Preclinical evaluation of a third-generation absorbable antibacterial envelope

Swine models in translational research and medicine

Swine are increasingly studied as animal models of human disease. The anatomy, size, longevity, physiology, immune system, and metabolism of swine are more like humans than traditional rodent models. In addition, the size of swine is preferred for surgical placement and testing of medical devices destined for humans. These features make swine useful for biomedical, pharmacological, and toxicological research. With recent advances in gene-editing technologies, genetic modifications can readily and efficiently be made in swine to study genetic disorders. In addition, gene-edited swine tissues are necessary for studies testing and validating xenotransplantation into humans to meet the critical shortfall of viable organs versus need. Underlying all of these biomedical applications, the knowledge of husbandry, background diseases and lesions, and biosecurity needs are important for productive, efficient, and reproducible research when using swine as a human disease model for basic research, preclinical testing, and translational studies.

Antibacterial mechanism and structure-activity relationships of Bombyx mori cecropin A

Bombyx mori cecropin A (Bmcecropin A) has antibacterial, antiviral, anti-filamentous fungal and tumour cell inhibition activities and is considered a potential succedaneum for antibiotics. We clarified the antibacterial mechanism and structure-activity relationships and then directed the structure-activity optimization of Bmcecropin A. Firstly, we found Bmcecropin A shows a strong binding force and permeability to cell membranes like a detergent; Bmcecropin A could competitively bind to the cell membrane with the cell membrane-specific dye DiI, then damaged the membrane for the access of DiI into the cytoplasm and leading to the leakage of electrolyte and proteins. Secondly, we found Bmcopropin A could also bind to and degrade DNA; furthermore, DNA library polymerase chain reaction (PCR) results indicated that Bmcecropin A inhibited DNA replication by non-specific binding. In addition, we have identified C-terminus amidation and serine-lysine- glycine (SLG) amino acids of Bmcecropin A played critical roles in the membrane damage and DNA degradation. Based on the above results, we designed a mutant of Bmcecropin A (E9 to H, D17 to K, K33 to A), which showed higher antibacterial activity, thermostability and pH stability than ampicillin but no haemolytic activity. Finally, we speculated that Bmcecropin A damaged the cell membrane through a carpet model and drew the schematic diagram of its antibacterial mechanism, based on the antibacterial mechanism and the three-dimensional configuration. These findings yield insights into the mechanism of antimicrobial peptide-pathogen interaction and beneficial for the development of new antibiotics.

Effects of envelopes on cardiac implantable electronic device pocket healing: A head-to-head preclinical evaluation

BACKGROUND

The healing response to cardiac implantable electronic device (CIED) implantation results in inflammation that can lead to fibrous pocket formation, which may disrupt pocket healing or complicate future interventions.

OBJECTIVE

The purpose of this study was to assess CIED pocket healing with use of the second-generation TYRX absorbable antibacterial envelope (T2), the next-generation (NG) TYRX absorbable antibacterial envelope under development, and the CanGaroo® extracellular matrix envelope (ECM) compared to no envelope.

METHODS

A total of 110 CIEDs were implanted in an ovine model, either with (T2, NG, or ECM) or without envelopes. Histopathologic and morphometric analyses were completed at several timepoints after implant (3 days, 7 days, 4 weeks, 12 weeks, 24 weeks). An independent pathologist completed a blinded histopathology assessment of the pockets.

RESULTS

TYRX (T2/NG) pockets showed similar inflammatory and healing profiles to controls with more rapid provisional matrix formation compared to controls and ECM. ECM pockets exhibited increased acute (3 and 7 days) and chronic (24 weeks) inflammation. T2/NG had almost complete (T2) or complete (NG) absorption by week 12. ECM remained present at week 24 and was associated with significantly thicker capsules (ECM 0.80 ± 0.14 mm; NG 0.37 ± 0.10 mm; control 0.56 ± 0.17 mm).

CONCLUSION

Compared to ECM, pockets with TYRX showed less inflammation, more rapid provisional matrix formation, faster absorption, and thinner capsules. TYRX pockets had low inflammation comparable to controls with accelerated provisional matrix deposition and tissue adhesion. The healing response to CIEDs used with TYRX fosters the formation of a well-healed pocket, which may bring patient benefit beyond its proven infection reduction.