Fu-quan Chen

Migration of neural precursor cells derived from olfactory bulb in cochlear nucleus exposed to an augmented acoustic environment.

The regeneration of the auditory neural system remains a challenge in hearing restoration. Acoustic signals may induce a site-specific cell replacement in the auditory system. This hypothesis was tested with grafted implantation of neural precursor cells (NPCs) along the cochlear nucleus in the adult host followed by an augmented acoustic stimulation. NPCs were obtained from the olfactory bulbs at embryonic day 14-16 and were transplanted into the inside border of cochlear nucleus. The labeled cells survived at least 2 weeks, verified by Hoechst 33342 fluorescence, and by immunostaining for a neuronal marker. In some cases NPCs had migrated directionally to the root of the auditory nerve. This observation demonstrates the survival and migration of NPCs from the olfactory bulb (OB) along the adult auditory nerve in an augmented acoustic environment following implantation.

Up-regulation of stromal cell-derived factor-1 enhances migration of transplanted neural stem cells to injury region following degeneration of spiral ganglion neurons in the adult rat inner ear

Neural stem cell (NSC) transplantation into the cochlea is widely used for the treatment of spiral ganglion neuron (SGN) degenerative disease and injury in the animal models, but the migration of the transplanted NSCs to the injury region is difficult and the mechanism is still unclear. In this study, we aimed to validate whether the SGN-degenerated cochlear microenvironment plays a role in the NSC migration and investigated whether stromal cell-derived factor-1 (SDF-1) was involved in the NSCs migration. Using a rat SGN degeneration model, we demonstrated that the transplanted NSCs are more likely to migrate to the injury region during the early post-injury (EPI) than the late post-injury (LPI) stage and the control cochlea. We found that the expressions of SDF-1 increased transiently after SGN degeneration. Additionally, we showed that the NSCs express CXCR4, a receptor for SDF-1. We observed that the region to which the transplanted NSC localized coincides with the region where the SDF-1 is highly expressed following the degeneration of SGNs. Finally, we observed that the increased SDF-1 is derived from the Schwann cells in the SGN-degenerated model. These results suggest that SDF-1, which is derived from cochlear Schwann cells and up-regulated in the early injury microenvironment, plays a beneficial role in the NSC migration to the injury region. Optimizing SDF-1 expression in the host microenvironment or increasing the CXCR4 expression of the donor stem cells may improve the migration efficiency of transplanted cells toward the injury region in the cochlea.

miR-29b overexpression induces cochlear hair cell apoptosis through the regulation of SIRT1/PGC-1α signaling: Implications for age-related hearing loss

It has been reported that the degeneration of cochlear hair cells is the typical cause of presbycusis (or age-related hearing loss). However, the molecular mechanisms that mediate cochlear hair cell apoptosis are not yet fully understood and there is no effective treatment for this disorder. MicroRNAs (miRNAs or miRs) have been increasingly shown to be associated with age-related diseases and are emerging as promising therapeutic targets. In this study, we investigated whether miR-29b is involved in the degeneration of cochlear hair cells. To examine our hypothesis, nuclear staining and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) were used to quantify the hair cell counts. RT-qPCR and western blot analysis were used to examine miR-29b/sirtuin 1 (SIRT1)/proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling in cochlear hair cells. We found that there was a significant degeneration of cochlear hair cells and a higher expression of miR-29b in aged C57BL/6 mice compared with young mice. There was also an age-related decrease in the expression of SIRT1 and PGC-1α. In the inner ear cell line, HEI-OC1, miR-29b overexpression (by transfection with miR-29b mimic) inhibited SIRT1 and PGC-1α expression, leading to an increase in mitochondrial dysfunction and apoptosis. Moreover, the inhibition of miR-29b (by transfection with miR-29b inhibitor) increased SIRT1 and PGC-1α expression, while it decreased apoptosis. Taken together, our findings support a link between age-related cochlear hair cell apoptosis and miR-29b/SIRT1/PGC-1α signaling, which may present an attractive pharmacological target for the development of novel drugs for the treatment of age-related hearing loss.

Association between histone deacetylases and the loss of cochlear hair cells: Role of the former in noise-induced hearing loss

Noise-induced hearing loss (NIHL) is one of the most frequent disabilities in industrialized countries. It has been demonstrated that hair cell loss in the auditory end organ may account for the majority of ear pathological conditions. Previous studies have indicated that histone deacetylases (HDACs) play an important role in neurodegenerative diseases, including hearing impairment, in older persons. Thus, we hypothesized that the inhibition of HDACs would prevent hair cell loss and, consequently, NIHL. In the present study, a CBA/J mouse model of NIHL was established. Following an injection with the HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), the expression levels of HDAC1, HDAC4 and acetyl-histone H3 (Lys9) (H3-AcK9) were measured. The number of hair cells was quantified and their morphology was observed. The results revealed that 1 h following exposure to 110 dB SPL broadband noise, there was a significant increase in HDAC1 and HDAC4 expression, and a marked decrease in the H3-AcK9 protein levels, as shown by western blot analysis. Pre-treatment with SAHA significantly inhibited these effects. Two weeks following exposure to noise, the mice exhibited significant hearing impairment and an obvious loss in the number of outer hair cells. An abnormal cell morphology with cilia damage was also observed. Pre-treatment with SAHA markedly attenuated these noise-induced effects. Taken together, the findings of our study suggest that HDAC expression is associated with outer hair cell function and plays a significant role in NIHL. Our data indicate that SAHA may be a potential therapeutic agent for the prevention of NIHL.

Histone deacetylase inhibitor sodium butyrate attenuates gentamicin-induced hearing loss in vivo

OBJECTIVE Although histone deacetylase (HDAC) inhibition has been shown to protect against gentamicin (GM)-induced hearing loss in vitro, its protective effect has not been proven in vivo. In the present study, the aim was to investigate the protective effect of sodium butyrate (NaB), a specific HDAC inhibitor, on GM-induced ototoxicity in vivo. METHODS Forty 8-week-old albino guinea pigs were divided into two experimental groups. Group 1 (n=10) underwent bilateral ear surgery to place sponges (0.3mm(3)) permeated with NaB (10μl, 100mg/ml) and physiological saline (10μl; control) in the right and left round window niches, respectively. The sponges were left in place for 15days to evaluate the effects of NaB at the applied concentration. Group 2 (n=30) underwent the same bilateral ear surgery described for Group 1, except three days after surgery, the animals received intramuscular GM injections (200mg/kg/day) for 5 consecutive days. Seven days after the final GM injection, the protective effects of NaB were examined. RESULTS After 15days of NaB treatment (10μl, 100mg/ml), an increase in histone acetylation was detected in Corti organ samples. Auditory brainstem response (ABR) threshold shifts and hair cell loss were also reduced in NaB-treated ears after GM administration. Furthermore, GM treatment increased HDAC1 expression in outer hair cells (OHCs) in vivo, and NaB blocked this action. CONCLUSION GM increases HDAC1 expression in OHCs, and NaB is able to block this action. Thus, it appears that the HDAC inhibitor, NaB, attenuates GM-induced hearing loss in guinea pigs.

Calpain Inhibitor PD150606 Attenuates Glutamate Induced Spiral Ganglion Neuron Apoptosis through Apoptosis Inducing Factor Pathway In Vitro

Objective This research aimed to investigate whether glutamate induced spiral ganglion neurons (SGNs) apoptosis through apoptosis inducing factor (AIF) pathway. And verify whether PD150606, a calpain inhibitor could prevent apoptosis by inhibiting cleaving and releasing AIF in mitochondrion. Methods SGNs of postnatal days 0-3 were harvested and cultured in dishes. 20 mM Glu, the caspase inhibitor Z-VAD-FMK and calpain inhibitor PD150606 were added into cultured dishes separately. We used optical microscope and immunofluoresence staining to observe cell morphology and AIF distribution, RT-PCR and Westernblot to analyse AIF and calpain expression in SGNs. TUNEL assay was used to test cell apoptosis. Results Cell morphology and nuclear translocation of AIF were altered in SGNs by 20 mM Glu treated in vitro. The axon of SGN shortened, more apoptosis SGN were observed and the expression of AIF and calpain were up-regulated in Glu-treated group than the normal one (P<0.05). The same experiments were conducted in 20 mM+PD150606 treated group and 20 mM+Z-VAD-FMK group. Obviously AIF were located from cytoplasm to the nuclear and the expressions of AIF and calpain were down-regulated by PD150606 (P<0.05). Positive cells in TUNEL staining decreased after PD150606 treating. However, Z-VAD-FMK had no influence on AIF, calpain expression or cell apoptosis. Conclusion The AIF-related apoptosis pathway is involved in the process of Glu-induced SGN injury. Furthermore, the inhibition of calpain can prevent AIF from releasing the nuclear or inducing SGN apoptosis.

Therapeutic Effect of Histone Deacetylase Inhibitor, Sodium Butyrate, on Allergic Rhinitis In Vivo

Despite the well-documented therapeutic effects of histone deacetylase inhibitor (HDACi) on various diseases, including arthritis and asthma, the therapeutic effect of HDACi on allergic rhinitis remains unmentioned in the literature. This study investigated the therapeutic effect of sodium butyrate (SoB), a form of HDACi, on mice with allergic rhinitis. The results showed that the expression levels of histone deacetylase 1 (HDAC1), histone deacetylase 3 (HDAC3), and thymic stromal lymphopoietin (TSLP) were significantly upregulated in mice with allergic rhinitis, whereas H3 acetylation at lysine 9 (H3AcK9) was decreased. The intranasal application of SoB inhibited the expression levels of TSLP levels and upregulated the expression of H3AcK9 in a mouse model of allergic rhinitis. Furthermore, SoB treatment significantly decreased the increased levels of ovalbumin-specific IgE and improved clinical symptoms and nasal mucosa epithelial morphology in the mouse model of allergic rhinitis. In addition, we further demonstrated that SoB treatment significantly increased the serum levels of IL-2 and IFN-γ and decreased the serum levels of IL-4 and IL-10, correcting the Th1/Th2 imbalance in the mouse model of allergic rhinitis. Taken together, our study suggests that SoB has the potential to treat allergic rhinitis.

The role of RIP3 mediated necroptosis in ouabain-induced spiral ganglion neurons injuries.

Spiral ganglion neuron (SGN) injury is a generally accepted precursor of auditory neuropathy. Receptor-interacting protein 3 (RIP3) has been reported as an important necroptosis pathway mediator that can be blocked by necrostatin-1 (Nec-1). In our study, we sought to identify whether necroptosis participated in SGN injury. Ouabain was applied to establish an SGN injury model. We measured the auditory brain-stem response (ABR) threshold shift as an indicator of the auditory conditions. Positive β3-tubulin immunofluorescence staining indicated the surviving SGNs. RIP3 expression was evaluated using immunofluorescence, quantitative real-time polymerase chain reaction and western blot. SGN injury promoted an increase in RIP3 expression that could be suppressed by application of the necroptosis inhibitor Nec-1. A decreased ABR threshold shift and increased SGN density were observed when Nec-1 was administered with apoptosis inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD). These results demonstrated that necroptosis is an indispensable pathway separately from apoptosis leading to SGN death pathway, in which RIP3 plays an important role.

Acoustical stimulus changes the expression of stromal cell-derived factor-1 in the spiral ganglion neurons of the rat cochlea

Neural stem cell (NSC) transplantation into the cochlea has been tested as a treatment for spiral ganglion neuron (SGN) degenerative disease and injury in various animal models. A recent study has shown evidence of functional recovery after transplantation of the stem cells into a degenerated-SGN model. Chemokine stromal cell-derived factor-1 (SDF-1, or known as CXC chemokine ligand-12, CXCL-12) signaling through CXCR4 has previously been identified as a key step in the homing of the stem cells within the injury areas; meanwhile, studies have revealed that the SDF-1/CXCR4 axis is also involved in axon guidance and pathfinding. A study found that transplanted neural precursor cells can migrate to the root of the auditory nerve when animals are subjected to an augmented acoustic environment (AAE). In accordance with these studies, we hypothesize that AAE will up-regulate the expression of SDF-1 in acoustic nerves. We tested our hypothesis by examining the expression of SDF-1 in different acoustic environments, and the results were confirmed by the auditory brainstem response (ABR), immunohistochemical and RT-PCR analyses. The results showed that SDF-1 was expressed at a relatively low level in the SGNs under normal animal unit acoustic conditions (40-50 dB). Moreover, it was significantly up-regulated in the SGNs under the 75 dB (augmented physiological process without hearing loss) and 90 dB AAE (pathological process with light hearing loss) conditions; however, under the 115 dB AAE (pathological process with severe hearing loss) condition, the expression of SDF-1 was not up-regulated. The results confirmed that appropriately augmented acoustical stimuli lead to the up-regulation of SDF-1, which may assist in the migration of the transplanted cells and the subsequent establishment of essential synaptic contacts between the exogenous cells and the host auditory pathway.

G-CSF attenuates noise-induced hearing loss

In this study, we investigated the effects of granulocyte colony-stimulating factor (G-CSF) for the treatment of noise-induced hearing loss (NIHL) in a guinea pig model. Forty guinea pigs were randomly divided into four groups: control, noise (white noise, 3 h/d for 2 days at 115 dB), noise+G-CSF (350 μg/kg/d for 5 days), and noise+saline. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were used to determine the hearing threshold and outer hair cell function, respectively, in each group. Cochlear morphology was examined to evaluate hair cell injury induced by intense noise exposure. Fourteen days after noise exposure, the noise+G-CSF group had a lower ABR value than the noise group (P<0.05) or the noise+saline group (P<0.01). At most frequencies, the DPOAE value of the noise+G-CSF group showed a significant rise (P<0.05) compared to the noise group or the noise+saline group. Neither the ABR value nor the DPOAE value differed between the noise group and the noise+saline group. The morphology of the phalloidin-stained organ of Corti was consistent with the functional measurements. In conclusion, G-CSF can preserve hearing in an experimental model of NIHL in guinea pigs, by preserving hair cells after intense noise exposure.