MSCs were pretreated in vitro with inhibitors of PKG, MAPK, FasL, nitric oxide synthase (NOS) (L‐NAME), CXCR4 (AMD3100), or miR‐21 inhibitors (+/−luciferase construction +/−Fas) prior to tadalafil treatment for 2 hours. These MSCs were then subjected to H2O2 stress to assess their injury. Rats were subjected to acute myocardial infarction (AMI), and then followed by injection of saline or 1.5 x 106 MSCs-treated ± tadalafil into infarcted and peri-infarcted area. In another group, AMI was performed in 1-month post-myelo-ablated rats and were injected intraperitoneally (IP) with tadalafil ± AMD3100 or L‐NAME for 5 days. Also, in another group, AMI mice were treated with IP ± tadalafil before intravenous injection with 111In-oxine-MSCs followed by CT/SPECT imaging to locate mobilized MSCs.
Cardiac function was assessed by echocardiography. MSCs and heart extracts were analyzed by molecular bioassays, including miRNA microarray. Tadalafil-treated MSCs had higher expression of cGMP, NOS, SDF‐1α, p‐VASP, p‐Erk1/2, p‐STAT3, p‐Akt, PKG1 and Bcl‐xl; expression of these molecules was reduced with PKG1, MAPK, NOS or FasL inhibitors. Tadalafil inhibited apoptosis through increased miR-21 expression and improved cell survival by inhibiting Fas (restored by PKG1, MAPK or miR‐21 inhibitors). In vivo, heart function, grafted cell survival, MSCs mobilization and homing were improved in tadalafil-treated AMI animals versus controls.
The researchers conclude Tadalafil prolonged MSCs survival via up-regulation of miR-21 dependent suppression of Fas, and increased MSCs mobilization and their homing into infarcted myocardium resulting in improved cardiac repair and function.
Tadalafil increased miR‐21 expression of in vitro MSCs under oxidative stress. Tadalafil induced miR‐21 up‐regulation (microRNA‐array analysis, (A). miR‐21 expression was increased in MSCs‐treated by tadalafil versus control (B). RT‐PCR: miR‐21 expression bands; and quantitative analysis of miR‐21/U6 expression was assessed in ± MAPK (U0126) and PKG1 (KT5823) inhibitors (PCR‐gel bands and densitometry assay, (C). Values are mean ± SE; n = 6; P‐value <0.05 is significant.