Erythropoietin-enhanced endothelial progenitor cell recruitment in peripheral blood and renal vessels during experimental acute kidney injury in rats

Low-Dose Erythropoietin Amplifies Beneficial Effects of Angiotensin II Blockade on Glomerulosclerosis

Exogenous erythropoietin (EPO) is used to treat anemia in patients with chronic kidney disease (CKD). Concerns about the possible adverse effect of EPO on the progression of CKD have been raised owing to nonerythroid cell effects. We investigated the effects of low-dose EPO, independent of correcting anemia, on existing glomerulosclerosis. Adult mice underwent 5/6 nephrectomy and were randomized into the following 4 groups at week 8 after surgery: vehicle (VEH), losartan (angiotensin II type 1 receptor blocker [ARB]), darbepoetin-α (DA), or combination (DA+ARB). Four weeks later, mice were euthanized, followed by evaluation of renal structure and function. Glomerular endothelial cells and podocytes were cultured to evaluate the effects of DA on cell migration, apoptosis, and Akt signaling. ARB reduced blood pressure, albuminuria, and the level of serum creatinine and increased hematocrit compared with VEH, whereas low-dose DA only reduced the level of serum creatinine. Combination treatment showed a trend to increase hematocrit and survival compared with ARB alone. Combination treatment but not ARB alone significantly reduced the progression of glomerulosclerosis compared with VEH. Low-dose DA resulted in more preserved glomerular and peritubular capillary endothelial cells with increased p-Akt and even further endothelial cell preservation in combination with ARB. In cultured glomerular endothelial cells, angiotensin II induced more apoptosis, reduced migration, and decreased p-Flk1, a receptor for the proangiogenic vascular endothelial growth factor. DA counteracted these injuries and increased p-Akt, a key factor in angiogenesis and cell survival. DA also protected cultured podocytes against transforming growth factor β-induced apoptosis and synaptopodin loss. Low-dose EPO directly protects glomerular and peritubular endothelial cells via Akt phosphorylation. Therefore, treatment using a combination of low-dose EPO and ARB results in less progression of glomerulosclerosis in an experimental CKD model.

Stem/progenitor cell in kidney: characteristics, homing, coordination, and maintenance

Renal failure has a high prevalence and is becoming a public health problem worldwide. However, the renal replacement therapies such as dialysis are not yet satisfactory for its multiple complications. While stem/progenitor cell-mediated tissue repair and regenerative medicine show there is light at the end of tunnel. Hence, a better understanding of the characteristics of stem/progenitor cells in kidney and their homing capacity would greatly promote the development of stem cell research and therapy in the kidney field and open a new route to explore new strategies of kidney protection. In this review, we generally summarize the main stem/progenitor cells derived from kidney in situ or originating from the circulation, especially bone marrow. We also elaborate on the kidney-specific microenvironment that allows stem/progenitor cell growth and chemotaxis, and comment on their interaction. Finally, we highlight potential strategies for improving the therapeutic effects of stem/progenitor cell-based therapy. Our review provides important clues to better understand and control the growth of stem cells in kidneys and develop new therapeutic strategies.

Erythropoietin Preconditioning Mobilizes Endothelial Progenitor Cells to Attenuate Nephron-Sparing Surgery-Induced Ischemia-Reperfusion Injury

The purpose of this study was to examine the role of endothelial progenitor cells (EPCs) in protection against ischemic-reperfusion injury (IRI) in a nephron-sparing surgery (NSS) rat model using erythropoietin (EPO) preconditioning. Fifty-four male Sprague-Dawley rats were randomly divided into 3 groups for right kidney nephrectomy treatment: sham group (exposure without clamp treatment), NSS group (3 days of peritoneal phosphate buffered saline [PBS] injection before renal blood vessels were clamped for 40 mins and NSS was performed), and EPO group (3 days of EPO abdomen injections prior to renal blood vessel clamping for 40 min before NSS was performed). After 12, 24, and 72 hours, inferior vena cava blood and renal tissues were harvested. The extent of renal injury was assessed, along with EPC number, cell proliferation, angiogenesis, and vascular growth factor expression. EPO preconditioning significantly improved renal function and histologic morphology, indicated by reduced blood urea nitrogen (BUN) ([33.12 ± 1.88] vs [16.03 ± 0.91], P < .05) and serum creatinine (Scr) ([190.2 ± 20.23] vs [77.23 ± 5.82], P < .05) levels and histologic injury scores ([3.20 ± 0.78] vs [1.70 ± 0.67], P < .05). Angiogenesis in peritubular capillaries markedly increased in the EPO group. EPC numbers increased in the kidneys at 24 hours following reperfusion in the EPO group, compared to the NSS group. Furthermore, EPO preconditioning also increased SDF-1α and CXCR7 expression at 24 hours following reperfusion relative to the NSS group. These findings suggest that EPO pretreatment can reduce renal injury in rats caused by IRI. Mechanistically, this may be related to EPC mobilization and recruitment to injured renal tissues by SDF-1α and CXCR7.

Comparison of the excretory capacities of erythropoietin and U-74389G concerning serum creatinine levels

Introduction This study compared the excretory effects, the erythropoietin (Epo) and antioxidant drug U-74389G exert on serum creatinine levels through kidneys. 2 preliminary studies were used for this purpose including respectively one drug used in a renal ischemia–reperfusion (IR) protocol of an animal model. The preliminary studies are part of the present work. The subjects were pretreated in preliminary studies but the results of the same subjects were simply compared in the current work.

Materials and methods The serum creatinine levels were evaluated at the 60th reperfusion min (for groups A, C and E) and at the 120th reperfusion min (for groups B, D and F) after IR in the 60 rats. Groups A and B received no drugs, rats from groups C and D were administered with Epo, whereas rats from groups E and F were administered with U-74389G.

Results The first preliminary study recommended a non-significant excretory effect of Epo (p-value = 0.4430 > 0.05) than placebo for serum creatinine levels. The second preliminary study proved a very significant excretory effect of U-74389G (p-value = 0.0005 < 0.05) than placebo for serum creatinine levels. These 2 studies were co-evaluated since they came from the same experimental setting. The outcome of the co-evaluation was that U-74389G has at least 5-fold significant excretory action (p-value = 0.0000 < 0.05) than Epo for serum creatinine levels.

Conclusions The U-74389G presents surprising effective excretory potencies for serum creatinine levels maybe of great importance in hemodialysis patients.