Increased potency of cardiac stem cells compared with bone marrow mesenchymal stem cells in cardiac repair

Abstract

Whereas cardiac-derived c-kit(+) stem cells (CSCs) and bone marrow-derived mesenchymal stem cells (MSCs) are undergoing clinical trials testing safety and efficacy as a cell-based therapy, the relative therapeutic and biologic efficacy of these two cell types is unknown. We hypothesized that human CSCs have greater ability than MSCs to engraft, differentiate, and improve cardiac function. We compared intramyocardial injection of human fetal CSCs (36,000) with two doses of adult MSCs (36,000 and 1,000,000) or control (phosphate buffered saline) in nonobese diabetic/severe combined immune deficiency mice after coronary artery ligation. The myocardial infarction-induced enlargement in left ventricular chamber dimensions was ameliorated by CSCs (p < .05 for diastolic and systolic volumes), as was the decline in ejection fraction (EF; p < .05). Whereas 1 × 10(6) MSCs partially ameliorated ventricular remodeling and improved EF to a similar degree as CSCs, 36,000 MSCs did not influence chamber architecture or function. All cell therapies improved myocardial contractility, but CSCs preferentially reduced scar size and reduced vascular afterload. Engraftment and trilineage differentiation was substantially greater with CSCs than with MSCs. Adult-cultured c-kit(+)CSCs were less effective than fetal, but were still more potent than high-dose MSCs. These data demonstrate enhanced CSC engraftment, differentiation, and improved cardiac remodeling and function in ischemic heart failure. MSCs required a 30-fold greater dose than CSCs to improve cardiac function and anatomy. Together, these findings demonstrate a greater potency of CSCs than bone marrow MSCs in cardiac repair.

Figure 1.

C-kit⁺ CSCs improve cardiovascular function as assessed by echocardiography. (A): EDV. (B): ESV. (C): EF, p < .05. (D): Representative echocardiographic M-mode short axis images showing preserved anatomy and function of LV in CSC-treated mice and severe dyskinesia and ventricular dilatation in control and low-dose MSC heart. *, p < .05. Abbreviations: CSC, cardiac stem cell; EDV, end diastolic volume; EF, ejection fraction; ESV, end systolic volume; MSC, mesenchymal stem cell.

Figure 2.

CSCs improve hemodynamic parameters more than MSCs. (A): Preload recruitable stroke work recorded during IVC occlusion. (B): Arterial elastance. (C): Representative PV loops showing preserved loop morphometry in the CSC-treated heart and increased ventricular volumes and decreased systolic function in control heart. *, p < .05. Abbreviations: CSC, cardiac stem cell; IVC, inferior vena cava; MSC, mesenchymal stem cell; PV, pressure volume.

Figure 3.

CSC therapy reduces scar size. Trichrome Masson (TM) staining of (A): control, (B): CSC, (C): low-dose MSC, and (D): high-dose MSC-treated hearts. (E): Quantitation of scar size following TM staining. *, p < .05. Abbreviations: CSC, cardiac stem cell; LV, left ventricle; MSC, mesenchymal stem cell.

Figure 4.

Cardiac stem cell-injected hearts (×40). (A): Remote area: Alu (pink), Cx43 (white), Laminin (green), TnI (long arrow). (B), (C): Alu⁺ cells in the (B) peri-infarct area and (C) infarcted area. (D): Border zone: Alu (pink), αSA, (white), coexpression (arrow). (E): Remote area: Alu and TnI costaining (long arrow), laminin (orange). Intercellular space: Alu⁺ (short arrows). (F): Border zone. Abbreviations: Cx43, connexin 43; DAPI, 4′,6-diamidino-2-phenylindole; TnI, troponin I.

Figure 5.

Human CSCs engraft better and are more widely distributed than human MSCs. Reconstructed images after tiling fluorescent scans at the midventricular level of Alu-stained hearts 8 weeks after cell delivery. Numbers = count of Alu⁺ cells. (A): CSCs, box outlines region of inset. Inset: an example of Alu⁺ cells (pink-stained nuclei) that were counted. (B): High-dose and (C): low-dose MSCs. DAPI (blue-stained nuclei). (D): Quantitation of Alu⁺ cells (p = .0006). **, p < .01. Abbreviations: CSC, cardiac stem cell; DAPI, 4′,6-diamidino-2-phenylindole; MSC, mesenchymal stem cell.

Figure 6.

Immunohistochemistry of mesenchymal stem cell (MSC)-injected hearts, (A), (B): High-dose MSC. A: Border/peri infarct zone: Alu⁺ cells (pink) in proximity to the vascular wall (white arrows) and between myocardial cells (arrow head). (B): Remote zone: α-SA (green), Laminin (orange). (C), (D): 36 × 10³ MSCs: Few Alu- and no TnI-positive cells (arrows).