Ex Vivo Murine Skin Model for B. burgdorferi Biofilm

Evidence for the Presence of Borrelia burgdorferi Biofilm in Infected Mouse Heart Tissues

Borrelia burgdorferi, the bacterium responsible for Lyme disease, has been shown to form antimicrobial-tolerant biofilms, which protect it from unfavorable conditions. Bacterial biofilms are known to significantly contribute to severe inflammation, such as carditis, a common manifestation of Lyme disease. However, the role of B. burgdorferi biofilms in the development of Lyme carditis has not been thoroughly investigated due to the absence of an appropriate model system. In this study, we examined heart tissues from mice infected with B. burgdorferi for the presence of biofilms and inflammatory markers using immunohistochemistry (IHC), combined fluorescence in situ hybridization FISH/IHC, 3D microscopy, and atomic force microscopy techniques. Our results reveal that B. burgdorferi spirochetes form aggregates with a known biofilm marker (alginate) in mouse heart tissues. Furthermore, these biofilms induce inflammation, as indicated by elevated levels of murine C-reactive protein near the biofilms. This research provides evidence that B. burgdorferi can form biofilms in mouse heart tissue and trigger inflammatory processes, suggesting that the mouse model is a valuable tool for future studies on B. burgdorferi biofilms.

3D Approaches to Culturing Bovine Skin: Explant Culture versus Organotypic Skin Model

INTRODUCTION

Digital dermatitis (DD) in cattle appears with high prevalence; nevertheless, the knowledge on its pathogenesis is still limited. In this context, in vitro skin models represent a valuable tool to facilitate the study of DD.

METHODS

Two in vitro skin models were established using bovine distal limb skin: a skin explant model and an organotypic skin model. For the skin explant model, skin samples were cultured with an air-liquid interface for up to 7 days. Besides routine histopathological examination, readout parameters were Ki-67 and cleaved Caspase-3 stainings. For the organotypic model, primary keratinocytes were layered on top of a dermal equivalent containing mainly mitotically inactive fibroblasts and maintained for up to 21 days. At regular intervals (days 7, 14, and 21), cultured skin samples were taken for (immuno)histological analysis.

RESULTS

Both cultures could be maintained for the entire duration of the intended culture period. In the histopathological assessment, explant skin cultures showed ballooning degeneration of keratinocytes and segmental necrosis starting at day 5 of culturing. Initially, basal keratinocytes in the organotypic model differentiated as demonstrated by positive Keratin 14, Desmoglein-1, Loricrin, and Involucrin immunofluorescent stainings. Ki-67 was observed occasionally and suprabasally still after 21 days of culture.

CONCLUSION

Both in vitro models proved dependable and constitute a viable option for replacing experiments on live animals, each with its own benefits. Whereas skin explants include all cell types available in vivo and can therefore reflect realistic cell-cell interactions and signaling pathways, the organotypic model offers a higher standardization and reproducibility. Depending on the focus of future studies, both models can be used for specific experimental purposes of bovine dermatological research in general or specialized questions concerning (infectious) claw diseases as, e.g., DD.

Establishing a Zebrafish Model for Borrelia burgdorferi Infection Using Immersion and Microinjection Methods

Borrelia burgdorferi is the spirochetal bacterium that causes Lyme disease. Even though antimicrobial sensitivity of B. burgdorferi has been widely studied, there is still a need to develop an affordable, practical, high-throughput in vivo model which can be used to find effective antibiotic therapies, especially for the recently discovered persister and biofilm forms. Here, we describe the immersion and microinjection methods to introduce B. burgdorferi spirochetes into zebrafish larvae. The B. burgdorferi-zebrafish model can be produced by immersing 5-day post-fertilization (dpf) zebrafish in a B. burgdorferi culture, or by injecting B. burgdorferi into the hindbrain of zebrafish at 28 h post-fertilization (hpf). To demonstrate that B. burgdorferi indeed infect the fish, nested polymerase chain reaction (PCR), reverse transcription PCR (RT-PCR), live fluorescence imaging, histological staining, and wholemount immunohistochemical (IHC) methods can be used on B. burgdorferi-infected zebrafish.

Pathogenicity and virulence of Borrelia burgdorferi

Infection with Borrelia burgdorferi often triggers pathophysiologic perturbations that are further augmented by the inflammatory responses of the host, resulting in the severe clinical conditions of Lyme disease. While our apprehension of the spatial and temporal integration of the virulence determinants during the enzootic cycle of B. burgdorferi is constantly being improved, there is still much to be discovered. Many of the novel virulence strategies discussed in this review are undetermined. Lyme disease spirochaetes must surmount numerous molecular and mechanical obstacles in order to establish a disseminated infection in a vertebrate host. These barriers include borrelial relocation from the midgut of the feeding tick to its body cavity and further to the salivary glands, deposition to the skin, haematogenous dissemination, extravasation from blood circulation system, evasion of the host immune responses, localization to protective niches, and establishment of local as well as distal infection in multiple tissues and organs. Here, the various well-defined but also possible novel strategies and virulence mechanisms used by B. burgdorferi to evade obstacles laid out by the tick vector and usually the mammalian host during colonization and infection are reviewed.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Systems of conductive skin for power transfer in clinical applications

The primary aim of this article is to review the clinical challenges related to the supply of power in implanted left ventricular assist devices (LVADs) by means of transcutaneous drivelines. In effect of that, we present the preventive measures and post-operative protocols that are regularly employed to address the leading problem of driveline infections. Due to the lack of reliable wireless solutions for power transfer in LVADs, the development of new driveline configurations remains at the forefront of different strategies that aim to power LVADs in a less destructive manner. To this end, skin damage and breach formation around transcutaneous LVAD drivelines represent key challenges before improving the current standard of care. For this reason, we assess recent strategies on the surface functionalization of LVAD drivelines, which aim to limit the incidence of driveline infection by directing the responses of the skin tissue. Moreover, we propose a class of power transfer systems that could leverage the ability of skin tissue to effectively heal short diameter wounds. In this direction, we employed a novel method to generate thin conductive wires of controllable surface topography with the potential to minimize skin disruption and eliminate the problem of driveline infections. Our initial results suggest the viability of the small diameter wires for the investigation of new power transfer systems for LVADs. Overall, this review uniquely compiles a diverse number of topics with the aim to instigate new research ventures on the design of power transfer systems for IMDs, and specifically LVADs.