Figure 2.

Crenolanib treatment improves liver fibrosis regression. Rats received (A,E,I,M,Q) normal (control) or (B,F,J,N,R) TAA-enriched drinking water for 18 weeks to induce liver fibrosis. After fibrosis induction, the rats were either treated with (C,G,K,O,S) DMSO or (D,H,L,P,T) Crenolanib (0.05 mg/mL) dissolved in DMSO for 14 days. Cryosections of liver samples obtained from these rats were subjected to (A–D) Sirius Red and (E–T) immunofluorescence staining, using antibodies against collagen 4 (COL4, red), α-smooth muscle actin (αSMA, green), glial fibrillary acidic protein (GFAP, red), platelet-derived growth factor receptor β (PDGFRβ, red), rat endothelial cell antigen-1 (RECA1, red), glutamine synthetase (GS) (green), and CK19 (green). (D,H,L,P,T) Rats from the Crenolanib-treated group showed weaker Sirius Red staining and decreased levels of COL4, αSMA, PDGFRβ, and CK19 staining. During fibrosis, hepatic stellate cells (HSC) activate and lower GFAP protein levels. The GS is expressed by a small subpopulation of hepatocytes around the central vein in normal liver, showing functional zonation of hepatocytes within the liver tissue. In the Crenolanib-treated group, recurrence of GFAP and GS staining was observed (D,H,L,P,T) compared with the DMSO control animals. (T) GS-expressing hepatocytes were always associated with RECA1-labeled endothelial cells and located near the residues of weakening scars. Cell nuclei were stained by DAPI (blue). Scale bars: 200 µm (A–D); 100 µm (E–T). (U–Z) The areas stained by Sirius red and immunofluorescence on liver sections (A–T) were quantified by computer-assisted methods, which confirmed the accelerated regeneration of the liver observed in the Crenolanib-treated group. The mean values of the control, TAA/Crenolanib, and TAA/DMSO groups represent data from 6 rats per group, whereas the TAA group represents the mean value of data from 4 rats (±SEM; p < 0.05; significant differences are indicated by different letters).