Daniel Hellenbrand - Academia.edu (original) (raw)

Papers by Daniel Hellenbrand

Research paper thumbnail of Anatomical Proximity Between Sciatic Nerve and Ischial Spine and its Relationship to the Development of Deep Gluteal Pain Syndrome

World neurosurgery, May 1, 2024

Research paper thumbnail of A Localized Materials‐Based Strategy to Non‐Virally Deliver Chondroitinase ABC mRNA Improves Hindlimb Function in a Rat Spinal Cord Injury Model

Advanced Healthcare Materials, Aug 25, 2022

Spinal cord injury often results in devastating consequences for those afflicted, with very few t... more Spinal cord injury often results in devastating consequences for those afflicted, with very few therapeutic options. A central element of spinal cord injuries is astrogliosis, which forms a glial scar that inhibits neuronal regeneration post‐injury. Chondroitinase ABC (ChABC) is an enzyme capable of degrading chondroitin sulfate proteoglycan (CSPG), the predominant extracellular matrix component of the glial scar. However, poor protein stability remains a challenge in its therapeutic use. Messenger RNA (mRNA) delivery is an emerging gene therapy technology for in vivo production of difficult‐to‐produce therapeutic proteins. Here, mineral‐coated microparticles as an efficient, non‐viral mRNA delivery vehicles to produce exogenous ChABC in situ within a spinal cord lesion are used. ChABC production reduces the deposition of CSPGs in an in vitro model of astrogliosis, and direct injection of these microparticles within a glial scar forces local overexpression of ChABC and improves recovery of motor function seven weeks post‐injury.

Research paper thumbnail of Glial cell line-derived neurotrophic factor as a treatment after spinal cord injury

Neural Regeneration Research, 2018

Research paper thumbnail of The secondary injury cascade after spinal cord injury: an analysis of local cytokine/chemokine regulation

Neural Regeneration Research

After spinal cord injury, there is an extensive infiltration of immune cells, which exacerbates t... more After spinal cord injury, there is an extensive infiltration of immune cells, which exacerbates the injury and leads to further neural degeneration. Therefore, a major aim of current research involves targeting the immune response as a treatment for spinal cord injury. Although much research has been performed analyzing the complex inflammatory process following spinal cord injury, there remain major discrepancies within previous literature regarding the timeline of local cytokine regulation. The objectives of this study were to establish an overview of the timeline of cytokine regulation for 2 weeks after spinal cord injury, identify sexual dimorphisms in terms of cytokine levels, and determine local cytokines that significantly change based on the severity of spinal cord injury. Rats were inflicted with either a mild contusion, moderate contusion, severe contusion, or complete transection, 7 mm of spinal cord centered on the injury was harvested at varying times post-injury, and t...

Research paper thumbnail of Brachial Plexus Anatomy of Miniature Swine Compared to Human

Research Square (Research Square), Aug 19, 2020

Research paper thumbnail of The Therapeutic Role of Interleukin-10 after Spinal Cord Injury

Journal of Neurotrauma, 2013

Research paper thumbnail of Basic techniques for long distance axon tracing in the spinal cord

Microscopy Research and Technique, 2013

The regeneration of axons after a spinal cord injury or disease is attracting a significant amoun... more The regeneration of axons after a spinal cord injury or disease is attracting a significant amount of interest among researchers. Being able to assess these axons in terms of morphology, length and origin is essential to our understanding of the regeneration process. Recently, two specific axon tracers have gained much recognition; biotinylated dextran amine (BDA) 10 kDa as an anterograde tracer and cholera toxin-B as a retrograde tracer. However, there are still several complexities when using these tracers, including the volume that should be administered and the best administration site so that a significant amount of axons are labeled in the area of interest. In this article, we describe some simple procedures for injecting the tracers and detecting them. We also quantified the number of axons at different locations of the spinal cord. Our results show axons labeled from motor cortex injections traveled down to the lumbosacral spinal cord in 2 weeks, while BDA injections into the lateral vestibular nucleus and reticular formation took 3 weeks to label axons in the lumbosacral spinal cord. Moreover, this protocol outlines some basic procedures that could be used in any laboratory and gives insight into the number of axons labeled and how procedures could be tailored to meet specific researcher's needs.

Research paper thumbnail of Glial cell line-derived neurotrophic factor as a treatment after spinal cord injury

Neural Regeneration Research, 2018

Spinal cord injury (SCI) is a devastating trauma that currently affects 54 people out of every mi... more Spinal cord injury (SCI) is a devastating trauma that currently affects 54 people out of every million, which is approximately 270,000 people in the United States (National Spinal Cord Injury Statistical Center, 2013). The effects of such an injury can cause a loss of both motor and sensory function below the injury site, normally leaving the patient unable to care for themselves entirely and relying on family and friends to provide personal care. Currently there are no definitive cures to a SCI; however, several potential treatments are currently being researched. One potential treatment would be the use of glial cell line-derived neurotrophic factor (GDNF), a growth factor that affects both neurons and astrocytes, which are support cells that protect neurons and maintain homeostasis. This has been shown to decrease lesion size, reduce allodynia, and regenerate axons in the central nervous system (CNS) and peripheral nervous system (PNS) (Rosich et al., 2017). GDNF has been extensively studied as a growth factor that has the potential to promote the survival of dopaminergic neurons. GDNF also has a potent survival effect on other neurons in the CNS and has many other roles in the nervous system (Paratcha and Ledda, 2008). GDNF has been characterized as a glycosylated homodimer connected by disulfide bond, and has two forms: a two hundred and eleven amino acid pre-GDNF inactive form and a one hundred and thirty-four amino acid active form. GDNF is the most potent growth factor of the GDNF family ligands (GFLs), which all contain seven conserved cysteine residues (Rosich et al., 2017).

Research paper thumbnail of The Role of Interleukins after Spinal Cord Injury

Interleukins - The Immune and Non-Immune Systems’ Related Cytokines, 2021

In skin wound healing the injured tissue goes through a normal progression, inflammation subsides... more In skin wound healing the injured tissue goes through a normal progression, inflammation subsides and remodeling occurs. However after spinal cord injury inflammation persists and there is less progression into a regenerative/rebuilding phase. This inflammatory process after spinal cord injury is orchestrated by many cell types and numerous cytokines. Although there are several positive effects of inflammation after spinal cord injury, such as the removal of debris, the substantial upregulation of immune cells has been shown to contribute to neural degeneration. Several chemokines and cytokines including many interleukins are involved in guiding these immune cells to the lesion. While there are many inflammatory cytokines acting on these immune cells after SCI, there are also several anti-inflammatory interleukins that have shown beneficial effects in reducing inflammation. After SCI in a rat model, interleukin-10 and interleukin-19 have been shown to downregulate the synthesis of p...

Research paper thumbnail of The Window Test: a simple bedside method to detect radial deviation of the wrist commonly seen in posterior interosseous nerve palsy

Research paper thumbnail of Functional recovery after peripheral nerve injury via sustained growth factor delivery from mineral-coated microparticles

Neural Regeneration Research, 2021

The gold standard for treating peripheral nerve injuries that have large nerve gaps where the ner... more The gold standard for treating peripheral nerve injuries that have large nerve gaps where the nerves cannot be directly sutured back together because it creates tension on the nerve, is to incorporate an autologous nerve graft. However, even with the incorporation of a nerve graft, generally patients only regain a small portion of function in limbs affected by the injury. Although, there has been some promising results using growth factors to induce more axon growth through the nerve graft, many of these previous therapies are limited in their ability to release growth factors in a sustained manner and tailor them to a desired time frame. The ideal drug delivery platform would deliver growth factors at therapeutic levels for enough time to grow axons the entire length of the nerve graft. We hypothesized that mineral coated microparticles (MCMs) would bind, stabilize and release biologically active glial cell-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) in a sustained manner. Therefore, the objective of this study was to test the ability of MCMs releasing growth factors at the distal end of a 10 mm sciatic nerve graft, to induce axon growth through the nerve graft and restore hind limb function. After sciatic nerve grafting in Lewis rats, the hind limb function was tested weekly by measuring the angle of the ankle at toe lift-off while walking down a track. Twelve weeks after grafting, the grafts were harvested and myelinated axons were analyzed proximal to the graft, in the center of the graft, and distal to the graft. Under physiological conditions in vitro, the MCMs delivered a burst release of NGF and GDNF for 3 days followed by a sustained release for at least 22 days. In vivo, MCMs releasing NGF and GDNF at the distal end of sciatic nerve grafts resulted in significantly more myelinated axons extending distal to the graft when compared to rats that received nerve grafts without growth factor treatment. The rats with nerve grafts incorporated with MCMs releasing NGF and GDNF also showed significant improvement in hind limb function starting at 7 weeks postoperatively and continuing through 12 weeks postoperatively when compared to rats that received nerve grafts without growth factor treatment. In conclusion, MCMs released biologically active NGF and GDNF in a sustained manner, which significantly enhanced axon growth resulting in a significant improvement of hind limb function in rats. The animal experiments were approved by University of Wisconsin-Madison Animal Care and Use Committee (ACUC, protocol# M5958) on January 3, 2018.

Research paper thumbnail of Differences in neuroplasticity after spinal cord injury in varying animal models and humans

Neural Regeneration Research

Rats have been the primary model to study the process and underlying mechanisms of recovery after... more Rats have been the primary model to study the process and underlying mechanisms of recovery after spinal cord injury. Two weeks after a severe spinal cord contusion, rats can regain weight-bearing abilities without therapeutic interventions, as assessed by the Basso, Beattie and Bresnahan locomotor scale. However, many human patients suffer from permanent loss of motor function following spinal cord injury. While rats are the most understood animal model, major differences in sensorimotor pathways between quadrupeds and bipeds need to be considered. Understanding the major differences between the sensorimotor pathways of rats, non-human primates, and humans is a start to improving targets for treatments of human spinal cord injury. This review will discuss the neuroplasticity of the brain and spinal cord after spinal cord injury in rats, non-human primates, and humans. A brief overview of emerging interventions to induce plasticity in humans with spinal cord injury will also be discussed.

Research paper thumbnail of Peripheral Nerve Grafts and Chondroitinase ABC Application Improves Functional Recovery After Complete Spinal Cord Transection

Elmer This is an open-access article distributed under the terms of the Creative Commons Attribut... more Elmer This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Research paper thumbnail of Inflammation after spinal cord injury: a review of the critical timeline of signaling cues and cellular infiltration

Journal of Neuroinflammation

Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss... more Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss of motor and sensory function. Although extensive research to develop treatments for SCI has been performed, to date, none of these treatments have produced a meaningful amount of functional recovery after injury. The primary injury is caused by the initial trauma to the spinal cord and results in ischemia, oxidative damage, edema, and glutamate excitotoxicity. This process initiates a secondary injury cascade, which starts just a few hours post-injury and may continue for more than 6 months, leading to additional cell death and spinal cord damage. Inflammation after SCI is complex and driven by a diverse set of cells and signaling molecules. In this review, we utilize an extensive literature survey to develop the timeline of local immune cell and cytokine behavior after SCI in rodent models. We discuss the precise functional roles of several key cytokines and their effects on a variety...

Research paper thumbnail of Sustained interleukin-10 delivery reduces inflammation and improves motor function after spinal cord injury

Journal of Neuroinflammation

Background: The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as... more Background: The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as a treatment method for spinal cord injury (SCI) due to its ability to attenuate pro-inflammatory cytokines and reduce apoptosis. Primary limitations when using systemic injections of IL-10 are that it is rapidly cleared from the injury site and that it does not cross the blood-spinal cord barrier. Objective: Here, mineral-coated microparticles (MCMs) were used to obtain a local sustained delivery of IL-10 directly into the injury site after SCI. Methods: Female Sprague-Dawley rats were contused at T10 and treated with either an intraperitoneal injection of IL-10, an intramedullary injection of IL-10, or MCMs bound with IL-10 (MCMs+IL-10). After treatment, cytokine levels were measured in the spinal cord, functional testing and electrophysiology were performed, axon tracers were injected into the brainstem and motor cortex, macrophage levels were counted using flow cytometry and immunohistochemistry, and lesion size was measured. Results: When treated with MCMs+IL-10, IL-10 was significantly elevated in the injury site and inflammatory cytokines were significantly suppressed, prompting significantly less cells expressing antigens characteristic of inflammatory macrophages and significantly more cells expressing antigens characteristic of earlier stage antiinflammatory macrophages. Significantly more axons were preserved within the rubrospinal and reticulospinal tracts through the injury site when treated with MCMs+IL-10; however, there was no significant difference in corticospinal tract axons preserved, regardless of treatment group. The rats treated with MCMs+IL-10 were the only group with a significantly higher functional score compared to injured controls 28 days post-contusion. Conclusion: These data demonstrate that MCMs can effectively deliver biologically active IL-10 for an extended period of time altering macrophage phenotype and aiding in functional recovery after SCI.

Research paper thumbnail of The Effects of Glial Cell Line-Derived Neurotrophic Factor After Spinal Cord Injury

Journal of neurotrauma, Jan 10, 2017

Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States... more Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States. The use of growth factors is a potential treatment for reducing secondary damage, promoting axon growth and restoring some of the lost function after SCI. Glial cell line-derived neurotrophic factor (GDNF) is an important growth factor, because it can affect both neurons and support cells. Here, we give an in depth review of the previously published literature where GDNF was used to treat SCI. The effects of GDNF have been shown to decrease lesion size, improve allodynia, and regenerate axons in the central nervous system and peripheral nervous system. GDNF is necessary for early development and lack of GDNF can lead to abnormal development of the autonomic nervous system or death. Exogenous administration of GDNF either prior to or immediately after SCI is most effective. Even though GDNF can be directly administered, genetically modified cells are often used as a delivery vehicle. Se...

Research paper thumbnail of Immunohistochemical assessment of rat nerve isografts and immunosuppressed allografts

Neurological Research, 2016

Autologous peripheral nerve grafts are commonly used clinically as a treatment for peripheral ner... more Autologous peripheral nerve grafts are commonly used clinically as a treatment for peripheral nerve injuries. However, in research using an autologous graft is not always feasible due to loss of function, which in many cases is assessed to determine the efficacy of the peripheral nerve graft. In addition, using allografts for research require the use of an immunosuppressant, which creates unwanted side effects and another variable within the experiment that can affect regeneration. The objective of this study was to analyze graft rejection in peripheral nerve grafts and the effects of cyclosporine A (CSA) on axonal regeneration. Peripheral nerve grafts in inbred Lewis rats were compared with Sprague-Dawley (SD) rats to assess graft rejection, CSA side effects, immune responses, and regenerative capability. Macrophages and CD8+ cells were labeled to determine graft rejection, and neurofilaments were labeled to determine axonal regeneration. SD rats without CSA had significantly more macrophages and CD8+ cells compared to Lewis autografts, Lewis isografts, and SD allografts treated with CSA. Lewis autografts, Lewis isografts, and SD autografts had significantly more regenerated axons than SD rat allografts. Moreover, allografts in immunosuppressed SD rats had significantly less axons than Lewis rat autograft and isografts. Autografts have long been the gold standard for treating major nerve injuries and these data suggest that even though CSA is effective at reducing graft rejection, axon regeneration is still superior in autografts versus immunosuppressed allografts.

Research paper thumbnail of Treating spinal cord injury via sustained drug delivery from calcium phosphate coatings

Neural Regeneration Research, 2016

Research paper thumbnail of Sustained release of neurotrophin-3 via calcium phosphate-coated sutures promotes axonal regeneration after spinal cord injury

Journal of neuroscience research, Jul 26, 2016

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly ... more Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin-3 (NT-3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT-3 binding and release were characterized in vitro. Then, the NT-3-loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP-coated sutures exhibited a burst release of NT-3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT-3-loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT-3-loaded suture were not significantly different from those of rats treated with...

Research paper thumbnail of Sustained release of neurotrophin-3 via calcium phosphate-coated sutures promotes axonal regeneration after spinal cord injury

Journal of Neuroscience Research, 2016

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly ... more Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin-3 (NT-3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT-3 binding and release were characterized in vitro. Then, the NT-3-loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP-coated sutures exhibited a burst release of NT-3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT-3-loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT-3-loaded suture were not significantly different from those of rats treated with PNGs alone. Cholera toxin subunit B (CTB) labeling rostral to the graft was not observed in any controls, but CTB labeling rostral to the graft was observed in almost all rats that had had a PNG. Neurofilament labeling on transverse sections of the graft revealed that the rats treated with the NT-3-loaded sutures had significantly more axons per graft than rats treated with an NT-3 injection and rats without NT-3. These data demonstrate that PNGs serve as scaffolds for axonal growth after SCI and that CaP-coated sutures can efficiently release NT-3 to increase axonal regeneration. © 2016 Wiley Periodicals, Inc.

Research paper thumbnail of Anatomical Proximity Between Sciatic Nerve and Ischial Spine and its Relationship to the Development of Deep Gluteal Pain Syndrome

World neurosurgery, May 1, 2024

Research paper thumbnail of A Localized Materials‐Based Strategy to Non‐Virally Deliver Chondroitinase ABC mRNA Improves Hindlimb Function in a Rat Spinal Cord Injury Model

Advanced Healthcare Materials, Aug 25, 2022

Spinal cord injury often results in devastating consequences for those afflicted, with very few t... more Spinal cord injury often results in devastating consequences for those afflicted, with very few therapeutic options. A central element of spinal cord injuries is astrogliosis, which forms a glial scar that inhibits neuronal regeneration post‐injury. Chondroitinase ABC (ChABC) is an enzyme capable of degrading chondroitin sulfate proteoglycan (CSPG), the predominant extracellular matrix component of the glial scar. However, poor protein stability remains a challenge in its therapeutic use. Messenger RNA (mRNA) delivery is an emerging gene therapy technology for in vivo production of difficult‐to‐produce therapeutic proteins. Here, mineral‐coated microparticles as an efficient, non‐viral mRNA delivery vehicles to produce exogenous ChABC in situ within a spinal cord lesion are used. ChABC production reduces the deposition of CSPGs in an in vitro model of astrogliosis, and direct injection of these microparticles within a glial scar forces local overexpression of ChABC and improves recovery of motor function seven weeks post‐injury.

Research paper thumbnail of Glial cell line-derived neurotrophic factor as a treatment after spinal cord injury

Neural Regeneration Research, 2018

Research paper thumbnail of The secondary injury cascade after spinal cord injury: an analysis of local cytokine/chemokine regulation

Neural Regeneration Research

After spinal cord injury, there is an extensive infiltration of immune cells, which exacerbates t... more After spinal cord injury, there is an extensive infiltration of immune cells, which exacerbates the injury and leads to further neural degeneration. Therefore, a major aim of current research involves targeting the immune response as a treatment for spinal cord injury. Although much research has been performed analyzing the complex inflammatory process following spinal cord injury, there remain major discrepancies within previous literature regarding the timeline of local cytokine regulation. The objectives of this study were to establish an overview of the timeline of cytokine regulation for 2 weeks after spinal cord injury, identify sexual dimorphisms in terms of cytokine levels, and determine local cytokines that significantly change based on the severity of spinal cord injury. Rats were inflicted with either a mild contusion, moderate contusion, severe contusion, or complete transection, 7 mm of spinal cord centered on the injury was harvested at varying times post-injury, and t...

Research paper thumbnail of Brachial Plexus Anatomy of Miniature Swine Compared to Human

Research Square (Research Square), Aug 19, 2020

Research paper thumbnail of The Therapeutic Role of Interleukin-10 after Spinal Cord Injury

Journal of Neurotrauma, 2013

Research paper thumbnail of Basic techniques for long distance axon tracing in the spinal cord

Microscopy Research and Technique, 2013

The regeneration of axons after a spinal cord injury or disease is attracting a significant amoun... more The regeneration of axons after a spinal cord injury or disease is attracting a significant amount of interest among researchers. Being able to assess these axons in terms of morphology, length and origin is essential to our understanding of the regeneration process. Recently, two specific axon tracers have gained much recognition; biotinylated dextran amine (BDA) 10 kDa as an anterograde tracer and cholera toxin-B as a retrograde tracer. However, there are still several complexities when using these tracers, including the volume that should be administered and the best administration site so that a significant amount of axons are labeled in the area of interest. In this article, we describe some simple procedures for injecting the tracers and detecting them. We also quantified the number of axons at different locations of the spinal cord. Our results show axons labeled from motor cortex injections traveled down to the lumbosacral spinal cord in 2 weeks, while BDA injections into the lateral vestibular nucleus and reticular formation took 3 weeks to label axons in the lumbosacral spinal cord. Moreover, this protocol outlines some basic procedures that could be used in any laboratory and gives insight into the number of axons labeled and how procedures could be tailored to meet specific researcher's needs.

Research paper thumbnail of Glial cell line-derived neurotrophic factor as a treatment after spinal cord injury

Neural Regeneration Research, 2018

Spinal cord injury (SCI) is a devastating trauma that currently affects 54 people out of every mi... more Spinal cord injury (SCI) is a devastating trauma that currently affects 54 people out of every million, which is approximately 270,000 people in the United States (National Spinal Cord Injury Statistical Center, 2013). The effects of such an injury can cause a loss of both motor and sensory function below the injury site, normally leaving the patient unable to care for themselves entirely and relying on family and friends to provide personal care. Currently there are no definitive cures to a SCI; however, several potential treatments are currently being researched. One potential treatment would be the use of glial cell line-derived neurotrophic factor (GDNF), a growth factor that affects both neurons and astrocytes, which are support cells that protect neurons and maintain homeostasis. This has been shown to decrease lesion size, reduce allodynia, and regenerate axons in the central nervous system (CNS) and peripheral nervous system (PNS) (Rosich et al., 2017). GDNF has been extensively studied as a growth factor that has the potential to promote the survival of dopaminergic neurons. GDNF also has a potent survival effect on other neurons in the CNS and has many other roles in the nervous system (Paratcha and Ledda, 2008). GDNF has been characterized as a glycosylated homodimer connected by disulfide bond, and has two forms: a two hundred and eleven amino acid pre-GDNF inactive form and a one hundred and thirty-four amino acid active form. GDNF is the most potent growth factor of the GDNF family ligands (GFLs), which all contain seven conserved cysteine residues (Rosich et al., 2017).

Research paper thumbnail of The Role of Interleukins after Spinal Cord Injury

Interleukins - The Immune and Non-Immune Systems’ Related Cytokines, 2021

In skin wound healing the injured tissue goes through a normal progression, inflammation subsides... more In skin wound healing the injured tissue goes through a normal progression, inflammation subsides and remodeling occurs. However after spinal cord injury inflammation persists and there is less progression into a regenerative/rebuilding phase. This inflammatory process after spinal cord injury is orchestrated by many cell types and numerous cytokines. Although there are several positive effects of inflammation after spinal cord injury, such as the removal of debris, the substantial upregulation of immune cells has been shown to contribute to neural degeneration. Several chemokines and cytokines including many interleukins are involved in guiding these immune cells to the lesion. While there are many inflammatory cytokines acting on these immune cells after SCI, there are also several anti-inflammatory interleukins that have shown beneficial effects in reducing inflammation. After SCI in a rat model, interleukin-10 and interleukin-19 have been shown to downregulate the synthesis of p...

Research paper thumbnail of The Window Test: a simple bedside method to detect radial deviation of the wrist commonly seen in posterior interosseous nerve palsy

Research paper thumbnail of Functional recovery after peripheral nerve injury via sustained growth factor delivery from mineral-coated microparticles

Neural Regeneration Research, 2021

The gold standard for treating peripheral nerve injuries that have large nerve gaps where the ner... more The gold standard for treating peripheral nerve injuries that have large nerve gaps where the nerves cannot be directly sutured back together because it creates tension on the nerve, is to incorporate an autologous nerve graft. However, even with the incorporation of a nerve graft, generally patients only regain a small portion of function in limbs affected by the injury. Although, there has been some promising results using growth factors to induce more axon growth through the nerve graft, many of these previous therapies are limited in their ability to release growth factors in a sustained manner and tailor them to a desired time frame. The ideal drug delivery platform would deliver growth factors at therapeutic levels for enough time to grow axons the entire length of the nerve graft. We hypothesized that mineral coated microparticles (MCMs) would bind, stabilize and release biologically active glial cell-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) in a sustained manner. Therefore, the objective of this study was to test the ability of MCMs releasing growth factors at the distal end of a 10 mm sciatic nerve graft, to induce axon growth through the nerve graft and restore hind limb function. After sciatic nerve grafting in Lewis rats, the hind limb function was tested weekly by measuring the angle of the ankle at toe lift-off while walking down a track. Twelve weeks after grafting, the grafts were harvested and myelinated axons were analyzed proximal to the graft, in the center of the graft, and distal to the graft. Under physiological conditions in vitro, the MCMs delivered a burst release of NGF and GDNF for 3 days followed by a sustained release for at least 22 days. In vivo, MCMs releasing NGF and GDNF at the distal end of sciatic nerve grafts resulted in significantly more myelinated axons extending distal to the graft when compared to rats that received nerve grafts without growth factor treatment. The rats with nerve grafts incorporated with MCMs releasing NGF and GDNF also showed significant improvement in hind limb function starting at 7 weeks postoperatively and continuing through 12 weeks postoperatively when compared to rats that received nerve grafts without growth factor treatment. In conclusion, MCMs released biologically active NGF and GDNF in a sustained manner, which significantly enhanced axon growth resulting in a significant improvement of hind limb function in rats. The animal experiments were approved by University of Wisconsin-Madison Animal Care and Use Committee (ACUC, protocol# M5958) on January 3, 2018.

Research paper thumbnail of Differences in neuroplasticity after spinal cord injury in varying animal models and humans

Neural Regeneration Research

Rats have been the primary model to study the process and underlying mechanisms of recovery after... more Rats have been the primary model to study the process and underlying mechanisms of recovery after spinal cord injury. Two weeks after a severe spinal cord contusion, rats can regain weight-bearing abilities without therapeutic interventions, as assessed by the Basso, Beattie and Bresnahan locomotor scale. However, many human patients suffer from permanent loss of motor function following spinal cord injury. While rats are the most understood animal model, major differences in sensorimotor pathways between quadrupeds and bipeds need to be considered. Understanding the major differences between the sensorimotor pathways of rats, non-human primates, and humans is a start to improving targets for treatments of human spinal cord injury. This review will discuss the neuroplasticity of the brain and spinal cord after spinal cord injury in rats, non-human primates, and humans. A brief overview of emerging interventions to induce plasticity in humans with spinal cord injury will also be discussed.

Research paper thumbnail of Peripheral Nerve Grafts and Chondroitinase ABC Application Improves Functional Recovery After Complete Spinal Cord Transection

Elmer This is an open-access article distributed under the terms of the Creative Commons Attribut... more Elmer This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Research paper thumbnail of Inflammation after spinal cord injury: a review of the critical timeline of signaling cues and cellular infiltration

Journal of Neuroinflammation

Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss... more Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss of motor and sensory function. Although extensive research to develop treatments for SCI has been performed, to date, none of these treatments have produced a meaningful amount of functional recovery after injury. The primary injury is caused by the initial trauma to the spinal cord and results in ischemia, oxidative damage, edema, and glutamate excitotoxicity. This process initiates a secondary injury cascade, which starts just a few hours post-injury and may continue for more than 6 months, leading to additional cell death and spinal cord damage. Inflammation after SCI is complex and driven by a diverse set of cells and signaling molecules. In this review, we utilize an extensive literature survey to develop the timeline of local immune cell and cytokine behavior after SCI in rodent models. We discuss the precise functional roles of several key cytokines and their effects on a variety...

Research paper thumbnail of Sustained interleukin-10 delivery reduces inflammation and improves motor function after spinal cord injury

Journal of Neuroinflammation

Background: The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as... more Background: The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as a treatment method for spinal cord injury (SCI) due to its ability to attenuate pro-inflammatory cytokines and reduce apoptosis. Primary limitations when using systemic injections of IL-10 are that it is rapidly cleared from the injury site and that it does not cross the blood-spinal cord barrier. Objective: Here, mineral-coated microparticles (MCMs) were used to obtain a local sustained delivery of IL-10 directly into the injury site after SCI. Methods: Female Sprague-Dawley rats were contused at T10 and treated with either an intraperitoneal injection of IL-10, an intramedullary injection of IL-10, or MCMs bound with IL-10 (MCMs+IL-10). After treatment, cytokine levels were measured in the spinal cord, functional testing and electrophysiology were performed, axon tracers were injected into the brainstem and motor cortex, macrophage levels were counted using flow cytometry and immunohistochemistry, and lesion size was measured. Results: When treated with MCMs+IL-10, IL-10 was significantly elevated in the injury site and inflammatory cytokines were significantly suppressed, prompting significantly less cells expressing antigens characteristic of inflammatory macrophages and significantly more cells expressing antigens characteristic of earlier stage antiinflammatory macrophages. Significantly more axons were preserved within the rubrospinal and reticulospinal tracts through the injury site when treated with MCMs+IL-10; however, there was no significant difference in corticospinal tract axons preserved, regardless of treatment group. The rats treated with MCMs+IL-10 were the only group with a significantly higher functional score compared to injured controls 28 days post-contusion. Conclusion: These data demonstrate that MCMs can effectively deliver biologically active IL-10 for an extended period of time altering macrophage phenotype and aiding in functional recovery after SCI.

Research paper thumbnail of The Effects of Glial Cell Line-Derived Neurotrophic Factor After Spinal Cord Injury

Journal of neurotrauma, Jan 10, 2017

Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States... more Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States. The use of growth factors is a potential treatment for reducing secondary damage, promoting axon growth and restoring some of the lost function after SCI. Glial cell line-derived neurotrophic factor (GDNF) is an important growth factor, because it can affect both neurons and support cells. Here, we give an in depth review of the previously published literature where GDNF was used to treat SCI. The effects of GDNF have been shown to decrease lesion size, improve allodynia, and regenerate axons in the central nervous system and peripheral nervous system. GDNF is necessary for early development and lack of GDNF can lead to abnormal development of the autonomic nervous system or death. Exogenous administration of GDNF either prior to or immediately after SCI is most effective. Even though GDNF can be directly administered, genetically modified cells are often used as a delivery vehicle. Se...

Research paper thumbnail of Immunohistochemical assessment of rat nerve isografts and immunosuppressed allografts

Neurological Research, 2016

Autologous peripheral nerve grafts are commonly used clinically as a treatment for peripheral ner... more Autologous peripheral nerve grafts are commonly used clinically as a treatment for peripheral nerve injuries. However, in research using an autologous graft is not always feasible due to loss of function, which in many cases is assessed to determine the efficacy of the peripheral nerve graft. In addition, using allografts for research require the use of an immunosuppressant, which creates unwanted side effects and another variable within the experiment that can affect regeneration. The objective of this study was to analyze graft rejection in peripheral nerve grafts and the effects of cyclosporine A (CSA) on axonal regeneration. Peripheral nerve grafts in inbred Lewis rats were compared with Sprague-Dawley (SD) rats to assess graft rejection, CSA side effects, immune responses, and regenerative capability. Macrophages and CD8+ cells were labeled to determine graft rejection, and neurofilaments were labeled to determine axonal regeneration. SD rats without CSA had significantly more macrophages and CD8+ cells compared to Lewis autografts, Lewis isografts, and SD allografts treated with CSA. Lewis autografts, Lewis isografts, and SD autografts had significantly more regenerated axons than SD rat allografts. Moreover, allografts in immunosuppressed SD rats had significantly less axons than Lewis rat autograft and isografts. Autografts have long been the gold standard for treating major nerve injuries and these data suggest that even though CSA is effective at reducing graft rejection, axon regeneration is still superior in autografts versus immunosuppressed allografts.

Research paper thumbnail of Treating spinal cord injury via sustained drug delivery from calcium phosphate coatings

Neural Regeneration Research, 2016

Research paper thumbnail of Sustained release of neurotrophin-3 via calcium phosphate-coated sutures promotes axonal regeneration after spinal cord injury

Journal of neuroscience research, Jul 26, 2016

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly ... more Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin-3 (NT-3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT-3 binding and release were characterized in vitro. Then, the NT-3-loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP-coated sutures exhibited a burst release of NT-3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT-3-loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT-3-loaded suture were not significantly different from those of rats treated with...

Research paper thumbnail of Sustained release of neurotrophin-3 via calcium phosphate-coated sutures promotes axonal regeneration after spinal cord injury

Journal of Neuroscience Research, 2016

Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly ... more Because of the dynamics of spinal cord injury (SCI), the optimal treatment will almost certainly be a combination approach to control the environment and promote axonal growth. This study uses peripheral nerve grafts (PNGs) as scaffolds for axonal growth while delivering neurotrophin-3 (NT-3) via calcium phosphate (CaP) coatings on surgical sutures. CaP coating was grown on sutures, and NT-3 binding and release were characterized in vitro. Then, the NT-3-loaded sutures were tested in a complete SCI model. Rats were analyzed for functional improvement and axonal growth into the grafts. The CaP-coated sutures exhibited a burst release of NT-3, followed by a sustained release for at least 20 days. Functionally, the rats with PNGs + NT-3-loaded sutures and the rats treated with PNGs scored significantly higher than controls on day 56 postoperatively. However, functional scores in rats treated with PNGs + NT-3-loaded suture were not significantly different from those of rats treated with PNGs alone. Cholera toxin subunit B (CTB) labeling rostral to the graft was not observed in any controls, but CTB labeling rostral to the graft was observed in almost all rats that had had a PNG. Neurofilament labeling on transverse sections of the graft revealed that the rats treated with the NT-3-loaded sutures had significantly more axons per graft than rats treated with an NT-3 injection and rats without NT-3. These data demonstrate that PNGs serve as scaffolds for axonal growth after SCI and that CaP-coated sutures can efficiently release NT-3 to increase axonal regeneration. © 2016 Wiley Periodicals, Inc.