Melatonin-treated bone marrow mesenchymal stem cell-derived exosomes reverse liver fibrosis induced by CCl4 in male wistar albino rats.

Liver fibrosis is defined as the substitution of hepatocytes with extracellular matrix (ECM) proteins, accompanied by abnormalities in matrix remodelling. We aimed to assess the efficacy of melatonin-pretreated bone marrow mesenchymal stem cell-derived exosomes (MT/Exos) in mitigating liver fibrosis. MT/Exos were isolated from their parent cells and characterised by measuring protein content, particle size, and cluster of differentiation (CD) markers. In vivo studies (MT/Exos (100 µg/rat) via the caudal vein twice weekly for 4 weeks) include assessment of liver biomarkers, oxidative stress markers, inflammatory cytokines, apoptotic markers, fibrotic cytokines, and histopathological changes. MT/Exos with 1 mg/ml protein showed double-membrane vesicles sized 50-100 nm, and expressed CD63 and CD81 markers. Treated rats showed restoration of albumin levels, significant improvements in liver enzymes, notable elevations in SOD activity and Nrf2 levels, and a marked reduction in MDA levels. TNF-α, IL-17, NF-κB-p50, and p65 levels were attenuated, and IL-10 levels increased significantly. p53, Bax, caspase-3, TGF-β, SMAD3, collagen I, and miRNA 196 also showed a substantial decrease in treated rats (P < 0.05). Histopathological examination confirmed a marked reduction of collagen deposition and inflammatory infiltration. MT/Exos were successfully isolated and characterized. The MT/Exos-treated group showed improvements in all liver function parameters, with increased levels of antioxidant and anti-inflammatory markers. MT/Exos reduced apoptotic and fibrotic modulators and improved histopathological features. These findings confirm the synergistic effect of melatonin preconditioning in improving the therapeutic potential of MSC-derived exosomes as a novel anti-fibrotic agent. Overall, MT/Exos may offer a promising therapeutic approach for liver fibrosis with potential clinical relevance pending further studies.