Biology subjects

Hansen, M. R.

Publications and source records attributed to Hansen, M. R..

15 recordsLinked to original sources

bioRxiv2026

Establishment of a cochlear lymphatic vascular network and immune surveillance system following cochlear implantation

Hearing loss is a highly prevalent sensory abnormality often addressed with cochlear implants (CI) that provide auditory rehabilitation for deaf patients. However, a universal inflammatory foreign body response (FBR) to the implanted materials negatively impacts CI outcomes. The mechanistic basis for immune cell infiltration and propagation of the FBR directed against CIs is not defined. Using mouse CI models and quantitative, highly tractable reporters for lymphatics, blood vessels, and immune cells, we identify inner ear lymphatic vessels and changes to the immune surveillance system following cochlear implantation. Histopathological analysis of implanted temporal bones from human subjects shows that both blood vessels and lymphatics are evident within the scala tympani of the implanted cochlea. Our data reveal a rich lymphatic vascular network in the inner ear, closely associated with the perilymphatic and endolymphatic spaces. Lymphatics proliferate within the perilymphatic space of the implanted cochleae and appear to traffic immune cells. Together, our data provide direct evidence that concurrent proliferation of blood vessels and recruitment of blood-borne immune cells comprise an 'immune surveillance system' in the implanted cochleae that promotes the FBR. Our findings also highlight potential opportunities to limit adverse FBR outcomes following cochlear implantation.

systems biology↗

bioRxiv2026

Long-term mitigation of the foreign-body response with dexamethasone-eluting cochlear implants in mice

The inflammatory foreign body response that follows cochlear implantation produces intracochlear fibrosis, neo-ossification, and elevated electrode impedances that can compromise implant performance. Dexamethasone-eluting cochlear implants reduce this response, but the durability of their anti-inflammatory effect over long implantation intervals has not been established. Using a murine model of chronic cochlear implantation in CX3CR1+/eGFP Thy1+/eYFP dual-reporter mice, we compared dexamethasone-eluting and standard mouse cochlear implants at 224 and 336 days post-implantation. Density of CX3CR1+ macrophages, MHCII+CX3CR1+ antigen-presenting macrophages, -SMA+ fibrosis, and neo-ossification were quantified in the scala tympani, Rosenthal canal, and lateral wall of the basal turn. Standard implants produced persistent macrophage and antigen-presenting macrophage infiltration, accompanied by an -SMA+ fibrotic response and neo-ossification. Dexamethasone-eluting implants suppressed macrophage infiltration in all three regions out to 336 days and reduced fibrosis at 224 days. In the subset of cochleae with electrode array translocation, dexamethasone-eluting implants attenuated macrophage infiltration and confined the fibrotic and osseous response to the site of translocation, whereas standard implants produced a widespread response. A reduction in immune cell density was also observed in the contralateral, unimplanted cochleae of animals implanted with dexamethasone-eluting implants, suggesting a wider component to the drug's effect. Dexamethasone-eluting cochlear implants therefore provide sustained, long-term suppression of the cochlear foreign body response in mice, supporting their continued translation toward clinical application. This effect was associated with continued low-level dexamethasone elution out to 336 days post-implantation; further work is needed to assess the durability of this effect at the conclusion of drug elution.

neuroscience↗

bioRxiv2026

Presynaptic CaV2.1 calcium dependent facilitation is essential for faithful auditory information transfer

Activity-dependent modulation of presynaptic voltage-gated Ca2+ channels (CaV2) regulates Ca2+ influx to control neuronal circuit output. Although CaV2.1 can undergo robust Ca2+ dependent facilitation (CDF), whether it occurs in native central nervous system neuronal circuits is disputed. Accurate auditory information processing requires precise and reliable synaptic transmission at high activity rates in the auditory brainstem. To determine if CaV2.1 CDF is a key regulator of high-fidelity synaptic transmission, we expressed CaV2.1 splice variants capable (CaV2.1 37a) or incapable (CaV2.1 37b) of CDF at the calyx of Held presynaptic terminal in the auditory brainstem. We found no difference in basal CaV2.1 currents or synaptic transmission. However, CaV2.1 37b terminals lacked CDF, synaptic facilitation and had a decreased reliability and precision of postsynaptic action-potential firing. Additionally, the Wave III amplitude of the auditory brainstem responses was reduced. We propose that CaV2.1 CDF is essential for accurate auditory information processing.

neuroscience↗

bioRxiv2025

Adult mice with neonatal-like T cell subsets exhibit increased susceptibility to Bordetella pertussis and influenza infection

Infants are significantly more susceptible to respiratory infection, often resulting in increased morbidity and hospitalization, and occasionally death. This susceptibility is partially explained by the developing nature of the thymus in human infants at, and for several months after, birth. However, the contribution of T cells produced in this thymic microenvironment to infant immune responses has received minimal investigation. Here, we utilized a previously described mouse model (Foxn1{Delta}/{Delta}) which exhibits a persistently immature thymus. Through further characterization, we have determined that adult Foxn1{Delta}/{Delta} mice retain some unique T cells observed in neonatal mice including CD8{beta}+ {gamma}{delta} T cells and CD8 T cells displaying a memory-like phenotype. For this reason, we assessed the potential of these neonatal-like T responses to two pathogens which disproportionately affect neonates, Bordetella pertussis (Bp) and influenza. Utilizing these infections, we demonstrate that T cells generated in an incompletely developed thymus fail to control or mount an effective response against Bp. We also observe that Foxn1{Delta}/{Delta} mice control acute influenza infection, a response which does not require IL-17. However, the Foxn1{Delta}/{Delta} mice fail to generate an influenza nucleoprotein (NP) specific CD8+ T cell response which is likely associated with their inability to fully clear the infection. Together, these data suggest that Foxn1{Delta}/{Delta} mice can be utilized to study the generation, function, and persistence of some unique T cells made in a neonatal-like thymus.

immunology↗

bioRxiv2025

Memory Regulatory T Cells Reprogram into Protective Tfh-like Effectors in Recurrent Malaria

Although people living in malaria-endemic areas experience repeated infections with Plasmodium, the role of regulatory T cells (Tregs) in recurrent malaria remains poorly understood. During a primary infection with Plasmodium, Tregs suppress protective immunity by inhibiting germinal center (GC) reactions, thereby impeding the control of parasitemia. In contrast, we demonstrate here that memory Tregs (mTregs) remaining after the clearance of initial Plasmodium infection acquire protective functions upon recall. Relying on longitudinal studies in humans and mice, we show that mTregs undergo antigen-driven expansion and inflammation-induced epigenetic reprogramming during reinfection to transition from Foxp3+ immunosuppressive cells to Bcl6+ follicular T helper (Tfh)-like effectors. These mTreg-derived Tfh-like cells enhance GC responses and the generation of Plasmodium-specific antibodies, ultimately facilitating Plasmodium control. Precluding such mTreg-to-Tfh differentiation abolished protection. Our findings reveal a previously unrecognized adaptive plasticity in canonical mTregs that enables a context-dependent functional switch from immunoregulatory to protective effectors during recurrent infections.

immunology↗

bioRxiv2025

Dextran-based T-cell expansion nanoparticles for manufacturing CAR T cells with augmented efficacy

Adoptive T cell therapy (ACT) using chimeric antigen receptor (CAR) engineered T cells is currently being explored in multiple cancer types beyond leukemia/lymphoma. A key step in CAR-T cell manufacturing is the activation and expansion of T cells, which facilitates viral transduction, however, may hamper T cell fitness and reduce in vivo persistence. We developed "T-Expand" for T cell activation and expansion, comprising dextran-based nanoparticles (NPs) conjugated with anti-CD3 and anti-CD28 antibodies. The NPs triggered robust polyclonal expansion of human T cells with efficiency in the range of commercial microbeads (Dynabeads). Engineered in presence of T-Expand, CD19 CAR T cells exhibited enhanced proliferative capacity, cytotoxicity and persistence in vitro, and furthermore, showed superior anti-lymphoma activity in mouse models resulting in complete tumor clearance at one fourth of the CAR T cell dose. Importantly, T-Expand is biocompatible with no observed toxicity, circumventing removal steps after T cell expansion compared to DynabeadsTM. As a biocompatible T cell expansion platform, T-Expand simplifies the manufacturing process while enhancing T cell persistence and functionality, thereby holding promise for increasing clinical efficacy of CAR T cell therapy. O_FIG O_LINKSMALLFIG WIDTH=165 HEIGHT=200 SRC="FIGDIR/small/648181v1_ufig1.gif" ALT="Figure 1"> View larger version (74K): org.highwire.dtl.DTLVardef@35337corg.highwire.dtl.DTLVardef@c75199org.highwire.dtl.DTLVardef@1be184forg.highwire.dtl.DTLVardef@12e1683_HPS_FORMAT_FIGEXP M_FIG Graphical abstract/Cover figureIllustration of CAR T cell manufacturing using T-Expands ex vivo. C_FIG

immunology↗

bioRxiv2024

Sex-specific thermoregulatory effects of estrogen signaling in Reprimo lineage cells

Estrogens have considerable impact on energy homeostasis and metabolic health. In mice, signaling through estrogen receptor alpha (ER) alters energy intake and multiple aspects of energy expenditure, effects that may be mediated by specific regions or neuronal sub-populations of the hypothalamus. This study investigates the function of ER in neurons of the lineage that expresses Rprm (Reprimo), a gene we previously linked to thermoregulation in females. Here, we engineered a novel ReprimoCre mouse to selectively knock out ER in Rprm lineage cells (Reprimo-specific estrogen receptor KO; RERKO) and report changes in core temperature in female mice, with no changes in movement or food intake. RERKO females have elevated brown adipose tissue (BAT) temperature and lower tail temperature relative to controls, suggesting increased heat production and reduced heat dissipation, respectively. Developmental expression of Rprm was detected in the brain, but not in BAT or white adipose tissue suggesting temperature changes may be mediated by the nervous system. To confirm centrally mediated effects on temperature, we ablated Rprm expressing cells in the mediobasal hypothalamus and observed a reduction in core temperature relative to controls. Taken together, these results indicate that estrogen signaling in the Rprm lineage is critical for thermoregulation, mainly through the modulation of brown adipose tissue thermogenesis in female, but not male, mice.

physiology↗

bioRxiv2024

Supervised Automation of Cell Counting in Confocal Microscopic Cochlear Imaging Datasets Using Macro in Imaris

Analyzing confocal microscopic data of biological samples using the Imaris software poses challenges due to its time-consuming nature involving tedious multiple steps and possibility of human errors. Here, we developed a supervised automation protocol to minimize manual input in cell and spot counting on confocal images obtained from mouse cochlear sections. The protocol increases efficiency by incorporating image recognition and object-oriented macros. Moreover, the protocol being adaptable allows scientists in diverse other fields to customize it for their specific needs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/604970v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@11b4aa0org.highwire.dtl.DTLVardef@c08c7dorg.highwire.dtl.DTLVardef@1479b59org.highwire.dtl.DTLVardef@280227_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

The geometry of photopolymerized topography influences neurite pathfinding by directing growth cone morphology and migration

Cochlear implants (CIs) provide auditory perception to those with profound sensorineural hearing loss: however, the quality of sound perceived by a CI user does not approximate natural hearing. This limitation is due in part to the large physical gap between the stimulating electrodes and their target neurons. Therefore, directing the controlled outgrowth of processes from spiral ganglion neurons (SGNs) into close proximity to the electrode array could provide significantly increased hearing function. For this objective to be properly designed and implemented, the ability and limits of SGN neurites to be guided must first be determined. In this work, we engineered precise topographical microfeatures with angle turn challenges of various geometries to study SGN pathfinding. Additionally, we analyze sensory neurite growth in response to topographically patterned substrates and use live imaging to better understand how neurite growth is guided by these cues. In assessing the ability of neurites to sense and turn in response to topographical cues, we find that the geometry of the angled microfeatures determines the ability of neurites to navigate the angled microfeature turns. SGN neurite pathfinding fidelity can be increased by 20-70% through minor increases in microfeature amplitude (depth) and by 25% if the angle of the patterned turn is made more obtuse. Further, by using engineered topographies and live imaging of dorsal root ganglion neurons (DRGNs), we see that DRGN growth cones change their morphology and migration to become more elongated within microfeatures. However, our observations also indicate complexities in studying neurite turning. First, as the growth cone pathfinds in response to the various cues, the associated neurite often reorients across the angle topographical microfeatures. This reorientation is likely related to the tension the neurite shaft experiences when the growth cone elongates in the microfeature around a turn. Additionally, neurite branching is observed in response to topographical guidance cues, most frequently when turning decisions are most uncertain. Overall, the multi-angle channel micropatterned substrate is a versatile and efficient system to assess SGN neurite turning and pathfinding in response to topographical cues. These findings represent fundamental principles of neurite pathfinding that will be essential to consider for the design of 3D systems aiming to guide neurite growth in vivo.

bioengineering↗

bioRxiv2022

Reducing the foreign body response on human cochlear implants and their materials in vivo with photografted zwitterionic hydrogel coatings

The foreign body response to implanted materials often complicates the functionality of sensitive biomedical devices. For cochlear implants, this response can reduce device performance, battery life and preservation of residual acoustic hearing. As a permanent and passive solution to the foreign body response, this work investigates ultra-low-fouling poly(carboxybetaine methacrylate) (pCBMA) thin film hydrogels that are simultaneously photo-grafted and photo-polymerized onto polydimethylsiloxane (PDMS). The cellular anti-fouling properties of these coatings are robustly maintained even after six-months subcutaneous incubation and over a broad range of cross-linker compositions. On pCBMA-coated PDMS sheets implanted subcutaneously, capsule thickness and inflammation are reduced significantly in comparison to uncoated PDMS or coatings of polymerized poly(ethylene glycol dimethacrylate) (pPEGDMA) or poly(hydroxyethyl methacrylate) (pHEMA). Further, capsule thickness is reduced over a wide range of pCBMA cross-linker compositions. On cochlear implant electrode arrays implanted subcutaneously for one year, the coating bridges over the exposed platinum electrodes and dramatically reduces the capsule thickness over the entire implant. Coated cochlear implant electrode arrays could therefore lead to persistent improved performance and reduced risk of residual hearing loss. More generally, the in vivo anti-fibrotic properties of pCBMA coatings also demonstrate potential to mitigate the fibrotic response on a variety of sensing/stimulating implants. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/518125v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1d92121org.highwire.dtl.DTLVardef@e2ca3org.highwire.dtl.DTLVardef@948783org.highwire.dtl.DTLVardef@14ce647_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

Durability of photografted zwitterionic hydrogel coatings for reduction of the foreign body response to cochlear implants

ObjectiveDurability of photografted zwitterionic hydrogel coatings on cochlear implant biomaterials was examined to determine viability of these antifouling surfaces during insertion and long-term implant usage. Approach: Tribometry was used to determine the effect of zwitterionic coatings on lubricity of surfaces with varying hydration level, applied normal force, and timeframe. Additionally, flexural resistance was investigated using mandrel bending. Ex vivo durability was assessed by determining coefficient of friction between tissues and treated surfaces. Furthermore, cochlear implantation force was measured using cadaveric human cochleae. Main results: Hydrated zwitterionic hydrogel coatings reduced frictional resistance approximately 20-fold compared to uncoated PDMS, which importantly led to significantly lower mean force experienced by coated cochlear implants during insertion compared to uncoated systems. Under flexural force, zwitterionic films resisted failure for up to 60 minutes of desiccation. The large increase in lubricity was maintained for 20 hours under continual force while hydrated. For loosely crosslinked systems, films remained stable and lubricious even after rehydration following complete drying. All films remained hydrated and functional under frictional force for at least 30 minutes in ambient conditions while drying, with lower crosslink densities showing the greatest longevity. Moreover, photografted zwitterionic hydrogel samples showed no evidence of degradation and nearly identical lubricity before and after implantation. Significance: This work demonstrates that photografted zwitterionic hydrogel coatings are sufficiently durable to maintain viability before, during, and after implantation. Mechanical properties, including greatly increased lubricity, are preserved after complete drying and rehydration for various applied forces. Additionally, this significantly enhanced lubricity translates to significantly decreased force during insertion of implants which should result in less trauma and scarring.

bioengineering↗

bioRxiv2022

Cochlear implant material effects on inflammatory cell function and foreign body response

ObjectivesThe objectives of this study were to assess the effects of cochlear implant (CI) biomaterials on the function of macrophages and fibroblasts, two key mediators of the foreign body response (FBR) and to determine how these materials influence fibrous tissue growth and new bone formation within the cochlea. MethodsMacrophages and fibroblasts were cultured on polydimethylsiloxane (PDMS) and platinum substrates and human CI electrodes in vitro. Cell count, cell proliferation, cytokine production, and cell adhesion were measured. CI electrodes were implanted into murine cochleae for one week without electrical stimulation. Implanted cochleae were harvested for 3D X-ray microscopy with the CI left in-situ. The location of new bone growth within the scala tympani (ST) with reference to different portions of the implant (PDMS vs platinum) was quantified. ResultsCell counts of macrophages and fibroblasts were significantly higher on platinum substrates and platinum contacts of CI electrodes. Fibroblast proliferation was greater on platinum relative to PDMS, and cells grown on platinum formed more/larger focal adhesions. 3D x-ray microscopy showed neo-ossification in the peri-implant areas of the ST. Volumetric quantification of neo-ossification showed a trend toward greater bone formation adjacent to the platinum electrodes compared to areas opposite or away from the platinum electrode bearing surfaces. ConclusionsFibrotic reactions are biomaterial specific, as demonstrated by the differences in cell adhesion, proliferation, and fibrosis on platinum and PDMS. The inflammatory reaction to platinum contacts on CI electrodes likely contributes to fibrosis to a greater degree than PDMS, and platinum contacts may influence the deposition of new bone, as demonstrated in the in vivo data. This information can potentially be used to influence the design of future generations of neural prostheses.

bioengineering↗

bioRxiv2021

Chronic Cochlear Implantation with and without Electric Stimulation in a Mouse Model Induces Robust Cochlear Influx of CX3CR1+/GFP Macrophages.

BackgroundCochlear implantation is an effective auditory rehabilitation strategy for those with profound hearing loss, including those with residual low frequency hearing through use of hybrid cochlear implantation techniques. Post-mortem studies demonstrate the nearly ubiquitous presence of intracochlear fibrosis and neo-ossification following cochlear implantation. Current evidence suggests post-implantation intracochlear fibrosis is associated with delayed loss of residual acoustic hearing in hybrid cochlear implant (CI) recipients and may also negatively influence outcomes in traditional CI recipients. This study examined the contributions of surgical trauma, foreign body response and electric stimulation to intracochlear fibrosis and the innate immune response to cochlear implantation and the hierarchy of these contributions. MethodsNormal hearing CX3CR1+/GFP mice underwent either round window opening (sham), acute CI insertion or chronic CI insertion with no, low- or high-level electric stimulation. Electric stimulation levels were based on neural response telemetry (NRT), beginning post-operative day 7 for 4 hours per day. Subjects (n=3 per timepoint) were sacrificed at 4 hours, 1,4,7,8,11,14 and 21 days. An unimplanted group (n=3) served as controls. Cochleae were harvested at each time-point and prepared for immunohistochemistry with confocal imaging. The images were analyzed to obtain CX3CR1+ macrophage cell number and density in the lateral wall (LW), scala tympani (ST) and Rosenthals canal (RC). ResultsA ST peri-implant cellular infiltrate and fibrosis occurred exclusively in the chronically implanted groups starting on day 7 with a concurrent infiltration of CX3CR1+ macrophages not seen in the other groups. CX3CR1+ macrophage infiltration was seen in the LW and RC in all experimental groups within the first week, being most prominent in the 3 chronically implanted groups during the second and third week. There were no significant differences in macrophage infiltration related to levels of electric stimulation. ConclusionsThe cochlear immune response was most prominent in the presence of chronic cochlear implantation, regardless of electric stimulation level. Further, the development of intracochlear ST fibrosis was dependent on the presence of the indwelling CI foreign body. An innate immune response was evoked by surgical trauma alone (sham and acute CI groups) to a lesser degree. These data suggest that cochlear inflammation and intrascalar fibrosis after cochlear implantation are largely dependent on the presence of a chronic indwelling foreign body and are not critically dependent on electrical stimulation. Also, these data support a role for surgical trauma in inciting the initial innate immune response.

neuroscience↗

bioRxiv2021

Interaction of micropatterned topographical and biochemical cues to direct neurite growth from spiral ganglion neurons

Functional outcomes with neural prosthetic devices, such as cochlear implants, are limited in part due to physical separation between the stimulating elements and the neurons they stimulate. One strategy to close this gap aims to precisely guide neurite regeneration to position the neurites in closer proximity to electrode arrays. Here, we explore the ability of micropatterned biochemical and topographic guidance cues, singly and in combination, to direct the growth of spiral ganglion neuron (SGN) neurites, the neurons targeted by cochlear implants. Photopolymerization of methacrylate monomers was used to form unidirectional topographical features of ridges and grooves in addition to multidirectional patterns with 90{degrees} angle turns. Microcontact printing was also used to create similar uni- and multi-directional patterns of peptides on polymer surfaces. Biochemical cues included peptides that facilitate (laminin, LN) or repel (EphA4-Fc) neurite growth. On flat surfaces, SGN neurites preferentially grew on LN-coated stripes and avoided EphA4-Fc-coated stripes. LN or EphA4-Fc was selectively adsorbed onto the ridges or grooves to test the neurite response to a combination of topographical and biochemical cues. Coating the ridges with EphA4-Fc and grooves with LN lead to enhanced SGN alignment to topographical patterns. Conversely, EphA4-Fc coating on the grooves or LN coating on the ridges tended to disrupt alignment to topographical patterns. SGN neurites respond to combinations of topographical and biochemical cues and surface patterning that leverages both cues enhance guided neurite growth.

bioengineering↗

bioRxiv2020

Manipulation of a cation-{Pi} sandwich expands knowledge of the conformational flexibility of mammalian phenylalanine hydroxylase

Phenylalanine hydroxylase (PAH) is an allosteric enzyme responsible for maintaining phenylalanine (Phe) below neurotoxic levels; its failure results in phenylketonuria. Wild type (WT) PAH equilibrates among resting-state (RS-PAH) and activated (A-PAH) conformations, whose equilibrium position depends upon allosteric Phe binding to the A-PAH conformation. The RS-PAH conformation of WT rat PAH (rPAH) contains a cation-{pi} sandwich between Phe80, Arg123, and Arg420, which cannot exist in the A-PAH conformation. Phe80 variants F80A, F80D, F80L, and F80R were prepared; their conformational equilibrium was evaluated using native PAGE, size exclusion chromatography, ion exchange behavior, intrinsic protein fluorescence, enzyme kinetics, and limited proteolysis, each as a function of [Phe]. Like WT rPAH, F80A and F80D show allosteric activation by Phe while F80L and F80R are constitutively active. Maximal activity of all variants suggests relief of a rate-determining conformational change involving Phe80. Limited proteolysis of WT rPAH in the absence of Phe reveals facile cleavage within a C-terminal 4-helix bundle that is buried in the RS-PAH tetramer interface, reflecting dynamic dissociation of the RS-PAH conformation. This cleavage is not seen for the Phe80 variants, which all show proteolytic hypersensitivity in a linker that repositions during the RS-PAH to A-PAH conformational interchange. Hypersensitivity is corrected by addition of Phe such that all Phe80 variants become like WT rPAH and achieve the A-PAH conformation. Thus, manipulation of Phe80 perturbs the conformational space sampled by PAH, increasing the propensity to sample intermediates in the RS-PAH and A-PAH interchange, which are presumed on-pathway because they can readily achieve the A-PAH conformation by addition of Phe.

biochemistry↗