Stria Vascularis Of Guinea Pigs Research Articles

Noise-induced blood-labyrinth-barrier trauma of guinea pig and the protective effect of matrix metalloproteinase inhibitors

Objective: The research is to study the expression and distribution of matrix metalloproteinase (MMPs)-2 and -9 in the guinea pig cochlea after noise exposure, and to explore the role of MMPs in the blood-labyrinth-barrier (BLB). In addition, the role of MMPs inhibitor doxycycline in noise-induced BLB trauma was studied as well, which provides the basis for further studies and prophylaxis of noise-induced hearing loss. Methods: A total of 45 healthy adult guinea pigs were randomly divided into the control group (15 received intraperitoneal injection of 0.9% saline for 4 consecutive days), the noise-exposure group (15 exposed by 120 dB SPL white noise for 4 h per day for continuous 2 d, intraperitoneal injection of normal saline for 4 consecutive days) and the noise-exposure + doxycycline group (15 exposed by 120 dB SPL white noise exposure for 4 h per day for 2 consecutive days, and intraperitoneal injection of doxycycline 50 mg/kg/d for 4 consecutive days), respectively. Immunofluorescence staining, western blot, and real-time quantitative PCR were used to analyze the distribution and differential expression of MMP-2 and -9 in the stria vascularis of guinea pigs in comparison with the normal control group, noise only group, and noise & doxycycline treatment group. Immunofluorescence staining was used to observe the changes in tight junction (TJ) protein ZO-1 in stria vascularis in three groups and to investigate the effect of acoustic injury on TJs. And ABR tests were utilized to detect the hearing function of guinea pigs in the three groups. Intravenous Evans blue was administrated intravenously as an indicator of vascular leakage among three groups to study the changes in BLB permeability in context of acoustic injury. SPSS 22.0 was used for statistical analysis. Results: There was no significant difference in hearing function between the noise-exposure group and the noise & doxycycline group two hours after noise exposure. After seven, 14 and 28 days noise exposure, the hearing recovery of the noise & doxycycline treatment group was significantly greater than that of the noise-exposure group (P<0.05) . Immunofluorescence staining showed that there was only a small amount of MMP-2 and -9 in the stria vascular in the normal control group, and ZO-1 showed dense linear expression. While, in the noise-explore group, MMP-2 and -9 in the stria vascular was significantly elevated (P<0.05), and the configuration of ZO-1 became loose and discontinuous. However, the MMP-2 and -9 in the noise & doxycycline treatment group were not significantly different from the normal control group (P>0.05), which were significantly less than that in the noise-exposure group, and just a little break of ZO-1 was observed, however, the overall structure remained dense. The leakage of Evans blue from stria vascular capillary in the noise-exposure group was significantly increased, and the difference between the other two groups did not show any statistical significance (P>0.05). Conclusions: The damage of tight junction structure induced by MMP-2 and -9 may play an important role in BLB destruction. In addition, doxycycline can inhibit MMPs secretion, thereby, to some extent, protecting the integrity of BLB from acoustic injury, and contributing to the long-term hearing recovery.

Age‑associated variation in the expression and function of TMEM16A calcium‑activated chloride channels in the cochlear stria vascularis of guinea pigs.

The present study was designed to investigate the expression and function of transmembrane protein 16 (TMEM16A), a calcium-activated chloride channel (CaCC), in the stria vascularis (SV) of the cochlea of guinea pigs at different ages, and to understand the role of CaCCs in the pathogenesis of presbycusis (age-related hearing loss), the most common type of sensorineural hearing loss that occurs with natural aging. Guinea pigs were divided into the following groups: 2 weeks (young group), 3 months (youth group), 1 year (adult group), D-galactose intervention (D-gal group; aging model induced by subcutaneous injection of D-galactose) and T16Ainh-A01 (intraperitoneal injection of 50 µg/kg/day TMEM16A inhibitor T16Ainh-A01 for 2 weeks). Differences in the hearing of guinea pigs between the various age groups were analyzed using auditory brainstem response (ABR), and immunofluorescence staining was performed to detect TMEM16A expression in the SV and determine the distribution. Reverse transcription-quantitative PCR and western blot analyses were conducted to detect the mRNA and protein levels of TMEM16A in SV in the different age groups. Morris water maze behavior analysis demonstrated that spatial learning ability and memory were damaged in the D-gal group. Superoxide dismutase activity and malondialdehyde content assays indicated that there was oxidative stress damage in the D-gal group. The ABR thresholds gradually increased with age, and the increase in the T16Ainh-A01 group was pronounced. Immunofluorescence analysis in the cochlear SV of guinea pigs in different groups revealed that expression of TMEM16A increased with increasing age (2 weeks to 1 year); fluorescence intensity was reduced in the D-gal model of aging. As the guinea pigs continued to mature, the protein and mRNA contents of TMEM16A in the cochlea SV increased gradually, but were decreased in the D-gal group. The findings indicated that CaCCs in the cochlear SV of guinea pigs were associated with the development of hearing in guinea pigs, and that downregulation of TMEM16A may be associated with age-associated hearing loss.

Electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K+ channels.

The present study was designed to investigate the electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K+ channels. Pericytes were identified by determining their morphological characteristics and using pericyte-associated immunofluorescence techniques. The electrophysiological properties of strial pericytes were observed with a whole-cell patch-clamp technique. Alterations in the outward current of cochlear pericytes in the stria vascularis of guinea pigs were examined following the application of K+ channel retardants. The effects of aspirin on pericyte K+ channels were also evaluated with the whole-cell patch-clamp technique. The results demonstrated that pericytes were desmin positive, and their nuclei were large and surrounded by a small proportion of the cytoplasm. Cytoplasmic processes gradually declined in size as branches grew parallel to the capillary axis. Thus, capillaries were surrounded by tips. The electrophysiological properties of the cochlear pericytes in the stria vascularis of guinea pigs were also determined. The membrane capacitance of the pericytes was 5.9±0.3 pF, while the membrane resistance and resting potential were 2.2±0.3 GΩ and −30.9±1.2 mV, respectively. The current densities of the pericytes (pA/pF) were 3.2±0.7, 10.6±1.0, 15.7±0.9 and 21.3±1.2 at command voltages of 0, +20, +40, and +60 mV, respectively. The K+ channels were activated when the pericytes were within the range of −20 mV to +20 mV, particularly at 0 mV. The inhibition rates of the outward current of cochlear pericytes in the stria vascularis of the guinea pigs were determined by administering iberiotoxin (IBTX) and IBTX + 4-aminopyridine. Once the background leakage current was removed, the following inhibition rates were obtained with 3, 10, 30, 300 and 1,000 µmol/l aspirin: 20.8±4.8, 34.1±6.9, 48.2±6.7, 63.6±7.1 and 65.7±8.1%, respectively. The outward current of the cochlear pericytes in the stria vascularis was inhibited by aspirin with a half maximal inhibitory concentration of 24.5±4.5 µmol/l. The membranes of the pericytes in the stria vascularis are characterized by high-conductance calcium-activated K+ (BKCa) and voltage-dependent K+ (KV) channels. The outward current of the cochlear pericytes in the stria vascularis of guinea pigs was inhibited by aspirin in a concentration-dependent manner. In addition, BKCa and KV channels were inhibited by aspirin.

Contrast-enhanced MRI of the inner ear after intratympanic injection of meglumine gadopentetate or gadodiamide hydrate

Conclusion: The degree of contrast enhancement of the cochlea after intratympanic administration of meglumine gadopentetate (Gd-DTPA) or gadodiamide hydrate (Gd-DTPA-BMA) varies widely among patients with inner ear diseases. There was no morphological change in the stria vascularis after Gd-DTPA or Gd-DTPA-BMA was placed on the round window of guinea pigs. Objectives: We investigated the degree of contrast enhancement of the inner ear after intratympanic administration of ionized and nonionized gadolinium (Gd) contrast agents in patients with inner ear diseases. The inner ear toxicities of these agents were investigated in guinea pigs. Methods: 3D-FLAIR MRI was conducted 1 day after the intratympanic injection of eightfold-diluted Gd-DTPA or Gd-DTPA-BMA in 73 patients with inner ear diseases. Gd enhancement of the basal turn of the cochlea was evaluated as the signal intensity (SI) ratio between the affected and nonaffected sides. In guinea pigs, nondiluted Gd-DTPA, Gd-DTPA-BMA or saline was placed on the round window for 1 h and the stria vascularis was observed using electron microscopy. Results: The SI ratio ranged from 1.5 to 16.5 in the Gd-DTPA group and from 2.5 to 21 in the Gd-DTPA-BMA group. Electron microscopy showed no significant differences in the stria vascularis of guinea pigs in any of the groups.

Physiological Role of L-Type Ca2+ Channels in Marginal Cells in the Stria Vascularis of Guinea Pigs

Using immunohistochemical and electrophysiological methods, we investigated the role of L-type Ca(2+) channels in the regulation of the endocochlear potential (EP) of the endolymphatic surface cells (ESC) of the guinea pig stria vascularis. The following findings were made: (1) Administration of 30 microg/ml nifedipine via a vertebral artery significantly suppressed the transient asphyxia-induced decrease in the EP (TAID) and the transient asphyxia-induced increase in the Ca(2+), referred to as TAIICa, concentration in the endolymph ([Ca](e)). (2) The endolymphatic administration of 1 microg/ml nifedipine significantly inhibited the TAID as well as the TAIICa. The endolymphatic administration of nifedipine (0.001-10 microg/ml) inhibited the TAID in a dose-dependent manner. (3) The endolymphatic administration of (+)-Bay K8644, an L-type Ca(2+) channel closer, significantly inhibited the TAID, whereas (-)-Bay K8644, an L-type Ca(2+) channel opener, caused a large decrease in the EP from approximately +75 mV to approximately +20 mV at 10 min after the endolymphatic administration. (4) By means of immunohistochemistry, a positive staining reaction with L-type Ca(2+) channels was detected in the marginal cells of the stria vascularis. (5) Under the high [Ca](e) condition, we examined the mechanism of the TAIICa and hypothesized that the TAIICa might have been caused by the decrease in the EP through a shunt pathway in the ESC. (6) The administration of nifedipine to the endolymph significantly inhibited the Ba(2+)-induced decrease in the EP. These findings support the view that L-type Ca(2+) channels in the marginal cells regulate the EP, but not directly the TAIICa.

Ultrastructural Localization of Glucose Transporter 1 (GLUT1) in Guinea Pig Stria Vascularis and Vestibular Dark Cell Areas: An Immunogold Study

Glucose transporter 1 (GLUT1) is one of the facilitated-diffusion glucose transporters, which plays a major role in the glucose transport across blood-tissue barriers. We demonstrated localization of GLUT1 in guinea pig stria vascularis (SV) and vestibular dark cell areas, using electron microscopy. GLUT1 immunoreactivity was seen mainly in the SV. Electron microscopically, immunogold particles were localized along the plasma membranes of the basal cells and the basolateral infoldings of the marginal cells. Erythrocyte membranes and the capillary walls in both the SV and the dark cell areas were also positive for GLUT1. These results indicate that GLUT1 is involved in glucose regulation for energy metabolism in the marginal cells and vestibular dark cells, and in glucose transport between blood and perilymph.

Effect of cisplatin on the basement membrane anionic sites in the ampulla, macula, and stria vascularis of guinea pigs.

Our objective was to compare changes in the basement membrane anionic sites (BMAs) in the ampulla, macula, and stria vascularis following the infusion of cisplatin (CDDP). After CDDP was administered to anesthetized Hartley guinea pigs, the bony labyrinth was immersed in a solution of polyethyleneimine (PEI). The size and distribution of PEI particles associated with BMAs in the stria vascularis and in the dark cell and sensory cell areas of the vestibular labyrinth were determined by electron microscopy. A significant reduction in the number and size of PEI particles was observed on CDDP-treated strial vessels. The number and size of PEI particles on the basement membranes of the vestibular labyrinth did not differ from those in the control. Our findings suggest that the BMAs of the vestibular labyrinth were not significantly affected by the administration of a single dose of CDDP.

Endothelial Injury of Capillaries in the Stria Vascularis of Guinea Pigs Treated with Cisplatin and Gentamicin

The drugs cisplatin and gentamicin are used for treatment of various cancer patients suffering from infection. The authors report a detailed electron microscopic study of blood vessels in stria vascularis of guinea pigs after treatment with cisplatin alone and in combination with gentamicin. The most distinctive features expressing endothelial cellular injury were mitochondrial, including occasional paracrystalline inclusions; electron-lucent foci with depleted organelles; intracytoplasmic vacuole formations; lipid bodies; cytoplasmic extrusions located on the luminal surface; and severe luminal constriction of part of the vessels from animals treated with the combined drugs. The study suggests that the damage to strial capillaries due to treatment with cisplatin alone and in combination with gentamicin may contribute to the injurious effects of these drugs on the strial tissue. Furthermore, the results of this study may enlarge the awareness of the potential vascular damage and vascular complications in additional body systems after medical use of cisplatin alone or in combination with gentamicin.

ATP-induced increase in intracellular Ca 2+ concentration in the cultured marginal cell of the stria vascularis of guinea-pigs

The primary culture of marginal cells from the explant of the stria vascularis of guinea-pigs was established and confirmed by morphological, immunohistochemical and physiological characters of the cultivated cells. The positive stain of cytokeratin 18 without vimentin and desmin expressions indicated the epithelial origin of the cultured polygonal cells. Electron microscopical findings of cultured cells resembled the morphological characteristics of marginal cells. The addition of 100 μM ouabain to the cultured cells significantly increased the intracellular Na + concentration, providing the evidence for the presence of Na + pump. Using the cultured marginal cells identified by the above-mentioned findings, the effects of neurotransmitters and hormones in regulating intracellular Ca 2+ concentration ([Ca 2+] i) were investigated. The addition of 10 −4 M ATP caused an increase in [Ca 2+] i, which was independent of the presence of extracellular Ca 2+. The rank order of agonist potency was ATP>α,β-methylene ATP>ADP. Adenosine, however, evoked no response. Cultured marginal cells may possessP 2-purinergic receptors which mobilize Ca 2+ from the intracellular Ca 2+ pool. [Marginal cell, Cell culture, Na + K + ATPase, Intracellular Ca 2+ concentration, ATP]

Dopamine inhibits the Na-K ATPase activity of the stria vascularis in the cochlea. In vivo ultracytochemical study.

It is believed that the function of the stria vascularis in the cochlea is to produce endolymph. However, the mechanisms that maintain and control the function of the stria vascularis remain unclear. In the present study, to clarify the role of humoral substances in the stria vascularis, a cerium-based method was used to investigate the ultracytochemical effects of intraperitoneal dopamine administration on ouabain-sensitive, K(+)-dependent, p-nitrophenylphosphatase (K-NPPase) activity, which is the second step in the formation of the Na-K ATPase complex, in the stria vascularis of guinea pigs. Na-K ATPase activity was shown to be completely inhibited after dopamine administration. This observation suggests that dopamine inhibits Na-K ATPase activity in the marginal cells of the stria vascularis, and that the stria vascularis may have dopamine receptors. Catecholamines may play an important role in the maintenance and/or control of stria vascularis function.

Ultrastructure of guinea pig stria vascularis processed by rapid freezing and freeze substitution.

The rapid-freezing and freeze-substitution method fixes a specimen as if it were prepared before excision. We used this method to study the stria vascularis of guinea pigs using electron microscopy. Findings were essentially the same as those obtained with conventional chemical fixation, although freeze substitution made it possible to observe the membrane structures in a smoother and more linear manner. This method seems to be the procedure of choice for studying the instantaneous movement and behavior of cells.

血管条萎縮に対するステロイド剤の効果

Anaphylatoxins are known to cause strong inflammatory reactions. It has been clearly shown that atrophy of the stria vascularis, endolymphatic hydrops and other morphological changes are caused by anaphylatoxins. In this study, the effect of i. v. injected hydrocortisone on the morphological changes in the stria vascularis of guinea pigs treated with anaphylatoxins was investigated by light microscopy. Guinea pigs treated with hydrocotisone with in 5 minutes following the administration of anaphylatoxins showed a decrease in the severity of atrophy of the stria vascularis in comparison with those treated after 24 hours or 48 hours and with untreated controls.These results suggest that early administration of hydrocortisone inhibits anaphylatoxin-induced morphological changes in the inner ear.

Toxic effects of cisplatin alone and in combination with gentamicin in stria vascularis of guinea pigs

The toxic effects on the stria vascularis of treatment with cisplatin alone and combined with the aminoglycoside antibiotic, gentamicin, were studied in guinea pigs. The toxicity induced in albino and pigmented guinea pigs was investigated morphologically with light and transmission electron microscopy, and functionally by brainstem-evoked response audiometry. The results of hearing thresholds were variable, ranging from no change in one ear in some of the animals to a hearing loss of 20 dB in one or both ears when treated with low-dose cisplatin alone or in combination with gentamicin. Bilateral deafness resulted from high-dose cisplatin combined with gentamicin. The combined treatment produced prominent structural damage in the stria vascularis. The results should be considered when aminoglycoside therapy is required in conjunction with cisplatin.

Alterations in Capillary Permeability of Stria Vascularis of Guinea Pigs following Decapitation

Ten minutes after an intravenous injection of HRP, guinea pigs were killed by decapitation. The bullas were removed and opened, and the cochleas were fixed by perilymphatic infusion with glutaraldehyde. Blood shudging and considerable HRP leagage were observed in the capillaries of the stria vascularis. When blood was replaced with plasma expander, blood sludging did not appear after decapitation because few blood cells remained in the capillaries. Moreover, HRP leakage was scarecely observed in the strial capillaries. Even if the strial capillaries were contracted by the decapitation, HRP leakage did not occur without blood sludging. The high pressure between capillary endothelium and blood cells produces many marginal bolds, which efficiently transport HRP out of the capillaries.

Carbohydrates in the Guinea Pig Stria Vascularis Demonstrated with Lectin-Gold Techniques

Carbohydrates in the Guinea Pig Stria Vascularis Demonstrated with Lectin-Gold Techniques

The resting potential of marginal cells in stria vascularis explants

In order to examine the intracellular potential of stria vascularis marginal cells (MCs) under direct visual control, a short-term organ culture of guinea pig stria vascularis (SV) was developed. The experimental conditions allowed exposure of the luminal surface of the SV to artificial endolymph or perilymph. Using conventional microelectrodes and inverted bright-field microscopy, impalement of MCs from the endolymphatic side through the luminal cell membrane was achieved. With artificial perilymph at the luminal side a small positivity at the cell surface and low negative intracellular potentials were recorded at room temperature (23 degrees C). The initial recording was -6.5 +/- 5.0 mV while the stable recording was -4.0 +/- 3.6 mV. Similar results were obtained at a bath temperature of 37 degrees C. Furthermore, subtotal exposure of the luminal cell surface to artificial endolymph did not result in a significant potential change.

Carbohydrates in the Guinea Pig Stria Vascularis Demonstrated with Lectin-gold Techniques

Soybean agglutinin (SBA), Helix pomatia agglutinin (HPA), Ricinus communis agglutinin-II (RCA-II), Limax flavus agglutinin (LFA) and wheat germ agglutinin (WGA) were employed to determine the localization of specific carbohydrates on thin sections of lowicryl K4M embedded guinea pig striae vasculares using the lectin-gold and glycoprotein-gold techniques. SBA, HPA and RCA-II gold labeling was observed in many of the cytoplasmic vesicles, endosomes and apical tubules located in the supranuclear region as well as on the microvilli and micropinocytotic invaginations of the luminal plasma membrane of the marginal cells. LFA labeling was found on the basal plasma membrane of the marginal cells as well as in the basement membrane of the perivascular spaces. WGA binding sites were detected along the plasma membrane of all types of cells constituting the stria vascularis. Our present results revealed that the membranes of internalization and many of the cytoplasmic vesicles, endosomes and apical tubules in the supranuclear region of the marginal cells are associated together and it is suggested that these structures may be related to the regulation of endolymph.

The Function and Lectin Receptors in the Guinea Pig Stria Vascularis

Soybean agglutinin (SBA), helix pomatia agglutinin (HPA), ricinus communis agglutinin-11 (RCA-II), limax flavus agglutinin (LFA) and wheat germ agglutinin (WGA) were employed to localize, with a lectin-gold technique, specific carbohydrates on thin sections of guinea pig stria vascularis embedded in Lowicryl K4M.Galactose and N-acetylgalactosamine labeled with SBA, HPA and RCA-II were found in many cyto-plasmic vesicles and endosomes located in the supra-nuclear region, as well as in the microvilli and in the plasma membranes of internalization of marginal cells.LFA labeling, indicating the distribution of sialic acid residues, was found in the basement membrane of the perivascular spaces and intercellular spaces between marginal and intermediate cells and between marginal and basal cells. Plasma membrances, how-ever, were unlabeled in all types of cells.WGA binding sites showing the localization of N-acetylgalactosamine, on the other hand, were detected along the plasma membranes of all types of cells constituting the stria vascularis and in some supranu-clear cytoplasmic vesicles in marginal cells.These findings revealed that the membranes of internalization and some cytoplasmic vesicles were as-sociated with endosomes in the supranuclear region of the marginal cells. It is probable that these struc-tures are related to the functions of absorption and secretion, and that the carbohydrates labeled with SBA, HPA and RCA-11 are recirculated in this system, the exchange between Na+ and K+ facilitating.

Lectin Binding Sites in the Guinea Pig Stria Vascularis

Limax flavus agglutinin (LFA) and wheat germ agglutinin (WGA) were employed to determine the localization of N-acetylneuraminic acid (NANA=sialic acid) and N-acetylglucosamine (Glc-NAc) on thin sections of Lowicryl K4M embedded guinea pig striae vasculares, and the two lectins were revealed by means of fetuin-colloidal gold and ovomucoid-colloidal gold complexes, respectively.LFA labeling was found in many of the cytoplasmic vesicles located in the supranuclear region of the marginal cells, as well as in the basement membrane of the perivascular spaces. Intercellular spaces between marginal and intermediate cells, and those between marginal and basal cells were also positive. The plasma membrance, however, was completely unlabeled in all types of cells.WGA binding sites, on the other hand, were detected along the plasma membrane of all cells constituting the stria vascularis and in some of the supranuclear cytoplasmic vesicles in the marginal cells. Sugar inhibition experiments confirmed the specificity of LFA and WGA for NANA and Glc-NAc, respectively.The present results, together with the data previously obtained indicate that some of the cytoplasmic vesicles in the supranuclear region of the marginal cells play a role in the internalization mechanism and suggest their involvement in the selective uptake of ions.

The effects of consecutive administration of cisplatin and gentamicin on stria vascularis of guinea pigs

The effects of consecutive administration of cisplatin and gentamicin on stria vascularis of guinea pigs