FGF21 Pretreatment Promotes the Cardioprotective Effects of Mesenchymal Stem Cells in Myocardial Infarction via Enhancement of Their Survival and Paracrine Effects

Background: The poor engraftment of mesenchymal stem cells (MSCs) in the ischemic heart post transplantation heavily restricts their cardioprotective benefits in myocardial infarction (MI). Pretreatment has emerged as a novel approach to enhance the biological properties of MSCs and enhance their therapeutic efficacy. This study aimed to determine whether pretreatment of MSCs with fibroblast growth factor 21 (FGF21) could promote their cardioprotective effects in mice with MI and illustrate the potential mechanisms.Methods: FGF21-pretreated MSCs (FGF21-MSCs) or MSCs were subjected to serum deprivation and hypoxia (SD/H) for 48 h. Apoptosis and proliferation of MSCs or FGF21-MSCs under SD/H were assessed using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and Ki67 staining, respectively. The conditioned medium (CdM) of MSCs and FGF21-MSCs was harvested by centrifugation. Left anterior descending coronary artery (LAD) ligation served to establish an MI model in mice and then MSCs or FGF21-MSCs intramyocardially injected into the peri-infarct area. Four weeks later, cardiac function, fibrosis and MSC engraftment in ischemic heart tissue were determined by echocardiography, Masson’s and immunofluorescence staining, respectively.Results: FGF21 pretreatment greatly inhibited apoptosis (p < 0.001) and elevated the proliferation (p < 0.05) of MSCs subjected to SD/H. Pretreatment with FGF21 enhanced the paracrine activity of MSCs, as evidenced by increased tube formation in HUVECs (human umbilical vein endothelial cells) (p < 0.001). Moreover, treatment with FGF21-MSC-CdM further alleviated SD/H-induced cardiomyocyte apoptosis (p < 0.05). Mechanistically, FGF21 pretreatment enhanced MSC survival under SD/H via activation of the AMPK signaling pathway by enhancing liver kinase B1 (LKB1) stability, an effect that was largely reversed by AMPK inhibitor Compound C. In the murine MI model, transplantation of FGF21-preconditioned MSCs resulted in superior cardiac recovery, accompanied by enhanced neovascularization (p < 0.001) and decreased cardiac apoptosis (p < 0.001). Importantly, FGF21 pretreatment significantly increased the persistence of human mitochondrial signaling in the infarcted heart (p < 0.001).Conclusions: FGF21 pretreatment significantly improved the cardioprotective efficacy of MSCs on MI via elevation of their survival and paracrine effects, providing a novel therapeutic approach to improve MSC therapy for heart repair following infarction.