Characteristics of PRR-derived exosomes and the proliferation abilities of HMEC-1 and BJ under different activation conditions: a comparative study

[Objective] To compare the characteristics of platelet-rich plasma derived exosomes (PRP-Exos) under different activation conditions and their differential effects on the proliferation capacit of human microvascular endothelial cells (HMEC-1) and human skin fibroblasts (BJ). [Methods] Ten healthy volunteers were recruited, and 10 mL of venous blood anticoagulated with EDTA-K2 was collected. PRP-Exos were prepared and extracted by the secondary centrifugation method. Transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting (WB) detection techniques were used to compare the morphological characteristics, particle size distribution, concentration, and the expression of surface marker proteins of PRP-Exos. Through in vitro cell culture, the differences in morphological changes and proliferation abilities of HMEC-1 and BJ cells induced by PRP-Exos in different activator groups were compared. [Results] 1) TEM observation showed that the morphologies of PRP-Exos in different activator groups were different. 2) NTA analysis showed that compared with the particle size of (109.60±2.71) nm in the normal saline group, the particle sizes of the thrombin group [(104.93±1.55) nm] and the mixed agent group [(103.83±1.58) nm] were relatively smaller, while the particle size of the calcium gluconate group [(113.57±4.70) nm] was larger and its particle size distribution range was wider. There were statistically significant differences among different groups (F=7.019, P<0.05). The concentration of exosomes obtained in the group with the mixture of calcium gluconate and thrombin was the highest [(4.87±0.63)×106 particles/mL, P<0.001]. Both the thrombin group [(2.75±0.13)×106 particles/mL, P < 0.01] and the calcium gluconate group [(3.82±0.06)×106 particles/mL, P<0.001] obtained higher concentrations of exosomes compared with the normal saline group. The concentration in the calcium gluconate group was slightly higher than that in the thrombin group, and there was a significant difference between the two groups (P<0.05). 3) WB analysis showed that CD41, CD81, and TSG101 were expressed on the surface of PRP-Exos, and the protein signal intensities of CD41 and TSG101 in the group with the mixture of thrombin and calcium gluconate were the strongest (P<0.001). 4) The results of in vitro cell culture showed that PRP-Exos in the group with the mixture of thrombin and calcium gluconate could significantly promote the proliferation of HMEC-1 and BJ cells (P<0.05). [Conclusion] The PRP treated with the thrombin and calcium gluconate mixture group yielded the highest concentration of exosomes; under in vitro culture conditions, PRP-Exos from this group significantly promoted the proliferation of HMEC-1 and BJ cells.