Abstract 1016: Regenerative Cellular Therapy: How To Enrich The Mesenchymal Stem Cell Content In The Periinfarction Zone After Myocardial Infarction
Background: The pluripotent capacity of adult mesenchymal stem cells (MSCs) makes this cell type a potential candidate for tissue regeneration after myocardial infarction (MI). However, the most effective route of MSC application and the impact of contributory cytokine enhancement remains to be elucidated.
Methods and Results: Murine CD90 + CD45-CD34-sca-1 + c-kit-MSCs were culture-expanded, stably transfected with firefly luciferase for bioluminescence imaging (BI), and labeled with CSFE for histology (H). High-throughput proteomics and a battery of in vitro and in vivo assays were used to profile 20 key cardiac-specific cytokines upregulated following MI for their effects on the biologic performance of MSCs. VEGF and HGF showed most effective enhancement of MSC proliferation, migration, and trans-membrane invasion. After LAD ligation, syngeneic mice received intraperitoneal (IP), intravenous (IV) or intramyocardial (IC) MSC injections. The development of cardiac MSC content was closely monitored by in vivo BI and H. Cytokine enhancement (CE) protocol: VEGF 8ng/ml and HGF 40ng/ml were injected into the infarction border zone to attract MSCs to the heart (after IV- or IP-injection) or to retain them in the heart (after IC-injection). 1 day after IP injection, a maximum of only 0.4 ± 0.5 cells/HPF was detected in the heart. Most IP-injected MSCs failed to be absorbed and enter the circulation. They rapidly decayed to <10% within the peritoneum over 4 ± 2 days. Due to their large size (19um), huge amounts of IV-injected MSCs were trapped within the pulmonary capillaries, causing hemodynamic alterations if >106 cells were used. After 1 day, a maximum of 1 ± 0.5 cells/HPF was found in the heart and CE significantly increased the cell content to 6 ± 3 cells/HPF (p=0.020). IC-injected MSCs vanished rapidly and cell counts dropped to 32 ± 18% at 6 days and 9 ± 6% at 12 days. Interestingly, the CE protocol significantly prolonged intramyocardial MSC survival and preserved higher cell counts (125 ± 21% at 6 days, p<0.001 and 87 ± 31% at 12 days, p<0.001).
Conclusions: The most effective route of MSC application seems to be direct injection into the heart combined with cytokine enhancement in the border zone to create a beneficial microenviroment for cell survival.