Nocturnal hemodialysis is associated with restoration of early-outgrowth endothelial progenitor-like cell function

Abstract

Background and objectives: Angiogenesis is a key response to tissue ischemia that may be impaired by uremia. Although early-outgrowth endothelial progenitor-like cells promote angiogenesis in the setting of normal renal function, cells from uremic patients are dysfunctional. When compared with conventional hemodialysis, it was hypothesized that nocturnal hemodialysis would improve the in vivo angiogenic activity of these cells in a well described model of ischemic vascular disease.

Design, setting, participants, and measurements: Early-outgrowth endothelial progenitor-like cells were cultured from healthy controls (n = 5) and age- and gender-matched conventional hemodialysis (12 h/wk, n = 10) and nocturnal hemodialysis (30 to 50 h/wk, n = 9) patients. Cells (5 × 10(5)) or saline were injected into the ischemic hindlimb of athymic nude rats 1 day after left common iliac artery ligation.

Results: Although conventional dialysis cell injection had no effect versus saline, nocturnal hemodialysis and healthy control cell injection significantly improved ischemic hindlimb perfusion and capillary density. Nocturnal hemodialysis cell injection was also associated with significant increases in endogenous angiopoietin 1 expression in the ischemic hindlimb compared with saline and conventional dialysis cell injection.

Conclusions: In contrast to a conventional dialytic regimen, nocturnal hemodialysis is associated with a significantly improved ability of early-outgrowth endothelial progenitor-like cells to promote angiogenesis and thus restore perfusion in a model of ischemic vascular disease.

Figure 1.

Microvascular perfusion of ischemic hindlimb tissue is improved 27 days after injection of early-outgrowth endothelial progenitor-like cells (EPLCs) from nocturnal hemodialysis (NHD) patients. (A) Representative contrast-enhanced ultrasound perfusion images of ischemic hindlimb muscle at increasing pulsing intervals from one animal in each of the four treatment groups at 4 weeks postligation. Contrast enhancement into ischemic skeletal muscle was greater and occurred faster in muscle treated with early-outgrowth EPLCs derived from healthy controls and NHD patients as compared with muscle treated with saline (negative control), whereas early-outgrowth EPLCs derived from conventional thrice weekly hemodialysis (CHD) patients had no beneficial effect when compared with saline. (B) Microvascular blood flow ratio. (C) Microvascular blood volume ratio. Results are presented as ratios of ischemic hindlimb to nonischemic hindlimb control. *P < 0.05 versus saline-treated animal. †P < 0.05 versus healthy early-outgrowth EPLC-treated animal. ‡ P < 0.05 versus NHD early-outgrowth EPLC-treated animal.

Figure 2.

Correlation between dialysis dose and microvascular perfusion. Correlation analysis between dialysis dose as measured by eKt/V and (A) microvascular blood flow ratio and (B) microvascular blood volume ratio.

Figure 3.

Capillary density. Ischemic hindlimb sections were stained with isolectin B4 4 weeks postligation to identify endothelial cells. (A through D) Representative ischemic hindlimb muscle images. Original magnification: ×160. (A) Saline-treated animal. (B) Healthy early-outgrowth EPLC-treated animal. (C) CHD early-outgrowth EPLC-treated animal. (D) NHD early-outgrowth EPLC-treated animal. (E) Capillary density (number of capillaries per 100× field) in the ischemic hindlimb. *P < 0.05 versus saline-treated animal. †P < 0.05 versus healthy early-outgrowth EPLC-treated animal. ‡P < 0.05 versus NHD early-outgrowth EPLC-treated animal.

Figure 4.

Correlation between dialysis dose and capillary density. Correlation analysis between dialysis dose as measured by eKt/V and ischemic hindlimb capillary density.