Sepsis causes over 200,000 deaths yearly in the US; better treatments are urgently needed. Administering bone marrow stromal cells (BMSCs-also known as mesenchymal stem cells) to mice before or shortly after inducing sepsis by cecal ligation and puncture reduced mortality and improved organ function. The beneficial effect of BMSCs was eliminated by macrophage depletion or pretreatment with antibodies specific for interleukin-10 (IL-10) or IL-10 receptor. Monocytes and/ or macrophages from septic lungs made more IL-10 when prepared from mice treated with BMSCs versus untreated mice. Lipopolysaccharide (LPS)-stimulated macrophages produced more IL-10 when cultured with BMSCs, but this effect was eliminated if the BMSCs lacked the genes encoding Toll-like receptor 4, myeloid differentiation primary response gene-88, tumor necrosis factor (TNF) receptor-1a or cyclooxygenase-2. Our results suggest that BMSCs (activated by LPS or TNF-) reprogram macrophages by releasing prostaglandin E 2 that acts on the macrophages through the prostaglandin EP2 and EP4 receptors. Because BMSCs have been successfully given to humans and can easily be cultured and might be used without human leukocyte antigen matching, we suggest that cultured, banked human BMSCs may be effective in treating sepsis in high-risk patient groups. © 2008 Nature Publishing GroupCorrespondence should be addressed to E.M. (E-mail: mezeye@mail.nih.gov).. 6 These authors contributed equally to this work. AUTHOR CONTRIBUTIONS K.N., A.L., P.S.T.Y., R.A.S. and E.M. formulated the basic hypotheses and experimental design; K.N., A.L., E.M., P.S.T.Y. and R.A.S. collected and evaluated data on survival and organ injury; K.N. and A.L. performed the in vivo experiments; A.L., P.S.T.Y., A.P., K.D., K.L. and X.H. assisted in the in vivo experiments and histology; P.G.R. consulted on BMSC biology; K.N. formulated the molecular mechanism hypothesis and designed and performed in vitro and ex vivo assays; B.H.K. helped to test the involvement of the prostaglandin receptors; J.M.B. and B.M. contributed to testing the involvement of COX2; B.M. performed the measurements for tissue peroxidase; I.J. performed FACS experiments; E.M. wrote the initial manuscript and prepared the figures; all of the authors edited the manuscript.Note: Supplementary information is available on the Nature Medicine website. In the last few years, it has been discovered that BMSCs are potent modulators of immune responses 2-5 . We wondered whether such cells could bring the immune response back into balance, thus attenuating the underlying pathophysiology that eventually leads to severe sepsis, septic shock and death 6,7 . NIH Public AccessAs a model of sepsis, we chose cecal ligation and puncture (CLP), a procedure that has been used for more than two decades 8 . This mouse model closely resembles the human disease: it has a focal origin (cecum), is caused by multiple intestinal organisms, and results in septicemia with release of bacterial toxins into the circulation. With no treatment, the ma...

Sepsis and sepsis-induced acute kidney injury: a life-threatening conditionSepsis is a characteristic set of systemic reactions to overwhelming infection. Sepsis, severe sepsis, and septic shock are defined according to established criteria (Table 1) (1). Discovery of antibiotics has dramatically improved the morbidity and mortality of the infectious diseases for the last decades; indeed, antibiotics and volume resuscitation are the first line of sepsis treatment strategy (2). However, overwhelming inflammatory response accompanied by depression in immunological function causes multiple organ injury and determines clinical outcomes. In addition to inflammation and immunological dysregulation, a number of different mechanisms contribute to sepsis at different phases (Figure 1). For instance, systemic hemodynamics evolves from an early hyperdynamic ("warm shock") state to a late hypodynamic ("cold shock") state.Sepsis is the leading cause of death in critically ill patients, and the incidence of sepsis is increasing (3, 4). The mortality rate of severe sepsis is very high (up to 70%), and the calculated costs exceed $15 billion per year in the United States (3). The rate of severe sepsis during hospitalization almost doubled during the last decade and is considerably greater than previously predicted (5). Sepsis causes multiorgan failure, including acute kidney injury (AKI) (6), and patients with both sepsis and AKI have an especially high mortality rate (7). AKI is diagnosed by a sudden decrease in glomerular filtration rate (GFR), the primary measure of kidney function, which is currently detected clinically as a rise in serum creatinine. A multinational prospective observational study including 29,269 critically ill patients revealed that the occurrence of AKI in the intensive care unit (ICU) was approximately 6%, the most frequent contributing factor to AKI being sepsis (50%) (8). Other reports showed that between 45% and 70% of all AKI is associated with sepsis (9-11). Several different pathophysiological mechanisms have been proposed for sepsis-induced AKI: vasodilation-induced glomerular hypoperfusion, dysregulated circulation within the peritubular capillary network, inflammatory reactions by systemic cytokine storm or local cytokine production (12), and tubular dysfunction induced by oxidative stress (13).Continuing concern over the efficacy and safety of the only FDAapproved therapy for severe sepsis (activated protein C) highlights the critical need to improve our understanding of the pathophysiology of sepsis and sepsis-induced AKI and to develop novel treatment strategies for critically ill patients (14). A multitude of potential drug targets have been identified in animal models of sepsis; however, translation from animals to humans has been exceedingly difficult. Several reviews have pointed out that the failure to translate results from animals to humans has been attributed to disease characteristics of sepsis (complexity and heterogeneity), inappropriate clinical trials (study of ineffective drugs...

Serum creatinine is used clinically to detect and evaluate acute kidney injury (AKI) and chronic kidney disease (CKD), 1,2 although the limitations of serum creatinine for the early detection and accurate estimation of renal injury are widely known. In AKI, serum creatinine does not accurately reflect the GFR because the patient is not in steady state. 3 Furthermore, serum creatinine is also influenced by tubular creatinine secretion and by nonrenal factors such as muscle mass, liver function, and nonrenal (gastrointestinal) elimination.Sepsis remains a serious problem in critically ill patients, and mortality from sepsis is increased dramatically when complicated by AKI; therefore, early detection and accurate evaluation of AKI is important in patients with sepsis. We modified the cecal ligation and puncture (CLP) mouse sepsis model to make it more clinically relevant, and our model developed sepsis-induced AKI. 4 -6 We found that serum creatinine increased to a lesser extent in CLP (approximately 0.5 mg/dl) than ischemia/reperfusion or cisplatin administration (Ͼ1 mg/dl) within 24 h of injury. To explore nonrenal factors that might account for this disparity, we used bilateral nephrectomy (BNx), a technique used recently by others to study the contribution of the kidney to cytokine metabolism and acute lung injury. 7 First, we evaluated sepsis in bilaterally nephrectomized mice. We induced sepsis by CLP surgery with 8-mm cecal ligation, which causes modest sublethal sepsis in normal outbred CD-1 mice. 8 All animals survived until they were killed at 18 h after surgery. CLP surgery in non-nephrectomized mice caused a numerically small, but not significant increase of serum creatinine (sham BNx ϩCLP group). As expected, we found large increases of serum creatinine in the BNxϩsham CLP group; however, induction of sepsis at the time of BNx significantly decreased serum creatinine (BNxϩCLP group) compared with nonseptic BNx alone (BNxϩsham CLP group; Figure 1A), raising doubt about whether serum creatinine accurately reflects impaired kidney function during sepsis. In contrast, nonrenal organ injury markers (aspartate aminotransferase [AST], alanine aminotransferase [ALT], and lactate dehydrogenase [LDH]) and serum TNF-␣ were higher in the BNxϩCLP group than in the BNxϩsham CLP group, confirming the presence of severe sepsis (Figure 1, ABSTRACTAlthough diagnosis and staging of acute kidney injury uses serum creatinine, acute changes in creatinine lag behind both renal injury and recovery. The risk for mortality increases when acute kidney injury accompanies sepsis; therefore, we sought to explore the limitations of serum creatinine in this setting. In mice, induction of sepsis by cecal ligation and puncture in bilaterally nephrectomized mice increased markers of nonrenal organ injury and serum TNF-␣. Serum creatinine, however, was significantly lower in septic animals than in animals subjected to bilateral nephrectomy and sham cecal ligation and puncture. Under these conditions treatment with chloroquine decrease...

Urinary exosomes are excreted from all nephron segments and constitute a rich source of intracellular kidney injury biomarkers. To study whether they contain transcription factors, we collected urine from two acute kidney injury models (cisplatin or ischemia-reperfusion), two podocyte injury models (puromycin-treated rats or podocin-Vpr transgenic mice) and from patients with focal segmental glomerulosclerosis, acute kidney injury and matched controls. Exosomes were isolated by differential centrifugation and found to contain activating transcription factor 3 (ATF3) and Wilms Tumor 1 (WT-1) proteins detected by Western blot. These factors were found in the concentrated exosomal fraction, but not in whole urine. ATF3 was continuously present in urine exosomes of the rat models following acute injury at times earlier than the increase in serum creatinine. ATF3 was found in exosomes isolated from patients with acute kidney injury but not from patients with chronic kidney disease or controls. Urinary WT-1 was present in animal models before significant glomerular sclerosis and in 9/10 patients with focal segmental glomerulosclerosis but not in 8 controls. Our findings suggest that transcription factor ATF3 may provide a novel renal tubular cell biomarker for acute kidney injury while WT-1 may detect early podocyte injury. Measurement of urinary exosomal transcription factors may offer insight into cellular regulatory pathways.

Star RA. Chloroquine and inhibition of Toll-like receptor 9 protect from sepsis-induced acute kidney injury.

The remnant kidney model in C57BL6 mice does not develop progressive chronic kidney disease (CKD). In this study we modified the model to mimic features of human CKD and to define accelerants of disease progression using three strains of mice. Following the procedure there was a progressive increase in albuminuria, progressive loss in renal function, severe glomerulosclerosis and interstitial fibrosis, hypertension, cardiac fibrosis, and anemia by 4 weeks in CD-1 mice and by 12 weeks in 129S3 mice. In contrast, even after 16 weeks, the C57BL/6 mice with a remnant kidney had modestly increased albuminuria without increased blood pressure and without developing CKD or cardiac fibrosis. The baseline blood pressure, determined by radiotelemetry in conscious animals, correlated with CKD progression rates in each strain. Administering angiotensin II overcame the resistance of C57BL/6 mice to CKD following renal mass reduction displaying high blood pressure and albuminuria, severe glomerulosclerosis, and loss of renal function by 4 weeks. Decreasing blood pressure with olmesartan but not hydralazine in CD-1 mice with a remnant kidney reduced CKD progression and cardiac fibrosis. C57BL/6 mice with a remnant kidney and DOCA-salt hypertension developed modest CKD. Each strain had similar degrees of interstitial fibrosis in three different normotensive models of renal fibrosis. Thus reducing renal mass in CD-1 or 129S3 mice mimics many features of human CKD. Angiotensin II can convert the C57BL/6 strain from CKD-resistant to susceptible in this disease model.

This study was performed to quantify the fraction of excreted creatinine not attributable to creatinine filtration for accurately determining the glomerular filtration rate in mice. To measure this we compared creatinine filtration with the simultaneous measurement of inulin clearance using both single-bolus fluorescein isothiocyanate (FITC)-inulin elimination kinetics and standard FITC-inulin infusion. During anesthesia, creatinine filtration was found to be systematically higher than inulin clearance in both male and female C57BL/6J mice. The secretion fraction was significantly less in female mice. Administration of either cimetidine or para-aminohippuric acid, competitors of organic cation and anion transport respectively, significantly reduced the secretion fraction in male and female mice and both significantly increased the plasma creatinine level. Creatinine secretion in both genders was not mediated by the organic cation transporters OCT1 or OCT 2 since secretion fraction levels were identical in FVB wild-type and OCT1/2 knockout mice. Thus, secretion accounts for about 50 and 35% of excreted creatinine in male and female mice, respectively. Increasing plasma creatinine threefold by infusion further increased the secretion fraction. Renal organic anion transporter 1 mRNA expression was higher in male than in female mice, reflecting the gender difference in creatinine secretion. Hence we show that there is a major secretory contribution to creatinine excretion mediated through the organic anion transport system. This feature adds to problems associated with measuring endogenous creatinine filtration in mice.

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