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Minimally invasive cell-seeded biomaterial systems for injectable/epicardial implantation in ischemic heart disease.

Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Ramakrishna S - Int J Nanomedicine (2012)

Bottom Line: These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit.An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery.This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI.

View Article: PubMed Central - PubMed

Affiliation: Healthcare and Energy Materials Laboratory, National University of Singapore, Singapore.

ABSTRACT
Myocardial infarction (MI) is characterized by heart-wall thinning, myocyte slippage, and ventricular dilation. The injury to the heart-wall muscle after MI is permanent, as after an abundant cell loss the myocardial tissue lacks the intrinsic capability to regenerate. New therapeutics are required for functional improvement and regeneration of the infarcted myocardium, to overcome harmful diagnosis of patients with heart failure, and to overcome the shortage of heart donors. In the past few years, myocardial tissue engineering has emerged as a new and ambitious approach for treating MI. Several left ventricular assist devices and epicardial patches have been developed for MI. These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit. An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery. Furthermore, intramyocardial injection of biomaterials and cells has opened new opportunities to explore and also to augment the potentials of this technique to ease morbidity and mortality rates owing to heart failure. This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI. Additionally, this review also provides a complete outlook on the tissue-engineering therapies presently being used for myocardial regeneration, as well as some perceptivity into the possible issues that may hinder its progress in the future.

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Related in: MedlinePlus

Immunocytochemical analysis for the expression of cardiac marker protein α-actinin (A–C), β-myosin heavy chain (D–F), troponin (G–I), connexin 43 (J–L) on tricalcium phosphate (A, D, G and J) and fibrinogen nanofibers (B, E, H and K) and poly(glycerol sebacate)/fibrinogen core/shell fibers (C, F, I and L) at 60× magnification.Note: Nucleus stained with DAPI (4′,6-diamidino-2-phenylindole).Reprinted from Int J Cardiol. Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Sridhar R, Ramakrishna S. Expression of cardiac proteins in neonatal cardiomyocytes on PGS/fibrinogen core/shell substrate for cardiac tissue engineering. Copyright 2012, with permission from Elsevier.47
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Related In: Results  -  Collection


getmorefigures.php?uid=PMC3526148&req=5

f2-ijn-7-5969: Immunocytochemical analysis for the expression of cardiac marker protein α-actinin (A–C), β-myosin heavy chain (D–F), troponin (G–I), connexin 43 (J–L) on tricalcium phosphate (A, D, G and J) and fibrinogen nanofibers (B, E, H and K) and poly(glycerol sebacate)/fibrinogen core/shell fibers (C, F, I and L) at 60× magnification.Note: Nucleus stained with DAPI (4′,6-diamidino-2-phenylindole).Reprinted from Int J Cardiol. Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Sridhar R, Ramakrishna S. Expression of cardiac proteins in neonatal cardiomyocytes on PGS/fibrinogen core/shell substrate for cardiac tissue engineering. Copyright 2012, with permission from Elsevier.47

Mentions: An in vitro-engineered cardiac construct is desired to possess certain essential characteristics, such as appropriate physical and mechanical properties, ready adherence, biocompatibility, nonantigenicity, noninvasive applicability, and ability for complete integration with host tissues. Li et al31 examined the transplantation of cells in a biomaterial scaffold for the treatment of MI. They demonstrated the survival of fetal cardiomyocytes on a biodegradable gelatin mesh in vitro and implanted onto the myocardial surface in a cryoinjury model; however, the cell-seeded gelatin grafts did not induce functional improvement of cardiac tissue. Subsequently, Leor et al32 demonstrated both survival and maintenance of cardiac function with fetal cardiomyocytes seeded onto an alginate scaffold, which was later implanted in a rat MI model. In another study, embryonic stem cells were mixed with type I collagen and implanted into the infarct wall by surgically creating an intramural pouch in a rat heterotopic heart-transplant model.33 The seeded cells formed viable grafts that improved fractional shortening and prevented infarct-wall thinning compared to animals that received either the scaffold without cells or treatment. Zimmermann et al34 created engineered heart tissue (EHT) by mixing cardiac myocytes isolated from neonatal Fischer 344 rats with liquid type I collagen, Matrigel, and serum-containing culture medium. EHT was made in a circular shape to fit around the circumference of hearts from syngeneic rats. After 12 days in culture, EHT was implanted on uninjured hearts. After fourteen days of implantation, EHT was completely vascularized and retained a well-organized heart muscle structure, evidenced by immunocytochemistry. However the study had drawbacks pertaining to the need for continuous administration of immunosuppressive drugs. This is because generally synthetic constructs do not allow normal cellular remodeling and may trigger immune response that may limit graft–host integration. These studies have involved scaffold-free or natural matrices for CTE, such as collagen type I and III, the major constituents of the native myocardial matrix. Studies have reported that scaffold-free human myocardial scaffolds, consisting of cardiomyocytes and the matrix to secrete, initially survive poorly after transplantation, but upon inclusion of stromal and endothelial cells enhance survival and vascularization, devoid of any foreign-body response at the graft–host interface. Moreover, it was validated that collagen-based cardiac constructs may provide additional cell-engraftment benefit over cell-injection therapies for infarct repair due to the positioning of the construct over and across an infarct rather than within it, which may increase therapeutic performance, owing to the (1) position that may enhance electrical coupling with intact myocardium on either side of the infarct and (2) separation of the graft from the inflammatory infarct environment.35 Recently, Fujimoto et al36 demonstrated an in vivo model using a biodegradable porous polyurethane patch sutured to the region of infarcted myocardium. The implanted patch improved cardiac remodeling and contractile function of the heart. Yamada et al37 and Okano et al38 utilized a temperature-responsive polymer, poly(N-isopropylacrylamide), which is hydrophobic and adhesive to cells at 37°C but becomes hydrophilic and resistant to cells at 32°C due to rapid hydration and swelling. Cardiomyocytes derived from embryonic stem cells (ESCs) were cultured with liquid collagen type I and Matrigel to construct engineered cardiac tissue.39 After 7 days of in vitro loading, the constructs could beat synchronously and react to physical/pharmaceutical stimulation. Similarly, rat cardiomyocytes cultured on a poly(N-isopropylacrylamide) sheet showed that the polymer caused the cell layers to detach when the temperature was reduced, thereby releasing cardiac myocyte sheets from the dishes without enzymatic or ethylenediaminetetraacetic acid treatment. Six months later, the researchers also observed these patches were beating and had been infiltrated by blood vessels.40 Zhang et al41 used a mixture of collagen, Matrigel, and cell-culture medium to deliver cardiomyocytes similar to Zimmermann et al18,19,34 in vitro, and reported conserved LV geometry and heart function. Implantation of engineered neonatal cardiomyocyte sheets to the MI region showed integration with infarcted myocardium and ameliorated cardiac function. Moreover, cultured cardiac cell sheets expressed angiogenesis-related genes, migrated to connect with the host vasculature, and formed endothelial cell networks after transplantation.42 Recent studies observed poly(glycerol sebacate) (PGS) to be a suitable elastomer for engineering cardiac myocardium.43,44 It is a biodegradable, synthetic, and biocompatible polymer and exhibits elastomer-like mechanical behavior,45 showing a wide range of stiffness values (10 kPa to 1.2 MPa) that could be tailored to be either softer or stiffer than the heart muscles.46 Ravichandran et al47 fabricated PGS/fibrinogen core/shell fibers for culturing cardiomyocytes that showed enhanced expression of cardiac-specific marker proteins like actinin, troponin, and myosin heavy-chain and gap junction protein connexin-43 compared to tissue culture plate and fibrinogen nanofibers, as shown in Figure 2, indicating that these core/shell fibers may prove to be suitable biomaterial for the treatment of MI. They attributed enhanced survival of cardiomyocytes on these scaffolds to the ECM-mimicking nanofibrous architecture and the favorable elastic property provided by PGS.47 In a similar study, hydrophilic, biocompatible nanofibrous scaffolds made of poly(l-lactic acid)-co-poly(ɛ-caprolactone)/collagen blend, fabricated by electrospinning, were reported to provide enhanced attachment and growth of adult cardiac cells favoring native myocardium-like alignment of cardiac cells for regeneration of infarcted myocardium.48 However, even with all the efforts invested, the in vitro approach for CTE followed by transplantation of biomaterial in vivo has shown only partial success. After transplantation, adequate perfusion, rapid vascularization, cell survival, integration, and function of the engineered cardiac patch remain vital steps in the translation of in vitro cardiac patches into effective clinical tools.


Minimally invasive cell-seeded biomaterial systems for injectable/epicardial implantation in ischemic heart disease.

Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Ramakrishna S - Int J Nanomedicine (2012)

Immunocytochemical analysis for the expression of cardiac marker protein α-actinin (A–C), β-myosin heavy chain (D–F), troponin (G–I), connexin 43 (J–L) on tricalcium phosphate (A, D, G and J) and fibrinogen nanofibers (B, E, H and K) and poly(glycerol sebacate)/fibrinogen core/shell fibers (C, F, I and L) at 60× magnification.Note: Nucleus stained with DAPI (4′,6-diamidino-2-phenylindole).Reprinted from Int J Cardiol. Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Sridhar R, Ramakrishna S. Expression of cardiac proteins in neonatal cardiomyocytes on PGS/fibrinogen core/shell substrate for cardiac tissue engineering. Copyright 2012, with permission from Elsevier.47
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3526148&req=5

f2-ijn-7-5969: Immunocytochemical analysis for the expression of cardiac marker protein α-actinin (A–C), β-myosin heavy chain (D–F), troponin (G–I), connexin 43 (J–L) on tricalcium phosphate (A, D, G and J) and fibrinogen nanofibers (B, E, H and K) and poly(glycerol sebacate)/fibrinogen core/shell fibers (C, F, I and L) at 60× magnification.Note: Nucleus stained with DAPI (4′,6-diamidino-2-phenylindole).Reprinted from Int J Cardiol. Ravichandran R, Venugopal JR, Sundarrajan S, Mukherjee S, Sridhar R, Ramakrishna S. Expression of cardiac proteins in neonatal cardiomyocytes on PGS/fibrinogen core/shell substrate for cardiac tissue engineering. Copyright 2012, with permission from Elsevier.47
Mentions: An in vitro-engineered cardiac construct is desired to possess certain essential characteristics, such as appropriate physical and mechanical properties, ready adherence, biocompatibility, nonantigenicity, noninvasive applicability, and ability for complete integration with host tissues. Li et al31 examined the transplantation of cells in a biomaterial scaffold for the treatment of MI. They demonstrated the survival of fetal cardiomyocytes on a biodegradable gelatin mesh in vitro and implanted onto the myocardial surface in a cryoinjury model; however, the cell-seeded gelatin grafts did not induce functional improvement of cardiac tissue. Subsequently, Leor et al32 demonstrated both survival and maintenance of cardiac function with fetal cardiomyocytes seeded onto an alginate scaffold, which was later implanted in a rat MI model. In another study, embryonic stem cells were mixed with type I collagen and implanted into the infarct wall by surgically creating an intramural pouch in a rat heterotopic heart-transplant model.33 The seeded cells formed viable grafts that improved fractional shortening and prevented infarct-wall thinning compared to animals that received either the scaffold without cells or treatment. Zimmermann et al34 created engineered heart tissue (EHT) by mixing cardiac myocytes isolated from neonatal Fischer 344 rats with liquid type I collagen, Matrigel, and serum-containing culture medium. EHT was made in a circular shape to fit around the circumference of hearts from syngeneic rats. After 12 days in culture, EHT was implanted on uninjured hearts. After fourteen days of implantation, EHT was completely vascularized and retained a well-organized heart muscle structure, evidenced by immunocytochemistry. However the study had drawbacks pertaining to the need for continuous administration of immunosuppressive drugs. This is because generally synthetic constructs do not allow normal cellular remodeling and may trigger immune response that may limit graft–host integration. These studies have involved scaffold-free or natural matrices for CTE, such as collagen type I and III, the major constituents of the native myocardial matrix. Studies have reported that scaffold-free human myocardial scaffolds, consisting of cardiomyocytes and the matrix to secrete, initially survive poorly after transplantation, but upon inclusion of stromal and endothelial cells enhance survival and vascularization, devoid of any foreign-body response at the graft–host interface. Moreover, it was validated that collagen-based cardiac constructs may provide additional cell-engraftment benefit over cell-injection therapies for infarct repair due to the positioning of the construct over and across an infarct rather than within it, which may increase therapeutic performance, owing to the (1) position that may enhance electrical coupling with intact myocardium on either side of the infarct and (2) separation of the graft from the inflammatory infarct environment.35 Recently, Fujimoto et al36 demonstrated an in vivo model using a biodegradable porous polyurethane patch sutured to the region of infarcted myocardium. The implanted patch improved cardiac remodeling and contractile function of the heart. Yamada et al37 and Okano et al38 utilized a temperature-responsive polymer, poly(N-isopropylacrylamide), which is hydrophobic and adhesive to cells at 37°C but becomes hydrophilic and resistant to cells at 32°C due to rapid hydration and swelling. Cardiomyocytes derived from embryonic stem cells (ESCs) were cultured with liquid collagen type I and Matrigel to construct engineered cardiac tissue.39 After 7 days of in vitro loading, the constructs could beat synchronously and react to physical/pharmaceutical stimulation. Similarly, rat cardiomyocytes cultured on a poly(N-isopropylacrylamide) sheet showed that the polymer caused the cell layers to detach when the temperature was reduced, thereby releasing cardiac myocyte sheets from the dishes without enzymatic or ethylenediaminetetraacetic acid treatment. Six months later, the researchers also observed these patches were beating and had been infiltrated by blood vessels.40 Zhang et al41 used a mixture of collagen, Matrigel, and cell-culture medium to deliver cardiomyocytes similar to Zimmermann et al18,19,34 in vitro, and reported conserved LV geometry and heart function. Implantation of engineered neonatal cardiomyocyte sheets to the MI region showed integration with infarcted myocardium and ameliorated cardiac function. Moreover, cultured cardiac cell sheets expressed angiogenesis-related genes, migrated to connect with the host vasculature, and formed endothelial cell networks after transplantation.42 Recent studies observed poly(glycerol sebacate) (PGS) to be a suitable elastomer for engineering cardiac myocardium.43,44 It is a biodegradable, synthetic, and biocompatible polymer and exhibits elastomer-like mechanical behavior,45 showing a wide range of stiffness values (10 kPa to 1.2 MPa) that could be tailored to be either softer or stiffer than the heart muscles.46 Ravichandran et al47 fabricated PGS/fibrinogen core/shell fibers for culturing cardiomyocytes that showed enhanced expression of cardiac-specific marker proteins like actinin, troponin, and myosin heavy-chain and gap junction protein connexin-43 compared to tissue culture plate and fibrinogen nanofibers, as shown in Figure 2, indicating that these core/shell fibers may prove to be suitable biomaterial for the treatment of MI. They attributed enhanced survival of cardiomyocytes on these scaffolds to the ECM-mimicking nanofibrous architecture and the favorable elastic property provided by PGS.47 In a similar study, hydrophilic, biocompatible nanofibrous scaffolds made of poly(l-lactic acid)-co-poly(ɛ-caprolactone)/collagen blend, fabricated by electrospinning, were reported to provide enhanced attachment and growth of adult cardiac cells favoring native myocardium-like alignment of cardiac cells for regeneration of infarcted myocardium.48 However, even with all the efforts invested, the in vitro approach for CTE followed by transplantation of biomaterial in vivo has shown only partial success. After transplantation, adequate perfusion, rapid vascularization, cell survival, integration, and function of the engineered cardiac patch remain vital steps in the translation of in vitro cardiac patches into effective clinical tools.

Bottom Line: These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit.An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery.This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI.

View Article: PubMed Central - PubMed

Affiliation: Healthcare and Energy Materials Laboratory, National University of Singapore, Singapore.

ABSTRACT
Myocardial infarction (MI) is characterized by heart-wall thinning, myocyte slippage, and ventricular dilation. The injury to the heart-wall muscle after MI is permanent, as after an abundant cell loss the myocardial tissue lacks the intrinsic capability to regenerate. New therapeutics are required for functional improvement and regeneration of the infarcted myocardium, to overcome harmful diagnosis of patients with heart failure, and to overcome the shortage of heart donors. In the past few years, myocardial tissue engineering has emerged as a new and ambitious approach for treating MI. Several left ventricular assist devices and epicardial patches have been developed for MI. These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit. An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery. Furthermore, intramyocardial injection of biomaterials and cells has opened new opportunities to explore and also to augment the potentials of this technique to ease morbidity and mortality rates owing to heart failure. This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI. Additionally, this review also provides a complete outlook on the tissue-engineering therapies presently being used for myocardial regeneration, as well as some perceptivity into the possible issues that may hinder its progress in the future.

Show MeSH
Related in: MedlinePlus