Unmodified MSCs, CMV-PDGF-BB-MSCs, and PGK-PDGF-BB-MSCs were cultured in GM and seeded at a density of 2 × 104 cells/well onto 24-well plates. The samples, which included the supernatant and cells, were collected at one, three, and seven days. For the samples collected at seven days, GM was replaced with fresh GM at three days. After collecting the supernatants, each plate was then washed three times with PBS and 1 mL of DNase/RNase free water was subsequently added into each well. Cellular DNA was released by three freeze–thaw cycles and the quantity of dsDNA in each well was measured by performing a Quant-iT PicoGreen dsDNA Assay (Invitrogen, Carlsbad, CA) according to the manufacturer’s instructions. Fluorescence was measured at 480/520 nm wavelength using a plate reader (SpectraMax M2e Microplate Reader, Molecular Devices, San Jose, CA), and the amount of dsDNA was calculated.
To verify expression of PDGF-BB, the supernatant at three and seven days was analyzed. The concentration of PDGF-BB was measured using a human PDGF-BB ELISA kit (R&D Systems, Minneapolis, MN) according to the manufacturer’s instructions. Optical absorbance at 450 nm was measured using a plate reader and PDGF-BB expression level was calculated.
To verify expression of PDGF-BB, the supernatant at three and seven days was analyzed. The concentration of PDGF-BB was measured using a human PDGF-BB ELISA kit (R&D Systems, Minneapolis, MN) according to the manufacturer’s instructions. Optical absorbance at 450 nm was measured using a plate reader and PDGF-BB expression level was calculated.