Linking the Mechanics of Chewing to Biology of the Junctional Epithelium

The capacity of a tissue to continuously alter its phenotype lies at the heart of how an animal is able to quickly adapt to changes in environmental stimuli. Within tissues, differentiated cells are rigid and play a limited role in adapting to new environments; however, differentiated cells are replenished by stem cells that are defined by their phenotypic plasticity. Here we demonstrate that a Wnt-responsive stem cell niche in the junctional epithelium is responsible for the capability of this tissue to quickly adapt to changes in the physical consistency of a diet. Mechanical input from chewing is required to both establish and maintain this niche. Since the junctional epithelium directly attaches to the tooth surface via hemidesmosomes, a soft diet requires minimal mastication, and consequently, lower distortional strains are produced in the tissue. This reduced strain state is accompanied by reduced mitotic activity in both stem cells and their progeny, leading to tissue atrophy. The atrophied junctional epithelium exhibits suboptimal barrier functions, allowing the ingression of bacteria into the underlying connective tissues, which in turn trigger inflammation and mild alveolar bone loss. These data link the mechanics of chewing to the biology of tooth-supporting tissues, revealing how a stem cell niche is responsible for the remarkable adaptability of the junctional epithelium to different diets.

Wnt/β-catenin Signaling Controls Maxillofacial Hyperostosis

The roles of Wnt/β-catenin signaling in regulating the morphology and microstructure of craniomaxillofacial (CMF) bones was explored using mice carrying a constitutively active form of β-catenin in activating Dmp1-expressing cells (e.g., daβcatOt mice). By postnatal day 24, daβcatOt mice exhibited midfacial truncations coupled with maxillary and mandibular hyperostosis that progressively worsened with age. Mechanistic insights into the basis for the hyperostotic facial phenotype were gained through molecular and cellular analyses, which revealed that constitutively activated β-catenin in Dmp1-expressing cells resulted in an increase in osteoblast number and an increased rate of mineral apposition. An increase in osteoblasts was accompanied by an increase in osteocytes, but they failed to mature. The resulting CMF bone matrix also had an abundance of osteoid, and in locations where compact lamellar bone typically forms, it was replaced by porous, woven bone. The hyperostotic facial phenotype was progressive. These findings identify for the first time a ligand-independent positive feedback loop whereby unrestrained Wnt/β-catenin signaling results in a CMF phenotype of progressive hyperostosis combined with architecturally abnormal, poorly mineralized matrix that is reminiscent of craniotubular disorders in humans.

Histopathological features in fatal COVID-19 acute respiratory distress syndrome

Background

COVID-19 acute respiratory distress syndrome (ARDS) shares the common histological hallmarks with other forms of ARDS. However, the chronology of the histological lesions has not been well established.

Objective

To describe the chronological histopathological alterations in the lungs of patients with COVID-19 related ARDS.

Design

A prospective cohort study was carried out.

Setting

Intensive Care Unit of a tertiary hospital.

Patients

The first 22 consecutive COVID-19 deaths.

Measurements

Lung biopsies and histopathological analyses were performed in deceased patients with COVID-19 related ARDS. Clinical data and patient course were evaluated.

Results

The median patient age was 66 [63–74] years; 73% were males. The median duration of mechanical ventilation was 17 [8–24] days. COVID-19 induced pulmonary injury was characterized by an exudative phase in the first week of the disease, followed by a proliferative/organizing phase in the second and third weeks, and finally an end-stage fibrosis phase after the third week. Viral RNA and proteins were detected in pneumocytes and macrophages in a very early stage of the disease, and were no longer detected after the second week.

Limitation

Limited sample size.

Conclusions

The chronological evolution of COVID-19 lung histopathological lesions seems to be similar to that seen in other forms of ARDS. In particular, lung lesions consistent with potentially corticosteroid-sensitive lesions are seen.

Histopathological features in fatal COVID-19 acute respiratory distress syndrome

Background

COVID-19 acute respiratory distress syndrome (ARDS) shares the common histological hallmarks with other forms of ARDS. However, the chronology of the histological lesions has not been well established.

Objective

To describe the chronological histopathological alterations in the lungs of patients with COVID-19 related ARDS.

Design

A prospective cohort study was carried out.

Setting

Intensive Care Unit of a tertiary hospital.

Patients

The first 22 consecutive COVID-19 deaths.

Measurements

Lung biopsies and histopathological analyses were performed in deceased patients with COVID-19 related ARDS. Clinical data and patient course were evaluated.

Results

The median patient age was 66 [63–74] years; 73% were males. The median duration of mechanical ventilation was 17 [8–24] days. COVID-19 induced pulmonary injury was characterized by an exudative phase in the first week of the disease, followed by a proliferative/organizing phase in the second and third weeks, and finally an end-stage fibrosis phase after the third week. Viral RNA and proteins were detected in pneumocytes and macrophages in a very early stage of the disease, and were no longer detected after the second week.

Limitation

Limited sample size.

Conclusions

The chronological evolution of COVID-19 lung histopathological lesions seems to be similar to that seen in other forms of ARDS. In particular, lung lesions consistent with potentially corticosteroid-sensitive lesions are seen.

A Comparative Assessment of Implant Site Viability in Humans and Rats

Our long-term objective is to devise methods to improve osteotomy site preparation and, in doing so, facilitate implant osseointegration. As a first step in this process, we developed a standardized oral osteotomy model in ovariectomized rats. There were 2 unique features to this model: first, the rats exhibited an osteopenic phenotype, reminiscent of the bone health that has been reported for the average dental implant patient population. Second, osteotomies were produced in healed tooth extraction sites and therefore represented the placement of most implants in patients. Commercially available drills were then used to produce osteotomies in a patient cohort and in the rat model. Molecular, cellular, and histologic analyses demonstrated a close alignment between the responses of human and rodent alveolar bone to osteotomy site preparation. Most notably in both patients and rats, all drilling tools created a zone of dead and dying osteocytes around the osteotomy. In rat tissues, which could be collected at multiple time points after osteotomy, the fate of the dead alveolar bone was followed. Over the course of a week, osteoclast activity was responsible for resorbing the necrotic bone, which in turn stimulated the deposition of a new bone matrix by osteoblasts. Collectively, these analyses support the use of an ovariectomy surgery rat model to gain insights into the response of human bone to osteotomy site preparation. The data also suggest that reducing the zone of osteocyte death will improve osteotomy site viability, leading to faster new bone formation around implants.

Mechanoresponsive Properties of the Periodontal Ligament

The periodontal ligament (PDL) functions as an enthesis, a connective tissue attachment that dissipates strains created by mechanical loading. Entheses are mechanoresponsive structures that rapidly adapt to changes in their mechanical loading; here we asked which features of the PDL are sensitive to such in vivo loading. We evaluated the PDL in 4 physiologically relevant mechanical environments, focusing on mitotic activity, cell density, collagen content, osteogenic protein expression, and organization of the tissue. In addition to examining PDLs that supported teeth under masticatory loading and eruptive forces, 2 additional mechanical conditions were created and analyzed: hypoloading and experimental tooth movement. Collectively, these data revealed that the adult PDL is a remarkably quiescent tissue and that only when it is subjected to increased loads—such as those associated with mastication, eruption, and orthodontic tooth movement—does the tissue increase its rate of cell proliferation and collagen production. These data have relevance in clinical scenarios where PDL acclimatization can be exploited to optimize tooth movement.

Acoustic neuromas presenting with symptoms of morbus Menière

If a patient with Menière's disease or a sudden deafness does not respond to adequate therapy, an acoustic neuroma should be excluded. This is achieved by a positive contrast cisternography using multidirectional tomography. The examples might have shown that sometimes acoustic neuromas present with atypical symptoms, with sudden deafness or even with the typical symptoms of morbus menière.

A pre-clinical murine model of oral implant osseointegration

Many of our assumptions concerning oral implant osseointegration are extrapolated from experimental models studying skeletal tissue repair in long bones. This disconnect between clinical practice and experimental research hampers our understanding of bone formation around oral implants and how this process can be improved. We postulated that oral implant osseointegration would be fundamentally equivalent to implant osseointegration elsewhere in the body. Mice underwent implant placement in the edentulous ridge anterior to the first molar and peri-implant tissues were evaluated at various timepoints after surgery. Our hypothesis was disproven; oral implant osseointegration is substantially different from osseointegration in long bones. For example, in the maxilla peri-implant pre-osteoblasts are derived from cranial neural crest whereas in the tibia peri-implant osteoblasts are derived from mesoderm. In the maxilla, new osteoid arises from periostea of the maxillary bone but in the tibia the new osteoid arises from the marrow space. Cellular and molecular analyses indicate that osteoblast activity and mineralization proceeds from the surfaces of the native bone and osteoclastic activity is responsible for extensive remodeling of the new peri-implant bone. In addition to histologic features of implant osseointegration, molecular and cellular assays conducted in a murine model provide new insights into the sequelae of implant placement and the process by which bone is generated around implants.

[T-cartilage tympanoplasty for an open oval window]

A T shaped cartilage, placed into the open oval window, functions as a stapes. The transvers part of the T prevents a too deep insertion into the vestibule. If necessary small stripes of connective tissue seal the vestibule.

[Short and long term results of endolymphatic sac surgery: a patient-questionnaire based study]

INTRODUCTION

The endolymphatic sac surgery for the treatment of Meniere's disease has been described since the 1920s. The success rate of this technique in terms of vertigo control has been reported to be 50-80%. However, the value of this treatment method remained controversial. Furthermore, the reliable identification of the endolymphatic sac intraoperatively can be challenging in some cases. This study examines the short-, middle- and long-term results in a larger cohort of patients.

MATERIALS AND METHODS

In 74 patients, vertigo control, tinnitus and degree of satisfaction was evaluated by means of a questionnaire retrospectively. Additionally, the diagnostic value of the electrocochleography (EcochG) was determined.

RESULTS

The overall vertigo control rate was more than 70% in patients followed up for two years and has reached 81% in patients followed up for more than two years. Hearing preservation rate was 61%. Tinnitus has disappeared in 11% and improved in 23% of the patients. In 47% of the patients it was unchanged and in 19% worsened. The difference in EcochG results pre- versus postoperative was highly significant.

CONCLUSIONS

ELSS is a useful tool in the management of Ménière's disease, in particular in patients that do not benefit sufficiently from conservative therapy.

[Results in otosurgically treated patients with acoustic neuroma. Part 1: Facial nerve function after translabyrinthine and middle fossa resection]

BACKGROUND

Regardless of all efforts to preserve a residual hearing, facial nerve function is still the primary issue for patients with acoustic neuromas. Since alternative methods like the gamma-knife treatment are of increasing importance, results after surgery have to be compared and discussed critically.

PATIENTS

The results of 538 patients operated at the Dept. of Otolaryngology, Head and Neck Surgery, University of Wuerzburg between 1989 and 2004 are presented. 392 had surgery via a middle fossa, 146 via a translabyrinthine approach.

RESULTS

Shortly after surgery 82.2 % of patients showed no facial palsy. 74 patients had an incomplete, 7 a complete paresis. After 12 months 144 of the patients operated on via middle fossa approach showed no palsy, 13 had an incomplete and one a complete paresis. Out of 76 patients operated on translabyrinthine approach 75 had no paresis, one had an incomplete, and no patient had a complete paresis. There was no difference between intrameatal tumors and tumors extending beyond the porus. Regular facial nerve function was seen in 93 %, postoperatively. Permanent paresis was seen in 0.4 % of cases.

CONCLUSION

Acoustic neuroma confined to the internal meatus or with minor extension into the cerebello-pontine angle (i. e. no contact to structures of the brain stem or vessels of the posterior fossa) are feasible for resection via a middle fossa or translabyrinthine approach. The possibility of hearing preservation combined with low morbidity and good results of facial nerve function makes these approaches the treatment of choice for this group of tumors.

Klinische und audiologische Befunde von Kindern mit auditorischer Neuropathie und ihre Versorgung mit einem Cochlea-Implantat

BACKGROUND

Auditory neuropathy is a disorder characterised by preservation of outer hair cells function with normal otoacoustic emissions (OAEs), but with absent auditory brainstem responses (ABR). Perisynaptic synchronisation disorder is one of the possible pathogenesis underlying auditory neuropathy. In this paper we describe the clinical presentation and audiological findings in pediatric auditory neuropathy and its management.

PATIENTS AND METHODS

9 children with auditory neuropathy could be included in the study. An audiological evaluation was performed in all children including behavioural audiometry, measurement of the OAEs as well as electrocochleography (ECoG) and ABR recordings. Children who failed to get any benefit from conventional amplification received a cochlear implant. Prior to implantation the responses to electrical stimuli were examined with the promontory test and with the electrically evoked ABR.

RESULTS

One child showed auditory neuropathy only on one side with normal hearing thresholds on the contralateral ear. Another child had normal hearing thresholds after the follow up period. Four children received a hearing aid. But variable hearing reactions were observed. Thus in three cases a CI is planned. In three children cochlea implantation was done. Following implantation a remarkable improvement in hearing/speech capabilities with the CI compared to conventional hearing aids were observed in all three cases. Beside, these three children developed open set speech discrimination and are using now oral language for communication.

CONCLUSIONS

Auditory neuropathy is a disorder which presents with different clinical and audiological findings. Thus the management of this disorder must be an individual one. In light of our findings we support the use of cochlear implants as an option for children with auditory neuropathy in cases where conventional amplification does not work sufficiently.

Analyzing the cellular contribution of bone marrow to fracture healing using bone marrow transplantation in mice

The bone marrow is believed to play important roles during fracture healing such as providing progenitor cells for inflammation, matrix remodeling, and cartilage and bone formation. Given the complex nature of bone repair, it remains difficult to distinguish the contributions of various cell types. Here we describe a mouse model based on bone marrow transplantation and genetic labeling to track cells originating from bone marrow during fracture healing. Following lethal irradiation and engraftment of bone marrow expressing the LacZ transgene constitutively, wild type mice underwent tibial fracture. Donor bone marrow-derived cells, which originated from the hematopoietic compartment, did not participate in the chondrogenic and osteogenic lineages during fracture healing. Instead, the donor bone marrow contributed to inflammatory and bone resorbing cells. This model can be exploited in the future to investigate the role of inflammation and matrix remodeling during bone repair, independent from osteogenesis and chondrogenesis.

[Development of a new test for speech audiometry in children and results in CI children]

BACKGROUND

Speech audiometry plays an important role for hearing evaluation in children. Hearing impaired children, such as those with cochlear implant (CI) who frequently undergo testing, learn the test words by heart. Furthermore, the standard tests use words of former time.

PATIENTS AND METHODS

Using the most frequently words of modern children's literature a speech assessment test was developed for children between 1 to 8 years. The material was first evaluated on normal hearing children. In a second step the phoneme and word perception scores of 35 CI children were measured using 60 - 100 dB SPL according to the most comfortable level (MCL) in free sound field.

RESULTS

The performance-intensity function for the single words were highly comparable with those of the Freiburger or Göttinger speech perception test. The average speech reception threshold in CI children was 44 % (test I), 36 % (test II), 63 % (test III) and 69 % (test IV), respectively. Compared to the Mainzer and Göttinger speech perception test the new words were more difficult to understand than those of the known tests. However, a statistically significant difference could be noted only for test II.

CONCLUSIONS

The new developed "Würzburger speech perception test" appears to be a useful additional tool for the evaluation of hearing impaired children in addition to the standard test procedures.

Sound localization and sensitivity to interaural cues in bilateral users of the Med-El Combi 40/40+cochlear implant system

OBJECTIVE

The purpose of this study was to investigate sound localization in subjects bilaterally implanted with MED-EL COMBI 40/40+ cochlear implants. In addition, the sensitivity to interaural cues was assessed.

METHODS

In the localization test (11 subjects), CCITT noise (500 ms, original and HRTF-filtered, 70/75/80 dB sound pressure level) was presented from one of seven loudspeakers between -90 degrees and 90 degrees azimuth. The subject had to indicate which loudspeaker the noise was presented from. Sensitivity to interaural level differences (ILD) was assessed by performing localization tests (4 subjects) with the loudness of the two speech processors unbalanced to various degrees. To investigate the subjects' sensitivity to interaural time differences (ITD), lateralization was measured (7 subjects) as a function of the time difference between two Gaussian-like pulses, each directed to one of the subject's speech processor microphones by way of headphones.

RESULTS

The judgments of all subjects significantly correlated with the positions of the loudspeakers. The scatter in the judged azimuth measured by the standard deviation of the responses was on average 27.5 degrees . Unbalanced loudness of the speech processors produced a bias in azimuth toward the speech processor with the louder volume setting. The mean rate of shift was 1.4 degrees per unit on the Wuerzburg loudness scale. Six of seven subjects showed a significant sensitivity to ITDs with the approximate time difference required for complete lateralization being 1,200 micros on an average. The one subject not showing a sensitivity to ITDs performed worst in the localization test.

CONCLUSIONS

Bilateral cochlear implantation can restore spatial hearing in cochlear implant users. Both ILDs and ITDs are used by bilateral cochlear implant users in sound localization with ILDs appearing to be the dominant cue.

Bilateral cochlear implants: a way to optimize auditory perception abilities in deaf children?

OBJECTIVES

The Würzburg bilateral cochlear implant (CI) program was started with the aim to improve the patients' communicative abilities in complex listening situations. In this study, the auditory skills of children using bilateral cochlear implants were evaluated.

STUDY DESIGN AND SETTINGS

Qualitative data based on free observations in the rehabilitation setup were collected in 39 bilaterally implanted children. A speech discrimination in noise test was performed in 18 of these children; lists of bisyllabic words were presented in noise at a signal to noise ratio (SNR) of +15 dB.

RESULTS

Qualitative and quantitative data show clearly that bilateral CI improves the children's communicative behaviour, especially in complex listening situations. Children examined with the speech in noise test scored significantly better under the bilateral condition compared to the unilateral condition. Integration of the second implanted side and use of binaural information was observed to be easier and faster in children with a short time lag between both implants.

CONCLUSIONS

To be able to obtain optimal benefit from bilateral cochlear implants, an intensive rehabilitation program is necessary. The important aspects of such a program are creating realistic expectations in older children before implantation; performing the first processor fitting of the second side with the first side switched on; and separate intensive training with the new system in order to balance out the hearing competence of the second CI with that of the first.

Cochlea-Implantation: Ergebnisse und Kosten, eine Übersicht

The cochlear implantation, especially after bilateral operation provides a reliable and outstanding compensation in bilateral complete deafness or severe hearing impairment. Directional hearing can be restored with bilateral implantation so that warning signals are localized correctly and speech in noise is easier understood. Thus, rehabilitation is restored to a high degree. The involved expenses are severe, but are lower for the society when compared to the amount of money necessary to substitute a completely deaf patient lifelong.