Abstracts
Objective
We developed an in vitro model for vasospasm post subarachnoid hemorrhage that was suitable for investigating brain vessel autoregulation. We further investigated the effects of iodinated contrast medium on the vascular tone and the myogenic response of spastic cerebral vessels.
Method
We isolated and perfused the superior cerebellar arteries of rats. The vessels were pressurized and studied under isobaric conditions. Coagulated blood was used to simulate subarachnoid hemorrhage. The contrast medium iodixanol was applied intraluminally.
Results
Vessels exposed to blood developed significantly stronger myogenic tone (65.7 ± 2.0% vs 77.1 ± 1.2% of the maximum diameter, for the blood and the control group, respectively) and significantly decreased myogenic response, compared with the control groups. The contrast medium did not worsen the myogenic tone or the myogenic response in any group.
Conclusion
Our results show that deranged myogenic response may contribute to cerebral blood flow disturbances subsequent to subarachnoid hemorrhage. The contrast medium did not have any negative influence on vessel tone or myogenic response in this experimental setting.
brain ischemia; cerebral angiography; contrast media; hemodynamics; intracranial aneurysm; intracranial vasospasm; subarachnoid hemorrhage
Objetivo
Desenvolvemos um modelo in vitro para vasoespasmo subsequente à hemorragia subaracnóide que foi adequado para investigar a autorregularão dos vasos cerebrais. Em seguida investigamos os efeitos o meio de contraste iodado no tônus vascular e na resposta miogênica dos vasos cerebrais espásticos.
Método
Isolamos e perfundimos as artérias cerebelares superiores de ratos. Os vasos foram pressurizados e estudados em condições isobáricas. Sangue coagulado foi utilizado para simular hemorragia subaracnóide. O meio de contraste iodixanol foi aplicado intraluminarmente.
Resultados
Os vasos expostos ao sangue desenvolveram aumento significativo do tônus miogênico (65.7 ± 2.0% vs 77.1 ± 1.2% do maior diâmetro, para o grupo de sangue e o grupo controle, respectivamente) com resposta miogênica significativamente menor do que aquela dos controles. O meio de contraste iodado não piorou o tônus miogênico ou a resposta miogênica em nenhum dos grupos.
Conclusão
Nossos resultados mostram que uma resposta miogênica pode contribuir para as alterações de fluxo sanguíneo cerebral subsequentes à hemorragia subaracnóide. O meio de contraste iodado não teve nenhuma influência negativa no tônus vascular ou na resposta miogênica neste modelo experimental.
isquemia cerebral; angiografia cerebral; meio de contraste; hemodinâmica; aneurisma intracraniano; vasoespasmo intracraniano; hemorragia subaracnóide
Cerebral delayed vasospasm is a severe complication following spontaneous subarachnoid
hemorrhage (SAH). Vasospasm is an important cause of death and contributes 10-12% to the
overall mortality after SAH, which reaches approximately 50% within the first month11 Odom MJ, Zuckerman SL, Mocco J. The role of magnesium in the
management of cerebral vasospasm. Neurol Res Int.
2013;2013:ID943914.,22 Ciurea AV, Palade C, Voinescu D, Nica DA. Subarachnoid hemorrhage
and cerebral vasospasm - Literature review. J Med Life.
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.
There is nowadays no specific therapy or prophylaxis for vasospasm22 Ciurea AV, Palade C, Voinescu D, Nica DA. Subarachnoid hemorrhage
and cerebral vasospasm - Literature review. J Med Life.
2013;6:120-5.,44 Athar MK, Levine JM. Treatment options for cerebral vasospasm in
aneurysmal subarachnoid hemorrhage. Neurotherapeutics. 2012;9(1):37-43.
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emerging therapeutic interventions. Neurol Res Int. 2013;2013:ID462491.
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.
The low success of current treatment strategies for vasospasm may be due to insufficient
knowledge about the pathophysiology of vasospasm, despite a large number of in
vitro and in vivo studies done to discover spastic
mechanisms and to find an adequate treatment for cerebral vasospasm66 Marbacher S, Fandino J, Kitchen ND. Standard intracranial in vivo
animal models of delayed cerebral vasospasm. Br J Neurosurg. 2010;24(4):415-34.
http://dx.doi.org/10.3109/02688691003746274
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.
The majority of studies on the mechanism of vasospasm were performed using in
vivo animal models33 Titova E, Ostrowski RP, Zhang JH, Tang J. Experimental models of
subarachnoid hemorrhage for studies of cerebral vasospasm. Neurol Res.
2009;31(6):568-81. http://dx.doi.org/10.1179/174313209X382412
https://doi.org/10.1179/174313209X382412...
,66 Marbacher S, Fandino J, Kitchen ND. Standard intracranial in vivo
animal models of delayed cerebral vasospasm. Br J Neurosurg. 2010;24(4):415-34.
http://dx.doi.org/10.3109/02688691003746274
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Controversies and evolving new mechanisms in subarachnoid hemorrhage. Prog
Neurobiol. 2014;115:64-91.
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.
While in vivo studies successfully reproduce the clinical picture of
vasospasm, there is high individual variability in their results66 Marbacher S, Fandino J, Kitchen ND. Standard intracranial in vivo
animal models of delayed cerebral vasospasm. Br J Neurosurg. 2010;24(4):415-34.
http://dx.doi.org/10.3109/02688691003746274
https://doi.org/10.3109/0268869100374627...
, what limits their application for studying effects of
vasospasm on mechanisms of cerebral blood flow regulation. The use of in vitro
models, where conditions like intraluminal pressure, oxygen tension, and milieu
surrounding the vessels are constant, might reduce these disadvantages. Unfortunately,
current in vitro models of vasospasm that use whole blood to simulate
SAH88 Simeone FA, Vinall P. Mechanisms of contractile response of cerebral
artery to externally-applied fresh blood. J Neurosurg. 1975;43(1):37-47.
http://dx.doi.org/10.3171/jns.1975.43.1.0037
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,99 Linder M, Alksne JF. Prevention of persistent cerebral smooth muscle
contraction in response to whole blood. Stroke. 1978;9(5):472-7.
http://dx.doi.org/10.1161/01.STR.9.5.472
https://doi.org/10.1161/01.STR.9.5.472...
are technically unsuitable for
investigation of the autoregulation of cerebral vessels, mostly because presence of
blood prevents visualization of a pressurized vessel and diameter measurements. We
developed a novel, highly reproducible and technically uncomplicated model of
vasospasm in vitro using a perfusion myograph and videomicroscopy
to investigate the myogenic response of cerebral vessels – one of the main
mechanisms of cerebral blood flow autoregulation1010 Schubert R, Mulvany M. The myogenic response: established facts and
attractive hypotheses. Clin Sci. 1999;96(4):313-26.
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contribution of NOS interneurons in the physiology of cerebrovascular
regulation. Front Neural Circuits. 2012;6:51.
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.
Most diagnostic and therapeutic procedures needed for the treatment of SAH patients
require the use of iodinated contrast media (CM)1212 Kellner P, Stoevesandt D, Soukup J, Bucher M, Raspé C.
Aneurysmatisch bedingte Subarachnoidalblutung. Anaesthesist. 2012;61(9):792-814.
http://dx.doi.org/10.1007/s00101-012-2077-2
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,1313 Seibert B, Tummala RP, Chow R, Faridar A, Mousavi SA, Divani AA.
Intracranial aneurysms: review of current treatment options and outcomes. Front
Neurol. 2011;2:45. http://dx.doi.org/10.3389/fneur.2011.00045
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,1414 Keyrouz SG, Diringer MN. Clinical review: prevention and therapy of
vasospasm in subarachnoid hemorrhage. Crit Care. 2007;11(4):220.
http://dx.doi.org/10.1186/cc5958
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. It has been shown that CM have adverse effects on vessels of
the kidney and other vascular beds1515 Sendeski M, Patzak A, Persson PB. Constriction of the vasa recta,
the vessels supplying the area at risk for acute kidney injury, by four
different iodinated contrast media, evaluating ionic, nonionic, monomeric and
dimeric agents. Invest Radiol. 2010;45(8):453-7.
http://dx.doi.org/10.1097/RLI.0b013e3181d77eed
https://doi.org/10.1097/RLI.0b013e3181d7...
,1616 Sendeski MM. Pathophysiology of renal tissue damage by iodinated
contrast media. Clin Exp Pharmacol Physiol. 2011;38(5):292-9.
http://dx.doi.org/10.1111/j.1440-1681.2011.05503.x
https://doi.org/10.1111/j.1440-1681.2011...
. Further, CM influence some components of cerebral blood flow
regulation in healthy subjects1717 Rosengarten B, Steen Müeller MK, Müeller A, Traupe H, Voss
RK, Kaps M. Contrast media effect on cerebral blood flow regulation after
performance of cerebral or coronary angiography. Cerebrovasc Dis.
2003;16(1):42-6. http://dx.doi.org/10.1159/000070114
https://doi.org/10.1159/000070114...
. We
thus tested the hypothesis that CM negatively influence the autoregulation of cerebral
blood flow after SAH.
METHOD
All animal handling and experiments were performed in accordance to the guidelines of the Office for Health and Social Matters of Berlin (Berlin, Germany).
Isolation and preparation of cerebral vessels
Adult male Sprague Dawley rats (Charles River, Germany), 150-200 grams (7-8 weeks
old), were anaesthetized using isoflurane (Abbott, Baar, Switzerland) and
decapitated. Brains were excised and placed in ice-cold preparation
physiological salt solution. Segments of superior cerebellar arteries without
branches in a diameter of about 250 µm were isolated under magnification
using sharpened forceps and microscopic scissors, and mounted on glass cannulas
within the myograph's experimental chamber. As usual in experiments
investigating myogenic response, there was no flow inside the vessel1818 Seker F, Hesser J, Neumaier-Probst E, Groden C, Brockmann MA,
Schubert R et al. Dose-response relationship of locally applied nimodipine in an
ex vivo model of cerebral vasospasm. Neuroradiology. 2013;55(1):71-6.
http://dx.doi.org/10.1007/s00234-012-1079-8
https://doi.org/10.1007/s00234-012-1079-...
.
Altogether 73 rats were included in the study. 50 successful experiments were performed. Excluding criteria were: intraluminal flow due to lacks or vessel branches and insufficient development of spontaneous myogenic tone (< 20%). Experimental groups and number of experiments are shown in Table.
Experimental conditions
Intraluminal
The intraluminal solution consisted of experimental physiological salt
solution (PSS) (146 mmol/l NaCl, 4.5 mmol/l KCl, 1.2 mmol/l
NaH2PO4, 1.0 mmol/l MgSO4, 1.6 mmol/l
CaCl2, 5.5 mmol/l glucose, 0.025 mmol/l EDTA, 5.0 mmol/l
HEPES, pH 7.4 by temperature 37.0°C). The groups which received CM had
an end concentration of 23 mg iodine/ml (1.8*10−44 Athar MK, Levine JM. Treatment options for cerebral vasospasm in
aneurysmal subarachnoid hemorrhage. Neurotherapeutics. 2012;9(1):37-43.
http://dx.doi.org/10.1007/s13311-011-0098-1
https://doi.org/10.1007/s13311-011-0098-...
mol/l) (iodixanol, GE
Healthcare, Munich, Germany) in the intraluminal solution. The CM
concentration is the same shown to cause constriction of renal vasa recta
and afferent arterioles, and is within the range possibly reached during
intravascular procedures in humans1515 Sendeski M, Patzak A, Persson PB. Constriction of the vasa recta,
the vessels supplying the area at risk for acute kidney injury, by four
different iodinated contrast media, evaluating ionic, nonionic, monomeric and
dimeric agents. Invest Radiol. 2010;45(8):453-7.
http://dx.doi.org/10.1097/RLI.0b013e3181d77eed
https://doi.org/10.1097/RLI.0b013e3181d7...
,1919 Liu ZZ, Viegas VU, Perlewitz A, Lai EY, Persson PB, Patzak A et al.
Iodinated contrast media differentially affect afferent and efferent arteriolar
tone and reactivity in mice: a possible explanation for reduced glomerular
filtration rate. Radiology. 2012;265(3):762-71.
http://dx.doi.org/10.1148/radiol.12120044
https://doi.org/10.1148/radiol.12120044...
,2020 Seeliger E, Flemming B, Wronski T, Ladwig M, Arakelyan K, Godes M et
al. Viscosity of contrast media perturbs renal hemodynamics. J Am Soc Nephrol.
2007;18(11):2912-20. http://dx.doi.org/10.1681/ASN.2006111216
https://doi.org/10.1681/ASN.2006111216...
.
Extraluminal inside the chamber
The experimental chamber was filled with PSS and warmed up to 37.0°C. The vessels were exposed to an initial intraluminal pressure of 80 mmHg.
Model of SAH: Fresh blood (2 ml) was collected through laparotomy and sectioning of the renal artery, and deposited into the experimental chamber (0.5 ml in each corner) of a perfusion myograph (model 110P, DMT, Aarhus Denmark). The blood was left to coagulate for 40 minutes by room temperature, during which suitable brain vessels were isolated and prepared for perfusion. The experimental chamber was then filled with the PSS, and the arteries were mounted onto the glass cannulas. There was no contact between the blood clot and the arteries.
Measurement of the vessel diameter and quantification of the myogenic response
The procedure for mounting of the artery, intraluminal pressure manipulation as well as measurement of vessel diameters was in accordance to the principles of investigating of myogenic responses in pressurized arteries2121 Schubert R. Isolated vessels. In: Dhein S, Mohr FW, Delmar M. Practical methods in cardiovascular research. Berlin: Heidelberg; 2005. p. 198-211.. Arterial diameter was recorded in a continuous manner over time using an acquisition system consisting of a video camera assembled on an inverted microscope and connected to a software for automatic vessel diameter measurement (IonWizard 6.1, IonOptics, Milton, MA, USA) (Figure 1). Right after mounting of superior cerebellar arteries on glass pipets, continuous diameter measurement was started, and all vessels underwent a period of stabilization of 1 hour during which the development of myogenic tone was monitored. Only arteries which developed typical spontaneous myogenic tone – for cerebral vessels more than 20% of constriction – were included into the study. The value of the myogenic tone was expressed as the percentage of the vessel diameter at the end of stabilization time in relation to the diameter in the maximal dilated state. After recording of baseline diameter measurements, the intraluminal pressure was changed in a controlled manner in 4 steps (each of 5 minutes): 1 step – from 80 to 40 mmHg; 2 step – from 40 to 80 mmHg; 3 step – from 80 to 120 mmHg; and 4 step – from 120 to 80 mmHg. The myogenic response was quantified in micrometers (µm) as the difference between the diameter immediately preceding the pressure step and the diameter measured 5 minutes following the pressure step, when the vessel diameter is stable. All diameter values were measured at the external border of the vessel wall. Figure 2 shows a representative tracing of a typical experiment, where the protocol steps are graphically depicted.
Representative pictures of pressurized superior cerebellar arteries during experiments using an acquisition system consisting of a video system and digital imaging. The rectangle delimits the range to be analysed by the software performing automatic diameter measurement over time. Vertical lines show the vessel borders detected in real time. The tip of the glass cannulas inside of the vessel is indicated with an arrow at the bottom of the picture. (A) Development of normal spontaneous myogenic tone; (B) Development of spastic spontaneous myogenic tone in presence of the coagulated blood (volume 2 ml).
Representative tracing taken out of a control experiment, showing continuous measurement of vessel diameter over time (lower tracing) along with the changes in intraluminal pressure (upper tracing). Development of spontaneous myogenic tone can be observed during stable pressure of 80 mmHg. The myogenic response is shown during controlled 5 minutes-stepwise changes in the intraluminal pressure. The tracing of diameter was graphically improved for better visualization in black/white printing (text, width of tracing, saturation and contrast), without influencing the actual values of measurement.
Statistical analysis
Only one artery was used from each rat for each experiment. Calculation of power was previously performed to determine the optimal sample size. The IBM SPSS Statistics 22 software was used for statistical comparisons. Statistical significance was considered for p-value smaller than 0.05.
Data from spontaneous myogenic tone were reported in the text and in Figure 3 as average and standard error of the means (SEM). Two-way/repeated measurements ANOVA was used to compare groups for spontaneous myogenic tone. Bonferroni method was used as correction for multiple comparisons. Where ANOVA pointed to differences in myogenic tone between groups, Tukey HSD test was used as a post hoc test to compare groups pairwise.
Development of spontaneous myogenic tone during stable intraluminal pressure of 80 mmHg. The data are presented as an average ± SEM. CM: Contrast medium. * indicates a significant difference between curves for groups treated with coagulated blood (volume 2 ml) and without blood, respectively.
Data from the myogenic response were reported in the text as medians (with 25th and 75th percentiles), and in the Figure 4 as box-plots. The myogenic response steps among all four groups were first compared with the Kruskal-Wallis test. Where differences among groups were detected, we used the Mann-Whitney-test to identify inter-group differences pairwise.
Myogenic response quantified as the variation in diameter after controlled changes in intraluminal pressure. CM – contrast medium. (A) Dilation in response to decrease of intraluminal pressure from 80 to 40 mmHg; (B) Constriction in response to increase of intraluminal pressure from 40 to 80 mmHg; (C) Constriction in response to increase of intraluminal pressure from 80 to120 mmHg; and (D) Dilation in response to decrease of intraluminal pressure from 120 to 80 mmHg. * indicates a significant difference between groups. Non-significant differences between groups are also indicated (n.s.).
RESULTS
Spontaneous myogenic tone
Two-way/repeated measurements ANOVA followed by Tukey HSD test showed that exposure to blood significantly influenced the development of myogenic tone over time (p = 0.000002), while CM did not (p = 0.423). Vessels treated with blood developed a more pronounced myogenic tone compared to control groups:
-
Vessels treated with blood clot alone had a final diameter of 65.7 ± 2.0% of maximal diameter after stabilization time, compared to 77.1 ± 1.2% of the control group (average ± SEM, p = 0.00001);
-
Vessels exposed to CM and blood clot together had a final diameter of 62.1 ± 2.1% of maximal diameter, compared to 77.2 ± 1.7% of the CM group (average ± SEM, p = 0.00024).
Myogenic response
There were statistically significant differences between the experimental groups in all four steps of the myogenic response measurement (Kruskal-Wallis test, p < 0.05). Figure 4 shows the magnitude of variation in vessel diameter in response to controlled changes in intraluminal pressure, as well as which experimental groups differed from another in each step of the protocol (Mann-Whitney-test). Exposition to blood alone impaired the myogenic response in all steps of pressure. CM alone did not influence the myogenic response in comparison to the control group. In the groups exposed to blood, CM influenced the myogenic response only in the third step of the protocol (80 to 120 mmHg) when compared to blood alone.
In the control group, the change of intraluminal pressure from 80 to 40 mmHg dilated vessels by 11.9 µm (25th and 75th percentiles, 8.2 µm and 16.5 µm, respectively), while the change from 40 to 80 mmHg constricted vessels by -13 µm (-19 µm, -7.7 µm). Increasing the intraluminal pressure from 80 to 120 mmHg changed the diameter by 1.4 µm (-1.8 µm, 4 µm). Decreasing the intraluminal pressure from 120 to 80 mmHg dilated vessels by 0.6 µm (-2.9 µm, 4.2 µm) (Figure 4).
CM alone did not significantly change the myogenic response (80-40 mmHg: 9.1 µm, 6.2 µm, 10.8 µm, p = 0.28; 40-80 mmHg: -9.3 µm, -13.1 µm, -7.1 µm, p = 0.24; 80-120 mmHg: -0.1 µm, -4.1 µm, 4 µm, p = 0.84; 120-80 mmHg: 1.7 µm, -2.8 µm, 4.3 µm, p = 0.89) compared to the control group, respectively (Figure 4).
Vessels treated with blood showed a significant decrease of both the dilatory and the constrictor myogenic response (80-40 mmHg: -3.3 µm, -7.9 µm, -1.9 µm, p = 0.00004; 40-80 mmHg: 1.7 µm, 0.5 µm, 3 µm, p = 0.0002; 80-120 mmHg: 10.9 µm, 7 µm, 18 µm, p = 0.0006; 120-80 mmHg: -6.4 µm, -23.1 µm, -2.5 µm, p = 0.008) in comparison to the control group, respectively (Figure 4).
Vessels treated with blood and CM together showed a significant decrease of the first and second steps of the myogenic response (80-40 mmHg: -3.3 µm, -4.3 µm, -0.6 µm, p = 0.0014; 40-80 mmHg: -1.1 µm, -1.4 µm, 0.4 µm, p = 0.0014; 80-120 mmHg: 1.1 µm, -1.3 µm, 2.5 µm, p = 0.93; 120-80 mmHg: -1.6 µm, -3.1 µm, 0 µm, p = 0.33) in comparison to CM alone, respectively (Figure 4).
The myogenic response differed between vessels treated with blood and CM together compared to blood alone only at the third step of pressure (80-40 mmHg: p = 0.55; 40-80 mmHg: p = 0.072; 80-120 mmHg: p = 0.0032; 120-80 mmHg: p = 0.099; Figure 4).
DISCUSSION
The focus of our study was to assess the effect of a contemporary, widely used CM on the myogenic response of spastic cerebral vessels. A novel in vitro model was developed to simulate vasospasm post SAH. It consisted of deploying a controlled amount of blood clot in the experimental chamber without mechanical interaction with the vessel.
The mechanisms of vasospasm post SAH have been investigated using different models.
There are in vivo and in vitro approaches. The
most common in vivo techniques are: injection of blood into the
brain cisternae and vessel avulsion2222 Brunner E, Puri ML. Nonparametric methods in factorial designs. Stat
Papers. 2001;42(1):1-52.
http://dx.doi.org/10.1007/s003620000039
https://doi.org/10.1007/s003620000039...
,2323 Crowley RW, Medel R, Kassell NF, Dumont AS. New insights into the
causes and therapy of cerebral vasospasm following subarachnoid hemorrhage. Drug
Discov Today. 2008;13:254-60.
http://dx.doi.org/10.1016/j.drudis.2007.11.010
https://doi.org/10.1016/j.drudis.2007.11...
. Some investigators placed blood clots into the brain33 Titova E, Ostrowski RP, Zhang JH, Tang J. Experimental models of
subarachnoid hemorrhage for studies of cerebral vasospasm. Neurol Res.
2009;31(6):568-81. http://dx.doi.org/10.1179/174313209X382412
https://doi.org/10.1179/174313209X382412...
,66 Marbacher S, Fandino J, Kitchen ND. Standard intracranial in vivo
animal models of delayed cerebral vasospasm. Br J Neurosurg. 2010;24(4):415-34.
http://dx.doi.org/10.3109/02688691003746274
https://doi.org/10.3109/0268869100374627...
. In vitro models include
application of whole blood88 Simeone FA, Vinall P. Mechanisms of contractile response of cerebral
artery to externally-applied fresh blood. J Neurosurg. 1975;43(1):37-47.
http://dx.doi.org/10.3171/jns.1975.43.1.0037
https://doi.org/10.3171/jns.1975.43.1.00...
,99 Linder M, Alksne JF. Prevention of persistent cerebral smooth muscle
contraction in response to whole blood. Stroke. 1978;9(5):472-7.
http://dx.doi.org/10.1161/01.STR.9.5.472
https://doi.org/10.1161/01.STR.9.5.472...
or of vasoactive substances which are hypothetically
involved in the development of vasospasm1818 Seker F, Hesser J, Neumaier-Probst E, Groden C, Brockmann MA,
Schubert R et al. Dose-response relationship of locally applied nimodipine in an
ex vivo model of cerebral vasospasm. Neuroradiology. 2013;55(1):71-6.
http://dx.doi.org/10.1007/s00234-012-1079-8
https://doi.org/10.1007/s00234-012-1079-...
into the organ bath solution.
In our experience models of SAH using whole blood88 Simeone FA, Vinall P. Mechanisms of contractile response of cerebral
artery to externally-applied fresh blood. J Neurosurg. 1975;43(1):37-47.
http://dx.doi.org/10.3171/jns.1975.43.1.0037
https://doi.org/10.3171/jns.1975.43.1.00...
,99 Linder M, Alksne JF. Prevention of persistent cerebral smooth muscle
contraction in response to whole blood. Stroke. 1978;9(5):472-7.
http://dx.doi.org/10.1161/01.STR.9.5.472
https://doi.org/10.1161/01.STR.9.5.472...
were not suitable for the investigation of spontaneous
myogenic tone and myogenic response, primarily because whole blood hinders the
visualization of pressurized arteries. The use of coagulated blood does not muddle
the solution and allow the measurement of vessel diameter. It is possible to use
coagulated blood of different ages, over longer periods of time. Importantly, we can
control the exact proportion between the volume of the blood clot and PSS
surrounding the vessel, and avoid the effects of irregular distribution of blood
around the brain cisterns. By careful and controlled isolation of each vessel we can
also exclude that vessel dysfunction happens due to mechanical damage by bleeding.
Although mechanical irritation of vessels or brain damage are considered as possible
contributing factors44 Athar MK, Levine JM. Treatment options for cerebral vasospasm in
aneurysmal subarachnoid hemorrhage. Neurotherapeutics. 2012;9(1):37-43.
http://dx.doi.org/10.1007/s13311-011-0098-1
https://doi.org/10.1007/s13311-011-0098-...
,88 Simeone FA, Vinall P. Mechanisms of contractile response of cerebral
artery to externally-applied fresh blood. J Neurosurg. 1975;43(1):37-47.
http://dx.doi.org/10.3171/jns.1975.43.1.0037
https://doi.org/10.3171/jns.1975.43.1.00...
,2424 Zheng M, Zhu H, Gong Y, Wang D, Xie Q, Tang H et al. Involvement of
GMRP1, a novel mediator of Akt pathway, in brain damage after intracerebral
hemorrhage. Int J Clin Exp Pathol. 2013;6(2):224-9.,2525 Koide M, Sukhotinsky I, Ayata C, Wellman GC. Subarachnoid
hemorrhage, spreading depolarizations and impaired neurovascular coupling.
Stroke Res Treat. 2013;2013:ID819340.
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https://doi.org/10.1155/2013/819340...
to clinical vasospasm, in our study we intended to
separate the mechanical effects from the effects of blood clot presence and
ageing.
We found that exposition to coagulated blood significantly increases the spontaneous
myogenic tone of cerebral arteries. This indicates that our in vitro
model successfully reproduces changes in the vessel tone which correspond
to the initial events of vasospasm post SAH in vivo. The data
support the assumption that the causal agents of vascular spasm originate largely
from the clotted blood2323 Crowley RW, Medel R, Kassell NF, Dumont AS. New insights into the
causes and therapy of cerebral vasospasm following subarachnoid hemorrhage. Drug
Discov Today. 2008;13:254-60.
http://dx.doi.org/10.1016/j.drudis.2007.11.010
https://doi.org/10.1016/j.drudis.2007.11...
. We thus
believe that the use of coagulated blood immersed in PSS provides a nearer
approximation of the environmental conditions in the brain cisterns following SAH in
comparison to the models using either whole blood or individual
vasoconstrictors.
Cerebral vessels showed an impaired myogenic response in our model of vasospasm. This
observation supports clinical evidences that the autoregulation of cerebral blood
flow is disturbed after SAH, what may contribute to brain damage2525 Koide M, Sukhotinsky I, Ayata C, Wellman GC. Subarachnoid
hemorrhage, spreading depolarizations and impaired neurovascular coupling.
Stroke Res Treat. 2013;2013:ID819340.
http://dx.doi.org/10.1155/2013/819340
https://doi.org/10.1155/2013/819340...
. It has been shown that
pressurized arteries from rabbits where SAH had been induced in
vivo have enhanced myogenic response2626 Ishiguro M, Puryear CB, Bisson E, Saundry CM, Nathan DJ, Russell SR
et al. Enhanced myogenic tone in cerebral arteries from a rabbit model of
subarachnoid hemorrhage. Am J Physiol Heart Circ Physiol. 2002;283(6):H2217-25.
http://dx.doi.org/10.1152/ajpheart.00629.2002
https://doi.org/10.1152/ajpheart.00629.2...
. However, in this study the myogenic response was
reversed in both control and spastic vessels when the intraluminal pressure was
increased to what the authors considered as supraphysiological levels (i.e., above
140 mmHg)2626 Ishiguro M, Puryear CB, Bisson E, Saundry CM, Nathan DJ, Russell SR
et al. Enhanced myogenic tone in cerebral arteries from a rabbit model of
subarachnoid hemorrhage. Am J Physiol Heart Circ Physiol. 2002;283(6):H2217-25.
http://dx.doi.org/10.1152/ajpheart.00629.2002
https://doi.org/10.1152/ajpheart.00629.2...
. In contrast, in our
experiments only the vessels exposed to blood clot showed an impaired myogenic
response, and in all levels of pressure. These apparently contradictory findings may
result from the use of different models of vasospasm, different time points for
investigating the myogenic response during the development of vasospasm, and
different protocols for quantifying the myogenic response.
We found out that CM did not significantly influence vessel tone and did not
negatively influence the myogenic response, in both healthy as well as in spastic
vessels. This is important because patients with SAH have disturbances of cerebral
blood regulation2525 Koide M, Sukhotinsky I, Ayata C, Wellman GC. Subarachnoid
hemorrhage, spreading depolarizations and impaired neurovascular coupling.
Stroke Res Treat. 2013;2013:ID819340.
http://dx.doi.org/10.1155/2013/819340
https://doi.org/10.1155/2013/819340...
, and many
diagnostic and therapeutic procedures needed for their treatment may require the use
of CM1212 Kellner P, Stoevesandt D, Soukup J, Bucher M, Raspé C.
Aneurysmatisch bedingte Subarachnoidalblutung. Anaesthesist. 2012;61(9):792-814.
http://dx.doi.org/10.1007/s00101-012-2077-2
https://doi.org/10.1007/s00101-012-2077-...
,1313 Seibert B, Tummala RP, Chow R, Faridar A, Mousavi SA, Divani AA.
Intracranial aneurysms: review of current treatment options and outcomes. Front
Neurol. 2011;2:45. http://dx.doi.org/10.3389/fneur.2011.00045
https://doi.org/10.3389/fneur.2011.00045...
,1414 Keyrouz SG, Diringer MN. Clinical review: prevention and therapy of
vasospasm in subarachnoid hemorrhage. Crit Care. 2007;11(4):220.
http://dx.doi.org/10.1186/cc5958
https://doi.org/10.1186/cc5958...
. It has been shown that several types of CM may
have potentially deleterious effects on the tone and reactivity of vessels from
several vascular beds1515 Sendeski M, Patzak A, Persson PB. Constriction of the vasa recta,
the vessels supplying the area at risk for acute kidney injury, by four
different iodinated contrast media, evaluating ionic, nonionic, monomeric and
dimeric agents. Invest Radiol. 2010;45(8):453-7.
http://dx.doi.org/10.1097/RLI.0b013e3181d77eed
https://doi.org/10.1097/RLI.0b013e3181d7...
,1616 Sendeski MM. Pathophysiology of renal tissue damage by iodinated
contrast media. Clin Exp Pharmacol Physiol. 2011;38(5):292-9.
http://dx.doi.org/10.1111/j.1440-1681.2011.05503.x
https://doi.org/10.1111/j.1440-1681.2011...
. Correspondingly, there are evidences that CM affect
regional cerebral blood flow in healthy subjects1717 Rosengarten B, Steen Müeller MK, Müeller A, Traupe H, Voss
RK, Kaps M. Contrast media effect on cerebral blood flow regulation after
performance of cerebral or coronary angiography. Cerebrovasc Dis.
2003;16(1):42-6. http://dx.doi.org/10.1159/000070114
https://doi.org/10.1159/000070114...
. Interestingly, Rosengarten et al.1717 Rosengarten B, Steen Müeller MK, Müeller A, Traupe H, Voss
RK, Kaps M. Contrast media effect on cerebral blood flow regulation after
performance of cerebral or coronary angiography. Cerebrovasc Dis.
2003;16(1):42-6. http://dx.doi.org/10.1159/000070114
https://doi.org/10.1159/000070114...
showed that the dynamic cerebral
blood flow regulation – the increase of regional cerebral blood flow caused
by brain activity – was negatively affected by CM, while stable regional
brain blood flow was not affected. We think that these results are compatible with
our findings, given that the stable regional blood flow is directly dependent on the
myogenic response. Although our results do not show statistical differences for
vessels treated with blood clot and CM, we have to consider a small number of
samples and multiple comparisons. Moreover, when translating the current findings
into in vivo condition, we can meet various limitations.
Interestingly, we found that vessels exposed to blood clot and CM showed a lower
degree of functional impairment in comparison to vessels exposed to blood clot
alone. A possible explanation for this finding could be endothelial damage induced
by the CM, with consequent decreased nitric oxide release and increased superoxide
production1515 Sendeski M, Patzak A, Persson PB. Constriction of the vasa recta,
the vessels supplying the area at risk for acute kidney injury, by four
different iodinated contrast media, evaluating ionic, nonionic, monomeric and
dimeric agents. Invest Radiol. 2010;45(8):453-7.
http://dx.doi.org/10.1097/RLI.0b013e3181d77eed
https://doi.org/10.1097/RLI.0b013e3181d7...
,2727 Sendeski MM, Persson AB, Liu ZZ, Busch JF, Weikert S, Persson PB et
al. Iodinated contrast media cause endothelial damage leading to
vasoconstriction of human and rat vasa recta. Am J Physiol Renal Physiol.
2012;303(12):F1592-8.
http://dx.doi.org/10.1152/ajprenal.00471.2012
https://doi.org/10.1152/ajprenal.00471.2...
. Although the influence of the
endothelium on the myogenic response is usually not marked, some experimental models
show that the myogenic response of cerebral arteries might be modulated by the
endothelium1010 Schubert R, Mulvany M. The myogenic response: established facts and
attractive hypotheses. Clin Sci. 1999;96(4):313-26.
http://dx.doi.org/10.1042/CS19980403
https://doi.org/10.1042/CS19980403...
.
In summary, we developed a novel, reproducible in vitro model of vasospasm post SAH which is adequate to investigate cerebral autoregulation. Our finding that the myogenic response was deranged in our model is compatible with clinical studies showing that the autoregulation of cerebral blood flow is impaired after SAH. There was no negative influence of CM on myogenic tone and myogenic response in cerebral vessels with acute vasospasm. The influence of CM on other mechanisms of regulation of cerebral blood flow in patients with vasospasm and SAH is still unknown, and warrants further investigation using other types of models.
Acknowledgements
We thank A. Gerhardt for the technical assistance during our experiments.
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» https://doi.org/10.1155/2013/819340 -
26Ishiguro M, Puryear CB, Bisson E, Saundry CM, Nathan DJ, Russell SR et al. Enhanced myogenic tone in cerebral arteries from a rabbit model of subarachnoid hemorrhage. Am J Physiol Heart Circ Physiol. 2002;283(6):H2217-25. http://dx.doi.org/10.1152/ajpheart.00629.2002
» https://doi.org/10.1152/ajpheart.00629.2002 -
27Sendeski MM, Persson AB, Liu ZZ, Busch JF, Weikert S, Persson PB et al. Iodinated contrast media cause endothelial damage leading to vasoconstriction of human and rat vasa recta. Am J Physiol Renal Physiol. 2012;303(12):F1592-8. http://dx.doi.org/10.1152/ajprenal.00471.2012
» https://doi.org/10.1152/ajprenal.00471.2012
-
Support: This work was supported by grants from the Deutsche Forschungsgemeinschaft (FG1368, PA479/10-1).
Publication Dates
-
Publication in this collection
Feb 2015
History
-
Received
20 May 2014 -
Reviewed
22 Oct 2014 -
Accepted
10 Nov 2014