Entwicklung einer neuronalen Leitstruktur für die biomimetische Freisetzung von Wachstumsfaktoren im Rahmen der cochleären Regeneration

Geht der Hörsinn eines Menschen verloren, so können die Betroffenen möglicherweise nicht mehr am sozialen Leben teilnehmen. Ausgelöst durch verschiedene Faktoren, wie Traumata oder Krankheiten, kommt es bei den meisten Patienten zu einer sensorischen oder Innenohr-taubheit, bei der jedoch der Hörnerv mit den dort ansässigen Nervenzellen, den Spiralgangli-enneuronen (SGNs), sowie die zentrale Hörbahn intakt vorliegen. Mithilfe des sogenannten Cochlea-Implantats (CI) kann der äußere Schall aufgenommen und in elektrische Impulse um-gewandelt werden, um die SGNs anschließend direkt zu stimulieren. Unter ruhigen Bedingun-gen ist mit dem CI bereits ein ausreichendes Sprachverständnis möglich. Befinden sich die Betroffenen jedoch in einer hohen Geräuschkulisse oder möchten sie Musik wahrnehmen, so liegen Defizite vor. Neben technischen Verbesserungen des Implantats fokussiert sich die ak-tuelle Forschung auf die medikamentöse Behandlung des Innenohres. Vor allem die Neuropro-tektion der SGNs sowie die Regeneration ihrer Neuriten gehören zu den Zielen. Bevorzugt wäre dabei ein Wachstum der Neuriten in Richtung auf das Innenohrimplantat. Hierzu wird im Rahmen dieser Arbeit an einer neuronalen Leitstruktur aus modifizierten, bi-ologisch abbaubaren Polymerfasern gearbeitet, welche die nachwachsenden Neuriten zur Oberfläche der CI-Elektrode leiten soll. Beschichtet mit verschiedenen Biomolekülen der ext-razellulären Matrix, wie Heparansulfat (HS) und Laminin, sowie Wachstumsfaktoren, wie dem brain-derived neurotrophic factor (BDNF), dient die neuronale Leitstruktur zudem als Implantat-assoziiertes Freisetzungssystem, um das biologische Gleichgewicht im Innenohr wiederherzustellen. Als Basismaterial werden Fasern aus Poly-ε-Caprolacton (PCL) und Po-lyglykolsäure (PGA) genutzt, welche bereits vielfältige Anwendung in der Biomedizin fanden. Um die Immobilisierung und die Freisetzung der verschiedenen Biomoleküle gezielt zu steu-ern, wurden neben den unmodifizierten Fasern ebenfalls solche mit frei zugänglichen Amino-gruppen auf der Oberfläche verwendet. Dazu wurden die Fasern aminolysiert, was eine Auf-rauung der Oberfläche zur Folge hatte. Untersuchungen an sowohl un- als auch amino-modi-fizierten Fasern zeigten auf, dass diese innerhalb weniger Wochen im physiologischem Me-dium abgebaut und somit als degradierbare Leitstruktur eingesetzt werden können. HS konnte kovalent auf der Oberfläche immobilisiert werden, um in einem biomimetischen Ansatz BDNF anzubinden und langanhaltend und kontrolliert wieder abzugeben. In Release-Experi-menten wurde von den amino-modifizierten Fasern weniger BDNF freigesetzt als von den unmodifizierten Fasern. Dies kann möglicherweise auf stärkere hydrophobe Wechselwirkun-gen zwischen dem Wachstumsfaktor und der Faseroberfläche zurückgeführt werden. Sowohl freigesetztes BDNF als auch der direkte Kontakt mit den BDNF-beladenen Fasern erhöhte die Überlebensrate der SGNs. Die vorliegenden Ergebnisse deuten zwar auf einen klaren neu-roprotektiven Effekt des BDNFs hin, ein neuroregenerativer Effekt ist jedoch zweifelhaft, da sich die mittlere Neuritenlänge hier nicht ändert. Für eine detailliertere Betrachtung der Neu-roregeneration wurden Experimente mit SGN-Strangstücken durchgeführt und es wurde, um quantitative Daten zu erhalten, die Sholl-Analyse für das hier vorliegende System weiterent-wickelt. Diese Untersuchungen zeigen, dass die Neuritenaussprossung durch die BDNF-tra-genden Fasern vermehrt und die maximale Neuritenlänge gesteigert wird. Auch die mittlere Neuritenaktivität, welche sich aus der Anzahl sowie der mittleren Länge der Neuriten zusam-mensetzt, erhöht sich durch BDNF. Größere Mengen des Wachstumsfaktors verstärken die beobachteten Effekte. Ein gerichtetes Wachstum der Neuriten durch die Zugabe von BDNF war nicht zu erkennen. Auch konnte kaum eine Wirkung von HS auf die Zellen beobachtet werden. Um den nachwachsenden Neuriten in der biomedizinischen Anwendung Ankerpunkte auf ihrem Weg entlang der Fasern zur CI-Oberfläche zu bieten, sollten diese mit Laminin be-schichtet werden. Vorläufige Untersuchungen hierzu deuten darauf hin, dass dies möglich ist.If a person's hearing is lost, it can mean that those affected can no longer participate in social life. Triggered by various factors, like traumas or diseases, most patients experience sensory or inner ear deafness, in which, however, the auditory nerve with the nerve cells located there, the spiral ganglion neurons (SGNs), as well as the central auditory pathway are still intact.With the help of the so-called cochlear implant (CI), the external sound can be recorded and con-verted into electrical impulses in order to then directly stimulate the SGNs. With the CI, a sufficient understanding of language is already possible under quiet conditions. However, at a high level of background noise or at listening to music, several deficits appear. In addition to technical improvements of the implant, current research focuses on drug treatments of the inner ear. Major goals are the neuroprotection of the SGNs and the regeneration of their neu-rites. Preferably, growth of the neurites should be directed towards the inner ear implant. For this purpose, within the scope of this work, a neuronal guidance scaffold made of modified, biodegradable polymer fibers is developed which should guide the regrowing neurites to the surface of the CI electrode. Coated with various biomolecules of the extracellular matrix, such as heparan sulfate (HS) and laminin, as well as growth factors such as the brain-derived neu-rotrophic factor (BDNF), it also serves as an implant-associated drug delivery system to re-store the biological balance in the inner ear. Fibers made out of poly-ε-caprolactone (PCL) and polyglycolic acid (PGA) are used as the base material, which have already been used in various ways in biomedicine. In order to control the immobilization and the release of the various biomolecules in a targeted manner, fibers with freely accessible amino groups on the surface were also used in addition to the unmodified fibers. For this purpose, the unmodified fibers were aminolyzed, which re-sulted in a roughening of the surface. Investigations on both unmodified and amino-modified fibers showed that they degrade in a physiological medium within a few weeks and thus can be used as biodegradable guidance structure. HS could be immobilized covalently on the sur-face in order to bind BDNF in a biomimetic approach and to release it again in a long-lasting, controlled manner. In release experiments, less BDNF was released from the amino-modified fibers than from the unmodified fibers. This can be attributed to stronger hydrophobic interac-tions between the growth factor and the fiber surface. Both, released BDNF and the direct contact with BDNF-loaded fibers increased the survival rate of the SGNs. Although the avail-able results indicate a clear neuroprotective effect of the BDNF, a neuroregenerative effect is doubtful, since the mean neurite length does not change. For a more detailed investigation on neuroregeneration, studies on SGN explants were performed and, in order to obtain quantita-tive data, were evaluated using the Sholl analysis which was adapted and further developed for the system investigated here. These investigations show that neurite sprouting by BDNF fibers as well as the maximum neurite length both increased. The mean neurite activity, which is composed of the number and the mean length of the neurites, is also increased by BDNF. Larger amounts of the growth factor amplify the observed effects. Directed growth of the neu-rites through the addition of BDNF could not be shown. Also, hardly any effect of HS on the cells could be observed. In order to provide the regrowing neurites in biomedical applications with anchor points on their way along the fibers to the CI surface, they should be coated with laminin. Initial investigations indicate in this direction show that this should be possible

Development of Neuronal Guidance Fibers for Stimulating Electrodes: Basic Construction and Delivery of a Growth Factor

State-of-the-art treatment for sensorineural hearing loss is based on electrical stimulation of residual spiral ganglion neurons (SGNs) with cochlear implants (CIs). Due to the anatomical gap between the electrode contacts of the CI and the residual afferent fibers of the SGNs, spatial spreading of the stimulation signal hampers focused neuronal stimulation. Also, the efficiency of a CI is limited because SGNs degenerate over time due to loss of trophic support. A promising option to close the anatomical gap is to install fibers as artificial nerve guidance structures on the surface of the implant and install on these fibers drug delivery systems releasing neuroprotective agents. Here, we describe the first steps in this direction. In the present study, suture yarns made of biodegradable polymers (polyglycolide/poly-ε-caprolactone) serve as the basic fiber material. In addition to the unmodified fiber, also fibers modified with amine groups were employed. Cell culture investigations with NIH 3T3 fibroblasts attested good cytocompatibility to both types of fibers. The fibers were then coated with the extracellular matrix component heparan sulfate (HS) as a biomimetic of the extracellular matrix. HS is known to bind, stabilize, modulate, and sustainably release growth factors. Here, we loaded the HS-carrying fibers with the brain-derived neurotrophic factor (BDNF) which is known to act neuroprotectively. Release of this neurotrophic factor from the fibers was followed over a period of 110 days. Cell culture investigations with spiral ganglion cells, using the supernatants from the release studies, showed that the BDNF delivered from the fibers drastically increased the survival rate of SGNs in vitro. Thus, biodegradable polymer fibers with attached HS and loaded with BDNF are suitable for the protection and support of SGNs. Moreover, they present a promising base material for the further development towards a future neuronal guiding scaffold. Copyright © 2022 Wille, Harre, Oehmichen, Lindemann, Menzel, Ehlert, Lenarz, Warnecke and Behrens

Heilende Implantate : Kontrollierte Wirkstoff-Freisetzung von Hör-Prothesen

Medikamente können dazu beitragen, dass ein Cochlea-Implantat im Ohr des Patienten besser funktioniert. Daher arbeiten Wissenschaftlerinnen und Wissenschaftler vom Institut für Anorganische Chemie sowie der Klinik für Hals-, Nasen-, Ohrenheilkunde an der Medizinischen Hoch-schule Hannover (MHH) gemeinsam an einer lokalen und kontrollierten Wirkstoff-Freisetzung, die direkt vom Implantat ausgeht

Genome-wide association identifies nine common variants associated with fasting proinsulin levels and provides new insights into the pathophysiology of type 2 diabetes.

OBJECTIVE: Proinsulin is a precursor of mature insulin and C-peptide. Higher circulating proinsulin levels are associated with impaired β-cell function, raised glucose levels, insulin resistance, and type 2 diabetes (T2D). Studies of the insulin processing pathway could provide new insights about T2D pathophysiology. RESEARCH DESIGN AND METHODS: We have conducted a meta-analysis of genome-wide association tests of ∼2.5 million genotyped or imputed single nucleotide polymorphisms (SNPs) and fasting proinsulin levels in 10,701 nondiabetic adults of European ancestry, with follow-up of 23 loci in up to 16,378 individuals, using additive genetic models adjusted for age, sex, fasting insulin, and study-specific covariates. RESULTS: Nine SNPs at eight loci were associated with proinsulin levels (P < 5 × 10(-8)). Two loci (LARP6 and SGSM2) have not been previously related to metabolic traits, one (MADD) has been associated with fasting glucose, one (PCSK1) has been implicated in obesity, and four (TCF7L2, SLC30A8, VPS13C/C2CD4A/B, and ARAP1, formerly CENTD2) increase T2D risk. The proinsulin-raising allele of ARAP1 was associated with a lower fasting glucose (P = 1.7 × 10(-4)), improved β-cell function (P = 1.1 × 10(-5)), and lower risk of T2D (odds ratio 0.88; P = 7.8 × 10(-6)). Notably, PCSK1 encodes the protein prohormone convertase 1/3, the first enzyme in the insulin processing pathway. A genotype score composed of the nine proinsulin-raising alleles was not associated with coronary disease in two large case-control datasets. CONCLUSIONS: We have identified nine genetic variants associated with fasting proinsulin. Our findings illuminate the biology underlying glucose homeostasis and T2D development in humans and argue against a direct role of proinsulin in coronary artery disease pathogenesis

The extraordinary March 2022 East Antarctica “heat” wave. Part II: impacts on the Antarctic ice sheet

International audienceBetween March 15-19, 2022, East Antarctica experienced an exceptional heatwave with widespread 30-40° C temperature anomalies across the ice sheet. In Part I, we assessed the meteorological drivers that generated an intense atmospheric river (AR) which caused these record-shattering temperature anomalies. Here in Part II, we continue our large, collaborative study by analyzing the widespread and diverse impacts driven by the AR landfall. These impacts included widespread rain and surface melt which was recorded along coastal areas, but this was outweighed by widespread, high snowfall accumulations resulting in a largely positive surface mass balance contribution to the East Antarctic region. An analysis of the surface energy budget indicated that widespread downward longwave radiation anomalies caused by large cloud-liquid water contents along with some scattered solar radiation produced intense surface warming. Isotope measurements of the moisture were highly elevated, likely imprinting a strong signal for past climate reconstructions. The AR event attenuated cosmic ray measurements at Concordia, something previously never observed. Finally, an extratropical cyclone west of the AR landfall likely triggered the final collapse of the critically unstable Conger Ice Shelf while further reducing an already record low sea-ice extent

The extraordinary March 2022 East Antarctica “heat” wave. Part I: observations and meteorological drivers

International audienceBetween March 15-19, 2022, East Antarctica experienced an exceptional heatwave with widespread 30-40° C temperature anomalies across the ice sheet. This record-shattering event saw numerous monthly temperature records being broken including a new all-time temperature record of -9.4° C on March 18 at Concordia Station despite March typically being a transition month to the Antarctic coreless winter. The driver for these temperature extremes was an intense atmospheric river advecting subtropical/mid-latitude heat and moisture deep into the Antarctic interior. The scope of the temperature records spurred a large, diverse collaborative effort to study the heatwaves meteorological drivers, impacts, and historical climate context. Here we focus on describing those temperature records along with the intricate meteorological drivers that led to the most intense atmospheric river observed over East Antarctica. These efforts describe the Rossby wave activity forced from intense tropical convection over the Indian Ocean. This led to an atmospheric river and warm conveyor belt intensification near the coastline which reinforced atmospheric blocking deep into East Antarctica. The resulting moisture flux and upper-level warm air advection eroded the typical surface temperature inversions over the ice sheet. At the peak of the heatwave, an area of 3.3 million km2 in East Antarctica exceeded previous March monthly temperature records. Despite a temperature anomaly return time of about one hundred years, a closer recurrence of such an event is possible under future climate projections. In a subsequent manuscript, we describe the various impacts this extreme event had on the East Antarctic cryosphere