Stem cell viability and proliferation is maintained in vivo using an alginate patch designed for epicardial administration

Background \u0026 Aim Cell-based therapies for the regeneration of the heart have demonstrated clinical safety but failed to show efficacy. This was attributed to poor cell retention and low integration of the cells into the tissue. We aim at developing a cardiac patch that will preserve cell viability and deliver functional cells into the heart. Methods, Results \u0026 Conclusion We employed the cryo-gelation method for the cross-linking of methacrylate alginate patches using free radical polymerization. Epicardial cells derived from human embryonic stem cells (epi-hESC) on differentiation day 12 were seeded on the patch. Their in vitro viability (Alamar blue proliferation assay, confocal imaging by the LIVE/DEAD® staining) and migratory potential were assessed over time. Patches loaded with luciferase-expressing mouse mesenchymal stem cells (mMSC) were injected subcutaneously in the dorsal area of BALB/c mice. Cells were monitored in vivo by bioluminescence and cell integration in the muscle was assessed by histology. An ultrasound guided injection method in the pericardial space of rodents was developed and cell-loaded radiolabelled patches were administered on the heart of BALB/c mice. The patches and the cells were monitored over 7 days using SPECT and bioluminesce. The patches were successfully seeded with 20’000 per mm2 epi-hESC. The cells formed clusters that were homogenously distributed within the patch, and their viability and proliferation were preserved over 4 days in vitro. The cells acquired a spindle shape migratory morphology by day 5. When administered in mice, the patch deployed and adhered on the dorsal muscle. The mMSC loaded in the patch survived in vivo over more than 8 days. When administered in the pericardial space of the rat, the patch deployed and remained confined between the pericardium and the surface of the heart. The viability of stem cell-derived somatic cells can be preserved in vivo using shape memory alginate scaffolds. These cardiac cells could enhance cardiac regeneration through paracrine signalling or integration of the cells in the heart.