Regulation of circulating progenitor cells in left ventricular dysfunction

Abstract

Background: Reductions in numbers of circulating progenitor cells (CD34+ cell subsets) have been demonstrated in patients at risk for, or in the presence of, cardiovascular disease. The mediators of these reductions remain undefined. To determine whether neurohumoral factors might regulate circulating CD34+ cell subsets in vivo, we studied complementary canine models of left ventricular (LV) dysfunction.

Methods and results: A pacing model of severe LV dysfunction and a hypertensive renal wrap model in which dogs were randomized to receive deoxycorticosterone acetate (DOCA) were studied. Circulating CD34+ cell subsets including hematopoietic precursor cells (HPCs: CD34+/CD45(dim)/VEGFR2-) and endothelial progenitor cells (EPCs: CD34+/CD45-/VEGFR2+) were quantified. Additionally, the effect of mineralocorticoid excess on circulating progenitor cells in normal dogs was studied. The majority of circulating CD34+ cells expressed CD45dimly and did not express VEGFR2, consistent with an HPC phenotype. HPCs were decreased in response to pacing, and this decrease correlated with plasma aldosterone levels (Spearman rank correlation=-0.67, P=0.03). In the hypertensive renal wrap model, administration of DOCA resulted in decreased HPCs. No changes were seen in EPCs in either model. Normal dogs treated with DOCA exhibited a decrease in HPCs in peripheral blood but not bone marrow associated with decreased telomerase activity.

Conclusions: This is the first study to demonstrate that mineralocorticoid excess, either endogenous or exogenous, results in reduction in HPCs. These data suggest that mineralocorticoids may induce accelerated senescence of progenitor cells, leading to their reduced survival and decline in numbers.

Figure 1

A: Hematopoietic (HPC) and B: endothelial progenitor cell (EPC) counts in a canine pacing model of LV dysfunction. Cells were enumerated from paced dogs at baseline and at 10 days and compared using a Wilcoxon signed-rank test. Cell counts are expressed as a % of total leukocytes.

Figure 2

Effects of renal wrapping (RW) and deoxycorticosterone acetate (DOCA) on progenitor cell counts. Hematopoietic and endothelial progenitor cell counts over time with regression analysis for the effect of DOCA therapy with the mean of pretreatment values as covariate. (A) HPC and (B) EPC counts as % of total leukocytes.

Figure 2

Effects of renal wrapping (RW) and deoxycorticosterone acetate (DOCA) on progenitor cell counts. Hematopoietic and endothelial progenitor cell counts over time with regression analysis for the effect of DOCA therapy with the mean of pretreatment values as covariate. (A) HPC and (B) EPC counts as % of total leukocytes.

Figure 3

Effects of DOCA administration on peripheral and bone marrow progenitor cells. A. DOCA administration did not affect peripheral blood or circulating CD45+ cell counts. B. HPC and EPC counts in buffy coat extracted from peripheral blood and C. from bone marrow in uninstrumented normal dogs pre and post 10 days of treatment with DOCA at a dose of 1mg/kg administered once daily intramuscularly. Analysis is by Wilcoxon signed rank test.

Figure 3

Effects of DOCA administration on peripheral and bone marrow progenitor cells. A. DOCA administration did not affect peripheral blood or circulating CD45+ cell counts. B. HPC and EPC counts in buffy coat extracted from peripheral blood and C. from bone marrow in uninstrumented normal dogs pre and post 10 days of treatment with DOCA at a dose of 1mg/kg administered once daily intramuscularly. Analysis is by Wilcoxon signed rank test.

Figure 3

Effects of DOCA administration on peripheral and bone marrow progenitor cells. A. DOCA administration did not affect peripheral blood or circulating CD45+ cell counts. B. HPC and EPC counts in buffy coat extracted from peripheral blood and C. from bone marrow in uninstrumented normal dogs pre and post 10 days of treatment with DOCA at a dose of 1mg/kg administered once daily intramuscularly. Analysis is by Wilcoxon signed rank test.

Figure 4

Detection of mineralocorticoid receptor (MR) expression. A. rt-PCR for MR in peripheral blood buffy coat from normal dogs. B. FACS of canine peripheral blood for CD34 and MR (R1=CD34+) (R2= CD34+/MR+). C. Co-localization of CD34 (red, cytoplasmic staining) and MR (green, nuclear staining) in canine bone marrow. Arrow indicates cell expressing CD34 and MR.

Figure 5

DOCA decreases telomerase activity in CD34+ cells. Telomerase activity in lysed CD34+ cells extracted from peripheral blood at Baseline and following 10 days of DOCA treatment. *p=<0.05, Student t-test.