Serum or plasma samples? The "Cinderella" role of blood collection procedures: preanalytical methodological issues influence the release and activity of circulating matrix metalloproteinases and their tissue inhibitors, hampering diagnostic trueness and leading to misinterpretation

Plasma Matrix Metalloproteinase Concentrations and Risk of Interstitial Lung Disease in a Prospective Rheumatoid Arthritis Cohort

OBJECTIVE

To evaluate the associations of plasma matrix metalloproteinases (MMPs) with prevalent and incident interstitial lung disease (ILD) in people with rheumatoid arthritis (RA).

METHODS

Within a multicenter, prospective cohort of US veterans with RA, we performed a cross-sectional study of prevalent ILD and cohort study of incident ILD. ILD diagnoses were validated by medical record review of provider diagnoses and chest imaging and/or pathology reports. MMP-1, 3, 7, and 9 concentrations were measured in plasma samples, then standardized and categorized into quartiles. The associations of MMPs with prevalent and incident ILD were assessed with logistic (prevalent) and Cox (incident) regression models adjusted for RA-ILD risk factors.

RESULTS

Among 2,312 participants (88.9% male; mean age 63.8 years), 96 had prevalent ILD. Incident ILD developed in 130 participants over 17,378 person-years of follow-up (crude incidence rate 7.5/1,000 person-years). Participants with the highest quartile of MMP-7 concentrations had a nearly four-fold increased odds of prevalent ILD (adjusted odds ratio 3.78 [95% confidence interval (95% CI) 1.86-7.65]) and over two-fold increased risk of incident ILD (adjusted hazard ratio 2.33 [95% CI 1.35-4.02]). Higher MMP-9 concentrations were also associated with prevalent and incident ILD, as well as negatively correlated with forced vital capacity among those with prevalent ILD (r = -0.30, P = 0.005).

CONCLUSION

MMP-7 and MMP-9 were strongly associated with both prevalent and incident ILD in this large, multicenter RA cohort after adjustment for other RA-ILD risk factors. These population-level findings further support a potential pathogenic role for MMPs in RA-ILD and suggest that their measurement could facilitate RA-ILD risk stratification.

MMP-9 upregulation may predict hemorrhagic transformation after endovascular thrombectomy

Background

Hemorrhagic transformation (HT) is a serious complication after endovascular thrombectomy (EVT) for patients with acute ischemic stroke (AIS). We analyzed the plasma levels of MMP-9 before and after EVT and assessed the temporal changes of MMP-9 that may be associated with, and therefore predict, HT after EVT.

Methods

We enrolled 30 AIS patients who received EVT, and 16 (53.3%) developed HT. The levels of MMP-9 in plasma collected from the arteries of AIS patients before and immediately after EVT were measured using ELISA. The percent change in MMP-9 after EVT (after/before) was calculated and compared between patients with and without HT.

Results

The median age of the AIS patients was 70 years, and 13 patients (43.3%) were men. The median National Institutes of Health Stroke Scale (NIHSS) scores of patients with HT were 18 on admission and 18 after EVT. The median NIHSS scores of patients without HT were 17 on admission and 11 after EVT. Patients with HT demonstrated significantly greater percentage increases in arterial MMP-9 levels after EVT.

Conclusion

Patients with AIS who developed HT had significantly increased arterial MMP-9 levels after EVT, suggesting that the upregulation of MMP-9 following EVT could serve as a predictive biomarker for HT.

Crimson clues: advancing endometriosis detection and management with novel blood biomarkers

Endometriosis is an inflammatory condition affecting approximately 10% of the female-born population. Despite its prevalence, the lack of noninvasive biomarkers has contributed to an established global diagnostic delay. The intricate pathophysiology of this enigmatic disease may leave signatures in the blood, which, when detected, can be used as noninvasive biomarkers. This review provides an update on how investigators are utilizing the established disease pathways and innovative methodologies, including genome-wide association studies, next-generation sequencing, and machine learning, to unravel the clues left in the blood to develop blood biomarkers. Many blood biomarkers show promise in the discovery phase, but because of a lack of standardized and robust methodologies, they rarely progress to the development stages. However, we are now seeing biomarkers being validated with high diagnostic accuracy and improvements in standardization protocols, providing promise for the future of endometriosis blood biomarkers.

Plasma type I collagen α1 chain in relation to coronary artery disease: findings from a prospective population-based cohort and an acute myocardial infarction prospective cohort in Sweden

OBJECTIVES

To investigate the association between type I collagen α1 chain (COL1α1) levels and coronary artery disease (CAD) by using absolute quantification in plasma. Also, to investigate the correlates of COL1α1 to clinical characteristics and circulating markers of collagen metabolism.

DESIGN

Life conditions, Stress and Health (LSH) study: prospective cohort study, here with a nested case-control design.Assessing Platelet Activity in Coronary Heart Disease (APACHE) study: prospective cohort study.

SETTING

LSH: primary care setting, southeast Sweden.APACHE: cardiology department, university hospital, southeast Sweden.

PARTICIPANTS

LSH: 1007 randomly recruited individuals aged 45-69 (50% women). Exclusion criteria was serious disease. After 13 years of follow-up, 86 cases with primary endpoint were identified and sex-matched/age-matched to 184 controls.

APACHE

125 patients with myocardial infarction (MI), 73 with ST-elevation MI and 52 with non-ST-elevation MI.

EXCLUSION CRITERIA

Intervention study participation, warfarin treatment and short life expectancy.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was the association between baseline COL1α1 and first-time major event of CAD, defined as fatal/non-fatal MI or coronary revascularisation after 13 years. Secondary outcomes were the association between the collagen biomarkers PRO-C1 (N-terminal pro-peptide of type I collagen)/C1M (matrix metalloproteinase-mediated degradation of type I collagen) and CAD; temporal change of COL1α1 after acute MI up to 6 months and lastly, correlates between COL1α1 and patient characteristics along with circulating markers of collagen metabolism.

RESULTS

COL1α1 levels were associated with CAD, both unadjusted (HR=0.69, 95% CI=0.56 to 0.87) and adjusted (HR=0.55, 95% CI=0.41 to 0.75). PRO-C1 was associated with CAD, unadjusted (HR=0.62, 95% CI=0.47 to 0.82) and adjusted (HR=0.61, 95% CI=0.43 to 0.86), while C1M was not. In patients with MI, COL1α1 remained unchanged up to 6 months. COL1α1 was correlated to PRO-C1, but not to C1M.

CONCLUSIONS

Plasma COL1α1 was independently and inversely associated with CAD. Furthermore, COL1α1 appeared to reflect collagen synthesis but not degradation. Future studies are needed to confirm whether COL1α1 is a clinically useful biomarker of CAD.

Comparison between 5 extractions methods in either plasma or serum to determine the optimal extraction and matrix combination for human metabolomics

BACKGROUND

Although metabolomics continues to expand in many domains of research, methodological issues such as sample type, extraction and analytical protocols have not been standardized, impeding proper comparison between studies and future research.

METHODS

In the present study, five solvent-based and solid-phase extraction methods were investigated in both plasma and serum. All these extracts were analyzed using four liquid chromatography coupled with high resolution mass spectrometry (LC-MS) protocols, either in reversed or normal-phase and with both types of ionization. The performances of each method were compared according to putative metabolite coverage, method repeatability and also extraction parameters such as overlap, linearity and matrix effect; in both untargeted (global) and targeted approaches using fifty standard spiked analytes.

RESULTS

Our results verified the broad specificity and outstanding accuracy of solvent precipitation, namely methanol and methanol/acetonitrile. We also reveal high orthogonality between methanol-based methods and SPE, providing the possibility of increased metabolome coverage, however we highlight that such potential benefits must be weighed against time constrains, sample consumption and the risk of low reproducibility of SPE method. Furthermore, we highlighted the careful consideration about matrix choice. Plasma showed the most suitable in this metabolomics approach combined with methanol-based methods.

CONCLUSIONS

Our work proposes to facilitate rational design of protocols towards standardization of these approaches to improve the impact of metabolomics research.

A combination of matrix stiffness and degradability dictate microvascular network assembly and remodeling in cell-laden poly(ethylene glycol) hydrogels

The formation of functional capillary blood vessels that can sustain the metabolic demands of transplanted parenchymal cells remains one of the biggest challenges to the clinical realization of engineered tissues for regenerative medicine. As such, there remains a need to better understand the fundamental influences of the microenvironment on vascularization. Poly(ethylene glycol) (PEG) hydrogels have been widely adopted to interrogate the influence of matrix physicochemical properties on cellular phenotypes and morphogenetic programs, including the formation of microvascular networks, in part due to the ease with which their properties can be controlled. In this study, we co-encapsulated endothelial cells and fibroblasts in PEG-norbornene (PEGNB) hydrogels in which stiffness and degradability were tuned to assess their independent and synergistic effects on vessel network formation and cell-mediated matrix remodeling longitudinally. Specifically, we achieved a range of stiffnesses and differing rates of degradation by varying the crosslinking ratio of norbornenes to thiols and incorporating either one (sVPMS) or two (dVPMS) cleavage sites within the matrix metalloproteinase- (MMP-) sensitive crosslinker, respectively. In less degradable sVPMS gels, decreasing the crosslinking ratio (thereby decreasing the initial stiffness) supported enhanced vascularization. When degradability was increased in dVPMS gels, all crosslinking ratios supported robust vascularization regardless of initial mechanical properties. The vascularization in both conditions was coincident with the deposition of extracellular matrix proteins and cell-mediated stiffening, which was greater in dVPMS conditions after a week of culture. Collectively, these results indicate that enhanced cell-mediated remodeling of a PEG hydrogel, achieved either by reduced crosslinking or increased degradability, leads to more rapid vessel formation and higher degrees of cell-mediated stiffening.

Reproducibility of double agar gel immunodiffusion test using stored serum and plasma from paracoccidioidomycosis patients

Background

Serological evaluation performed by double agar gel immunodiffusion test (DID) is used for diagnosis, evaluation of severity, management of paracoccidioidomycosis patients, and development of new clinical studies. For these reasons, the Botucatu Medical School of UNESP maintains a serum bank at the Experimental Research Unit with patient clinical data. This study aimed to evaluate the influence of the freeze-thaw cycle and different blood matrices on the titration of circulating antibodies.

Methods

The study included 207 patients with confirmed (etiology-demonstrated) or probable (serology-demonstrated) paracoccidioidomycosis, and DID was performed with culture filtrate from Paracoccidioides brasiliensis B339 as antigen. First experiment: the antibody levels were determined in serum samples from 160 patients with the chronic form and 20 with the acute/subacute form, stored at -80^oC for more than six months. Second experiment: titers of 81 samples of serum and plasma with ethylenediaminetetraacetic acid (EDTA) or heparin, from 27 patients, were compared according to matrix and effect of storage at -20^oC for up to six months. Differences of titers higher than one dilution were considered discordant.

Results

First experiment: test and retest presented concordant results in serum stored for up to three years, and discordant titers in low incidence in storage for four to six years but high incidence when stored for more than six years, including conversion from reagent test to non-reagent retest. Second experiment: serum, plasma-EDTA and plasma-heparin samples showed concordant titers, presenting direct correlation, with no interference of storage for up to six months.

Conclusions

Storage at -80^oC for up to six years has no or little influence on the serum titers determined by DID, permitting its safe use in studies depending on this parameter. The concordant titrations in different blood matrices demonstrated that the plasma can be used for immunodiffusion test in paracoccidioidomycosis, with stability for at least six months after storage at -20^oC.

Plasma versus Serum Analysis by FTIR Spectroscopy to Capture the Human Physiological State

Fourier Transform InfraRed spectroscopy of serum and plasma has been highly explored for medical diagnosis, due to its general simplicity, and high sensitivity and specificity. To evaluate the plasma and serum molecular fingerprint, as obtained by FTIR spectroscopy, to acquire the system metabolic state, serum and plasma spectra were compared to characterize the metabolic state of 30 human volunteers, between 90 days consumption of green tea extract rich in Epigallocatechin-3-gallate (EGCG). Both plasma and serum spectra enabled the high impact of EGCG consumption on the biofluid spectra to be observed, as analyzed by the spectra principal component analysis, hierarchical-cluster analysis, and univariate data analysis. Plasma spectra resulted in the prediction of EGCG consumption with a slightly higher specificity, accuracy, and precision, also pointing to a higher number of significant spectral bands that were different between the 90 days period. Despite this, the lipid regions of the serum spectra were more affected by EGCG consumption than the corresponding plasma spectra. Therefore, in general, if no specific compound analysis is highlighted, plasma is in general the advised biofluid to capture by FTIR spectroscopy the general metabolic state. If the lipid content of the biofluid is relevant, serum spectra could present some advantages over plasma spectra.

An Exploratory Study Provides Insights into MMP9 and Aβ Levels in the Vitreous and Blood across Different Ages and in a Subset of AMD Patients

Matrix metalloproteinase-9 (MMP9) and total amyloid-beta (Aβ) are prospective biomarkers of ocular ageing and retinopathy. These were quantified by ELISA in the vitreous and blood from controls (n = 55) and in a subset of age-related macular degeneration (AMD) patients (n = 12) for insights and possible additional links between the ocular and systemic compartments. Vitreous MMP9 levels in control and AMD groups were 932.5 ± 240.9 pg/mL and 813.7 ± 157.6 pg/mL, whilst serum levels were 2228 ± 193 pg/mL and 2386.8 ± 449.4 pg/mL, respectively. Vitreous Aβ in control and AMD groups were 1173.5 ± 117.1 pg/mL and 1275.6 ± 332.9 pg/mL, whilst plasma Aβ were 574.3 ± 104.8 pg/mL and 542.2 ± 139.9 pg/mL, respectively. MMP9 and Aβ showed variable levels across the lifecourse, indicating no correlation to each other or with age nor AMD status, though the smaller AMD cohort was a limiting factor. Aβ and MMP9 levels in the vitreous and blood were unrelated to mean arterial pressure. Smoking, another modifiable risk, showed no association with vitreous Aβ. However, smoking may be linked with vitreous (p = 0.004) and serum (p = 0.005) MMP9 levels in control and AMD groups, though this did not reach our elevated (p = 0.001) significance. A bioinformatics analysis revealed promising MMP9 and APP/Aβ partners for further scrutiny, many of which are already linked with retinopathy.

Assessment of Changes in Physiological Markers in Different Body Fluids at Rest and after Exercise

Physiological and biological markers in different body fluids are used to measure the body’s physiological or pathological status. In the field of sports and exercise medicine, the use of these markers has recently become more popular for monitoring an athlete’s training response and assessing the immediate or long-term effects of exercise. Although the effect of exercise on different physiological markers using various body fluids is well substantiated, no article has undertaken a review across multiple body fluids such as blood, saliva, urine and sweat. This narrative review aims to assess various physiological markers in blood, urine and saliva, at rest and after exercise and examines physiological marker levels obtained across similar studies, with a focus on the population and study methodology used. Literature searches were conducted using PRISMA guidelines for keywords such as exercise, physical activity, serum, sweat, urine, and biomarkers, resulting in an analysis of 15 studies for this review paper. When comparing the effects of exercise on physiological markers across different body fluids (blood, urine, and saliva), the changes detected were generally in the same direction. However, the extent of the change varied, potentially as a result of the type and duration of exercise, the sample population and subject numbers, fitness levels, and/or dietary intake. In addition, none of the studies used solely female participants; instead, including males only or both male and female subjects together. The results of some physiological markers are sex-dependent. Therefore, to better understand how the levels of these biomarkers change in relation to exercise and performance, the sex of the participants should also be taken into consideration.

Molecular Clustering Analysis of Blood Biomarkers in World Trade Center Exposed Community Members with Persistent Lower Respiratory Symptoms

The destruction of the World Trade Center (WTC) on September 11, 2001 (9/11) released large amounts of toxic dusts and fumes into the air that exposed many community members who lived and/or worked in the local area. Many community members, defined as WTC survivors by the federal government, developed lower respiratory symptoms (LRS). We previously reported the persistence of these symptoms in patients with normal spirometry despite treatment with inhaled corticosteroids and/or long-acting bronchodilators. This report expands upon our study of this group with the goal to identify molecular markers associated with exposure and heterogeneity in WTC survivors with LRS using a selected plasma biomarker approach. Samples from WTC survivors with LRS (n = 73, WTCS) and samples from healthy control participants of the NYU Bellevue Asthma Registry (NYUBAR, n = 55) were compared. WTCS provided information regarding WTC dust exposure intensity. Hierarchical clustering of the linear biomarker data identified two clusters within WTCS and two clusters within NYUBAR controls. Comparison of the WTCS clusters showed that one cluster had significantly increased levels of circulating matrix metalloproteinases (MMP1, 2, 3, 8, 12, 13), soluble inflammatory receptors (receptor for advanced glycation end-products-RAGE, Interleukin-1 receptor antagonist (IL-1RA), suppression of tumorigenicity (ST)2, triggering receptor expressed on myeloid cells (TREM)1, IL-6Ra, tumor necrosis factor (TNF)RI, TNFRII), and chemokines (IL-8, CC chemokine ligand- CCL17). Furthermore, this WTCS cluster was associated with WTC exposure variables, ash at work, and the participant category workers; but not with the exposure variable WTC dust cloud at 9/11. A comparison of WTC exposure categorial variables identified that chemokines (CCL17, CCL11), circulating receptors (RAGE, TREM1), MMPs (MMP3, MMP12), and vascular markers (Angiogenin, vascular cell adhesion molecule-VCAM1) significantly increased in the more exposed groups. Circulating biomarkers of remodeling and inflammation identified clusters within WTCS and were associated with WTC exposure.

Changes in Serum Levels of Matrix Metalloproteinase-1 and Tissue Inhibitor of Metalloproteinases-1 in Patients with Essential Hypertension

Hypertension (HTN) is a leading risk factor for cardiovascular (CV) disease. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are thought to be actively involved in the remodeling of the CV extracellular matrix (ECM) during hypertensive damage. Therefore, in this study, we aimed to investigate serum levels of MMP-1 and TIMP-1 in patients with essential HTN and compare them with those of normotensive individuals. We measured serum concentrations of MMP-1 and TIMP-1 in 60 patients with HTN and 20 healthy controls using an ELISA. The obtained results showed that in patients with HTN, the mean levels of MMP-1 (1.82 ± 0.9 ng/mL) were significantly higher (p = 0.03) than the mean levels in the control group (1.19 ± 0.7 ng/mL). The levels of TIMP-1 in patients with essential HTN (0.44 ± 0.1 ng/mL) were also significantly higher (p = 0.005) than those in the control group (0.33 ± 0.1 ng/mL). In HTN, elevated serum MMP-1 levels may be associated with increased collagen degradation in the CV ECM, whereas elevated TIMP-1 levels may favor its accumulation and the development of pathological remodeling and fibrosis of the heart and arterial vessels.

Clinical Proteomics of Biofluids in Haematological Malignancies

Since the emergence of high-throughput proteomic techniques and advances in clinical technologies, there has been a steady rise in the number of cancer-associated diagnostic, prognostic, and predictive biomarkers being identified and translated into clinical use. The characterisation of biofluids has become a core objective for many proteomic researchers in order to detect disease-associated protein biomarkers in a minimally invasive manner. The proteomes of biofluids, including serum, saliva, cerebrospinal fluid, and urine, are highly dynamic with protein abundance fluctuating depending on the physiological and/or pathophysiological context. Improvements in mass-spectrometric technologies have facilitated the in-depth characterisation of biofluid proteomes which are now considered hosts of a wide array of clinically relevant biomarkers. Promising efforts are being made in the field of biomarker diagnostics for haematologic malignancies. Several serum and urine-based biomarkers such as free light chains, β-microglobulin, and lactate dehydrogenase are quantified as part of the clinical assessment of haematological malignancies. However, novel, minimally invasive proteomic markers are required to aid diagnosis and prognosis and to monitor therapeutic response and minimal residual disease. This review focuses on biofluids as a promising source of proteomic biomarkers in haematologic malignancies and a key component of future diagnostic, prognostic, and disease-monitoring applications.

Serum MMP-3 and its association with central arterial stiffness among young adults is moderated by smoking and BMI

Central arterial stiffness is an independent predictor of cardiovascular disease. It is characterized by a marked reduction in the elastin-collagen ratio of the arterial wall extracellular matrix (ECM), and is largely the result of degradation of various ECM components. Matrix metalloproteinase-3 (MMP-3) may contribute to central arterial stiffness via its involvement in ECM homeostasis and remodeling. This study examined the association between serum MMP-3 concentrations and central arterial stiffness and potential interactions of MMP-3 and traditional cardiovascular risk factors in a population of healthy young adults. A total of 206 participants (n = 109 females) aged 19-25 years were included in the current study. Central arterial stiffness was measured non-invasively as carotid-femoral pulse wave velocity (cfPWV) (m/s). MMP-3 concentrations (ng/ml) were measured using ELISA techniques. Regression analyses were used to examine the association between cfPWV and MMP-3, adjusting for age, sex, smoking status, body mass index (BMI), instantaneous mean arterial pressure (MAP) and heart rate, and serum C-reactive protein. Interactions between MMP-3 with smoking, BMI, sex, and MAP were analyzed in subsequent regression models. MMP-3 was an independent predictor of cfPWV (β = 0.187, p = 0.007), and significant interactions between MMP-3 and regular smoking (β = 0.291, p = 0.022), and MMP-3 and BMI (β = 0.210, p = 0.013) were observed. Higher serum MMP-3 concentrations were associated with a faster cfPWV and thus, greater central arterial stiffness. Interactions between MMP-3 and smoking, and MMP-3 and BMI may, in part, drive the association between MMP-3 and central arterial stiffness.

Protein signatures of centenarians and their offspring suggest centenarians age slower than other humans

Using samples from the New England Centenarian Study (NECS), we sought to characterize the serum proteome of 77 centenarians, 82 centenarians' offspring, and 65 age-matched controls of the offspring (mean ages: 105, 80, and 79 years). We identified 1312 proteins that significantly differ between centenarians and their offspring and controls (FDR < 1%), and two different protein signatures that predict longer survival in centenarians and in younger people. By comparing the centenarian signature with 2 independent proteomic studies of aging, we replicated the association of 484 proteins of aging and we identified two serum protein signatures that are specific of extreme old age. The data suggest that centenarians acquire similar aging signatures as seen in younger cohorts that have short survival periods, suggesting that they do not escape normal aging markers, but rather acquire them much later than usual. For example, centenarian signatures are significantly enriched for senescence-associated secretory phenotypes, consistent with those seen with younger aged individuals, and from this finding, we provide a new list of serum proteins that can be used to measure cellular senescence. Protein co-expression network analysis suggests that a small number of biological drivers may regulate aging and extreme longevity, and that changes in gene regulation may be important to reach extreme old age. This centenarian study thus provides additional signatures that can be used to measure aging and provides specific circulating biomarkers of healthy aging and longevity, suggesting potential mechanisms that could help prolong health and support longevity.

Recent progress in the LC-MS/MS analysis of oxidative stress biomarkers

The presence of a dynamic and balanced equilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and the in-house antioxidant defense mechanisms is characteristic for a healthy body. During oxidative stress (OS), this balance is switched to increased production of ROS and RNS, exceeding the capacity of physiological antioxidant systems. This can cause damage to biological molecules, leading to loss of function and even cell death. Nowadays, there is increasing scientific and clinical interest in OS and the associated parameters to measure the degree of OS in biofluids. An increasing number of reports using LC-MS/MS methods for the analysis of OS biomarkers can be found. Since bioanalysis is usually complicated by matrix effects, various types of cleanup procedures are used to effectively separate the biomarkers from the matrix. This is an essential part of the analysis to prepare a reproducible and homogenous solution suitable for injection onto the column. The present review gives a summary of the chromatographic methods used for the determination of OS biomarkers in both urine and plasma, serum, and whole blood samples. The first part mainly describes the biological background of the different OS biomarkers, while the second part reports examples of chromatographic methods for the analysis of different metabolites connected with OS in biofluids, covering a period from 2015 till early 2020. The selected examples mainly include LC-MS/MS methods for isoprostanes, oxidized proteins, oxidized lipoproteins, and DNA/RNA biomarkers. The last part explains the clinical relevance of this review.

MMP-2 and MMP-9 in Human Peripheral Blood: Optimizing Gelatinase Calibrator for Degradome Research and Discovering a Novel Gelatinolytic Enzyme

Matrix metalloprotease-2 and -9 (gelatinase A and B, respectively) are enzymes crucially involved in a plethora of physiopathological conditions. Gelatin zymography is considered one of the major qualitative/semiquantitative assays for simultaneously determining zymogenic, active, and complexed forms of gelatinases. Critical steps are represented by variations in sample collection methods, molecular weight standard calibrators, and different zymography assay protocols. A normalization of these aspects is required for reducing discrepancies in technical procedures and interpreting results among different laboratories. In this study, we describe a novel protocol for gelatin zymography with increased pore size, which improves the separation of gelatinases with different molecular weights. A new method for obtaining gelatinase calibrator for gelatin zymography, by extracting MMP-2 and MMP-9 from peripheral blood, is also reported. Our method provides a gelatinase calibrator with enhanced stability both at room temperature and during multiple freeze-thaw cycles. This calibrator preparation is also suitable for in vitro post-translational modifications. For the first time, the improved zymography protocol allowed us to reveal in human peripheral blood samples new gelatinolytic bands resolved at very high molecular weight, likely complexes of MMP-9, undetectable with classical zymography protocols.

Sample management for clinical biochemistry assays: Are serum and plasma interchangeable specimens?

The constrained economic context leads laboratories to centralize their routine analyses on high-throughput platforms, to which blood collection tubes are sent from peripheral sampling sites that are sometimes distantly located. Providing biochemistry results as quickly as possible implies to consolidate the maximum number of tests on a minimum number of blood collection tubes, mainly serum tubes and/or tubes with anticoagulants. However, depending on the parameters and their pre-analytical conditions, the type of matrix - serum or plasma - may have a significant impact on results, which is often unknown or underestimated in clinical practice. Importantly, the matrix-related effects may be a limit to the consolidation of analyses on a single tube, and thus must be known by laboratory professionals. The purpose of the present critical review is to put forward the main differences between using serum and plasma samples on clinical biochemistry analyses, in order to sensitize laboratory managers to the need for standardization. To enrich the debate, we also provide an additional comparison of serum and plasma concentrations for approximately 30 biochemistry parameters. Properties, advantages, and disadvantages of serum and plasma are discussed from a pre-analytical standpoint - before, during, and after centrifugation - with an emphasis on the importance of temperature, delay, and transport conditions. Then, differences in results between these matrices are addressed for many classes of biochemistry markers, particularly proteins, enzymes, electrolytes, lipids, circulating nucleic acids, metabolomics markers, and therapeutic drugs. Finally, important key-points are proposed to help others choose the best sample matrix and guarantee quality of clinical biochemistry assays. Moreover, awareness of the implications of using serum and plasma samples on various parameters assayed in the laboratory is an important requirement to ensure reliable results and improve patient care.

Impact of biological matrix on inflammatory protein biomarker quantification based on targeted mass spectrometry

Background: Serum and plasma are widely used matrices in biological and clinical studies. To improve reliability and consistency of markers quantification, the influence of these matrices on proteins was evaluated by targeted mass spectrometry. Results: 65 proteins were quantified in matched blood samples collected in serum, ethylenediaminetetraacetic acid and heparin plasma tubes from 40 healthy and 10 pathological individuals. Only 52% of the proteins were not impacted by any of the biological matrices tested, and the effects on quantification of proteins affected was matrix and protein dependent. Conclusion: Matrix comparisons using mass spectrometry is therefore recommended to assess the relevance of using surrogate matrix, performing biomarker discovery study or evaluating the clinical use of biomarkers in large clinical cohorts.

Multiple Cold-Water Immersions Attenuate Muscle Damage but not Alter Systemic Inflammation and Muscle Function Recovery: A Parallel Randomized Controlled Trial

The aim of this study was to investigate the effects of multiple cold-water immersions (CWIs) on muscle function, markers of muscle damage, systemic inflammation and ECM degradation following exercise-induced muscle damage (EIMD). Thirty physically active males were randomly assigned to either a control (n = 15) or cold-water immersion (CWI) group (n = 15). The CWI group performed one immersion (10 °C for 20 min) at post-exercise and every 24 h for the following 72 h, while the control group remained in a seated position during these corresponding periods. Muscle strength, vertical jump height, muscle thickness, delayed-onset muscle soreness (DOMS), systemic creatine kinase (CK), C-reactive protein (CRP), inflammatory cytokines and matrix metalloproteinase-2 (MMP-2) activity were assessed at Pre, Post, 24, 48, 72, 96 and 168 h following EIMD. No significant time × group interaction was obtained for muscle strength, vertical jump height recovery and MMP-2 activity (p > 0.05). At 24 h, muscle thickness from the CWI group returned to baseline and was lower than the control (p = 0.04). DOMS returned to baseline at 168 h for the CWI group (p = 0.109) but not for the control (p = 0.008). At 168 h, CK showed a time-group difference with a greater peak for the control group (p = 0.016). In conclusion, multiple CWIs attenuated muscle damage, but not altered systemic inflammation and muscle function recovery.

Circulating Biomarkers Predictive of Postoperative Atrial Fibrillation

Postoperative atrial fibrillation (PoAF), a common complication of cardiac surgery, contributes significantly to morbidity, mortality, and increasing healthcare costs. Despite advances in surgical and medical management, the overall incidence of PoAF has not changed significantly, partly because of the limited understanding of mechanisms underlying acute surgery-related factors, such as myocardial injury, inflammation, sympathetic activation, and oxidative stress, which play an important role in the initiation of PoAF, whereas a preexisting atrial substrate appears to be more important in the maintenance of this dysrhythmia. Thus, in a majority of patients, PoAF becomes a manifestation of an underlying arrhythmogenic substrate that is unmasked after acute surgical stress. As such, the ability to identify which patients have this proarrhythmic substrate and are, therefore, at high risk for developing AF postoperatively, is important for the improved selection for prophylactic interventions, closer monitoring for complications, and establishing the probability of AF in the long term. This review highlights the role of the underlying substrate in promoting PoAF, proposed mechanisms, and the potential role of serum biomarkers to identify patients at risk for PoAF.

Adapting extracellular matrix proteomics for clinical studies on cardiac remodeling post-myocardial infarction

Following myocardial infarction (MI), the left ventricle (LV) undergoes a series of cardiac wound healing responses that involve stimulation of robust inflammation to clear necrotic myocytes and tissue debris and induction of extracellular matrix (ECM) protein synthesis to generate a scar. Proteomic strategies provide us with a means to index the ECM proteins expressed in the LV, quantify amounts, determine functions, and explore interactions. This review will focus on the efforts taken in the proteomics research field that have expanded our understanding of post-MI LV remodeling, concentrating on the strengths and limitations of different proteomic approaches to glean information that is specific to ECM turnover in the post-MI setting. We will discuss how recent advances in sample preparation and labeling protocols increase our successes at detecting components of the cardiac ECM proteome. We will summarize how proteomic approaches, focusing on the ECM compartment, have progressed over time to current gel-free methods using decellularized fractions or labeling strategies that will be useful for clinical applications. This review will provide an overview of how cardiac ECM proteomics has evolved over the last decade and will provide insight into future directions that will drive forward our understanding of cardiac ECM turnover in the post-MI LV.

Human plasma and human platelet-rich plasma as a substitute for fetal calf serum during long-term cultivation of mesenchymal dental pulp stem cells

AIMS

Our aims were to isolate and cultivate mesenchymal dental pulp stem cells (DPSC) in various media enriched with human blood components, and subsequently to investigate their basic biological properties.

METHODS

DPSC were cultivated in five different media based on α MEM containing different concentrations of human plasma (HP), platelet-rich plasma (PRP), or fetal calf serum (FCS). The DPSC biological properties were examined periodically.

RESULTS

We cultivated DPSC in the various cultivation media over 15 population doublings except for the medium supplemented with 10% HP. Our results showed that DPSC cultivated in medium supplemented with 10% PRP showed the shortest average population doubling time (DT) (28.6 ± 4.6 hours), in contrast to DPSC cultivated in 10% HP which indicated the longest DT (156.2 ± 17.8 hours); hence this part of the experiment had been cancelled in the 6th passage. DPSC cultivated in media with 2% FCS+ITS (DT 47.3 ± 10.4 hours), 2% PRP (DT 40.1 ± 5.7 hours) and 2% HP (DT 49.0 ± 15.2 hours) showed almost the same proliferative activity. DPSC's viability in the 9th passage was over 90% except for the DPSC cultivated in the 10% HP media.

CONCLUSIONS

We proved that human blood components are suitable substitution for FCS in cultivation media for long-term DPSC cultivation.

Gender-dependent differences in plasma matrix metalloproteinase-8 elevated in pulmonary tuberculosis

Tuberculosis (TB) remains a global health pandemic and greater understanding of underlying pathogenesis is required to develop novel therapeutic and diagnostic approaches. Matrix metalloproteinases (MMPs) are emerging as key effectors of tissue destruction in TB but have not been comprehensively studied in plasma, nor have gender differences been investigated. We measured the plasma concentrations of MMPs in a carefully characterised, prospectively recruited clinical cohort of 380 individuals. The collagenases, MMP-1 and MMP-8, were elevated in plasma of patients with pulmonary TB relative to healthy controls, and MMP-7 (matrilysin) and MMP-9 (gelatinase B) were also increased. MMP-8 was TB-specific (p<0.001), not being elevated in symptomatic controls (symptoms suspicious of TB but active disease excluded). Plasma MMP-8 concentrations inversely correlated with body mass index. Plasma MMP-8 concentration was 1.51-fold higher in males than females with TB (p<0.05) and this difference was not due to greater disease severity in men. Gender-specific analysis of MMPs demonstrated consistent increase in MMP-1 and -8 in TB, but MMP-8 was a better discriminator for TB in men. Plasma collagenases are elevated in pulmonary TB and differ between men and women. Gender must be considered in investigation of TB immunopathology and development of novel diagnostic markers.

The importance of sample collection when using single cytokine levels and systemic cytokine profiles as biomarkers--a comparative study of serum versus plasma samples

BACKGROUND

Cytokines, soluble adhesion molecules and metalloproteinases can be detected in human serum or plasma samples. Such systemic levels are widely used as biomarkers in epidemiological and clinical studies.

METHODS

We prepared serum samples and three types of plasma samples (EDTA, heparin, citric acid) from 20 healthy individuals. The levels of 31 cytokines, four soluble adhesion molecules and eight matrix metalloproteinases were analyzed by Luminex technology.

RESULTS

Most mediators showed detectable levels in both plasma and serum. Several mediators that can be released by platelets showed increased serum levels, especially CCL5 and CD40L, but for the other mediators the serum levels did not correlate with peripheral blood platelet counts and for these last mediators serum and plasma levels often showed strong correlations. The use of bivalirudin for anticoagulation significantly increased and citric acid combined with platelet inhibitors (ticagrelor, acetylsalicylic acid plus prostaglandin E2) did not alter plasma levels of platelet-store mediators compared with citric acid alone. The impact of sample preparation differed between mediators; for many mediators strong correlations were seen between serum and plasma levels even when absolute levels differed. Soluble adhesion molecule levels showed only minor differences between samples. Unsupervised hierarchical clustering suggested that the effect of sampling/preparation was strongest for serum and heparin plasma samples.

CONCLUSION

Careful standardization of sample preparation is usually necessary when analyzing systemic mediator levels, and differences caused by sample preparation should be considered as a possible explanation if studies show conflicting results.

Quantitative mass spectrometric immunoassay for the chemokine RANTES and its variants

The chemokine RANTES plays a key role in inflammation, cell recruitment and T cell activation. RANTES is heterogenic and exists as multiple variants in vivo. Herein we describe the development and characterization of a fully quantitative mass spectrometric immunoassay (MSIA) for analysis of intact RANTES and its proteoforms in human serum and plasma samples. The assay exhibits linearity over a wide concentration range (1.56-200ng/mL), intra- and inter-assay precision with CVs <10%, and good linearity and recovery correlations. The assay was tested in different biological matrices, and it was benchmarked against an existing RANTES ELISA. The new RANTES MSIA was used to analyze RANTES and its proteoforms in a small clinical cohort, revealing the quantitative distribution and frequency of the native and truncated RANTES proteoforms.

BIOLOGICAL SIGNIFICANCE

In the last two decades, RANTES has been studied extensively due to its association with numerous clinical conditions, including kidney-related, autoimmune, cardiovascular, viral and metabolic pathologies. Although a single gene product, RANTES is expressed in a range of cells and tissues presenting with different endogenously produced variants and PTMs. The structural variety and population diversity that has been identified for RANTES necessitate developing advanced methodologies that can provide insight into the protein heterogeneity and its function and regulation in disease. In this work we present a simple, efficient and high-throughput mass spectrometric immunoassay (MSIA) method for analysis of RANTES proteoforms. RANTES MSIA can detect and analyze RANTES proteoforms and provide an insight into the endogenous protein modifications.

Matrix metalloproteinases in biologic samples

Matrix metalloproteinases (MMPs) are an important class of endopeptidases, having a role in a diverse range of physiological and pathological processes. This chapter provides an overview of the key regulatory processes in MMP production and activation. The common techniques used to assess MMP activity are discussed and their various strengths and weaknesses presented. This comparison of methodologies is specifically intended to aid any investigator who wishes to determine the most appropriate analytical method for their future studies because any investigation of MMPs in biological samples should be cognizant of the key mechanisms influencing the expression and activity of these proteinases. The endogenous, preanalytic and analytic chemistry of MMP activation influences the interpretation of the various techniques widely employed throughout the literature. Therefore, the ability to accurately evaluate the true endogenous activity of MMPs is heavily dependent on a clear understanding of these processes.

Rac1 regulates platelet shedding of CD40L in abdominal sepsis

Matrix metalloproteinase-9 (MMP-9) regulates platelet shedding of CD40L in abdominal sepsis. However, the signaling mechanisms controlling sepsis-induced shedding of CD40L from activated platelets remain elusive. Rac1 has been reported to regulate diverse functions in platelets; we hypothesized herein that Rac1 might regulate platelet shedding of CD40L in sepsis. The specific Rac1 inhibitor NSC23766 (N6-[2-[[4-(diethylamino)-1-methylbutyl] amino]-6-methyl-4-pyrimidinyl]-2 methyl-4, 6-quinolinediamine trihydrochloride) was administered to mice undergoing cecal ligation and puncture (CLP). Levels of CD40L and MMP-9 in plasma, platelets, and neutrophils were determined by use of ELISA, western blot, and confocal microscopy. Platelet depletion abolished the CLP-induced increase in plasma levels of CD40L. Rac1 activity was significantly increased in platelets from septic animals. Administration of NSC23766 abolished the CLP-induced enhancement of soluble CD40L levels in the plasma. Moreover, Rac1 inhibition completely inhibited proteinase-activated receptor-4-induced surface mobilization and secretion of CD40L in isolated platelets. CLP significantly increased plasma levels of MMP-9 and Rac1 activity in neutrophils. Treatment with NSC23766 markedly attenuated MMP-9 levels in the plasma from septic mice. In addition, Rac1 inhibition abolished chemokine-induced secretion of MMP-9 from isolated neutrophils. Finally, platelet shedding of CD40L was significantly reduced in response to stimulation with supernatants from activated MMP-9-deficient neutrophils compared with supernatants from wild-type neutrophils, indicating a direct role of neutrophil-derived MMP-9 in regulating platelet shedding of CD40L. Our novel data suggest that sepsis-induced platelet shedding of CD40L is dependent on Rac1 signaling. Rac1 controls surface mobilization of CD40L on activated platelets and MMP-9 secretion from neutrophils. Thus, our findings indicate that targeting Rac1 signaling might be a useful way to control pathologic elevations of CD40L in the systemic circulation in abdominal sepsis.

Mass spectrometry based biomarker discovery, verification, and validation--quality assurance and control of protein biomarker assays

In its early years, mass spectrometry (MS)-based proteomics focused on the cataloging of proteins found in different species or different tissues. By 2005, proteomics was being used for protein quantitation, typically based on "proteotypic" peptides which act as surrogates for the parent proteins. Biomarker discovery is usually done by non-targeted "shotgun" proteomics, using relative quantitation methods to determine protein expression changes that correlate with disease (output given as "up-or-down regulation" or "fold-increases"). MS-based techniques can also perform "absolute" quantitation which is required for clinical applications (output given as protein concentrations). Here we describe the differences between these methods, factors that affect the precision and accuracy of the results, and some examples of recent studies using MS-based proteomics to verify cancer-related biomarkers.

Interferences from blood collection tube components on clinical chemistry assays

Improper design or use of blood collection devices can adversely affect the accuracy of laboratory test results. Vascular access devices, such as catheters and needles, exert shear forces during blood flow, which creates a predisposition to cell lysis. Components from blood collection tubes, such as stoppers, lubricants, surfactants, and separator gels, can leach into specimens and/or adsorb analytes from a specimen; special tube additives may also alter analyte stability. Because of these interactions with blood specimens, blood collection devices are a potential source of pre-analytical error in laboratory testing. Accurate laboratory testing requires an understanding of the complex interactions between collection devices and blood specimens. Manufacturers, vendors, and clinical laboratorians must consider the pre-analytical challenges in laboratory testing. Although other authors have described the effects of endogenous substances on clinical assay results, the effects/impact of blood collection tube additives and components have not been well systematically described or explained. This review aims to identify and describe blood collection tube additives and their components and the strategies used to minimize their effects on clinical chemistry assays.

MRM for the verification of cancer biomarker proteins: recent applications to human plasma and serum

Accurate cancer biomarkers are needed for early detection, disease classification, prediction of therapeutic response and monitoring treatment. While there appears to be no shortage of candidate biomarker proteins, a major bottleneck in the biomarker pipeline continues to be their verification by enzyme linked immunosorbent assays. Multiple reaction monitoring (MRM), also known as selected reaction monitoring, is a targeted mass spectrometry approach to protein quantitation and is emerging to bridge the gap between biomarker discovery and clinical validation. Highly multiplexed MRM assays are readily configured and enable simultaneous verification of large numbers of candidates facilitating the development of biomarker panels which can increase specificity. This review focuses on recent applications of MRM to the analysis of plasma and serum from cancer patients for biomarker verification. The current status of this approach is discussed along with future directions for targeted mass spectrometry in clinical biomarker validation.

Comparison of serum, EDTA plasma and P100 plasma for luminex-based biomarker multiplex assays in patients with chronic obstructive pulmonary disease in the SPIROMICS study

Background

As a part of the longitudinal Chronic Obstructive Pulmonary Disease (COPD) study, Subpopulations and Intermediate Outcome Measures in COPD study (SPIROMICS), blood samples are being collected from 3200 subjects with the goal of identifying blood biomarkers for sub-phenotyping patients and predicting disease progression. To determine the most reliable sample type for measuring specific blood analytes in the cohort, a pilot study was performed from a subset of 24 subjects comparing serum, Ethylenediaminetetraacetic acid (EDTA) plasma, and EDTA plasma with proteinase inhibitors (P100™).

Methods

105 analytes, chosen for potential relevance to COPD, arranged in 12 multiplex and one simplex platform (Myriad-RBM) were evaluated in duplicate from the three sample types from 24 subjects. The reliability coefficient and the coefficient of variation (CV) were calculated. The performance of each analyte and mean analyte levels were evaluated across sample types.

Results

20% of analytes were not consistently detectable in any sample type. Higher reliability and/or smaller CV were determined for 12 analytes in EDTA plasma compared to serum, and for 11 analytes in serum compared to EDTA plasma. While reliability measures were similar for EDTA plasma and P100 plasma for a majority of analytes, CV was modestly increased in P100 plasma for eight analytes. Each analyte within a multiplex produced independent measurement characteristics, complicating selection of sample type for individual multiplexes.

Conclusions

There were notable detectability and measurability differences between serum and plasma. Multiplexing may not be ideal if large reliability differences exist across analytes measured within the multiplex, especially if values differ based on sample type. For some analytes, the large CV should be considered during experimental design, and the use of duplicate and/or triplicate samples may be necessary. These results should prove useful for studies evaluating selection of samples for evaluation of potential blood biomarkers.

Procollagen III N-terminal propeptide and desmosine are released by matrix destruction in pulmonary tuberculosis

BACKGROUND

Tuberculosis is transmitted by patients with pulmonary disease. Matrix metalloproteinases (MMPs) drive lung destruction in tuberculosis but the resulting matrix degradation products (MDPs) have not been studied. We investigate the hypothesis that MMP activity generates matrix turnover products as correlates of lung pathology.

METHODS

Induced sputum and plasma were collected prospectively from human immunodeficiency virus (HIV) positive and negative patients with pulmonary tuberculosis and controls. Concentrations of MDPs and MMPs were analyzed by ELISA and Luminex array in 2 patient cohorts.

RESULTS

Procollagen III N-terminal propeptide (PIIINP) was 3.8-fold higher in induced sputum of HIV-uninfected tuberculosis patients compared to controls and desmosine, released during elastin degradation, was 2.4-fold higher. PIIINP was elevated in plasma of tuberculosis patients. Plasma PIIINP correlated with induced sputum MMP-1 concentrations and radiological scores, demonstrating that circulating MDPs reflect lung destruction. In a second patient cohort of mixed HIV seroprevalence, plasma PIIINP concentration was increased 3.0-fold above controls (P < .001). Plasma matrix metalloproteinase-8 concentrations were also higher in tuberculosis patients (P = .001). Receiver operating characteristic analysis utilizing these 2 variables demonstrated an area under the curve of 0.832 (P < .001).

CONCLUSIONS

In pulmonary tuberculosis, MMP-driven immunopathology generates matrix degradation products.

Platelet shedding of CD40L is regulated by matrix metalloproteinase-9 in abdominal sepsis

BACKGROUND AND OBJECTIVES

Platelet-derived CD40L is known to regulate neutrophil recruitment and lung damage in sepsis. However, the mechanism regulating shedding of CD40L from activated platelets is not known. We hypothesized that matrix metalloproteinase (MMP)-9 might cleave surface-expressed CD40L and regulate pulmonary accumulation of neutrophils in sepsis.

METHODS

Abdominal sepsis was induced by cecal ligation and puncture (CLP) in wild-type and MMP-9-deficient mice. Edema formation, CXC chemokine levels, myeloperoxidase levels, neutrophils in the lung and plasma levels of CD40L and MMP-9 were quantified.

RESULTS

CLP increased plasma levels of MMP-9 but not MMP-2. The CLP-induced decrease in platelet surface CD40L and increase in soluble CD40L levels were significantly attenuated in MMP-9 gene-deficient mice. Moreover, pulmonary myeloperoxidase (MPO) activity and neutrophil infiltration in the alveolar space, as well as edema formation and lung injury, were markedly decreased in septic mice lacking MMP-9. In vitro studies revealed that inhibition of MMP-9 decreased platelet shedding of CD40L. Moreover, recombinant MMP-9 was capable of cleaving surface-expressed CD40L on activated platelets. In human studies, plasma levels of MMP-9 were significantly increased in patients with septic shock as compared with healthy controls, although MMP-9 levels did not correlate with organ injury score.

CONCLUSIONS

Our novel data propose a role of MMP-9 in regulating platelet-dependent infiltration of neutrophils and tissue damage in septic lung injury by controlling CD40L shedding from platelets. We conclude that targeting MMP-9 may be a useful strategy to limit acute lung injury in abdominal sepsis.

Diagnostic and prognostic role of matrix metalloproteases in cancer

BACKGROUND

Matrix metalloproteases (MMPs) are key players in the progression and metastasis of cancer. MMPs cleave extracellular matrix components and in this way promote tumor growth, invasion and vascularization. MMPs also affect tumor progression by regulating availability and activity of growth factors, inflammatory cytokines and chemokines. Accordingly, several MMPs have been found to serve as prognostic indicators in solid tumors. Usually the increased levels of MMPs in patients' tumor tissue or serum/plasma are associated with poor outcome. Interestingly, recent results show that certain MMPs also serve as tumor suppressors.

OBJECTIVE

This review discusses the latest view on MMPs as diagnostic and prognostic indicators in cancer patients.

METHODS

Studies with clinical samples of 70 or more patients are included in particular. In addition, the possible roles of MMPs in future molecular diagnostics and in the evaluation of therapeutic responses are discussed.

CONCLUSION

MMP-9 in particular has shown prognostic value in various types of tumor, and its measurement in circulation, urine or tumor tissue might help in clinical surveillance of otherwise problematic patient cases. There is upcoming new knowledge on MMPs in therapy response evaluation, in which MMPs might be useful together with CT scans and other clinically more established prognostic factors. Certain MMPs have a dual role in terms of cancer-modulating properties and thus it is essential to evaluate their expression and function in tumor cells and host environment to select validated therapy targets but spare MMP antitargets.

Novel association between plasma matrix metalloproteinase-9 and risk of incident atrial fibrillation in a case-cohort study: the Atherosclerosis Risk in Communities study

Background

Previous cross-sectional studies have suggested that biomarkers of extracellular matrix remodelling are associated with atrial fibrillation (AF), but no prospective data have yet been published. Hence, we examine whether plasma matrix metalloproteinases (MMP) and their inhibitors are related to increased risk of incident AF.

Methods

We used a case-cohort design in the context of the prospective Atherosclerosis Risk in Communities (ARIC) study. From 13718 eligible men and women free from AF in 1990-92, we selected a stratified random sample of 500 individuals without and 580 with incident AF over a mean follow-up of 11.8 years. Using a weighted proportional hazards regression model, the relationships between MMP-1, MMP-2, MMP-9, tissue inhibitor of matrix metalloproteinase (TIMP)-1, TIMP-2 and C-terminal propeptide of collagen type-I with incident AF were examined after adjusting for confounders.

Results

In models adjusted for age, sex and race, all biomarkers were associated with AF, but only the relationship between plasma MMP-9 remained significant in the fully-adjusted model: each one standard deviation increase in MMP-9 was associated with 27% (95% Confidence Interval: 7% to 50%) increase in risk of AF with no evidence of an interaction with race or sex. Individuals with above mean levels of MMP-9 were more likely to be male, white and current smokers.

Conclusions

The findings suggest that elevated levels of MMP-9 are independently associated with increased risk of AF. However, given the lack of specificity of MMP-9 to atrial tissue, it remains to be determined whether the observed relationship reflects the impact of atrial fibrosis or more generalized fibrosis on risk of incident AF.

Biological effects of static electric field: Plasma/serum proteome analysis of rats

The external static electric field (SEF) of man-made origin brings to the substantially increased SEF background in a human environment the biological activity of which is a moot question. The paper reports on rats blood plasma/serum proteome modifications by means of 1D polyacrilamide gel electrophoresis and clotting process alterations after the short- and long-term SEF exposures of 200 kV/m. The results indicate decrease of fast α1 and α2 globular proteins in plasma coinciding with clotting acceleration after the short-term SEF, and attenuation of clotting-dependent proteome modifications reflected with incomplete coagulation after the long-term SEF exposure. Increased lysozyme activity in serum unlike plasma was observed after both SEF exposures. Applied model of the high-voltage SEF environment indicates dependence of biological systems functioning on the external SEF.

Concentration kinetics of serum MMP-9 and TIMP-1 after blunt multiple injuries in the early posttraumatic period

Metalloproteinases are secreted in response to a variety of inflammatory mediators and inhibited by tissue inhibitors of matrixmetalloproteinases (TIMPs). Two members of these families, MMP-9 and TIMP-1, were differentially expressed depending on clinical parameters in a previous genomewide mRNA analysis. The aim of this paper was now to evaluate the posttraumatic serum levels and the time course of both proteins depending on distinct clinical parameters. 60 multiple traumatized patients (ISS > 16) were included. Blood samples were drawn on admission and 6 h, 12 h, 24 h, 48 h, and 72 h after trauma. Serum levels were quantified by ELISA. MMP-9 levels significantly decreased in the early posttraumatic period (P < 0.05) whereas TIMP-1 levels significantly increased in all patients (P < 0.05). MMP-9 and TIMP-1 serum concentration kinetics became manifest in an inversely proportional balance. Furthermore, MMP-9 presented a stronger decrease in patients with severe trauma and non-survivors in contrast to minor traumatized patients (ISS ≤ 33) and survivors, initially after trauma.