Number and Replating Capacity of Endothelial Colony-Forming Cells are Telomere Length Dependent: Implication for Human Atherogenesis

Abstract

Background Short leukocyte telomere length (TL) is associated with atherosclerotic cardiovascular disease. Endothelial repair plays a key role in the development of atherosclerosis. The objective was to examine associations between TL and proliferative dynamics of endothelial colony-forming cells (ECFCs), which behave as progenitor cells displaying endothelial repair activity. Methods and Results To isolate ECFCs, we performed a clonogenic assay on blood samples from 116 participants (aged 24-94 years) in the TELARTA (Telomere in Arterial Aging) cohort study. We detected no ECFC clones in 29 (group 1), clones with no replating capacity in other 29 (group 2), and clones with replating capacity in the additional 58 (group 3). Leukocyte TL was measured by Southern blotting and ECFCs (ECFC-TL). Age- and sex-adjusted leukocyte TL (mean±SEM) was the shortest in group 1 (6.51±0.13 kb), longer in group 2 (6.69±0.13 kb), and the longest in group 3 (6.78±0.09 kb) (P<0.05). In group 3, ECFC-TL was associated with the number of detected clones (P<0.01). ECFC-TL (7.98±0.13 kb) was longer than leukocyte TL (6.74±0.012 kb) (P<0.0001) and both parameters were strongly correlated (r=0.82; P<0.0001). Conclusions Individuals with longer telomeres display a higher number of self-renewing ECFCs. Our results also indicate that leukocyte TL, as a proxy of TL dynamics in ECFCs, could be used as a surrogate marker of endothelial repair capacity in clinical and laboratory practice because of easy accessibility of leukocytes. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02176941.

Keywords: aging; endothelial progenitor cell; telomere.

Figure 1. Classification of the subjects according to endothelial colony‐forming cells detectability and replating capacity.

ECFCs indicates endothelial colony‐forming cells; and PBMC, peripheral blood mononuclear cells.

Figure 2. Leukocyte telomere length and endothelial colony‐forming cells detectabity and replating capacity.

Age‐ and sex‐adjusted leukocyte telomere length values in the 3 groups. Black lines and crossbars represent mean±SD, circles represent individual values, and P is from trend ANOVA. ECFCs indicates endothelial colony‐forming cells; and LTL, leukocyte telomere length.

Figure 3. Endothelial colony‐forming cells‐telomere length and number of clones.

Number of endothelial colony‐forming cell clones obtained from culture of peripheral blood mononuclear cells according to endothelial colony‐forming cells‐telomere length. R ² and P are from Pearson correlation. ECFCs indicates endothelial colony‐forming cells; ECFC‐TL, endothelial colony‐forming cells telomere length; and PBMC, peripheral blood mononuclear cells.

Figure 4. Endothelial colony‐forming cells‐telomere length and circulating von Willebrand factor levels.

Relationship between plasmatic levels of von Willebrand factor and ECFC‐TL (n=52). R ² and P are from Pearson correlation. ECFC‐TL indicates endothelial colony‐forming cells‐telomere length; and VWF, von Willebrand factor.

Figure 5. Relationship between endothelial colony‐forming cells‐telomere length (ECFC‐TL), muscle telomere length, and leukocyte telomere length.

A, Mean and individual values of muscle telomere length, ECFC‐TL, and leukocyte telomere length (n=52). Value are expressed as mean±SD (kb) and P are from paired t tests. B, Relationship between ECFC‐TL and leukocyte telomere length. R ² and P are from Pearson correlation. C, Relationship between ECFC‐TL and muscle telomere length. R ² and P are from Pearson correlation. ECFC‐TL indicates endothelial colony‐forming cells‐telomere length; LTL, leukocyte telomere length; and MTL, muscle telomere length.