Medical University of Hannover (MHH)

Legal address of MHH:

Medizinische Hochschule Hannover
HNO-Klinik, OE 6500
Carl-Neuberg-Strasse 1
30625 Hannover, GER

Partner information

Researchers:

Prof. Dr. Thomas Lenarz, chairman
Assoc. prof. Timo Stöver, group leader
Dr. Kirsten Wissel, biochemist
Verena Scheper, veterinarian

Description of Partner

The cochlear implant (CI) has become the "success story" of neuroprosthetic devices. The development of CI enables most implanted patients to attain high levels of speech discrimination. However, speech understanding is variable in individuals and depends significantly on the state of survival and excitability of the auditory nerve cell bodies locating in the spiral ganglion cells (SGC). Therefore, the overall focus of research activities is the development of therapies to prevent and attend hearing loss caused by destruction of the sensory cells (hair cells) resulting in secondary degeneration of the afferent auditory nerve fibers. Furthermore, induction of the regeneration mechanisms of the auditory nerve following hearing loss will play a key role in rehability of natural hearing. There is an increasing evidence that neurotrophic factors (NTF), especially members of the TGF-beta superfamily and brain derived neurotrophic factor (BDNF)-family, play key roles in protection of SGC and enhance the functional excitability of the auditory nerve fibers after drug- and noise-induced trauma. Beside stem cell therapies and gene transfer application of functionalized nanoparticles to the target tissues for drug delivery may become important features in inner ear therapies. Partner 7 focuses on determinations in preventing the degeneration of the auditory nerve and induction of regeneration mechanisms of the nerve fibres and its cell bodies, the spiral ganglion cells (SGC), by using MFNP. For that purpose biological degradable NP made of PLGA, PCL, chitosan, silica compounds, liposomes and micelles will be determined by their cytotoxicity, distribution, uptake and targetibility into sensory cells and SGC, and their bioefficiacy in vivo. As well the NP will be "multi-functionalized" by coating with biotin and i.e. brain derived neurotrophic factor (BDNF) which is known as a potential survival factor for prevention auditory nerve degeneration. The targetibility and biological effects of the nanoparticles will be evaluated in the animal-model of normal hearing and profoundly deafened guinea pigs. Detection and characterization of distribution, cytotoxicity, targeting and bioefficiacy of the MFNP in cochlea tissues is basing on immunohistochemical methods and microscope assessment as well as gene expression profiling by real time-PCR techniques. In detail, cytotoxicity of certain MFNP in vivo may be determined by hematoxylin staining of cochlear sections to characterise the effects of NP in morphology of SGC or others. Immunohistochemical detection of certain inflammatory mediators and apoptose markers by using fluorescence microscopy, i.e. confocal laser scanning microscopy, will give more detailed informations about (non)cytotoxicity of certain nanoparticles in normal hearing animals. Key features in this project are not only the bioefficiacy of the MFNP, but also their distribution and cell-targetibility within the inner ear depending on their labelling characteristics. Detection of the nanoparticles in singles cells or specific cell compartment is facilitated by labelling with biotin or green fluorescent protein (GFP). Whereas GFP can be directly measured within the cochlea at the emission wavelength of approximately 501 nm, the biotin labelled nanoparticles have to be captured by streptavidin, conjugated with fluorochrome. Distribution and targeting of the nanoparticles can only be characterised by using high resolution fluorescence microscopy, especially confocal laser scanning microscopy or transmission electron microscopy. In terms of bioefficiacy beneficial effects of i.e. BDNF labelled MFNP in deafened animals may be demonstrated not only by the survival rate of SGC in comparison to normal hearing animals, but also by expression of neuronal proteins, transcription factors, ion channels or by the absence of apoptose inducing mediators using immunohistochemical methods and fluorescence microscopy. Additionally, gene expression profiling from laser microdissected cochlear tissues (laser microdissection pressure catapulting-technique) may support data access from protein detection methods on RNA level by using real time-PCR (rtPCR). Moreover, the very sensitive rtPCR allows not only detection of rarely expressed RNA, but also quantification of small changes in specific RNA expression.