Hypoxia leads to necrotic hepatocyte death

Hepatocyte transplantation is being investigated as a therapy for liver disease; however, its success has been limited by rapid death of the cells following transplantation. This study was dedicated to elucidating the mode of death responsible for loss of transplanted hepatocytes in order to guide future strategies for promoting their survival. Using a tissue engineering model, it was found that the environment within polymer scaffolds containing transplanted cells was hypoxic after 5 days in vivo, with (90 +/- 3)% of hepatocytes existing at pO(2) < 10 mmHg. The primary mode of hepatocyte death in response to hypoxic conditions of 0 or 2 vol % oxygen was then determined in vitro. Several assays for features of apoptosis and necrosis demonstrated that hepatocytes cultured in an anoxic environment died via necrosis, while culture at 2% oxygen inhibited proliferation. These results suggest it will not be possible to prevent hepatocyte death by interfering with the apoptotic process, and hypoxic conditions in the transplants must instead be addressed. The finding that the environment within cell transplantation scaffolds is hypoxic is likely applicable to many cell-based therapies, and a similar analysis of the primary mode of death for other cell types in response to hypoxia may be valuable in guiding future strategies for their transplantation.