Fig. 5: circCDK13^OE-sEVs promote the proliferation and migration of HDFs and HEKs.

a RT-qPCR analysis of circCDK13 abundance in CP-MSCs transduced with vector or circCDK13 lentivirus (n = 3 biologically independent samples). b Representative TEM photomicrographs of N-sEVs and circCDK13^OE-sEVs. Scale bars, 500 nm. c The size distribution and concentration of N-sEVs and circCDK13^OE-sEVs measured by NTA. d CD63, TSG101, CD9, Alix, and Calnexin were detected by western blot assays in the whole-cell lysate (CP-MSCs) and purified sEVs of CP-MSCs (N-sEVs and circCDK13^OE-sEVs). e RT-qPCR analysis of circCDK13 abundance in N-sEVs and circCDK13^OE-sEVs (n = 3 biologically independent samples). f Absolute qPCR analysis of circCDK13 copy numbers in circCDK13^OE-sEVs after treatments with RNase A/T1 Mix and 1% Triton X-100 for 30 min (n = 3 biologically independent samples). g Internalization of sEVs by HDFs and HEKs. sEVs were marked by the red fluorescence (CM-DiI) and cytoskeleton were marked by green fluorescence (phalloidin). Scale bar, 25 μm. h RT-qPCR analysis of circCDK13 abundance in HDFs and HEKs after co-incubation with N-sEVs or circCDK13^OE-sEVs (sEVs concentration, 2 × 10¹⁰ particles/ml) for 6 h (n = 3 biologically independent samples). i, j Wound healing assay was performed to measure the motility of HDFs and HEKs. Quantification histogram represented migration rate (n = 5 biologically independent samples). Scale bar, 200 μm. k, l Representative images of transwell migration assay of HDFs and HEKs. Quantification histogram represented the number of migrated cells (n = 5 biologically independent samples). Scale bar, 50 μm. m CCK-8 assay was performed after HDFs and HEKs were incubated with N-sEVs or circCDK13^OE-sEVs (sEVs concentration, 2 × 10¹⁰ particles/ml) at the indicated time points (n = 6 biologically independent samples). n EdU incorporation assay was performed to assess DNA synthesis in HDFs and HEKs. Quantification histogram represented EdU positive cell percentage (n = 5 biologically independent samples). Scale bar, 100 μm. o Western blots analysis of IGF2BP3, c-MYC, CD44, and cyclin D1 protein expression levels in HDFs and HEKs of different treatment groups. In (d, g, o) three independent experiments were performed and similar results were obtained. Comparisons were performed by one-way ANOVA followed by Tukey’s multiple comparisons test in (f, h−l, n) and two-tailed Student’s t test in (a, e). Data are presented as mean values ±SD. Source data are provided as a Source Data file.