Tadalafil, a long acting phosphodiesterase inhibitor, promotes bone marrow stem cell survival and their homing into ischemic myocardium for cardiac repair.

The aim was to evaluate the tadalafil-mediated effects at molecular level on bone marrow-derived mesenchymal stem cells (MSCs) survival and their homing into the infarcted hearts to promote cardiac repair and improve function. 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 h. 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. 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. CONCLUSIONS: 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.

Optimization of in vitro vascular cell transfection with non-viral vectors for in vivo applications.

BACKGROUND: Syngeneic vascular cells are interesting tools for indirect gene therapy in the cardiovascular system. This study aims to optimize transfection conditions of primary cultures of vascular smooth muscle cells (VSMCs) using different non-viral vectors and zinc as an adjuvant and to implant these transfected cells in vivo. METHODS: Non-liposomal cationic vectors (FuGene 6), polyethylenimines (ExGen 500), and histidylated polylysine (HPL) were used as non-viral vectors in vitro with secreted alkaline phosphatase (SEAP) as reporter gene. Transfection efficiency was compared in cultured rat, rabbit and human VSMCs and fibroblasts. Zinc chloride (ZnCl2) was added to optimize transfection of rat VSMCs in vitro which were then seeded in vivo. RESULTS: Much higher SEAP levels were obtained in rabbit cells with FuGene 6 (p <0.0001) at day 2 than in equivalent rat and human cells. Rat VSMCs transfected in vitro with FuGene 6 and ExGen 500 expressed higher SEAP levels than with HPL. In rat VSMCs, SEAP secretion was more than doubled by addition of 250 microM ZnCl2 (p <0.0001) for all vectors. Seeding of syngeneic VSMCs transfected under optimized conditions (FuGene 6/pcDNA3-SEAP +250 microM ZnCl2) into healthy Lewis rats using various routes or into post-infarct myocardial scar resulted in a peak of SEAP expression at day 2 and detectable activity in the plasma for at least 8 days. CONCLUSIONS: FuGene 6 is an efficient non-viral transfection reagent for gene transfer in somatic smooth muscle cells in vitro and ZnCl2 enhances its efficiency. This increased expression of the transgene product is maintained after seeding in vivo.