PCSK9 and metabolic dysfunction-associated steatohepatitis: However, some studies have found the unfavorable evidence that high-cholesterol diets in PCSK9 knockout mice showed increasing hepatic free cholesterol and cholesterol crystals, and fibrotic steatohepatitis, even with a higher predisposition to liver cancer as compared with WT mice [28], and that PCSK9 KO exacerbated NASH, fibrosis, and liver injury in the presence of excess dietary fats in mice [13].