Penicillin and streptomycin

iMPMECs were generated in our laboratory [34 (link)]. The cells were used at passages 3–10, and maintained in DMEM-F12 (Gibco, USA) supplemented with 5% foetal bovine serum (FBS) (ExCell, China), 1% penicillin and streptomycin (Gibco, USA), 1% endothelial cell growth supplement (ECGS) (ScienCell, USA), 100 IU/ml heparin (Solarbio, China), and 92 mg/L D-valine (Sigma, USA) and incubated at 37 °C in 5% CO₂. The cells were grown to 70–80% confluence, washed 3 times with PBS, and treated with or without 1 µg/ml LPS (Sigma, USA) for 24 h in conditioned culture medium (CCM) containing exosome-depleted FBS. CCM was collected after 24 h. Exosome-depleted FBS was prepared by centrifuging FBS for at least 18 h overnight at 100,000 × g at 4 °C, after which the centrifuged FBS were passed through a 0.22 μm filter (Millipore, USA). MSCs derived from the bone marrow of C57BL/6 mice (Cyagen Biosciences, China) were used at passages 3–8 and cultured in DMEM-F12 supplemented with 10% FBS and 1% penicillin and streptomycin, and these cells were tested for their osteogenic, adipogenic, and chondrogenic differentiation potentials to ensure they met the characteristic of stem cells (Supplementary Fig. S1).