(C-108) A localizable angiogenic vehicle for a myocardial recovery

Approximately 18 million Americans are affected annually from an acute myocardial infarction. Of this group, 20-40% suffer from consequential loss of function due to ischemia related necrosis and scar tissue formation of the affected heart muscle. To rescue the ischemia-affected tissue and mitigate the effects of acute injury, we have developed a self-assembling peptide hydrogel, termed SLan (KSLSLSLSLSLSLKGKLTWQELYQLKYKGI). When solvated in aqueous media, SLan serves as a thixotropic vehicle to promote regeneration of the heart tissue by mimicking Vascular Endothelial Growth Factor A (VEGFA). This hydrogel vehicle is being investigated for use to deliver cardiomyocytes to the affected wound area. We modeled its efficacy in rescuing insulted tissue with an acute myocardial infarction model. The results suggest a new methodology for both delivery and instruction of the cells to rescue and regenerate damaged tissue.

SLan was synthesized using solid phase peptide synthesis using FMOC chemistry. Purification was performed using high performance liquid chromatography, and identity of the amino acid sequence was performed using MALDI. The peptides were solvated at 2.88mM in isotonic phosphate buffered saline. Cardiomyocytes were purchased from ATCC and cultured under 5% CO2 until 70% confluency. The cells were removed from culture, centrifuged, and reloaded into the vehicle at a concentration of 1 million cells per mL of vehicle. The hydrogel was added with cells at a final concentration of 1M cells/ml and the rheological testing was performed. To test the cytocompatibility of the scaffolds a live dead assay was performed.  The acute myocardial infarction was induced by ligating the left anterior descending coronary artery of 25g C57BL/6 mice. The experimental groups were injected in the left ventricle below the ligation site. After 7 and 28 days, the mice were sacrificed, and the hearts explanted. Histology was performed with H&E, Masson’s Trichrome, and TUNEL / Caspase stains.

The cells showed excellent cytocompatibility over order of magnitude SLan addition in vitro. As well the rheology test resulted in a confirmation of the thixotropic nature of the gel and cell construct to be preserved. A significantly decreased heart wall thickness was observed with the SLan + cardiomyocytes vs. SLan alone, PBS vehicle, and cardiomyocytes alone. The results revealed the lowest level of apoptosis for sham and SLan+mESC at 7 days compared to PBS, SLan only, or cell-only scaffolds. This trend was significantly reduced in magnitude for all groups (except sham) at the 28-day timepoint.  These initial results suggest that localized growth factor mimicry may serve as a novel option for both delivery and localized cell response. In vitro studies support the hypothesis that growth factor mimicry can lead to advantageous cell growth in response to an acute injury. The in vivo myocardial infarction model suggests that these effects can be used for both local cell delivery and rescue from an acute ischemic event. This serves as a basis for further investigation into localized cytokine and growth factor localization and codelivery for mitigating chronic pathologies that result from an acute injury.