Abstract 708: Platelet Derived Growth Factor-Beta Communication Axis is Critical for Mediating Pericyte-Endothelial Cell Interactions and Angiogenic Support in Combination Therapy of Human Umbilical Cord Perivascular Cells and Endothelial Progenitor Cells

Abstract

Introduction: First Trimester Human Umbilical Cord Perivascular Cells (FTM HUCPVC) have higher cardiovascular regenerative potential compared to older sources of MSC. We designed a cell combination therapy with FTM HUCPVC and endothelial progenitor cells (EPC) to enhance angiogenesis after MI. However, the mechanism of PVC-EPC interaction is unclear. Hypothesis: Platelet derived growth factor beta receptor (PDGFB-R) expression of HUCPVC mediates homing and integration with endothelial networks and required for supporting neovasculature. Methods: Expression of pericyte markers PDGFB-R and CD146 of xeno-free expanded (HPL 2.5%) FTM and term HUCPVC was analyzed by flow cytometry. PDGFB-driven trans-ECM migration was assessed by Corning Biocoat Invasion assay with 1-100 ng/ml PDGFB. siRNA for PDGFB-R, CD146 and scrambled control was used with lipofectamine for 72 hours. Silencing was confirmed by qPCR and flow cytometry. 10% HPL was used for PDGFB-R desensitization. HUCPVC of all treatment groups were co-cultured with EPC and rat aortic rings on Matrigel TM . Cell migration, endothelial adhesion and network properties were quantified. Statistics: one-way ANOVA N=5 Results: PDGFB-R and CD146 expression and endothelial network augmenting function of FTM HUCPVC was significantly higher than of term HUCPVC. PDGFB dependent migration of FTM HUCPVC was disabled by both ligand (<10%) and siRNA-based (<5%) downregulation of PDGFB-R. Fluorescence microscopy (24 h) showed limited homing and endothelial interactions of PDGFB-R-reduced FTM HUCPVC. PDGFB-R-reduced FTM HUCPVC had significantly decreased network growth and nodes ( p <0.0001) compared to control groups (day3). In EPC co-cultures, PDGFB-R-reduced FTM HUCPVC had limited endothelial interactions and coverage compared to control FTM HUCPVC. PDGFB-R-reduced FTM HUCPVC treated networks had significantly thinner ( p <0.001) and shorter tubules ( p <0.001) compared to control FTM HUCPVC groups. Down-regulation of C146 did not alter FTM HUCPVC pericyte properties. Conclusions: PDGFB-R is crucial for the homing and endothelial support of HUCPVC. This interaction is critical in vascular cell combination therapies and PDGFB-R expression can be a novel criterion for cardiovascular cell therapy.