Locally administered heparin-binding epidermal growth factor-like growth factor reduces radiation-induced oral mucositis in mice

Oral mucositis refers to lesions of the oral mucosa observed in patients with cancer being treated with radiation with or without chemotherapy, and can significantly affect quality of life. There is a large unmet medical need to prevent oral mucositis that can occur with radiation either alone or in combination with chemotherapy. We investigated the efficacy of locally administered heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent epithelial proliferation and migration stimulator of the oral mucosa as a potential therapy to prevent radiation induced oral mucositis. Using a single dose (20 Gy) of radiation to the oral cavity of female C57BL/6 J mice, we evaluated the efficacy of HB-EGF treatment (5 µl of 10 µg/ml) solution. The results show that HB-EGF delivered post radiation, significantly increased the area of epithelial thickness on the tongue (dorsal tongue (42,106 vs 53,493 µm2, p < 0.01), ventral tongue (30,793 vs 39,095 µm2, *p < 0.05)) compared to vehicle control, enhanced new epithelial cell division, and increased the quality and quantity of desmosomes in the oral mucosa measured in the tongue and buccal mucosa. This data provides the proof of concept that local administration of HB-EGF has the potential to be developed as a topical treatment to mitigate oral mucositis following radiation.

A novel mouse model of chronic suppurative otitis media and its use in preclinical antibiotic evaluation

Chronic suppurative otitis media (CSOM) is a neglected pediatric disease affecting 330 million worldwide for which no new drugs have been introduced for over a decade. We developed a mouse model with utility in preclinical drug evaluation and antimicrobial discovery. Our model used immune-competent mice, tympanic membrane perforation and inoculation with luminescent Pseudomonas aeruginosa that enabled bacterial abundance tracking in real-time for 100 days. The resulting chronic infection exhibited hallmark features of clinical CSOM, including inhibition of tympanic membrane healing and purulent ear discharge. We evaluated the standard care fluoroquinolone ofloxacin and demonstrated that this therapy resulted in a temporary reduction of bacterial burden. These data are consistent with the clinical problem of persistent infection in CSOM and the need for therapeutic outcome measures that assess eradication post-therapeutic endpoint. We conclude that this novel mouse model of CSOM has value in investigating new potential therapies.

Quantitative assessment of bacterial growth phase utilizing flow cytometry

Flow cytometry is currently underutilized for bacterial phenotyping and standard microbiological techniques do not provide phenotypic information about the state of the bacterial disease. Pseudomonas aeruginosa is a human pathogen of increased importance in public health due to both the ability to cause chronic diseases and the prevalence of functionally different subsets that can be difficult to treat and diagnose. In the present study, we used flow cytometry to analyze the growth phase of P. aeruginosa. A simple method for single cell quantitative detection of bacterial biofilm and planktonic cells was established with a combination of membrane permeable (SYTO 60) and impermeable (TOTO-1) dyes plus the addition of polystyrene counting beads. The specificity of the dye combination for biofilm detection was determined by comparison with impaired biofilm forming strains of P. aeruginosa LasI/RhlI-/- and ∆PfPhage. Results suggest that flow cytometric bacterial phenotyping serves as an expandable platform that may be useful for enumeration of population level variation in P. aeruginosa studies.

The Role of Neutrophils in Pseudomonas aeruginosa Chronic Suppurative Otitis Media

Chronic suppurative otitis media is largely due to biofilm-forming bacteria, of which a common pathogen is Pseudomonas aeruginosa. Neutrophils are well-known to have various contributions in both promoting and restricting bacterial growth in other biofilm-mediated diseases, as they are one of the first cells recruited to sites of infection. Herein we propose that 1) fluorescent P. aeruginosa develop into biofilms and form chronic infections in the middle ear of a mouse model of Eustachian tube obstruction and acute tympanic membrane wounds; 2) this biofilm reduces functional capacity of professional phagocytes; 3) biofilm initiates apoptosis of responding neutrophils; and 4) neutrophils contribute to disease burden. We also determine neutrophil subsets with a leading role in the establishment of bacterial biofilm-mediated disease, and test the capacity of polymorphonuclear leukocytes to suppress planktonic infection.

Neutrophil function is quantified as a measure of phagocytosis and the production of extracellular traps; we also measure cell survival and clearance via efferocytosis to determine host-mediated barriers to this recalcitrant infection. Using flow cytometry coupled with fluorescent-tagged P. aeruginosa, we are able to assess middle ear effusion post-inoculation and develop a timeline of response to chronic infection in our novel CSOM model.

Importantly, this study establishes a model system for further immunological and translational studies, including testing of topical therapeutics. The results of this work will also inform potential efforts of neutrophils as predictors for disease exacerbation and guide additional therapeutic development for an illness affecting millions of children globally.