Angiopoietin-1 treated early endothelial outgrowth cells (eEOCs) are activated in vitro and reduce renal damage in murine acute ischemic kidney injury (iAKI).

BACKGROUND: Acute kidney injury (AKI) severely worsens prognosis of hospitalized patients. Early Endothelial Outgrowth Cells act protective in murine acute ischemic renal failure and renoprotective actions of eEOCs have been documented to increase after cell pretreatment with 8-O-cAMP and Melatonin. Angiopoietin-1 is critically involved in maintaining vascular integrity and regeneration. Aim of the study was to analyze the consequences of eEOC treatment with Ang-1 in murine AKI. METHODS: After 40 minutes of unilateral renal artery clamping with contralateral nephrectomy, male C57/Bl6N mice were injected with either untreated or pretreated (Ang-1) syngeneic murine eEOCs. Two days later serum creatinine levels and morphology were evaluated. Cultured, Ang-1 treated murine eEOCs were analyzed for production/release of proangiogenic and proinflammatory mediators, migratory activity, and cell survival, respectively. RESULTS: Angiopoietin-1 pretreatment of eEOCs significantly reduced serum creatinine in cell-injected mice. In vitro analysis showed increased migration of Ang-1 treated eEOCs and supernatant from Ang-1 treated eEOCs stimulated migration of cultured mature endothelial cells. In addition, Ang-1 reduced percentages of Annexin V+/PI+ eEOCs. Intrarenal numbers of eEOCs remained unaffected by Ang-1 and eEOCs did not produce more or less proangiogenic/proinflammatory mediators after being stimulated with Ang-1. CONCLUSIONS: Angiopoietin-1 pretreatment of eEOCs increases the cells' renoprotective competence in ischemic AKI. Thus, the armentarium of eEOC agonists in AKI is increasingly being expanded and the treatment of AKI with eEOCs becomes a promising future option.

Angiopoietin-2 modulates eEOC-mediated renoprotection in AKI in a dose-dependent manner.

BACKGROUND: Early endothelial outgrowth cells (eEOCs) significantly protect mice from acute kidney injury (AKI). Angiopoietin-2 (Ang-2) has been shown to be critically involved in vascular repair and homeostasis. The aim of this study was to investigate consequences of Ang-2 treatment of syngeneic murine eEOCs in a cell-based therapeutic approach for AKI. METHODS: Male 8- to 12-week-old C57/Bl6N mice, subjected to unilateral renal ischemia (40 minutes) postuninephrectomy were systemically injected with 0.5 × 10(6) untreated or Ang-2-pretreated syngeneic murine eEOCs. Renal function and morphology were analyzed 48 hours later. Cellular consequences of eEOC treatment with Ang-2 were evaluated using different in vitro assays (direct and indirect migration, apoptosis/necrosis, ELISA studies). RESULTS: Administration of untreated eEOCs did not protect mice from AKI. Ang-2 dose-dependently modulated cell effects in AKI. While incubating the cells at a concentration of 200 ng/mL (1 hour) did not have any effect on renal function, doubling the concentration (400 ng/mL) resulted in significant renoprotection of cell-injected mice. With 800 ng/mL, cell injection dramatically worsened renal function of treated animals. In vitro analysis showed significantly accelerated migration of cultured mature endothelial cells after incubation with supernatant from Ang-2-treated eEOCs (200 and 400 ng/mL). These effects were most pronounced with 400 mg/mL. In addition, Ang-2 promoted survival of eEOCs. Cellular releases of VEGF and IL-6 were decreased by Ang-2, while TGF-ß levels in the medium of Ang-2-stimulated eEOCs were not different from those in untreated cells. CONCLUSION: Ang-2 acts as modulator of eEOCs in AKI. The migration analysis indicates that the Ang-2 significantly alters indirect (paracrine) activity of eEOCs, thus promoting renoprotection in a dose-dependent manner.