Oral Communications 4
9.3 - Heterogeneity and the role of aging in the activation of Isl1+ endogenous cardiovascular progenitor cell clones isolated from human neonates and adults
Presenter: Eric, Tsay, Riverside, United States
Authors: Eric Tsay1,2, Tania Fuentes1,2, Nancy Appleby1,2, Hsiao-Yun Yeh1,2, Leonard Bailey1,2, N. Hasaniya1,2, Mary Kearns-Jonker1,2
Heterogeneity and the role of aging in the activation of Isl1+ endogenous cardiovascular progenitor cell clones isolated from human neonates and adults
Eric Tsay1,2, Tania Fuentes1,2, Nancy Appleby1,2, Hsiao-Yun Yeh1,2, Leonard Bailey1,2, N. Hasaniya1,2, Mary Kearns-Jonker1,2
1Department of Pathology and Human Anatomy, Loma Linda University School of Medicine, Loma Linda, CA, United States; 2Department of Cardiothoracic Surgery, Loma Linda University School of Medicine, Loma Linda, CA, United States
Introduction: Paracrine effects are largely responsible for the improvements in cardiac function that have been achieved with stem cell-based therapies. Insulin-like growth factor-1 (IGF-1) and SDF-1 have been well-documented for their ability to promote cardiovascular cell growth, migration and regeneration. The beneficial effects of these growth factors when administered without a cell type capable of cardiovascular regeneration are transient. Successful stem cell-based therapy will thus require an understanding of how growth factors promote cellular expansion in order to optimize their function towards maximal cardiac regeneration.
Hypothesis: Signaling is impaired in cardiovascular progenitor cells isolated from the aged adult population, rendering them less responsive to growth factors that stimulate migration to the site of injury.
Methods: Our laboratory isolated 264 clones of human neonatal and adult cardiovascular progenitor cells (CPCs) from patients undergoing cardiothoracic surgery, under IRB approval. These clones represent a unique resource for studying functional efficacy and early activation events in endogenous CPCs. Forty seven clones were selected for surface phenotype characterization using flow cytometry. Real time PCR was used to further distinguish the clones during differentiation into cardiac myocytes based on the expression of Isl1, MESP-1, c-kit and TropT. Differences in AKT cell signaling were identified in CPC clones in response to SDF-1 and IGF-1 by Western blotting. Invasion assays were also performed.
Results: Cardiovascular progenitor cell clones can produce both IGF-1 and SDF-1, factors that play a key role in cardiovascular repair. Functional differences were identified in the response of CPC populations to various growth factors. The response of Isl1+ c-kit+ co-expressing neonatal and adult CPCs to IGF-1 and SDF-1 was compared. Cardiomyocytes from neonates responded to IGF-1 treatment with a nearly two-fold increase in AKT phosphorylation while cells from the adult showed no response. Flow cytometry revealed that IGF-1 receptor levels were present on both neonatal and adult CPCs. Neonatal clones could be further distinguished by their differential response to SDF-1. The adult cells were not stimulated to invade in response to SDF-1 and there was no evidence of AKT activation, although the receptors were present on the cells as identified by flow cytometry.
Conclusions: Cardiovascular progenitor cells residing within the heart co-express Isl1 and c-kit. Neonatal CPCs produce and are activated by IGF-1 and SDF-1 and exist as a heterogeneous population. Age impacts cardiovascular progenitor cell signaling and may account for the inability of cardiovascular progenitor cells to mobilize to the site of injury and repair the heart in older adults.