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We compared therapeutic benefits of intramyocardial injection of unfractionated bone marrow cells (BMCs) versus BMC extract as treatments for myocardial infarction (MI), using closed-chest ultrasound-guided injection at a clinically relevant time post-MI. MI was induced in mice and the animals treated at day 3 with either: (i) BMCs from green fluorescent protein (GFP)-expressing mice (n = 14), (ii) BMC extract (n = 14), or (iii) saline control (n = 14). Six animals per group were used for histology at day 6 and the rest followed to day 28 for functional analysis. Ejection fraction was similarly improved in the BMC and extract groups versus control (40.6 ± 3.4 and 39.1 ± 2.9% versus 33.2 ± 5.0%, P < 0.05) with smaller scar sizes. At day 6 but not day 28, both therapies led to significantly higher capillary area and number of arterioles versus control. At day 6, BMCs increased the number of cycling cardiomyocytes (CMs) versus control whereas extract therapy resulted in significant reduction in the number of apoptotic CMs at the border zone (BZ) versus control. Intracellular components within BMCs can enhance vascularity, reduce infarct size, improve cardiac function, and influence CM apoptosis and cycling early after therapy following MI. Intact cells are not necessary and death of implanted cells may be a major component of the benefit.Molecular Therapy (2009) 17 7, 1250–1256. doi:10.1038/mt.2009.85 [ABSTRACT FROM AUTHOR]

Assessment of severity of a myocardial infarction (MI) is an important measure of success after experimental delivery of potentially therapeutic genes or cells in rodent MI models. In experiments involving an acute MI setting, histological measurement of the area of the infarcted region in tissue sections of the left ventricle (LV) is a standard assessment of “infarct size.” This approach is also used by numerous investigators in a chronic infarct setting, taking infarct area measurements several weeks post-MI. However, we hypothesized that wall thinning due to remodeling of a transmural infarct would invalidate the correlation between a severe infarct and a large infarct scar area measurement, reducing the legitimacy of this approach in a chronic setting. To address this issue, we assessed left ventricular ejection fraction (LVEF; cardiac systolic function) in 8 infarcted mouse hearts and ranked them according to increasing severity. Tissue sections were collected approximately every 300 uM from apex to base and were stained with Masson's trichrome to visualize the infarct scar. The scar was measured in each section by a blinded investigator using several strategies, the numbers obtained were combined to express infarct size as percentage of total LV volume, and the values were compared to the functional measurements for each heart. Our measurement strategies consisted of calculation of the ratio of (1) summed infarct areas to summed LV myocardial areas (Area Measurement: AM), (2) summed epicardial and endocardial infarct arc lengths to summed epicardial and endocardial LV circumferences (Length Measurement: LM), and (3) summed midline infarct arc lengths to summed midline LV circumferences (Midline Length Measurement: MLM). Linear correlation analyses showed that infarct size from all three measurement approaches correlated significantly with LVEF (r=0.87, p<0.01 for each method) and wall motion score index (r=0.97-0.98, p<0.01 for each). However, the infarct size calculated using AM was significantly smaller than those using the other measurements (average of values obtained for all hearts studied: AM 10.83±6.53% vs. LM 26.72±19.04%, MLM 26.08±20.94%, p<0.01), and the range of values obtained was compressed 0.4-fold, substantially compromising the accuracy of this approach. We conclude that while wall thinning did not invalidate the use of area-based infarct size measurements, it underestimated the extent of the infarct and substantially reduced the sensitivity of this measure compared to measurements based on infarct arc lengths. We further conclude that the estimation of myocardial and infarct midlines provided comparable accuracy to the more cumbersome tracing of epicardial and endocardial lengths and circumferences. These findings demonstrate that the ratio of summed infarct midlines to summed LV midlines is significantly better than infarct area measurements as an assessment of infarct size in cell or gene therapy studies in chronic rodent MI models.Molecular Therapy (2006) 13, S92–S92; doi: 10.1016/j.ymthe.2006.08.265 [ABSTRACT FROM AUTHOR]

Objective: Myocardial regeneration based on stem cell transplantation has emerged as a potential therapeutic approach toward replacing myocardial scar with functioning contractile tissue after myocardial infarction (MI). Considerable interest has focused on bone marrow cells (BMCs) and endothelial progenitor cells (EPCs) because they appear successful in attenuating remodeling following acute MI. However, preclinical experiments toward this goal have been limited to treatment within hours of an MI, in contrast to human trials, in which cell treatment has been performed several days later after patient stabilization and autologous cell harvesting. We sought to compare the therapeutic effects of different types of putative stem and progenitor cells in a mouse model of MI using a novel closed-chest echo-guided injection approach to deliver cells 3 days after infarction.Methods: MI was surgically induced in adult male mice by performing a mid-LAD ligation. Closed-chest echo-guided injection of cells (5 x 105 in 5 ul or saline control (HBSS) into myocardium at the peri-infarct border zone was performed at day 3 post-MI in the following groups (n=8/group): mouse BMCs (mBMCs) into C57BL/6 mice, human BMCs into immunodeficient SCID mice, mBMCs into SCID, human EPCs into SCID, and HBSS into both C57BL/6 and SCID as controls. Echocardiography was accomplished in a blinded manner with a Vevo 660 system (VisualSonics, Toronto) at baseline, 2 days post-MI (before injection), and at day 28 post-MI.Results: Left ventricular ejection fraction (LVEF) was uniformly reduced from 57.2+/-4.0% to 38.4+/-3.7% (p<0.0001) after MI in all groups. Mice injected with mBMCs showed the best effect with significant improvement in global LVEF (37.8+/-2.3% vs 44.4+/-6.3%, p=0.03), and in regional wall motion index in the infarct area (1.79+/-0.21 vs 1.4+/-0.29, p=0.02) at day 28, and there was a tendency toward less dilation of cardiac dimensions compared with that before injection. The global systolic function of the treatment group injected with mBMCs was significantly better preserved than that of its corresponding control group (44.4+/-6.3% vs 31.1+/-10.4%, p<0.0005). Human EPC injection showed a non-significant trend toward improvement of LVEF and less LV dilation, while the LVEF of its corresponding control group continued to decrease, resulting in a significant difference between the EPC group and its controls at day 28 (41.5 +/-4.3 vs 32.1+/-6.3, p<0.0005).Conclusions: Unfractionated mouse bone marrow cells attenuated ventricular remodeling and partially preserved LV function when delivered several days after surgically-induced MI. However, injection of different cell types affects LV function to varying extents. The percutaneous echo-guided injection approach made it possible to assess therapeutic cell implantation at a clinically relevant time after MI in a mouse model.Molecular Therapy (2006) 13, S175–S175; doi: 10.1016/j.ymthe.2006.08.521 [ABSTRACT FROM AUTHOR]