Interactions of neutrophils with silver-coated vascular polyester grafts.

BACKGROUND: In reconstructive vascular surgery, infection is one of the most feared complications because of the high mortality. While the antimicrobial effect of a silver-coated endoprosthesis has been proven in experimental trials, there are no reports on its interactions with granulocytes, the first effector cells in general inflammation and in infection. MATERIALS AND METHODS: Therefore, we investigated whether silver coating of vascular polyester grafts affects receptor expression, mediator release, and functions of human neutrophils relevant for microbicidal activity and the wound-healing process. Naïve neutrophils were analyzed for their cellular receptors such as cluster of differentiation (CD)62L, CD11b, CXCR2, and fMLP-R, the mediators interleukin 8, granulocyte elastase (human neutrophil elastase), and leukotriene B4 (LTB4) as well as for microbicidal capacity (oxidative burst) in vitro. In addition, the role of plasma coating for receptor expression was addressed. RESULTS: There was both a decrease of CD62L and CXCR2 expression and an increase of CD11b, fMLP-R expression, elastase release, and LTB4 generation, which were statistically significant (p = 0.04; p = 0.01; p = 0.0; p = 0.0; p = 0.01; p = 0.02, respectively) in the presence of the silver-coated graft compared with non-silver-coated vascular grafts. In addition, microbicidal activity was significantly (p = 0.0) impaired by the silver-coated graft. Coating of the vascular grafts with plasma did not alter the former observations significantly. CONCLUSION: The results may indicate that silver-coated vascular polyester grafts activate neutrophils chronically which may favor tissue destruction and impaired antimicrobial effects.

The influence of polymorbidity, revascularization, and wound therapy on the healing of arterial ulceration.

OBJECTIVE: An ulcer categorized as Fontaine's stage IV represents a chronic wound, risk factor of arteriosclerosis, and co-morbidities which disturb wound healing. Our objective was to analyze wound healing and to assess potential factors affecting the healing process. METHODS: 199 patients were included in this 5-year study. The significance levels were determined by chi-squared and log-rank tests. The calculation of patency rate followed the Kaplan-Meier method. RESULTS: Mean age and co-morbidities did not differ from those in current epidemiological studies. Of the patients with ulcer latency of more than 13 weeks (up to one year), 40% required vascular surgery. Vascular surgery was not possible for 53 patients and they were treated conservatively. The amputation rate in the conservatively treated group was 37%, whereas in the revascularizated group it was only 16%. Ulcers in patients with revascularization healed in 92% of cases after 24 weeks. In contrast, we found a healing rate of only 40% in the conservatively treated group (p<0.001). Revascularization appeared more often in diabetic patients (n=110; p<0.01) and the wound size and number of infections were elevated (p=0.03). Among those treated conservatively, wound healing was decelerated (p=0.01/0.02; chi(2) test). CONCLUSIONS: The success of revascularization, presence of diabetes mellitus, and wound treatment proved to be prognostic factors for wound healing in arterial ulcers.

Long term study of deoxyribozyme administration to XT-1 mRNA promotes corticospinal tract regeneration and improves behavioral outcome after spinal cord injury.

Spinal cord injury (SCI) affects approximately 3 million people around the world, who are desperately awaiting treatment. The pressing need for the development of therapeutics has spurred medical research for decades. To respond to this pressing need, our group developed a potential therapeutic to reduce the presence of proteoglycans at the injury site after acutely traumatizing the spinal cord of rats. With the aid of a DNA enzyme against the mRNA of xylosyltransferase-1 (DNAXT-1as) we adjourn the glycosylation and prevent the assembly of the proteoglycan core protein into the extracellular matrix. Hence, endogenous repair is strengthened due to the allocation of a more growth permissive environment around the lesion site. Here, we present data on a long term study of animals with a dorsal hemisection treated with DNAXT-1as, DNAXT-1mb (control DNA enzyme) or PBS via osmotic minipumps. After successful digestion of the XT-1 mRNA shown by qPCR we observed an overall behavioral improvement of DNAXT-1as treated rats at 8, 10 and 14 weeks after insult to the spine compared to the control animals. This is accompanied by the growth of the cortical spinal tract (CST) in DNAXT-1as treated animals after a 19 week survival period. Furthermore, after evaluating the lesion size tissue-protective effects in the DNAXT-1as treated animals compared to DNAXT-1mb and PBS treated rats are revealed. The results yield new insights into the regeneration processes and provide confirmation to involve DNA enzyme administration in future therapeutic strategies to medicate SCI.

Strategies for inducing the formation of bands of Büngner in peripheral nerve regeneration.

Peripheral human nerves fail to regenerate across longer tube implants (>2 cm), most likely because implants lack the microarchitecture of native nerves, including bands of Büngner. Bands of Büngner comprise longitudinally aligned Schwann cell strands that guide selectively regrowing axons. We aim to optimize tubular implants by integrating artificial bands of Büngner. Three principle strategies for inducing the formation of bands of Büngner were investigated: (a) an aligned extracellular matrix, (b) polarizing differentiation factors, and (c) microstructured biomaterial filaments. In vitro oriented collagen and a combination of differentiation factors (NGF, neuregulin-1, TGF-beta) induced Schwann cell alignment to some extent. The most pronounced Schwann cell alignment was evident on ultrathin, endless poly-epsilon-caprolactone (PCL) filaments with longitudinal microgrooves. Precoated PCL filaments proved to be non-cytotoxic, displayed good cell attachment, and supported Schwann cell proliferation as well as guided axonal outgrowth. In vitro on PCL filaments Schwann cells displayed a polarized expression of the cell adhesion molecule L1 similar to that seen in vivo in bands of Büngner after sciatic nerve crush in adult rats. In summary, the integration of bioengineered bands of Büngner based on microstructured polymer filaments in nerve conduits promises to be the most valuable approach to initiating a more efficient regeneration across longer nerve lesions.

Protein synthesis inhibiting clindamycin improves outcome in a mouse model of Staphylococcus aureus sepsis compared with the cell wall active ceftriaxone.

OBJECTIVE: The release of proinflammatory components from bacteria depends on the mode of action of the antibacterial therapy used. We studied whether this influences mortality in experimental sepsis. DESIGN: In a lethal murine model of Staphylococcus aureus sepsis, animals were randomly assigned to receive the protein synthesis inhibitor clindamycin (CLI) or the beta-lactam ceftriaxone (CRO). SETTING: Therapy was introduced subcutaneously 5 hrs after intraperitoneal injection of 10 colony forming units of S. aureus American Type Culture Collection 29213 and was continued every 8 hrs for 3 days. MEASUREMENTS AND RESULTS: Survival was higher in mice receiving CLI (29/50 animals [58%]) than in mice receiving CRO (16/50 animals [32%]; p =.015). Mice treated with CRO died earlier than mice receiving CLI (p =.002). Eight hours after the first antibiotic dose, the motor performance of mice receiving CRO had deteriorated more than it did for mice receiving CLI (p =.009). Higher levels of tumor necrosis factor-alpha were measured in serum (p =.027) and peritoneal fluid (p =.001) of CRO-treated mice. In vitro, CLI released smaller amounts of staphylococcal enterotoxin A than CRO. CONCLUSIONS: Antibiotic treatment of Gram-positive sepsis with a protein synthesis inhibitor decreases morbidity and mortality compared with a bacteriolytic compound. This may be caused by a reduction of the concentrations of proinflammatory/toxic bacterial components and cytokines.