The impact of SARS-CoV-2 measures on patient samples and complication rates in spine surgery – A single center analysis

ObjectiveOver the past two years during the pandemic, the German health system has taken drastic measures, like the continuous use of face masks for all staff, restrictions of hospital visits as well as cancellation of elective surgical procedures. As a potential side effect of these measures, a significant reduction of surgical site infections was reported for neurosurgical patients. The purpose of our study was to analyze the impact of these measures on spinal surgery.MethodsWe performed a retrospective analysis to compare patient samples, procedures and infection rates before (January 2019 – March 2020) and during (April 2020 – June 2021) the pandemic to evaluate the impact of the measures mentioned above. Demographic and clinical data were collected and correlated with the occurrence of postoperative complications, especially infection.ResultsOur analysis showed no relevant decrease of spine surgeries (838 surgeries in non-pandemic group vs. 831 surgeries pandemic group). The most common postoperative complication was wound infection in both groups, followed by urinary tract infection and pneumonia. In both patient groups, infections were more prevalent in surgeries of multilevel posterior instrumentation. Comparing the two groups of patients, a slight, non-significant (0.5%) reduction of overall postoperative complications in the pandemic group was observed. However, the number of spinal surgeries classified as emergencies in our institution increased by 10.2% during the last 15 months of the COVID-19 pandemic. In line with this finding the urgent transfer of patients from smaller hospitals increased by 14.2%, compared to previous years.ConclusionThe volume of spinal surgeries remained high and complication rates stable during the pandemic. A reason why complication rates did not drop as reported previously might be a significant change in patient sample due to the increase of emergency surgeries. A decrease of complication rates, especially infections by the measures of infection prevention for the pandemic was not observed

DNA Damage in Nijmegen Breakage Syndrome Cells Leads to PARP Hyperactivation and Increased Oxidative Stress

Nijmegen Breakage Syndrome (NBS), an autosomal recessive genetic instability syndrome, is caused by hypomorphic mutation of the NBN gene, which codes for the protein nibrin. Nibrin is an integral member of the MRE11/RAD50/NBN (MRN) complex essential for processing DNA double-strand breaks. Cardinal features of NBS are immunodeficiency and an extremely high incidence of hematological malignancies. Recent studies in conditional null mutant mice have indicated disturbances in redox homeostasis due to impaired DSB processing. Clearly this could contribute to DNA damage, chromosomal instability, and cancer occurrence. Here we show, in the complete absence of nibrin in null mutant mouse cells, high levels of reactive oxygen species several hours after exposure to a mutagen. We show further that NBS patient cells, which unlike mouse null mutant cells have a truncated nibrin protein, also have high levels of reactive oxygen after DNA damage and that this increased oxidative stress is caused by depletion of NAD+ due to hyperactivation of the strand-break sensor, Poly(ADP-ribose) polymerase. Both hyperactivation of Poly(ADP-ribose) polymerase and increased ROS levels were reversed by use of a specific Poly(ADP-ribose) polymerase inhibitor. The extremely high incidence of malignancy among NBS patients is the result of the combination of a primary DSB repair deficiency with secondary oxidative DNA damage

A Systematic Proteomic Study of Irradiated DNA Repair Deficient Nbn-Mice

BACKGROUND: The NBN gene codes for the protein nibrin, which is involved in the detection and repair of DNA double strand breaks (DSBs). The NBN gene is essential in mammals. METHODOLOGY/PRINCIPAL FINDINGS: We have used a conditional null mutant mouse model in a proteomics approach to identify proteins with modified expression levels after 4 Gy ionizing irradiation in the absence of nibrin in vivo. Altogether, amongst approximately 8,000 resolved proteins, 209 were differentially expressed in homozygous null mutant mice in comparison to control animals. One group of proteins significantly altered in null mutant mice were those involved in oxidative stress and cellular redox homeostasis (p<0.0001). In substantiation of this finding, analysis of Nbn null mutant fibroblasts indicated an increased production of reactive oxygen species following induction of DSBs. CONCLUSIONS/SIGNIFICANCE: In humans, biallelic hypomorphic mutations in NBN lead to Nijmegen breakage syndrome (NBS), an autosomal recessive genetic disease characterised by extreme radiosensitivity coupled with growth retardation, immunoinsufficiency and a very high risk of malignancy. This particularly high cancer risk in NBS may be attributable to the compound effect of a DSB repair defect and oxidative stress

Impact of Sarcopenia and Bone Mineral Density on Implant Failure after Dorsal Instrumentation in Patients with Osteoporotic Vertebral Fractures

Background and Objectives: Age-related loss of bone and muscle mass are signs of frailty and are associated with an increased risk of falls and consecutive vertebral fractures. Management often necessitates fusion surgery. We determined the impacts of sarcopenia and bone density on implant failures (IFs) and complications in patients with spondylodesis due to osteoporotic vertebral fractures (OVFs). Materials and Methods: Patients diagnosed with an OVF according to the osteoporotic fracture classification (OF) undergoing spinal instrumentation surgery between 2011 and 2020 were included in our study. The skeletal muscle area (SMA) was measured at the third lumbar vertebra (L3) level using axial CT images. SMA z-scores were calculated for the optimal height and body mass index (BMI) adjustment (zSMAHT). The loss of muscle function was assessed via measurement of myosteatosis (skeletal muscle radiodensity, SMD) using axial CT scans. The bone mineral density (BMD) was determined at L3 in Hounsfield units (HU). Results: A total of 68 patients with OVFs underwent instrumentation in 244 segments (mean age 73.7 &plusmn; 7.9 years, 60.3% female). The median time of follow-up was 14.1 &plusmn; 15.5 months. Sarcopenia was detected in 28 patients (47.1%), myosteatosis in 45 patients (66.2%), and osteoporosis in 49 patients (72%). The presence of sarcopenia was independent of chronological age (p = 0.77) but correlated with BMI (p = 0.005). The zSMAHT was significantly lower in patients suffering from an IF (p = 0.0092). Sarcopenia (OR 4.511, 95% CI 1.459&ndash;13.04, p = 0.0092) and osteoporosis (OR 9.50, 95% CI 1.497 to 104.7, p = 0.014) increased the likelihood of an IF. Using multivariate analysis revealed that the zSMAHT (p = 0.0057) and BMD (p = 0.0041) were significantly related to IF occurrence. Conclusion: Herein, we established sarcopenic obesity as the main determinant for the occurrence of an IF after instrumentation for OVF. To a lesser degree, osteoporosis was associated with impaired implant longevity. Therefore, measuring the SMA and BMD using an axial CT of the lumbar spine might help to prevent an IF in spinal fusion surgery via early detection and treatment of sarcopenia and osteoporosis

DNA damage in Nijmegen Breakage Syndrome cells leads to PARP hyperactivation and increased oxidative stress

Das Nijmegen-Breakage-Syndrom (NBS), ein autosomal rezessives Chromosomen- Bruchsyndrom, wird durch Mutationen im NBN-Gen verursacht. Das durch NBN kodierte Genprodukt Nibrin ist ein integraler Bestandteil des MRE11/RAD50/NBN (MRN) Komplex. Zu den Aufgaben des MRN-Komplexes zählt die Prozessierung von DNA-Doppelstrangbrüchen (DSBs). Zu den klinischen Merkmalen des NBS zählen eine ausgeprägte Immunschwäche, erhöhte Empfindlichkeit gegenüber ionisierenden Strahlen sowie eine hohe Inzidenz maligner Neoplasien. Diese spiegeln die Bedeutung von Nibrin für die DSB-Reparatur wider. Über 90% der Patienten sind Träger einer homoallelisch vorkommenden 5bp Deletion innerhalb des NBN-Gens. Die ersten Beschreibungen betroffener Patienten stammen aus dem niederländischen Städtchen Nijmegen. Der Mutationsursprung wird jedoch vor mehr als zweitausend Jahren innerhalb der slawischen Völker vermutet. Dies erklärt die vergleichsweise hohe Prävalenz des NBS in Zentral- und Ost-Europa. Die extrem hohe Inzidenz maligner Neoplasien, höher als bei allen anderen Chromosomen-Bruchsyndromen, legt eine über das eigentliche Reparaturdefizit hinausgehende Störung, mit Beitrag zur erhöhten Mutationsrate, des NBS nahe. Ein Verständnis der über die DSB-Reparatur hinausgehenden Auswirkungen von Mutationen des NBN-Gens ist eine wichtige Voraussetzung für die Entwicklung neuer Ansätze in der Therapie des NBS. Den Anstoß zu der im Folgenden vorgestellten Publikation gab die Beobachtung, dass Proteine, welche in Folge eines erhöhten oxidativen Stress gebildet werden, in Leberlysaten konditionaler Nbn knockout Mäuse 24h nach Bestrahlung, im Vergleich zu Wildtyp-Kontrollen, vermehrt exprimiert wurden. Oxidativer Stress wird als Ungleichgewicht zwischen der Produktion und Elimination reaktiver Sauerstoffspezies (ROS) definiert. Ursachen können entweder in einer Überproduktion oder einer gestörten Detoxifikation gefunden werden. Als Ursache eines erhöhtem oxidativen Stress bei einem DNA-Reparaturdefizitsyndrom wie NBS, wurde eine überschießende Aktivierung der Poly(ADP-ribose) Polymerase (PARP) aufgrund nicht reparierte DNA-DSBs vermutet. PARP fungiert als Nicotinamid- Adenin-Dinukleotid (NAD+) abhängiger DNA-Schadenssensor. Eine überschießende Aktivierung würde daher zum raschen Verbrauch der zellulären Speicher des als Co5 Enzym wichtigen NAD+ führen. Aus dem Verbrauch der NAD+-Speicher ergeben sich zwei Implikationen für die zelluläre Redox- Homeostase: Erstens, NADPH ist essentiell für die Regeneration des zentralen Anti-Oxidant Glutathione aus Glutathione-Disulfid notwendig; Zweitens, NADPH und NADH sind beide als direkte Radikalfänger wirksam. ROS sind wirkungsvolle Mutagene und führen zu einer schweren Schädigung der DNA. Eine Erhöhung des oxidativen Stress führt daher unvermeidlich zu einem Anstieg der Mutationsrate. In dieser Arbeit wurden Zellen von NBS-Patienten und murine Nbn knock-out Zellen nach Induktion von DSBs mit einem ROS sensitiven Fluoreszenzfarbstoff inkubiert und mittels Durchflußzytometrie analysiert. Es wird gezeigt, dass ein Verlust von Nibrin zu einem Anstieg des zellulären oxidativen Stresses 12h nach Auftreten der DNA Schäden führt. Eine Analyse poly-ADP ribosylierter Proteine der entsprechenden Zellen mittels Western- Blot, zeigt eine korrespondierende Erhöhung der PARP-Aktivität. Ebenso konnte ein konkomitantes Absinken der zellulären NAD+- Spiegel beobachtet werden. Durch Einsatz eines PARP-Inhibitors konnte ein Absinken von ROS, trotz bestehender DSBs, gezeigt werden. Hierdurch wurde erstmals ein direkter, kausaler Zusammenhang zwischen DSBs, PARP, NAD+ und ROS bewiesen. Diese Befunde stützen die Hypothese, dass die extrem hohe Prävalenz maligner Neoplasien bei Patienten mit NBS aus der kombinierten Wirkung von DNA- Reparaturdefizit und oxidativem Stress resultiert.The gene underlying the autosomal recessive Nijmegen-Breakage-Syndrome (NBS), a chromosome breakage syndrome, is NBN. The NBN gene product, nibrin, is an integral member of the MRE11/RAD50/NBN (MRN) complex which is essential for processing DNA double strand breaks (DSBs). The cardinal features of NBS, immunodeficiency, radiosensitivity and an extremely high cancer incidence, reflect the role of nibrin in DSB repair. Over 90% of patients with this hereditary cancer disorder are homoallelic for a 5bp deletion in the NBN gene. This mutation occurred in the Slavic population at least two thousand years ago and is therefore particularly frequent in eastern and central Europe, even though the first patients described were from the Dutch city of Nijmegen. Cancer occurrence is extremely high in NBS, higher than in any other chromosome breakage syndrome, suggesting that more than the DSB repair defect itself is contributing to an elevated mutation rate. Understanding the effects of the NBN mutation, beyond the DSB repair defect, is an important goal for the development of therapeutic options for the NBS patients. Starting point for the publication presented here was the finding that proteins involved in combating oxidative stress are more highly expressed 24 hours after irradiation in the livers of NBS knockout mice, in comparison to control mice. Oxidative stress is defined as an imbalance between the production and the elimination of reactive oxygen species (ROS) and can be due either to excessive ROS production or to a deficiency in ROS eradication. We hypothesized that, in the case of a DSB repair deficiency such as NBS, oxidative stress could be consequence of a hyperactivation of Poly(ADP-ribose) polymerase (PARP), a DNA strand-break sensor, due to the deficiency in DSB- Repair in NBS cells. PARP requires NAD+ and its hyperactivation leads to rapid depletion of the cellular pool of this important dinucleotide coenzyme. Loss of NAD+ has two effects on ROS elimination: firstly, NADPH is essential for the regeneration of the central cellular antioxidant glutathione from oxidized glutathione disulfide; secondly, NADPH and NADH have been implicated in the direct scavenging of radicals. ROS attack DNA and are extremely mutagenic; increased oxidative stress leads inevitably to an increased mutation rate. Using flow-cytometric analysis of NBS patient cells and Nbn knock out mouse cells stained with a sensitive fluorescent indicator of ROS content, it was proven that loss of nibrin results in increased levels of ROS 12 hours after a mutagenic treatment to induce DSBs. A corresponding increase in PARP activity could be demonstrated by western blot analysis of poly-ADP-ribosylated proteins. An accompanying rapid depletion of cellular NAD+ in comparison to control cells was also found. Importantly, repression of PARP activity with a specific pharmacological inhibitor reduced ROS levels despite the presence of DSBs. Thus, a direct link between DSBs, PARP, NAD+ and ROS could be proven. The extremely high incidence of malignancy among NBS patients is thus the result of the combination of a primary DSB repair deficiency with secondary oxidative DNA damage

The importance of thrombin in cerebral injury and disease

There is increasing evidence that prothrombin and its active derivative thrombin are expressed locally in the central nervous system. so far, little is known about the physiological and pathophysiological functions exerted by thrombin in the human brain. extra-hepatic prothrombin expression has been identified in neuronal cells and astrocytes via mrna measurement. the actual amount of brain derived prothrombin is expected to be 1% or less compared to that in the liver. the role in brain injury depends upon its concentration, as higher amounts cause neuroinflammation and apoptosis, while lower concentrations might even be cytoprotective. its involvement in numerous diseases like alzheimer’s, multiple sclerosis, cerebral ischemia and haemorrhage is becoming increasingly clear. this review focuses on elucidation of the cerebral thrombin expression, local generation and its role in injury and disease of the central nervous system

Involuntary ambulatory triage during the COVID-19 pandemic – A neurosurgical perspective

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic poses an unprecedented challenge to health-care systems around the world. As approximately one-third of the world´s population is living under “lockdown” conditions, medical resources are being reallocated and hospital admissions are limited to emergencies. We examined the decision-making impact of these actions and their effects on access to hospital treatment in patients with neurosurgical conditions. METHODS: This retrospective cohort study analyzes hospital admissions of two major neurosurgical services in Germany during the nationwide lockdown period (March 16th to April 16th, 2020). Spinal or cranial conditions requiring immediate hospital admission and treatment constituted emergencies. RESULTS: A total of 243 in-patients were treated between March 16th and April 16th 2020 (122 patients at the University Medical Center Mainz, 121 patients at the University Medical Center Göttingen). Of these, 38.0±16% qualified as emergency admission. Another 1,688 admissions were reviewed during the same periods in 2018 and 2019, providing a frame of reference. Overall, emergency admissions declined by 44.7±0.7% during lockdown. Admissions for cranial emergencies fell by 48.1±4.44%, spinal emergencies by 30.9±14.6%. CONCLUSION: Above findings indicate that in addition to postponing elective procedures, emergency admissions were dramatically curtailed during the COVID-19 lockdown. As this surely is unexpected and unintended, reasons are undoubtedly complex. As consequences in morbidity and mortality are still unpredictable, efforts should be made to accommodate all patients in need of hospital access going forward

The Importance of Thrombin in Cerebral Injury and Disease

There is increasing evidence that prothrombin and its active derivative thrombin are expressed locally in the central nervous system. So far, little is known about the physiological and pathophysiological functions exerted by thrombin in the human brain. Extra-hepatic prothrombin expression has been identified in neuronal cells and astrocytes via mRNA measurement. The actual amount of brain derived prothrombin is expected to be 1% or less compared to that in the liver. The role in brain injury depends upon its concentration, as higher amounts cause neuroinflammation and apoptosis, while lower concentrations might even be cytoprotective. Its involvement in numerous diseases like Alzheimer’s, multiple sclerosis, cerebral ischemia and haemorrhage is becoming increasingly clear. This review focuses on elucidation of the cerebral thrombin expression, local generation and its role in injury and disease of the central nervous system

Thrombin contributes to the injury development and neurological deficit after acute subdural hemorrhage in rats only in collaboration with additional blood-derived factors

Abstract Background Acute subdural hemorrhage (ASDH) is a severe consequence of traumatic brain injury. The occurrence of subdural blood increases the lethality of these patients independent of the amount of blood or elevated intracranial pressure. Thrombin is one of the potential harmful blood components. Possible harmful effects of thrombin are mediated via the Protease-activated-receptor-1 (PAR1) and thus, translating the acute Thrombin release after ASDH into cell loss. The objectives of the present study were twofold, namely to examine (1) the impact of direct thrombin inhibition in the acute phase after hemorrhage on the long-term histological and functional deficits and (2) the early inhibition of PAR1 activation by thrombin with the selective antagonist SCH79797 on lesion volume at 14 days after ASDH. The effects of thrombin on the lesion size were investigated in two separate experiments via (1) direct thrombin inhibition in the subdural infused blood (Argatroban 600 µg) as well as by (2) intraventricular injection of the PAR-1 antagonist SCH79797 (1 µg or 5 µg). Lesion volume and behavior deficits using a neurological deficit score and a motor function test (beam balance test) were analyzed as outcome parameters at 14 days after injury. Results 59 Male Sprague–Dawley rats received a subdural infusion of 300 µl autologous blood or sham operation. Lesion volume at 14 days after ASDH tended to be smaller in the Argatroban-treated group when compared to the vehicle group (8.1 ± 1.1 vs. 10.1 ± 2.3 mm2, n.s.). Motor deficits in the beam balance test were not significantly less severe in the Argatroban-treated group. Animals treated with SCH79797 also showed a trend towards dose-dependent decreased lesion volume in comparison to the vehicle-treated group (1 μg: 4.3 ± 0.7 mm3; 5 μg: 3.8 ± 1.1 mm3; vehicle: 6.5 ± 2.0 mm3, n.s). Conclusions Thrombin inhibition in the subdural blood and local cerebral blockade of PAR-1 cause a tendency towards reduced lesion volume or functional recovery. All results show a trend in favor of the acute treatment on the outcome parameters. Our results suggests that thrombin could be an important blood-derived factor during acute subdural hemorrhage that translates its deleterious effects in concert with other blood-induced factors