Abstract 18790: Identification of a Novel Regulator of the Mesenchymal Stem Cell Secretome and Myocardial Repair
The delivery of mesenchymal stem cells (MSC) in acute myocardial infarction (AMI) leads to significant preservation of myocardium and improved cardiac function. We have previously shown that the down-regulation of the tumor suppressor protein disabled-2 (Dab2) leads to increased MSC function in AMI. We sought to define the molecular mechanisms associated with down-regulation of disabled-2 and improved MSC function. We observed that the improvement in cardiac function following engraftment of Dab2-/- MSC was associated with modulation of the MSC secretome, in that of conditioned media conferred the same benefits as cell transplantation. To begin to define the down-stream targets of disabled-2 we completed a detailed Illumina array comparing Dab2 down-regulation by three methods (MSC treated with TGFß1 or MSC transfected with miR-145 or dab2:siRNA). Comparing gene expression in these three treatment groups to control MSC we identified 23 genes whose expression were similarly significantly modulated by dab2 down-regulation. Of this group we have focused to date on CAMKK1 as a possible regulator of the MSC secretome. CAMKK1, is a kinase with multiple down-stream targets including CAMK1, CAMKIV and Akt. Inhibition of CAMKK1 leads to an increase in pro-inflammatory cytokines and chemokines in the conditioned media of MSC. To determine if CAMKK1 over-expression was sufficient to induce an MSC like benefit in AMI we generated a plasmid vector in which CAMKK1 expression is regulated by the CMV promoter and the 5’-UTR RU5 enhancer element. We performed randomized blinded study in an AMI model in Sprague Dawley rats in which 500 ug of plasmid encoding CAMKK1 in 5 divided doses was injected into the infarct borderzone immediately after LAD ligation. CAMKK1 over-expression led to a significant improvement in cardiac function at 1, 2 and 8 weeks after AMI (Ejection Fraction at 8 weeks: CAMKK1: 83.2%±5.4% vs. Placebo: 51.7%±5.8%, p<0.0001, baseline: 91.3%±4.3%). These data suggest that CAMKK1 is a key molecular regulator of the MSC secretome, and that the benefits associated with MSC therapy can be achieved through the direct over-expression of CAMKK1.
Author Disclosures: F. Dong: None. M. Kiedrowski: None. M. Penn: None. M.E. Mayorga: None.
- © 2015 by American Heart Association, Inc.