Abstract: Objective To investigate the time-effect relationship of hyperbaric oxygen(HBO) exposure on platelet rich fibrin(PRF) to secreting platelet endothelial cell adhesion molecule-1(PECAM-1) and vascular endothelial growth factor(VEGF). Methods A total of 28 volunteers were randomly divided into 4 groups (n=7):HBO 1 group(exposed to 0.25 MPa HBO for 10 min), HBO 2 group (exposed to 0.25 MPa HBO for 30 min),HBO 3 group(exposed to 0.25 MPa HBO for 60 min) and the control group (air exposure for 60 min). PRF in each group was fixed with 4% paraformaldehyde respectively. PECAM-1 and VEGF positive staining were qualitatively and quantitatively determined by immunohistochemical staining and micro-spectrophotometer. The ultra-structural changes of PRF were observed by transmission electron microscope(TEM). Results In control group, PECAM-1 and VEGF staining were positive in PRF. The positive degrees of PECAM-1 and VEGF staining in PRF in HBO 1 group,HBO 2 group and HBO 3 group were higher than that in control group. The positive staining was mainly located in the upper part of white blood cell, and spread to the fiber end after the exposure of HBO. Quantitative determination showed that the contents of PECAM-1 and VEGF in the HBO exposed group were significantly different from those in the control group. The secretory contents of PECAM-1 and VEGF in HBO 2 group and HBO 3 groups were significantly higher than those in HBO 1 group. The platelet granule release in HBO 1 group, HBO 2 group and HBO 3 group was significantly higher than that in control group. The secreted platelet granules were located in the cells or collagenous fibers. Little apoptosis of leukocytes was observed in HBO 3 group. Conclusion HBO exposure to PRF significantly promotes the secretion of PECAM-1 and VEGF.

Key words: Hyperbaric oxygen, platelet rich fibrin, PECAM-1, VEGF, time-effect relationship