Biology subjects

Knudsen, B.

Publications and source records attributed to Knudsen, B..

10 recordsLinked to original sources

bioRxiv2026

Identification of low threshold off-target activation pathways during stimulation of carotid baroreceptor afferents in swine.

ObjectiveElectrical stimulation of the baroreceptors pathways at the carotid sinus bulb - known as baroreflex activation therapy (BAT) - is intended to change autonomic tone and ultimately reduce blood pressure and heart rate. BAT is pre-market approved by the United States Food and Drug Administration (FDA) for the treatment of heart failure and received an FDA humanitarian device exemption for drug resistant hypertension. However, responder rates are limited by side-effects including numbness in the head and neck, altered speech, respiratory constriction, dry cough, vomiting, and altered sensory and motor function of the tongue. We hypothesized that these side-effects are driven by activation of other nearby nerve fibers of similar or lower threshold than the carotid sinus nerve. In this study, we sought to identify the neural sources responsible for off-target muscle activation contributing to these side-effects. These sources would inform strategies mitigating off-target activation in BAT therapy. MethodsDomestic swine were used in this work as the diameter and thickness of the swine carotid artery are closer to human than those of canine models. A monopolar disk electrode mimicking the clinical CVRx(R) Neo electrode was surgically placed proximal to the carotid bifurcation with the position optimized for stimulation dose responsive changes in blood pressure. Evoked responses were recorded during dose response testing from multiple neck muscles, and the corresponding off-target nerve pathways were identified by sequential transection of nearby nerves. ResultsThe following activated off-target muscle groups and their corresponding nerve pathways were verified which included 1) the cricoarytenoid via recurrent laryngeal nerve, 2) cricothyroid via superior laryngeal nerve, 3) sternocleidomastoid via accessory nerve, and 4) the tongue via hypoglossal nerve. The constrictor muscle group was also activated through a more complex neural pathway. ConclusionWe identified multiple sources of therapy-limiting side-effects of BAT in the swine model. These results will help guide the design of improved stimulation electrodes, surgical placement, and parameter programming to reduce BAT-associated side-effects while increasing on-target activation in patients.

bioengineering↗

bioRxiv2025

Intrinsic higher potency of basal urothelial cells to intermediate and umbrella cells as the cell of origin for bladder cancer

Transcriptome profiling of bladder cancer has revealed distinct basal-like and luminal-like molecular subtypes, which may be correlated with pathological subtypes of different patient outcomes. However, whether these molecular subtypes originate from the corresponding cell types in the normal urothelium and whether different cells of origin influence bladder cancer progression remain unclear. Here, we conducted cell-type-specific lineage tracing in CRISPR/Cas9-induced mouse bladder cancer models of Pten and Trp53 targeting. We show that although basal, intermediate, and superficial umbrella cells can all serve as the cell of origin for bladder cancer, transformed umbrella cells were gradually displaced by tumor cells from inner layers, particularly transformed basal cells, which had highest stemness. Histological and single cell RNA-sequencing data comparing basal- and intermediate-cell-induced bladder tumors revealed that basal-induced tumors displayed higher heterogeneity, and contained unique cell clusters including Krt14+Ki67+ highly proliferative basal cells, squamous cell carcinoma, and transitioning cells towards the Gata3+ luminal subtype. Trajectory analysis confirmed the cell lineage differentiation hierarchy uncovered in lineage tracing. Moreover, human bladder cancer molecular subtype signatures were highly enriched in mouse tumor cell clusters of the corresponding cell of origin, and a gene signature derived from the unique basal-induced clusters is predictive of worse patient outcome. Overall, our results support that the basal and luminal molecular subtypes of bladder cancer have the corresponding cells of origin as their basis, and that urothelial basal cells are intrinsically more competitive than intermediate and umbrella cells in generating aggressive bladder cancer subtypes.

cancer biology↗

bioRxiv2025

Prevalence of sympathetic fibers within the rat cervical vagus, and functional consequence on physiological effects mediated by vagus nerve stimulation (VNS).

IntroductionElectrical stimulation of the vagus nerve (VNS) is an FDA approved therapy for epilepsy, depression and rehabilitation after stroke, with recent clinical trials to treat heart failure and inflammation. VNS is often assumed to activate either parasympathetic efferents projecting to visceral organs, and/or sensory afferents projecting from these organs, for its therapeutic effects. Recent studies in humans, swine and dogs have shown that sympathetic nerve fibers from the sympathetic trunk (ST) can frequently be found within the cervical vagus nerve (VN). However, the prevalence and functional consequence of sympathetic fibers on VNS have yet to be elucidated in the most common high throughput animal model to study disease, the rodent. MethodsWe carefully traced ST from sympathetic cervical ganglion (SCG) to find its location in the carotid sheath with reference to the VN in a cohort of Long Evans rats. We then assessed the prevalence of ST fibers with the cervical VN across the cohort using microCT and immunohistochemistry. Finally, we stimulated the VN and the ST in isolation, and where they were conjoined, to evaluate the ST contribution to changes in heart rate. VNS induced heart rate changes are a commonly used surrogate for changes in sympathetic/parasympathetic tone. ResultsThe ST frequently runs in very close proximity to the VN in rats when traced caudally from the SCG. The ST is even conjoined with the VN for stretches within the carotid sheathe at the most common location to place an epineural cuff. Cross-connecting branches were found between the ST and the VN. VNS performed at locations where there was minimal ST crossover induced dose-dependent bradycardia (decrease in heart rate) across the cohort, with detectable bradycardia across the cohort beginning at 50 A (n=8 right, n=3 left). Conversely, stimulation of the isolated ST induced tachycardia (increase in heart rate) across the cohort beginning at [~]200 A (n=7 right, n=3 left). ConclusionThese data suggest that studies of VNS in the rodent model may also be stimulating sympathetic fibers from the ST in addition to canonical VN pathways. Concurrent sympathetic activation has profound implications for dissecting mechanisms of VNS for a host of diseases/disorders. As such, careful post-mortem assessment of the presence of hitchhiking sympathetic fibers within the VN is critical for understanding sources of variability in VNS outcomes.

neuroscience↗

bioRxiv2024

Tenascin-C in the early lung cancer tumor microenvironment promotes progression through integrin activation and FAK

Pre-cancerous lung lesions are commonly initiated by activating mutations in the RAS pathway, but do not transition to lung adenocarcinomas (LUAD) without additional oncogenic signals. Here, we show that expression of the extracellular matrix protein Tenascin-C (TNC) is increased in and promotes the earliest stages of LUAD development in oncogenic KRAS-driven lung cancer mouse models and in human LUAD. TNC is initially expressed by fibroblasts and its expression extends to tumor cells as the tumor becomes invasive. Genetic deletion of TNC in the mouse models reduces early tumor burden and high-grade pathology and diminishes tumor cell proliferation, invasion, and focal adhesion kinase (FAK) activity. TNC stimulates cultured LUAD tumor cell proliferation and migration through engagement of v-containing integrins and subsequent FAK activation. Intringuingly, lung injury causes sustained TNC accumulation in mouse lungs, suggesting injury can induce additional TNC signaling for early tumor cell transition to invasive LUAD. Biospecimens from patients with stage I/II LUAD show TNC in regions of FAK activation and an association of TNC with tumor recurrence after primary tumor resection. These results suggest that exogenous insults that elevate TNC in the lung parenchyma interact with tumor-initiating mutations to drive early LUAD progression and local recurrence.

cancer biology↗

bioRxiv2024

Epidural Spinal Cord Recordings (ESRs): Sources of Artifact in Stimulation Evoked Compound Action Potentials

IntroductionEvoked compound action potentials (ECAPs) measured using epidural spinal recordings (ESRs) during epidural spinal cord stimulation (SCS) can help elucidate fundamental mechanisms for the treatment of pain, as well as inform closed-loop control of SCS. Previous studies have used ECAPs to characterize the neural response to various neuromodulation therapies and have demonstrated that ECAPs are highly prone to multiple sources of artifact, including post-stimulus pulse capacitive artifact, electromyography (EMG) bleed-through, and motion artifact resulting from disturbance of the electrode/tissue interface during normal behavior. However, a thorough characterization has yet to be performed for how these sources of artifact may contaminate recordings within the temporal window commonly used to determine activation of A-beta fibers in a large animal model. MethodsWe characterized the sources of artifacts that can contaminate the recording of ECAPs in an epidural SCS swine model using the Abbott Octrode lead. Muscle paralytics were administered to block muscle activation preventing EMG from contaminating the recorded ECAPs. Concurrent EMG recordings of the longissimus, a long muscle of the back, were used to confirm a 2-4 millisecond (ms) latency source of EMG bleed-through that frequently contaminated the A-beta temporal window. Additionally, we obtained recordings approximately 5-10 minutes post-mortem after clear evoked A-beta and associated EMG responses ceased to characterize the representation of stimulation artifact across the array. ResultsSpinal ECAP recordings can be contaminated by capacitive artifact, short latency EMG from nearby long muscles of the back, and motion artifact from multiple sources. In many cases, the capacitive artifact can appear nearly identical in duration and waveshape to evoked A-beta responses. These sources of EMG can have phase shifts across the electrode array, very similar to the phase shift anticipated by propagation of an evoked A-beta fiber response across the array. This short latency EMG is often evident at currents similar to those needed to activate A-beta fibers associated with the treatment of pain. Changes in cerebrospinal fluid between the cord and dura, and motion induced during breathing created a cyclic oscillation in all evoked components of the recorded ECAP signal. ConclusionCareful controls must be implemented to accurately separate neural signal from the sources of artifact in spinal cord ECAPs. To address this, we suggest experimental procedures and associated reporting requirements necessary to disambiguate the underlying neural response from these confounds. These data are important to better understand the conceptual framework for recorded ESRs, with components such as ECAPs, EMG responses and artifacts, and have important implications for closed-loop control algorithms to account for transient motion such as postural changes and cough.

neuroscience↗

bioRxiv2023

Characterization and Applications of Evoked Responses During Epidural Electrical Stimulation

Epidural electrical stimulation (EES) of the spinal cord has been FDA approved and used therapeutically for decades. However, there is still not a clear understanding of the local neural substrates and consequently the mechanism of action responsible for the therapeutic effects. Epidural spinal recordings (ESR) are collected from the electrodes placed in the epidural space. ESR contains multi-modality signal components such as the evoked neural response (due to tonic or BurstDR waveforms), evoked muscle response, stimulation artifact, and cardiac response. The tonic stimulation evoked compound action potential (ECAP) is one of the components in ESR and has been proposed recently to measure local neural activation during EES. Here, we first review and investigate the referencing strategies, as they apply to ECAP component in ESR in the domestic swine animal model. We then examine how ECAP component can be used to sense lead migration, an adverse outcome following lead placement that can reduce therapeutic efficacy. Lastly, we show and isolate concurrent activation of local back and leg muscles during EES, demonstrating that the ESR obtained from the recording contacts contain both ECAP and EMG components. These findings may further guide the implementation of recording and reference contacts in an implantable EES system and provide preliminary evidence for the utility of ECAP component in ESR to detect lead migration. We expect these results to facilitate future development of EES methodology and implementation of use of different components in ESR to improve EES therapy.

physiology↗

bioRxiv2022

Microneurography as a Minimally Invasive Method to Assess Target Engagement During Neuromodulation

ObjectivePeripheral neural signals recorded during neuromodulation therapies provide insights into local neural target engagement and serve as a sensitive biomarker of physiological effect. Although these applications make peripheral recordings important for furthering neuromodulation therapies, the invasive nature of conventional nerve cuffs and longitudinal intrafascicular electrodes (LIFEs) limit their clinical utility. Furthermore, cuff electrodes typically record clear asynchronous neural activity in small animal models but not in large animal models. Microneurography, a minimally invasive technique, is already used routinely in humans to record asynchronous neural activity in the periphery. However, the relative performance of microneurography microelectrodes compared to cuff and LIFE electrodes in measuring neural signals relevant to neuromodulation therapies is not well understood. ApproachTo address this gap, we recorded cervical vagus nerve (cVN) electrically evoked compound action potentials (ECAPs) and spontaneous activity in a human-scaled large animal model - the pig. Additionally, we recorded sensory evoked activity and both invasively and non-invasively evoked CAPs from the great auricular nerve (GAN). In aggregate, this study assesses the potential of microneurography electrodes to measure neural activity during neuromodulation therapies with statistically powered and pre-registered outcomes (https://osf.io/y9k6j). Main resultsThe cuff recorded the largest ECAP signal (p<0.01) and had the lowest noise floor amongst the evaluated electrodes. Despite the lower signal to noise ratio, microneurography electrodes were able to detect the threshold for neural activation with similar sensitivity to cuff and LIFE electrodes once a dose-response curve was constructed. Furthermore, the microneurography electrode was the only electrode to record distinct sensory evoked neural activity (p<0.01). SignificanceThe results show that microneurography electrodes can measure neural signals relevant to neuromodulation therapies. Microneurography could further neuromodulation therapies by providing a real-time biomarker to guide electrode placement and stimulation parameter selection to optimize local neural fiber engagement and study mechanisms of action.

bioengineering↗

bioRxiv2020

Oscillatory responses to generated and perceived rhythms

Neural oscillations have been proposed as a mechanism for structure building in language and music. In music, this idea is appealing because of the intuitive mapping between perceptual and neural rhythms. The strongest evidence has come from studies in which participants listened to isochronous sequences of identical tones and were asked to imagine hearing them in binary (march) or ternary meter (waltz). The critical finding was that in addition to increased signal at the frequency corresponding to the tone rate there was increased signal at the imagined meter frequencies. While it is striking that meter tracking was observed without any acoustic cues in the input, rhythm perception was confounded with rhythm imagery involving active generation of rhythmic structure. We conducted two electroencephalography experiments with musicians and non-musicians, teasing apart the effects of rhythm perception and rhythm generation. Evidence for meter-related neural oscillations was only observed in situations where rhythmic structure was actively generated, either via rhythm imagery or in the form of overt behavior (tapping). Thus, our data suggest that mere rhythm perception is not sufficient to elicit oscillations at the meter frequency and that they are instead driven by the active generation of rhythm. This undermines the proposal that neural oscillations constitute a basic structure building mechanism in rhythm perception and raises questions about the role of oscillations in language processing.

neuroscience↗

bioRxiv2020

Newly regenerated axons through a cell-containing biomaterial scaffold promote reorganization of spinal circuitry and restoration of motor functions with epidural electrical stimulation.

We report the effect of newly regenerated neural fibers via bioengineered scaffold on reorganization of spinal circuitry and restoration of motor functions with electrical epidural stimulation (EES) after spinal transection (ST). Restoration across multiple modalities was evaluated for 7 weeks after ST with implanted scaffold seeded with Schwann cells, producing neurotrophic factors and with rapamycin microspheres. Gradual improvement in EES-facilitated stepping was observed in animals with scaffolds, although, no significant difference in stepping ability was found between groups without EES. Similar number of regenerated axons through the scaffolds was found in rats with and without EES-enabled training. Re-transection through the scaffold at week 6, reduced EES-enabled motor function, remaining higher compared to rats without scaffolds. The combination of scaffolds and EES-enabled training demonstrated synaptic changes below the injury. These findings indicate that sub-functional connectivity with regenerated across injury fibers can reorganize of sub-lesional circuitry, facilitating motor functions recovery with EES.

neuroscience↗

bioRxiv2020

Segment-specific orientation of the dorsal and ventral roots for precise therapeutic targeting of human spinal cord

An understanding of spinal cord functional neuroanatomy is essential for diagnosis and treatment of multiple disorders including, chronic pain, movement disorders, and spinal cord injury. Till now, no information is available on segment-specific spinal roots orientation in humans. In this study we collected neuroanatomical measurements of the dorsal and ventral roots from C2-L5, as well as spinal cord and vertebral bone measurements from adult cadavers. Spatial orientation of dorsal and ventral roots were measured and correlated to the anatomical landmarks of the spinal cord and vertebral column. The results show less variability in rostral root angles compared to the caudal angles across all segments. Dorsal and ventral rootlets were oriented mostly perpendicular to the spinal cord at the cervical level and demonstrate more parallel orientation at the thoracic and lumbar segments. The number of rootlets was the highest in dorsal cervical and lumbar segments. Spinal cord transverse diameter and size of the dorsal columns were largest at cervical and lumbar segments. The strongest correlation was found between the length of intervertebral foramen to rostral rootlet and vertebral bone length. These results could be used to locate spinal roots and spinal cord landmarks based on bone marks on CT or X-rays. These results also provide background for future correlations between anatomy of spinal cord and spinal column structures that could improve stereotactic surgical procedures and electrode positioning for spinal cord neuromodulation. One Sentence SummaryThis is the first detailed analysis of the segment-specific dorsal and ventral spinal roots spatial orientation measured and correlated to the anatomical landmarks of the spinal cord and vertebral column for human.

neuroscience↗