Platelets display potent antimicrobial activity and release human beta-defensin 2

Area of Science:

• Biomedical Engineering
• Infectious Diseases
• Regenerative Medicine

Background:

• Platelet-rich plasma (PRP) is recognized for enhancing soft tissue and bone healing through growth factor release.
• Emerging evidence suggests PRP possesses antimicrobial activity, particularly against Gram-positive bacteria like S. aureus.
• Human beta-defensin-2 (hBD-2) has demonstrated an ideal antibacterial profile for orthopedic infections.

Purpose of the Study:

• To investigate the antimicrobial activity of PRP against a spectrum of clinically relevant bacteria, including Gram-negative strains.
• To determine if human beta-defensin-2 (hBD-2) is the effector molecule responsible for PRP's antimicrobial action.
• To explore the potential of PRP as an adjunct therapy for preventing and treating orthopedic infections.

Main Methods:

• Platelet concentrates were prepared from human platelet apheresis.
• PRP was analyzed for hBD-2 content using immunohistochemistry, Western Blot, and ELISA.
• In vitro antimicrobial susceptibility testing of PRP was performed using a standard disc diffusion assay against various bacterial strains, with and without anti-hBD-2 antibodies.

Main Results:

• PRP was found to contain significant levels of hBD-2 (470 pg/10^9 platelets or 1786 pg/ml).
• PRP demonstrated effective inhibition against Gram-negative bacteria (E. coli, P. aeruginosa, P. mirabilis) and Gram-positive bacteria (B. megaterium, E. faecalis).
• The antimicrobial effect of PRP against E. coli and P. mirabilis was significantly reduced when pre-incubated with anti-hBD-2 antibodies, suggesting hBD-2 mediates this action.

Conclusions:

• This study confirms the antimicrobial efficacy of PRP against a range of clinically relevant bacteria, including important Gram-negative pathogens.
• Human beta-defensin-2 (hBD-2) is identified as a key mediator of PRP's antimicrobial activity, particularly against E. coli and P. mirabilis.
• The findings support the expanded clinical application of PRP as a therapeutic agent with dual roles in promoting healing and combating infections.