Background
Urethral stricture is a clinical challenge for both patients and clinicians. Post-traumatic urethral stricture is associated with formation of scar tissue caused by excessive inflammation. The
Conclusion
These results support a role for let-7c-containing Exo-MSCsIL-1β in reducing urethral stricture via inhibition of PAK1-NF-κB signaling, M2 macrophage polarization, and differentiation of urethral myofibroblasts.
Methods
In vivo experiments on New Zealand rabbits and in vitro experiments on THP-1 monocytes and urethral fibroblasts were performed to investigate the effects on post-traumatic urethral stricture of exosomes isolated from IL-1β-treated mesenchymal stem cells (Exo-MSCsIL-1β) and the role of macrophage M2 polarization in this process. Additionally, related signaling and mechanism behind were explored.
Results
In a New Zealand rabbit model of post-traumatic urethral stricture, injection of Exo-MSCsIL-1β significantly reduced urethral stricture and collagen fiber accumulation compared with Exo-MSCs. Addition of Exo-MSCsIL-1β to THP-1 monocytes in vitro induced M2 macrophage polarization, which, in turn, inhibited activation of urethral fibroblasts and synthesis of collagen. Mechanistically, Exo-MSCsIL-1β were found to contain high levels of the microRNA let-7c, and luciferase reporter assays showed that let-7c interacted with the 3'UTR of PAK1 mRNA. Transfection of THP-1 cells with a let-7c mimic downregulated PAK1 expression and inhibited activation of the NF-κB signaling pathway.