Growth and function of equine endothelial colony forming cells labeled with semiconductor quantum dots

Randolph L Winter,Yuan Tian,Elizabeth A Lipke,Anne A Wooldridge,Fred J Caldwell,Wen J Seeto

doi:10.1186/s12917-018-1572-3

Abstract

BackgroundEndothelial progenitor cells (EPCs) contribute to neovascularization and vascular repair in vivo and are attractive for clinical use in ischemic disease. Tracking of stem and progenitor cells is essential to determine engraftment after administration. Semiconductor quantum dots (QD) are promising for cell labeling due to their ease of uptake by many cell lines and their continued presence after many cell generations. The purpose of this study was to evaluate function and growth of equine EPCs after QD labeling. Additionally, this study evaluated the duration of QD label retention and mechanisms of QD label loss.ResultsEndothelial colony forming cells (ECFCs) from adult horses (N = 3) were employed for this study, with QD labeled and unlabeled ECFCs tested from each horse. Cell proliferation of ECFCs labeled with QD at 20 nM was quantified by comparing the number of cell doublings per day (NCD) and the population doubling time (PDT) in labeled and unlabeled cells. Function of labeled and unlabeled ECFCs was assessed by comparing uptake of acetylated low-density lipoprotein (DiO-Ac-LDL) and tubule formation on growth factor containing matrix. Cell proliferation was not impacted by QD labeling; both NCD (p = 0. 95) and PDT (P = 0. 91) did not differ between unlabeled and QD labeled cells. Function of ECFCs assessed by DiO-Ac-LDL and tubule formation was also not different between unlabeled and QD labeled cells (P = 0. 33 and P = 0. 52, respectively). ECFCs retained their QD labeling over 7 passages with both 5 nM and 20 nM label concentrations. Reduction in label intensity was observed over time, and the mechanism was determined to be cell division.ConclusionsEquine ECFCs are effectively labeled with QD, and QD concentrations up to 20 nM do not affect cell growth or function. QD label loss is a result of cell division. The use of QD labeling with equine EPCs may be an ideal way to track engraftment of EPCs for in vivo applications.

Highlights

Endothelial progenitor cells (EPCs) contribute to neovascularization and vascular repair in vivo and are attractive for clinical use in ischemic disease
number of cell doublings per day (NCD), population doubling time (PDT), and cumulative population doubling level (CPDL) data were assessed in quantum dots (QD) labeled P4 – P10 Endothelial colony forming cells (ECFCs) for all horse cell lines (N = 3)
NCD for unlabeled ECFCs were not significantly different compared to QD-labeled ECFCs (P = 0.95), indicating that QD label did not affect the NCD

Summary

Introduction

Endothelial progenitor cells (EPCs) contribute to neovascularization and vascular repair in vivo and are attractive for clinical use in ischemic disease. Multiple types of cell labeling strategies have been employed for in vitro and in vivo tracking including cell transduction with subsequent green fluorescent protein expression, superparamagnetic iron oxide (SPIO) nanoparticles, and QD nanocrystals [9,10,11]. QD labeling has gained prevalence for use and has been used in many different cell types (including human endothelial progenitor cells) and species [2,3,4, 7]. In another study of mouse embryonic stem cells labeled with QD, a loss of QD label was suggested to occur from either cell division or leaking of the label from the cell [9, 12]. A study using human endothelial progenitor cells suggested that QD label loss occurred primarily from cell division [7]

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