Platelet‐leukocyte gel (PLG) contains high concentrations of platelets and leukocytes. As leukocytes play an important role in the innate host‐defense, we hypothesized that PLG might have antimicrobial properties. This study investigated the antimicrobial activity of PLG against Staphylococcus aureus and the contribution of myeloperoxidase (MPO), present in leukocytes, in this process. Platelet‐rich plasma (PRP) and platelet‐poor plasma (PPP) were obtained from whole blood of six donors. PLG was prepared by mixing PRP with autologous (PLG‐AT) or bovine thrombin (PLG‐BT). Antimicrobial activity of PLG‐AT, PLG‐BT, PRP, and PPP was determined in a bacterial kill assay. MPO release was measured by ELISA and activity was measured using a MPO activity assay. Cultures showed a rapid decrease in the number of bacteria for both PLG‐AT and PLG‐BT, which was maximal between 4 and 8 h, to approximately 1% of the bacteria in controls. The effect of PLG‐AT was largest and significantly different compared to PRP (p = 0.004) and PPP (p < 0.001), however not compared to PLG‐BT (p = 0.093). PLG‐AT, PLG‐BT, and PRP showed a comparable, gradually increasing MPO release. MPO activity was comparable for all groups and remained stable. No correlation between MPO release, activity, and bacterial kill could be found. PLG appears to have potent antimicrobial capacity, but the role of MPO in this activity is questionable. PLG might represent a useful strategy against postoperative infections. However, additional research should elucidate its exact antimicrobial activity. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:404–410, 2008

Prospective observational and analytic study. To investigate whether spontaneous intervertebral disc degeneration (IVDD) occurring in both chondrodystrophic (CD) and nonchondrodystrophic dogs (NCD) can be used as a valid translational model for human IVDD research. Different animal models are used in IVDD research, but in most of these models IVDD is induced manually or chemically rather than occurring spontaneously. A total of 184 intervertebral discs (IVDs) from 19 dogs of different breeds were used. The extent of IVDD was evaluated by macroscopic grading, histopathology, glycosaminoglycan content, and matrix metalloproteinase 2 activity. Canine data were compared with human IVD data acquired in this study or from the literature. Gross pathology of IVDD in both dog types (CD and NCD) and humans showed many similarities, but the cartilaginous endplates were significantly thicker and the subchondral cortices significantly thinner in humans than in dogs. Notochordal cells were still present in the IVDs of adult NCD but were not seen in the CD breeds or in humans. Signs of degeneration were seen in young dogs of CD breeds (<1 year of age), whereas this was only seen in older dogs of NCD breeds (5–7 years of age). The relative glycosaminoglycan content and metalloproteinase 2 activity in canine IVDD were similar to those in humans: metalloproteinase 2 activity increased and glycosaminoglycan content decreased with increasing severity of IVDD. IVDD is similar in humans and dogs. Both CD and NCD breeds may therefore serve as models of spontaneous IVDD for human research. However, as with all animal models, it is important to recognize interspecies differences and, indeed, the intraspecies differences between CD and NCD breeds (early vs. late onset of IVDD, respectively) to develop an optimal canine model of human IVDD.