DELIVERY OF WHOLE LIVER EQUIVALENT HEPATOCYTE MASS USING POLYMER DEVICES AND HEPATOTROPHIC STIMULATION

Using hepatocytes injected into prevascularized polymer sponge devices , we studied hepatocyte survival and function after delivery of a whol e liver-equivalent of cells into rats. LEW rats and enzyme-deficient G unn rats served as recipients, respectively. Totally, 28.5 cm2 (0.5-cm thick) of polyvinyl alcohol sponges were implanted per animal. Hepato trophic stimulation was induced by portacaval shunt and partial (70% o r 30%) hepatectomy. Recipient rats received 5 x 10(8) hepatocytes (equ ivalent to whole rat liver) which were harvested from LEW and Wistar d onors, respectively. After engraftment, histologic examination reveale d hepatocyte remodeling in the device with capillaries lining plates o f hepatocytes, and also tubular structures resembling early biliary ra dicles. BrdU staining revealed DNA synthesis in hepatocytes, providing evidence of regeneration within the grafts. Quantification of viable hepatocyte area at various time points was performed using computer-as sisted morphometry. We then estimated a range of cell numbers from the quantitated cell area. The number of hepatocytes viable at day 7 was estimated at 27.5-46.0% and 6.6-11.0% in the mesentery and subcutaneou s site, respectively. Thus the average number was estimated between 10 .8% and 18.0% of initially injected hepatocytes. In the Gunn rat, expe riment, experimental rats that received normal Wistar hepatocytes show ed a significantly greater decrease in total serum bilirubin compared with the concurrent control Gunn rats (P<0.01). At week 1, serum bilir ubin in experimental rats decreased to 74.7% (6.80+/-0.16 mg/dl) of pr etransplantation level (9.10+/-0.47 mg/dl) and this was 71.4% of the c ontrol rats' bilirubin level (9.53+/-0.37 mg/dl). In conclusion, a hep atocyte mass equivalent, to a whole rat liver can be delivered into pr evascularized polymer sponge devices. At day 7 between 10.8% and 18.0% of these hepatocytes were estimated to be engrafted and functioning. Further optimization of this technique is necessary before clinical ap plication is considered.