Bhlhe40 protects cochlear hair cell-like HEI-OC1 cells against H_(2)O_(2) ‑triggered oxidative injury

Background:Cochlear hair cell injury is a common pathological feature of hearing loss.The basic helix-loop-helix family,member e40(Bhlhe40),a gene belonging to the basic helix-loop-helix(bHLH)family,exhibits strong transcriptional repression activity.Methods:Oxidative damage,in House Ear Institute-Organ of Corti 1(HEI-OC1)cells,was caused using hydrogen peroxide(H2O2).The Ad-Bhlhe40 particles were constructed to overexpress Bhlhe40 in HEI-OC1 cells.Various assays including cell counting kit-8(CCK-8),terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay(TUNEL),flow cytometry,immunofluorescence,and corresponding commercial kits were employed to investigate the impacts of Bhlhe40 on cell viability,apoptosis,oxidative stress levels,mitochondrial membrane potential and cellular senescence.Additionally,a dual-luciferase reporter assay was performed to confirm the targeting of the histone deacetylases 2(Hdac2)by Bhlhe40.Results:The results revealed that Bhlhe40 was downregulated in H_(2)O_(2)-treated HEI-OC1 cells,but its overexpression improved cell viability and mitigated H_(2)O_(2)-induced oxidative injury in HEI-OC1 cells with increase of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx)activities and decrease of reactive oxygen species(ROS)levels.Besides,overexpression of Bhlhe40 suppressed H_(2)O_(2)-triggered cell senescence,as evidenced by the fact that the upregulation of P53,P21,and P16 in HEI-OC1 cells treated with H2O2 were all alleviated by Bhlhe40 overexpression.And we further verified that overexpression of Bhlhe40 could inhibit the expression of Hdac2,which may be related to the repression of Hdac2 transcription.Conclusion:This study suggests that Bhlhe40 plays a protective role against senescence and oxidative damage in cochlear hair cells exposed to H2O2.

The role of Rho GTPase family in cochlear hair cells and hearing

Rho GTPases are essential regulators of the actin cytoskeleton.They are involved in various physiological and biochemical processes such as the regulation of cytoskeleton dynamics,development,proliferation,survival,and regeneration.During the development of cochlear hair cells,Rho GTPases are activated by various extracellular signals through membrane receptors to further stimulate multiple downstream effectors.Specifically,RhoA,Cdc42,and Rac1,members of the classical subfamily of the Rho GTPase family,regulate the development and maintenance of cilia by inducing the polymerization of actin monomers and stabilizing actin filaments.In addition,they also regulate the normal morphology orientation of ciliary bundles in auditory hair cells,which is an important element of cell polarity regulation.Moreover,the actin-related pathways mediated by RhoA,Cdc42,and Rac1 also play a role in the motility of outer hair cells,indicating that the function of Rho GTPases is crucial in the highly polar auditory sensory system.In this review,we focus on the expression of RhoA,Cdc42,and Rac1 in cochlear hair cells and how these small molecules participate in ciliary bundle morphogenesis and cochlear hair cell movement.We also discuss the progress of current research investigating the use of these small molecules as drug targets for deafness treatment.

Recent progress in hair follicle stem cell markers and their regulatory roles

Hair follicle stem cells(HFSCs)in the bulge are a multipotent adult stem cell population.They can periodically give rise to new HFs and even regenerate the epidermis and sebaceous glands during wound healing.An increasing number of biomarkers have been used to isolate,label,and trace HFSCs in recent years.Considering more detailed data from single-cell transcriptomics technology,we mainly focus on the important HFSC molecular markers and their regulatory roles in this review.

Notch pathway inhibitor DAPT enhances Atoh1 activity to generate new hair cells in situ in rat cochleae

Atoh1 overexpression in cochlear epithelium induces new hair cell formation. Use of adenovirus-mediated Atoh1 overexpression has mainly focused on the rat lesser epithelial ridge and induces ectopic hair cell regeneration. The sensory region of rat cochlea is difficult to transfect, thus new hair cells are rarely produced in situ in rat cochlear explants. After culturing rat cochleae in medium containing 10% fetal bovine serum, adenovirus successfully infected the sensory region as the width of the supporting cell area was significantly increased. Adenovirus encoding Atoh1 infected the sensory region and induced hair cell formation in situ. Combined application of the Notch inhibitor DAPT and Atoh1 increased the Atoh1 expression level and decreased hes1 and hes5 levels, further promoting hair cell generation. Our results demonstrate that DAPT enhances Atoh1 activity to promote hair cell regeneration in rat cochlear sensory epithelium in vitro.

Correlation of PDCD5 and Apoptosis in Hair Cells and Spiral Ganglion Neurons of Different Age of C57BL/6J Mice

This study examined the expression pattern of programmed cell death 5 (PDCD5) in co-chlear hair cells and spiral ganglion neurons (SGNs) and its association with age-related hearing loss in mice.Sixty C57BL/6J (C57) mice at different ages were divided into four groups (3,6,9 or 12 months).PDCD5 expression was detected by using immunohistochemistry,real-time PCR and Western blot.Morphological change of the cochleae was also evaluated by using immunoassay.The results showed that the expression of PDCD5 had a gradual increase with ageing in both protein and RNA levels in C57 mice,as well as gradually increased apoptosis of cochlear hair cells and SGNs.In addition,we also found that caspase-3 activity was enhanced and its expression was enhanced with ageing.It is implied that overexpression of PDCD5 causes the increase in caspase-3 activity and the subsequent increase of apoptosis in cochlear hair cells and SGNs,and thereby plays a role in the pathogenesis of presbycusis.Thus,PDCD5 may be a new target site for the treatment and prevention of age-related hearing loss.

Rat hair follicle stem cells differentiate and promote recovery following spinal cord injury

Emerging studies of treating spinal cord injury （SCI） with adult stem cells led us to evaluate the effects of transplantation of hair follicle stem cells in rats with a compression-induced spinal cord lesion. Here, we proposed a hypothesis that rat hair follicle stem cell transplantation can promote the recovery of injured spinal cord. Compression-induced spinal cord injury was induced in Wistar rats in this study. The bulge area of the rat vibdssa follicles was isolated, cultivated and characterized with nestin as a stem cell marker. 5-Bromo-2＇-deoxyuridine （BrdU） labeled bulge stem cells were transplanted into rats with spinal cord injury. Immunohistochemical staining results showed that some of the grafted cells could survive and differentiate into oligodendrocytes （receptor-interacting protein positive cells） and neuronal-like cells （~lll-tubulin positive cells） at 3 weeks after transplantation. In addition, recovery of hind limb locomotor function in spinal cord injury rats at 8 weeks following cell transplantation was assessed using the Basso, Beattie and Bresnahan （BBB） locomotor rating scale. The results demon- strate that the grafted hair follicle stem cells can survive for a long time period in vivo and differentiate into neuronal- and glial-like cells. These results suggest that hair follicle stem cells can promote the recovery of spinal cord injury.

Hopf Amplification Originated from the Force-Gating Channels of Auditory Hair Cells

The sense of mammalian hearing exhibits nonlinear phenomena which are most significant to hearing function, such as nonlinear dynamic compression, nonlinear tuning and combination tones. These nonlinear phenomena are suggested to originate from the Hopf amplification within the cochlea, while the mechanism underlying the Hopf amplification remains elusive. According to the experimental results of force-gating channel operation in hair cells, through a theoretic model, this work reveals a velocity-dependent open probability of force-gating channels in auditory hair cells, and a velocity-dependent active force produced by the force-gating channel operating, which makes sensors hear typical Hopf vibrators with nonlinear hearing phenomena.

Mammalin cochlear supporting cells transdifferentiation into outer hair cells

Objective To study the recovery of the outer hair cells in the bat cochlea after gentamicin exposure. Methods Bats were injected with a daily dose of gentamicin for 15 consecutive days and bromodeoxyuridine (BrdU) was given from day 16 to day 40 of this recovery phase. Hearing was assessed by overt acoustic behavior and auditory brainstem responses analysis, which was performed one day prior to the first injection and a day after the last injection (day 16). On day 40 animals were sacrificed for detection of cells that could take up BrdU. Results After 15 days of gentamicin treatment, all of the animals were proved to be deafened with significant increases of ABR thresholds, compared with control group. The findings in immunocytochemical stained samples and scanning electron microscopy revealed that BrdU labeled nuclei were observed in the cochlea in all of the deafened animals most commonly in the regions of the first-row and second-row Deiter’s cells (DCs) and occasionally in the regions of the third-row DCs. Conclusion We suggest that, under sufficient drug and enough time, the bat cochlear supporting cells can directly transdifferentiate into the outer hair cells after aminoglycoside exposure. This transdifferentation process is essential for repair of outer hair cells and recovery of normal function after gentamicin exposure.

Acetylcholine-induced calcium oscillation in isolated outer hair cells in guinea pig

Objective This study is to explore the relationship between acetylcholine(ACh)-induced calcium release from intracellular Ca2+ stores and function of outer hair cell(OHC) motors, in an attempt to elucidate the mechanism of OHC electromotility at resting state. Methods OHCs were isolated from adult guinea pig (200-300 g) cochlea and loaded with Fluo-3/AM. The cells were treated with ACh/dHBSS, ACh/HBSS, dHBSS only or HBSS only. Intracellular [Ca2+]i variations in cells under the four treatments were observed using an Ar-Kr laser scan confocal microscope. Results [Ca2+]i oscillations were recorded in five OHCs treated with ACh/dHBSS but not in other cells. This is the first time that Ach-excited [Ca2+]i oscillations are reported in guinea pig OHCs independent of extracellular calcium. Conclusions ACh-excited [Ca2+]i oscillations in OHCs originates from intracellular calcium release and may play a crucial role in maintaining active mechanical motility of the OHC at resting and modulating OHC electromotility.

Ephrin A2 protein expression in the regeneration and plasticity of cochlear hair cells in chicken following kanamycin ototoxicity

The results from this study showed that the thresholds of brainstem auditory-evoked potentials peak following 10 successive days of intramuscular injection of Roman chickens with kanamycin, starting 3 days after birth. Fluorescence immunohistochemistry analysis revealed few ganglion cells positively labeled for Ephrin A2 in the cochlea of experimental chickens from 2 days before until 7 days after the last kanamycin injection. The number of Ephrin A2-positive ganglion cell bodies was increased at 15 days after the last injection and was similar to that in normal chickens at 30 days following the cessation of kanamycin treatment. These experimental findings indicate that Ephrin A2 protein expression in the acoustic ganglia is synchronized with the connection damage and regeneration of cochlear hair cells after kanamycin exposure. Ephrin A2 may play an important role in the regeneration and plasticity of cochlear hair cells in the chick cochlea following kanamycin ototoxicity.

The progenitors of inner ear hair cells and their regulating genes

Hair cells in the mammalian inner ear are very fragile and are often injured as a result of acoustic trauma or exposure to ototoxic drugs (cisplatin, aminoglycosides, etc) [1]. In amphibians and birds, spontaneous

In vitro Differentiation of Adipose-Derived Stem Cells into Hair Cell-Like Cells in Guinea Pigs

Objective Adipose-derived stem cells(ADSCs) are suggested to possess a highly plastic ability to differentiate into several specific cell types in addition to adipocyte lineages, including germ layer tissue-specific cell lineages such as chondrocyte, myocyte, neuronal, and osteoblast lineages. The aim of this study is to establish an in vitro culture technique for ADSCs in an adult guinea pig model that facilitate their differentiation into hair cell-like cells. Materials and Methods Cells from inguinal fat pads in adult guinea pigs were cultured with β-mercaptoethanol, RA, Forskorin, Heregulin, bFGF, BDNF and EGF. Cellular differentiation was examined using immunocytochemistry techniques. Results The ADSCs demonstrated hair cell immunophenotypes with expression of epitopes of the hair cell marker protein myosin Ⅶa. Conclusion ADSCs from adult guinea pig adipose tissue can differentiate into hair cell-like cells when cultured in vitro. ADSCs may serve as seed cells for tissue engineering.

Muscarinic Acetylcholine Receptor Subtype Expression in Type Vestibular Hair Cells of Guinea Pigs

Recent studies have demonstrated that five subtypes （M1-M5） of muscarinic acetylcholine receptor （mAChR） are expressed in the vestibular periphery. However, the exact cellular location of the mAChRs is not clear. In this study, we investigated whether there is the expression of M1-M5 muscarinic receptor mRNA in isolated type Ⅱ vestibular hair cells of guinea pig by using single-cell RT-PCR. In vestibular end-organ, cDNA of the expected size was obtained by RT-PCR. Moreover, mRNA was identified by RT-PCR from individually isolated type Ⅱ vestibular hair cells （single-cell RT-PCR）. Sequence analysis confirmed that the products were M1-M5 mAChR. These results dem-onstrated that M1-M5 mAChR was expressed in the typeⅡvestibular hair cells of the guinea pig, which lends further support for the role of M1-M5 mAChR as a mediator of efferent cholinergic signalling pathway in vestibular hair cells.

Phosphatidylserine-positive particles in the apical domain of sensory hair cells

Apical membrane recycling has been proposed to be important for normal hair cell function. The current study reports an in vitro work that demonstrates the presence of phosphatidylserine (PS) and PS-positive vesicles labeled by Annexin V in the apical portion of hair cells. The following characteristics of the PS-positive vesicles were noticed using scanning confocal fluorescence microscopy:(1) variable sizes around 200 nm; (2) variable distribution patterns (either uniformly along individual stereocilia in the hair bundle or irregular) in the stereocilia from cell to cell; (3) variable sizes and numbers at locations along the border of the cuticular plate (CP), with a large number of them located at the vestigal kinocilial location; (4) motility with some of the vesicles during the observation period; (5) increase in PS labeling and the number of PS-positive vesicles after loud sound stimulation; and (6) decreased PS labeling and PS-positive vesicle numbers following treatment with LY-294002, a PI3 -kinase inhibitor. These results suggest that the presence of PS-positive vesicles at the apical area of hair cells may be indicative of vesicle shedding or transportation of a protein or rafts.

Basic flbroblast growth factor protects auditory neurons and hair cells from noise exposure and glutamate neurotoxicity

The purpose of the present study was to determine protectivie effects of basic fibroblast growth factor (bFGF) on cochlear neurons and hair cells in vitro and in vivo. In experiment I, cultured spiral ganglion neurons (SGNs) prepared from P3 mice were exposed to 20mM glutamate for 2 hours before the culture medium was replaced with fresh medium containing 0, 25, 50, and 100 ng/ml bFGF, respectively. Fourteen days later, all cultures were fixed with 4% paraformaldehyde, and stained with 1% toluidine blue. The number of surviving SGNs were counted and the length of SGNs neurites were measured. Exposure to 20 mM glutamate for 24 hours resulted in an inhibition on neurite outgrowth of SGNs and elevated cell death. Treatment of the cultures with bFGF led to promotion of neurite outgrowth and elevated number of surviving SGNs. Effects of bFGF were dose dependent with the highest potency at 100 ng/ml. In experiment Ⅱ, in vivo studies were carried out with guinea pigs in which bFGF or artificial perilymph was perfused into the cochlea to assess possible protective effects of bFGF on cochlear hair cells and compound action potentials(CAP). The CAPs were measured before, immediatly and 48 hours after exposure to noise. Significant differences in CAP were observed (p＜0. 05 ) among the bFGF perfused group, control group(t =3. 896 ) and artificial perilymph perfused group (t =2. 520) at 48 hours after noise exposure, Cochleae were removed and hair cell Loss was analyzed in surface preparations prepared from all experimental animals. Acoustic trauma caused loss of 651 and 687 inner hair cells in the control and artificial perilymph perfused group, respectively. In sharp contrast, only 31 inner hair cells were lost in the bFGF perfused ears. Similarly, more outer hair cells died in the control and perilymph perfuesed group (41830 and 41968, respectively) than in the group treated with bFGF (34258). Our results demonstrate that bFGF protected SGNs against glutmate neurotoxicity in vitro. In addition, treatment with bFGF also protected hair cells from acoustic trauma.

Constructing skin-equivalents using hair follicle stem cells

Objective： To establish the method of constructing skin-equivalents （SE） using hair follicle stem cells （HFSC）. Methods： K19 positive cells derived from hair were cultivated using serum-free medium KGM and seeded on dermal equivalents （DE）. After the culture between the air-liquid interface for 14 days, SE were harvested and used for evaluation. Results： K19 positive cells chosen as HFSC were located in bulge of out root sheet in hair follicle. Cultivated HFSC could build a fully developed, multi-layered epidermis on the basis of DE, resembling the skin structure. Conclusion： HFSC located in out root sheet can differentiate into kerafinocyte in vitro and be used for SE construction.

Flavonoids in safflower extract reduce cisplatin-induced damage to human follicle dermal papilla cells by inhibiting DNA damage and Rad17/Chk1/Cdc25C signaling

Background:Cisplatin is a chemotherapeutic agent commonly used clinically for the treatment of various human cancers.Patients often reduce the use of cisplatin due to its side effects,which in turn affects its treatment.This study explored the mechanism of action of safflower extract as an adjuvant traditional Chinese medicine for chemotherapy.Methods:Primary human follicle dermal papilla cells(HFDPCs)were used as target cells for cisplatininduced damage to hair cells.Western blotting was used to investigate the molecular targets of cisplatin and safflower extract in causing HFDPCs damage.Cell survival and cell cycle were analyzed by mitochondrial staining reagent WST-1 and propidium iodide.Results:Cisplatin could reduce the viability of HFDPCs without causing cell death.Cisplatin increased the level of phospho-Rad17 in HFDPCs and activated the Chk1/Cdc25C signaling to reduce the expression of Cdc2 protein,thereby arresting the cells in the G2/M phase.The combination of safflower extract and the flavonoids could effectively inhibit the signal transduction of Rad17/Chk1/Cdc25 in cisplatin-treated cells and reduce the cell population in the G2/M phase.Finally,we also confirmed that safflower extract could effectively inhibit the damage to HFDPCs caused by cisplatin,mainly at the level of reducing the DNA damage caused by cisplatin.Conclusions:Safflower extract can be used as an adjuvant Chinese medicine for chemotherapy to reduce the damage caused by chemotherapy to normal hair follicle cells.

ULTRASTRUCTURAL OBSERVATIONS ON REGENERATING HAIR CELLS IN THE CHICK BASILAR PAPILLA FOLLOWING AMINOGLYCOSIDE OTOTOXICITY

Newly hatched chicks were injected with so mg/(kg' d) of gentamycin sulfate (GM )for 10 days. After 18st injection, animals were killed on survival days 3,6 .9 and 12. The chick basilar papillae (BP) were observed by transmission electron microscopy (TEM ). The results sho've'Ithat regenerated hair cells were erupted to the hasal membrane surrace in the early phase. The cytoplasm of these regenerated hair cells was heavily stained an contained numerous mitochondria. Afterseveral days, stereocilia appeared. When stereocilis bundles were rormed and cuticular layer was integrated, hasal nerve terminals were round. The results suggested that regenerating hair cells 'veredirectly produced on the hasal membrane surface following gentamycin induced ototoxlcity and thenI,roliferated and developed Into mature normal hair cells.

Modulation of copper transporters in protection against cisplatin-induced cochlear hair cell damage

Cisplatin belongs to platinum-based drugs and is widely used in cancer chemotherapy.Ototoxicity is one of the major dose limiting side-effects of cisplatin.For toxicity to occur cisplatin must first be transported from the bloodstream into cochlear cells.Three copper transporters are considered pathways for regulating the uptake and translocation of cisplatin into cells:Ctr1,ATP7A and ATP7B.Our recent study with cochlear organotypic cultures shows that cochlear hair cells can be destroyed by cisplatin at low concentrations from 10μm to 100μn.However,high doses of cisplatin cannot damage hair cells,maybe due to intrinsic feedback reactions that increase export of platinum by ATP7B when the platinum concentration is high in extracellular space.Cimitidine is a specific copper transporter inhibitor that can block the entrance of copper and platinum,and may prevent cisplatin-induced cochlear hair cell injury.To evaluate this hypothesis,we treated cochlear organotypic cultures with cisplatin (10 μm or 50 μm) alone,or cisplatin combined with cimitidine at concentrations ranging from 10-2000 μm for 48 hours.cisplatin at 10 μm damaged about 20% hair cells.In contrast,when cimitidine (10 μm,100 μm and 2000 μm) was added to the culture,near 100% cochlear hair cell survived.At higher concentration (50 μm),cisplatin destroyed about 80% of cochlear hair cells.However,100 μmcimitidine rescued about 50% hair cells from cisplatin damage,and 2000μm cimitidine protected about 80% hair cells.The data of western blot showed that CTR1 and ATP7B expressions were increased in cisplatin treated cochlear tissue,but cimitidine significantly reduced CTR1 and ATP7B.In addition,ATP7A expression was depressed a little after cisplatin treatment.Considering that Ctr1 is involved in copper and platinum influx,but the ATP7A and ATP7B are copper export transporters,the results suggest that cimitidine can effectively block the entrance by copper transporters and stop the influx of cisplatin.