ISX-9 Promotes KGF Secretion From MSCs to Alleviate ALI Through NGFR-ERK-TAU-β-Catenin Signaling Axis.

Background: Mesenchymal stem cells (MSCs) have been widely studied to alleviate acute lung injury (ALI) due to their paracrine function. However, the microenvironment of inflammatory outbreaks significantly restricted the factors secreted from MSCs like keratinocyte growth factor (KGF). KGF is a growth factor with tissue-repaired ability. Is there a better therapeutic prospect for MSCs in combination with compounds that promote their paracrine function? Through compound screening, we screened out isoxazole-9 (ISX-9) to promote MSCs derived KGF secretion and investigated the underlying mechanisms of action.

Methods: Compounds that promote KGF secretion were screened by a dual-luciferase reporter gene assay. The TMT isotope labeling quantitative technique was used to detect the differential proteins upon ISX-9 administrated to MSCs. The expressions of NGFR, ERK, TAU, and β-catenin were detected by Western blot. In the ALI model, we measured the inflammatory changes by HE staining, SOD content detection, RT-qPCR, immunofluorescence, etc. The influence of ISX-9 on the residence time of MSCs transplantation was explored by optical in vivo imaging.

Results: We found out that ISX-9 can promote the expression of KGF in MSCs. ISX-9 acted on the membrane receptor protein NGFR, upregulated phosphorylation of downstream signaling proteins ERK and TAU, downregulated phosphorylation of β-catenin, and accelerated β-catenin into the nucleus to further increase the expression of KGF. In the ALI model, combined ISX-9 with MSCs treatments upgraded the expression of KGF in the lung, and enhanced the effect of MSCs in reducing inflammation and repairing lung damage compared with MSCs alone.

Conclusions: ISX-9 facilitated the secretion of KGF from MSCs both in vivo and in vitro. The combination of ISX-9 with MSCs enhanced the paracrine function and anti-inflammatory effect of MSCs compared with MSCs applied alone in ALI. ISX-9 played a contributive role in the transplantation of MSCs for the treatment of ALI.