Neuromodulation Strategies to Reduce Inflammation and Improve Lung Complications in COVID-19 Patients.

Since the outbreak of the COVID-19 pandemic, races across academia and industry have been initiated to identify and develop disease modifying or preventative therapeutic strategies has been initiated. The primary focus has been on pharmacological treatment of the immune and respiratory system and the development of a vaccine. The hyperinflammatory state ("cytokine storm") observed in many cases of COVID-19 indicates a prognostically negative disease progression that may lead to respiratory distress, multiple organ failure, shock, and death. Many critically ill patients continue to be at risk for significant, long-lasting morbidity or mortality. The human immune and respiratory systems are heavily regulated by the central nervous system, and intervention in the signaling of these neural pathways may permit targeted therapeutic control of excessive inflammation and pulmonary bronchoconstriction. Several technologies, both invasive and non-invasive, are available and approved for clinical use, but have not been extensively studied in treatment of the cytokine storm in COVID-19 patients. This manuscript provides an overview of the role of the nervous system in inflammation and respiration, the current understanding of neuromodulatory techniques from preclinical and clinical studies and provides a rationale for testing non-invasive neuromodulation to modulate acute systemic inflammation and respiratory dysfunction caused by SARS-CoV-2 and potentially other pathogens. The authors of this manuscript have co-founded the International Consortium on Neuromodulation for COVID-19 to advocate for and support studies of these technologies in the current coronavirus pandemic.

Efficacy profile of noninvasive vagus nerve stimulation on cortical spreading depression susceptibility and the tissue response in a rat model.

BACKGROUND: Noninvasive vagus nerve stimulation (nVNS) has recently emerged as a promising therapy for migraine. We previously demonstrated that vagus nerve stimulation inhibits cortical spreading depression (CSD), the electrophysiological event underlying migraine aura and triggering headache; however, the optimal nVNS paradigm has not been defined. METHODS: Various intensities and doses of nVNS were tested to improve efficacy on KCl-evoked CSD frequency and electrical threshold of CSD in a validated rat model. Chronic efficacy was evaluated by daily nVNS delivery for four weeks. We also examined the effects of nVNS on neuroinflammation and trigeminovascular activation by western blot and immunohistochemistry. RESULTS: nVNS suppressed susceptibility to CSD in an intensity-dependent manner. Two 2-minute nVNS 5 min apart afforded the highest efficacy on electrical CSD threshold and frequency of KCl-evoked CSD. Daily nVNS for four weeks did not further enhance efficacy over a single nVNS 20 min prior to CSD. The optimal nVNS also attenuated CSD-induced upregulation of cortical cyclooxygenase-2, calcitonin gene-related peptide in trigeminal ganglia, and c-Fos expression in trigeminal nucleus caudalis. CONCLUSIONS: Our study provides insight on optimal nVNS parameters to suppress CSD and suggests its benefit on CSD-induced neuroinflammation and trigeminovascular activation in migraine treatment.

Traumatic Injury Under COVID-19 Stay-at-Home Advisory: Experience of a New England Trauma Center.

BACKGROUND: With the onset of the COVID-19 pandemic and subsequent widespread stay-at-home advisories throughout early 2020, hospitals have noticed a decrease in illnesses unrelated to COVID-19. However, the impact on traumatic injury is relatively unknown. This study aims to characterize patterns of trauma during the COVID-19 pandemic at a Level I Trauma Center. MATERIALS & METHODS: A retrospective review was performed of adult trauma patients from March to June, in the years 2018 through 2020. Primary outcome was the number of trauma activations (volume). Secondary outcomes included activation level, mechanism of injury, mortality rate, and length of stay, and other demographic background. Trauma patterns of the 2018 and 2019 periods were combined as historical control, and compared to patterns of the biweekly-matched period of 2020. RESULTS: A total of 2,187 patients were included in analysis (Pre-COVID n = 1,572; COVID n = 615). Results were significant for decreased trauma volume but longer length of stay during COVID cohort, and for an increased proportion of males. No significant difference was found for other demographic variables, trauma mechanisms, or severity. Trauma volume patterns mirrored COVID rates in the state. CONCLUSIONS: Despite a decline in trauma volume, other trauma patterns including severity and mechanism remained unchanged during the COVID-19 period. The decreased volume was not associated with a markedly lower clinical workload, change in team structure, or provider coverage re-distribution. Our data suggests that trauma volume and severity remained high enough during COVID-19 peak to necessitate full staffing, which may provide guidance in the event of a pandemic resurgence.

Vagus nerve stimulation reduces spreading depolarization burden and cortical infarct volume in a rat model of stroke.

Cortical spreading depolarization (SD) waves negatively affect neuronal survival and outcome after ischemic stroke. We here aimed to investigate the effects of vagus nerve stimulation (VNS) on SDs in a rat model of focal ischemia. To this end, we delivered non-invasive VNS (nVNS) or invasive VNS (iVNS) during permanent middle cerebral artery occlusion (MCAO), and found that both interventions significantly reduced the frequency of SDs in the cortical peri-infarct area compared to sham VNS, without affecting relative blood flow changes, blood pressure, heart rate or breathing rate. In separate groups of rats subjected to transient MCAO, we found that cortical stroke volume was reduced 72 h after transient MCAO, whereas stroke volume in the basal ganglia remained unchanged. In rats treated with nVNS, motor outcome was improved 2 days after transient MCAO, but was similar to sham VNS animals 3 days after ischemia. We postulate that VNS may be a safe and efficient intervention to reduce the clinical burden of SD waves in stroke and other conditions.

Exploration of the Impact of Brief Noninvasive Vagal Nerve Stimulation on EEG and Event-Related Potentials.

OBJECTIVES: The primary objective of this study was to explore the impact of noninvasive Vagal Nerve Stimulation (nVNS) on brain electrophysiology, as assessed through spontaneous resting-state EEG and stimulus-driven event-related potentials (ERPs). METHODS: A hand-held transcutaneous stimulator was placed on the neck over the main branch of the left vagus (active condition) or more laterally over neck muscles (sham condition), with two 120-sec long bursts of stimulation applied over a five-minute period. For each of eight neurotypical subjects, prior to stimulation, and then again beginning at 15, 120, and 240 min post-stimulation, ten minutes of background EEG data were collected, along with a series of ERPs-N100 auditory sensory-gating; the N1/P2 loudness dependent auditory evoked responses (LDAER); mismatch negativity; P300a; and P300b. Each subject participated in active and sham stimulation sessions. RESULTS: Brief nVNS had a significant (p < 0.05), and in some cases prolonged (>2 hours), impact on the spontaneous EEG (decreased theta and alpha, and increased beta and gamma), and on sensory gating, LDAER, and P300b evoked responses. Based on prior literature, these specific observations may reflect nVNS-induced modulation of particular neurotransmitter systems including those for GABA (gamma power and frequency); acetylcholine (sensory gating); serotonin (LDAER); and noradrenaline (P300b). CONCLUSIONS: Brief nVNS leads to changes in a sub-set of resting-state and event-related electrophysiologic indices of brain activity. These changes are believed to be mediated by vagal afferent projections to the nucleus of the solitary tract, which in turn regulates several neurotransmitter systems through known direct and indirect neuroanatomic pathways.

High-Resolution Multi-Scale Computational Model for Non-Invasive Cervical Vagus Nerve Stimulation.

OBJECTIVES: To develop the first high-resolution, multi-scale model of cervical non-invasive vagus nerve stimulation (nVNS) and to predict vagus fiber type activation, given clinically relevant rheobase thresholds. METHODS: An MRI-derived Finite Element Method (FEM) model was developed to accurately simulate key macroscopic (e.g., skin, soft tissue, muscle) and mesoscopic (cervical enlargement, vertebral arch and foramen, cerebral spinal fluid [CSF], nerve sheath) tissue components to predict extracellular potential, electric field (E-Field), and activating function along the vagus nerve. Microscopic scale biophysical models of axons were developed to compare axons of varying size (Aα-, Aß- and Aδ-, B-, and C-fibers). Rheobase threshold estimates were based on a step function waveform. RESULTS: Macro-scale accuracy was found to determine E-Field magnitudes around the vagus nerve, while meso-scale precision determined E-field changes (activating function). Mesoscopic anatomical details that capture vagus nerve passage through a changing tissue environment (e.g., bone to soft tissue) profoundly enhanced predicted axon sensitivity while encapsulation in homogenous tissue (e.g., nerve sheath) dulled axon sensitivity to nVNS. CONCLUSIONS: These findings indicate that realistic and precise modeling at both macroscopic and mesoscopic scales are needed for quantitative predictions of vagus nerve activation. Based on this approach, we predict conventional cervical nVNS protocols can activate A- and B- but not C-fibers. Our state-of-the-art implementation across scales is equally valuable for models of spinal cord stimulation, cortex/deep brain stimulation, and other peripheral/cranial nerve models.

Microglia modulation through external vagus nerve stimulation in a murine model of Alzheimer's disease.

Chronically activated microglia contribute to the development of neurodegenerative diseases such as Alzheimer's disease (AD) by the release of pro-inflammatory mediators that compromise neuronal function and structure. Modulating microglia functions could be instrumental to interfere with disease pathogenesis. Previous studies have shown anti-inflammatory effects of acetylcholine (ACh) or norepinephrine (NE), which mainly activates the ß-receptors on microglial cells. Non-invasive vagus nerve stimulation (nVNS) is used in treatment of drug-resistant depression, which is a risk factor for developing AD. The vagus nerve projects to the brainstem's locus coeruleus from which noradrenergic fibers reach to the Nucleus Basalis of Meynert (NBM) and widely throughout the brain. Pilot studies showed first signs of cognitive-enhancing effects of nVNS in AD patients. In this study, the effects of nVNS on mouse microglia cell morphology were analyzed over a period of 280 min by 2-photon laser scanning in vivo microscopy. Total branch length, average branch order and number of branches, which are commonly used indicators for the microglial activation state were determined and compared between young and old wild-type and amyloid precursor protein/presenilin-1 (APP/PS1) transgenic mice. Overall, these experiments show strong morphological changes in microglia, from a neurodestructive to a neuroprotective phenotype, following a brief nVNS in aged animals, especially in APP/PS1 animals, whereas microglia from young animals were morphologically unaffected.

Cervical non-invasive vagus nerve stimulation (nVNS) for preventive and acute treatment of episodic and chronic migraine and migraine-associated sleep disturbance: a prospective observational cohort study.

BACKGROUND: The debilitating nature of migraine and challenges associated with treatment-refractory migraine have a profound impact on patients. With the need for alternatives to pharmacologic agents, vagus nerve stimulation has demonstrated efficacy in treatment-refractory primary headache disorders. We investigated the use of cervical non-invasive vagus nerve stimulation (nVNS) for the acute treatment and prevention of migraine attacks in treatment-refractory episodic and chronic migraine (EM and CM) and evaluated the impact of nVNS on migraine-associated sleep disturbance, disability, and depressive symptoms. METHODS: Twenty patients with treatment-refractory migraine were enrolled in this 3-month, open-label, prospective observational study. Patients administered nVNS prophylactically twice daily at prespecified times and acutely as adjunctive therapy for migraine attacks. Pain intensity (visual analogue scale [VAS]); number of headache days per month and number of migraine attacks per month; number of acutely treated attacks and time to achieve pain relief; sleep quality (Pittsburgh Sleep Quality Index [PSQI]); migraine disability assessment (MIDAS); depressive symptoms (Beck Depression Inventory(®) [BDI]); and adverse events (AEs) were evaluated. RESULTS: Of the 20 enrolled patients, 10 patients each had been diagnosed with EM and CM. Prophylaxis with nVNS was associated with significant overall reductions in patient-perceived pain intensity (mean VAS scores at baseline vs 3 months: 7.75 ± 0.64 vs 4.05 ± 0.76; 95 % CI: 3.3, 4.1; p < 0.0001), mean number of headache days per month (baseline vs 3 months: 14.7 ± 4.1 vs 8.9 ± 3.66; 95 % CI: 3.3, 8.3; p < 0.0001), and mean number of migraine attacks per month (baseline vs 3 months: 7.3 ± 3.85 vs 4.45 ± 2.48; 95 % CI: 0.8, 4.9; p < 0.01). For acutely treated migraine attacks, a reduction in mean time (minutes) to achieve pain relief (baseline vs 3 months: 84.5 ± 39.1 vs 52.75 ± 16.42; 95 % CI: 12.6, 51.0; p < 0.002) was noted. Significant improvements, more evident in patients with EM, were noted in MIDAS and BDI scores along with a trend toward improvement in PSQI daytime dysfunction subscore (p = 0.07). No severe or serious AEs occurred. CONCLUSION: In this study, treatment with nVNS was safe and provided clinically meaningful decreases in the frequency, intensity, and duration of migraine attacks in patients with treatment-refractory migraine. Improvements in migraine-associated disability, depression, and sleep quality were also noted.

Noninvasive vagus nerve stimulation as treatment for trigeminal allodynia.

Implanted vagus nerve stimulation (VNS) has been used to treat seizures and depression. In this study, we explored the mechanism of action of noninvasive vagus nerve stimulation (nVNS) for the treatment of trigeminal allodynia. Rats were repeatedly infused with inflammatory mediators directly onto the dura, which led to chronic trigeminal allodynia. Administration of nVNS for 2 minutes decreased periorbital sensitivity in rats with periorbital trigeminal allodynia for up to 3.5 hours after stimulation. Using microdialysis, we quantified levels of extracellular neurotransmitters in the trigeminal nucleus caudalis (TNC). Allodynic rats showed a 7.7±0.9-fold increase in extracellular glutamate in the TNC after i.p. administration of the chemical headache trigger glyceryl trinitrate (GTN; 0.1 mg/kg). Allodynic rats that received nVNS had only a 2.3±0.4-fold increase in extracellular glutamate after GTN, similar to the response in control naive rats. When nVNS was delayed until 120 minutes after GTN treatment, the high levels of glutamate in the TNC were reversed after nVNS. The nVNS stimulation parameters used in this study did not produce significant changes in blood pressure or heart rate. These data suggest that nVNS may be used to treat trigeminal allodynia.

Low voltage vagal nerve stimulation reduces bronchoconstriction in guinea pigs through catecholamine release.

OBJECTIVE: Electrical stimulation of the vagus nerve at relatively high voltages (e.g., >10 V) can induce bronchoconstriction. However, low voltage (≤2 V) vagus nerve stimulation (VNS) can attenuate histamine-invoked bronchoconstriction. Here, we identify the mechanism for this inhibition. METHODS: In urethanea-nesthetized guinea pigs, bipolar electrodes were attached to both vagus nerves and changes in pulmonary inflation pressure were recorded in response to i.v. histamine and during VNS. The attenuation of the histamine response by low-voltage VNS was then examined in the presence of pharmacologic inhibitors or nerve ligation. RESULTS: Low-voltage VNS attenuated histamine-induced bronchoconstriction (4.4 ± 0.3 vs. 3.2 ± 0.2 cm H(2) O, p < 0.01) and remained effective following administration of a nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester, and after sympathetic nerve depletion with guanethidine, but not after the ß-adrenoceptor antagonist propranolol. Nerve ligation caudal to the electrodes did not block the inhibition but cephalic nerve ligation did. Low-voltage VNS increased circulating epinephrine and norepinephrine without but not with cephalic nerve ligation. CONCLUSION: These results indicate that low-voltage VNS attenuates histamine-induced bronchoconstriction via activation of afferent nerves, resulting in a systemic increase in catecholamines likely arising from the adrenal medulla.

Practice management guidelines for the diagnosis and management of injury in the pregnant patient: the EAST Practice Management Guidelines Work Group.

Trauma during pregnancy has presented very unique challenges over the centuries. From the first report of Ambrose Pare of a gunshot wound to the uterus in the 1600s to the present, there have existed controversies and inconsistencies in diagnosis, management, prognostics, and outcome. Anxiety is heightened by the addition of another, smaller patient. Trauma affects 7% of all pregnancies and requires admission in 4 of 1000 pregnancies. The incidence increases with advancing gestational age. Just over half of trauma during pregnancy occurs in the third trimester. Motor vehicle crashes comprise 50% of these traumas, and falls and assaults account for 22% each. These data were considered to be underestimates because many injured pregnant patients are not seen at trauma centers. Trauma during pregnancy is the leading cause of nonobstetric death and has an overall 6% to 7% maternal mortality. Fetal mortality has been quoted as high as 61% in major trauma and 80% if maternal shock is present. The anatomy and physiology of pregnancy make diagnosis and treatment difficult.

Osteoblasts stimulated with pulsed electromagnetic fields increase HUVEC proliferation via a VEGF-A independent mechanism.

The clinically beneficial effect of low frequency pulsed electromagnetic fields (ELF-PEMF) on bone healing has been described, but the exact mechanism of action remains unclear. A recent study suggests that there is a direct autocrine mitogenic effect of ELF-PEMF on angiogenesis. The hypothesis of this study is that ELF-PEMF also has an indirect effect on angiogenesis by manipulation of vascular endothelial growth factor (VEGF)-A-based paracrine intercellular communication with neighboring osteoblasts. Conditioned media experiments measured fetal rat calvarial cell (FRC) and human umbilical vein endothelial cell (HUVEC) proliferation using tritiated thymidine uptake. We demonstrate that ELF-PEMF (15 Hz, 1.8 mT, for 8 h) has an indirect effect on the proliferation rate of both endothelial cells and osteoblasts in vitro by altering paracrine mediators. Conditioned media from osteoblast cells stimulated with ELF-PEMF increased endothelial proliferation 54-fold, whereas media from endothelial cells stimulated with ELF-PEMF did not affect osteoblast proliferation. We examined the role of the pro-angiogenic mediator VEGF-A in the mitogenic effect of ELF-PEMF-stimulated osteoblast media on endothelial cells. The production of VEGF-A by FRC as measured by ELISA was not changed by exposure to PEMF, and blocking experiments demonstrated that the ELF-PEMF-induced osteoblast-derived endothelial mitogen observed in these studies was not VEGF-A, but some other soluble angiogenic mediator.

Osteoprotegerin (OPG) production by cells in the osteoblast lineage is regulated by pulsed electromagnetic fields in cultures grown on calcium phosphate substrates.

Pulsed electromagnetic fields (PEMF) used clinically to stimulate bone formation enhance the osteogenic effects of BMP-2 on human mesenchymal stem cells (MSCs) if the MSCs are grown in osteogenic medium and are cultured on calcium phosphate (CaP) surfaces rather than tissue culture polystyrene plastic (TCPS). This study tested if PEMF's effects on cells in the osteoblast lineage are substrate dependent and if factors produced by osteoblasts that regulate osteoclastic bone resorption, might also be regulated by PEMF. Human MSCs treated with BMP-2 and human osteoblast-like cells (normal human osteoblasts [NHOst cells], MG63 cells, SaOS-2 cells) were cultured on CaP or TCPS and their response to PEMF (4.5 ms bursts of 20 pulses repeating at 15 Hz for 8 h/day) determined as a function of decoy receptor osteoprotegerin (OPG) and RANK ligand (RANKL) production, both of which are associated with regulation of osteoclast differentiation. The results showed that when osteoblast-like cells were cultured on CaP, PEMF decreased cell number and increased production of paracrine factors associated with reduced bone resorption like OPG. RANKL was unaffected, indicating that the OPG/RANKL ratio was increased, further supporting a surface-dependent osteogenic effect of PEMF. Moreover, effects of estrogen were surface dependent and enhanced by PEMF, demonstrating that PEMF can modulate osteogenic responses to anabolic regulators of osteoblast function. These effects of PEMF would not be evident in models examining cells in traditional culture on plastic.

Comparison of a caprolactone/lactide film (mesofol) to two polylactide film products as a barrier to postoperative peridural adhesion in an ovine dorsal laminectomy model.

STUDY DESIGN: Experimental study. OBJECTIVE: To evaluate and compare the performances of 2 bioresorbable products, Mesofol (a caprolactone/lactide film) and Lactosorb (a polylactide film), as barriers to postoperative peridural adhesions and fibrosis. SUMMARY OF BACKGROUND DATA: Postoperative peridural adhesions from scar tissue may be an inciting cause of chronic pain and dysfunction in "failed back" syndrome. Many biocompatible products and drugs, as well as autografts have been tested as antiadhesion barriers with varying success. METHODS: The bioresorbable film products were used to cover large laminectomy defects in 11 sheep. Three laminectomy defects were created, with 2 randomly assigned treatment sites and 1 control site in each animal. A tear was created in the dura allowing cerebrospinal fluid leakage to assess for impaired dural healing. Performance of the film barriers was assessed at 10 weeks postoperative by gross scar and tenacity scoring by 3 blinded, independent observers in 7 animals. Histology was performed in 4 animals. New Methylene blue dye myelography and magnetic resonance imaging were performed to assess for cerebrospinal fluid leakage. Magnetic resonance imaging was also used to evaluate the imaging characteristics of adhesions. RESULTS: All 3 products evaluated showed a benefit to prevention of postoperative peridural adhesion; the performance of Mesofol was deemed superior to either of the 2 Lactosorb products. The handling characteristics of all products were compatible with clinical usage. Impairment to healing of dural tears or active inflammation was not identified with any product. CONCLUSION: The results of this investigation support previous studies on the benefit of polylactide film barriers, like Lactosorb, for reducing peridural adhesion following spinal surgery. The performance of Mesofol in this investigation suggests that it may provide improved antiadhesion properties in comparison to the polylactide products. Safety issues related to impaired dural healing was not identified in either product.

Pulsed electromagnetic fields accelerate normal and diabetic wound healing by increasing endogenous FGF-2 release.

BACKGROUND: Chronic wounds, particularly in diabetics, result in significant morbidity and mortality and have a profound economic impact. The authors demonstrate that pulsed electromagnetic fields significantly improve both diabetic and normal wound healing in 66 mice through up-regulation of fibroblast growth factor (FGF)-2 and are able to prevent tissue necrosis in diabetic tissue after an ischemic insult. METHODS: Db/db and C57BL6 mice were wounded and exposed to pulsed electromagnetic fields. Gross closure, cell proliferation, and vascularity were assessed. Cultured medium from human umbilical vein endothelial cells exposed to pulsed electromagnetic fields was analyzed for FGF-2 and applied topically to wounds. Skin flaps were created on streptozocin-induced diabetic mice and exposed to pulsed electromagnetic fields. Percentage necrosis, oxygen tension, and vascularity were determined. RESULTS: Pulsed electromagnetic fields accelerated wound closure in diabetic and normal mice. Cell proliferation and CD31 density were significantly increased in pulsed electromagnetic field-treated groups. Cultured medium from human umbilical vein endothelial cells in pulsed electromagnetic fields exhibited a three-fold increase in FGF-2, which facilitated healing when applied to wounds. Skin on diabetic mice exposed to pulsed electromagnetic fields did not exhibit tissue necrosis and demonstrated oxygen tensions and vascularity comparable to those in normal animals. CONCLUSIONS: This study demonstrates that pulsed electromagnetic fields are able to accelerate wound healing under diabetic and normal conditions by up-regulation of FGF-2-mediated angiogenesis. They also prevented tissue necrosis in response to a standardized ischemic insult, suggesting that noninvasive angiogenic stimulation by pulsed electromagnetic fields may be useful to prevent ulcer formation, necrosis, and amputation in diabetic patients.

Electrical stimulation of the growth plate: a potential approach to an epiphysiodesis.

Epiphysiodesis is an operative procedure that induces bony bridges to form across a growth plate of a bone to stop longitudinal growth. This is a very common orthopedic procedure to correct disproportional long-bone growth discrepancies; however, present techniques require an operation and anesthesia. Our study was designed to develop a minimally invasive method of epiphysiodesis by using electrical stimulation with DC current. In a rabbit model, a thin titanium electrode was inserted into a single location of the distal femoral growth plate in three groups: one without current (control), one group with a constant 10 microA (low current, LC), and one group with a 50 microA (high current, HC). The current was delivered for 2 weeks. The nontreated femur served as a control for each animal. Femur lengths were measured and comparisons were made between operated (left) and nonoperated (right) femurs. Digitized histomorphometric and volumetric analyses were performed on each growth plate, and detailed assessments were made of any morphological changes. Using length measurements, the difference in femur length was significantly larger in the HC group and not in the LC or control groups, showing bone growth inhibition at the higher current. In the HC group, bony bridges and disorganized growth plates were observed. This study shows that delivery of an electrical current of 50 microA for as little as 2 weeks can markedly affect bone growth as evidenced by changes in epiphyseal plate volume and architectural organization, and the study supports the use of this minimally invasive approach as a potential method of achieving an epiphysiodesis.

Effects of direct current electrical stimulation on gene expression of osteopromotive factors in a posterolateral spinal fusion model.

STUDY DESIGN: An in vivo model was used to determine levels of mRNA expression in response to direct current (DC) electrical stimulation in a rabbit posterolateral fusion model. OBJECTIVES: This study tested the possibility that DC stimulation at the surgery site would increase expression of genes related to bone formation relative to expression in autograft alone. SUMMARY OF BACKGROUND DATA: DC electrical stimulation as an adjunct treatment in spinal surgery has shown increased fusion rates when compared with autograft alone, yet the biology of such treatment is not fully understood. METHODS: Thirty New Zealand White rabbits were entered into the study. A posterolateral, intertransverse process fusion was performed bilaterally at L4-L5, with autogenous bone graft. An implantable DC stimulator was placed across the decorticated transverse processes before placement of autograft. Animals were killed at 3, 7, 14, 21, and 28 days. mRNA levels of BMP-2, 4, 6, 7, VEGF, FGF-2, TGF-beta, ALK-2, and ALK-3 were evaluated with real-time RT-PCR. RESULTS: mRNA expression was significantly higher in the DC stimulated animals versus the control animals for several of the genes studied. In particular, levels of mRNA were elevated for BMP-2, BMP-6, and BMP-7. CONCLUSIONS: This study shows for the first time that DC stimulation results in a sustained increase of multiple osteogenic genes, suggesting that the biologic mechanism for the DC-induced increase in the rate and extent of bone formation observed clinically may be mediated by the up-regulation of these osteoinductive factors.

Real-time control of neutrophil metabolism by very weak ultra-low frequency pulsed magnetic fields.

In adherent and motile neutrophils NAD(P)H concentration, flavoprotein redox potential, and production of reactive oxygen species and nitric oxide, are all periodic and exhibit defined phase relationships to an underlying metabolic oscillation of approximately 20 s. Utilizing fluorescence microscopy, we have shown in real-time, on the single cell level, that the system is sensitive to externally applied periodically pulsed weak magnetic fields matched in frequency to the metabolic oscillation. Depending upon the phase relationship of the magnetic pulses to the metabolic oscillation, the magnetic pulses serve to either increase the amplitude of the NAD(P)H and flavoprotein oscillations, and the rate of production of reactive oxygen species and nitric oxide or, alternatively, collapse the metabolic oscillations and curtail production of reactive oxygen species and nitric oxide. Significantly, we demonstrate that the cells do not directly respond to the magnetic fields, but instead are sensitive to the electric fields which the pulsed magnetic fields induce. These weak electric fields likely tap into an endogenous signaling pathway involving calcium channels in the plasma membrane. We estimate that the threshold which induced electric fields must attain to influence cell metabolism is of the order of 10(-4) V/m.

Treatment of nonunions with electric and electromagnetic fields.

Electric and electromagnetic fields are, collectively, one form of biophysical technique which regulate extracellular matrix (ECM) synthesis and may be useful in clinically stimulating repair of fractures and nonunions. Preclinical studies have shown that electric and electromagnetic fields regulate proteoglycan (PG) and collagen synthesis in models of endochondral ossification, and increase bone formation in vivo and in vitro. A substantial number of clinical studies have been done that suggest acceleration of bone formation and healing, particularly osteotomies and spine fusions, by electric and electromagnetic fields. Many of these studies have used randomized, placebo controlled designs. In osteotomy trials, greater bone density, trabecular maturation, and radiographic healing were observed in actively treated, compared with placebo-treated patients. In spine fusions, average union rates of 80% to 90% were observed in actively treated patients across numerous studies compared with 65% to 75% in placebo-treated patients. Uncontrolled, longitudinal cohort studies of delayed and nonunions report mean union rates of approximately 75% to 85% in fractures previously refractory to healing. The few randomized controlled studies in delayed and nonunions suggest improved results with electric and electromagnetic fields compared with placebo treatment, and equivalent to bone grafts.