- Email: [email protected]
Effect of blood flow on drug release from DES: An experimental study
Letters to the Editor
[7]. However, in 18 chronic heart failure patients, one Japanese group has reported both the peak CO determined by an opticatheter (10.2 ± 2.2 l/min vs. 10.9 ± 2.1 l/min, p b 0.001) to be significantly higher in the treadmill test compared to a bicycle ergometer [9]. In conclusion, Stringer calculated SV and CO are accurate at peak exercise and during recovery. However at peak exercise and at rest the method is of limited accuracy in comparison to oxygen consumption and CW Doppler based USCOM. References [1] Chan JS, Segara D, Nair P. Measurement of cardiac output with noninvasive continuous wave Doppler device versus the pulmonary artery catheter: a comparative study. Crit Care Resuscitation 2006;8(4):309–14. [2] Knobloch K, Lichtenberg A, Winterhalter M, Rossner D, Pichlmaier M, Phillips R. Non-invasive cardiac output determination by twodimensional independent Doppler during and after cardiac surgery. Ann Thorac Surg 2005;80:1479–84.
415
[3] Knobloch K, Hoeltke V, Jakob E, Vogt PM, Phillips R. Non-invasive ultrasonic cardiac output monitoring in exercise testing. Int J Cardiol 2008;126:445–7. [4] Paterson DH, Cunningham DA, Plyley MJ, Blimkie CJR, Donner D. The consistency of cardiac output measurement (CO2 rebreathe) in children during exercise. Eur J Appl Physiol 1982;49:37–44. [5] Siu CW, Tse HF, Lee K, et al. Cardiac resynchronization therapy optimization by ultrasonic cardiac output monitoring (USCOM) device. Pacing Clin Electrophysiol 2007;30(1):50–5. [6] Stringer WW, Hansen JE, Wasserman K. Cardiac output estimated noninvasively from oxygen uptake during exercise. J Appl Physiol 1997;82:908–12. [7] Stromme SB, Ingjer F, Meen HD. Assessment of maximal aerobic power in specifically trained athletes. J Appl Physiol 1977;6:833. [8] Tan HL, Pinder M, Parsons R, Roberts B, van Heerden PV. Clinical evaluation of USCOM ultrasonic cardiac output monitor in cardiac surgical patients in intensive care unit. Br J Anaesth 2005;94(3):287–91. [9] Welsman J, Bywater K, Farr C, Welford D, Armstrong N. Reliability of peak VO2 and maximal cardiac output assessed using thoracic bioimpedance in children. Eur J Appl Physiol 2005;94:228–34.
0167-5273/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2007.07.112
Effect of blood flow on drug release from DES: An experimental study P.R. Umashankar ⁎, P.R. Hari, K. Sreenivasan Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Poojapura, Trivandrum, 695012, India Received 30 June 2007; accepted 6 July 2007 Available online 14 November 2007
Abstract DES has made stenting a successful treatment modality. Still problems exists such as late thrombosis and continued neo-intimal proliferation. Blood flow affects the drug retained in the stent and subsequently on the time frame of vascular healing. To find out drug release kinetics from DES implanted in two different flow conditions, DES were implanted in porcine carotid artery and coronary artery. The drug release kinetics was found out by estimating the drug retained in the stent at different time periods. Through this study it is shown that DES in the coronary artery has a T1/2 of 24 days compared to 2 days in the carotid artery. The difference in T1/2 is attributed to the difference in flow as estimated using Hagen–Poiseuille equation. Evaluation of DES through heterotopic implantation may yield false results due to flow discrepancy. Moreover flow conditions should also be considered while designing the drug matrix to have optimum clinical efficacy. © 2007 Elsevier Ireland Ltd. All rights reserved.
In-stent restenosis, a major problem plaguing stent therapy is targeted by local delivery of antiproliferative, anti-inflammatory, antithrombotic or immunosuppresive ⁎ Corresponding author. Scientist D (Veterinary), Division of In-vivo Models and Testing, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram. Kerala, 695012, India. E-mail address: [email protected] (P.R. Umashankar).
drugs [1]. Metallic coronary stents either alone or with a degradable/non-biodegradable polymer is being used as drug eluting platform for this pharmacological prevention of restenosis. DESs contain single or multilayer biocompatible polymeric coating which ensures drug retention during deployment and modulated drug release kinetics [2]. Currently available DESs are designed to release antirestenotic drugs for at least 3 weeks after the stenting procedure to prevent smooth muscle migration and proliferation [3]. The
416
Letters to the Editor
polymeric formulations are tailored to obtain a sustained release for the stipulated time frame. Drug elution kinetics from DESs are influenced by many factors such as physiochemical properties of the drug, expanded stent configuration [4] degree of cross linking of the polymers, drug solubility and porosity and thickness of the coating [5]. The commercially available DESs are designed to provide sustained release independent of the size of the implanted vessel. To date, as far as these authors know, the influence of the blood flow through stent on the drug release profile is not reported. It can have implication on pre-clinical testing as well as clinical efficacy. In the present study, ‘Infinnium’ Paclitaxel eluting biodegradable polymer coated stents of 4.0 mm diameter and 16 mm length and 3.0 mm diameter and 11 mm length were implanted in the pig carotid artery and coronary artery respectively. In the carotid artery, a total of 15 Paclitaxel eluting stents of sizes 4.0 × 16 mm were deployed, one stent in each animal, at 16 atm pressure to achieve an estimated stent lumen of 4.56 mm. The native vessel overstretch was limited to 30%. The implantation time periods were 3, 7, 15, 30 and 90 days. Three stents were deployed per time period. The amount of Paclitaxel extracted from fresh un-implanted stent of similar size was used as day 0 value. The animals were sacrificed at the end of respective time periods and the Paclitaxel remaining in the stent was extracted with Dicloromethane and estimated using standard method. In the coronary artery, a total of 15 Paclitaxel eluting stents of sizes 3.0 × 11 mm were deployed in the Left anterior descending coronary artery, left circumflex coronary artery or right coronary artery randomly at 6 atm pressure to achieve an estimated stent lumen diameter of 3.0 mm, one stent in each animal. The native artery overstretch was limited to 30%. The implantation time periods were 1, 3, 7, 15 and 30 days. Three stents were deployed per time period. The amount of Paclitaxel extracted from fresh un-implanted stent of similar size was used as day 0 value. The animals were sacrificed at the end of respective time periods and the Paclitaxel remaining in the stent was extracted with Dicloromethane and estimated using standard method. It was apparent that drug release is much faster and T1/2 is attained around 3–4 days from stents implanted in carotid artery. Within a period of 7 days nearly 83% of the incorporated drug is released from the stent. Nearly 90% of the drug is released by 3 weeks of implantation. It is relevant to point out that a sustained release of antirestenotic drug for at least 3 weeks after deployment is required to prevent restenosis. Interestingly, a distinctively altered release pattern of drug from stents implanted in coronary artery was noticed. Here about 25% of the drug was released in the first day. After a week, around 44% of the drug was released. However, between 7 to 30 days period, only an additional 10% drug was released indicating a trend towards the attainment of a plateau phase. Even after 30 days nearly 47% of the drug was remaining in the stents. In this case, the T1/2 appeared to be 24 days. This study vividly point out that release profile of the drug incorporated in drug eluting stents is strongly influenced by the implanted artery, i.e., carotid artery or coronary artery as
the drug matrix is same for both the groups. Structurally both these arteries have similar micro-anatomy [6], except for their estimated diameters. The stented coronary artery had an estimated diameter of 3 mm and that of stented carotid artery was 4.56 mm. Assuming blood as a Newtonian fluid at this flow velocity with around 50 mm Hg pressure at the coronary artery and 100 mm Hg pressure at carotid artery respectively, and applying Hagen–Poiseuille equation to this, it was seen that the blood flow through carotid artery stent is 7.3 times that of the coronary artery stent [7]. This indicates that the relatively faster release of the drug noticed in the carotid artery stents is because of the increased blood flow through it. This can have profound clinical relevance as quicker drug release than the designed period may render the DES ineffective by failing to inhibit neo-intimal proliferation. At the same time prolonged drug retention in the stent can delay intimal healing and endothelialization thereby making it vulnerable for late thrombosis[8,9]. This study also questions the logic of using rabbit iliac artery model for the evaluation of DES compared to pig coronary artery model. Drug retention in the DES will be shorter in the rabbit iliac artery compared to pig coronary artery due to the difference in blood flow through them, even if these arteries have similar diameters and stent length. Due to the difference in the blood pressure experienced at these arteries, the blood flow through the rabbit iliac artery stent will be approximately twice that of the coronary artery stent. The temporal distribution of vessel healing will be affected by the drug retained in the stent and this may be evidenced as quicker healing response in rabbit iliac artery compared to pig coronary artery, for the same DES at similar durations. This animal study warrants that, apart from tailoring the drug containing matrix, blood flow parameters has also to be considered in the designing and evaluation of DES. Acknowledgements The authors wish to acknowledge M/s Sahajanand Medical Technologies Pvt. Ltd, Surat, India for sponsoring the study. The authors appreciate the support given by the Head, BMT wing and the Director, SCTIMST for conducting the study. References [1] Babapulle Mohan N, Eisenberg Mark J. Coated stents for prevention of restenosis: part 1. Circulation 2002;106:2734–40. [2] van der Giessen WJ, Lincoff AM, Schwartz RS, et al. Marked inflammatory sequelae to implantation of biodegradable and nonbiodegradable polymers in porcine coronary arteries. Circulation 1996;94:1690–7. [3] Sousa J Eduardo, Serruys Patrick W, Marco A Costa. New frontiers in cardiology, drug eluting stents: part 1. Circulation 2003;107:2274–9. [4] Hwang Chao-Wei, Wu David, Edelman Elazer R. Physiological transport forces govern drug distribution for stent-based delivery. Circulation 2001;104:600–5. [5] Whelan DM, van Beusekom HM, van der Giessen WJ. Mechanisms of drug loading and release kinetics. Semin interv Cardiol 1998;3:127–31.
Letters to the Editor [6] Kessel Richard G, Kardon Randy H, editors. Tissues and Organs: A Text Atlas of Scanning Electron Microscopy. USA: WH Freeman and Company; 1979. 41–44pp. [7] Nichlas Wilmer W, O'Rourke Michael F Eds, 2005. McDonalds blood flows in arteries- theoretical, experimental and clinical principles, 5th Ed., Hodder Arnold Publications, London. 11 to 48, 321 to 338 pp.
417
[8] Farb Andrew, Burke Allen P, Kolodgie Frank D, Virmani Renu. Pathological mechanisms of fatal late coronary stent thrombosis in humans. Circulation 2003;108:1701–6. [9] Joner Michael, Finn Aloke V, Farb Andrew, et al. Pathology of drugeluting stents in humans-delayed healing and late thrombotic risk. J Am Coll Cardiol 2006;48:193–202.
0167-5273/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2007.07.111
Identification and differentiation of magnetically labeled mesenchymal stem cells in vivo in swines with myocardial infarction Chun-mei Qi, Gen-shan Ma ⁎, Nai-feng Liu, Cheng-xing Shen, Zhong Chen, Xiao-jun Liu, Yao-peng Hu, Xiao-li Zhang, Ji-yuan Chen, Sheng-hong Ju,Yao-liang Tang Received 5 July 2007; accepted 6 July 2007 Available online 11 December 2007
Abstract We aim to track mesenchymal stem cells (MSCs) after magnetically labeling and test the ability of these cells differentiate into cardiomyocytes in vivo. Therefore, 20 swines were divided into four groups, sham-operated group (n = 3); acute myocardial infarction (AMI) transplanted with PBS (n = 3); labeled MSCs (n = 7) and unlabeled MSCs (n = 7) group. 107 labeled or unlabeled cells were intracoronary delivered after MI (4.8 ± 1.3 days), and serial cardiac MR (3.0T) imaging studies were performed at 0, 4 and 8 weeks after transplantation, then the results were confirmed by histological and western blot analysis. We demonstrated that labeled MSCs can be reliably detected and tracked in vivo using MR imaging. In particular, we provided the evidence of regeneration of labeled MSCs in vivo by histological examination and western blot analysis. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Magnetic resonance imaging; Contrast media; Mesenchymal stem cell; Differentiation; Myocardial infarction
1. Results
2. Discussion
MSCs after labeled with dual-contrast particles (magnetite as an MRI marker and Dragon Green fluorescent dye as a histological marker) [1] were accurately identified along the rim or in the region of MI on MR imaging (Fig. 1). Signal to noise ratio and contrast to noise ratio (CNR) decreased (16.07 ± 5.85 vs.10.96± 1.34, P b 0.05) from 4 weeks to 8 weeks after labeled MSCs transplantation. Labeled MSCs were further confirmed by Prussian blue and immunofluorescent staining. Immunohistochemistry confirmed that the myogenic cells differentiated from labeled MSCs were positive for desmin and negative for CD68 (Fig. 2). Western blot analysis demonstrated that there was an increase expression of cardiomyocyte markers such as myosin heavy chain and troponin T in MSCs treatment groups compared with sham-operated group and AMI group (Fig. 3).
There is growing enthusiasm for the application of stem cell-based therapies to the regeneration of damaged myocardium. Although the results of preliminary studies and clinical trials are promising, many practical issues regarding this therapy remain highly controversial [2]. To address these important issues, molecular markers capable of tracking transplanted cells and determining the fate of engrafted cells would be extremely useful. Cells labeling with MR contrast media were used as a new technology to monitor the in vivo behavior of MSCs [3]. In the current study, we use the realtime tracking technology, MR imaging, to determine whether labeled MSCs indeed migrate into injured regions and further differentiate into cardiomyocytes after transplantation. A major difficulty in the present study is how to find the labeled MSCs after intracoronary delivery. With the idea of stem cells homing to injured myocardium, bone marrow stem cells are spontaneously mobilized to the infarction after MI [4]. Thus, identification of the infarction may serve as an alternative approach to finding the location of labeled MSCs.
☆ This work was supported by NSFC (National Nature Science Foundation of China,30570743), NSFC (30670853). ⁎ Corresponding author. E-mail address: [email protected] (G. Ma).
[7]. However, in 18 chronic heart failure patients, one Japanese group has reported both the peak CO determined by an opticatheter (10.2 ± 2.2 l/min vs. 10.9 ± 2.1 l/min, p b 0.001) to be significantly higher in the treadmill test compared to a bicycle ergometer [9]. In conclusion, Stringer calculated SV and CO are accurate at peak exercise and during recovery. However at peak exercise and at rest the method is of limited accuracy in comparison to oxygen consumption and CW Doppler based USCOM. References [1] Chan JS, Segara D, Nair P. Measurement of cardiac output with noninvasive continuous wave Doppler device versus the pulmonary artery catheter: a comparative study. Crit Care Resuscitation 2006;8(4):309–14. [2] Knobloch K, Lichtenberg A, Winterhalter M, Rossner D, Pichlmaier M, Phillips R. Non-invasive cardiac output determination by twodimensional independent Doppler during and after cardiac surgery. Ann Thorac Surg 2005;80:1479–84.
415
[3] Knobloch K, Hoeltke V, Jakob E, Vogt PM, Phillips R. Non-invasive ultrasonic cardiac output monitoring in exercise testing. Int J Cardiol 2008;126:445–7. [4] Paterson DH, Cunningham DA, Plyley MJ, Blimkie CJR, Donner D. The consistency of cardiac output measurement (CO2 rebreathe) in children during exercise. Eur J Appl Physiol 1982;49:37–44. [5] Siu CW, Tse HF, Lee K, et al. Cardiac resynchronization therapy optimization by ultrasonic cardiac output monitoring (USCOM) device. Pacing Clin Electrophysiol 2007;30(1):50–5. [6] Stringer WW, Hansen JE, Wasserman K. Cardiac output estimated noninvasively from oxygen uptake during exercise. J Appl Physiol 1997;82:908–12. [7] Stromme SB, Ingjer F, Meen HD. Assessment of maximal aerobic power in specifically trained athletes. J Appl Physiol 1977;6:833. [8] Tan HL, Pinder M, Parsons R, Roberts B, van Heerden PV. Clinical evaluation of USCOM ultrasonic cardiac output monitor in cardiac surgical patients in intensive care unit. Br J Anaesth 2005;94(3):287–91. [9] Welsman J, Bywater K, Farr C, Welford D, Armstrong N. Reliability of peak VO2 and maximal cardiac output assessed using thoracic bioimpedance in children. Eur J Appl Physiol 2005;94:228–34.
0167-5273/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2007.07.112
Effect of blood flow on drug release from DES: An experimental study P.R. Umashankar ⁎, P.R. Hari, K. Sreenivasan Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Poojapura, Trivandrum, 695012, India Received 30 June 2007; accepted 6 July 2007 Available online 14 November 2007
Abstract DES has made stenting a successful treatment modality. Still problems exists such as late thrombosis and continued neo-intimal proliferation. Blood flow affects the drug retained in the stent and subsequently on the time frame of vascular healing. To find out drug release kinetics from DES implanted in two different flow conditions, DES were implanted in porcine carotid artery and coronary artery. The drug release kinetics was found out by estimating the drug retained in the stent at different time periods. Through this study it is shown that DES in the coronary artery has a T1/2 of 24 days compared to 2 days in the carotid artery. The difference in T1/2 is attributed to the difference in flow as estimated using Hagen–Poiseuille equation. Evaluation of DES through heterotopic implantation may yield false results due to flow discrepancy. Moreover flow conditions should also be considered while designing the drug matrix to have optimum clinical efficacy. © 2007 Elsevier Ireland Ltd. All rights reserved.
In-stent restenosis, a major problem plaguing stent therapy is targeted by local delivery of antiproliferative, anti-inflammatory, antithrombotic or immunosuppresive ⁎ Corresponding author. Scientist D (Veterinary), Division of In-vivo Models and Testing, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram. Kerala, 695012, India. E-mail address: [email protected] (P.R. Umashankar).
drugs [1]. Metallic coronary stents either alone or with a degradable/non-biodegradable polymer is being used as drug eluting platform for this pharmacological prevention of restenosis. DESs contain single or multilayer biocompatible polymeric coating which ensures drug retention during deployment and modulated drug release kinetics [2]. Currently available DESs are designed to release antirestenotic drugs for at least 3 weeks after the stenting procedure to prevent smooth muscle migration and proliferation [3]. The
416
Letters to the Editor
polymeric formulations are tailored to obtain a sustained release for the stipulated time frame. Drug elution kinetics from DESs are influenced by many factors such as physiochemical properties of the drug, expanded stent configuration [4] degree of cross linking of the polymers, drug solubility and porosity and thickness of the coating [5]. The commercially available DESs are designed to provide sustained release independent of the size of the implanted vessel. To date, as far as these authors know, the influence of the blood flow through stent on the drug release profile is not reported. It can have implication on pre-clinical testing as well as clinical efficacy. In the present study, ‘Infinnium’ Paclitaxel eluting biodegradable polymer coated stents of 4.0 mm diameter and 16 mm length and 3.0 mm diameter and 11 mm length were implanted in the pig carotid artery and coronary artery respectively. In the carotid artery, a total of 15 Paclitaxel eluting stents of sizes 4.0 × 16 mm were deployed, one stent in each animal, at 16 atm pressure to achieve an estimated stent lumen of 4.56 mm. The native vessel overstretch was limited to 30%. The implantation time periods were 3, 7, 15, 30 and 90 days. Three stents were deployed per time period. The amount of Paclitaxel extracted from fresh un-implanted stent of similar size was used as day 0 value. The animals were sacrificed at the end of respective time periods and the Paclitaxel remaining in the stent was extracted with Dicloromethane and estimated using standard method. In the coronary artery, a total of 15 Paclitaxel eluting stents of sizes 3.0 × 11 mm were deployed in the Left anterior descending coronary artery, left circumflex coronary artery or right coronary artery randomly at 6 atm pressure to achieve an estimated stent lumen diameter of 3.0 mm, one stent in each animal. The native artery overstretch was limited to 30%. The implantation time periods were 1, 3, 7, 15 and 30 days. Three stents were deployed per time period. The amount of Paclitaxel extracted from fresh un-implanted stent of similar size was used as day 0 value. The animals were sacrificed at the end of respective time periods and the Paclitaxel remaining in the stent was extracted with Dicloromethane and estimated using standard method. It was apparent that drug release is much faster and T1/2 is attained around 3–4 days from stents implanted in carotid artery. Within a period of 7 days nearly 83% of the incorporated drug is released from the stent. Nearly 90% of the drug is released by 3 weeks of implantation. It is relevant to point out that a sustained release of antirestenotic drug for at least 3 weeks after deployment is required to prevent restenosis. Interestingly, a distinctively altered release pattern of drug from stents implanted in coronary artery was noticed. Here about 25% of the drug was released in the first day. After a week, around 44% of the drug was released. However, between 7 to 30 days period, only an additional 10% drug was released indicating a trend towards the attainment of a plateau phase. Even after 30 days nearly 47% of the drug was remaining in the stents. In this case, the T1/2 appeared to be 24 days. This study vividly point out that release profile of the drug incorporated in drug eluting stents is strongly influenced by the implanted artery, i.e., carotid artery or coronary artery as
the drug matrix is same for both the groups. Structurally both these arteries have similar micro-anatomy [6], except for their estimated diameters. The stented coronary artery had an estimated diameter of 3 mm and that of stented carotid artery was 4.56 mm. Assuming blood as a Newtonian fluid at this flow velocity with around 50 mm Hg pressure at the coronary artery and 100 mm Hg pressure at carotid artery respectively, and applying Hagen–Poiseuille equation to this, it was seen that the blood flow through carotid artery stent is 7.3 times that of the coronary artery stent [7]. This indicates that the relatively faster release of the drug noticed in the carotid artery stents is because of the increased blood flow through it. This can have profound clinical relevance as quicker drug release than the designed period may render the DES ineffective by failing to inhibit neo-intimal proliferation. At the same time prolonged drug retention in the stent can delay intimal healing and endothelialization thereby making it vulnerable for late thrombosis[8,9]. This study also questions the logic of using rabbit iliac artery model for the evaluation of DES compared to pig coronary artery model. Drug retention in the DES will be shorter in the rabbit iliac artery compared to pig coronary artery due to the difference in blood flow through them, even if these arteries have similar diameters and stent length. Due to the difference in the blood pressure experienced at these arteries, the blood flow through the rabbit iliac artery stent will be approximately twice that of the coronary artery stent. The temporal distribution of vessel healing will be affected by the drug retained in the stent and this may be evidenced as quicker healing response in rabbit iliac artery compared to pig coronary artery, for the same DES at similar durations. This animal study warrants that, apart from tailoring the drug containing matrix, blood flow parameters has also to be considered in the designing and evaluation of DES. Acknowledgements The authors wish to acknowledge M/s Sahajanand Medical Technologies Pvt. Ltd, Surat, India for sponsoring the study. The authors appreciate the support given by the Head, BMT wing and the Director, SCTIMST for conducting the study. References [1] Babapulle Mohan N, Eisenberg Mark J. Coated stents for prevention of restenosis: part 1. Circulation 2002;106:2734–40. [2] van der Giessen WJ, Lincoff AM, Schwartz RS, et al. Marked inflammatory sequelae to implantation of biodegradable and nonbiodegradable polymers in porcine coronary arteries. Circulation 1996;94:1690–7. [3] Sousa J Eduardo, Serruys Patrick W, Marco A Costa. New frontiers in cardiology, drug eluting stents: part 1. Circulation 2003;107:2274–9. [4] Hwang Chao-Wei, Wu David, Edelman Elazer R. Physiological transport forces govern drug distribution for stent-based delivery. Circulation 2001;104:600–5. [5] Whelan DM, van Beusekom HM, van der Giessen WJ. Mechanisms of drug loading and release kinetics. Semin interv Cardiol 1998;3:127–31.
Letters to the Editor [6] Kessel Richard G, Kardon Randy H, editors. Tissues and Organs: A Text Atlas of Scanning Electron Microscopy. USA: WH Freeman and Company; 1979. 41–44pp. [7] Nichlas Wilmer W, O'Rourke Michael F Eds, 2005. McDonalds blood flows in arteries- theoretical, experimental and clinical principles, 5th Ed., Hodder Arnold Publications, London. 11 to 48, 321 to 338 pp.
417
[8] Farb Andrew, Burke Allen P, Kolodgie Frank D, Virmani Renu. Pathological mechanisms of fatal late coronary stent thrombosis in humans. Circulation 2003;108:1701–6. [9] Joner Michael, Finn Aloke V, Farb Andrew, et al. Pathology of drugeluting stents in humans-delayed healing and late thrombotic risk. J Am Coll Cardiol 2006;48:193–202.
0167-5273/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2007.07.111
Identification and differentiation of magnetically labeled mesenchymal stem cells in vivo in swines with myocardial infarction Chun-mei Qi, Gen-shan Ma ⁎, Nai-feng Liu, Cheng-xing Shen, Zhong Chen, Xiao-jun Liu, Yao-peng Hu, Xiao-li Zhang, Ji-yuan Chen, Sheng-hong Ju,Yao-liang Tang Received 5 July 2007; accepted 6 July 2007 Available online 11 December 2007
Abstract We aim to track mesenchymal stem cells (MSCs) after magnetically labeling and test the ability of these cells differentiate into cardiomyocytes in vivo. Therefore, 20 swines were divided into four groups, sham-operated group (n = 3); acute myocardial infarction (AMI) transplanted with PBS (n = 3); labeled MSCs (n = 7) and unlabeled MSCs (n = 7) group. 107 labeled or unlabeled cells were intracoronary delivered after MI (4.8 ± 1.3 days), and serial cardiac MR (3.0T) imaging studies were performed at 0, 4 and 8 weeks after transplantation, then the results were confirmed by histological and western blot analysis. We demonstrated that labeled MSCs can be reliably detected and tracked in vivo using MR imaging. In particular, we provided the evidence of regeneration of labeled MSCs in vivo by histological examination and western blot analysis. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Magnetic resonance imaging; Contrast media; Mesenchymal stem cell; Differentiation; Myocardial infarction
1. Results
2. Discussion
MSCs after labeled with dual-contrast particles (magnetite as an MRI marker and Dragon Green fluorescent dye as a histological marker) [1] were accurately identified along the rim or in the region of MI on MR imaging (Fig. 1). Signal to noise ratio and contrast to noise ratio (CNR) decreased (16.07 ± 5.85 vs.10.96± 1.34, P b 0.05) from 4 weeks to 8 weeks after labeled MSCs transplantation. Labeled MSCs were further confirmed by Prussian blue and immunofluorescent staining. Immunohistochemistry confirmed that the myogenic cells differentiated from labeled MSCs were positive for desmin and negative for CD68 (Fig. 2). Western blot analysis demonstrated that there was an increase expression of cardiomyocyte markers such as myosin heavy chain and troponin T in MSCs treatment groups compared with sham-operated group and AMI group (Fig. 3).
There is growing enthusiasm for the application of stem cell-based therapies to the regeneration of damaged myocardium. Although the results of preliminary studies and clinical trials are promising, many practical issues regarding this therapy remain highly controversial [2]. To address these important issues, molecular markers capable of tracking transplanted cells and determining the fate of engrafted cells would be extremely useful. Cells labeling with MR contrast media were used as a new technology to monitor the in vivo behavior of MSCs [3]. In the current study, we use the realtime tracking technology, MR imaging, to determine whether labeled MSCs indeed migrate into injured regions and further differentiate into cardiomyocytes after transplantation. A major difficulty in the present study is how to find the labeled MSCs after intracoronary delivery. With the idea of stem cells homing to injured myocardium, bone marrow stem cells are spontaneously mobilized to the infarction after MI [4]. Thus, identification of the infarction may serve as an alternative approach to finding the location of labeled MSCs.
☆ This work was supported by NSFC (National Nature Science Foundation of China,30570743), NSFC (30670853). ⁎ Corresponding author. E-mail address: [email protected] (G. Ma).