CXCL12 and infection: To identify the core DEGs generated by the SDF-1 and EX-4 combined application, STEM software was applied to perform a pattern analysis (mock infection was designated NC), and the results revealed 49 gene clusters among all DEGs generated by SDF-1, EX-4 and SDF-1+EX-4-treated PDLSCs (Fig. S4 and Table S5).