Xueling Wang

Dexamethasone loaded nanoparticles exert protective effects against Cisplatin-induced hearing loss by systemic administration.

Ototoxicity is one of the most important adverse effects of cisplatin chemotherapy. As a common treatment of acute sensorineural hearing loss, systemic administration of steroids was demonstrated ineffective against cisplatin-induced hearing loss (CIHL) in published studies. The current study aimed to evaluate the potential protective effect of dexamethasone (DEX) encapsulated in polyethyleneglycol-coated polylactic acid (PEG-PLA) nanoparticles (DEX-NPs) against cisplatin-induced hearing loss following systemic administration. DEX was fabricated into PEG-PLA nanoparticles using emulsion and evaporation technique as previously reported. DEX or DEX-NPs was administered intraperitoneally to guinea pigs 1h before cisplatin administration. Auditory brainstem response (ABR) threshold shifts were measured at four frequencies (4, 8, 16, and 24kHz) 1 day before and three days after cisplatin injection. Cochlear morphology was examined to evaluate inner ear injury induced by cisplatin exposure. A single dose of DEX-NPs 1h before cisplatin treatment resulted in a significant preservation of the functional and structural properties of the cochlea, which was equivalent to the effect of multidose (3 days) DEX injection. In contrast, no significant protective effect was observed by single dose injection of DEX. The results of histological examination of the cochleae were consistent with the functional measurements. In conclusion, a single dose DEX-NPs significantly attenuated cisplatin ototoxicity in guinea pigs after systemic administration at both histological and functional levels indicating the potential therapeutic benefits of these nanoparticles for enhancing the delivery of DEX in acute sensorineural hearing loss.

Inner ear delivery of dexamethasone using injectable silk-polyethylene glycol (PEG) hydrogel

Minimally invasive delivery and sustained release of therapeutics to the inner ear are of importance to the medical treatment of inner ear disease. In this study, the injectable silk fibroin-polyethylene glycol (Silk-PEG) hydrogel was investigated as a drug delivery carrier to deliver poorly soluble micronized dexamethasone (mDEX) to the inner ear of guinea pigs. Encapsulation of mDEX with a loading up to 5% (w/v) did not significantly change the silk gelation time, and mDEX were evenly distributed in the PEG-Silk hydrogel as visualized by SEM. The loading of mDEX in Silk-PEG hydrogel largely influenced in vitro drug release kinetics. The optimized Silk-PEG-mDEX hydrogel (2.5% w/v loading, in situ-forming, 10 μl) was administered directly onto the round window membrane of guinea pigs. The DEX concentration in perilymph maintained above 100 ng/ml for at least 10 days for the Silk-PEG formulation while less than 12h for the control sample of free mDEX. Minimal systemic exposure was achieved with low DEX concentrations (<0.2 μg/ml) in cerebrospinal fluid (CSF) and plasma in the first 2h after the local application of the Silk-PEG-mDEX hydrogel. A transient hearing threshold shift was found but then resolved after 14 days as revealed by auditory brainstem response (ABR), showing minimal inflammatory responses on the round window membrane and scala taympani. The Silk-PEG hydrogel completely degraded in 21 days. Thus, the injectable PEG-Silk hydrogel is an effective and safe vehicle for inner ear delivery and sustained release of glucocorticoid.

a single dose of dexamethasone encapsulated in polyethylene glycol-coated polylactic acid nanoparticles attenuates cisplatin-induced hearing loss following round window membrane administration

This study aimed to investigate the sustained drug release properties and hearing protection effect of polyethylene glycol-coated polylactic acid (PEG-PLA) stealth nanoparticles loaded with dexamethasone (DEX). DEX was fabricated into PEG-PLA nanoparticles using an emulsion and evaporation technique, as previously reported. The DEX-loaded PEG-PLA nanoparticles (DEX-NPs) had a hydrodynamic diameter of 130±4.78 nm, and a zeta potential of −26.13±3.28 mV. The in vitro release of DEX from DEX-NPs lasted 24 days in phosphate buffered saline (pH 7.4), 5 days in artificial perilymph (pH 7.4), and 1 day in rat plasma. Coumarin 6-labeled NPs placed onto the round window membrane (RWM) of guinea pigs penetrated RWM quickly and accumulated to the organs of Corti, stria vascularis, and spiral ganglion cells after 1 hour of administration. The DEX-NPs locally applied onto the RWM of guinea pigs by a single-dose administration continuously released DEX in 48 hours, which was significantly longer than the free DEX that was cleared out within 12 hours after administration at the same dose. Further functional studies showed that locally administrated single-dose DEX-NPs effectively preserved outer hair cells in guinea pigs after cisplatin insult and thus significantly attenuated hearing loss at 4 kHz and 8 kHz frequencies when compared to the control of free DEX formulation. Histological analyses indicated that the administration of DEX-NPs did not induce local inflammatory responses. Therefore, prolonged delivery of DEX by PEG-PLA nanoparticles through local RWM diffusion (administration) significantly protected the hair cells and auditory function in guinea pigs from cisplatin toxicity, as determined at both histological and functional levels, suggesting the potential therapeutic benefits in clinical applications.

Double heterozygous mutations of MITF and PAX3 result in Waardenburg syndrome with increased penetrance in pigmentary defects

Yang T, Li X, Huang Q, Li L, Chai Y, Sun L, Wang X, Zhu Y, Wang Z, Huang Z, Li Y, Wu H. Double heterozygous mutations of MITF and PAX3 result in Waardenburg syndrome with increased penetrance in pigmentary defects.

A dominant variant in DMXL2 is linked to nonsyndromic hearing loss.

Purpose:To explore the genetic etiology of deafness in a dominant family with late-onset, progressive, nonsyndromic hearing loss.Methods:Genome-wide linkage analysis was performed for 21 family members. Candidate pathogenic variants were identified by whole-exome sequencing of selected family members and confirmed by Sanger sequencing of all family members. Cochlear expression of Dmxl2 was investigated by reverse-transcription polymerase chain reaction (RT-PCR) and immunostaining of the organ of Corti from mice.Results:The causative gene was mapped to a 9.68-Mb candidate region on chromosome 15q21.2 (maximum logarithm of the odds score = 4.03) that contained no previously described deafness genes. Whole-exome sequencing identified heterozygous c.7250G>A (p.Arg2417His) in DMXL2 as the only candidate pathogenic variant segregating the hearing loss. In mouse cochlea, expression of DMXL2 was restricted to the hair cells and the spiral ganglion neurons.Conclusion:Our data indicated that the p.Arg2417His variant in DMXL2 is associated with dominant, nonsyndromic hearing loss and suggested an important role of DMXL2 in inner ear function.Genet Med advance online publication 22 September 2016

Effects of long-term salicylate administration on synaptic ultrastructure and metabolic activity in the rat CNS.

Tinnitus is associated with neural hyperactivity in the central nervous system (CNS). Salicylate is a well-known ototoxic drug, and we induced tinnitus in rats using a model of long-term salicylate administration. The gap pre-pulse inhibition of acoustic startle test was used to infer tinnitus perception, and only rats in the chronic salicylate-treatment (14 days) group showed evidence of experiencing tinnitus. After small animal positron emission tomography scans were performed, we found that the metabolic activity of the inferior colliculus (IC), the auditory cortex (AC), and the hippocampus (HP) were significantly higher in the chronic treatment group compared with saline group (treated for 14 days), which was further supported by ultrastructural changes at the synapses. The alterations all returned to baseline 14 days after the cessation of salicylate-treatment (wash-out group), indicating that these changes were reversible. These findings indicate that long-term salicylate administration induces tinnitus, enhanced neural activity and synaptic ultrastructural changes in the IC, AC, and HP of rats due to neuroplasticity. Thus, an increased metabolic rate and synaptic transmission in specific areas of the CNS may contribute to the development of tinnitus.

Characterization of a knock-in mouse model of the homozygous p.V37I variant in Gjb2

The homozygous p.V37I variant in GJB2 is prevalent in East and Southeast Asians and may lead to mild-to-moderate hearing loss with reduced penetrance. To investigate the pathogenic mechanism underlying this variant, we generated a knock-in mouse model of homozygous p.V37I by an embryonic stem cell gene targeting method. Auditory brainstem response test showed that the knock-in mice developed progressive, mild-to-moderate hearing loss over the first 4–9 months. Overall no significant developmental and morphological abnormality was observed in the knock-in mouse cochlea, while confocal immunostaining and electron microscopic scanning revealed minor loss of the outer hair cells. Gene expression microarray analysis identified 105 up-regulated and 43 down-regulated genes in P5 knock-in mouse cochleae (P < 0.05 adjusted by the Benjamini & Hochberg method), among which four top candidate genes with the highest fold-changes or implication to deafness Fcer1g, Nnmt and Lars2 and Cuedc1 were verified by quantitative real-time PCR. Our study demonstrated that the homozygous p.V37I knock-in mouse modeled the hearing phenotype of the human patients and can serve as a useful animal model for further studies. The differentially expressed genes identified in this study may shed new insights into the understanding of the pathogenic mechanism and the phenotypic modification of homozygous p.V37I.

A Novel p.G141R Mutation in ILDR1 Leads to Recessive Nonsyndromic Deafness DFNB42 in Two Chinese Han Families

Genetic hearing impairment is highly heterogeneous. In this study, targeted next-generation sequencing (NGS) in two Chinese Han families identified a novel p.G141R homozygous mutation in ILDR1 as the genetic cause of the deafness. Consistent with the recessive inheritance, cosegregation of the p.G141R variant with the hearing loss was confirmed in members of both families by PCR amplification and Sanger sequencing. SNP genotyping analysis suggested that those two families were not closely related. Our study showed that targeted NGS is an effective tool for diagnosis of genetic deafness and that p.G141R in ILDR1 may be a relatively frequent mutation for DFNB42 in Chinese Hans.

Genetic analysis of a Chinese family with members affected with Usher syndrome type II and Waardenburg syndrome type IV

AIMS The purpose of this study was to identify the genetic causes of a family presenting with multiple symptoms overlapping Usher syndrome type II (USH2) and Waardenburg syndrome type IV (WS4). METHODS Targeted next-generation sequencing including the exon and flanking intron sequences of 79 deafness genes was performed on the proband. Co-segregation of the disease phenotype and the detected variants were confirmed in all family members by PCR amplification and Sanger sequencing. RESULTS The affected members of this family had two different recessive disorders, USH2 and WS4. By targeted next-generation sequencing, we identified that USH2 was caused by a novel missense mutation, p.V4907D in GPR98; whereas WS4 due to p.V185M in EDNRB. This is the first report of homozygous p.V185M mutation in EDNRB in patient with WS4. CONCLUSION This study reported a Chinese family with multiple independent and overlapping phenotypes. In condition, molecular level analysis was efficient to identify the causative variant p.V4907D in GPR98 and p.V185M in EDNRB, also was helpful to confirm the clinical diagnosis of USH2 and WS4.