Diversity of the cochlear and vestibular pathologies in human temporal bones of newborns infected with cytomegalovirus

Hypothesis

Human temporal bones of newborns with congenital cytomegalovirus (cCMV) infection can be characterized by diverse cochlear and vestibular histopathologies associated with the variability in sensorineural hearing loss (SNHL) and vestibular dysfunction in these newborns.

Background

Only a small number of studies on the cochlear and vestibular pathologies in human temporal bones with cCMV infection have been previously reported.

Methods

Cochleovestibular histopathologies were evaluated in 4 temporal bones from 3 infants with cCMV infection by light microscopy.

Results

In one available temporal bone of the infant in Case 1, no cytomegalic cells were found. Large areas of cellular and non-cellular structures were observed in the scala tympani of the perilymphatic space; however, there was no obvious loss of cochlear or vestibular hair cells. In Case 2, cytomegalic cells, a loss of vestibular hair cells, and a loss of nerve fibers were observed only in the area of dark cells in the vestibular labyrinth of the left temporal bone. No cytomegalic cells were found in the right temporal bone of the same infant; however, there was a loss of outer hair cells in the organ of Corti and hypervascularity in the stria vascularis. The one available temporal bone of the infant in Case 3 showed cytomegalic cells and a loss of hair cells in both cochlear and vestibular parts of the inner ear.

Conclusions

Human temporal bones of newborns with cCMV demonstrate diverse cochleovestibular histopathologies. This diversity is consistent with the variable SNHL and vestibular dysfunction reported in infected newborns.

Cytomegalovirus-induced pathology in human temporal bones with congenital and acquired infection

OBJECTIVE

Publications on histopathology of human temporal bones with cytomegalovirus (CMV) infection are limited. We aim to determine histopathology of the inner ears and the middle ears in human temporal bones with congenital and acquired CMV infections.

METHODS

Temporal bones from 2 infants with congenital and 2 adults with acquired CMV infection were evaluated by light microscopy.

RESULTS

Two infants with congenital CMV infection showed striking pathological changes in the inner ear. There was a hypervascularization of the stria vascularis in the cochlea of the first infant, but no obvious loss of outer and inner hair cells was seen in the organ of Corti. However, cytomegalic cells and a loss of outer hair cells were found in the cochlea of the second infant. The vestibular organs of both infants showed cytomegalic cells, mostly located on dark cells. There was a loss of type I and type II hair cells in the macula of the saccule and utricle. Loss of hair cells and degeneration of nerve fibers was also seen in the semicircular canals. Both infants with congenital infection showed abundant inflammatory cells and fibrous structures in the middle ear cavity. No evidence of cytomegalic cells and hair cell loss was found in the cochlea or vestibular labyrinth in acquired CMV infection.

CONCLUSIONS

In two infants with congenital CMV infection, the cochlea, vestibule, and middle ear were highly affected. Temporal bones of adult donors with acquired viral infection showed histological findings similar to donors of the same age without ear disease.

Neutrophil Extracellular Traps and Fibrin in Otitis Media: Analysis of Human and Chinchilla Temporal Bones

Background

Bacterial resistance in acute otitis can result in bacterial persistence and biofilm formation, triggering chronic and recurrent infections.

Objective

To investigate the middle ear inflammatory response to bacterial infection in human and chinchilla temporal bones.

Design, Setting, and Participants

Six chinchillas underwent intrabullar inoculations with 0.5 mL of 106 colony-forming units (CFUs) of Streptococcus pneumoniae, serotype 2. Two days later, we counted bacteria in middle ear effusions postmortem. One ear from each chinchilla was processed in paraffin and sectioned at 5 µm. The opposite ear was embedded in epoxy resin, sectioned at a thickness of 1 µm, and stained with toluidine blue. In addition, we examined human temporal bones from 2 deceased donors with clinical histories of otitis media (1 with acute onset otitis media, 1 with recurrent infection). Temporal bones had been previously removed at autopsy, processed, embedded in celloidin, and cut at a thickness of 20 µm. Sections of temporal bones from both chinchillas and humans were stained with hematoxylin-eosin and immunolabeled with antifibrin and antihistone H4 antibodies.

Main Outcome Measures

Histopatological and imminohistochemical changes owing to otitis media.

Results

Bacterial counts in chinchilla middle ear effusions 2 days after inoculation were approximately 2 logs above initial inoculum counts. Both human and chinchilla middle ear effusions contained bacteria embedded in a fibrous matrix. Some fibers in the matrix showed positive staining with antifibrin antibody, others with antihistone H4 antibody.

Conclusions and Relevance

In acute and recurrent otitis media, fibrin and neutrophil extracellular traps (NETs) are part of the host inflammatory response to bacterial infection. In the early stages of otitis media the host defense system uses fibrin to entrap bacteria, and NETs function to eliminate bacteria. In chronic otitis media, fibrin and NETs appear to persist.

Deterioration of Vestibular Cells in Labyrinthitis

OBJECTIVE

To quantitatively assess the effect of serous labyrinthitis, suppurative labyrinthitis, and labyrinthitis ossificans on vestibular hair cells, dark cells, and transitional cells.

METHODS

We examined human temporal bone specimens with serous labyrinthitis, suppurative labyrinthitis, and labyrinthitis ossificans, then compared them with age-matched control groups without labyrinthitis. We evaluated the density of type I and II vestibular hair cells, dark cells, and transitional cells in the peripheral sensorial organs.

RESULTS

The mean density of type I vestibular hair cells in the maculae of the saccule significantly differed between the serous labyrinthitis group and its control group. The loss of type I and II vestibular hair cells in all of the peripheral sensorial organs was significantly higher in the suppurative labyrinthitis group than in its control group. The mean density of dark cells in the lateral and posterior semicircular canals was significantly lower in the suppurative labyrinthitis group than in its control group. The mean density of type I and II vestibular hair cells, dark cells, and transitional cells was significantly lower in the labyrinthitis ossificans group than in its control group.

CONCLUSION

The loss of vestibular hair cells and degenerative changes in dark cells and transitional cells could affect vestibular function in patients with labyrinthitis.

A three-dimensional analysis of the endolymph drainage system in Ménière disease

OBJECTIVES/HYPOTHESIS

To measure the volume of the endolymph drainage system in temporal bone specimens with Ménière disease, as compared with specimens with endolymphatic hydrops without vestibular symptoms and with nondiseased specimens STUDY DESIGN: Comparative human temporal bone analysis.

METHODS

We generated three-dimensional models of the vestibular aqueduct, endolymphatic sinus and duct, and intratemporal portion of the endolymphatic sac and calculated the volume of those structures. We also measured the internal and external aperture of the vestibular aqueduct, as well as the opening (if present) of the utriculoendolymphatic (Bast's) valve and compared the measurements in our three study groups.

RESULTS

The volume of the vestibular aqueduct and of the endolymphatic sinus, duct, and intratemporal endolymphatic sac was significantly lower in the Ménière disease group than in the endolymphatic hydrops group (P <.05). The external aperture of the vestibular aqueduct was also smaller in the Ménière disease group. Bast's valve was open only in some specimens in the Ménière disease group.

CONCLUSIONS

In temporal bones with Ménière disease, the volume of the vestibular aqueduct, endolymphatic duct, and intratemporal endolymphatic sac was lower, and the external aperture of the vestibular aqueduct was smaller as compared with bones from donors who had endolymphatic hydrops without vestibular symptoms and with nondiseased bones. The open status of the Bast's valve in the Ménière disease group could be secondary to higher retrograde endolymph pressures caused by smaller drainage systems. These anatomic findings could correlate with the reason that some patients with hydrops develop clinical symptoms, whereas others do not.

LEVEL OF EVIDENCE

N/A Laryngoscope, 127:E170-E175, 2017.

Pathologic Changes of the Peripheral Vestibular System Secondary to Chronic Otitis Media

OBJECTIVE

To evaluate the histopathologic changes of dark, transitional, and hair cells of the vestibular system in human temporal bones from patients with chronic otitis media.

STUDY DESIGN

Comparative human temporal bone study.

SETTING

Otopathology laboratory.

SUBJECTS AND METHODS

To compare the density of vestibular dark, transitional, and hair cells in temporal bones with and without chronic otitis media, we used differential interference contrast microscopy.

RESULTS

In the chronic otitis media group (as compared with the age-matched control group), the density of type I and type II hair cells was significantly decreased in the lateral semicircular canal, saccule, and utricle (P < .05). The density of type I cells was also significantly decreased in the chronic otitis media group in the posterior semicircular canal (P = .005), but that of type II cells was not (P = .168). The mean number of dark cells was significantly decreased in the chronic otitis media group in the lateral semicircular canal (P = .014) and in the posterior semicircular canal (P = .002). We observed no statistically significant difference in the density of transitional cells between the 2 groups (P > .1).

CONCLUSION

The findings of our study suggest that the decrease in the number of vestibular sensory cells and dark cells could be the cause of the clinical symptoms of imbalance of some patients with chronic otitis media.

Cochlear changes in serous labyrinthitis associated with silent otitis media: A human temporal bone study

PURPOSE

To determine histopathological findings in the cochlea of human temporal bones with serous labyrinthitis.

MATERIALS AND METHODS

We compared human temporal bones with serous labyrinthitis (20 cases) associated with silent otitis media and without serous labyrinthitis (20 cases) to study location of serous labyrinthitis, the degree of endolymphatic hydrops, number of spiral ganglion cells and hair cells, loss of fibrocytes in the spiral ligament, and areas of the spiral ligament and stria vascularis.

RESULTS

The serous labyrinthitis caused significant loss of outer hair cells in the lower basal (P=0.006), upper basal (P=0.005), and lower middle (P=0.011) cochlear turns, and significant increase in the degree of endolymphatic hydrops than the control group (P=0.036). No significant difference was found in the loss of inner hair cells, in the number of spiral ganglion cells and fibrocytes in the spiral ligament, and in areas of the stria vascularis and spiral ligament (P>0.05).

CONCLUSIONS

Serous labyrinthitis resulted in significant loss of outer hair cells and significant increase in the degree of endolymphatic hydrops.

Pneumococcal PspA and PspC proteins: potential vaccine candidates for experimental otitis media

OBJECTIVE

Otitis media is the most commonly diagnosed disease in ambulatory care and Streptococcuspneumoniae continues to be the most common bacterial agent. Bacterial resistance to antibiotics underscores the need for better vaccines. Current pneumococcal conjugate vaccines are modestly protective against otitis media; however, limited serotype coverage and serotype replacement have led to the investigation of pneumococcal proteins as potential vaccine candidates. Two proteins, pneumococcal surface proteins A (PspA) and C (PspC) are important virulence factors, expressed by virtually all strains. Although a number of pneumococcal proteins have been investigated in other infection sites, these proteins can have diverse organ-specific effects. In this study, we investigated the viability and virulence of single (PspA(-) and PspC(-)) and double (PspA(-)/PspC(-)) mutants of pneumococcal PspA and PspC proteins in the chinchilla middle ear.

METHODS

Bullae of 24 chinchillas were inoculated with 0.5 ml of 10(6) colony forming units (CFUs)/ml bacteria: 6 with wild-type D39 strain; 6 with PspA(-); 6 with PspC(-); and 6 with PspA(-)/PspC(-) isogenic mutant strains. Bacterial CFU levels in middle ear effusions and light microscopic analysis of the number of inflammatory cells in the round window membrane (RWM) were compared 48 h after inoculation.

RESULTS

At 48 h, CFUs in middle ears were increased for wild-type and PspC(-) strains compared to inoculum levels; however, they were significantly less for the group inoculated with the PspC(-) strain compared to wild-type strain. No bacteria were detected in the PspA(-) and PspA(-)/PspC(-) groups. The number of inflammatory cells in the RWM was significantly higher in wild-type compared to the PspA(-), PspC(-), and PspA(-)/PspC(-) groups. No significant difference in number of inflammatory cells was observed between any pairs of groups inoculated with mutant strains.

CONCLUSION

Viability and virulence of the PspC(-) strain were similar to the wild-type strain. The single PspA(-) and double PspA(-)/PspC(-) mutants were highly attenuated in the ear. Bacterial clearance of the PspA(-)/PspC(-) double mutant was indistinguishable from that of the PspA mutant. These studies provide no reason to exclude PspC from a multi-component protein vaccine containing PspA.

The pathology of silent otitis media: a predecessor to tympanogenic meningitis in infants

OBJECTIVE

To determine the association of bacteria embedded within a fibrous matrix in the middle and inner ear in infants with tympanogenic meningitis.

METHODS

Thirty-one cases with meningitis from the human temporal bone collection at the University of Minnesota were screened to select those with tympanogenic meningitis. Inclusion criteria for tympanogenic meningitis were acute meningitis with histopathological evidence of chronic otitis media, and no other source of infection. The presence of labyrinthitis and pathologic changes such as granulation tissue, fibrosis, cholesterol granuloma, cholesteatoma, tympanic membrane perforation, tympanosclerosis, and the type of effusion were noted. The extent and location of bacteria embedded in a fibrous matrix were also explored.

RESULTS

Seventeen temporal bones, from nine cases that included two females and seven males, ranging in age from five to twenty-three months, met our criteria of tympanogenic meningitis. Eighty two percent of these temporal bones had bacteria within the fibrous matrices (BFM). BFM were located in one anatomical region in one temporal bone and multiple anatomic regions in sixteen temporal bones. The most common locations were the areas near the oval and round windows. They were also commonly seen in the epitympanum, facial recess, and supratubal recess. BFM within the inner ear were observed in the scala tympani and modiolus in the middle and basal turns of the cochleae of nine temporal bones. In one of these temporal bones, BFM were seen in the internal auditory canal. Labyrinthitis was seen in all ears. The tympanic membrane was intact in all cases. BFM were not seen in three temporal bones from two patients. In one case only one side was available for study.

CONCLUSIONS

Our findings show an association between the presence of BFM in the ear with chronic pathologic changes and tympanogenic meningitis. Potential pathways of bacteria from the middle ear include hematogeous spread and/or direct spread to dura through the tympanic tegmen, and/or to the inner ear through the oval and round windows, and from there to the modiolus and the meninges. Chronic pathologic changes in the middle ear behind an intact tympanic membrane and the lack of ear symptoms may result in potentially serious sequelae and complications in infant age groups. There should be a heightened awareness of this condition.

Viability and virulence of pneumolysin, pneumococcal surface protein A, and pneumolysin/pneumococcal surface protein A mutants in the ear

IMPORTANCE

Understanding how pneumococcal proteins affect the pathology of the middle ear and inner ear is important for the development of new approaches to prevent otitis media and its complications.

OBJECTIVES

To determine the viability and virulence of Streptococcus pneumoniae mutants deficient in pneumolysin (Ply-) and pneumococcal surface protein A (PspA-) in the chinchilla middle ear.

DESIGN

Bullae of chinchillas were inoculated bilaterally with wild-type (Wt), Ply-, PspA-, and Ply-/PspA- strains. Bacterial colony-forming units (CFUs) in middle ear effusions were counted at 48 hours. The CFUs of the PspA- group were also counted at 6 to 36 hours after inoculation. Temporal bone histopathological results were compared.

SETTING AND PARTICIPANTS

Twenty-seven chinchillas in an academic research laboratory.

EXPOSURE

Chinchilla middle ears were inoculated with S pneumoniae to produce sufficient volumes of effusions and noticeable histopathological changes in the ears.

MAIN OUTCOMES AND MEASURES

The CFU counts in the middle ear effusions and histopathological changes were compared to determine the effect of pneumococcal protein mutations on chinchilla ears.

RESULTS

At 48 hours, CFUs in middle ears were increased for the Wt and Ply-/PspA- strains, but Ply- remained near inoculum level. No bacteria were detected in the PspA- group. The CFUs of PspA- decreased over time to a low level at 30 to 36 hours. In vitro, PspA- in Todd-Hewitt broth showed an increase in bacterial growth of 2 logs at 43 hours, indicating PspA- susceptibility to host defenses in vivo. The PspA- and Ply- groups had fewer pathologic findings than the Wt or Ply-/PspA- groups. Histopathological analysis showed significant differences in the number of bacteria in the scala tympani in the Wt group compared with the Ply-, PspA-, and Ply-/PspA- groups. The PspA- strain was the least virulent.

CONCLUSIONS AND RELEVANCE

The PspA- mutant was much less viable and less virulent in the ear than the Wt, Ply-, and Ply-/PspA- strains. There was no significant attenuation in the viability and virulence of the Ply-/PspA- mutant compared with the Wt or single mutants. The viability and virulence of pneumococcal mutants seemed to be protein and organ specific.

The Continuum of Biofilms in Different Types of Otitis Media

Objective: It is recognized that the various types of otitis media (OM) follow a continuum with early forms of the disease leading to more chronic forms over time. This study investigates if biofilms play a role in conjunction with the continuum of pathological changes in different stages of OM.

Method: Thirty human temporal bones of each type, sero- purulent OM (SPOM), purulent OM (POM), chronic OM with purulent effusion (PCOM), and fourteen mucoid OM (MOM), were selected. We defined “web-like structures” with host defense cells and bacterial bodies as biofilm. We examined the occurrence, frequency, and anatomic locations of biofilms.

Results: Biofilms were observed in 10 (33.3%) of the 30 temporal bones with SPOM, 19 (63.3%) with POM, and 20 (66.7%) with PCOM. A significant difference of biofilms’ frequency between SPOM and POM ( P = .038), and SPOM and PCOM ( P = .017), was observed. The most common anatomic location was mastoid antrum and mastoid cells (35 of 49 temporal bones, 71.4%). The number of anatomic locations with biofilms was 2.20 ± 1.03 in SPOM, 2.89 ± 1.70 in POM, and 4.15 ± 1.60 in PCOM. There was a significant difference of locations between PCOM and SPOM ( P < .001), and PCOM and POM ( P = .022).

Conclusion: The frequency of biofilms suggests that the presence of biofilms is associated with the severity of OM. The growth and development of biofilms may play an important role in the progression of chronicity of OM.

Biofilm in Human Temporal Bones with Pneumococcal Otitis Media

Objective: Evaluate biofilm formation in the middle ear and mastoid and correlate the clinical data with the histopathologic findings in human temporal bones (TB) from patients with Streptococcus pneumonia positive chronic otitis media (COM).

Method: Thirty-seven TB from 20 cases with COM were selected based on positive blood cultures for Streptococcus pneumonia. The presence, amount, and localization of biofilm, and fluid, type of inflammatory cells, labyrinthitis, use of antibiotics, and coinfection of H influenza were noted. Data were compared between the groups with/without biofilm.

Results: Biofilms were observed in 22 (59%) of the 37 TB with COM. The most common anatomic localization of biofilm was facial recess, the least common was the Eustachian tube. When comparing biofilm positive and negative groups there was statistical significance in the correlation regarding type of inflammatory cells ( P .05).

Conclusion: There is higher incidence of biofilm in chronic otitis media with pneumococcal infection. Because biofilms can be found more commonly in obscure areas such as facial recess and sinus tympany and less localized in well aerated areas such as the Eustachian tube, radical cleaning of those areas and optimum aeration seem essential to avoid recurrence of infection.

Effect of apolactoferrin on experimental pneumococcal otitis media

OBJECTIVE

To find the effect of apolactoferrin administration on the middle and inner ears after experimentally induced pneumococcal otitis media.

DESIGN

Histopathologic and morphometric analysis of the middle and inner ears.

SETTING

University of Minnesota, Minneapolis.

SUBJECTS

Ten chinchillas.

INTERVENTIONS

The middle ear cavities of chinchillas were inoculated bilaterally with type 2 wild-type Streptococcus pneumoniae. Twenty-four hours later, the ears of 5 of the animals were injected with phosphate-buffered saline (PBS) and the other 5 with human apolactoferrin. The animals were killed 24 hours after the last injection. Bacterial counts were made of the middle ear effusions, and the cochleae were processed for histologic analysis. The thickness of the round window membranes and bacterial and inflammatory cell infiltration of the round window membranes, and scala tympani and damage of the hair cells and stria vascularis were compared for these 2 groups of animals.

MAIN OUTCOME MEASURES

Comparison of inflammatory and bacterial cells in the middle and inner ears, and damage to inner ear structures.

RESULTS

Bacterial plate counts of middle ear effusions (P  = .005) and the number of inflammatory cells in the round window membrane (P  = .047) were significantly lower in the apolactoferrin group compared with the group treated with PBS.

CONCLUSION

Further investigation of apolactoferrin as a nonantibiotic approach for the treatment of otitis media and its complications is needed to confirm its safety and efficacy.

Cochlear pathology in human temporal bones with otitis media

CONCLUSION

Middle and inner ear interactions in otitis media can lead to cochlear pathology. More severe pathological changes observed in the basal turn of the cochlea are consistent with prevalence of sensorineural hearing loss at higher frequencies in patients with otitis media.

METHODS

Of 614 temporal bones with otitis media, 47 with chronic and 35 with purulent otitis media were selected following strict exclusion of subjects with a history of acoustic trauma, head trauma, ototoxic drugs, and other diseases affecting the cochlear labyrinth. Temporal bones with labyrinthine inflammatory changes were further evaluated for loss of hair cells and other histopathologic changes compared to age-matched controls.

RESULTS

In all, 19% of temporal bones with chronic and 9% with purulent otitis media showed labyrinthine inflammatory changes. In chronic otitis media, inflammatory changes were: 56% localized purulent, 22% localized serous, 11% generalized seropurulent, and 11% generalized serous. Inflammatory changes in temporal bones with purulent otitis media included 67% localized purulent and 33% were generalized seropurulent. Pathological findings included: serofibrinous precipitates and inflammatory cells in scala tympani of basal turn and cochlear aqueduct, significant loss of outer and inner hair cells, and significant decrease in area of stria vascularis in the basal turn of the cochlea, as compared to controls.

Effect of lipooligosaccharide mutations of Haemophilus influenzae on the middle and inner ears

OBJECTIVE

The purpose of this study was to determine the virulence of nontypeable Haemophilus influenzae 2019 (NTHi 2019) and its two lipooligosaccharide (LOS) mutant strains, B29 (gene htrB) and DK1 (gene rfaD), and compare their effect on the middle ear, round window membrane, and inner ear.

RESULTS

Fifteen chinchillas were divided into three equal groups and their bullas inoculated bilaterally with 0.5 ml of 10(2)CFU/ml of parent NTHi 2019, B29 or DK1 mutant strains. Two days after inoculation all animals had otitis media and inflamed middle ear mucosa. There was a trend of greater thickness and infiltration of the round window membrane in animals inoculated with the wild-type NTHi strain compared to the mutant strains and a significant increase in both inflammatory cell infiltration and bacteria presence in the scala tympani area of the inner ear. Strial edema was only observed in the wild-type-inoculated group.

CONCLUSIONS

LOS mutants of NTHi appear to have a reduced ability to pass through the round window membrane resulting in less inner ear inflammation and pathological changes.

Virulence of pneumococcal proteins on the inner ear

OBJECTIVE

To investigate the effects of the virulence characteristics of specific pneumococcal proteins on the inner ear.

MAIN OUTCOME MEASURES

A histologic comparison of inflammatory cell infiltration and pathologic changes in the round window membrane and inner ear.

RESULTS

Most of the animals inoculated with high-dose pneumolysin or wild-type bacteria showed severe pathologic changes of the inner ears. The inner ears of most animals inoculated with surface protein A or surface antigen A-deficient bacteria appeared normal.

CONCLUSIONS

Pneumococcal surface protein A and pneumococcal surface antigen A are 2 important virulence factors in inner ear damage secondary to pneumococcal otitis media. Mutation of these virulence factors results in less inner ear damage.

The round window membrane in otitis media: effect of pneumococcal proteins

OBJECTIVE

To determine whether mutants of Streptococcus pneumoniae that are deficient in pneumococcal surface protein A (PspA), pneumococcal surface antigen A (PsaA), or pneumolysin (Ply) are less virulent and less likely to penetrate the round window membrane (RWM).

DESIGN

Histopathologic comparison of wild-type S. pneumoniae and its mutants deficient in PspA, PsaA, and Ply.

SETTING

Otopathology Laboratory, Department of Otolaryngology, University of Minnesota Medical School, Minneapolis.

PARTICIPANTS

Forty young chinchillas (weight, 250-350 g) with normal external auditory canals and tympanic membranes.

INTERVENTION

Animals were divided into 3 groups and bullae inoculated with wild-type S. pneumoniae serotype 2, strain D39, or its mutants deficient in PspA, PsaA, or Ply. Two days after inoculation, bullae were processed for light microscopy and transmission electron microscopy.

MAIN OUTCOME MEASURES

Comparison of inflammatory cell infiltration and penetration of bacteria into the round window membrane and adjacent scala tympani.

RESULTS

Histopathologic findings using wild-type S. pneumoniae and Ply(-) mutant were similar and included otitis media and the presence of inflammatory cells and damage to and passage of bacteria through the RWM. Although otitis media was seen with the PspA(-) and PsaA(-) mutants, we observed no passage of bacteria through the RWM.

CONCLUSIONS

Both PspA and PsaA affect the ability of S. pneumoniae to penetrate the RWM. Understanding the role of S. pneumoniae virulence proteins in the pathogenesis of the middle ear, RWM, and inner ear will provide new strategies for the prevention and treatment of otitis media and its complications.

Up-regulation of macrophage migration inhibitory factor induced by endotoxin in experimental otitis media with effusion in mice

CONCLUSION

Injection of endotoxin into the middle ear causes production of macrophage migration inhibitory factor (MIF) in an experimental mouse model of otitis media with effusion (OME). Down-regulation of MIF may become a new approach for the management of OME.

OBJECTIVE

To determine the role of MIF in OME.

MATERIALS AND METHODS

Mice were divided into two groups and their middle ears were injected with either endotoxin or phosphate-buffered saline (PBS). Mice were sacrificed at 6 h, 12 h, or 1, 3, 7, or 14 days after injection and concentrations of MIF, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) in middle ear effusions were measured by enzyme-linked immunosorbent assay.

RESULTS

Concentrations of MIF in the endotoxin group at 1 day and 3 days were significantly higher than in the PBS control group. Concentrations of IL-1beta in the endotoxin group at 6 h, 12 h, 1 day, and 3 days were significantly higher than in controls. Concentrations of TNF-alpha in the endotoxin group at 1 day and 3 days were significantly higher than in controls. Concentration of MIF in the endotoxin group was positively correlated with that of IL-1beta and TNF-alpha.

Pneumococcal peptidoglycan-polysaccharides induce the expression of interleukin-8 in airway epithelial cells by way of nuclear factor-kappaB, nuclear factor interleukin-6, or activation protein-1 dependent mechanisms

Cell envelope compounds of bacteria trigger immune and inflammatory reactions by way of chemokines/cytokines. In this study, we demonstrated that pneumococcal peptidoglycan-polysaccharides (PGPS) induced the production of interleukin (IL)-8 by way of nuclear factor (NF)-kappaB, nuclear factor interleukin (NF-IL)6, and activation protein (AP)-1 dependent mechanisms in the human bronchial epithelial cells (NL-20) in a dose- and time-dependent manner in vitro, and the mutation of either the NF-kappaB, NF-IL6, or AP-1 binding sites in the promoter of IL-8 abrogated the IL-8 transcriptional activity. In a similar way, lipopolysaccharides induced the promoter activation of IL-8 in NL-20. However, the PGPS-induced IL-8 promoter activation in rodent middle ear epithelial cells required NF-kappaB and NF-IL6 but not AP-1.

Age-related functional and histopathological changes of the ear in the MPS I mouse

OBJECTIVE

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive disorder caused by a mutation in the gene encoding the enzyme alpha-L-iduronidase. This enzyme is responsible for degradation of dermatan and heparan sulfates. Enzyme deficiency results in their accumulation in lysosomes of virtually all organs, resulting in severe somatic and neurological changes. Clinical findings of otitis media with mixed hearing loss are common. Cellular and molecular mechanisms of ear pathology and hearing loss are not understood. The purpose of this study is to describe the age-related audiologic and histopathologic changes of the ear in the mouse model of MPS I.

METHODS

Auditory brainstem responses (ABR) were obtained to clicks and tone bursts at 1-32kHz, and pathological changes to middle and inner ears were studied with light and electron microscopy in 53 mice that included: (1) wild type (+/+)-five at 2 months, five at 4-6 months, and five at 13-19 months; (2) heterozygotes (+/-)-four at 2 months, five at 4-6 months, and eight at 13-19 months; and (3) homozygotes (-/-)-five at 2 months, six at 4-6 months, and five at 13-19 months. Histopathology was also done on five newborn -/- mice.

RESULTS

In newborns, no lysosomal storage was observed and the ear appeared age appropriately normal. In all other -/- mice, cells with lysosomal storage vacuoles were observed in spiral ligament, spiral prominence, spiral limbus, basilar membrane, epithelial and mesothelial cells of Reissner's membrane, endothelial cells of vessels, and some ganglion cells; their number increased with aging. Hair cell loss was not observed at 2 or 6 months, but there was total loss of the organ of Corti in year-old mice. Hearing of -/- mice was significantly decreased at all ages compared to +/+ and +/-. Hearing loss progressed from mild to moderate loss at 2 months to profound at 6 months and total deafness by 1 year of age.

CONCLUSIONS

Progressive age-related changes suggest early therapeutic intervention to prevent sensory cell damage and hearing loss.

Specificity of Aminoacylase III-Mediated Deacetylation of Mercapturic Acids

Trichloroethylene (TCE) and other halogenated alkenes are known environmental contaminants with cytotoxic and nephrotoxic effects, and are potential carcinogens. Their metabolism via the mercapturate metabolic pathway was shown to lead to their detoxification. The final products of this pathway, mercapturic acids or N-acetyl-l-cysteine S-conjugates, are secreted into the lumen in the renal proximal tubule. The proximal tubule may also deacetylate mercapturic acids, and the resulting cysteine S-conjugates are transformed by cysteine S-conjugate beta-lyases to nephrotoxic reactive thiols. The specificity and rate of mercapturic acid deacetylation may determine the toxicity of certain mercapturic acids; however, the exact enzymologic processes involved are not known in detail. In the present study we characterized the kinetics of the recently cloned mouse aminoacylase III (AAIII) toward a wide spectrum of halogenated mercapturic acids and N-acetylated amino acids. In general, the V(max) value of AAIII was significantly larger with chlorinated and brominated mercapturic acids, whereas fluorination significantly decreased it. The enzyme deacetylated mercapturic acids derived from the TCE metabolism including N-acetyl-S-(1,2-dichlorovinyl)-l-cysteine (NA-1,2-DCVC) and N-acetyl-S-(2,2-dichlorovinyl)-l-cysteine (NA-2,2-DCVC). Both mercapturic acids induced cytotoxicity in mouse proximal tubule mPCT cells expressing AAIII, which was decreased by an inhibitor of beta-lyase, aminooxyacetate. The toxic effect of NA-2,2-DCVC was smaller than that of NA-1,2-DCVC, indicating that factors other than the intracellular activity of AAIII mediate the cytotoxicity of these mercapturic acids. Our results indicate that in proximal tubule cells, AAIII plays an important role in deacetylating several halogenated mercapturic acids, and this process may be involved in their cyto- and nephrotoxicity.

Otosclerosis: etiopathogenesis and histopathology

Otosclerosis is a disease of the bony labyrinth manifesting clinically as a progressive conductive hearing loss, a mixed-type hearing loss, or a sensorineural hearing loss. The age of onset of the hearing loss caused by otosclerosis is principally between 15 and 40 years. Although histopathological inner ear changes due to otosclerosis have been very well documented, the true etiopathogenesis of the disease has yet to be described despite intensive research. Both genetic and environmental factors have been implicated, however.

Round window membrane and labyrinthine pathological changes: an overview

The round window membrane is considered the most likely pathway from the middle to the inner ear. Various substances placed in the middle ear have been seen to pass through the round window membrane. Once toxic substances or inflammatory mediators such as cytokines and nitric oxide enter the inner ear, various inner ear sequelae such as labyrinthitis, endolymphatic hydrops, sensorineural hearing loss or more insidious diseases can occur.

The structure of tip links and kinocilial links in avian sensory hair bundles

Recent studies have indicated that the tip links and kinocilial links of sensory hair bundles in the inner ear have similar properties and share a common epitope, and that cadherin 23 may also be a component of each link type. Transmission electron microscopy was therefore used to study and compare the fine structure of the tip links and kinocilial links in avian sensory hair bundles. Tannic acid treatment revealed a thin strand, 150-200 nm long and 8-11 nm thick, present in both link types. Fourier analysis of link images showed that the strand of both link types is formed from two filaments coiled in a helix-like arrangement with an axial period of 20-25 nm, with each filament composed of globular structures that are approximately 4 nm in diameter. Differences in the radius and period of the helix-like structure may underlie the observed variation in the length of tip and kinocilial links. The similar helix-like structure of the tip links and kinocilial links is in accord with the presence of a common cell-surface antigen (TLA antigen) and similarities in the physical and chemical properties of the two link types. The spacing of the globular structures comprising each filament of the two link types is similar to the 4.3 nm center-to-center spacing reported for the globular cadherin repeat, and is consistent with the suggestion that cadherin 23 is the tip link.

Structural characterization, tissue distribution, and functional expression of murine aminoacylase III

Many xenobiotics are detoxified through the mercapturate metabolic pathway. The final product of the pathway, mercapturic acids ( N-acetylcysteine S-conjugates), are secreted predominantly by renal proximal tubules. Mercapturic acids may undergo a transformation mediated by aminoacylases and cysteine S-conjugate β-lyases that leads to nephrotoxic reactive thiol formation. The deacetylation of cysteine S-conjugates of N-acyl aromatic amino acids is thought to be mediated by an aminoacylase whose molecular identity has not been determined. In the present study, we cloned aminoacylase III, which likely mediates this process in vivo, and characterized its function and structure. The enzyme consists of 318 amino acids and has a molecular mass (determined by SDS-PAGE) of ∼35 kDa. Under nondenaturing conditions, the molecular mass of the enzyme is ∼140 kDa as determined by size-exclusion chromatography, which suggests that it is a tetramer. In agreement with this hypothesis, transmission electron microscopy and image analysis of aminoacylase III showed that the monomers of the enzyme are arranged with a fourfold rotational symmetry. Northern analysis demonstrated an ∼1.4-kb transcript that was expressed predominantly in kidney and showed less expression in liver, heart, small intestine, brain, lung, testis, and stomach. In kidney, aminoacylase III was immunolocalized predominantly to the apical domain of S1 proximal tubules and the cytoplasm of S2 and S3 proximal tubules. The data suggest that in kidney proximal tubules, aminoacylase III plays an important role in deacetylating mercapturic acids. The predominant cytoplasmic localization of aminoacylase III may explain the greater sensitivity of the proximal straight tubule to the nephrotoxicity of mercapturic acids.

Structure of the stereocilia side links and morphology of auditory hair bundle in relation to noise exposure in the chinchilla

Stereocilia side links are directly involved in the maintenance of stereociliary bundle integrity in hair cells. The structure of the stereocilia side links and morphology of the auditory hair bundle in relation to noise exposure in the chinchilla was investigated by transmission electron microscopy. The outer hair cell (OHC) stereocilia side link was suggested to consist of extracellular, juxta-membrane and thin filamentous regions. Two beaded filaments were folded at their distal ends and fastened in one globule in the center between stereocilia. An intracellular, submembraneous layer appeared to form a bridge between the actin core and the extracellular, juxta-membrane region of the side link. In normal physiological conditions, most OHC stereocilia had a regular distribution of side links, forming a 'zipper-like' lattice between stereocilium shafts. Side links of the inner hair cell (IHC) stereocilia had a similar filamentous appearance, but were observed less commonly and had decreased structural organization compared to those of the OHC stereocilia. Ultrastructural analysis of OHC and IHC stereocilia showed that a large number of the side links could survive acoustic stimulation of 114 dB SPL for 2 hrs or 123 dB SPL for 15 min, that resulted in temporarily elevated hearing thresholds in all animals. Disarray, separation, close attachment and fusion of stereocilia were more frequently observed for IHC stereocilia and OHC stereocilia that were poorly connected or that lacked side links. Most disarrayed OHC and IHC stereocilia recovered to a normal erect state with restored orientation of the side links after 14-28 days, which correlated with near-complete recovery of auditory sensitivity. However, direct attachment of plasma membranes, ruptured links, fusion and blebs were seen on some stereocilia even after 28 days and appear to be permanent.

Structure of outer hair cell stereocilia side and attachment links in the chinchilla cochlea

The structure and symmetry of chinchilla outer hair cell (OHC) stereocilia side and attachment links were investigated by transmission electron microscopy using tannic acid and Cuprolinic blue histochemical procedures. The side links run laterally between and across the rows of the stereocilia and connect the stereocilia together within the bundle. Attachment links form a crown-like array around the tips of only the tallest OHC stereocilia and attach these stereocilia to the Type B fibrils of the tectorial membrane. Computer averaging of the side links from tannic acid-treated tissues showed a central dense region of the link between adjacent stereocilia and a smaller dense portion at the plasma membrane end of the link. Computer averaging of Cuprolinic blue-treated tissues showed low electron density of the central region of the link, and the plasma membrane ends of the link were electron dense. After tannic acid treatment, the attachment links showed a diffused radial distribution around the tips of the tallest OHC stereocilia. After Cuprolinic blue treatment, the attachment links appeared as electron-dense, membrane-bound granular structures arranged with radial symmetry. The central regions of the side links are reactive to tannic acid. These regions appear to contain neutral and basic residues of proteins and participate in side-by-side association of the side links in regular aggregates. Cuprolinic blue-reactive regions of the side and attachment links appear to contain acidic sulfated residues of glycoproteins or proteoglycans, which may be involved in the attachment of these links to the stereocilium membrane.

Proteoglycan arrays in the cochlear basement membrane

Indirect immunofluorescence and transmission electron microscopy were used to investigate the composition and assembly of proteoglycans in the basement membranes of the spiral limbus, basilar membrane, spiral ligament, Reissner's membrane, myelinated nerve fibers, and blood capillaries of the spiral ligament and stria vascularis in the chinchilla cochlea. Four types of basement membrane components: laminin, entactin/nidogen, type IV collagen and heparan sulfate proteoglycans were immunolocalized in all basement membranes in association with heparan sulfate proteoglycans. beta 1 and alpha 1 integrin subunits were also detected along these basement membranes. The concentration of the basement membrane-associated proteins and integrin subunits differed according to the adjacent cell type. Electron microscopy showed that all basement membranes, with exception of those of stria vascularis, consist of two layers: lamina lucida and lamina densa. In the stria vascularis only a homogeneous lamina densa was observed. Cuprolinic blue treatment revealed heterogeneity in the ultrastructure and arrangement of proteoglycans in the cochlear basement membranes. Proteoglycans of the subepithelial basement membrane in the spiral limbus and spiral ligament formed quasi-regular, linear arrays within the lamina lucida, or were located at both sides of the lamina densa in the basilar membrane and Reissner's membrane. In the basement membranes of nerve fibers, and capillaries in the spiral ligament and stria vascularis, proteoglycans were scattered throughout these basement membranes, but showed different concentration and ultrastructural appearance, which may be related to different filtration and mechanical properties. In the basilar membrane, PGs were located above and below the lamina densa. An additional layer of PGs below the lamina densa may function as increased mechanical support of organ of Corti by its interaction with underlying fibrillar collagen layer. In the stria vascularis capillaries, PGs were stained considerably less with Cuprolinic blue and were scattered through the lamina densa of the basement membrane compared to capillaries of spiral ligament. This observation is compatible with a higher permeability of the strial capillaries.

Characterization of mucins in human middle ear and Eustachian tube

Mucins are important glycoproteins in the mucociliary transport system of the middle ear and Eustachian tube. Little is known about mucin expression within this system under physiological and pathological conditions. This study demonstrated the expression of MUC5B, MUC5AC, MUC4, and MUC1 in the human Eustachian tube, whereas only MUC5B mucin expression was demonstrated in noninflamed middle ears. MUC5B and MUC4 mucin genes were upregulated 4.2- and 6-fold, respectively, in middle ears with chronic otitis media (COM) or mucoid otitis media (MOM). This upregulation of mucin genes was accompanied by an increase of MUC5B- and MUC4-producing cells in the middle ear mucosa. Electron microscopy of the secretions from COM and MOM showed the presence of chainlike polymeric mucin. These data indicate that the epithelium of the middle ear and Eustachian tube expresses distinct mucin profiles and that MUC5B and MUC4 mucins are highly produced and secreted in the diseased middle ear. These mucins may form thick mucous effusion in the middle ear cavity and compromise the function of the middle ear.

Structure of outer hair cell stereocilia links in the chinchilla

The structure of side, tip, and "attachment" links of chinchilla outer hair cell (OHC) stereocilia was studied by transmission and scanning electron microscopy using tannic acid and Cuprolinic blue histochemical procedures. Tannic acid, which interacts with many different types of proteins and glycoproteins irrespective of their electrical charge, showed strong reactivity for the central area of the side links and weak reactivity for the marginal area of these links adjacent to the stereocilia membrane. Tannic acid treatment revealed the tip links as thin strands, about 5 nm thick. Attachment links were poorly visualized after tannic acid treatment and appeared as sparse filamentous strands at tips of the tallest OHC stereocilia. Cuprolinic blue, at a high critical electrolyte concentration, reacted with strongly negative, primarily sulfated, carbohydrate residues of glycoconjugate macromolecules. In contrast to the tannic acid treatment, the central portions of the OHC stereocilia side links were unstained after Cuprolinic blue treatment; however, membrane-associated ends of these links were darkly stained. The tip links showed a similar appearance as after tannic acid treatment; however, Cuprolinic blue revealed an electron-dense substructure at both ends of its insertion into the stereocilia. Cuprolinic blue reactive structures were also observed as attachment links only at the tips of the OHC stereocilia of the tallest row in each bundle. These structures formed a crown-like array around the tip of each stereocilium. Their primary function appears to be attachment of type B fibrils of the tectorial membrane to the tallest OHC stereocilia. Cuprolinic blue reactive structures of the side, tip, and attachment links appear to contain acidic, sulfated residues of proteoglycans or glycoproteins. These structures may function as connective elements between the stereocilia links and the hair cell cytoskeleton.

Helical structure of hair cell stereocilia tip links in the chinchilla cochlea

Outer-hair-cell stereocilia tip-link structure in the chinchilla cochlea was studied by transmission electron microscopy using tannic acid and Ruthenium red/ Alcian blue histochemical procedures. Tannic acid and Ruthenium red/Alcian blue treatments showed the tip link as a compact strand of filaments 9-12 nm thick. Fourier analysis of tip-link images showed that the strand is a three-start helical bundle of fine, coiled filaments which had an axial period of 22.5+/-1.5 nm. Each of three coiled filaments in the strand showed globular structures, 4.3+/-0.3 nm in diameter. The globular structures may correspond to individual protein subunits or they may be repeating identical domains of one polypeptide. The three filaments of the helical array may provide a rigidity to the tip link during stereocilia deflections. Alternatively, changes in the subunit or domain structure of each filament may result in a lengthening or shortening of the tip-link strand.

Ultrastructure and immunohistochemical identification of the extracellular matrix of the chinchilla cochlea

The molecular composition and three-dimensional organization of the extracellular matrix (ECM) was studied by immunofluorescent microscopy, transmission and scanning electron microscopy in three connective tissue structures of the cochlea: the spiral limbus, basilar membrane and spiral ligament. Type II collagen, fibronectin, tenascin, chondroitin sulfate proteoglycans, alphav and beta1 integrins were immunolocalized in the ECM of these connective tissue structures. Electron micrographs showed a continuum of cross-striated collagen fibrils having a similar diameter and axial periodicity that spread from the spiral limbus via the basilar membrane and into the spiral ligament. Some of collagen fibrils were aggregated laterally into bundles. Bundle images, and their digital Fourier transformations, showed a major 67-nm axial D-repeat characteristic for collagen fibrils. Transmission electron microscopy showed numerous proteoglycans associated with the collagen fibrils. The spiral limbus, basilar membrane and spiral ligament demonstrated regional differences in molecular composition and structural organization of their ECM. The glycoproteins fibronectin, tenascin and alphav integrin were immunolocalized mainly in the basilar membrane. Collagen fibrils of the spiral limbus and spiral ligament did not appear to be strongly oriented. However, most of the collagen fibrils in the basilar membrane were arranged into radially directed bundles. Collagen fibrils in the basilar membrane were also surrounded by a homogeneous matrix, which was immunoreactive to fibronectin and tenascin antibodies. A more complete understanding of the composition and structural organization of the ECM in these connective tissue structures in the cochlea provides a foundation upon which micromechanical models of cochlear function can be constructed.

Ultrastructural organization of proteoglycans and fibrillar matrix of the tectorial membrane

The molecular and supramolecular structure of the tectorial membrane (TM) was studied by transmission electron microscopy (TEM). Collagen (type A) fibrils in the TM were found associated with proteoglycans (PGs) and type B fibrils. Most PGs were orthogonally oriented and attached D-periodically to collagen fibrils. Computer averaged projections of PG particles and linear aggregates of PGs in crystalline arrays, stained with Cuprolinic blue, showed an elongated, electron-dense structure 50-65 nm in length and 10 nm in width. Image analysis of type B fibrils showed that they are constructed of globular domains arranged with a periodicity of 12-14 nm. Each globular domain contains two thin 'arms', extended in opposite directions, which contact the 'arms' of adjacent fibrils. Numerous type B fibrils were found between collagen fibrils. They are attached to adjacent collagen fibrils by the 'arms' of their globular domains. An association of type B fibrils and PGs with collagen seems to result in the local ordered arrangement of the TM matrix. A hypothetical model of the TM matrix supramolecular structure is presented.

Crystalline arrays of proteoglycan and collagen in the tectorial membrane

Ultrastucture of the tectorial membrane in the chinchilla cochlea was studied by transmission electron microscopy using different fixatives and staining procedures. It was shown that the tectorial membrane is a highly structured matrix composed of collagen type A fibrils, noncollagenous type B fibrils and proteoglycan. The localization of type B fibrils surrounding bundles of parallel type A fibrils was observed. Staining of the tectorial membranes with the cationic dye Cuprolinic blue in a "critical electrolyte concentration" method revealed proteoglycan, D-periodically associated with collagen type A fibrils and orthogonal to them. The appearance and size of the proteoglycan, and its binding to collagen, were similar to small proteoglycans observed in cartilage and other tissues. In many regions of the tectorial membrane the collagen-bound proteoglycan forms crystalline-like arrays. The images of these arrays processed by Fourier analysis show long linear aggregates of proteoglycan arranged parallel each other.

Electron microscopy of Bacillus subtilis GroESL chaperonin and interaction with the bacteriophage phi 29 head-tail connector

The Bacillus subtilis GroESL chaperonin was isolated by sucrose density gradient centrifugation and the constituent GroES and GroEL moieties were purified by electrophoresis in agarose. Electron microscopic images of negatively stained GroEL and GroES oligomers and GroESL complexes were averaged using a reference-free alignment method. The GroEL and GroES particles had the sevenfold symmetry characteristic of their Escherichia coli counterparts. GroESL complexes, reconstituted efficiently in vitro from GroEL and GroES in the absence of added ADP or ATP, had the characteristic bullet- and football-like shapes in side view. Purified bacteriophage phi 29 head-tail connectors having a mass in excess of 0.4 MDa were shown to bind to GroESL at the end opposite to the GroES. The same GroESL-connector complexes were isolated from phage-infected cells in which capsid assembly was blocked, and thus the complex may have functional significance in phi 29 morphogenesis.

The bacteriophage phi 29 head-tail connector shows 13-fold symmetry in both hexagonally packed arrays and as single particles

The symmetry of the phi 29 head-tail connector is controversial: several studies of two-dimensional arrays of the connector have found a 12-fold symmetry, while a recent study of isolated particles has found a 13-fold symmetry. To investigate whether a polymorphism of the structure might explain these different results, electron microscopy and image analysis were used to study both isolated connectors and particles in hexagonally packed arrays. The hexagonally packed arrays have a P1 symmetry, and the connectors displayed 13 subunits both in the arrays and as isolated single particles. While we do not observe a polymorphism between connectors in two-dimensional arrays and as isolated particles, data show that the connectors can exist with either 12 or 13 subunits. A three-dimensional reconstruction of our 13-fold connector was generated by combining an averaged side-view projection with the known symmetry. The structure of rosettes of the connectors formed in the presence of phi 29 prohead RNA (pRNA) was also examined. These rosettes contain five connectors arranged about a single connector in the center, and this arrangement may reflect an essential role of the pRNA in mediating a symmetry mismatch between either a 12- or 13-fold symmetric connector and a putative fivefold symmetric prohead portal vertex into which the connector fits.