Bacterial chatter in chronic wound infections.

One of the hallmark characteristics of chronic diabetic wounds is the presence of biofilm-forming bacteria. Bacteria encapsulated in a biofilm may coexist as a polymicrobial community and communicate with each other through a phenomenon termed quorum sensing (QS). Here, we describe the QS circuits of bacterial species commonly found in chronic diabetic wounds. QS relies on diffusion of signaling molecules and the local concentration changes of these molecules that bacteria experience in wounds. These biochemical signaling pathways play a role not only in biofilm formation and virulence but also in wound healing. They are, therefore, key to understanding the distinctive nature of these infections. While several in vivo and in vitro models exist to study QS in wounds, there has been limited progress in understanding the interplay between QS molecules and host factors that contribute to wound healing. Lastly, we examine the potential of targeting QS for both diagnosis and therapeutic intervention purposes.

Treating Polymicrobial Infections in Chronic Diabetic Wounds.

This review provides a comprehensive summary of issues associated with treating polyclonal bacterial biofilms in chronic diabetic wounds. We use this as a foundation and discuss the alternatives to conventional antibiotics and the emerging need for suitable drug delivery systems. In recent years, extraordinary advances have been made in the field of nanoparticle synthesis and packaging. However, these systems have not been incorporated into the clinic for treatments other than for cancer or severe genetic diseases. We present a unifying perspective on how the field is evolving and the need for an early amalgamation of engineering principles and a biological understanding of underlying phenomena in order to develop a therapy that is translatable to the clinic in a shorter time.

Real-Time Monitoring of Urinary Encrustation Using a Quartz Crystal Microbalance.

Encrustation on the surface of urological devices such as ureteral stents leads to their blockage. However, limited tools are available for fast and real-time monitoring and modeling of the encrustation process. In this work, we have developed a model for in vitro study of encrustation and coupled it to an online monitoring QCM technique. The QCM biosensor is precoated with a polymer that is representative of the surface of a ureteral stent and subsequently coated with urease to facilitate crystallization of calcium and magnesium phosphate. The changes in deposition of crystals on the polymer surface are monitored quantitatively using a quartz crystal microbalance (QCM) biosensor. The QCM sensor is capable of dynamic, label-free detection and has a very high sensitivity. Experimental data generated using this model shows that pretreatment of the sensor surface with urease significantly induces early stage encrustation as compared to the untreated sensor surface, which emulates the real encrustation process. This encrustation study model has a high utility in screening studies for materials used in urological devices.

Actin cytoskeleton rest stops regulate anterograde traffic of connexin 43 vesicles to the plasma membrane.

RATIONALE: The intracellular trafficking of connexin 43 (Cx43) hemichannels presents opportunities to regulate cardiomyocyte gap junction coupling. Although it is known that Cx43 hemichannels are transported along microtubules to the plasma membrane, the role of actin in Cx43 forward trafficking is unknown. OBJECTIVE: We explored whether the actin cytoskeleton is involved in Cx43 forward trafficking. METHODS AND RESULTS: High-resolution imaging reveals that Cx43 vesicles colocalize with nonsarcomeric actin in adult cardiomyocytes. Live-cell fluorescence imaging reveals Cx43 vesicles as stationary or traveling slowly (average speed 0.09 µm/s) when associated with actin. At any time, the majority (81.7%) of vesicles travel at subkinesin rates, suggesting that actin is important for Cx43 transport. Using Cx43 containing a hemagglutinin tag in the second extracellular loop, we developed an assay to detect transport of de novo Cx43 hemichannels to the plasma membrane after release from Brefeldin A-induced endoplasmic reticulum/Golgi vesicular transport block. Latrunculin A (for specific interference of actin) was used as an intervention after reinitiation of vesicular transport. Disruption of actin inhibits delivery of Cx43 to the cell surface. Moreover, using the assay in primary cardiomyocytes, actin inhibition causes an 82% decrease (P<0.01) in de novo endogenous Cx43 delivery to cell-cell borders. In Langendorff-perfused mouse heart preparations, Cx43/ß-actin complexing is disrupted during acute ischemia, and inhibition of actin polymerization is sufficient to reduce levels of Cx43 gap junctions at intercalated discs. CONCLUSIONS: Actin is a necessary component of the cytoskeleton-based forward trafficking apparatus for Cx43. In cardiomyocytes, Cx43 vesicles spend a majority of their time pausing at nonsarcomeric actin rest stops when not undergoing microtubule-based transport to the plasma membrane. Deleterious effects on this interaction between Cx43 and the actin cytoskeleton during acute ischemia contribute to losses in Cx43 localization at intercalated discs.