Extracellular vesicles from mesenchymal stem cells improve liver injury in rats with mild liver damage. Underlying mechanisms and role of TGFβ.

Preventing the progression of liver damage to fibrosis would be beneficial for patients with steatotic liver disease (SLD). Mesenchymal stem cells (MSC) are a promising therapy for SLD and derived extracellular vesicles (EVs) could even improve the treatment's efficacy and safety. However, the mechanisms of MSC-EVs beneficial effects are not well known. It has been suggested that modifying the EVs cargo could improve their beneficial effects. The aims of this study were to assess if MSC-EVs reduce liver damage in a rat model of mild liver damage; to analyze the underlying mechanisms and to assess if silencing TGFβ enhances the beneficial effects of MSC-EVs. CCl4 was injected three times per week during four weeks to induce mild liver damage. EVs from human adipocyte MSC and from TGFβ-depleted MSC (siTGFβ-MSC-EVs) were injected in the tail vein. Steatosis, fibrosis, liver inflammation, macrophage infiltration and liver content of fibrotic markers, DAMPs, cytokines and bile acids were analyzed. Normal MSC-EVs reduce the CCL2 increase in liver, macrophage infiltration and the increases in the fibrosis markers collagen I and α-SMA. Treatment with siTGFβ-MSC-EVs, in addition, reduces liver steatosis, the increase of bile acids (mainly TCA), and DAMP HMGB1 levels, inducing a larger reduction of collagen I in liver of CCl4 rats. Treatment with MSCs-EVs effectively reduces early liver damage. Silencing of TGFβ in MSCs enhances the beneficial effects by additional mechanisms. Early treatment with MSC-EVs, especially after silencing TGFβ, could improve liver damage in SLD patients.