W Kuijpers

Radboud University Medical Centre (Radboudumc), Nymegen, Gelderland, Netherlands

Are you W Kuijpers?

Claim your profile

Publications (95)135.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The intention of this study was to investigate the epithelial reactions to hydroxyapatite ceramic in vivo and in vitro. Shortly after implantation in the rat middle ear, hydroxyapatite was found covered by a mucosal layer. In the early postoperative period the implant was almost completely covered by epithelial cells, which were found to proliferate and also showed migratory activity. After longer intervals the implant was completely covered by epithelium, which was composed predominantly of flat polygonal cells and a relatively small number of ciliated epithelium and goblet cells. All cells showed normal morphology. In vitro experiments showed preservation of the morphology of rat middle-ear mucosa explants with good outgrowth of epithelial cells. In these outgrows, the majority of the cells were flat polygonal, but ciliated epithelium was also seen. No difference was found between the absence and presence of hydroxyapatite. Serially cultured cells displayed normal polygonal morphology, but no ciliated cells were found. Ciliated cells were also absent in control experiments without hydroxyapatite. Growth curves obtained in the absence and presence of hydroxyapatite did not differ significantly from each other.
    No preview · Article · Jul 2009 · Acta Oto-Laryngologica
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: It has recently been demonstrated that endolymphatic sac (ES) ribosome-rich (dark) cells respond to induced endolymph changes and are thus likely to be involved in endolymph homeostasis. Therefore, we studied the ultrastructural characteristics of rat ES ribosome-rich cells during development in order to determine the cellular distribution of organelles involved in protein metabolism, secretion and absorption, indicative for their contribution to endolymph homeostasis. During embryonal stages ribosome-rich cells contain a limited number and variety of organelles and are predominantly involved in the production of components for cell growth and differentiation. In the young adult stage (P60) three different states of ribosome-rich cells may be distinguished. State A resembles a cell with only limited metabolic activities whereas state B is characterized by numerous different intracellular organelles and is considered to be involved in production and secretion as well as absorption and degradation of complex proteins. A third cellular state, state C, is filled with phagolysosomes and contains very few other organelles. This is considered to be a final (pre)apoptotic state. Autoradiography data suggest that ES ribosome-rich cells are capable of synthesis and secretion of tyrosine-containing proteins and may thus be involved in regulation of the osmolarity of endolymph based on the capacity to bind cations as well as water molecules. In addition, ES ribosome-rich cells appear to synthesize and secrete fucosylated glycoproteins into the endolymph. In conclusion, the present data suggest that ES ribosome-rich cells are actively involved in endolymph homeostasis through secretion and absorption of complex proteins and it is hypothesized that they are able to adapt their function or activities in response to changes in endolymph composition.
    Full-text · Article · Mar 2003 · Hearing Research

  • No preview · Article · Jan 2003 · Hearing Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of the study was to examine the specific involvement of endolymphatic sac mitochondria-rich cells in endolymph homeostasis. Transmission electron microscopy and immunohistochemistry were performed on the endolymphatic sac of young adult rats, and two important developmental stages were also investigated. Ultrastructural characteristics of endolymphatic sac mitochondria-rich cells were studied more concisely and compared with renal mitochondria-rich cells (i.e., the intercalated cells). In addition, expression of cytokeratins 7 and 19 was determined. Until birth, only one type of mitochondria-rich cell is observed in the rat endolymphatic sac. In young adult animals, distinct differences in mitochondria-rich cell ultrastructure in the endolymphatic sac enables classification into subtypes or configurations. Comparison of endolymphatic sac mitochondria-rich cells with renal intercalated cells reveals striking similarities and provides additional information on their specific function in endolymph homeostasis. Furthermore, differences in cytokeratin expression are determined in endolymphatic sac mitochondria-rich cells. Differences in morphology of endolymphatic sac mitochondria-rich cells develop after birth and may reflect a distinct functional or physiological state of the cell. In analogy to renal intercalated cells, the distribution patterns of H+-adenosine triphosphatase and Cl-/HCO3- exchanger may differ between subtypes. We propose that subtype A mitochondria-rich cells, from which protruding A mitochondria-rich cells are the activated state, are involved in proton secretion (apical H+-adenosine triphosphatase) and thus are potential candidates for hearing loss accompanying renal tubular acidosis. Subtype B mitochondria-rich cells are the most likely candidates to be affected in Pendred syndrome because of the assumed function of pendrin as apical Cl-/HCO3- exchanger.
    Full-text · Article · Apr 2002 · The Laryngoscope
  • Source
    TA Peters · W Kuijpers · J. H. A. J. Curfs
    [Show abstract] [Hide abstract]
    ABSTRACT: 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.
    Full-text · Article · Mar 2001 · Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to determine specific characteristics of endolymphatic sac (ES) cells of the developing rat that are considered to be involved in endolymph homeostasis. Because intermediate filament proteins (IFPs) are regarded as markers of cell differentiation and basal lamina proteins (BLPs) are essential in cell<=>matrix interactions, we determined the presence of IFPs [cytokeratins (CKs) and vimentin] and BLPs [collagen IV, heparan sulphate proteoglycan (HSPG) and laminin] at different developmental stages before and after birth. In addition, we studied the expression of two enzymes of oxidative metabolism: cytochrome oxidase and succinate dehydrogenase. The presence of CKs 8, 18 and 19 in all epithelial cells of the ES during the embryonic stage is characteristic of simple (glandular) epithelial cells. Interestingly, a distinct population of these cells shows additional expression of CK 7, which is a feature of secretory cells. These CK 7-positive cells also contain a high concentration of oxidative enzymes and are rich in mitochondria, indicating that they are light cells. It is suggested that light cells possess specific energy-requiring transport capabilities. Loss of CK 19 expression in the distal part and in a large region of the intermediate part of the ES implies that these cells do not differentiate any further and acquire the capacity to proliferate. Furthermore, prominent co-expression of vimentin with the CKs in the distal part of the ES may confer viscoelastic properties on this epithelium. This may facilitate expansion and thus enable cushioning of pressure fluctuations. Finally, the early prominent occurrence of HSPG in the basal lamina of the ES enables transport of ions. In this light our recent observations of early functioning NaK-ATPases in certain ES cells are interesting.
    Full-text · Article · Jan 2001 · Acta Oto-Laryngologica
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objectives: The assessment of the expression patterns of cytokeratin polypeptides (Cks) and vimentin in normal epithelium of the mobile tongue and floor of the mouth, squamous cell carcinomas and their lymph node metastases. Material and Methods: Chain-specific monoclonal antibodies to various Cks and vimentin were used, employing the immunoperoxidase technique. Results and Conclusions: Profound changes in the expression of pre-existing Cks and de novo expression of simple epithelium-related Cks and of vimentin occurred upon malignant transformation and tumor progression. Changes were mainly related to the degree of cellular differentiation, tumor cell morphology and tumor growth pattern. Low-grade tumors showed a pronounced decrease of the stratification Cks 4 and 13, and an increase of Cks 14, 16, and 17. With increasing tumor grade, expression of Cks 16 and 17 decreased. De novo expression of Cks 8 and 18 and of vimentin was most marked in high-grade tumors, in tumors with a basaloid phenotype and in tumors growing in small infiltrating tumor fields; it was proposed to be associated with poor prognosis.
    No preview · Article · Jan 2001 · Oto-Rhino-Laryngologia Nova
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective To study the effect of various middle ear effusions on the structure of the lamina propria of the tympanic membrane.Methods Sterile and infective middle ear effusions were induced by obstruction of the eustachian tube in specific pathogen-free (SPF) rats and in rats with upper airway infections (URI), respectively. The condition of the tympanic membrane was monitored at regular intervals. After varying survival times, the animals were killed and the tympanic membranes processed for light and electron microscopy.Results Sterile effusions always resulted in tympanosclerotic lesions. These lesions did not develop in the presence of primary-infected effusions. These effusions had a severe destructive effect on the lamina propria, followed by fibrosis. Generally, secondary infection did not markedly affect preexisting tympanosclerotic lesions. Moreover, calcification disappeared when re-aeration of the middle ear occurred, but the abnormal collagen depositions persisted.Conclusions Both sterile and infective effusions result in comprehensive irreversible changes in the lamina propria of the pars tensa. The development of tympanosclerosis is confined to sterile effusions. Mechanical injury and compromised vascularization of the lamina propria are likely to be important etiological factors in the development of tympanosclerosis.
    Full-text · Article · Dec 2000 · The Laryngoscope
  • J. J. S. Mulder · W Kuijpers
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to evaluate the anatomy of the eustachian tube (ET) of the rat and the paratubal musculature. Microdissection and serial sections were used. The ET consists of collapsible membranous and membranocartilaginous segments and a noncollapsible bony segment. Tubal muscles are attached to the collapsible part; the salpingopharyngeus muscle (SPM) is well developed and consists of 3 distinct groups of muscle fibers; the tensor veli palatini muscle (TVPM) consists of 2 functionally different groups of fibers, but only 1 group assists in opening the ET. Attachment of the fibers of the SPM and TVPM that are involved in tubal opening is confined to the dorsal portion of the ET. This finding, together with the earlier observation that this part is mainly lined by squamous epithelium, strongly suggests that the dorsal part has a ventilatory function. The ventral portion of the ET, which is lined by ciliated-secretory epithelium and lacks the attachment of muscle fibers that can dilate the lumen, is assumed to serve clearance. The anatomic position of the levator veli palatini muscle suggests that this muscle contributes to the protective function of the ET. These findings are discussed with regard to the ET in humans.
    No preview · Article · Apr 1999 · The Annals of otology, rhinology, and laryngology
  • W Kuijpers · TA Peters · E.L.G.M Tonnaer
    [Show abstract] [Hide abstract]
    ABSTRACT: The nature of the insertion of the tympanic membrane into the tympanic bone was studied in the rat during the developmental period ranging from 18 days post conception (dpc) to 40 days after birth (dab). Techniques applied were light microscopy, electron microscopy and immunohistochemistry with antibodies to cytoskeletal proteins: vimentin, desmin and alpha-smooth muscle actin (sma) as fibroblast differentiation markers. It was established that the cartilaginous annulus of the pars tensa was connected to the tympanic bone by an interface of specialised connective tissue. Both the fibrocartilage and the interface were derived from the embryonal mesenchyme between the tympanic ring and meatal plate. Electron microscopy showed that the interface was composed of two types of fibroblast. The majority of these cells were myofibroblasts, which were interconnected by junctions and had intimate contact with the collagenous fibres. A small number were identified as genuine fibroblasts. Cytoskeletal characterisation revealed the presence of three types of cell: V cells which expressed vimentin, VA cells which expressed vimentin and alpha-sma and VAD cells which expressed vimentin, alpha-sma and desmin. The myofibroblasts expressed antigens of both smooth muscle cells (alpha-sma, desmin) and connective tissue cells (vimentin). It is suggested that the pars tensa is connected to the tympanic bone by a network of contractile cells and fibres. Contraction will move the membrane in an outward direction and antagonise the inward retraction by the tensor tympani.
    No preview · Article · Mar 1999 · Hearing Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Immunohistochemistry with monospecific antibodies was used to study the expression patterns of cytokeratins (Cks) and vimentin in non-dysplastic lesions of the oral cavity, including lichen planus and fibromas. In hyperplastic lesions, Ck expression did not deviate significantly from the normal non-keratinizing squamous epithelium of the oral cavity. Hyperkeratotic lesions showed pronounced aberrations in their Ck profile. These lesions were characterized by extended expression of the keratinization marker Ck 10, the basal cell Ck 14 and the hyperproliferation-associated Ck 16 in the suprabasal compartment. The stratification markers Cks 4 and 13 showed a decreased expression. Coexpression of Cks and vimentin was found in lesions having accumulations of inflammatory cells in the subepithelial cell layer. These changes are felt to characterize benign mucosal lesions without dysplasia and might be helpful for distinguishing these lesions from potentially malignant ones.
    Full-text · Article · Feb 1999 · Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To investigate the relationship between the anatomical maturation of the middle ear and that of the eustachian tube and paratubal muscles in the rat. Design: Wistar rats ranging from gestational day 12 to postnatal day 40 were used. Methods: Tissue specimens were examined with routine light microscopy and electron microscopy. Epithelial differentiation was studied immunohistochemically with antibodies to different cytokeratins. Results: The epithelial lining of the tubotympanum showed differentiation-related cytokeratin expression throughout the whole developmental period. The mucociliary epithelium reached mature features around birth. A dorsal extension and its framing cartilage started forming around 5 days after birth. This extension became lined by stratified nonciliated epithelium and attained maturity around 10 days after birth concurrently with the attachment of the dilatory muscles. This process was immediately followed by aeration of the middle ear cavity. Conclusions: The continuous expression of cytokeratins demonstrates that the epithelial lining of the tubotympanum is only derived from the embryonal endoderm. Furthermore, this study demonstrates that the eustachian tube shows a two-stage postnatal development. First, the mucociliary system matures, providing protection/clearance when the animal starts respiration and swallowing. Subsequently, the dorsal part attains maturity. The features of the epithelial lining of the dorsal part of the eustachian tube and the coincidence of the maturation of this part with the attachment of the dilating muscle fibers and the aeration of the middle ear indicates that this part provides ventilation. These findings support the authors' hypothesis that different parts of the eustachian tube serve different purposes: clearance, protection and ventilation.
    Full-text · Article · Nov 1998 · The Laryngoscope
  • [Show abstract] [Hide abstract]
    ABSTRACT: ZusammenfassungVom histologischen Aufbau der Eustachi-Röhre können deren Grundfunktionen (Schutz, Reinigung und Belüftung) abgeleitet werden. Neuere systematische histologische und Mikroschnittuntersuchungen sowie embryologische Untersuchungen zur Entwicklung der Tuba auditiva führten zu Ergebnissen, die unsere Einsicht in die Funktion der Eustachi-Röhre vertieft haben. Diese Befunde sind: 1. Squamöses, nicht sekretorisches Epithel kommt nur im dorsalen Teil der Tube vor. 2. Die Öffnungsmuskeln der Tube setzen ausschliesslich am dorsalen Abschnitt an. 3. Zur Zeit der Geburt ist lediglich das mukoziliare Epithel ausgereift. Das dorsale, squamöse hingegen erst kurz vor der Belüftung des Mittelohres (10 Tage postpartal). Diese Befunde führten zum Konzept der räumlich-funktionellen Zweiteilung des Tubenepithels: Der dorsale Teil spielt eine Rolle bei der Belüftung des Mittelohres, der ventrale dient der Clearance.
    No preview · Article · Jan 1998 · Oto-Rhino-Laryngologia Nova
  • [Show abstract] [Hide abstract]
    ABSTRACT: Histological studies of the eustachian tube may reveal its basal functions, i.e. protection, clearance and ventilation. Thorough histological and microdissectional research as well as developmental studies have yielded data which provide further insight into the function of the eustachian tube. These new data are: (1) the appearance of squamous non-secretory epithelium in only the dorsal part of the tube; (2) the solely dorsal attachment of the fibres of the tubal dilators, and (3) the maturation of the mucociliary part of the epithelium at the time of birth whereas the dorsal (squamous) epithelium matures only just before the middle ear is aerated. This resulted in the concept of spatial separation, a subdivision in the structure of the eustachian tube. According to this concept the dorsal part is involved in the ventilation of the middle ear while the ventral part serves its clearance.
    No preview · Article · Jan 1998
  • J J Manni · W Kuijpers

    No preview · Article · Feb 1997 · Acta Oto-Laryngologica
  • [Show abstract] [Hide abstract]
    ABSTRACT: The immunohistochemical expression patterns of cytokeratin polypeptides and vimentin were investigated in normal epithelia and squamous cell carcinomas of the larynx with special emphasis on tumor grading. During malignant transformation of epithelial cells, the cytokeratin expression patterns changed, depending on the differentiation grade of the carcinomas. In low-grade carcinomas, the expression patterns were close to those of the normal epithelium. With increasing tumor grade, there was decreased expression of stratification cytokeratins and increased expression of basal cell, simple cell and hyperproliferation-related cytokeratins. Increasing tumor grade was also associated with the expression of vimentin, a cytoskeletal protein of mesenchymal cells. No relationship was found between vimentin expression and the presence of lymph-node metastases.
    No preview · Article · Feb 1997 · Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde
  • J. J. S. Mulder · W. Kuijpers

    No preview · Article · Jan 1997
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the type of differentiation of keratinocytes of acquired cholesteatoma and its significance for cholesteatoma invasiveness. Forty acquired cholesteatomas and 10 tympanic membranes with persisting perforations were snap frozen and processed for immunohistochemical studies. Cytokeratin antibodies that represented all subgroups and antibodies that were directed against collagen components of the basal lamina were applied. Expression of these constituents was scored by using light microscopy. The phenotype of the matrix was generally characterized by an extension of expression of basal cell cytokeratin 14 and hyperproliferation-associated cytokeratins 6, 16, and 17 into the suprabasal cell layers, while the expression of keratinization marker cytokeratin 10 was down-regulated. These features varied greatly at different sites of the matrix and were most marked at the advancing front of the cholesteatoma. A comparable expression pattern, but less pronounced, was observed at the epidermal front of the mucocutaneous junction of the tympanic membrane perforations. This phenomenon was invariably associated with a mononuclear cell infiltrate in the dermis at both junctions. The basal lamina was always intact. Acquired cholesteatomas show hyperproliferative features. There is a striking similarity between the pronounced expression of this phenotype and the associated inflammation at the mucocutaneous junctions of cholesteatomas and tympanic membrane perforations and those that are observed after epidermal injury. This indicates that epidermis and middle ear epithelium do not form stable junctions and the front can be considered to be a persisting epidermal defect. This involves the permanent presence of "activated keratinocytes" in the junction area that will lead to proliferation and migration, when additional triggers are present.
    Preview · Article · Sep 1996 · Archives of Otolaryngology - Head and Neck Surgery
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Experimental autoimmune pigment epithelial protein-induced uveitis (EAPU) is a new type of disease that destroys the retinal pigment epithelium (RPE), and exhibits a hitherto unknown form of progressive chorioretinal dystrophy in which neuroretinal inflammatory foci are absent. The present study was aimed at studying the expression of adhesion molecules, and the kinetics of the appearance of the main types of macrophages and other intraocular immunocompetent cell populations in the various stages of this disease. EAPU was evoked in Lewis rats by immunization with the membrane protein from bovine RPE cells containing PEP-65 as main constituent. In the uvea, increased expression of intercellular adhesion molecule-1, of class II major histocompatibility complex antigen, and of ED2 macrophage reactivity were observed closely before the onset of EAPU. Expression of these reactivities was also slightly elevated by injections of the applied adjuvants alone. The onset of EAPU was mainly characterized by initial uveal infiltrations of ED1+ macrophages and a minor population of CD4 T cells, and an increase in ED3, ED7 and perivascular ED2 reactive macrophages. This was followed by the development of focal accumulations of ED1+ cells at both sides of the Bruch's membrane-RPE layer (Dálen-Fuchs nodules) which was permeated and disintegrated at these sites. The outer choroidal layer, the anterior iridal surface, and the base of the ciliary body more frequently contained active inflammatory cells than the other uveal areas. Lymphoid cells were found scattered through the uvea, aqueous and vitreous. The sites of increased activity of ED2+ and ED3+ cells in the uvea were rather similar to those of ED1 macrophages in the various stages of EAPU. Starting from multiple foci, the process of the formation of plaque-shaped cell accumulations in severe EAPU progressed along the RPE and exhibited a chronic character. The results of this study show that ED1+, ED2+, ED3+ and ED7+ subpopulations of macrophages are actively involved in an immunopathological process in which the RPE is the target. The thickening of the plaque-shaped cell accumulations stops if the integrity of all RPE cells at that site has been affected. We postulate that this is the result of antigen elimination while additional influence of the abrogation of RPE cytokine production is presumed.
    Full-text · Article · Jun 1996 · Experimental Eye Research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The differentiation of epidermis in the various parts of the human ear canal was documented on the basis of cytokeratin (Ck) expression patterns. Immunohistochemistry was performed on cryostat sections of normal meatal skin using a comprehensive panel of monospecific Ck antibodies representing the main lines of epithelial differentiation. The epidermis of the cartilaginous part showed a Ck profile characteristic of normal skin type differentiation. The deep meatal skin, including the tympanic membrane, showed a peculiar type of differentiation: in addition to epidermal Cks, hyperproliferation-associated Cks 6, 16, and 17 were expressed in the suprabasal cells, while the simple epithelia cell marker Ck 19 was found in the basal cells. The presence of hyperproliferative Cks in the deep meatal skin could only partly be related to areas of proliferative activity. Keratinocytes, which express markers of hyperproliferation, are migratory. Therefore, their presence in the meatal skin is likely to be related to the peculiar pattern of keratinocyte migration, the purpose of which is to keep the meatus free from desquamation products.
    Full-text · Article · May 1996 · The Laryngoscope

Publication Stats

1k Citations
135.61 Total Impact Points


  • 1986-2009
    • Radboud University Medical Centre (Radboudumc)
      • Department of Human Genetics
      Nymegen, Gelderland, Netherlands
  • 1973-1999
    • Radboud University Nijmegen
      • Institute of Otorhinolaryngology
      Nymegen, Gelderland, Netherlands
  • 1996
    • Maastricht University
      • Genetica en Moleculaire Celbiologie
      Maastricht, Provincie Limburg, Netherlands
  • 1986-1990
    • Leiden University
      Leyden, South Holland, Netherlands
  • 1978
    • Utrecht University
      Utrecht, Utrecht, Netherlands
    • University of Antwerp
      Antwerpen, Flanders, Belgium
  • 1976
    • University of Dundee
      Dundee, Scotland, United Kingdom