| 1. |
- Gram, Magnus, et al.
(författare)
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Extracellular hemoglobin - mediator of inflammation and cell death in the choroid plexus following preterm intraventricular hemorrhage
- 2014
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Ingår i: Journal of Neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Intraventricular hemorrhage (IVH) with post-hemorrhagic ventricular dilatation (PHVD) is a major cause of neurodevelopmental impairment and mortality in preterm infants. The mechanisms leading to PHVD and brain damage remain largely unknown. The choroid plexus and the ependyma, which constitute an essential part of the blood-brain barrier (BBB), are the first structures to encounter the damaging effects of extravasated blood. The breakdown of the BBB is a critical upstream event leading to brain damage following IVH. In this study we investigated the impact of hemorrhage and hemoglobin (Hb) metabolites on the choroid plexus epithelium. Methods: Using a preterm rabbit pup model of IVH, the structural and functional integrity, cellular, inflammatory and oxidative response of the choroid plexus, at 24 and 72 hours following IVH + PHVD, were investigated. In order to further characterize cellular and molecular mechanisms, primary human choroid plexus epithelial cells were exposed to cerebrospinal fluid (CSF) from preterm infants with IVH as well as to Hb-metabolites. Finally, the blocking effects of the Hb-scavenger haptoglobin (Hp) were investigated both in vivo and in vitro. Results: Following IVH + PHVD, an up-regulation of mRNA for the receptor-related genes TLR-4, IL1R1, FAS, the transcription factor NF-kappa beta and for the pro-inflammatory and chemotactic effector molecules, IL-1 beta, TNF alpha, MCP-1, IL-8, and IL-6 was observed in the choroid plexus at 24 and 72 hours. This was associated with structural disintegration, caspase activation and cell death in the choroid plexus epithelium. In vitro characterization of choroid plexus epithelial cells, following exposure to hemorrhagic CSF and to the Hb-metabolites metHb and heme, displayed apoptotic and necrotic cell death and an up-regulation of receptor-related and inflammatory effector molecules similar to that observed in vivo following IVH + PHVD. Intraventricular injection of the Hb-scavenger Hp in vivo and co-incubation with Hp in vitro reversed or reduced the cellular activation, inflammatory response, structural damage and cell death. Conclusion: Hb-metabolites are important causal initiators of cell death following IVH and removal or scavenging of Hb-metabolites may present an efficient means to reduce the damage to the immature brain following IVH.
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| 2. |
- Ley, David, et al.
(författare)
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High presence of extracellular hemoglobin in the periventricular white matter following preterm intraventricular hemorrhage
- 2016
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 7:AUG
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Tidskriftsartikel (refereegranskat)abstract
- Severe cerebral intraventricular hemorrhage (IVH) in preterm infants continues to be a major clinical problem, occurring in about 15-20% of very preterm infants. In contrast to other brain lesions the incidence of IVH has not been reduced over the last decade, but actually slightly increased. Currently over 50% of surviving infants develop post-hemorrhagic ventricular dilatation and about 35% develop severe neurological impairment, mainly cerebral palsy and intellectual disability. To date there is no therapy available to prevent infants from developing either hydrocephalus or serious neurological disability. It is known that blood rapidly accumulates within the ventricles following IVH and this leads to disruption of normal anatomy and increased local pressure. However, the molecular mechanisms causing brain injury following IVH are incompletely understood. We propose that extracellular hemoglobin is central in the pathophysiology of periventricular white matter damage following IVH. Using a preterm rabbit pup model of IVH the distribution of extracellular hemoglobin was characterized at 72 h following hemorrhage. Evaluation of histology, histochemistry, hemoglobin immunolabeling and scanning electron microscopy revealed presence of extensive amounts of extracellular hemoglobin, i.e., not retained within erythrocytes, in the periventricular white matter, widely distributed throughout the brain. Furthermore, double immunolabeling together with the migration and differentiation markers polysialic acid neural cell adhesion molecule (PSA-NCAM) demonstrates that a significant proportion of the extracellular hemoglobin is distributed in areas of the periventricular white matter with high extracellular plasticity. In conclusion, these findings support that extracellular hemoglobin may contribute to the pathophysiological processes that cause irreversible damage to the immature brain following IVH.
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| 3. |
- Sveinsdóttir, Kristbjörg, et al.
(författare)
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Impaired Cerebellar Maturation, Growth Restriction, and Circulating Insulin-Like Growth Factor 1 in Preterm Rabbit Pups
- 2017
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Ingår i: Developmental Neuroscience. - : S. Karger AG. - 0378-5866 .- 1421-9859. ; 39:6, s. 487-497
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Tidskriftsartikel (refereegranskat)abstract
- Cerebellar growth is impeded following very preterm birth in human infants and the observed reduction in cerebellar volume is associated with neurodevelopmental impairment. Decreased levels of circulating insulin-like growth factor 1 (IGF-1) are associated with decreased cerebellar volume. The relationship between preterm birth, circulating IGF-1, and key cell populations supporting cerebellar proliferation is unknown. The aim of this study was to evaluate the effect of preterm birth on postnatal growth, circulating IGF-1, and cerebellar maturation in a preterm rabbit pup model. Preterm rabbit pups (PT) were delivered by cesarean section at day 29 of gestation, cared for in closed incubators with humidified air, and gavage fed with formula. Control term pups (T) delivered by spontaneous vaginal delivery at day 32 of gestation were housed and fed by their lactating doe. In vivo perfusion-fixation for immunohistochemical evaluation of cerebellar prolif-eration, cell maturation, and apoptosis was performed at repeated time points in PT and T pups. Results show that the mean weight of the pups and circulating IGF-1 protein levels were lower in the PT group at all time points (p < 0.05) than in the T group. Postnatal weight development correlated with circulating IGF-1 (r(2) = 0.89) independently of gestational age at birth and postnatal age. The proliferative (Ki-67-positive) portion of the external granular layer (EGL) was decreased in the PT group at postnatal day 2 (P2) compared to in the T group (p = 0.01). Purkinje cells exhibited decreased calbindin staining at P0 (p = 0.003), P2 (p = 0.004), and P5 (p = 0.04) in the PT group compared to in the T group. Staining for sonic hedgehog was positive in neuronal EGL progenitors and Purkinje cells at early time points but was restricted to a welldefined Purkinje cell monolayer at later time points. Preterm birth in rabbit pups is associated with lower circulating levels of IGF-1, decreased postnatal growth, and decreased cerebellar EGL proliferation and Purkinje cell maturation. The preterm rabbit pup model exhibits important characteristics of human preterm birth, and may thus be suitable for the evaluation of interventions aiming to modify growth and cerebellar development in the preterm population. (C) 2017 S. Karger AG, Basel
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| 4. |
- Sveinsdottir, Snjolaug, et al.
(författare)
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Altered Expression of Aquaporin 1 and 5 in the Choroid Plexus following Preterm Intraventricular Hemorrhage.
- 2014
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Ingår i: Developmental Neuroscience. - : S. Karger AG. - 1421-9859 .- 0378-5866. ; 36:6, s. 542-551
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Tidskriftsartikel (refereegranskat)abstract
- Intraventricular hemorrhage (IVH) with posthemorrhagic ventricular dilatation (PHVD) is a common cause of hydrocephalus in infants. Dysregulation of cerebrospinal fluid (CSF) production by the choroid plexus may contribute to the development of PHVD. The aquaporins (AQPs), transmural water transporting proteins, are believed to contribute to CSF production. The aim of the study was to characterize the expression and localization of AQP1, 4 and 5 in the choroid plexus following preterm IVH. Using a preterm rabbit pup model, the mRNA expression, protein level and localization of AQP1, 4 and 5 were investigated in the choroid plexus at 24 and 72 h following IVH with PHVD. Further, AQP1, 4 and 5 expression were characterized in primary human plexus epithelial cells exposed to CSF from preterm human infants with IVH and to hemoglobin metabolites. IVH with PHVD in the immature brain caused a downregulation of AQP1 mRNA, the key AQP in CSF production, but an upregulation of AQP1 protein level with apical epithelial cell localization. Notably, AQP5 was expressed in the choroid plexus with upregulated mRNA expression and protein levels during PHVD with apical epithelial cell localization. Analysis of human choroid plexus epithelial cells in vitro, following exposure to posthemorrhagic CSF and to hemin, displayed results concordant with those observed in vivo, i.e. downregulation of AQP1 mRNA and upregulation of AQP5 mRNA expression. AQP4 was neither detectable in vivo nor in vitro. The changes observed in AQP1 and AQP5 expression in the choroid plexus suggest an adaptive response following IVH with possible functional implications for the development of PHVD. © 2014 S. Karger AG, Basel.
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| 5. |
- Erlöv, Tobias, et al.
(författare)
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Automatic Measurements of Diameter, Distension and Intima Media Thickness of the Aorta in Premature Rabbit Pups Using B-Mode Images.
- 2014
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 40:2, s. 371-377
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Tidskriftsartikel (refereegranskat)abstract
- To improve cardiovascular research, there is a growing need for arterial characterization in small animals. We developed a method, ARTIC (arterial characterization) for measuring lumen diameter, distension and intima media thickness (IMT). In this study ARTIC was used to automatically characterize the aorta of premature rabbit pups. Automatic measurements were compared with manual measurements, both performed by three observers. Diameter was 769 ± 140 μm (manual) and 766 ± 142 μm (automatic), distension was 35 ± 15 μm (manual) and 40 ± 12 μm (automatic) and IMT was 84 ± 11 μm (manual) and 88 ± 8 μm (automatic) (mean ± standard deviation). The variation in the measured diameter, distension and IMT ranged from 1.1% to 26.0% (manual) and from 1.0% to 9.0% (automatic). The intra-class correlation coefficient ranged from 33.0% to 99.3% (manual) and from 76.9% to 99.6% (automatic). The evaluation revealed that it is feasible to use ARTIC on B-mode images of arteries with small dimensions, which makes it a useful tool for arterial characterization in small animals.
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| 6. |
- Gram, Magnus, et al.
(författare)
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Hemoglobin induces inflammation after preterm intraventricular hemorrhage by methemoglobin formation.
- 2013
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Ingår i: Journal of Neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 10:Aug.,6
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Tidskriftsartikel (refereegranskat)abstract
- Cerebral intraventricular hemorrhage (IVH) is a major cause of severe neurodevelopmental impairment in preterm infants. To date, no therapy is available that prevents infants from developing serious neurological disability following IVH. Thus, to develop treatment strategies for IVH, it is essential to characterize the initial sequence of molecular events that leads to brain damage. In this study, we investigated extracellular hemoglobin (Hb) as a causal initiator of inflammation in preterm IVH.
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| 7. |
- Romantsik, Olga, et al.
(författare)
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The heme and radical scavenger α1-microglobulin (A1M) confers early protection of the immature brain following preterm intraventricular hemorrhage
- 2019
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Ingår i: Journal of Neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Germinal matrix intraventricular hemorrhage (GM-IVH) is associated with cerebro-cerebellar damage in very preterm infants, leading to neurodevelopmental impairment. Penetration, from the intraventricular space, of extravasated red blood cells and extracellular hemoglobin (Hb), to the periventricular parenchyma and the cerebellum has been shown to be causal in the development of brain injury following GM-IVH. Furthermore, the damage has been described to be associated with the cytotoxic nature of extracellular Hb-metabolites. To date, there is no therapy available to prevent infants from developing either hydrocephalus or serious neurological disability. Mechanisms previously described to cause brain damage following GM-IVH, i.e., oxidative stress and Hb-metabolite toxicity, suggest that the free radical and heme scavenger α1-microglobulin (A1M) may constitute a potential neuroprotective intervention. Methods: Using a preterm rabbit pup model of IVH, where IVH was induced shortly after birth in pups delivered by cesarean section at E29 (3 days prior to term), we investigated the brain distribution of recombinant A1M (rA1M) following intracerebroventricular (i.c.v.) administration at 24 h post-IVH induction. Further, short-term functional protection of i.c.v.-administered human A1M (hA1M) following IVH in the preterm rabbit pup model was evaluated. Results: Following i.c.v. administration, rA1M was distributed in periventricular white matter regions, throughout the fore- and midbrain and extending to the cerebellum. The regional distribution of rA1M was accompanied by a high co-existence of positive staining for extracellular Hb. Administration of i.c.v.-injected hA1M was associated with decreased structural tissue and mitochondrial damage and with reduced mRNA expression for proinflammatory and inflammatory signaling-related genes induced by IVH in periventricular brain tissue. Conclusions: The results of this study indicate that rA1M/hA1M is a potential candidate for neuroprotective treatment following preterm IVH.
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| 8. |
- Segstedt, Simon, et al.
(författare)
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Arterial diameter change measurements in premature rabbit pups using B-Mode images
- 2012
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Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). ; , s. 922-924
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Konferensbidrag (refereegranskat)abstract
- To further promote cardiovascular research there is a growing need for arterial characterization on small animals. Arterial wall movement measurements form the basis for most stiffness related parameters. As far as we know, previous reports on lumen diameter change measurements in small animals have required ECG triggering and cross-correlation techniques on the RF-signal using extremely high frame rate. The first aim of this study was to evaluate a novel method, ARTerIal Characterization (ARTIC), for robust diameter measurements in premature rabbit pups using conventional scanning technique (B-mode, 230 Hz). Although blood pressure is important for arterial stiffness measurements, it is often impossible to obtain without affecting the animal setup. However, arterial stiffness can also be assessed by measuring the pressure independent transition strain as recently proposed by Danpinid et al. (Ultrasonics 50, 2010: 654-665). The second aim was to investigate the feasibility of measuring transition strain in premature rabbit pups using the obtained diameter curve. The diameter was 874/82 mu m (mean/SD), CV 2.9%. The distension was 24+/-3 mu m, CV 7.3%. The transition strain was 1.55+/-0.46%, CV 12.8%. In summary, ARTIC can measure arterial diameter and distension in small animals using B-Mode images at regular frame rates. ARTIC also has a low computation time suitable for real-time implementation. Measurements of transition strain on premature rabbit pups are feasible using B-Mode images at regular frame rate. (Abstract)
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| 9. |
- Sveinsdottir, Snjolaug, et al.
(författare)
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High-frequency ultrasound in the evaluation of cerebral intraventricular haemorrhage in preterm rabbit pups.
- 2012
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629. ; 38:3, s. 423-431
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Tidskriftsartikel (refereegranskat)abstract
- Cerebral intraventricular haemorrhage (IVH) is the most common cause of severe neurologic impairment following preterm birth in human infants. Ideally, an animal model for cerebral IVH should allow for reliable noninvasive evaluation of haemorrhagic extension and of subsequent development of posthaemorrhagic ventricular dilatation (PHVD). The aim of this study was to evaluate the use of high-frequency ultrasound (HFU) in premature rabbit pups with cerebral IVH induced by IP glycerol injection. Serial examinations using HFU enabled an accurate description of haemorrhagic extension and measurement of progressive PHVD over 72 h. The coefficient of variation for inter- and intraobserver variability in two measurements of ventricular size was less than 8.8% and 9.3%, respectively. Repeated ultrasound-guided intraventricular injection and sampling could be performed in vivo excluding requirement of stereotactic procedures and sedation. Application of HFU is a powerful tool for the evaluation of mechanisms involved in cerebral IVH and PHVD in the preterm rabbit pup model.
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| 10. |
- Sveinsdottir, Snjolaug
(författare)
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Preterm intraventricular haemorrhage - Effects of extracellular haemoglobin
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intraventricular haemorrhage (IVH) is the most common brain lesion in preterm infants and is most commonly seen in the sickest children, with 15-20% of very preterm infants developing IVH. The mortality of infants with severe IVH is 20-50 % in the neonatal period and over 50 % of surviving infants develop post-haemorrhagic ventricular dilatation (PHVD) and 40-80 % develop severe neurological impairment, mainly cerebral palsy and mental retardation. To date there is no available therapy to prevent infants from developing either hydrocephalus or serious neurological disability. Infants who develop hydrocephalus receive a life-long ventriculo-peritoneal shunt, which is an efficient means of preventing ventricular distension but does not reduce neurological impairment. Mechanisms leading to brain damage and hydrocephalus following IVH are complex and incompletely understood. However, inflammation and oxidative stress have been identified as two major culprits leading to irreversible damage in the vulnerable immature periventricular brain matter. Dysfunction of cerebrospinal fluid (CSF) production contributes to the development of PHVD but the exact molecular mechanisms remain unknown. The choroid plexus, which produces the CSF, is adjacent to the origin of IVH and is the first organ to encounter the extravasated blood. The subsequent haemolysis of red blood cells causes release of cell-free haemoglobin (Hb), which will with time further degrade releasing the toxic substances hemin, free iron, and various ROS (reactive oxygen species). Metabolites of cell-free Hb have been identified as an initiator of inflammation in the context of adult cerebral haemorrhage and inflammation of the ependyma has been shown to cause alterations of the blood-brain barrier (BBB). Our working hypothesis is that cell-free Hb and its metabolites act as causal initiators of inflammation following IVH, constituting a critical up-stream event eventually leading to periventricular cell death. We further hypothesize that inflammation of the choroid plexus alters the ability of the epithelium to maintain CSF homeostasis contributing to the formation of post-haemorrhagic hydrocephalus. To test the hypothesis we used the rabbit pup model of preterm IVH. It is excellently suited since rabbit pups have a germinal matrix with vulnerable capillary meshwork prone to rupture and have CNS maturation comparable to a 28-30 weeks preterm human infant. The application of high-frequency ultrasound enabled accurate measurements of haemorrhagic size and distension as well as ultrasound guided intraventricular injections and CSF sampling. Following IVH there is a release of free haemoglobin in its reduced form, oxyHb, into the intraventricular space. OxyHb autooxidises to metHb over time and the concentration of the key inflammatory cytokine TNF-α is highly correlated to that of metHb. In an astrocyte cell culture, metHb induces TNF-α production whereas oxyHb does not. We therefore conclude that the formation of metHb is a key up-stream event leading to inflammation following IVH. Following IVH there is extensive damage to the choroid plexus epithelium, which develops over time. There is a distinct inflammatory and cellular response induced by haemoglobin metabolites. Injection or co-incubation with haptoglobin, a haemoglobin scavenger, reduces or reverses the effects of haemoglobin both in vivo and in vitro. Aquaporins (AQP) are water transporting transmembrane proteins playing a central role in CSF production. Following IVH the expression of AQP1, the key AQP in the choroid plexus, is down-regulated whereas the expression of AQP5, not previously described in the choroid plexus, is up-regulated. This probably represents an adaptive response to insult and might be of importance in understanding the development of PHVD. In conclusion; following IVH released cell free haemoglobin, metabolized to metHb and hemin, constitutes a causal up-stream initiator of inflammation and cellular damage. Scavenging or removal of haemoglobin might be an efficient and feasible approach to reduce brain damage following preterm IVH.
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