Intracardiac injection of matrigel induces stem cell recruitment and improves cardiac functions in a rat myocardial infarction model

Abstract

Matrigel promotes angiogenesis in the myocardium from ischemic injury and prevents remodelling of the left ventricle. We assessed the therapeutic efficacy of intracardiac matrigel injection and matrigel-mediated stem cell homing in a rat myocardial infarction (MI) model. Following MI, matrigel (250 μl) or phosphate-buffered solution (PBS) was delivered by intracardiac injection. Compared to the MI control group (MI-PBS), matrigel significantly improved left ventricular function (n= 11, P < 0.05) assessed by pressure-volume loops after 4 weeks. There is no significant difference in infarct size between MI-matrigel (MI-M; 21.48 ± 1.49%, n = 10) and MI-PBS hearts (20.98 ± 1.25%, n = 10). The infarct wall thickness of left ventricle is significantly higher (P < 0.01) in MI-M (0.72 ± 0.02 mm, n = 10) compared with MI-PBS (0.62 ± 0.02 mm, n = 10). MI-M hearts exhibited higher capillary density (border 130.8 ± 4.7 versus 115.4 ± 6.0, P < 0.05; vessels per high-power field [HPF; 400×], n = 6) than MI-PBS hearts. c-Kit(+) stem cells (38.3 ± 5.3 versus 25.7 ± 1.5 c-Kit(+) cells per HPF [630×], n = 5, P < 0.05) and CD34(+) cells (13.0 ± 1.51 versus 5.6 ± 0.68 CD34(+) cells per HPF [630×], n = 5, P < 0.01) were significantly more numerous in MI-M than in MI-PBS in the infarcted hearts (n = 5, P < 0.05). Intracardiac matrigel injection restores myocardial functions following MI, which may attribute to the improved recruitment of CD34(+) and c-Kit(+) stem cells.

Fig 1

Local matrigel injection improved cardiac functions 4 weeks after MI assessed by catherization. Left ventricular function (EF, dp/dt max and dp/dt min, n= 11) is significantly improved in MI-M compared with MI-PBS. *P < 0.05.

Fig 2

Effects of local matrigel injection on cardiac remodelling 4 weeks after MI. (A), (B) Representative heart cross sections stained with Sirius Red (red, fibrosis) and Fast Green FCF (green, myocyte) from rats. (C) Ratio of infarction size to entire heart is not significantly decreased in MI-M (n= 10) compared with MI-PBS (n= 10). (D) The infarct LWT is significantly higher in MI-M (n= 10) compared with MI-PBS (n= 10). *P < 0.01.

Fig 3

Local matrigel injection induces neovascularization 4 weeks after MI. Endothelial CD31 were stained in the border of the infarct of hearts. Representative micrographs of the border of the infarct in the three groups of animals [(A) Sham, (B) MI-PBS, (C) MI-M, Blue, DAPI in nuclei, 400×]. (D) Morphometric analysis of vessel density in the border of the infarct in the various groups. Data are mean values ± S.E.M. *P < 0.05 MI-M versus MI-PBS (sham, n= 6, MI-PBS, n= 6 and MI-M, n= 6). HPF: high-power field. Scale bars = 250 μm.

Fig 4

Local matrigel injection increases the myocardial homing of c-Kit⁺ cells. Representative immunostaining for c-Kit in the three groups of animals. c-Kit⁺ cells (green) were identified in infarct border zone at 4 weeks after treatment. Red, TOPRO3 in nuclei. Yellow is shown after green [(A), sham, (B), MI-PBS, (C–F), MI-M]. (D) The number of c-Kit⁺ cells per HPF in MI-M hearts (n= 5) was significantly higher than in MI hearts (n= 5), and c-Kit⁺ cells can seldom be seen in sham animals (n= 5). *P < 0.01. (A–C) scale bars = 250 μm; (D–F) scale bars = 25 μm.

Fig 5

Local matrigel injection increases the myocardial homing of CD34⁺ cells. (A)–(C) and (C)’ Representative images for CD34⁺ (green) cells (square) in at 4 weeks after local matrigel injection. Red, TOPRO3 in nuclei. Yellow is shown after green. (D) The number of CD34⁺ cells per HPF in MI-M (n= 5) was significantly higher than in MI-PBS (n= 5) hearts. *P < 0.01. (A), (B) and (C’): scale bars = 25 μm; (C) scale bars = 250 μm.