Hepatic stellate cell activation in nonalcoholic steatohepatitis and fatty liver.

Factors associated with the development of fibrosis in nonalcoholic steatohepatitis (NASH) are largely unknown, although an association with increased hepatic iron has been suggested. Hepatic stellate cells are the principal collagen-producing cells in many liver diseases and when activated express alpha-smooth muscle actin (alpha-SMA). Hepatic stellate cell activation and association with fibrosis, necroinflammatory activity, steatosis, and stainable iron in 60 cases of NASH and 16 cases of steatosis were evaluated. All 76 patients were obese or had other risk factors for NASH. All biopsy specimens were stained for alpha-smooth muscle actin to evaluate the pattern of hepatic stellate cell activation and were evaluated for inflammatory activity (0 to 3), fibrosis (0 to 4), and stainable iron stores (0 to 4). The zonal location of activated stellate cells was recorded, and the degree of activation was graded as high-grade or low-grade based on the percentage of lobular alpha-SMA+ cells. Activated stellate cells were identified in the hepatic lobule in 74 of 76 biopsy specimens and graded as low-grade in 26 and high-grade in 48. Zone 3 was involved in 72 of 74 positive cases, and in 33 cases, the activated stellate cells were preferentially located in zone 3. The degree of stellate cell activation correlated with fibrosis but not with inflammatory activity, severity of steatosis, or stainable iron. In most cases, the degree of stellate cell activation paralleled the degree of hepatic fibrosis, but in 25 cases, the degree of hepatic stellate cell activation was greater than expected, raising the question of whether such patients are at risk for disease progression.