Deficiency of apoptosis-stimulating protein two of p53 promotes liver regeneration in mice by activating mammalian target of rapamycin

Although liver regeneration has been intensively studied in various ways, the mechanisms underlying liver regeneration remain elusive. Apoptosis-stimulating protein two of p53 (ASPP2) was discovered as a binding partner of p53 and plays an important role in regulating cell apoptosis and growth. However, the role of ASPP2 in hepatocyte proliferation and liver regeneration has not been reported. The expression profile of ASPP2 was measured in a mouse model with 70% partial hepatectomy (PH(X)). Liver regeneration and hepatocyte proliferation were detected in wild-type (ASPP2(+/+)) and ASPP2 haploinsufficient (ASPP2(+/−)) mice with PH(X). The mammalian target of rapamycin (mTOR) and autophagy pathways were analyzed in the ASPP2(+/+) and ASPP2(+/−) mice with PH(X). After rapamycin or 3-methyladenine (3-MA) treatment, hepatocyte proliferation and liver regeneration were analyzed in the ASPP2(+/+) and ASPP2(+/−) mice with PH(X). ASPP2 expression was shown to be upregulated at the early stage and downregulated at the late stage. Compared to the ASPP2(+/+) mice, liver regeneration was enhanced in ASPP2(+/−) mice with 70% PH(X). In addition, compared to the ASPP2(+/+) mice, the mTORC1 pathway was significantly upregulated and the autophagic pathway was downregulated in ASPP2(+/−)mice with 70% PH(X). Inhibition of the mTORC1 pathway significantly suppressed liver regeneration in ASPP2(+/−) mice with 70% PH(X). In contrast, disruption of the autophagic pathway further enhanced liver regeneration in ASPP2(+/−) mice with 70% PH(X). ASPP2 deficiency can promote liver regeneration through activating the mTORC1 pathway, which further regulates downstream molecules, such as those related to autophagy and p70S6K expression in mouse model post-PH(X).