Biology subjects

Burrell, J. C.

Publications and source records attributed to Burrell, J. C..

8 recordsLinked to original sources

bioRxiv2026

Long-Term Functional and Histological Outcomes Following Sutureless Peripheral Nerve Repair Using Nerve Tape in Pigs

Severe peripheral nerve injuries result in incomplete recovery despite neurorrhaphy. Microsurgical suturing is technically demanding, time-intensive, and may produce variable fascicular alignment. Nerve Tape is an FDA-approved sutureless device enabling rapid, reproducible nerve coaptation. This study compared Nerve Tape with epineurial microsuturing following common peroneal nerve transection in Yucatan minipigs. Over 12 months, both groups demonstrated reinnervation of the tibialis anterior and extensor digitorum brevis, representing proximal and distal muscle targets, respectively. Tibialis anterior recovery was comparable between groups. In contrast, Nerve Tape produced greater distal motor recovery in the extensor digitorum brevis, with approximately 1.8-fold higher compound muscle action potential amplitude and 74.3% versus 46.0% recovery compared with microsutures. Compound nerve action potential amplitudes recorded from the motor branch of the deep peroneal nerve were also greater with Nerve Tape, whereas conduction velocities were comparable. Histological analysis demonstrated preserved fascicular architecture distal to the repair in both groups, with no significant differences in axon count, mean myelinated axon diameter, or g-ratio in the terminal common peroneal nerve or its distal motor branch. Clinical use was demonstrated in a representative case with progressive recovery. Nerve Tape supported durable structural and functional recovery and improved distal motor reinnervation compared with microsuturing.

neuroscience↗

bioRxiv2026

Boldine inhibits SARM1 NADase Activity and Preserves Axonal Integrity After Nerve Injury

Wallerian degeneration of anucleated axonal segments is driven by SARM1, which depletes axonal NAD+, disrupting energy metabolism and triggering self-destruction. SARM1 inhibition is an emerging therapeutic target for traumatic nerve injuries. Boldine, a natural aporphine alkaloid from Peumus boldus, modulates connexin hemichannels, oxidative stress, and inflammation. Building on our published work showing boldines neuroprotective effects in nerve injury models, we hypothesized that boldine also inhibits SARM1 directly. A fluorescence polarization assay revealed that boldine inhibits SARM1 NADase activity with an IC50 of approximately 7.5 uM. AI-assisted structural modeling (AlphaFold3-based Boltz-1 with GNINA docking) predicted two boldine binding sites on SARM1: the TIR catalytic site (Kd [~] 13.5 uM) and the ARM-TIR regulatory interface (Kd [~] 12 uM). In a sciatic nerve explant model, boldine preserved the integrity of anucleated axonal segments at 3 and 7 days post-transection relative to vehicle controls. These findings suggest boldine may act as a dual-site SARM1 inhibitor and support its development as a neuroprotective therapy after traumatic axonal injury.

neuroscience↗

bioRxiv2020

Tyrosine-Derived Polycarbonate Nerve Guidance Tubes Elicit Pro-Regenerative Extracellular Matrix Deposition When Used to Bridge Segmental Nerve Defects in Swine

Promising biomaterials should be tested in appropriate large animal models that recapitulate human inflammatory and regenerative responses. Previous studies have shown tyrosine-derived polycarbonates (TyrPC) are versatile biomaterials with a wide range of applications across multiple disciplines. The library of TyrPC has been well studied and consists of thousands of polymer compositions with tunable mechanical characteristics and degradation and resorption rates that are useful for nerve guidance tubes (NGTs). NGTs made of different TyrPCs have been used in segmental nerve defect models in small animals. The current study is an extension of this work and evaluates NGTs made using two different TyrPC compositions in a 1 cm porcine peripheral nerve repair model. We first evaluated a nondegradable TyrPC formulation, demonstrating proof-of-concept chronic regenerative efficacy up to 6 months with similar nerve/muscle electrophysiology and morphometry to the autograft repair control. Next, we characterized the acute regenerative response using a degradable TyrPC formulation. After 2 weeks in vivo, TyrPC NGT promoted greater deposition of pro-regenerative extracellular matrix (ECM) constituents (in particular collagen I, collagen III, collagen IV, laminin and fibronectin) compared to commercially available collagen-based NGTs. This corresponded with dense Schwann cell infiltration and axon extension across the lumen. These findings confirmed results reported previously in a mouse model and reveal that TyrPC NGTs were well tolerated in swine and facilitated host axon regeneration and Schwann cell infiltration in the acute phase across segmental defects - likely by eliciting a favorable neurotrophic ECM milieu. This regenerative response ultimately can contribute to functional recovery.

bioengineering↗

bioRxiv2019

Peripheral Nerve Repair Using Tissue Engineered Living Scaffolds Comprised of Stretch-Grown Aligned Axonal Tracts Promotes Survival of Spinal Cord Motor Neurons

Peripheral nerve injury (PNI) impacts millions annually, often leaving debilitated patients with minimal repair options to improve functional recovery. Our group has previously developed tissue engineered nerve grafts (TENGs) featuring long, aligned axonal tracts from dorsal root ganglia (DRG) neurons that are fabricated in custom bioreactors using the process of axon "stretch-growth". We have shown that TENGs effectively serve as "living scaffolds" to promote regeneration across segmental nerve defects by exploiting the newfound mechanism of axon-facilitated axon regeneration, or "AFAR", by simultaneously providing haptic and neurotrophic support. To extend this work, the current study investigated the efficacy of living versus non-living regenerative scaffolds in preserving host sensory and motor neuronal health following nerve repair. Rats were assigned across five groups: naive, or repair using autograft, nerve guidance tube (NGT) with collagen, NGT + non-aligned DRG populations in collagen, or TENGs. We found that TENG repairs yielded equivalent regenerative capacity as autograft repairs based on preserved health of host spinal cord motor neurons and acute axonal regeneration, whereas NGT repairs or DRG neurons within an NGT exhibited reduced motor neuron preservation and diminished regenerative capacity. These acute regenerative benefits ultimately resulted in enhanced levels of functional recovery in animals receiving TENGs, at levels matching those attained by autografts. Our findings indicate that TENGs may preserve host spinal cord motor neuron health and regenerative capacity without sacrificing an otherwise uninjured nerve (as in the case of the autograft), and therefore represent a promising alternative strategy for neurosurgical repair following PNI. HIGHLIGHTSO_LITENGs preserve host spinal cord motor neuron health and regenerative capacity acutely following repair of segmental nerve defects, matching that of the clinical gold-standard autograft and exceeding commercially-available nerve guidance tubes. C_LIO_LITENGs facilitated regeneration across segmental nerve defects, yielding similar degree of chronically surviving host spinal motor neurons and functional recovery as compared to autografts. C_LIO_LIEarly surgical intervention for segmental nerve defect with living scaffolds, such as TENGs and autografts, preserves the host regenerative capacity, and likely increases the ceiling for total regeneration and functional recovery at chronic time points compared to (acellular) commercially-available nerve guidance tubes. C_LIO_LITENGs preserve host neuronal health and regenerative capacity without sacrificing an otherwise uninjured nerve, and therefore represent a promising alternative strategy to autografts or nerve guidance tube repairs. C_LI

bioengineering↗

bioRxiv2019

Tissue Engineered Axon Tracts Serve as Living Scaffolds to Accelerate Axonal Regeneration and Functional Recovery Following Peripheral Nerve Injury in Rats

Although regeneration of damaged axons in peripheral nerves has long been observed, the mechanisms facilitating this growth are not well characterized. Recently, we demonstrated that host axon regeneration could be greatly enhanced by transplanting engineered living axon tracts to guide outgrowth. Here, we used a model of rat sciatic nerve transection to explore potential mechanisms of this facilitated regeneration and its efficacy in comparison with nerve guidance tubes (NGTs) and autografts. Tissue engineered nerve grafts (TENGs) were developed via \"stretch-growth\" in mechanobioreactors and consisted of centimeter-scale aligned axonal tracts. Either TENGs, NGTs or autografts (reversed nerve) were then transplanted to bridge a 1 cm segmental gap in the sciatic nerve with the mechanisms of axonal regrowth assessed at 2 weeks and the extent of functional recovery assessed at 16 weeks. We observed numerous host axons growing directly along and intertwining with pre-formed axonal tracts in TENGs. This behavior appears to mimic the action of \"pioneer\" axons in developmental pathfinding by providing living cues for directed and accelerated outgrowth. Indeed, we found that the rates of axon regeneration were 3-4 fold faster than NGTs and equivalent to autografts. It was also observed that infiltration of host Schwann cells - traditional drivers of peripheral axon regeneration - was both accelerated and progressed directly along TENG axonal tracts. These TENG repairs resulted in levels of functional recovery equivalent to autografts, with each being several fold superior to NGT repairs. This new mechanism - which we term \"axon-facilitated axon-regeneration\" - may be further exploited to enhance axonal regeneration and functional recovery following neurotrauma.

bioengineering↗

bioRxiv2019

A Porcine Model of Peripheral Nerve Injury Enabling Ultra-Long Regenerative Distances: Surgical Approach, Recovery Kinetics, and Clinical Relevance

Approximately 20 million Americans currently experience residual deficits from traumatic peripheral nerve injury. Despite recent advancements in surgical technique, peripheral nerve repair typically results in poor functional outcomes due to prolonged periods of denervation resulting from long regenerative distances coupled with relatively slow rates of axonal regeneration. Development of novel surgical solutions requires valid preclinical models that adequately replicate the key challenges of clinical peripheral nerve injury. Our team has developed a porcine model using Yucatan minipigs that provides an opportunity to investigate peripheral nerve regeneration using different nerves tailored for a specific mechanism of interest, such as (1) nerve modality: motor, sensory, and mixed-modality; (2) injury length: short versus long gap; and (3) total regenerative distance: proximal versus distal injury. Here, we describe a comprehensive porcine model of two challenging clinically relevant procedures for repair of long segmental lesions ([≥] 5 cm) - the deep peroneal nerve repaired using a sural nerve autograft and the common peroneal nerve repaired using a saphenous nerve autograft - each featuring ultra-long total regenerative distances (up to 20 cm and 27 cm, respectively) to reach distal targets. This paper includes a detailed characterization of the relevant anatomy, surgical approach/technique, functional/electrophysiological outcomes, and nerve morphometry for baseline and autograft repaired nerves. These porcine models of major peripheral nerve injury are suitable as preclinical, translatable models for evaluating the efficacy, safety, and tolerability of next-generation artificial nerve grafts prior to clinical deployment.

neuroscience↗

bioRxiv2018

Cardiac myocyte microtissue aggregates broadcast local field potentials

Muscle tissue has been exploited as a living biopotential amplifier to facilitate transduction of peripheral nerve signals into prosthetic control in patients with limb amputation. Here we sought to address the question of whether microscopically small volumes of muscle tissue could effectively broadcast field potentials to electrodes not immediately in contact with that tissue. Cardiac myocytes were grown as three-dimensional aggregates containing 105 cells comprising a volume of approximately 0.065 mm3 (~500 m in diameter) atop multi-electrode arrays. In addition to the expected spontaneous contraction potentials detected using electrodes in direct contact with the myocytes, potentials could also be detected on distant electrodes not contacting the aggregates. Specifically, while both dissociated and aggregated cardiac myocyte cultures generated spontaneous contractions that could easily be recorded from underlying multi-electrode arrays, only aggregated myocyte cultures generated signals detectable several millimeters away by the electrode grid floating in media. This confirmed the ability of micro-volumes of aggregated muscle tissue to broadcast readily detectible signals. The amplitude of the potentials generated by the aggregates decreased exponentially with distance. The aggregates were sensitive to pharmacologic modification with isoproterenol increasing contraction rate. Simultaneous recordings with electrodes in physical contact to the aggregate and with electrodes several millimeters away revealed that the aggregates function as amplifiers and low-pass filters. This study lays the groundwork for forging myocyte aggregates as \"living amplifiers\" for long-term neural recording in brain-computer interfaces to treat neurological disease and injury.

bioengineering↗

bioRxiv2018

Optically-Controlled \"Living Electrodes\" with Long-Projecting Axon Tracts for a Synaptic Brain-Machine Interface

Achievements in intracortical neural interfaces are compromised by limitations in specificity and long-term performance. A biological intermediary between devices and the brain may offer improved specificity and longevity through natural synaptic integration with deep neural circuitry, while being accessible on the brain surface for optical read-out/control. Accordingly, we have developed the first "living electrodes" comprised of implantable axonal tracts protected within soft hydrogel cylinders for the biologically-mediated monitoring/modulation of brain activity. Here we demonstrate the controlled fabrication, rapid axonal outgrowth, reproducible cytoarchitecture, and simultaneous optical stimulation and recording of neuronal activity within these engineered constructs in vitro. We also present their transplantation, survival, integration, and optical recording in rat cortex in vivo as a proof-of-concept for this neural interface paradigm. The creation and functional validation of these preformed, axon-based "living electrodes" is a critical step towards developing a new class of biohybrid neural interfaces to probe and modulate native circuitry.

bioengineering↗