The cerebral embolism evoked by intra-arterial delivery of allogeneic bone marrow mesenchymal stem cells in rats is related to cell dose and infusion velocity
© Cui et al.; licensee BioMed Central. 2015
Received: 17 September 2014
Accepted: 27 January 2015
Published: 27 January 2015
Intra-arterial cell infusion is an efficient delivery route with which to target organs such as the ischemic brain. However, adverse events including microembolisms and decreased cerebral blood flow were recently reported after intra-arterial cell delivery in rodent models, raising safety concerns. We tested the hypothesis that cell dose, infusion volume, and velocity would be related to the severity of complications after intra-arterial cell delivery.
In this study, 38 rats were subjected to a sham middle cerebral artery occlusion (sham-MCAO) procedure before being infused with allogeneic bone-marrow mesenchymal stem cells at different cell doses (0 to 1.0 × 106), infusion volumes (0.5 to 1.0 ml), and infusion times (3 to 6 minutes). An additional group (n = 4) was infused with 1.0 × 106 cells labeled with iron oxide for in vivo tracking of cells. Cells were infused through the external carotid artery under laser Doppler flowmetry monitoring 48 hours after sham-MCAO. Magnetic resonance imaging (MRI) was performed 24 hours after cell infusion to reveal cerebral embolisms or hemorrhage. Limb placing, cylinder, and open field tests were conducted to assess sensorimotor functions before the rats were perfused for histology.
A cell dose-related reduction in cerebral blood flow was noted, as well as an increase in embolic events and concomitant lesion size, and sensorimotor impairment. In addition, a low infusion velocity (0.5 ml/6 minutes) was associated with high rate of complications. Lesions on MRI were confirmed with histology and corresponded to necrotic cell loss and blood-brain barrier leakage.
Particularly cell dose but also infusion velocity contribute to complications encountered after intra-arterial cell transplantation. This should be considered before planning efficacy studies in rats and, potentially, in patients with stroke.
Stroke is one of the leading causes of death and chronic disability in adults in the industrialized countries. Only limited treatment options are available in the acute phase of stroke. Thrombolysis is the only established treatment, but is hampered by the narrow time window of 4.5 hours and very strict indications , thus leaving more than 90% of patients untreated.
Cell-based therapy is a promising experimental approach to enhance poststroke recovery. Positive treatment effects have been seen in stroke models by using different sources of cells and different delivery routes . In particular, mesenchymal stem cells (MSCs) are safely and readily obtainable [3, 4]. Several delivery routes are available, but the intravenous transplantation technique is the most commonly used in both preclinical and clinical trials [5–8]. However, the current treatment strategies are far from optimal. For example, most of the infused cells are rapidly trapped in the lung, followed by their relocation to the internal organs [8, 9]. The pulmonary circulation can be circumvented by giving an intra-arterial infusion to increase the cell homing to the ischemic hemisphere, which has been claimed to enhance therapeutic outcome [10–12]. However, some adverse events related to intra-arterial cell infusion, such as micro-occlusions, have been reported [12, 13], raising safety concerns. Therefore, a careful optimization of the intra-arterial infusion procedures is needed before efficacy studies.
The complications encountered after intra-arterial stem cell transplantation seem to depend, to some extent at least, on the infusion technique, cell size, and infusion velocity [14, 15]. Janowski et al.  proposed that cell size and infusion velocity would be major determinants of micro-occlusion after intra-arterial cell injection, whereas cell dose should be adjusted when using different types of cells. In this study, we hypothesized that (a) complications of intra-arterial cell delivery would be dose dependent (that is, a lower cell dose would be safer for cell delivery); and (b) complications would be related to both infusion volume and velocity (that is, extending the infusion volume or time might mitigate some of the complications). A safety assessment was performed with laser Doppler flowmetry (LDF), magnetic resonance imaging (MRI), behavioral testing, and histology.
Forty-two adult male RccHan:Wistar rats (249 to 306 g; Laboratory Animal Centre, Kuopio, Finland) were maintained in a controlled environment (temperature, 20°C ± 1°C; humidity, 50% to 60%; light period, 07:00 to 19:00), with free access to food (2016S, Teklad) and water throughout the experiment. Animal care procedures were conducted according to the guidelines set by the European Community Council Directives 86/609/EEC, and this work was approved by the Animal Ethics Committee (Hämeenlinna, Finland).
Preparation and characterization of rat bone marrow mesenchymal stem cells for transplantation
Oricell™ male Wistar rat bone marrow mesenchymal stem cells (BMMSCs; Cyagen Biosciences, Inc., Sunnyvale, CA, USA; Cat. No. RAWMX-01001, passage 2) were cultured according to the manufacturer’s instructions in OriCell MSC growth medium supplemented with 10% fetal bovine serum, 1% glutamine, and 1% penicillin-streptomycin (all reagents from Cyagen Biosciences Inc., Cat. No. GUXMX-90011). The medium was changed twice weekly, and cells were passaged when subconfluent (80% to 90% confluence). Rat BMMSCs (p5) were cryopreserved in the OriCell™ NCR cryopreservation medium (Cyagen Biosciences Inc., Cat.No. NCPF-10001). The cryopreserved cells were thawed in a water bath at 37°C before being decanted into the thawing medium containing α-MEM (Life Technologies Ltd., Cat. No. 41061-029) and 10% human serum albumin (octapharma, albunorm™). The cells were centrifuged, and medium was removed. The cells were then resuspended in phosphate-buffered saline (PBS), and trypan blue staining was used to determine cell viability and number by Countess™ automated cell counter (Invitrogen, Cat.No. C10281). For in vivo MRI tracking of transplanted cells, cells were incubated overnight with 25 μg/ml Molday ION Rhodamine B (BioPAL, CL-50Q02-6A-50), a superparamagnetic iron oxide formulation. The labeling efficiency was confirmed by Zeiss Axio inverted fluorescent microscope (Vert.A1).
Intra-arterial cell transplantation
Forty-eight hours after the sham-operation, rats were infused with different doses of rat BMMSCs (0.25 × 106, 0.5 × 106, and 1.0 × 106; n = 6 per group) in 0.5 ml PBS during 3 minutes through the stump of the ECA with the blood flow maintained in the ICA. Control subjects (n = 8) were infused with 0.5 ml PBS. The infusion needle was removed after transplantation, and the ECA stump was electrocoagulated. An additional group of rats (n = 4) was infused with 1.0 × 106 iron-labeled cells in 0.5 ml PBS within 3 minutes before MRI tracking. To explore the effects of infusion volume and velocity, 0.5 × 106 cells were infused in 0.5 ml over either 3 minutes or 6 minutes, and in 1.0 ml over either 3 minutes or 6 minutes (n = 4 per group).
Monitoring of cerebral blood flow with laser Doppler flowmetry
A PeriFlux System 4000 (Perimed, Sweden) with probe 407 was used to monitor the local cerebral blood flow (CBF). Before cell transplantation, an incision was made to expose the skull. The probe was placed above the sensorimotor cortex (1 mm posterior, 3 mm lateral to bregma). CBF signals were recorded starting 5 minutes before cell infusion and subsequently continuing for 30 minutes. Mean values of signal were measured before cell infusion (baseline), during cell infusion, and in 5-minute periods during 30 minutes of follow-up after cell infusion. CBF signal changes were expressed relative to baseline. The laser Doppler signal was recorded and analyzed by using PeriSoft for Windows 2.50. Area under the curve (AUC) was calculated to reveal the overall CBF changes.
The limb-placing, cylinder, and open field tests were conducted in a blinded manner before sham-operation and 24 hours after cell transplantation to detect possible behavioral deficits related to cell infusion.
A limb-placing test was used to assess the fore- and hindlimb responses to tactile and proprioceptive stimulation [16, 17]. The test contained seven limb-placing tasks, which were scored as follows: 2 points, the rat performed normally; 1 point, the rat performed with a delay (>2 s) and/or incompletely, and 0 points, no response.
The open field test was used to measure locomotor activity under dimmed lighting conditions to avoid the inhibitory effect of light . The open field apparatus consisted of a circular arena surrounded by a 25 cm high wall. The location and movement of the experimental animal were recorded by an infrared-sensitive video camera-computer linkup. The field was divided into eight preprogrammed areas. The test lasted 10 minutes. The rat was considered moving, if the velocity was more than 1.5 cm/s. EthoVision XT 7.0 (Noldus, The Netherlands) was used to record and analyze the data.
Magnetic resonance imaging
MRI was performed 24 hours after cell transplantation by using a Bruker 9.4 T horizontal scanner to detect micro-occlusions or hemorrhages. The rats were anesthetized with 2% to 2.5% isoflurane (5% for induction) in a gas mixture of 30% O2/70% N2, delivered via a nose mask. A RARE sequence with the following parameters was used to acquire T2-weighted images: repetition time (TR) = 3.0 s, echo time (TE) = 32 ms, average = 16, matrix size of 256 × 128, field-of-view (FOV) = 30 mm × 30 mm; 15 slices with 1-mm slice thickness. T2*-weighted multislice images were acquired with the following parameters: TR = 750 ms, TE = 3.0 ms, TE2 = 6.0 ms, average = 6, FOV = 25.6 mm × 25.6 mm, 15 slices with 1-mm slice thickness. Lesion volumes were analyzed with MATLAB R2012a, Aedes 1.0. MRI images were also scored by using the following semiquantitative scaling: 0 point, no lesions; 1 point, one to five focal lesions (≤2 mm); 2 points, five to 10 focal lesions; 3 points, more than 10 focal lesions or confluent lesions.
One day after MRI, the rats were perfused with 0.9% NaCl followed by 4% paraformaldehyde in 0.1 M phosphate buffer (PB) (pH 7.4). The brains were carefully removed and postfixed in 4% paraformaldehyde overnight, and then kept in 30% sucrose in 0.1 M PB for 5 days. Brain sections (35 μm) were cut by using a sliding microtome, with the sections being stored in antifreeze solution at -20°C.
Nissl staining and modified Gallyas silver staining  were used to detect lesions and to visualize degenerating terminals and cell bodies in sections matched with MRI images.
IgG staining was used to assess the blood-brain barrier leakage . The sections were washed in PB 3 times, incubated in 1% H2O2 for 15 minutes, blocked in 2% normal goat serum for 2 hours, followed by incubation with biotinylated sheep anti-rat IgG (1:200; AbD Serotec, Oxford, UK) for 48 hours at 4°C. The sections were then rinsed with Tris-buffered saline with 0.5% Triton X-100 and incubated with streptavidin-horseradish peroxidase conjugate (1:1,000; GE Healthcare, UK) for 1 hour, and developed with diaminobenzidine for 4 to 6 minutes.
Prussian blue staining was used to visualize the iron-labeled BMMSCs in the brain . The sections were incubated with 2% potassium ferrocyanide in 2% HCl for 5 minutes and counterstained with neutral red.
All images were captured by using a Zeiss Axio Imager M2 microscope (Carl Zeiss GmbH, Germany), with an AxioCam ER camera.
The analyses were performed with SPSS software (version 19). CBF changes, lesion size, MRI scores, and results from behavioral tests were compared by using a Kruskal-Wallis test followed by a Mann-Whitney test. The Spearman rank correlation coefficient was used to evaluate correlations between lesion size, behavioral results, and cell dose. The level of significance was P <0.05. Data are presented as mean ± standard deviation (SD).
LDF monitoring of cell transplantation
MRI monitoring of embolisms and hemorrhage after cell transplantation
MRI results in rats receiving different cell doses
0.25 × 10 6
0.5 × 10 6
1.0 × 10 6
Rats with micro-occlusions/total
0.13 ± 0.35
0.17 ± 0.41
1.67 ± 0.82**##
2.67 ± 0.82**##
Lesion size (mm3)
0.31 ± 0.88
0.94 ± 1.99
35.87 ± 21.86**##
194.36 ± 165.94**##
MRI results in rats receiving 0.5 × 10 6 cells with different infusion volumes in different time spans
0.5 ml/3 min
0.5 ml/6 min
1.0 ml/3 min
1.0 ml/6 min
Rats with micro-occlusions
1.67 ± 0.82
3.00 ± 0.00
1.50 ± 1.29
2.50 ± 1.00
Lesion size (mm3)
35.87 ± 21.86
197.83 ± 184.30
41.78 ± 38.87
150.35 ± 236.69
Behavioral results after cell transplantation
In groups with different infusion volumes or velocities, the mean limb-placing score of left limbs (10.75 ± 3.95) in 0.5 ml/6-minute group was significantly lower than the mean score (14) in both 0.5 ml/3-minute and 1.0 ml/3-minute group (P <0.05), but not in 1.0 ml/6-minute group (11.25 ± 5.50). No significant differences in the performance in the cylinder or open field tests were found between groups.
Histologic changes after cell transplantation
Tracking of iron-labeled cells
Intra-arterial cell delivery has been postulated to enhance the homing efficiency to the target organ, which may be associated with additional therapeutic benefits, particularly in the brain. However, adverse events after intra-arterial cell delivery, such as micro-occlusions and compromised CBF, were recently reported in rodent models, raising safety concerns. Cell size, infusion velocity, and technique seem to be important determinants of safety [14, 15, 23]. Our study reveals the relation particularly between cell dose and the severity of complications, as detected by LDF, MRI, behavioral testing, and histology.
Lower cell dose is safer for intra-arterial delivery of BMMSCs
In our study, we used ECA for cell transplantation with preserved blood flow in the ICA. Previously, an infusion velocity of 0.2 ml/min or lower has been postulated to be safe for rats ; thus we applied the rate of 0.5 ml/3 minutes to test different cell doses. When PBS was infused at a rate of 0.5 ml/3 minutes, the average LDF signal did not change or slightly increased, probably as a result of hemodynamic changes after the injection of vehicle into the cerebral artery. In contrast, an increasing cell dose evoked a reduction in CBF, which resulted in an increase in the numbers of ischemic lesions, as detected by MRI and sensorimotor function impairment. Therefore, lower cell doses were associated with fewer adverse events. Both MRI, 24 hours, and histology, 48 hours, after infusion revealed microembolisms as being the most likely explanation for the observed CBF decline.
Thrombi formed at damaged endothelium after filament retraction may have caused the minor downstream ischemic lesions occasionally observed in the control group. This would be a technical complication in the filament model that should be taken into account. The size of BMMSCs is relatively large (diameter approximately 20 μm), and thus the cells may be trapped in the cerebral microvessels and cause focal ischemic lesions. Despite attempts to avoid cell aggregation by suspending the cells rigorously before infusion, it is not possible to be sure that single-cell aggregates are not formed before or during the infusion. Those aggregates may also have caused microemboli in some individual cases.
In both scenarios, reducing the cell dose seems to be one way to prevent such events. In the present study, we found a dose of 0.25 × 106 to be safe (that is, the complication rate was similar to that found with controls). Filtering cells before infusion might prevent aggregations, but might also result in a loss of cells. Three-dimensional spheroid cultured MSCs or flow cytometry-based pulse-width assay can also be considered as techniques to reduce or detect cell aggregates in the future [24, 25].
Infusion velocity is closely related to the safety of intra-arterial cell delivery
Our data suggest that increasing the infusion volume (1.0 ml/3 minutes versus 0.5 ml/3 minutes) in an attempt to reduce the cell concentration, did not reduce CBF drop or lesion size. One may speculate that a rapid infusion could affect the hemodynamics, and then trigger endothelial injury, microthrombosis, or forced opening of the blood-brain barrier. Hence, we prolonged the infusion time in an attempt to prevent such adverse events. However, extending the infusion time (0.5 ml/6 minutes versus 0.5 ml/3 minutes) worsened CBF decrease. This may be explained by the higher probability of cell aggregates forming during the prolonged infusion times, which may ultimately result in even greater complications than with rapid infusion.
In line with the LDF results, the MRI score and lesion size seemed to increase in the 0.5 ml/6 minute group, although no significant difference was found, which might be due to the rather small number of animals per group and the extensive variations. Hence, a slower infusion may not be necessarily beneficial despite preventing the hemodynamic complications encountered with high injection velocities. When we extended both infusion volume and infusion time (1.0 ml/6 minutes), CBF was similar to that seen in the 0.5 ml/3 minute group (same net infusion velocity), although with a higher MRI score and a larger lesion, which might be due to the greater variation (Table 2). Thus, infusion velocity, rather than simply infusion volume or infusion time, should be considered to be more responsible for the development of microembolisms after intra-arterial MSC delivery.
Open field test is sensitive at detecting randomly distributed microembolisms
In the present study, microembolisms were found mainly within the ICA territory, but some were also observed in the posterior circulation (brain stem) and occasionally even in the contralateral hemisphere. Given the random distribution of microembolisms and location in the white matter, it was a challenge to find a sensitive behavioral test that could assess possible functional consequences. This was also reflected as an apparent discrepancy in the occurrence of complications in 1.0 × 106 and 0.5 × 106 groups (that is, some of the rats were not found to have any apparent impairment in the limb-placing test or in the cylinder test, despite the presence of MRI lesions). With respect to the open field test, although no significant group difference was found in the rats infused with different doses of cells, which might be due to the high variation between animals, a significant correlation appeared between cell dose and locomotor activity. Therefore, the open field test appears to be the most sensitive technique for detecting a minor, cell dose-related decrease in motor activity [19, 26].
Rapid disappearance of allogeneic BMMSCs after intra-arterial transplantation
Only limited information is available about the intra-arterial delivery of allogeneic cells [9, 14, 27, 28]. Recently Khabbal  reported different clearance rates of rat and human BMMSCs from the brain after intra-arterial infusion, with human BMMSCs disappearing more rapidly than rat cells. However, it is unclear whether the differential cell behavior has any functional impact. Moreover, despite initial effective homing to the brain, both rat and human cells disappeared almost completely within 1 or 2 days [27, 29]. Similarly, the T2* signal extinctions were observed in the brain with MRI at 24 hours after infusion in the present study, but histology at 48 hours after infusion revealed fewer cells in the brain. More important, the brief presence of MSCs was associated with permanent damage with high cell doses.
Thus, one major task for future studies will be to reduce the effective therapeutic dose and to improve engraftment, which should be reflected in functional improvements.
Limitations of the present study
The present study has several limitations. First, only sham-operated rats were used because the microembolisms caused by MSC infusion might be masked by the large corticostriatal lesions typical of most MCAO models. In addition, one cannot exclude the possibility that cells behave differently under postischemic circumstances. Another limitation is that we used the preoperated ECA for cell infusion. It might be possible that reopening the artery releases some blood emboli, causing technical micro-occlusion such as that occasionally observed in the control group. Moreover, because of the random location of lesions, LDF might not be sensitive enough to detect CBF changes in deep white matter and brain structures out of the ICA territory. For the same reason, it was challenging to detect sensorimotor impairment.
Finally, the follow-up period was limited to 3 days (that is, no assessment was made of the long-term outcome). As the observed functional deficits may be transient or minor with respect to the potential therapeutic improvements achieved by MSC, long-term efficacy studies with a safe dose of rat BMMSCs are warranted in stroke rats.
The safety of allogeneic intra-arterial BMMSC transplantation is dose dependent. Infusion velocity is also closely related with safe intra-arterial administration. Therefore, cell dose and infusion velocity should be carefully optimized, according to which cell types are being delivered, as well as to the study design when planning future preclinical and clinical efficacy studies.
Area under curve
bone marrow mesenchymal stem cells
cerebral blood flow
common carotid artery
external carotid artery
field of view
internal carotid artery
laser Doppler flowmetry
middle cerebral artery occlusion
magnetic resonance imaging
mesenchymal stem cell
We thank Ville Juutilainen, Bhimashankar Mitkari, Kristina Kuptsova, Kimmo Jokivarsi, and Mikko Kettunen for their technical assistance with animal care and operations, cell culture, histology, and MRI. This study was supported by Health Research Council of the Academy of Finland and by the MEMS-IRBI ERA-NET research project.
- Del Zoppo GJ, Saver JL, Jauch EC, Adams HP Jr, American Heart Association Stroke Council: Expansion of the time window for treatment of acute ischemic stroke with intravenous tissue plasminogen activator: a science advisory from the American Heart Association/American Stroke Association. Stroke 2009, 40:2945–8. 10.1161/STROKEAHA.109.192535View ArticlePubMed CentralPubMedGoogle Scholar
- Bliss T, Guzman R, Daadi M, Steinberg GK: Cell transplantation therapy for stroke. Stroke. 2007, 38:817–26. 10.1161/01.STR.0000247888.25985.62View ArticlePubMedGoogle Scholar
- Lalu MM, Mclntyre L, Pugliese C, Fergusson D, Winston BW, Marshall JC, et al.: Safety of cell therapy with mesenchymal stromal cells (SafeCell): a systematic review and meta-analysis of clinical trials. PLoS One. 2012, 7:e47559. 10.1371/journal.pone.0047559View ArticlePubMed CentralPubMedGoogle Scholar
- Eckert MA, Vu Q, Xie K, Yu J, Liao W, Cramer SC, et al.: Evidence for high translational potential of mesenchymal stromal cell therapy to improve recovery from ischemic stroke. J Cereb Blood Flow Metab. 2013, 33:1322–34. 10.1038/jcbfm.2013.91View ArticlePubMed CentralPubMedGoogle Scholar
- Bhasin A, Srivastava MV, Mohanty S, Bhatia R, Kumaran SS, Bose S: Stem cell therapy: a clinical trial of stroke. Clin Neurol Neurosurg. 2013, 115:1003–8. 10.1016/j.clineuro.2012.10.015View ArticlePubMedGoogle Scholar
- Lee JS, Hong JM, Moon GJ, Lee PH, Ahn YH, Bang OY, et al.: A long-term follow-up study of intravenous autologous mesenchymal stem cell transplantation in patients with ischemic stroke. Stem Cells. 2010, 28:1099–106. 10.1002/stem.430View ArticlePubMedGoogle Scholar
- Honmou O, Houkin K, Matsunaga T, Niitsu Y, Ishiai S, Onodera R, et al.: Intravenous administration of auto serum-expanded autologous mesenchymal stem cells in stroke. Brain. 2011, 134:1790–807. 10.1093/brain/awr063View ArticlePubMed CentralPubMedGoogle Scholar
- Goldmacher GV, Nasser R, Lee DY, Yigit S, Rosenwasser R, Iacovitti L: Tracking transplanted bone marrow stem cells and their effects in the rat MCAO stroke model. PLoS One. 2013, 8:e60049. 10.1371/journal.pone.0060049View ArticlePubMed CentralPubMedGoogle Scholar
- Rosado-de-Castro PH, Schmidt Fda R, Battistella V, de Souza SAL, Gutfilen B, Goldenberg RC, et al.: Biodistribution of bone marrow mononuclear cells after intra-arterial or intravenous transplantation in subacute stroke patients. Regen Med. 2013, 8:145–55. 10.2217/rme.13.2View ArticlePubMedGoogle Scholar
- Lundberg J, Sodersten E, Sundstrom E, Le Blanc K, Andersson T, Hermanson O, et al.: Targeted intra-arterial transplantation of stem cells to the injured CNS is more effective than intravenous administration: engraftment is dependent on cell type and adhesion molecule expression. Cell Transplant. 2012, 21:333–43. 10.3727/096368911X576036View ArticlePubMedGoogle Scholar
- Misra V, Ritchie MM, Stone LL, Low WC, Janardhan V: Stem cell therapy in ischemic stroke: role of IV and intra-arterial therapy. Neurology. 2012, 79:S207–12. 10.1212/WNL.0b013e31826959d2View ArticlePubMed CentralPubMedGoogle Scholar
- Li L, Jiang Q, Ding G, Zhang L, Zhang ZG, Li Q, et al.: Effects of administration route on migration and distribution of neural progenitor cells transplanted into rats with focal cerebral ischemia, an MRI study. J Cereb Blood Flow Metab. 2010, 30:653–62. 10.1038/jcbfm.2009.238View ArticlePubMed CentralPubMedGoogle Scholar
- Walczak P, Zhang J, Gilad AA, Kedziorek DA, Ruiz-Cabello J, Young RG, et al.: Dual-modality monitoring of targeted intraarterial delivery of mesenchymal stem cells after transient ischemia. Stroke. 2008, 39:1569–74. 10.1161/STROKEAHA.107.502047View ArticlePubMed CentralPubMedGoogle Scholar
- Chua JY, Pendharkar AV, Wang N, Choi R, Andres RH, Gaeta X, et al.: Intra-arterial injection of neural stem cells using a microneedle technique does not cause microembolic strokes. J Cereb Blood Flow Metab. 2011, 31:1263–71. 10.1038/jcbfm.2010.213View ArticlePubMed CentralPubMedGoogle Scholar
- Janowski M, Lyczek A, Engels C, Xu J, Lukomska B, Bulte JW, et al.: Cell size and velocity of injection are major determinants of the safety of intracarotid stem cell transplantation. J Cereb Blood Flow Metab. 2013, 33:921–7. 10.1038/jcbfm.2013.32View ArticlePubMed CentralPubMedGoogle Scholar
- Jolkkonen J, Puurunen K, Rantakomi S, Harkonen A, Haapalinna A, Sivenius J: Behavioral effects of the alpha(2)-adrenoceptor antagonist, atipamezole, after focal cerebral ischemia in rats. Eur J Pharmacol. 2000, 400:211–9. 10.1016/S0014-2999(00)00409-XView ArticlePubMedGoogle Scholar
- Puurunen K, Jolkkonen J, Sirvio J, Haapalinna A, Sivenius J: An alpha (2)-adrenergic antagonist, atipamezole, facilitates behavioral recovery after focal cerebral ischemia in rats. Neuropharmacology. 2001, 40:597–606. 10.1016/S0028-3908(00)00182-9View ArticlePubMedGoogle Scholar
- Karhunen H, Virtanen T, Schallert T, Sivenius J, Jolkkonen J: Forelimb use after focal cerebral ischemia in rats treated with an alpha 2-adrenoceptor antagonist. Pharmacol Biochem Behav. 2003, 74:663–9. 10.1016/S0091-3057(02)01053-5View ArticlePubMedGoogle Scholar
- Roos MW, Ericsson A, Berg M, Sperber GO, Sjoquist M, Meyerson BJ: Functional evaluation of cerebral microembolization in the rat. Brain Res. 2003, 961:15–21. 10.1016/S0006-8993(02)03829-5View ArticlePubMedGoogle Scholar
- Gallyas F, Wolff JR, Bottcher H, Zaborszky L: A reliable and sensitive method to localize terminal degeneration and lysosomes in the central nervous system. Stain Technol. 1980, 55:299–306.PubMedGoogle Scholar
- Hayward NM, Yanev P, Haapasalo A, Miettinen R, Hiltunen M, Grohn O, et al.: Chronic hyperperfusion and angiogenesis follow subacute hypoperfusion in the thalamus of rats with focal cerebral ischemia. J Cereb Blood Flow Metab. 2011, 31:1119–32. 10.1038/jcbfm.2010.202View ArticlePubMed CentralPubMedGoogle Scholar
- Jolkkonen J, Jokivarsi K, Laitinen T, Gröhn O: Subacute hemorrhage and resolution of edema in Rose Bengal stroke model in rats coincides with improved sensorimotor functions. Neurosci Lett. 2007, 428:99–102. 10.1016/j.neulet.2007.09.043View ArticlePubMedGoogle Scholar
- Ge J, Guo L, Wang S, Zhang Y, Cai T, Zhao RC, et al.: The size of mesenchymal stem cells is a significant cause of vascular obstructions and stroke. Stem Cell Rev. 2014, 10:295–303. 10.1007/s12015-013-9492-xView ArticlePubMedGoogle Scholar
- Guo L, Ge J, Zhou Y, Wang S, Zhao RC, Wu Y: Three-dimensional spheroid-cultured mesenchymal stem cells devoid of embolism attenuate brain stroke injury after intra-arterial injection. Stem Cells Dev. 2014, 23:978–89. 10.1089/scd.2013.0338View ArticlePubMed CentralPubMedGoogle Scholar
- Hickerson DH, White HS, Nguyen A, Nieman E, Meadows N, Gentry T, et al.: Development of a flow cytometry-based pulse-width assay for detection of aggregates in cellular therapeutics to be infused by catheter. Cytotherapy. 2014, 16:1545–57. 10.1016/j.jcyt.2014.05.004View ArticlePubMedGoogle Scholar
- Nemeth CL, Shurte MS, McTigue DM, Nemeroff CB, Neigh GN: Microembolism infarcts lead to delayed changes in affective-like behaviors followed by spatial memory impairment. Behav Brain Res. 2012, 234:259–66. 10.1016/j.bbr.2012.06.014View ArticlePubMedGoogle Scholar
- Khabbal J, Kerkela E, Mitkari B, Raki M, Nystedt J, Mikkonen V: Differential clearance of rat and human bone marrow-derived mesenchymal stem cells from the brain after intra-arterial infusion in rats. Cell Transplant 2014. DOI: 10.3727/096368914X679336Google Scholar
- Jiang W, Liang G, Li X, Li Z, Gao X, Feng S, et al.: Intracarotid transplantation of autologous adipose-derived mesenchymal stem cells significantly improves neurological deficits in rats after MCAO. J Mater Sci Mater Med. 2014, 25:1357–66. 10.1007/s10856-014-5157-9View ArticlePubMedGoogle Scholar
- Mitkari B, Kerkela E, Nystedt J, Korhonen M, Mikkonen V, Huhtala T, et al.: Intra-arterial infusion of human bone marrow-derived mesenchymal stem cells results in transient localization in the brain after cerebral ischemia in rats. Exp Neurol. 2013, 239:158–62.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.