library_construction_protocol: For each sample, cells were mixed with proteinase K (ThermoFisher, E00491) in L1 solution (A&A Biotechnology, 010-50) before incubation at 50°C for 16h with agitation. Then samples were prepared for eccDNA enrichment with column chromatography on an ion exchange membrane column (Plasmid Mini AX; A&A Biotechnology). DNA from uhBMSCs, OBs, CCs and ACs was purified using FastDigest MssI (Thermo Scientifific, ER1341) at 37 °C for 16h and Plasmid-Safe ATP-dependent DNase (E3110K, Plasmid-Safe ATP-dependent DNase, Lucigen) at 37 °C for 1 week. Every 24h, 30 units of ATP and ATP-dependent DNase were added. GenSeq® RCA DNA Amplification Kit was used for phi29 amplification (Genseq Inc., GS-MB-002S) at 30 °C for 46–48h. Library preparation was conducted using GenSeq® Rapid DNA Lib Prep Kit (GenSeq Inc.)