Diagnostic Value of Matrix Metalloproteinase-9 and Tissue Inhibitor of Matrix Metalloproteinase-1 in Sepsis-Associated Acute Kidney Injury

Serum and Urinary Matrix Metalloproteinase-9 Concentrations in Dehydrated Horses

Matrix metalloproteinase-9 is increased in renal tissue in human kidney disease, but its role as a biomarker for kidney disease has not been fully evaluated yet. The aim of this study was to evaluate serum MMP-9 (sMMP-9) and urinary MMP-9 (uMMP-9) concentrations in dehydrated horses. Dehydrated horses were prospectively included. Blood and urinary samples were taken at admission, and after 12, 24, and 48 h (t0, t12, t24, t48), an anti-equine MMP-9 sandwich ELISA was used. Four healthy horses served as the controls. Serum creatinine, urea, symmetric dimethylarginine (SDMA), urine-specific gravity, urinary protein concentration, fractional sodium excretion, and urinary gamma-glutamyl transferase/creatinine ratio (uGGT/Cr) were measured. Statistical analysis included a repeated measures ANOVA and mixed linear regression model. Overall, 40 dehydrated horses were included (mild dehydration 13/40, moderate 16/40, severe 11/40). Acute kidney injury was found in 1/40 horses; 7/40 horses showed elevated serum creatinine, 11/40 horses elevated serum SDMA, and 5/28 elevated uGGT/Cr at presentation. In dehydrated horses, sMMP-9 concentrations were significantly higher on t0 (median: 589 ng/mL, range: 172-3597 ng/mL) compared to t12 (340 ng/mL, 132-1213 ng/mL), t24 (308 ng/mL, 162-1048 ng/mL), and t48 (258 ng/mL, 130-744 ng/mL). In healthy horses, sMMP-9 (239 ng/mL, 142-508 ng/mL) showed no differences over time or compared to patients. uMMP-9 and uMMP-9/creatinine did not differ over time or to the controls. No differences were found between dehydration groups. Urinary casts (p = 0.001; estimate = 135) and uGGT/Cr (p = 0.03; estimate = 6.5) correlated with sMMP-9. Serum urea was associated with uMMP-9/Cr (p = 0.01, estimate 0.9). In conclusion, sMMP-9 was elevated at arrival in dehydrated patients compared to later measurements. Correlations to uGGT/Cr and urinary casts need further evaluation.

Low nephron endowment increases susceptibility to renal stress and chronic kidney disease

Preterm birth results in low nephron endowment and increased risk of acute kidney injury (AKI) and chronic kidney disease (CKD). To understand the pathogenesis of AKI and CKD in preterm humans, we generated potentially novel mouse models with a 30%-70% reduction in nephron number by inhibiting or deleting Ret tyrosine kinase in the developing ureteric bud. These mice developed glomerular and tubular hypertrophy, followed by the transition to CKD, recapitulating the renal pathological changes seen in humans born preterm. We injected neonatal mice with gentamicin, a ubiquitous nephrotoxic exposure in preterm infants, and detected more severe proximal tubular injury in mice with low nephron number compared with controls with normal nephron number. Mice with low nephron number had reduced proliferative repair with more rapid development of CKD. Furthermore, mice had more profound inflammation with highly elevated levels of MCP-1 and CXCL10, produced in part by damaged proximal tubules. Our study directly links low nephron endowment with postnatal renal hypertrophy, which in this model is maladaptive and results in CKD. Underdeveloped kidneys are more susceptible to gentamicin-induced AKI, suggesting that AKI in the setting of low nephron number is more severe and further increases the risk of CKD in this vulnerable population.

Potential Biomarkers for Early Diagnosis, Evaluation, and Prognosis of Sepsis-Induced Coagulopathy

Sepsis-induced coagulopathy (SIC) is a life-threatening complication characterized by the systemic activation of coagulation in sepsis. The diagnostic criteria of SIC consist of three items, including Sequential Organ Failure Assessment (SOFA) score, platelet count, and prothrombin time (PT)-international normalized ratio (INR). SIC has a high prevalence and it can lead to a higher mortality rate and longer length of hospital and ICU stay. Thus, the early detection of SIC is extremely important. It is unfortunate that there is still no precise biomarker for early diagnosis and assessment of the prognosis of SIC. We reviewed the current literature and discovered that some potential biomarkers, such as soluble thrombomodulin (sTM), thrombin-antithrombin complex (TAT), tissue plasminogen activator-inhibitor complex (t-PAIC), α2-plasmin inhibitor-plasmin complex (PIC), C-type lectin-like receptor 2 (CLEC-2), neutrophil extracellular traps (NETs), prothrombin fragment 1.2 (F1.2), Angiopoietin-2 (Ang-2), plasminogen activator inhibitor-1 (PAI-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) may be useful for early diagnosis, evaluation, and prognosis of SIC. Early initiation of treatment without missing any therapeutic opportunities may improve SIC patients' prognosis. Further large-scale clinical studies are still needed to confirm the role of these biomarkers in the diagnosis and prognosis assessment of SIC.

Urinary proteome analysis of acute kidney injury in post-cardiac surgery patients using enrichment materials with high-resolution mass spectrometry

Background: Cardiac surgery-associated acute kidney injury (CSA-AKI) may increase the mortality and incidence rates of chronic kidney disease in critically ill patients. This study aimed to investigate the underlying correlations between urinary proteomic changes and CSA-AKI.

Methods: Nontargeted proteomics was performed using nano liquid chromatography coupled with Orbitrap Exploris mass spectrometry (MS) on urinary samples preoperatively and postoperatively collected from patients with CSA-AKI. Gemini C18 silica microspheres were used to separate and enrich trypsin-hydrolysed peptides under basic mobile phase conditions. Differential analysis was conducted to screen out urinary differential expressed proteins (DEPs) among patients with CSA-AKI for bioinformatics. Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis was adopted to identify the altered signal pathways associated with CSA-AKI.

Results: Approximately 2000 urinary proteins were identified and quantified through data-independent acquisition MS, and 324 DEPs associated with AKI were screened by univariate statistics. According to KEGG enrichment analysis, the signal pathway of protein processing in the endoplasmic reticulum was enriched as the most up-regulated DEPs, and cell adhesion molecules were enriched as the most down-regulated DEPs. In protein–protein interaction analysis, the three hub targets in the up-regulated DEPs were α-1-antitrypsin, β-2-microglobulin and angiotensinogen, and the three key down-regulated DEPs were growth arrest-specific protein 6, matrix metalloproteinase-9 and urokinase-type plasminogen activator.

Conclusion: Urinary protein disorder was observed in CSA-AKI due to ischaemia and reperfusion. The application of Gemini C18 silica microspheres can improve the protein identification rate to obtain highly valuable resources for the urinary DEPs of AKI. This work provides valuable knowledge about urinary proteome biomarkers and essential resources for further research on AKI.

The Effect of Thiamine, Ascorbic Acid, and the Combination of Them on the Levels of Matrix Metalloproteinase-9 (MMP-9) and Tissue Inhibitor of Matrix Metalloproteinase-1 (TIMP-1) in Sepsis Patients

Background

Methods

Results

Conclusion

Tubular and glomerular biomarkers of renal tissue function in the urine of fetuses with posterior urethral valves

INTRODUCTION

Posterior urethral valve (PUV) is a congenital malformation characterized by a membranous structure located in the prostatic portion of the male posterior urethra that obstructs the urinary flow. Efforts have been made to determine the degree of impairment of fetal kidney function in this condition.

OBJECTIVE

This study aimed to measure the levels of urinary biomarkers of glomerular and tubular functions in fetuses with PUV and to compare with the levels of the same molecules in healthy male premature newborns.

STUDY DESIGN

Urine samples from 43 fetuses with PUVs were collected and compared with urine samples from 40 healthy male newborns of the same gestational age (controls). Tubular and glomerular biomarkers levels were measured in urine samples by MILLIPLEX® assay kits. Levels of the molecules were related to creatinine (Cr) measurements at same urine samples and expressed as pg/mg Cr. Results were analysed with Graphpad Prism version 7.0 and SPSS version 20.0.

RESULTS

Fetuses with PUV showed a significant reduction in urine levels of Epidermal Growth Factor (EGF), Calbindin, Osteoactivin, Molecule Renal Injury 1 (KIM-1 and Factor of trefoil 3 (TFF-3) when compared to controls. On the other hand, urine levels of cystatin C and renin were higher in PUV fetuses. The levels of molecules also differed according to urine osmolality and grade of hydronephrosis.

DISCUSSION

Some urinary excreted molecules may indicate kidney damage in several segments along the nephron, while others may exert important functions. Mechanical and immunological mechanisms related to PUV might significantly modulate the synthesis of cytokines related to glomerular and tubular physiology, leading to alterations in urinary concentrations of those molecules. These biomarkers can be used as future diagnostic and prognostic markers in clinical practice.

CONCLUSION

Early kidney structural and functional impairment influenced the synthesis of glomerular and tubular molecules related to kidney physiological processes in fetuses with PUV.

Derivation and validation of urinary TIMP-1 for the prediction of acute kidney injury and mortality in critically ill children

Background

Acute kidney injury (AKI) is associated with high morbidity and mortality. Multiple urinary biomarkers have been identified to be associated with the prediction of AKI and outcomes. However, the accuracy of these urinary biomarkers for AKI and associated outcomes has not been clearly defined, especially in heterogeneous populations. The aims of the study were to compare the ability of 10 existing or potential urinary biomarkers to predict AKI and pediatric intensive care unit (PICU) mortality and validate urinary tissue inhibitor of metalloproteinases-1 (uTIMP-1) as a better biomarker for early prediction in heterogeneous critically ill children.

Methods

A derivation-validation approach with separate critically ill cohorts was designed. We first conducted a prospective cohort study to determine the ability of 10 urinary biomarkers serially measured in 123 children during the first 7 days of PICU stay to predict AKI and PICU mortality (derivation study) and further validated the better biomarker of uTIMP-1 in a separate cohort of 357 critically ill children (validation study). AKI diagnosis was based on KDIGO classification with serum creatinine and urine output. PICU mortality was defined as all-cause mortality.

Results

In the derivation cohort, 17 of 123 (13.8%) children developed AKI stage 3 or died during the PICU stay, and both the initial and peak uTIMP-1 displayed the highest AUCs of 0.87 (0.79–0.94) and 0.90 (0.84–0.96), respectively, for predicting AKI stage 3 or death. In the validation cohort, 78 of 357 (21.8%) developed AKI during the first week after admission, and 38 (10.6%) died during the PICU stay. The initial uTIMP-1 level was validated to be independently associated with AKI (AOR = 2.88, 95% CI 1.97–4.21), severe AKI (AOR = 2.62, 95% CI 1.78–3.88), AKI stage 3 (AOR = 2.94, 95% CI 1.84–4.68) and PICU mortality (AOR = 1.92, 95% CI 1.11–3.30) after adjustment for potential confounders. The predictive values of uTIMP-1 for AKI, severe AKI, AKI stage 3 and PICU mortality were 0.80 (0.74–0.86), 0.83 (0.77–0.89), 0.84 (0.77–0.92) and 0.83 (0.76–0.89), respectively.

Conclusions

Urinary TIMP-1 levels have been identified and validated to be independently associated with AKI and PICU mortality in independent prospective cohorts and may be an early potential indicator of AKI and PICU mortality in critically ill children.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03302-0.

Elevated Plasma Levels of Matrix Metalloproteinase-3 and Tissue-Inhibitor of Matrix Metalloproteinases-1 Associate With Organ Dysfunction and Mortality in Sepsis

BACKGROUND

Matrix Metalloproteinases (MMP) respond to tissue damage during sepsis. Higher plasma concentrations of MMPs and the tissue-inhibitor of matrix metalloproteinases (TIMP) have been reported in sepsis compared with healthy controls. The objective of this study was to examine if plasma levels of MMP-3, MMP-9, and TIMP-1 associate with mortality and organ dysfunction during sepsis.

METHODS

We conducted a prospective cohort study of critically ill patients with sepsis adjudicated per Sepsis-3 criteria at a tertiary academic medical center. We measured plasma concentrations of MMP-3, MMP-9, and TIMP-1 on intensive care unit admission. We phenotyped the subjects for shock, acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and mortality at 30 days. We used logistic regression to test the associations between the MMPs and TIMP-1 with shock, ARDS, AKI, and mortality.

RESULTS

Higher plasma TIMP-1 levels were associated with shock (odds ratio [OR] 1.51 per log increase [95% CI 1.25, 1.83]), ARDS (OR 1.24 [95% CI 1.05, 1.46]), AKI (OR 1.18 [95% CI 1.01, 1.38]), and mortality (OR 1.20 [95% CI 1.05, 1.46]. Higher plasma MMP-3 concentrations were associated with shock (OR 1.40 [95% CI 1.12, 1.75]) and mortality (OR 1.24 [95% CI 1.03, 1.48]) whereas MMP-9 levels were not associated with outcomes. Higher plasma TIMP-1 to MMP-3 ratios were associated with shock (OR 1.41 [95% CI 1.15, 1.72], P = 0.02).

CONCLUSION

Elevated plasma concentrations of TIMP-1 associate with organ dysfunction and mortality in sepsis. Higher plasma levels of MMP-3 associate with shock and mortality. Plasma MMP and TIMP-1 may warrant further investigation as emerging sepsis theragnostic biomarkers.

Aristolochic Acid Induces Chronic Kidney Disease in ACE Knockout Mice

Background:

Aristolochic acid I (AAI) is an extract from Chinese herbs that causes progressive interstitial nephritis. The aim of this research is to know whether chymases play the crucial role in AAI-induced nephropathy.

Methods:

The mice were treated with AAI via intraperitoneal injection and the accumulated AAI dosages are 30 mg/kg of body weight for two, four, six, and eight weeks. The animals were sacrificed after another two or four weeks for nephropathy development. Collection of blood, urine, and kidney samples for the further biochemical analysis, hematoxylin–eosin (H and E) and Masson's trichrome stained to detected pathologic, and MMP2 and MMP9 activity assays.

Results:

After the treatment of AAI, of the mice, their body weights were decreased (P < 0.01), and concentration of creatinine and blood urea nitrogen (BUN) in serum (P < 0.01) and urine collection were increased (P < 0.01). In the renal tissue sections, high amount of inflammatory cells were found by H and E stain, and increased fibrosis in renal interstitial tissue were observed by Masson's trichrome stain. In mice kidney tissue, significantly increased chymase activity after treatment of AAI was found (P < 0.01), but ACE activity did not show significant changes. In ACE KO mice, increased MMP2 and decreased MMP9 activity were found in the AAI-treated mice compared with AAI-untreated control (P < 0.01).

Conclusions:

Moreover, it was also observed that the deficiency of ACE would accelerate the disease development of AAI-induced nephropathy. These results may help to know more information about the role of AAI-induced chronic kidney disease and can be applied in developing new drug targets for nephropathy.

Current and Evolving Indications for Simultaneous Liver Kidney Transplantation

This review will discuss the etiologies of kidney disease in liver transplant candidates, provide a historical background of the prior evolution of simultaneous liver-kidney (SLK) transplant indications, discuss the current indications for SLK including Organ Procurement and Transplantation Network policies and Model for End Stage Liver Disease exception points, as well as provide an overview of the safety net kidney transplant policy. Finally, the authors explore unanswered questions and future research needed in SLK transplantation.

Position paper on liver and kidney diseases from the Italian Association for the Study of Liver (AISF), in collaboration with the Italian Society of Nephrology (SIN)

Liver and kidney are strictly connected in a reciprocal manner, in both the physiological and pathological condition. The Italian Association for the Study of Liver, in collaboration with the Italian Society of Nephrology, with this position paper aims to provide an up-to-date overview on the principal relationships between these two important organs. A panel of well-recognized international expert hepatologists and nephrologists identified five relevant topics: 1) The diagnosis of kidney damage in patients with chronic liver disease; 2) Acute kidney injury in liver cirrhosis; 3) Association between chronic liver disease and chronic kidney disease; 4) Kidney damage according to different etiology of liver disease; 5) Polycystic kidney and liver disease. The discussion process started with a review of the literature relating to each of the five major topics and clinical questions and related statements were subsequently formulated. The quality of evidence and strength of recommendations were graded according to the GRADE system. The statements presented here highlight the importance of strong collaboration between hepatologists and nephrologists for the management of critically ill patients, such as those with combined liver and kidney impairment.

Bioinformatic analysis identifies potential biomarkers and therapeutic targets of septic-shock-associated acute kidney injury

Background

Sepsis and septic shock are life-threatening diseases with high mortality rate in intensive care unit (ICU). Acute kidney injury (AKI) is a common complication of sepsis, and its occurrence is a poor prognostic sign to septic patients. We analyzed co-differentially expressed genes (co-DEGs) to explore relationships between septic shock and AKI and reveal potential biomarkers and therapeutic targets of septic-shock-associated AKI (SSAKI).

Methods

Two gene expression datasets (GSE30718 and GSE57065) were downloaded from the Gene Expression Omnibus (GEO). The GSE57065 dataset included 28 septic shock patients and 25 healthy volunteers and blood samples were collected within 0.5, 24 and 48 h after shock. Specimens of GSE30718 were collected from 26 patients with AKI and 11 control patents. AKI-DEGs and septic-shock-DEGs were identified using the two datasets. Subsequently, Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed to elucidate molecular mechanisms of DEGs. We also evaluated co-DEGs and corresponding predicted miRNAs involved in septic shock and AKI.

Results

We identified 62 DEGs in AKI specimens and 888, 870, and 717 DEGs in septic shock blood samples within 0.5, 24 and 48 h, respectively. The hub genes of EGF and OLFM4 may be involved in AKI and QPCT, CKAP4, PRKCQ, PLAC8, PRC1, BCL9L, ATP11B, KLHL2, LDLRAP1, NDUFAF1, IFIT2, CSF1R, HGF, NRN1, GZMB, and STAT4 may be associated with septic shock. Besides, co-DEGs of VMP1, SLPI, PTX3, TIMP1, OLFM4, LCN2, and S100A9 coupled with corresponding predicted miRNAs, especially miR-29b-3p, miR-152-3p, and miR-223-3p may be regarded as promising targets for the diagnosis and treatment of SSAKI in the future.

Conclusions

Septic shock and AKI are related and VMP1, SLPI, PTX3, TIMP1, OLFM4, LCN2, and S100A9 genes are significantly associated with novel biomarkers involved in the occurrence and development of SSAKI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00176-y.

Identification of fibroblast activation-related genes in two acute kidney injury models

Background

Ischemia-reperfusion injury and drug-induced nephrotoxicity are the two most common reasons for acute kidney injury (AKI). However, little attention has been paid to early activation of fibroblasts in the progression of AKI to chronic kidney disease (CKD). The present study aimed to identify related genes and pathways on fibroblast activation in two mouse models of AKI: ischemia-reperfusion injury (IRI) model and folic acid (FA)-induced injury model.

Methods

The microarray expression profiles of GSE62732 and GSE121190 were downloaded from the GEO database, and the differentially expressed genes (DEGs) was analyzed using the Limma package of R software. Principal component analysis (PCA) was also performed using R. The functional information of gene products was annotated by Gene Ontology (GO) and DAVID online database, and the pathway analysis was carried out by using the Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) database. Protein-protein interactions (PPI) network was constructed by STRING and Cytoscape. Furthermore, in the Hypoxia/Reoxygenation (H/R) model, the morphological changes of cells were observed under microscope and the expression of the hub genes in NRK-49F cells were validated by qRT-PCR assays.

Results

A total of 457 DEGs were identified. Among these, 215 DEGs were upregulated and 242 DEGs were downregulated in the acute injured samples compared with uninjured samples. The GO enrichment analysis indicated that these DEGs were mainly involved in transport, the oxidation-reduction process, the metabolic process, metal ion binding, hydrolase activity, and oxidoreductase activity. The KEGG analysis revealed that these DEGs were significantly enriched in the PI3K-Akt signaling pathway, protein digestion and absorption pathway, and focal adhesion pathway. The hub genes including Hnf4α, Pck1 and Timp1 were validated by the qRT-PCR assay in NRK-49F cells in the H/R model.

Conclusions

Hnf4α, Pck1 and Timp-1 may play a pivotal role in the early activation of fibroblasts, providing novel therapeutic strategies for early prediction and treatment of renal fibrosis.

MMP-9 Concentration in Peritoneal Fluid Is a Valuable Biomarker Associated with Endotoxemia in Equine Colic

The purpose of the study was to compare the results of sepsis scoring (clinical examination and clinical pathology) to the concentrations of matrix-metalloproteinases (MMPs) -2, -8, and -9; tissue-inhibitor of metalloproteinases (TIMPs) -1 and -2; and inflammatory chemokines interleukin (IL) 1β and tumor-necrosis-factor-alpha (TNF-α) in plasma and peritoneal fluid of equine colic patients. A modified sepsis scoring including general condition, heart and respiratory rate, rectal temperature, mucous membranes, white blood cell count (WBC), and ionized calcium was applied in 47 horses presented with clinical signs of colic. Using this scoring system, horses were classified as negative (n = 32, ≤6/19 points), questionable (n = 9, 7-9/19 points), or positive (n = 6, ≥10/19 points) for sepsis. MMPs, TIMPs, IL-1β, and TNF-α concentrations were evaluated in plasma and peritoneal fluid using species-specific sandwich ELISA kits. In a linear discriminant analysis, all parameters of sepsis scoring apart from calcium separated well between sepsis severity groups (P < 0.05). MMP-9 was the only biomarker of high diagnostic value, while all others remained insignificant. A significant influence of overall sepsis scoring on MMP-9 was found for peritoneal fluid (P = 0.005) with a regression coefficient of 0.092, while no association was found for plasma (P = 0.085). Using a MMP-9 concentration of >113 ng/ml in the peritoneal fluid was found to be the ideal cutoff to identify positive sepsis scoring (≥10/19 points; sensitivity of 83.3% and specificity of 82.9%). In conclusion, MMP-9 was found to be a biomarker of high diagnostic value for sepsis and endotoxemia in equine colic. The evaluation of peritoneal fluid seems preferable in comparison to plasma. As abdominocentesis is commonly performed in the diagnostic work-up of equine colic, a pen-side assay would be useful and easy-to-perform diagnostic support in the decision for therapeutic intervention.

Urinary MMP-9/UCr association with albumin concentration and albumin-creatinine-ratio in Mexican patients with type 2 diabetes mellitus

BACKGROUND

Chronic kidney disease is one of the most common complications of type 2 diabetes mellitus (T2DM), causing an increased risk of cardiovascular morbidity and mortality. Matrix metalloproteinase (MMP) activity has been proposed as useful biomarker for diabetic renal and vascular complications.

METHODS

A cross-sectional study was conducted among T2DM patients who attended a public secondary hospital in Mexico. We performed clinical, biochemical, and microbiological assessments, as well chronic kidney disease diagnosis according to the KDIGO guideline. Urinary MMP-9 was quantified by ELISA and adjusted using urinary creatinine (UCr).

RESULTS

A total of 111 patients were included. Most participants were women (66%). Mean age was 61 ± 10 years and median T2DM duration was estimated at 11 years. Through multivariate analysis, MMP-9/UCr was found to be associated with albumin concentration and albumin to creatinine ratio.

DISCUSSION

Validation of non-invasive biomarkers of chronic kidney disease among T2DM patients is necessary. Here, we demonstrate MMP-9/UCr as a potential biomarker of albumin concentration and albumin to creatinine ratio in Mexican patients with T2DM.

Using best subset regression to identify clinical characteristics and biomarkers associated with sepsis-associated acute kidney injury

Sepsis-associated acute kidney injury (AKI) is a complex clinical disorder associated with inflammation, endothelial dysfunction, and dysregulated coagulation. With standard regression methods, collinearity among biomarkers may lead to the exclusion of important biological pathways in a single final model. Best subset regression is an analytic technique that identifies statistically equivalent models, allowing for more robust evaluation of correlated variables. Our objective was to identify common clinical characteristics and biomarkers associated with sepsis-associated AKI. We enrolled 453 septic adults within 24 h of intensive care unit admission. Using best subset regression, we evaluated for associations using a range of models consisting of 1-38 predictors (composed of clinical risk factors and plasma and urine biomarkers) with AKI as the outcome [defined as a serum creatinine (SCr) increase of ≥0.3 mg/dL within 48 h or ≥1.5× baseline SCr within 7 days]. Two hundred ninety-seven patients had AKI. Five-variable models were found to be of optimal complexity, as the best subset of five- and six-variable models were statistically equivalent. Within the subset of five-variable models, 46 permutations of predictors were noted to be statistically equivalent. The most common predictors in this subset included diabetes, baseline SCr, angiopoetin-2, IL-8, soluble tumor necrosis factor receptor-1, and urine neutrophil gelatinase-associated lipocalin. The models had a c-statistic of ∼0.70 (95% confidence interval: 0.65-0.75). In conclusion, using best subset regression, we identified common clinical characteristics and biomarkers associated with sepsis-associated AKI. These variables may be especially relevant in the pathogenesis of sepsis-associated AKI.

Identification and Validation of Potential Biomarkers and Their Functions in Acute Kidney Injury

Acute kidney injury (AKI) is a global public health concern associated with high morbidity, mortality, and health-care costs, and the therapeutic measures are still limited. This study aims to investigate crucial genes correlated with AKI, and their potential functions, which might contribute to a better understanding of AKI pathogenesis. The high-throughput data GSE52004 and GSE98622 were downloaded from Gene Expression Omnibus; four group sets were extracted and integrated. Differentially expressed genes (DEGs) in the four group sets were identified by limma package in R software. The overlapping DEGs among four group sets were further analyzed by the VennDiagram package, and their potential functions were analyzed by the GO and KEGG pathway enrichment analyses using the DAVID database. Furthermore, the protein-protein interaction (PPI) network was constructed by STRING, and the functional modules of the PPI network were filtered by MCODE and ClusterOne in Cytoscape. Hub genes of overlapping DEGs were identified by Cyto-Hubba and cytoNCA. The expression of 35 key genes was validated by quantitative real-time PCR (qRT-PCR). Western blot and immunofluorescence were performed to validate an important gene Egr1. A total of 722 overlapping DEGs were differentially expressed in at least three group sets. These genes mainly enriched in cell proliferation and fibroblast proliferation. Additionally, 5 significant modules and 21 hub genes, such as Havcr1, Krt20, Sox9, Egr1, Timp1, Serpine1, Edn1, and Apln were screened by analyzing the PPI networks. The 5 significant modules were mainly enriched in complement and coagulation cascades and Metabolic pathways, and the top 21 hub genes were mainly enriched in positive regulation of cell proliferation. Through validation, Krt20 were identified as the top 1 upregulated genes with a log2 (fold change) larger than 10 in all these 35 genes, and 21 genes were validated as significantly upregulated; Egr1 was validated as an upregulated gene in AKI in both RNA and protein level. In conclusion, by integrated analysis of different high-throughput data and validation by experiment, several crucial genes were identified in AKI, such as Havcr1, Krt20, Sox9, Egr1, Timp1, Serpine1, Edn1, and Apln. These genes were very important in the process of AKI, which could be further utilized to explore novel diagnostic and therapeutic strategies.

Plasma MMP-9 and TIMP-1 levels on ICU admission are associated with 30-day survival

Background

Matrix metalloproteinases (MMPs) are involved in systemic inflammatory responses and organ failure. The aim of this study was to evaluate early circulating plasma levels of MMP‑2, MMP‑9 and their inhibitors TIMP‑1 and TIMP‑2 and their prognostic significance in critically ill patients on admission to the intensive care unit (ICU).

Methods

In a single center prospective study 120 consecutive patients (72.5% male, mean age 66.8 ± 13.3 years, mean simplified acute physiology score [SAPS II] score 52.9 ± 21.9) were enrolled on transfer to the ICU of a cardiology department. The most common underlying conditions were cardiac diseases (n = 42.5%), respiratory failure (n = 10.8%) and sepsis (n = 6.7%). Blood samples were taken within 12 h of ICU admission. The MMP‑2, MMP‑9, TIMP‑1 and TIMP‑2 levels in plasma were evaluated in terms of 30-day survival, underlying condition and clinical score.

Results

On ICU admission 30-day survivors had significantly lower plasma MMP‑9 (odds ratio, OR 1.67 per 1 SD; 95% confidence interval, CI 1.10−2.53; p = 0.016) and TIMP‑1 (OR 2.15 per 1 SD; 95% CI 1.27−3.64; p = 0.004) levels than non-survivors; furthermore, MMP‑9 and TIMP‑1 correlated well with SAPS II (both p < 0.01). In patients with underlying cardiac diseases, MMP‑9 (p = 0.002) and TIMP‑1 (p = 0.01) were independent predictors of survival (Cox regression). No significant correlation was found between MMP‑2 and TIMP‑2 levels, MMP/TIMP ratios and 30-day mortality.

Conclusion

The MMP‑9 and TIMP‑1 levels are significantly elevated in acute critical care settings with increased short-term mortality risk, especially in patients with underlying heart disease. These findings support the value of MMPs and TIMPs as prognostic markers and potential therapeutic targets in conditions leading to systemic inflammation and acute organ failure.

External Validation of a Pretransplant Biomarker Model (REVERSE) Predictive of Renal Recovery After Liver Transplantation

In patients with end-stage liver disease, the ability to predict recovery of renal function following liver transplantation (LT) remains elusive. However, several important clinical decisions depend on whether renal dysfunction is recoverable after LT. We used a cohort of patients undergoing LT to independently validate a published pre-LT model predictive of post-transplant renal recovery (Renal Recovery Assessment at Liver Transplant [REVERSE]: high osteopontin [OPN] and tissue inhibitor of metalloproteinases-1 [TIMP-1] levels, age < 57, no diabetes). Serum samples pre-LT and 4-12 weeks post-LT (n = 117) were analyzed for kidney injury proteins from three groups of recipients: (1) estimated glomerular filtration rate (eGFR) < 30 mL/minute/1.73 m² prior to and after LT (irreversible acute kidney injury [AKI]), (2) eGFR < 30 mL/minute/1.73 m² prior to LT and >50 mL/minute/1.73 m² after LT (reversible AKI [rAKI]) (3) eGFR > 50 mL/minute/1.73 m² prior to and after LT (no AKI). In patients with elevated pre-LT serum levels of OPN and TIMP-1, recovery of renal function correlated with decreases in the level of both proteins. At 4 weeks post-LT (n = 77 subset), the largest decline in OPN and TIMP-1 was seen in the rAKI group. Validation of the REVERSE model in this independent data set had high area under the curve (0.78) in predicting full post-LT renal recovery (sensitivity 0.86, specificity 0.6, positive predictive value 0.81, negative predictive value 0.69). Our eGFR findings were confirmed using measured GFR. Conclusion: The REVERSE model, derived from an initial training set combining plasma biomarkers and clinical characteristics, demonstrated excellent external validation performance characteristics in an independent patient cohort using serum samples. Among patients with kidney injury pre-LT, the predictive ability of this model may prove beneficial in clinical decision-making both prior to and following transplantation.

The future for diagnostic tests of acute kidney injury in critical care: evidence synthesis, care pathway analysis and research prioritisation

BACKGROUND

Acute kidney injury (AKI) is highly prevalent in hospital inpatient populations, leading to significant mortality and morbidity, reduced quality of life and high short- and long-term health-care costs for the NHS. New diagnostic tests may offer an earlier diagnosis or improved care, but evidence of benefit to patients and of value to the NHS is required before national adoption.

OBJECTIVES

To evaluate the potential for AKI in vitro diagnostic tests to enhance the NHS care of patients admitted to the intensive care unit (ICU) and identify an efficient supporting research strategy.

DATA SOURCES

We searched ClinicalTrials.gov, The Cochrane Library databases, Embase, Health Management Information Consortium, International Clinical Trials Registry Platform, MEDLINE, metaRegister of Current Controlled Trials, PubMed and Web of Science databases from their inception dates until September 2014 (review 1), November 2015 (review 2) and July 2015 (economic model). Details of databases used for each review and coverage dates are listed in the main report.

REVIEW METHODS

The AKI-Diagnostics project included horizon scanning, systematic reviewing, meta-analysis of sensitivity and specificity, appraisal of analytical validity, care pathway analysis, model-based lifetime economic evaluation from a UK NHS perspective and value of information (VOI) analysis.

RESULTS

The horizon-scanning search identified 152 potential tests and biomarkers. Three tests, Nephrocheck^® (Astute Medical, Inc., San Diego, CA, USA), NGAL and cystatin C, were subjected to detailed review. The meta-analysis was limited by variable reporting standards, study quality and heterogeneity, but sensitivity was between 0.54 and 0.92 and specificity was between 0.49 and 0.95 depending on the test. A bespoke critical appraisal framework demonstrated that analytical validity was also poorly reported in many instances. In the economic model the incremental cost-effectiveness ratios ranged from £11,476 to £19,324 per quality-adjusted life-year (QALY), with a probability of cost-effectiveness between 48% and 54% when tests were compared with current standard care.

LIMITATIONS

The major limitation in the evidence on tests was the heterogeneity between studies in the definitions of AKI and the timing of testing.

CONCLUSIONS

Diagnostic tests for AKI in the ICU offer the potential to improve patient care and add value to the NHS, but cost-effectiveness remains highly uncertain. Further research should focus on the mechanisms by which a new test might change current care processes in the ICU and the subsequent cost and QALY implications. The VOI analysis suggested that further observational research to better define the prevalence of AKI developing in the ICU would be worthwhile. A formal randomised controlled trial of biomarker use linked to a standardised AKI care pathway is necessary to provide definitive evidence on whether or not adoption of tests by the NHS would be of value.

STUDY REGISTRATION

The systematic review within this study is registered as PROSPERO CRD42014013919.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Association of urinary activity of MMP-9 with renal impairment in Mexican patients with type 2 diabetes mellitus

BACKGROUND

Diabetic kidney disease is the most common cause of chronic kidney disease (CKD). An early event in diabetic kidney disease is alteration of the glomerular basement membrane and the mesangial expansion. Matrix metalloproteinases (MMP) are a family of endopeptidases responsible for controlling the pathophysiological remodeling of tissues, including renal tissues. MMP-9 in human urine has been proposed as a marker of diabetic nephropathy and urinary tract infections (UTI).

METHODS

A cross-sectional study was conducted in type 2 diabetes mellitus (T2DM) patients who receive first level medical attention in Mexico. We used ELISA to measure MMP-9 levels in the urine of subjects with T2DM ≥ 18 years of age, who fulfilled the clinical requirements for calculation of glomerular filtration rate (GFR), according to the K/DOQI guide, in an attempt to identify whether MMP-9 levels in T2DM differ in patients with and without renal impairment. Univariate and multivariable analyses were performed in order to identify the association between MMP-9 and renal impairment.

RESULTS

Included in the study were 34 (45%) subjects with renal impairment and 42 (55%) without. In the group with renal impairment, 10 subjects corresponded to stages 1-2 and 24 subjects corresponded to stage 3, according to their values of GFR and urinary albumin, following that proposed by the K/DOQI. No differences were found relating to sex, age, having or not having a partner, education, being able to read and write a message and duration of T2DM. Moreover, no differences were found between the groups in terms of weight, height, body mass index, waist size in general and frequency of UTI. In contrast, serum creatinine and urinary albumin were higher in the group with renal impairment, while GFR was greater in the group without renal impairment. Levels of MMP-9 were greater in women compared to men. Through univariate analysis in the general population, the presence of MMP-9 and that of its percentile 90 (P90) P90 were associated with the renal impairment group; however, in patients without UTI, only the presence of MMP-9 was associated with the renal impairment group, and no association was found with its P90. Multivariate analysis revealed an association between MMP-9 and its P90 with renal impairment.

DISCUSSION

It is necessary to validate sensitive and non-invasive biological markers of CKD. We demonstrate that the presence and P90 of urinary MMP-9 are associated with renal impairment in Mexican patients with T2DM. While high levels of MMP-9 were associated to females and UTI, the presence of UTI was not associated with the incidence of renal impairment.

Matrix Metalloproteinase-9 and Tissue Inhibitor of Matrix Metalloproteinase-1 in Sepsis after Major Abdominal Surgery

Background

The role of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in sepsis after major abdominal surgery and sepsis-associated organ dysfunction is unexplored.

Materials and Methods

Fifty-three patients with sepsis after major abdominal surgery were compared to 50 operated and 50 nonoperated controls. MMP-9, TIMP-1, biomarkers of inflammation, kidney and liver injury, coagulation, and metabolic disorders were measured daily during 96 h following diagnosis of sepsis and once in controls. MMP-9/TIMP-1 ratios and disease severity scores were calculated. Use of vasopressors/inotropes, mechanical ventilation, and survival were recorded.

Results

Septic patients had lower MMP-9 and MMP-9/TIMP-1 ratios but higher TIMP-1 levels compared to controls. AUC-ROC for diagnosis of sepsis was 0.940 and 0.854 for TIMP-1 and 0.924 and 0.788 for MMP-9/TIMP-1 ratio (sepsis versus nonoperated and sepsis versus operated controls, resp.). Lower MMP-9 and MMP-9/TIMP-1 ratio and higher TIMP-1 levels were associated with shorter survival. MMP-9, TIMP-1, and MMP-9/TIMP-1 ratio correlated with biomarkers of inflammation, kidney and liver injury, coagulation, metabolic disorders, and disease severity scores. Use of vasopressors/inotropes was associated with higher TIMP-1 levels.

Conclusions

MMP-9, TIMP-1, and MMP-9/TIMP ratio were good diagnostic or prognostic biomarkers of sepsis after major abdominal surgery and were linked to sepsis-associated organ dysfunction.

Just Look! Intravital Microscopy as the Best Means to Study Kidney Cell Death Dynamics

Kidney cell death plays a key role in the progression of life-threatening renal diseases, such as acute kidney injury and chronic kidney disease. Injured and dying epithelial and endothelial cells take part in complex communication with the innate immune system, which drives the progression of cell death and the decrease in renal function. To improve our understanding of kidney cell death dynamics and its impact on renal disease, a study approach is needed that facilitates the visualization of renal function and morphology in real time. Intravital multiphoton microscopy of the kidney has been used for more than a decade and made substantial contributions to our understanding of kidney physiology and pathophysiology. It is a unique tool that relates renal structure and function in a time- and spatial-dependent manner. Basic renal function, such as microvascular blood flow regulation and glomerular filtration, can be determined in real time and homeostatic alterations, which are linked inevitably to cell death and can be depicted down to the subcellular level. This review provides an overview of the available techniques to study kidney dysfunction and inflammation in terms of cell death in vivo, and addresses how this novel approach can be used to improve our understanding of cell death dynamics in renal disease.

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Predictive Value of Matrix Metalloproteinases and Their Inhibitors for Mortality in Septic Patients: A Cohort Study

Purpose:

Over 170 biomarkers are being investigated regarding their prognostic and diagnostic accuracy in sepsis in order to find new tools to reduce morbidity and mortality. Matrix metalloproteinases (MMPs) and their inhibitors have been recently studied as promising new prognostic biomarkers in patients with sepsis. This study is aimed at determining the utility of several cutoff points of these biomarkers to predict mortality in patients with sepsis.

Materials and Methods:

A multicenter, prospective, analytic cohort study was performed in the metropolitan area of Bucaramanga, Colombia. A total of 289 patients with sepsis and septic shock were included. MMP-9, MMP-2, tissue inhibitor of metalloproteinase 1 (TIMP-1), TIMP-2, TIMP-1/MMP-9 ratio, and TIMP-2/MMP-2 ratio were determined in blood samples. Value ranges were correlated with mortality to estimate sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiving operating characteristic curve.

Results:

Sensitivity ranged from 33.3% (MMP-9/TIMP-1 ratio) to 60.6% (TIMP-1) and specificity varied from 38.8% (MMP-2/TIMP-2 ratio) to 58.5% (TIMP-1). As for predictive values, positive predictive value range was from 17.5% (MMP-9/TIMP-1 ratio) to 70.4% (MMP-2/TIMP-2 ratio), whereas negative predictive values were between 23.2% (MMP-2/TIMP-2 ratio) and 80.9% (TIMP-1). Finally, area under the curve scores ranged from 0.31 (MMP-9/TIMP-1 ratio) to 0.623 (TIMP-1).

Conclusion:

Although TIMP-1 showed higher sensitivity, specificity, and negative predictive value, with a representative population sample, we conclude that none of the evaluated biomarkers had significant predictive value for mortality.

Association of Matrix Metalloproteinases -7, -8 and -9 and TIMP -1 with Disease Severity in Acute Pancreatitis. A Cohort Study

Objectives

Several biomarkers for early detection of severe acute pancreatitis (SAP) have been presented. Matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) are released early in inflammation. We aimed to assess levels of MMP-7, -8, -9 and TIMP-1 in acute pancreatitis (AP) and explore their ability to detect disease severity. Our second aim was to find an association between MMPs, TIMP and creatinine.

Methods

We collected plasma samples for MMP-7, -8, -9 and TIMP-1 analyses from 176 patients presenting within 96 h from onset of acute pancreatitis (AP) symptoms. We used samples from 32 control subjects as comparison. The revised Atlanta Classification was utilised to assess severity of disease. Receiver operating characteristic curve analysis and Spearman´s Rho-test were utilised for statistical calculations.

Results

Compared with controls, patients showed higher levels of all studied markers. MMP-8 was higher in moderately severe AP than in mild AP (p = 0.005) and MMP-8, -9 and TIMP-1 were higher in severe than in mild AP (p<0.001, p = 0.005 and p = 0.019). MMP-8 detected SAP with an AUC of 0.939 [95% CI 0.894–0.984], LR+ 9.03 [5.30–15.39]. MMP-8, -9 and TIMP-1 failed to discern moderately severe AP from SAP. MMP-7 was not different between patient groups. MMP-7 and TIMP-1 correlated weakly with creatinine (Rho = 0.221 and 0.243). MMP-8 might be a useful biomarker in early detection of SAP.