The purpose of this study is to describe polyp formation in the mucosa of the middle ear as a possible model for the pathogenesis of nasal polyps. In 65 Wistar rats, the eustachian tube was occluded on the left side for up to 20 months; 60 right-sided, nonoccluded ears served as controls. Following occlusion, the middle ear mucosa was examined for signs of polyps. Signs of polyp formation or fully developed polyps were seen in 14 (22%) of the middle ears, and were only seen in middle ears with signs of actual or previous infection. It was established that the first stages of polyp formation include epithelial rupture, proliferation of fibrous tissue through the epithelial defect, and epithelialization of the prolapsed fibrous tissue by proliferation and migration of epithelial cells from the surrounding epithelium until there is full epithelial covering of the polyp. This report discusses whether the described middle ear model may form basis for the explanation of the pathogenesis of nasal polyps.
The biocompatibility of porous implants made of Estane 5714 F1 polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer (HPOE/PBT copolymer), which were selected as candidates for an alloplastic tympanic membrane, was assessed after implantation in rat middle ears for periods of up to 1 year. Implantation of the materials led to tissue reactions initially associated with the wound-healing process, whereas after 1 month not only the presence of macrophages and foreign-body giant cells surrounding the implant materials but also implant degradation were characteristic for a foreign-body reaction. Macrophages and foreign-body giant cells dominated the picture of the tissue surrounding polypropylene oxide. The altered morphology of these cells, the persistent infiltration of the implantation sites by exudate cells, and the premature death of five rats in the 1-year group suggest that polypropylene oxide degradation was accompanied by the release of toxic substances. Estane and copolymer degradation did not induce tissue responses reflecting implant toxicity, and tympanic membranes given these alloplasts showed a normal healing pattern. Inclusions in the cytoplasm of macrophages associated with degradation and phagocytosis of all of the polymers under study were found to contain iron, silicon, titanium, and aluminum. Growth of fibrous tissue and bone, the latter into Estane and HPOE/PBT copolymer implants, indicated appropriate implant fixation by tissue, although macrophages and foreign-body giant cells were present as well. Especially the fixation of copolymer by ingrowth of bone seems promising in terms of the amount of bone in the pores and the electron-dense bone/copolymer interface. The latter is indicative for bonding osteogenesis. The HPOE/PBT copolymer is a better candidate for alloplastic tympanic membrane than Estane, and the use of polypropylene oxide cannot be recommended.
This study examined the presence of NaK-ATPase isoforms in the developing inner ear of the rat and studied the importance of functional subunit combinations in endolymph homeostasis. The findings were: (a) the combination alpha 1 beta 1 is found in epithelial, mesenchymal, and neural inner ear cells with an early starting expression 14 days postconception (dpc) in some endolymphatic sac cells; (b) from 1 day after birth (dab) expression of alpha 1 beta 2 is observed in marginal cells, vestibular dark cells, and certain vestibular nonsensory cells; (c) a transient expression of alpha 2 beta 1 is found in suprastrial fibrocytes and spiral ligament fibrocytes type II between 10 and 15 dab; (d) starting at 16 dpc the combination alpha 3 beta 1 is uniquely expressed in inner ear neural cells (as in other neural tissues). In conclusion, during development a switch from alpha 2 beta 1 towards alpha 1 beta 1 is observed in suprastrial fibrocytes and in spiral ligament fibrocytes type II. Thus, according to the biochemical characteristics of these combinations, a switch towards a NaK-ATPase with higher capacity takes place. In addition, prominent expression of the alpha 1 beta 2 combination in predominantly K+ ion transporting marginal and dark cells is in accordance with the characteristic of this combination and thus with the presumed function of these cells as important K+ suppliers for the endolymph. We believe this combination in certain vestibular nonsensory cells to be involved in K+ sensing. Early expression of the alpha 1 beta 1 combination in the endolymphatic sac, prior to that in the other parts of the inner ear, suggests that this structure may be involved to some extent in the development of the vestibulum and cochlea.
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