Aarne Jyrala

Delivering stem cells to the heart in a collagen matrix reduces relocation of cells to other organs as assessed by nanoparticle technology

AIM A limitation of cell therapy for heart disease is the fact that stem cells injected directly into the myocardium are capable of entering the vasculature and migrating to remote organs. We determined whether retention of mesenchymal stem cells (MSCs) in the infarcted myocardium could be improved by implanting the cells in a collagen matrix. METHODS A myocardial infarction was induced by ligation of the left anterior descending coronary artery in Fischer rats. A total of 7 days after myocardial infarction, saline (n = 12), saline plus 2 million bone marrow-derived rat MSCs labeled with isotopic colloidal nanoparticles containing europium (n = 13), collagen (n = 13) or collagen plus 2 million labeled MSCs (n = 13) were directly injected into the infarcted myocardium. Tissues from the infarcted myocardium, noninfarcted myocardium, lung, liver, spleen and kidney were sampled 4 weeks later. Distribution of grafted MSCs was quantitatively analyzed by measuring the nanoparticle radioactivity in these tissues. Cardiac function was assessed by left ventriculography. RESULTS There were zero nanoparticles detected in the tissues that received saline or collagen alone into the heart. Nanoparticles were detected in the heart and remote organs in the saline plus MSC group. Labeled cells (expressed as cell number/g tissue weight) were present in three out of 13 lungs (mean of 12,724 +/- 7060 cells/g), four out of 13 livers (12,301 +/- 5924 cells/g), 11 out of 13 spleens (57,228 +/- 11,483 cells/g), zero out of 13 kidneys, 13 out of 13 infarcted myocardium (8,006,835 +/- 1,846,462 cells/g) and nine out of 13 noninfarcted myocardium (167,331 +/- 47,007 cells/g). However, compared with the saline plus MSC group, nanoparticles were detected to a lesser extent in remote organs in collagen plus MSC group. Nanoparticles were detected in two out of 13 lungs (4631 +/- 3176 cells/g; p = NS), zero out of 13 livers (0 cells/g; p <0.05 vs saline plus MSC), four out of 13 spleens (24,060 +/- 17,373 cells/g; p <0.05), zero out of 13 kidneys (p = NS) and five out of 13 noninfarcted myocardium (51,522 +/- 21,548 cells/g; p <0.05). In the collagen plus MSC group, nanoparticles were detected in 12 out of 13 infarcted myocardium (4,830,050 +/- 592,215 cells/g), which did not significantly differ from that in the saline plus MSC group (p = NS). Both saline plus MSCs and collagen alone improved left ventricular ejection fraction compared with saline treatment. However, collagen plus MSCs failed to improve cardiac function. CONCLUSIONS Collagen matrix as a delivery vehicle significantly reduced the relocation of transplanted MSCs to remote organs and noninfarcted myocardium.

Intramyocardial Injection of Heart Tissue-Derived Extracellular Matrix Improves Postinfarction Cardiac Function in Rats

Aims: We determined whether implantation of heart tissue-derived decellularized matrix, which contains native biochemical and structural matrix composition, could thicken the infarcted left ventricular (LV) wall and improve LV function in a rat myocardial infarction model. Methods and Results: Myocardial infarction was induced by left coronary ligation in Fischer rats. One week later, saline (75 μL, n = 17) or matrix (75 μL, n = 19) was directly injected into the infarcted area. At 6 weeks after injection, cardiac function was assessed by left ventriculogram, echocardiography, and Millar catheter. The hearts were pressure fixed to measure postmortem LV volume and processed for histology. Left ventriculogram demonstrated that LV ejection fraction (EF) was significantly greater in the matrix-treated (56.7% ± 1.4%) than in the saline-treated group (52.4% ± 1.5%; P = .043), and paradoxical LV systolic bulging was significantly reduced in the matrix-treated group (6.2% ± 1.6% of the LV circumference) compared to the saline-treated group (10.3% ± 1.3%; P = .048). Matrix implantation significantly increased the thickness of infarcted LV wall (0.602 ± 0.029 mm) compared to the saline-treated group (0.484 ± 0.03 mm; P = .0084). Infarct expansion index was significantly lower in the matrix-treated group (1.053 ± 0.051) than in the saline-treated group (1.382 ± 0.096, P = .0058). Blood vessel density and c-kit positive staining cells within the infarct area were comparable between the 2 groups. Conclusions: Implantation of heart tissue-derived decellularized matrix thickens the LV infarcted wall, prevents paradoxical LV systolic bulging, and improves LV EF after myocardial infarction in rats. This benefit was not dependent on the enhanced angiogenesis or the recruitment of endogenous stem cells to the injury site.

Cardioprotective Effects of Angiotensin II Type 1 Receptor Blockade with Olmesartan on Reperfusion Injury in a Rat Myocardial Ischemia-Reperfusion Model

We determined the effects of olmesartan on infarct size and cardiac function in a rat ischemia/reperfusion model. Rats underwent 30 min of left coronary artery (CA) occlusion followed by 2 h of reperfusion. In protocol 1, the rats received (by i.v.) 1 mL of vehicle at 10 min after CA occlusion (Group 1, n = 15); olmesartan (0.3 mg/kg) at 10 min after CA occlusion (Group 2, n = 15); 1 mL of vehicle at 5 min before CA reperfusion (Group 3, n = 15); or olmesartan (0.3 mg/kg) 5 min before CA reperfusion (Group 4, n = 15). In protocol 2, the rats received (by i.v.) 1 mL of vehicle at 5 min before CA reperfusion (Group 5, n = 21); or olmesartan (3 mg/kg) at 5 min before CA reperfusion (Group 6, n = 21). Systemic hemodynamics, left ventricular (LV) function, LV ischemic risk zone, no-reflow zone, and infarct size were determined. In protocol 1, olmesartan (0.3 mg/kg) did not affect blood pressure (BP), heart rate, LV +/- dp/dt or LV fractional shortening during the experimental procedure, and did not alter no-reflow or infarct size. In protocol 2, olmesartan (3 mg/kg) significantly reduced infarct size to 21.7 +/- 4.1% from 34.3 +/- 4.1% of risk zone in the vehicle group (P= 0.035), but did not alter the no-reflow size. Prior to CA reperfusion, olmesartan (3 mg/kg) significantly reduced mean BP by 22% and LV +/-dp/dt, but did not affect heart rate. At 2 h after reperfusion, olmesartan significantly decreased heart rate by 21%, mean BP by 14%, and significantly increased LV fractional shortening from 54.1 +/- 1.4% to 61.3 +/- 1.6% (P= 0.0018). Olmesartan significantly reduced myocardial infarct size and improved LV contractility at a dose (3 mg/kg) with systemic vasodilating effects but not at a lower dose (0.3 mg/kg) without hemodynamic effects.

Experience from experimental cell transplantation therapy of myocardial infarction: what have we learned?

During the past 15 years, our research group has transplanted fetal/neonatal cardiomyocytes, mesenchymal stem cells, and embryonic stem cell-derived cardiomyocytes into infarcted myocardium in a rat myocardial infarction model. Our experimental data demonstrated that cell transplantation therapy provides a potential approach for the treatment of injured myocardium after myocardial infarction based on the reported positive effects upon histological appearance and left ventricular function. However, the underlying mechanisms of the benefits from cell transplantation therapy remain unclear and may involve replacement of scar tissue by transplanted cells, induced neoangiogenesis and paracrine effects of factors released by the transplanted cells. In this review, we summarize our experiences from experimental cell transplantation therapy in a rat myocardial infarction model and discuss the controversies and questions that need to be addressed in future studies.