The significance of HBD-3 and fluorescent composite carriers in the processof bone formation in rats infected with Staphylococcus aureus.

The objective of the present study was to explore the significance of human β-defensin 3 (HBD-3) through establishment and evaluation of the model of implant-related biofilm infection of the femoral condyle of the outer knee using Sprague-Dawley (SD) rats.Age-matched SD rats were divided into three groups, the HBD-3 group, HBD-3 fluorescent liposome group, and the HBD-3 liposome-microbubble fluorescent composite carrier group. After biofilm infection for 24 h, the fluorescent composite vector was injected intraperitoneally 2 times/day. After the first injection, rats in each group were sacrificed on the 7th, 14th, and 28th day. The lower end of the femur bone was harvested after removing the surrounding soft tissue. H&E and immunohistochemical staining were applied and light microscopy was used for observation. Fluorescent markers including tetracycline and calcein were used to follow the formation of new bone in vivo. Undecalcified specimens were embedded in epoxy resin (thickness of roughly 150 m), and confocal microscopy was used for observation.By assessing cell proliferation with cell counting kit-8, the proliferation ability of cells in the HBD-3 liposome-microbubble fluorescent composite carrier group was significantly increased compared with the other groups (p<0.05). qPCR was used to measure the levels of alkaline phosphatase (ALP), type I collagen, osteocalcin (OCN), osteopontin (OPN), and bone sialoprotein (BSP) in each group. The levels of these genes in the HBD-3 liposome-microbubble fluorescent composite carrier group were significantly higher than those in other groups (p<0.05).The application of the HBD-3 liposome-microbubble fluorescent composite carrier can significantly promote osteogenesis in rats infected with Staphylococcus aureus, and increase the expression levels of ALP, type I collagen, OCN, OPN, and BSP.