title: Anti-bacterial effects of poly-N-acetyl-glucosamine nanofibers in cutaneous wound healing: requirement for Akt1.
abstract: BACKGROUND
  Treatment of cutaneous wounds with poly-N-acetyl-glucosamine nanofibers (sNAG) results in increased kinetics of wound closure in diabetic animal models, which is due in part to increased expression of several cytokines, growth factors, and innate immune activation. Defensins are also important for wound healing and anti-microbial activities. Therefore, we tested whether sNAG nanofibers induce defensin expression resulting in bacterial clearance.
  
  
  METHODS
  The role of sNAG in defensin expression was examined using immunofluoresence microscopy, pharmacological inhibition, and shRNA knockdown in vitro. The ability of sNAG treatment to induce defensin expression and bacterial clearance in WT and AKT1-/- mice was carried out using immunofluoresent microscopy and tissue gram staining. Neutralization, using an antibody directed against β-defensin 3, was utilized to determine if the antimicrobial properties of sNAG are dependent on the induction of defensin expression.
  
  
  CONCLUSIONS
  sNAG treatment causes increased expression of both α- and β-type defensins in endothelial cells and β-type defensins in keratinocytes. Pharmacological inhibition and shRNA knockdown implicates Akt1 in sNAG-dependent defensin expression in vitro, an activity also shown in an in vivo wound healing model. Importantly, sNAG treatment results in increased kinetics of wound closure in wild type animals. sNAG treatment decreases bacterial infection of cutaneous wounds infected with Staphylococcus aureus in wild type control animals but not in similarly treated Akt1 null animals. Furthermore, sNAG treatment of S. aureus infected wounds show an increased expression of β-defensin 3 which is required for sNAG-dependent bacterial clearance. Our findings suggest that Akt1 is involved in the regulation of defensin expression and the innate immune response important for bacterial clearance. Moreover, these findings support the use of sNAG nanofibers as a novel method for enhancing wound closure while simultaneously decreasing wound infection.
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Haley Buff
authors.initials: HB
authors.lastname: Lindner
authors.forename: Aiguo
authors.initials: A
authors.lastname: Zhang
authors.forename: Juanita
authors.initials: J
authors.lastname: Eldridge
authors.forename: Marina
authors.initials: M
authors.lastname: Demcheva
authors.forename: Philip
authors.initials: P
authors.lastname: Tsichlis
authors.forename: Philip
authors.initials: P
authors.lastname: Tsichilis
authors.forename: Arun
authors.initials: A
authors.lastname: Seth
authors.forename: John
authors.initials: J
authors.lastname: Vournakis
authors.forename: Robin C
authors.initials: RC
authors.lastname: Muise-Helmericks
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry*; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology; D015603:Keratinocytes / Q000166:cytology; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence / Q000379:methods; D057139:Nanofibers / Q000737:chemistry*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D014945:Wound Healing; D023083:beta-Defensins / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D016207:Cytokines; D034741:RNA, Small Interfering; D023083:beta-Defensins; C113831:poly-N-acetyl glucosamine; D051057:Proto-Oncogene Proteins c-akt; D000117:Acetylglucosamine