[Mesenchymal stem cells implantation increases the myofibroblasts congregating in infarct region in a rat model of myocardial infarction].

OBJECTIVE

To investigate the modulation effects of mesenchymal stem cells (MSC) implantation on the myofibroblasts congregating in the infarct region after myocardial infarction (MI).

METHODS

MI was induced in SD rats by left anterior descending coronary artery ligation, and the experimental animals were assigned randomly into the sham group, MI + PBS group and MI + MSC group (myocardial injection of 0.1 ml 2×10(7)/ml in four locations in the infarct region). Echocardiography, hemodynamic examinations and Masson trichrome staining were performed. Implanted MSC differentiation and myofibroblasts congregating in infarct region were investigated by immunofluorescence staining. TGF-β(1)-Smad2 signaling pathway was examined by real-time RT-PCR and Western blot.

RESULTS

(1) Four weeks late, heart-weight/body-weight ratio [(3.04 ± 0.16) mg/g vs. (3.34 ± 0.14) mg/g, P < 0.01] and myocardial infarction size [(38.72 ± 2.38)% vs. (46.36 ± 2.81)%, P < 0.01] were significantly reduced in MI + MSC group than in MI + PBS group, while scar thickness of infarct region was thicker [(0.93 ± 0.17) mm vs. (0.65 ± 0.16) mm, P = 0.01], and LVEF was higher [LVEF: (32.5 ± 5.9)% vs. (26.5 ± 4.5)%, P = 0.03] in MI + MSC group than in MI + PBS group. (2) Myofibroblasts congregating in the infarct region was significantly enhanced in MI + MSC group compared with MI + PBS group [(196 ± 20) cells/mm(2) vs. (89 ± 25) cells/mm(2), P < 0.01], and part of implanted MSC expressed α-SMA(+). (3) TGF-β(1) expression and the phosphorylating of Smad2 in the infarct region were significantly upregulated in MI + MSC group compared with MI + PBS group (all P < 0.05).

CONCLUSIONS

MSC could improve myocardial function and promote myofibroblasts congregating in the infarct region via activating the TGF-β(1)-Smad2 signaling pathway in this model.