Expression of molecular markers for bone formation increases during experimental acute otitis media

Animal models of acute otitis media - A review with practical implications for laboratory research

Considerable animal research has focused on developing new strategies for the prevention and treatment of acute otitis media (AOM). Several experimental models of AOM have thus been developed. A PubMed search of the English literature was conducted from 1975 to July 2016 using the search terms "animal model" and "otitis media" from which 91 published studies were included for analysis, yielding 123 animal models. The rat, mouse and chinchilla are the preferred animals for experimental AOM models with their individual advantages and disadvantages. The most common pathogens used to create AOM are Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Streptococcus pneumoniae (types 3, 23 and 6A) and non-typeable Haemophilus influenzae (NTHi) are best options for inoculation into rat and mouse models. Adding viral pathogens such as RSV and Influenza A virus, along with creating ET dysfunction, are useful adjuncts in animal models of AOM. Antibiotic prophylaxis may interfere with the inflammatory response without a significant reduction in animal mortality.

Heparin binding-epidermal growth factor-like growth factor for the regeneration of chronic tympanic membrane perforations in mice

We aim to explore the role of epidermal growth factor (EGF) ligand shedding in tympanic membrane wound healing and to investigate the translation of its modulation in tissue engineering of chronic tympanic membrane perforations. Chronic suppurative otitis media (CSOM) is an infected chronic tympanic membrane perforation. Up to 200 million suffer from its associated hearing loss and it is the most common cause of pediatric hearing loss in developing countries. There is a need for nonsurgical treatment due to a worldwide lack of resources. In this study, we show that EGF ligand shedding is essential for tympanic membrane healing as it's inhibition, with KB-R7785, leads to chronic perforation in 87.9% (n=58) compared with 0% (n=20) of controls. We then show that heparin binding-EGF-like growth factor (5 μg/mL), which acts to shed EGF ligands, can regenerate chronic perforations in mouse models with 92% (22 of 24) compared with 38% (10 of 26), also with eustachian tube occlusion with 94% (18 of 19) compared with 9% (2 of 23) and with CSOM 100% (16 of 16) compared with 41% (7 of 17). We also show the nonototoxicity of this treatment and its hydrogel delivery vehicle. This provides preliminary data for a clinical trial where it could be delivered by nonspecialist trained healthcare workers and fulfill the clinical need for a nonsurgical treatment for chronic tympanic membrane perforation and CSOM.

Mouse models for human otitis media

Otitis media (OM) remains the most common childhood disease and its annual costs exceed $5 billion. Its potential for permanent hearing impairment also emphasizes the need to better understand and manage this disease. The pathogenesis of OM is multifactorial and includes infectious pathogens, anatomy, immunologic status, genetic predisposition, and environment. Recent progress in mouse model development is helping to elucidate the respective roles of these factors and to significantly contribute toward efforts of OM prevention and control. Genetic predisposition is recognized as an important factor in OM and increasing numbers of mouse models are helping to uncover the potential genetic bases for human OM. Furthermore, the completion of the mouse genome sequence has offered a powerful set of tools for investigating gene function and is generating a rich resource of mouse mutants for studying the genetic factors underlying OM.

Host's response in otitis media: understanding genetic susceptibility

Increasing evidence is emerging on genetic factors affecting host's response to infection in the middle ear. This review summarizes current knowledge on the field and on the contribution of nonspecific barriers, innate, and adaptive immunity. Better understanding of susceptibility to this very common disease will facilitate identification of high-risk individuals and optimization of prevention and treatment.

Modified aminosilane substrates to evaluate osteoblast attachment, growth, and gene expression in vitro

Bone cell-substrate interactions are important to understand in the design, selection, and surface modification of bone implants. To gain insight into such interactions, substrates designed with surface species approximating the physiological environment of bone matrix were studied. Osteoblasts (Ob) grown on three such surfaces were used to evaluate cell-substrate effects on attachment, growth, and gene expression as compared with controls. Initial surface preparation consisted of coating glass slides with aminopropyltriethoxy silane (APTES), after which the coated slides were modified with collagen-rich extracellular matrix components obtained from normally mineralizing avian tendon: the tripeptide arginine-glycine-aspartic acid (arg-gly-asp), or a precipitate formed from a metastable solution containing inorganic ions normally found in blood (simulated body fluid). Each of the modified substrates, as well as the nonmodified (APTES) control, provided distinctly different physical (evidenced by differences in rms roughness) and chemical surfaces for seeding primary osteoblasts obtained from 14-day-old normal embryonic chickens. Cell responses to each of the substrates were evaluated over a 21-day period in terms of Ob growth and growth rate, alkaline phosphatase (ALP) activity, and gene expression of type I collagen (COL I), osteopontin (OPN), osteocalcin (OC), and bone sialoprotein (BSP). From these preliminary experiments, indications are that cell attachment and growth in this study possibly are independent processes, an assumption that compels the need for further studies. Collagen-rich matrix-modified substrates had a distinct advantage over others when cell growth rate, ALP activity, and gene expression were considered; cells on these substrates exhibited increased ALP activity and enhanced expression of BSP, OPN, and OC when compared with those of cells on APTES controls or other modified substrates. These results indicate that matrix-modified substrates such as those used in this study provide favorable templates for tissue generation, suggesting their potential in the design of surfaces for bone implants.

Gene expression profiles of early pneumococcal otitis media in the rat

OBJECTIVE

To define the gene expression patterns during the early phases of a bacterial middle ear infection in the rat model.

METHOD

Using cDNA gene array technology, we profiled the mRNA expression of 1176 genes in a rat model of acute otitis media. We identified changes in gene expression two-fold or greater 12 and 48 h after bilateral ME inoculation with either tryptic soy broth (TSB) or Streptococcus pneumoniae in TSB.

RESULTS

Transcripts of cytokines and cell adhesion molecules were up-regulated by 12 h, but returned to placebo transcription levels by 48 h. Three of six stress-response genes, including inducible nitric oxide synthase, GADD45 and heat shock protein 27 (HSP27) were up-regulated by 12 h, with HSP27 transcription levels continuing to rise through 48 h. All assayed transcription factors were up-regulated by 12 h, but only c-fos and c-jun up-regulation persisted to the 48-h time point. Up-regulation of apoptosis-related genes, except for bcl-x, was not evident until 48 h. These gene expression patterns reflected an early proinflammatory response consisting of cytokines, cell adhesion and stress-response molecules at 12 h followed by an up-regulation of apoptosis-related genes at 48 h.

CONCLUSION

Downstream targets of several transcription factors, up-regulated transiently at 12 h, control secondary effects of S. pneumoniae infection, including apoptosis of neutrophils and mucosal epithelial cells, bone proliferation and promotion of leukocyte differentiation. These observations lead to a greater understanding of the early events in the pathogenesis of an AOM episode and highlight therapeutic targets, which may play a roll in the sequelae of AOM.