TNFRSF12A mRNA Expression and Distribution of TNFRSF12A+ Cells in the Rate Liver during Thioacetamide-Induced Fibrogenesis

TNFRSF12A mRNA expression and the distribution of TNFRSF12A+ cells were studied in detail for the first time at different stages of fibrosis in the rat liver. Under physiological conditions, the expression level of TNFRSF12A mRNA was 0.224 (95% CI: 0.170–0.277). At the same time, cells expressing the TNFRSF12A marker were practically absent. In bridging fibrosis, the first peak of TNFRSF12A mRNA growth (p = 0.000) and an increase in the area of TNFRSF12A+ cells (p = 0.000) was established. The second peak (p = 0.000) was detected during the process of transformation of fibrosis into cirrhosis. At the stage of incomplete cirrhosis, a sharp drop was noted. A subsequent increase in the expression of TNFRSF12A mRNA and the area of TNFRSF12A+ cells was observed from the stage of significant cirrhosis. The immunohistochemical method revealed two groups of TNFRSF12A+ cells. In the sinusoidal capillaries TNFRSF12A+, the cells had a shape close to flat and resembled endotheliocytes, while in the fibrous connective tissue they were rounded. The number of α-SMA+ cells increased gradually (p = 0.000) before the onset of significant cirrhosis, and then there was a sharp increase (p = 0.000).