Identification of Optimal Harvest Sites of Ileal Stem Cells for Treatment of Bile Acid Malabsorption in a Dog Model
Abstracts
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Ileal mucosal stem cells expressing the sodium-dependent ileal bile acid transporter (IBAT) have been successfully transplanted into jejunum of rodents in projects aimed at creating a "neo-ileum" to treat bile acid malabsorption (Stelzner, J Surg Res 86:269;1999). To find optimal harvest sites for a dog model of stem cell transplantation, the exact location of peak IBAT expression in the donor ileum needs to be known. Therefore we mapped IBAT function, mRNA and IBAT protein in the ileum of Beagle dogs (N=3). Methods: 80 mucosal samples were obtained from the small intestine of each dog. Na+-dependent (active) and -independent (passive) bile acid uptake rates were measured using a standardized everted sleeve technique. IBAT mRNA concentrations were determined by real-time fluorescent PCR and IBAT protein concentrations by quantitative immunohistochemistry and Western blotting. Results: The small bowel measured 208?17 cm(mean?SEM) in length. Active and passive uptake rates were found to follow distinct distribution curves. Significant active uptake was seen only in the terminal 40 cm (Graph) and peaked at 479?176 pM/mm2. Depending on location, active uptake was 10%-58% of total uptake. IBAT mRNA and protein distributions corroborated uptake curves. Conclusion: The terminal 10 - 40 cm of ileum have the highest bile acid uptake capacity and appear as the most promising donor site for ileal stem cell transplants to create a "neo-ileum" in dogs. |
