Therapeutic progenitor cell application for tissue regeneration: Analyzing the impact of toll-like receptor signaling on c-kit+ cell migration following ischemia-reperfusion injury in vivo

Abstract Objectives Toll-like-receptor (TLR) mediated immune response has been shown to regulate myocardial damage following cardiac ischemia-reperfusion (IR). It has not been described conclusively so far whether migration of therapeutically applied progenitor cells following an IR event depends on TLR-signaling. Methods In vivo migratory capacity murine c-kit + cells following IR injury was quantified by intravital fluorescence microscopy, utilizing the mouse cremaster muscle model and analyzing early (rolling) and late (adhesion) c-kit + cell interaction with the local endothelium. The role of TLR-2 and TLR-4, as well as MyD88 and TRIF was analyzed by applying specific knock-out models. Results A sequence of 15 min ischemia followed by 15 min of reperfusion induced firm endothelial c-kit + cell adhesion (5.6 ± 1.3 cells/mm 2 in Control vs. 30.2 ± 10.1 cells/mm 2 in IR , p IR induced early c-kit + cell-endothelial cell interactions (67.6 ± 2.3% c-kit + cell rolling in IR vs. 46.3 ± 4.8% c-kit + cell rolling in IR-TLR-2-ko vs. 45.3 ± 4.8% c-kit + cell rolling in IR-TLR-4-ko , p + cell adhesion (30.2 ± 10.1 cells/mm 2 in IR vs. 16.3 ± 3.9 cells/mm 2 in IR-TLR-2-ko vs. 14.5 ± 4.4 cells/mm 2 in IR-TLR-4-ko , p + cell adhesion only in MyD88 knock-out but not in TRIF knock-out (9.2 ± 2.2 cells/mm 2 in IR-MyD88-ko vs. 30.1 ± 9.9 cells/mm 2 in IR-WT , p Conclusion Artificially applied c-kit + cells interact with the target organ endothelium following IR injury. This interaction seems to depend on TLR-MyD88 signaling. Therapeutic blockade of TLR signaling for anti-inflammatory purposes might interfere with regenerative cell-based therapy protocols.