Intramyocardially Transplanted Neonatal Cardiomyocytes (NCMs) Show Structural and Electrophysiological Maturation and Integration and Dose-Dependently Stabilize Function of Infarcted Rat Hearts.

Cardiac cell replacement therapy is a promising therapy to improve cardiac function in heart failure. Persistence, structural and functional maturation, and integration of transplanted cardiomyocytes into recipients' hearts are crucial for a safe and efficient replacement of lost cells. We studied histology, electrophysiology, and quantity of intramyocardially transplanted rat neonatal cardiomyocytes (NCMs) and performed a detailed functional study with repeated invasive (pressure-volume catheter) and noninvasive (echocardiography) analyses of infarcted female rat hearts including pharmacological stress before and 3 weeks after intramyocardial injection of 5 × 106 (low NCM) or 25 × 106 (high NCM) syngeneic male NCMs or medium as placebo (Ctrl). Quantitative real-time polymerase chain reaction (PCR) for Y-chromosome confirmed a fivefold higher persisting male cell number in high NCM versus low NCM after 3 weeks. Sharp electrode measurements within viable slices of recipient hearts demonstrated that transplanted NCMs integrate into host myocardium and mature to an almost adult phenotype, which might be facilitated through gap junctions between host myocardium and transplanted NCMs as indicated by connexin43 in histology. Ejection fraction of recipient hearts was severely impaired after ligation of left anterior descending (LAD; pressure-volume catheter: 39.2 ± 3.6%, echocardiography: 39.9 ± 1.4%). Repeated analyses revealed a significant further decline within 3 weeks in Ctrl and a dose-dependent stabilization in cell-treated groups. Consistently, stabilized cardiac function/morphology in cell-treated groups was seen in stroke volume, cardiac output, ventricle length, and wall thickness. Our findings confirm that cardiac cell replacement is a promising therapy for ischemic heart disease since immature cardiomyocytes persist, integrate, and mature after intramyocardial transplantation, and they dose-dependently stabilize cardiac function after myocardial infarction.

Influence of cell treatment with PDGF-BB and reperfusion on cardiac persistence of mononuclear and mesenchymal bone marrow cells after transplantation into acute myocardial infarction in rats.

Bone marrow cells are used for cell therapy after myocardial infarction (MI) with promising results. However, cardiac persistence of transplanted cells is rather low. Here, we investigated strategies to increase the survival and cardiac persistence of mononuclear (MNC) and mesenchymal (MSC) bone marrow cells transplanted into infarcted rat hearts. MNC and MSC (male Fischer 344 rats) were treated with different doses of PDGF-BB prior to intramyocardial injection into border zone of MI (syngeneic females, permanent LAD ligation) and hearts were harvested after 5 days and 3 weeks. In additional experiments, untreated MNC and MSC were injected immediately after permanent or temporary LAD ligation and hearts were harvested after 48 h, 5 days, 3 weeks, and 6 weeks. DNA of the hearts was isolated and the number of donor cells was determined by quantitative real-time PCR with Y chromosome-specific primers. There was a remarkable though not statistically significant (p = 0.08) cell loss of approximately 46% between 5 days and 3 weeks in the control group, which was completely inhibited by treatment with high dose of PDGF-BB. Forty-eight hours after reperfusion only 10% of injected MSC or 1% for MNC were found in the heart, decreasing to 1% for MSC and 0.5% for MNC after 6 weeks. These numbers were lower than after permanent LAD ligation for both MNC and MSC at all time points studied. Treatment with PDGF-BB seems to prevent loss of transplanted bone marrow cells at later times presumably by inhibition of apoptosis, while reperfusion of the occluded artery enhances cell loss at early times putatively due to enhanced early wash-out. Further investigations are needed to substantially improve the persistence and survival of grafted bone marrow cells in infarcted rat hearts, in order to fully explore the therapeutic potential of this novel treatment modality for myocardial repair.