Transfection of neonatal rat cochlear cells in vitro with an adenovirus vector

A recombinant adenovirus vector containing a βI-galactosidase reporter gene was used to transfect neonatal rat organ of Corti or spiral ganglion explants in vitro. Infection at appropriate titers (10⁶−10⁷ pfu/ml) transduced virtually all cells in the cultures after 72 hr. However, spiral ganglion neurons and cells in the inner hair cell regions of the organ of Corti showed the highest levels of expression. Viral titers that produced high levels of β-galactosidase expression did not appear to damage the cultures, and did not inhibit neurite outgrowth from spiral ganglion cells. However, higher titers (10⁸-10⁹pfu/ml) clearly diminished explant viability and inhibited neurite extension. The results demonstrate that cochlear cells can be transfected successfully with an adenovirus vector, at viral titers which do not induce obvious signs of cellular damage or dysfunction.     

Intense noise induces formation of vasoactive lipid peroxidation products in the cochlea

This study investigates the correlation between the formation of reactive oxygen species (ROS) and auditory damage in noise-induced hearing loss. The noise exposure (4-kHz octave band, 115 dB SPL, 5 h) created permanent threshold shifts at frequencies from 2 to 20 kHz. The lipid peroxidation product, 8-isoprostane, was determined biochemically and histochemically as an indicator of ROS. Noise exposure increased 8-isoprostane levels in the cochlea in a time-dependent manner. After 5 h of exposure, 8-isoprostane levels were more than 30-fold greater than baseline, and decreased rapidly after the termination of noise. The immunoreactivity to 8-isoprostane was increased in the stria vascularis, spiral ganglion cells and the organ of Corti. In the organ of Corti, immunostaining was restricted to the second turn in a region 10-12 mm from the apex. This region sustained most of the permanent hair cell damage as revealed in surface preparations. Outer hair cells were more heavily immunostained than inner hair cells while Hensen's cells showed still less immunostain. These data are consistent with the view that ROS are involved in noise-induced damage. However, the relationship between ROS formation and tissue damage appears complex. In the organ of Corti, the pattern of noise-induced lipid peroxidation correlates well with subsequent morphological damage. The stria vascularis, however, does not sustain permanent damage despite intense lipid peroxidation. Differences in endogenous antioxidant levels and commitment to different apoptotic or survival pathways may underlie such differential responses.     

Two modes of hair cell loss from the vestibular sensory epithelia of the guinea pig inner ear

In the vestibular and auditory neurosensory epithelia of poikilothermic vertebrates and of birds, damaged sensory “hair” cells are often deleted by extrusion from the apical surface. In contrast, in the adult mammalian auditory epithelium (the organ of Corti), the bodies of damaged hair cells degenerate within the epithelium. To determine whether this apparent difference is species related or is associated with the differing structural organisation of the epithelia, hair cell deletion in the mammalian vestibular end-organs was examined. The structural organisation of these tissues is closer to that of the inner ear epithelia of lower vertebrates than to the organ of Corti. Hair cell loss was induced by chronic, systemic treatment of guinea pigs with the ototoxic aminoglycoside antibiotic gentamicin. The vestibular sensory epithelia were examined at various times after treatment via scanning electron microscopy, thin sectioning, and staining f-actin with fluorescently labelled phalloidin. Two distinct modes of hair cell loss were identified: (1) degeneration of hair cells within the epithelium, which often showed morphological features consistent with those described for apoptosis, and (2) extrusion of intact cells from the apical surface. Neither process caused the formation of obvious lesions through the epithelial surfaces. Expansion of adjacent supporting cells during hair cell deletion resulted in repair that appeared to preserve permeability barriers. There was also no evidence of inflammation accompanying hair cell removal. Thus, with both modes of hair cell loss, it appeared that deletion of hair cells was achieved without disruption of tissue architecture or integrity. This may be important for subsequent repair and regeneration processes to operate.     

Mutual Induction of TGFβ1 and NGF after Treatment with NGF or TGFβ1 in Grafted Chromaffin Cells of the Adrenal Medulla

Chromaffin cells have been recognized for their ability to transform into sympathetic ganglion-like cells in response to nerve growth factor (NGF) or to stimulation of other neurotrophic factors. Transforming growth factor β (TGFβ) family members have been shown to potentiate the effect of different trophic factors. The aim of this study was to investigate if TGFβ may influence NGF-induced neuronal transformation and regulation of NGF, TGFβ1, and their receptors in the adult rat chromaffin tissue after grafting. Intraocular transplantation of adult chromaffin tissue was employed and grafts were treated with TGFβ1 and/or NGF. Graft survival time was 18 days after which the grafts were processed for TGFβ luciferase detection assay, NGF enzyme immunoassay, or in situ hybridization. In grafts stimulated with NGF, increased levels of TGFβ1 and TGFβ1 mRNA were detected. When grafts instead were treated with TGFβ1, enhanced levels of NGF protein were found. Furthermore, a positive mRNA signal corresponding to the transforming growth factor II receptor (TβRII) was found in the chromaffin cells of the normal adrenal medulla as well as after grafting. No increase of TβRII mRNA levels was detected after transplantation or after TGFβ1 treatment. Instead a reduction of TβRII mRNA expression was noted after NGF treatment. NGF stimulation of grafts increased the message for NGF receptors p75 and trkA in the chromaffin transplants. Grafts processed for evaluations of neurite outgrowth were allowed to survive for 28 days and were injected weekly with NGF and/or TGFβ1. NGF treatment resulted in a robust innervation of the host irides. TGFβ1 had no additive effect on nerve fiber formation when combined with NGF. Combined treatment of NGF and anti-TGFβ1 resulted in a significantly larger area of reinnervation. In conclusion, it was found that NGF and TGFβ1 may regulate the expression of each other's protein in adult chromaffin grafts. Furthermore, TβRII mRNA was present in the adult rat chromaffin cells and became downregulated as a result of NGF stimulation. Although no synergistic effects of TGFβ1 were found on NGF-induced neurite outgrowth, it was found that TGFβ1 and NGF signaling are closely linked in the chromaffin cells of the adrenal medulla.     

Endothelial nitric oxide synthase upregulation in the guinea pig organ of Corti after acute noise trauma

Endothelial nitric oxide synthase (eNOS) upregulation was identified 60 h after acute noise trauma in morphologically intact cells of the reticular lamina in the organ of Corti of the guinea pig in the second turn of the cochlea. Using gold-coupled anti-eNOS antibodies and electron microscopy, it was shown that eNOS expression was upregulated in all cell areas and cell types except inner hair cells. Furthermore, eNOS was found in the organelle-free cytoplasm and in mitochondria of various cell types. The density of eNOS in mitochondria was considerably higher compared with the surrounding cytoplasm. Since eNOS activity is regulated by calcium, the eNOS detection was combined with calcium precipitation, a method for visualizing intracellular Ca2+ distribution. After acute noise trauma, intracellular Ca2+ was increased in all cell types and cell areas except in outer hair cells. Comparing the distribution patterns of eNOS and calcium, significantly elevated levels (P < 0.0001) of eNOS were detected within a 100 nm radius near calcium precipitates in all cuticular structures as well as microtubule-rich regions and Deiters' cells near Hensen cells. The observed colocalization lends support to the postulated mechanism of eNOS activation by Ca2+. eNOS upregulation after acute noise trauma might therefore be part of an induced stress response. The eNOS upregulation in cell areas with numerous microtubule- and actin-rich structures is discussed with respect to possible cytoskeleton-dependent processes in eNOS regulation.     

β-Endorphin modulates T-cell intracellular calcium flux and c-myc expression via a potassium channel

To characterize the effect of β-endorphin on T-lymphocyte activation, we examined its influence on membrane currents, intracellular calcium flux, and c-myc mRNA levels during mitogenic stimulation of Jurkat cells. While β-endorphin weakly enhanced voltage-activated K⁺ currents of Jurkat cells by itself, it suppressed these currents in the presence of mitogen. Naloxone, by itself, also enhanced K⁺ current amplitude, but in the presence of mitogen partially reversed the suppressive effect of β-endorphin. A 5–30 min exposure to β-endorphin resulted in an increase in the rate of mitogen-stimulated intracellular calcium release and an increase in c-myc mRNA levels relative to controls. Longer exposure (1–2 h) to β-endorphin retarded intracellular calcium release, and suppressed c-myc expression. The suppressive effects were reversed by naloxone and mimicked by the K⁺ channel blocker, tetraethylammonium ion. These data suggest that opiate receptors and K⁺ channels of Jurkat cells are functionally coupled in a way that modulates intracellular calcium release and c-myc expression — two key processes in T-cell mitogenesis.     

The bacterial Neo gene confers neomycin resistance to mammalian cochlear hair cells.

The aminoglycoside antibiotics are important agents in the treatment of bacterial infection. At pharmacological doses they also preferentially damage the sensory hair cells of the inner ear, leading to ototoxic hearing loss. However, it has been suggested that the mechanism of ototoxicity is different from that of bacterial toxicity. The bacterial neomycin phosphotransferase gene (Neo) confers resistance to this and related aminoglycoside antibiotics. To determine whether the Neo gene also confers resistance to vertebrate ototoxicity, the sensitivity of cochlear hair cells to neomycin was evaluated in mice with a targeted insertion of Neo. Organotypic cultures of the organ of Corti, isolated from neonatal wild-type mice and two strains of mice carrying the Neo gene, were cultured for 72 h in the absence (controls) or in the presence of 200 microM neomycin. Organs from wild-type mice showed no remaining outer hair cells and <25% of inner hair cells when incubated with neomycin. In contrast, organs from mice carrying the Neo gene showed no loss of hair cells after neomycin treatment.     

Transforming growth factor-alpha-induced cellular changes in organotypic cultures of juvenile, amikacin-treated rat organ of corti.

Hair cell losses in the mammalian cochlea following an ototoxic insult are irreversible. However, past studies have shown that amikacin treatment in rat cochleae resulted in the transient presence of atypical Deiters' cells (ACs) in the damaged organ of Corti. These ACs arise through a transformation of Deiters' cells, which produce, at their apical pole, densely packed microvilli reminiscent of early-differentiating stereociliary bundles. The ACs do not, however, express typical hair cell markers such as parvalbumin or calbindin. The present study was designed to determine whether specific growth factors could influence the survival and differentiation of these ACs and stimulate hair cell regeneration processes in vitro. Apical-medial segments of organ of Corti of juvenile amikacin-treated rats were established as organotypic cultures, and the effects of epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1), transforming growth factor-alpha (TGFalpha), and retinoic acid were studied using morphological and molecular approaches. Our results indicate that TGFalpha supports the survival of the damaged organ of Corti and influences ACs differentiation in vitro, possibly acting through reorganization of the actin cytoskeleton. These effects could be directly mediated through activation of the EGF receptor, which is expressed by supporting cells in the mature organ of Corti. TGFalpha does not, however, allow the ACs to progress towards a hair cell phenotype.     

Factors modulating supernumerary hair cell production in the postnatal rat cochlea in vitro

It has been shown in the past that extra hair cells or supernumerary cells can be produced when neonatal cochleae are maintained in vitro. In this report, we investigated the effects of the culture methods, molecules and growth factors that are thought to be involved in cell proliferation. Quantitative studies of supernumerary hair cells were made by measuring the cell density over the entire spiral lamina at two postnatal stages: birth and 3 days after birth. With a standard feeding solution without serum, a difference in cell density was observed between the two methods of culture. Cochlear explants in a standard feeding solution supplemented with serum showed an increase of cell density only when the explantation is made at birth. Retinoic acid added to the standard feeding solution did not increase the hair cell density, while insulin induced an increase, especially at 5 μg/ml. Several growth factors were tested. Epidermal growth factor (EGF) presented a dose dependent effect with an increase of up to 30% of hair cell density that was observed in the basal region when the explantation was made at birth. Transforming growth factor-a did not induce an increase of cell density, whereas transforming growth factor-β presented an effect on hair cell density, with a dose dependent effect reaching 37.4% for the basal inner hair cells. Interpretation of these results is limited because of the lack of data concerning the presence of specific membrane receptors. One possibility is that insulin stimulates hair cell differentiation from existing undifferentiated cells. Another hypothesis may be related to the EGF and transforming growth factor-β, where these molecules might induce transdifferentiation of cells by acting on the transmembrane molecules and the extracellular matrix.     

Interactions between growth factors and steroids in the control of LHRH-secreting neurons

How the gene expression and the release of luteinizing hormone releasing hormone (LHRH) are controlled in LHRH-secreting neurons is a very crucial and still debated topic of the neuroendocrinology. Several observations present in literature have recently indicated that glial cells may influence the activity of hypothalamic LHRH-secreting neurons, via the release of growth factors. The present review will summarize data obtained in our laboratory indicating that: (a) type 1 astrocytes, a kind of glial cells, are able to release in vitro growth factors belonging to the transforming growth factors beta (TGFβ) family (i.e. TGFβ1 and TGFβ2) which influence the gene expression and the release of the decapeptide in immortalized LHRH-secreting neurons; (b) glial cells are also able to influence the steroid metabolism occurring in these neurons and in some cases this effect is exerted by TGFβ1; (c) the mRNA levels of TGFβ1 and of basic fibroblast growth factor (bFGF), another growth factor involved in the control of LHRH-secreting neurons, are modified in the rat hypothalamus during the different phases of the estrous cycle; (d) steroid hormones are able to modulate the gene expression of TGFβ1 and bFGF both in vivo (i.e. in the whole hypothalamus of ovariectomized rats) and in vitro (cultures of type 1 astrocytes). On the basis of these results a possible functional correlation in the control of LHRH-secreting neurons between growth factors and gonadal steroids will be discussed and proposed.     

Postnatal development of the hamster coclea. I. Growth of hair cells and the organ of Corti

A morphometric analysis of the developing organ of Corti and its component hair cells was carried out in an age-graded series of Syrian golden hamsters with the aid of scanning electron microscopy. The purpose was to establish a quantitative framework that would provide insight into the rules and principles by which the mammalian cochlea attains its adult proportions. This study examined postnatal development at two day intervals from birth to 22 days after birth. Our analysis included measures of cochlear length and hair cell numbers as well as measures of hair cell sizes in each of five sectors along the cochlear spiral. Our results demonstrate several principles of cochlear development: (1) The full two and one-fourths turns seen in the adult cochlea are already present at birth, but the cochlea continues to elongate for the next 10–12 days. (2) Development of hair cells in the apex generally lags behind that in the base. Whereas the stereocilia and apical margins of hair cells are clearly defined in the basal turn, they become well defined in the apex only postnatally. (3) Growth in cochlear length occurs mainly by increases in cell size rather than in cell numbers; although hair cells do increase in numbers during the first 4 days of cochlear growth, this increase involves addition of hair cells only to preexisting regions of the cochlear apex. Moreover, the full complement of hair cells is established 6 days before the full size of the cochlea is attained; in contrast, hair cell growth occurs at all positions along the cochlear spiral and spans the entire period of cochlear elongation. (4) The period of hair cell growth exceeds the period of organ of Corti growth and appears to be possible by decreases in intercellular spacing, primarily in the apical region of the cochlea; inner and outer hair cell growth was complete between 16 and 18 days after birth. (5) Inner and outer hair cell neighbors remain virtually constant at different ages indicating that the spatial relationships between the two hair cell populations is preserved as the cochlea grows. (6) Comparison with previous developmental studies of auditory function in the hamster reveals that the age of 16 days after birth, when hair cells attain their mature sizes, coincides with the onset of brainstem auditory evoked responses. Growth of hair cell somas alone, however, cannot explain either the subsequent maturation of evoked potential thresholds or changes in frequency representation in the developing cochlea. © Wiley-Liss, Inc.     

Attempt at hair cell neodifferentiation in developing and adult amikacin intoxicated rat cochleae

Recent studies have shown that an attempt at auditory hair cell neodifferentiation occurs in vivo in the rat organ of Corti after amikacin intoxication during the last stages of cochlear maturation. Atypical cells, with morphological characteristics reminiscent of very immature sensory hair cells, were transiently observed after outer hair cell losses. The aim of the present study was to assess (i) if this attempt at hair cell neodifferentiation was related to the degree of maturity of the organ of Corti and (ii) to characterise morphological and molecular changes in the scarring epithelium. We therefore investigated, using electron and confocal microscopy, morphological and molecular changes in cochleae from rats treated with amikacin at two different periods: from post natal day (PND) 1 to PND 8, when the organ of Corti is very immature; and from PND 30 to 37, when the organ of Corti is morphologically and functionally mature. In both groups, transient atypical cells were observed, attesting that the attempt at hair cell neodifferentiation is not strictly related to the immaturity of the cochlea. The results also suggest that Deiters cells are involved in the appearance of atypical cells, possibly through a transdifferentiation process. Finally, it appears that non-sensory epithelial cells from the outer spiral sulcus progressively colonize the region of pre-existing outer hair cells.     

Mild carbon monoxide exposure diminishes selectively the integrity of the cochlea of the developing rat

Rat pups were chronically exposed to carbon monoxide (CO) concentrations (12 or 25 ppm) in air starting at day 8, through 22 days of age, to examine the changes in the peripheral auditory system. Gastrostomy-reared rat pups, with or without CO exposure, were used and compared with mother-reared pups. The organ of Corti and the neurons of the spiral ganglion were analyzed for their morphology by using immunochemical and histological techniques. The inner and outer hair cells in the organ of Corti of animals exposed to 12 and 25 ppm CO were not different from the controls. However, at 25 ppm CO exposure, the nerve terminals innervating the inner hair cells were swollen. The somata of neurons in the spiral ganglion showed mild changes in the cytoplasm, and signs of mild vacuolization were observed in myelin covering their central processes. Synaptophysin, a marker for synaptic vesicles, and choline acetyltransferase, a marker for cholinergic terminals, showed no difference in immunoreactivity in CO exposed animals at 12 and at 25 ppm when compared with their age-matched controls. Also, Na(+)K(+) ATPase immunoreactivity patterns were normal compared with controls. Three enzymes were significantly reduced at the 25 ppm CO exposure: Cytochrome oxidase, NADH-TR, and calcium ATPase were decreased in both the organ of Corti and the neurons of the spiral ganglion, and decreased immunostaining for the neurofilament and myelin basic proteins was found. We conclude that components of the cochlea are selectively affected by mild chronic CO exposure during development.     

Calpain inhibitors protect auditory sensory cells from hypoxia and neurotrophin-withdrawal induced apoptosis

Inhibitors of calpain have been shown to protect nerve growth factor (NGF)-deprived ciliary ganglion neurons and hypoxic cortical neurons. Calpains have been identified in the cochlea and are active during ischemic injury. Since apoptosis can be initiated by loss of neurotrophic support, hypoxia, and ototoxins (e.g., cisplatin, CDDP), the role of calpain inhibitors under these conditions was examined in auditory hair cells and neurons. Dissociated spiral ganglion neuron (SGN) cell cultures and organ of Corti explants from P3 rats were used to test the efficacy of calpain inhibitors as otoprotective molecules. Our results indicate that calpain inhibitor I, calpain inhibitor II, and leupeptin all provided significant protection of SGNs against neurotrophin-withdrawal and hypoxia-induced apoptosis. The increase in neuronal survival ranged from 2.16 to 2.31 times greater than in untreated neurotrophin-withdrawn SGN cell cultures. BOC-Asp(Ome)-Fluoromethyl Ketone (B-D-FMK), a general caspase inhibitor, increased neuronal survival 2.16 times more. Neuronal survival rates were from 1.88 to 2.27 times greater than in untreated, hypoxic neurons and hair cell survival rates were from 1.98 to 2.03 times greater than untreated, hypoxic organ of Corti explants. However, protection of auditory hair cells and neurons from CDDP-induced damage (10 and 6 μg/ml, respectively) was limited with any of these calpain inhibitors. Apoptotic pathways initiated by neurotrophin-deprivation and ototoxic stress (e.g., CDDP) have been shown to be different. Our results agree with this finding, with neurotrophin-withdrawal and hypoxia, but not CDDP damage-induced apoptosis being calpain-dependent.     

Degeneration followed by partial regeneration of the organ of Corti in deafness (dn/dn) mice.

The deafness mouse is a Mendelian recessive mutant which never hears and has no stimulus-related receptor or neural auditory responses. From birth through 12 days after birth (DAB), the organ of Corti develops normally as seen with light microscopy, except that the space of Nuel does not fully develop. The inner and outer hair cells are degenerating between 12 and 24 DAB and are gone by 45 DAB. As the hair cells degenerate, other cells of the organ of Corti become less recognizable, appear to collapse, and lose their identities as differentiated cells. By 45 DAB, from base to apex, the organ of Corti is composed of a low, roughly cuboidal epithelium with no distinguishing cell types; a hint of a tunnel of Corti remains at the apex. In the basal turn, the organ of Corti remains in this degenerated state through at least 460 DAB (senility for these mice). In the apical organ of Corti, considerable regeneration occurs between 45 and 90 DAB. By 90 DAB the apical turn of the organ of Corti has readily identifiable inner and outer pillar cells, inner and outer supporting cells, Hensen's cells, and Claudius' cells. A tunnel of Corti and space of Nuel are also present in the apex but there are no hair cells. Mechanisms are not known for either the degeneration or the regeneration.     

TGFα and the Blood–Brain Barrier: Accumulation in Cerebral Vasculature

Transforming growth factor α (TGFα) is a cytokine that belongs to the epidermal growth factor (EGF) family of growth factors. EGF has a fast and saturable entry from blood to brain that is inhibitable by TGFα (18). In this report, we studied the passage of TGFα from blood to brain after an i.v. bolus injection. Using radioactively labeled peptide, we found that TGFα had an apparent rate of entry of 0.7 μl/g/min. However, most of the TGFα was trapped in the capillary endothelial cells of the cerebral vasculature rather than entering the brain parenchyma. No saturation was detected. TGFα was relatively stable in blood for 20 min after i.v. injection, but dissociation of the isotope ¹²⁵I was more evident in brain. The accumulation of TGFα in the cerebral vasculature was similar to that of amyloid-β protein_1–40. Therefore, we conclude that TGFα from the periphery interacts with the blood–brain barrier without substantial uptake into brain parenchyma. This raises the possibility that TGFα might be involved in intracranial vascular disorders such as angiopathy.     

Localisation of functional muscarinic receptors in the rat cochlea: evidence for efferent presynaptic autoreceptors

In the rat cochlea, the activation of muscarinic receptors stimulates the hydrolysis of phosphoinositides but the importance of this muscarinic effect is still unknown. In order to find out about the role of the muscarinic receptors in the cochlea, we examined their functional distribution within this organ. This was achieved by measuring the formation of [³H]inositol phosphates induced by carbachol (1 mM) in two regions of the cochlea: the modiolus and the organ of Corti. At both sites, carbachol enhanced the accumulation of inositol phosphates in an atropine-sensitive way. These stimulations were completely antagonised by 4-diphenylacetoxy-N-methyl piperidine methiodide (1 μM) but unchaged by pirenzepine (1 μM). In cochleas depleted of outer hair cells by a treatment with amikacin, the carbachol-induced formation of inositol phosphates is not altered with respect to control, undamaged cochleas. Conversely, when the medial cholinergic axons which form synapses with the outer hair cells are destroyed by the section of the crossed olivocochlaer bundle the carbachol-stimulated inositol phosphates response is reduced by 35% in the organ of Corti. This section has no effect in the modiolus, despite the degeneration of some modiolar fibers. Our results show that functional muscarinic receptors are distributed both in the organ of Corti and in the modiolus. These two structures contain presumably the same class of cholinoceptor. The effects of selective destruction clearly demonstrate that a population of muscarinic receptors is located on presynaptic membranes at the level of the medial axon-outer hair cell contacts. They also point to spiral ganglion neurons and/or the Schwann cells as sites for the functional cholinoceptors in the modiolus.     

Calcineurin activation contributes to noise-induced hearing loss

Acoustic overstimulation increases Ca(2+) concentration in auditory hair cells. Because calcineurin is known to activate cell death pathways and is controlled by Ca(2+) and calmodulin, this study assessed the role of calcineurin in auditory hair cell death in guinea pigs after intense noise exposure. Immediately after noise exposure (4-kHz octave band, 120 dB, for 5 hr), a population of hair cells exhibited calcineurin immunoreactivity at the cuticular plate, with a decreasing number of positive-stained cells on Days 1-3. By Day 7, the levels of calcineurin immunoreactivity had diminished to near control, non-noise exposed values, concomitant with an increasing loss of hair cells. Staining of hair cell nuclei with propidium iodide (PI), restricted to calcineurin-immunopositive cells, indicated breakdown of cell membranes symptomatic of incipient cell death. The local application of the calcineurin inhibitors, FK506 and cyclosporin A, reduced the level of noise-induced auditory brain stem response threshold shift and hair cell death, indicating that calcineurin is a factor in noise-induced hearing loss. The results suggest that calcineurin inhibitors are of potential therapeutic value for long-term protection of the morphologic integrity and function of the organ of Corti against noise trauma.     

TGFβ1 and TGFβ2 Concentrations Are Elevated in Parkinson's Disease in Ventricular Cerebrospinal Fluid

Transforming growth factor (TGF)β plays a role in injury repair in sites surrounding brain injury. The present study tested the hypothesis that TGFβ1 and TGFβ2 levels in the postmortem CSF of patients with neurodegenerative disorders would be elevated compared to those in normal subjects. Free TGFβ1 and total TGFβ2 were measured by ELISA in postmortem ventricular cerebrospinal fluid (vCSF) of patients with Parkinson's disease (n = 30), Alzheimer's disease (n = 30), multiple sclerosis (n = 15), and schizophrenia (n = 12) and of normal controls (n = 16). In addition, albumin, IgG, and total protein in vCSF were measured. Both TGFβ1 and TGFβ2 were significantly different between groups (P < 0.002 andP < 0.001, respectively). Parkinson's disease vCSF showed significant increases in both TGFβ1 (P = 0.015) and TGFβ2 (P = 0.012) compared to normal controls. There was a trend for TGFβ2 to be elevated in Alzheimer's disease and multiple sclerosis vCSFs, which failed to achieve significance. There were no differences between controls and schizophrenics in TGFβ1 or TGFβ2. Alzheimer's disease vCSF showed a significant decrease in protein compared to all other groups, which was not related to blood–brain barrier permeability, age, or autolysis differences. Evidence is presented suggesting that some TGFβ1 may leak into the vCSF from plasma. Autopsy vCSF levels of TGFβ isoforms were found to be distinctly different from those reported for human serum, especially for TGFβ2, which is undetectable in plasma. These results indicate that furtherin vivostudies of TGFβ2 in the CSF of Parkinson's disease patients are warranted to determine the relationship between clinical status, medication, and TGFβ2 concentrations.     

Sequential changes in anti-GAL-1 staining of the rat organ of Corti following amikacin exposure

Hair cell loss and a non-functional epithelial reorganization appeared in the organ of Corti after acoustic or toxic damage. Moreover, in the drug damaged organ of Corti, transient atypical cells were recently described with characteristics of both immature hair cells and/or non-sensory epithelial cells. The phenotype of these atypical cells has been now investigated by using the galectine 1 (GAL-1) antibody. In the normal organ of Corti, this antibody recognizes all the epithelial cells except the sensory hair cells and their supporting cells. At PD 21, transient atypical cells were not stained by GAL-1 antibody, suggesting that they were originated from hair cells or their supporting cells. Later, the organ of Corti was substituted by an epithelial scare, GAL-1 stained. This study also emphasizes the particular resistance of the cochlear apex to degeneration after antibiotic intoxication.