Bone marrow transplantation of CD117+ (c-Kit) stem cells and investigation of the bile acid transporter regulation in Abcb4-/- mice, a model of sclerosing cholangitis
Abcb4 (ATP-binding cassette sub family-b) or Mdr2 (multidrug resistance protein 2) is a gene which encodes for ABCB4 protein that mediates the transportation of phospholipids across the canalicular membrane of hepatocytes into the bile. Functional loss of the ABCB4 transporter disturbs the excretion of phospholipids into bile, leading to toxic bile composition, bile duct alterations, and damaged bile duct epithelia resembling sclerosing cholangitis (1). Long term consequences are biliary cirrhosis, cholangiocarcinoma and liver failure (2).In Abcb4-/- mice, a model of sclerosing cholangitis, we aimed to investigate the regenerative potential of bone marrow transplantation (BM-Tx) and especially BM-Tx of desialylated CD117+ (c-Kit) stem cells. CD117 receptor expressing cells are hematopoietic progenitors, which bear the potential to differentiate into specialized cell types depending upon tissue environment. Based on these characteristics we analysed whether CD117+ cells differentiated into hepatocytes, e.g. by by cell fusion (3).Successfully isolated mouse (BALB/c-GFP) hematopoietic stem cells were sorted with the help of hematopoietic (Lin- CD117+) cell surface markers. Neuraminidase treated CD117+ progenitor cells were transplanted into lethally irradiated Abcb4-/- (BALB/c-GFP → BALB/c-Abcb4-/- allogenic transplantation) mice at the age of 6-7 weeks. At respective time points (i.e 2 and 20 weeks after transplantation, actually 8 and 26 weeks of age) mice were sacrificed and underlying immunomodulatory and matrix remodelling processes were analyzed. In addition, we elucidated molecular and biochemical analysis of hepatic bile acid transport in Abcb4-/- mice during the course of the disease. The present studies demonstrated a reduced temporary graft versus host disease and unaltered liver integrity. Fusion of transplanted (GFP+) cells with host (Abcb4-/-) hepatocytes was a rare event. Whereas lots of GFP+ cells, including T-cells infiltrated around portal fields could be detected. Significant upregulation of proinflammatory (Th1) and profibrogenic (Th2) cytokines revealed enhanced fibrosis in the longterm observation. Furthermore, bile acid transporter data revealed an altered gene regulation at basolateral and canalicular membrane in chronically injured liver of Abcb4-/- mice.The present work suggests that transcriptional changes of bile acid transporters may open new molecular targets for therapy of liver fibrosis in Abcb4-/- mice. These data from fibrogenesis in Abcb4-/- mice are of great interest for translational antifibrotic strategies.
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