Repeated Administrations of Cardiac Progenitor Cells Are Markedly More Effective Than a Single Administration

Abstract

Rationale The effects of c-kitPOS cardiac progenitor cells (CPCs) (and adult cell therapy in general) on left ventricular (LV) function have been regarded as modest or inconsistent. Objective To determine whether three CPC infusions have greater efficacy than one infusion. Methods and Results Rats with a 30-day-old myocardial infarction received one or three CPC infusions into the LV cavity, 35 days apart. Compared with vehicle-treated rats, the single-dose group exhibited improved LV function after the 1st infusion (consisting of CPCs) but not after the 2nd and 3rd (vehicle). In contrast, in the multiple-dose group regional and global LV function improved by a similar degree after each CPC infusion, resulting in greater cumulative effects. For example, the total increase in LV ejection fraction was approximately triple in the multiple-dose group vs. the single-dose group (P<0.01). The multiple-dose group also exhibited more viable tissue and less scar, less collagen in the risk and noninfarcted regions, and greater myocyte density in the risk region. Conclusions This is the first demonstration that repeated CPC administrations are markedly more effective than a single administration. The concept that the full effects of CPCs require repeated doses has significant implications for both preclinical and clinical studies; it suggests that the benefits of cell therapy may be underestimated or even overlooked if they are measured after a single dose, and that repeated administrations are necessary to properly evaluate the effectiveness of a cell product. In addition, we describe a new method that enables studies of repeated cell administrations in rodents.

Repeated Administrations of Cardiac Progenitor Cells Are Superior to a Single Administration of an Equivalent Cumulative Dose

“…The isolation, characterization, and expansion of CPCs have been previously described 3, 8, 9. Briefly, cardiac cells were isolated from adult male Fischer 344 rats (4–6 months of age).…”

“…The rat model of old MI has been described previously 3, 7. Adult female Fischer 344 rats (age, 4 months; weight 175±2 g) underwent a 2‐hour occlusion of the left anterior descending coronary artery followed by reperfusion.…”

“…All rats received 3 echo‐guided intraventricular injections, 35 days apart, as described previously 3. Briefly, animals were anesthetized lightly with isoflurane, placed on the imaging table in the right lateral decubitus position, and prepared for imaging using the Vevo 2100 Imaging System (VisualSonics) equipped with a 20‐MHz transducer to determine the optimal site for needle insertion, a site that did not include the infarct scar or a coronary artery.…”

“…Serial echocardiograms were obtained at 5 time points: baseline (3 days before coronary artery occlusion), 30 days after MI (before the first treatment), 35 days after the first treatment (before the second treatment), 35 days after the second treatment (before the third treatment), and 35 days after the third treatment (before euthanasia; Figure 1). The echocardiographic studies were performed as described3, 7, 8, 9, 10 using a Vevo 2100 Imaging System equipped with a 20‐MHz transducer.…”

“…The hemodynamic studies were conducted 35 days after the third treatment, just before euthanasia (Figure 1). The protocol has been described previously 3, 7, 8, 9, 10…”