In Vivo Functional Selection Identifies Cardiotrophin-1 as a Cardiac Engraftment Factor for Mesenchymal Stromal Cells
Background—Transplantation of cells into the infarcted heart has significant potential to improve myocardial recovery; however, low efficacy of cell engraftment still limits therapeutic benefit. Here we describe a method for the unbiased, in vivo selection of cytokines that improve mesenchymal stromal cell (MSC) engraftment into the heart in both normal conditions and after myocardial infarction.
Methods—An arrayed library of 80 secreted factors, including most of the currently known interleukins and chemokines, were individually cloned into adeno-associated viral (AAV) vectors. Pools from this library were then used for the batch transduction of bone marrow-derived MSCs ex vivo, followed by intra-myocardial cell administration in normal and infarcted mice. Three weeks after injection, vector genomes were recovered from the few persisting cells and identified by sequencing DNA barcodes uniquely labeling each of the tested cytokines.
Results—The most effective molecule identified by this competitive engraftment screening was cardiotrophin 1 (Ctf1), a member of the IL6 family. Intra-cardiac injection of MSCs transiently pre-conditioned with Ctf1 preserved cardiac function and reduced infarct size, parallel to the persistence of the transplanted cells in the healing hearts for at least two months after injection. Engraftment of Cft1-treated MSCs was consequent to STAT3-mediated activation of the focal adhesion kinase (FAK) and its associated focal adhesion complex and the consequent acquisition of adhesive properties by the cells.
Conclusions—These results support the feasibility of selecting molecules in vivo for their functional properties using AAV vector libraries and identify Ctf1 as a powerful cytokine promoting cell engraftment and thus improving cell therapy of the infarcted myocardium.
- Received April 17, 2017.
- Revision received June 15, 2017.
- Accepted July 12, 2017.