Detection of BDNF-Related Proteins in Human Perilymph in Patients With Hearing Loss

Abstract

The outcome of cochlear implantation depends on multiple variables including the underlying health of the cochlea. Brain derived neurotrophic factor (BDNF) has been shown to support spiral ganglion neurons and to improve implant function in animal models. Whether endogenous BDNF or BDNF-regulated proteins can be used as biomarkers to predict cochlear health and implant outcome has not been investigated yet. Gene expression of BDNF and downstream signaling molecules were identified in tissue of human cochleae obtained from normal hearing patients ( n = 3) during skull base surgeries. Based on the gene expression data, bioinformatic analysis was utilized to predict the regulation of proteins by BDNF. The presence of proteins corresponding to these genes was investigated in perilymph ( n = 41) obtained from hearing-impaired patients ( n = 38) during cochlear implantation or skull base surgery for removal of vestibular schwannoma by nanoscale liquid chromatography coupled to tandem mass spectrometry (nano LC-MS/MS). Analyzed by mass spectrometry were 41 perilymph samples despite three patients undergoing bilateral cochlear implantation. These particular BDNF regulated proteins were not detectable in any of the perilymph samples. Subsequently, targeted analysis of the perilymph proteome data with Ingenuity Pathway Analysis (IPA) identified further proteins in human perilymph that could be regulated by BDNF. These BDNF regulated proteins were correlated to the presence of residual hearing (RH) prior to implantation and to the performance data with the cochlear implant after 1 year. There was overall a decreased level of expression of BDNF-regulated proteins in profoundly hearing-impaired patients compared to patients with some RH. Phospholipid transfer protein was positively correlated to the preoperative hearing level of the patients. Our data show that combination of gene expression arrays and bioinformatic analysis can aid in the prediction of downstream signaling proteins related to the BDNF pathway. Proteomic analysis of perilymph may help to identify the presence or absence of these molecules in the diseased organ. The impact of such prediction algorithms on diagnosis and treatment needs to be established in further studies.

In‐depth proteome of perilymph in guinea pig model

“…In addition, several epidermal growth factor (EGF)-and transforming growth factor beta (TGFβ)-related extracellular matrix and membrane proteins, such as EFEMP1, EGFR, collagens, and TGFBI, known to be crucial for hearing [24,25], were identified. Moreover, many proteins, including SERPINA3, SPP1, PLTP, NCAM1, FTL, MBP, AGRN, RELN, PTPRK, and PLXNB2, were detected in perilymph, which is correlated with the previous reported human perilymph proteome data associated with cochlear health [20].…”

“…The dynamic range of proteins expressed in perilymph, estimated using total intensity value in 48 LC-MS/MS runs, spanned seven orders of magnitude (Figure 2A). Several proteins related to hearing loss were identified across the whole measuring range of perilymph proteome [20]. To assess the link between relative protein abundance and biological functions, we divided the proteome into four quantiles (Q1-Q4) based on the estimated protein abundances (Figure 2A).…”

Potential Molecular Biomarkers of Vestibular Schwannoma Growth: Progress and Prospects

“…With several over-expressed neurotrophic factors in VS drawn attention as putative key mediators of tumor growth, Kramer et al. explored the relationship between gene expression profiles of neurotrophic factors and proliferation-associated Ki-67 labelling index, and observed significantly elevated brain derived neurotrophic factor (BDNF) expression that correlated with mitotic activity in VS ( 38 ).BDNF plays a pivotal role in myelination processing and supports the survival and synaptic integrity of the auditory nerve ( 145 ). This mitosis-promoting neurotrophic factor, together with the previously mentioned bFGF, which has the dual effects of hearing protection and growth stimulation of VS cells ( 16 , 75 ), may partially explain the seemingly paradoxical phenomenon that VS patients with tumor growth do not necessarily experience hearing loss.…”

Distinct MicroRNA Profiles in the Perilymph and Serum of Patients With Menière's Disease

“…As a result of these shortcomings, there is significant interest in obtaining a “liquid biopsy” equivalent of the inner ear. Many investigators are analyzing the components of inner ear fluid to gain insights into what may be occurring on a molecular level in active inner ear disease states ( 7 – 12 ).…”