Background: The beneficial functions of bone marrow mesenchymal stem cells (BM-MSCs) decline with decreased cell survival, limiting their therapeutic efficacy for myocardial infarction (MI). Irisin, a novel myokine which is cleaved from its precursor fibronectin type III domain-containing protein 5 (FNDC5), is believed to be involved in a cardioprotective effect, but little was known on injured BM-MSCs and MI repair yet. Here, we investigated whether FNDC5 or irisin could improve the low viability of transplanted BM-MSCs and increase their therapeutic efficacy after MI.
Methods: BM-MSCs, isolated from dual-reporter firefly luciferase and enhanced green fluorescent protein positive (Fluc+-eGFP+) transgenic mice, were exposed to normoxic condition and hypoxic stress for 12 h, 24 h, and 48 h, respectively. In addition, BM-MSCs were treated with irisin (20 nmol/L) and overexpression of FNDC5 (FNDC5-OV) in serum deprivation (H/SD) injury. Furthermore, BM-MSCs were engrafted into infarcted hearts with or without FNDC5-OV.
Results: Hypoxic stress contributed to increased apoptosis, decreased cell viability, and paracrine effects of BM-MSCs while irisin or FNDC5-OV alleviated these injuries. Longitudinal in vivo bioluminescence imaging and immunofluorescence results illustrated that BM-MSCs with overexpression of FNDC5 treatment (FNDC5-MSCs) improved the survival of transplanted BM-MSCs, which ameliorated the increased apoptosis and decreased angiogenesis of BM-MSCs in vivo. Interestingly, FNDC5-OV elevated the secretion of exosomes in BM-MSCs. Furthermore, FNDC5-MSC therapy significantly reduced fibrosis and alleviated injured heart function.
Conclusions: The present study indicated that irisin or FNDC5 improved BM-MSC engraftment and paracrine effects in infarcted hearts, which might provide a potential therapeutic target for MI.
Keywords: Apoptosis; Bone marrow mesenchymal stem cells (BM-MSCs); Cell viability; Fibronectin type III domain-containing protein 5 (FNDC5); Irisin; Myocardial infarction (MI).