Fig. 4

Psoralen restored irradiation-induced suppression of the PI3K/AKT pathway in SSCs. The RNA sequencing data showed that the expression of the osteogenesis-related gene Bmpr1b and the cell proliferation-related gene Gli2 was significantly downregulated in the irradiated SSCs (a). In the psoralen-treated SSCs, the expression of the osteogenesis-related genes Bglap and Bmp8b was remarkably upregulated (a). The gene expression results of RNA sequencing were validated by qPCR (b). The Gene Ontology (GO) analysis results of the irradiation induced the change of gene expression including upregulation of genes responding to oxidative stress and the downregulation of genes related to ossification and mesenchymal cell development, etc., (c) while the psoralen induced the upregulation of genes involved in bone mineralization, ossification, etc. (d). Further KEGG analysis suggested that the PI3K/AKT signaling pathway was closely involved in both irradiation- and psoralen-induced changes in SSC properties (e and f). The results of Western Blotting showed that irradiation significantly inhibited the expression and phosphorylation of AKT in SSCs as well as psoralen promoted the activation of AKT in SSCs while increasing AKT expression and phosphorylation in irradiated SSCs (g and h). All data are shown as the mean ± SD. **P < 0.01, *P < 0.05. SSC: skeletal stem cell; IR: irradiation; and Pso: psoralen