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 whole liver-equivalent of cells into rats. LEW rats and enzyme-deficient Gunn rats served as recipients, respectively. Totally, 28.5 cm2 (0.5-cm thick) of polyvinyl alcohol sponges were implanted per animal. Hepatotrophic stimulation was induced by portacaval shunt and partial (70% or 30%) hepatectomy. Recipient rats received 5 x 10(8) hepatocytes (equivalent to whole rat liver) which were harvested from LEW and Wistar donors, respectively. After engraftment, histologic examination revealed hepatocyte remodeling in the device with capillaries lining plates of hepatocytes, and also tubular structures resembling early biliary radicles. 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-assisted 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 subcutaneous site, respectively. Thus the average number was estimated between 10.8% and 18.0% of initially injected hepatocytes. In the Gunn rat experiment, experimental rats that received normal Wistar hepatocytes showed a significantly greater decrease in total serum bilirubin compared with the concurrent control Gunn rats (P < 0.01). At week 1, serum bilirubin in experimental rats decreased to 74.7% (6.80 +/- 0.46 mg/dl) of pretransplantation level (9.10 +/- 0.47 mg/dl) and this was 71.4% of the control rats' bilirubin level (9.53 +/- 0.37 mg/dl). In conclusion, a hepatocyte mass equivalent to a whole rat liver can be delivered into prevascularized 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 application is considered.