[Transplantation of cardiac stem cells overexpressing integrin-linked kinase improves cardiac function in a rat model of acute myocardial infarction].

Objective: To investigate the effect of cardiac stem cells (CSC) overexpressing integrin-linked kinase (ILK-CSC) transplantation on cardiac function after myocardial infarction (MI) and related mechanism. Methods: CSCs were isolated from the hearts of neonatal Sprague-Dawley (SD) rats and ILK-CSC were established by transfecting recombinant adenoviral vector harboring human wild-type ILK cDNA. Forty 8-week-old rats were randomly divided into 4 groups ( n =10 each group): sham group, MI plus saline injection group(saline group), MI plus CSC transfected with null vector injection group (Ad-null-CSC group), and MI plus ILK-CSC injection group(ILK-CSC group). MI was induced through coronary artery ligation, and after 15 minutes, 30 μl saline, Ad-null-CSC (1×10(5) cells/30 μl) or ILK-CSC (1×10(5) cells/30 μl) were injected into the hearts of MI rats at 3 different points in infracted zone and infarct border zone. After 4 weeks, left ventricular (LV) function was examined by echocardiography, LV fibrosis was detected by HE and Masson staining, and myocardial protein expression of Ki-67 and p-H3 was evaluated by immuohistochemistry and mRNA expression of cyclinD1 and PCNA was detected by real-time RT-PCR. Results: (1) Thirty-seven rats (sham group=10, saline group=8, Ad-null-CSC group=9 and ILK-CSC group=10) survived at 4 weeks after operation. Left ventricular end-systolic dimension (LVESD, P =0.009) and left ventricular end-diastolic dimension (LVEDD, P =0.002) were significantly increased, and left ventricular ejection fraction(LVEF, P =0.006) was decreased in saline group compared with those of sham group.In Ad-null-CSC group LVESD ( P =0.005) and LVEDD ( P =0.003) were decreased, but LVEF remained unchanged ( P =0.113) compared with those of saline group. LVESD ( P =0.004) and LVEDD ( P =0.000 1) of ILK-CSC group were significantly decreased, and LVEF ( P =0.004) was significantly increased compared with those of Ad-null-CSC group. (2) LV histology and myocardial fibrosis: there were marked myocyte loss and significant increase of myocardial fibrosis in the saline group((70.6±5.1) %, P =0.002) and Ad-null-CSC group((57.7±3.4) %, P =0.001) compared with sham group ((8.2±2.2) %), while the fibrosis was significantly attenuated post injection of ILK-CSC ((30.6±7.0)%, P =0.005 vs. Ad-null-CSC). (3) Protein levels of mitotic genes: the results of immuohistochemistry showed that the brown positive particles were presented in the nuclei of cardiac myocytes in saline, Ad-null-CSC and ILK-CSC groups, but they were negative in sham group. The protein expression of Ki-67 ( P =0.007) and phosphohistone-H3 (p-H3) ( P =0.003) in ILK-CSC group was significantly higher than in Ad-null-CSC group. (4) mRNA levels of mitotic genes: the results of real-time RT-PCR showed that the mRNA levels of cyclinD1 and proliferating cell nuclear antigen (PCNA) in saline and Ad-null-CSC groups were similar as in sham group (all P >0.05). However, in ILK-CSC group they were significantly increased compared with those in Ad-null-CSC group (cyclinD1, P =0.003; PCNA, P =0.004). Conclusion: Our results suggest that myocardial transplantation of CSC overexpressing ILK improves cardiac function in the post-MI rats, and this beneficial effect may be related to the enhanced proliferation of cardiac myocytes and attenuated myocardial fibrosis.