Heat treatment of EPC-CM was performed in order to denature the proteinaceous components of EPC-CM. Briefly, 15-ml polypropylene test tubes (BD Falcon, Allschwil, Switzerland) containing 6 ml of medium were immersed in boiling distilled water for 10 min, and then the tubes were transferred to ice-cold water for 5 min.
For the protease treatment, the medium was incubated with proteinase K immobilized on agarose beads (Sigma-Aldrich) as described by others with minor modifications (48) . Briefly, 3 ml of the medium was incubated with agarose-proteinase K (5 U) in 15-ml polypropylene test tubes (BD Falcon, Allschwil, Switzerland) for 4 h at 37°C in a rotating roller drum. Thereafter, the tubes were centrifuged for 5 min at 780 × g to pellet the agarose-proteinase K, and the proteinase K-free supernatant was carefully collected and used for subsequent experiments.
Removal of lipid components from EPC-CM was performed by chloroform extraction (56) . Briefly, equal volumes (6 ml) of EPC-CM and chloroform were mixed and centrifuged for 5 min at 1,750 × g, the aqueous phase was collected, and the procedure was repeated. Finally, the medium was transferred into an open 1-cm Petri dish, and the traces of chloroform were left to evaporate in the sterile hood for 10 min. Thereafter, the water lost during evaporation was reconstituted with distilled sterile water.
For the protease treatment, the medium was incubated with proteinase K immobilized on agarose beads (Sigma-Aldrich) as described by others with minor modifications (48) . Briefly, 3 ml of the medium was incubated with agarose-proteinase K (5 U) in 15-ml polypropylene test tubes (BD Falcon, Allschwil, Switzerland) for 4 h at 37°C in a rotating roller drum. Thereafter, the tubes were centrifuged for 5 min at 780 × g to pellet the agarose-proteinase K, and the proteinase K-free supernatant was carefully collected and used for subsequent experiments.
Removal of lipid components from EPC-CM was performed by chloroform extraction (56) . Briefly, equal volumes (6 ml) of EPC-CM and chloroform were mixed and centrifuged for 5 min at 1,750 × g, the aqueous phase was collected, and the procedure was repeated. Finally, the medium was transferred into an open 1-cm Petri dish, and the traces of chloroform were left to evaporate in the sterile hood for 10 min. Thereafter, the water lost during evaporation was reconstituted with distilled sterile water.