Viability and differentiation of human hepatocytes immunoprotected by macroencapsulation and transplanted in rats

Objectives - To determine the viability and differentiation of human hepato cytes immunoprotected by encapsulation and transplanted in rats without imm unosuppression. Methods - Freshly isolated human hepatocytes were encapsulated in hollow fi bers and transplanted in the peritoneal cavity of immunocompetent rats. The fibers were explanted for analysis at D3, D7 and D14 Following transplanta tion. Morphological features under light and electron microscopy and gene e xpress,on were compared to those of non-transplanted encapsulated hepatocyt es (DO). Human cytochrome P450 3A and albumin mRNAs were quantified by Nort hern blot. Cytochrome P450 3A proteins were detected by Western blot and cy tochrome P450 3A enzyme activity was assessed by measuring the formation of 6 beta-hydroxytestosterone by high performance liquid chromatography. Results - Transplanted hepatocytes were more than 60% viable and exhibited morphological criteria of hepatocytic differentiation up to D7 Albumin and cytochrome P450 3A transcripts were detected up to D14. At D3 and D7, album in mRNA levels were of 30%, compared to control DO hepatocytes, while cytoc hrome P450 3A5 and cytochrome P450 3A4 mRNA levels were 65% and 0%, Cytochr ome P450 3A immunoreactivity was detected Western blot up to D14 and 6 beta -hydroxylase activity was 17% at D3 compared to DO, supporting with disappe arance of cytochrome P450 3A4 mRNA. Conclusions - Human hepatocytes remain viable for a short period, following encapsulation and intraperitoneal transplantation in rot. Other experiment al conditions need to be tested to prevent or delay a decrease in hepatocyt e specific gene expression.