells and epithelium of lung, intestine and liver. For MAPC derived hepatocytes to be suitable for therapy of alpha1AT, or other liver disorders, better characterization of the in vitro differentiation process will be needed. In addition, we will need to demonstrate that MAPC-derived cells function like hepatocytes in vivo. We propose three aims to determine whether MAPC-derived hepatocytes may be a source of cells to treat alpha1AT-deficiency mediated pulmonary and/or liver disease. Studies in SA1 will further demonstrate that hepatocyte like cells can be generated from bone marrow derived MAPC, and develop methods to select progenitors/precursors for hepatocytes generated during culture. Selection of such progenitors will serve two purposes: characterization of differentiation from pluripotent adult stem cells to hepatocytes, and generation of a potential source of cells for effective transplantation in liver disease. Studies described in SA2 that will assess all functions of mature hepatocytes in spheroid cultures should help confirm that hepatocytes generated from BM MAPC are similar to hepatocytes derived from primary liver. Studies in SA3 will establish whether MAPC themselves, MAPC-derived hepatocyte progenitors or mature hepatocytes can restore liver function in vivo, in the setting of hepatocyte cell death and in the setting of abnormal liver function but without liver cell death. This should lay the groundwork for future studies testing whether MAPC or MAPC-derived hepatocyte progenitors/hepatocytes can serve as a suitable source of cells for therapy of alpha1AT, a single gene defect associated with lung damage and/or liver failure.
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