Substance P alleviates liver fibrosis by modulating inflammation and mobilizing reparative stem cells.

Repetitive hepatic damage resulting from viral hepatitis, toxins, and alcohol abuse induces chronic inflammation and excessive accumulation of the extracellular matrix, leading to the development of liver cirrhosis. Substance P (SP) promotes endogenous wound healing by mobilizing bone marrow stem cells and stimulating anti-inflammatory responses. This study aimed to investigate whether SP exerts a therapeutic effect on liver fibrosis by recruiting endogenous stem cells and modulating immune responses. A non-clinical model of liver cirrhosis was established through repeated injections of thioacetamide and recombinant leptin. After confirming liver fibrosis, SP was administered intravenously for 6 weeks. SP treatment decreased the formation of hepatic micronodules on the external surface of the liver and the infiltration of immune cells. Furthermore, SP treatment notably reduced the deposition of collagen and the activation of hepatic stellate cells, concomitant with decreased levels of transforming growth factor-β1 and matrix metalloproteinase activity. In the context of severe hepatic damage, SP increased the number of circulating stem cells, leading to the restoration of the reparative stem cell pool in the bone marrow. The findings of this study suggest that SP alleviates liver fibrosis by modulating the mobilization of functional stem cells and the immune response.