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

Seasonal variation and stability of matrix metalloproteinase-9 activity and tissue inhibitor of matrix metalloproteinase-1 with storage at -80°C

OBJECTIVE

To determine whether active matrix metalloproteinase (MMP)-9 and tissue inhibitor of matrix metalloproteinase (TIMP)-1 displayed seasonal variation and were stable in storage.

METHODS

Plasma active MMP-9 and TIMP-1 were measured at three time-points in 163 individuals.

RESULT

There was no evidence for seasonal variation or declining levels for up to three years of storage at -80°C.

CONCLUSION

Active MMP-9 and TIMP-1 appear to be stable seasonally, and in storage for at least three years.

Differences between human plasma and serum metabolite profiles

BACKGROUND

Human plasma and serum are widely used matrices in clinical and biological studies. However, different collecting procedures and the coagulation cascade influence concentrations of both proteins and metabolites in these matrices. The effects on metabolite concentration profiles have not been fully characterized.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed the concentrations of 163 metabolites in plasma and serum samples collected simultaneously from 377 fasting individuals. To ensure data quality, 41 metabolites with low measurement stability were excluded from further analysis. In addition, plasma and corresponding serum samples from 83 individuals were re-measured in the same plates and mean correlation coefficients (r) of all metabolites between the duplicates were 0.83 and 0.80 in plasma and serum, respectively, indicating significantly better stability of plasma compared to serum (p = 0.01). Metabolite profiles from plasma and serum were clearly distinct with 104 metabolites showing significantly higher concentrations in serum. In particular, 9 metabolites showed relative concentration differences larger than 20%. Despite differences in absolute concentration between the two matrices, for most metabolites the overall correlation was high (mean r = 0.81±0.10), which reflects a proportional change in concentration. Furthermore, when two groups of individuals with different phenotypes were compared with each other using both matrices, more metabolites with significantly different concentrations could be identified in serum than in plasma. For example, when 51 type 2 diabetes (T2D) patients were compared with 326 non-T2D individuals, 15 more significantly different metabolites were found in serum, in addition to the 25 common to both matrices.

CONCLUSIONS/SIGNIFICANCE

Our study shows that reproducibility was good in both plasma and serum, and better in plasma. Furthermore, as long as the same blood preparation procedure is used, either matrix should generate similar results in clinical and biological studies. The higher metabolite concentrations in serum, however, make it possible to provide more sensitive results in biomarker detection.

Matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) in preoperative serum as independent prognostic markers in patients with colorectal cancer

Colorectal cancer is one of the leading causes of cancer related death in developed countries. One of the reasons is the absence of tumor specific diagnostic and prognostic markers. The aim of this study was to examine the correlation of matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) expressions in serum and clinicopathological features of the colorectal adenocarcinoma. Another aim was to examine expression of MMP-9 in the tissue of the colorectal carcinoma in MMP-9 serum positive patients. In addition, we tried to establish the correlation between preoperative levels of serum markers (CEA and CA 19-9) and presence of MMP-2 or MMP-9. The study was performed on 32 patients with colorectal adenocarcinoma who underwent surgery and 11 patients in a control group who were operated for benign diseases. The samples were analyzed by SDS-PAGE to determine the molecular mass and SDS-PAGE zymography to determine levels of MMP-2 and MMP-9. Expression of MMP-9 was determined immunohistochemically in the tissue of the colorectal carcinoma of MMP-9 serum positive patients. MMP-2 and MMP-9 levels were increased in the serum of the patients with colorectal cancer compared to the control group. There was significant correlation in MMPs levels among the patients with tumor stage I and II and the patients with tumor stage III and IV. Obtained results did not demonstrate correlation between levels of CEA, CA 19-9 and presence of MMP-2 or MMP-9. MMP-9 expression was positive in 85% of MMP-9 serum positive patients with colorectal carcinoma. The overexpression of MMP-2 and MMP-9 strongly suggests its association with colorectal adenocarcinoma. Detection of MMP-2 and MMP-9 in serum might be useful for identification of patients with higher risk for colorectal cancer recurrence.

Increased levels of leukocyte-derived MMP-9 in patients with stable angina pectoris

Objective

There is a growing interest for matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in plasma as novel biomarkers in coronary artery disease (CAD). We aimed to identify the sources of MMP-8, MMP-9, TIMP-1 and TIMP-2 among peripheral blood cells and further explore whether gene expression or protein release was altered in patients with stable angina pectoris (SA).

Methods

In total, plasma MMP-9 was measured in 44 SA patients and 47 healthy controls. From 10 patients and 10 controls, peripheral blood mononuclear cells (PBMC) and neutrophils were isolated and stimulated ex vivo. MMPs, TIMPs and myeloperoxidase were measured in plasma and supernatants by ELISA. The corresponding gene expression was measured by real-time PCR.

Results

Neutrophils were the dominant source of MMP-8 and MMP-9. Upon moderate stimulation with IL-8, the neutrophil release of MMP-9 was higher in the SA patients compared with controls (p<0.05). In PBMC, the TIMP-1 and MMP-9 mRNA expression was higher in SA patients compared with controls, p<0.01 and 0.05, respectively. There were no differences in plasma levels between patients and controls except for TIMP-2, which was lower in patients, p<0.01.

Conclusion

Measurements of MMPs and TIMPs in plasma may be of limited use. Despite similar plasma levels in SA patients and controls, the leukocyte-derived MMP-9 and TIMP-1 are significantly altered in patients. The findings indicate that the leukocytes are more prone to release and produce MMP-9 in symptomatic and angiographically verified CAD—a phenomenon that may have clinical implications in the course of disease.

Matrix metalloproteinase-9 predicts pulmonary status declines in α1-antitrypsin deficiency

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) may be important in the progression of emphysema, but there have been few longitudinal clinical studies of MMP-9 including pulmonary status and COPD exacerbation outcomes.

METHODS

We utilized data from the placebo arm (n=126) of a clinical trial of patients with alpha1-antitrypsin deficiency (AATD) and emphysema to examine the links between plasma MMP-9 levels, pulmonary status, and COPD exacerbations over a one year observation period. Pulmonary function, computed tomography lung density, incremental shuttle walk test (ISWT), and COPD exacerbations were assessed at regular intervals over 12 months. Prospective analyses used generalized estimating equations to incorporate repeated longitudinal measurements of MMP-9 and all endpoints, controlling for age, gender, race-ethnicity, leukocyte count, and tobacco history. A secondary analysis also incorporated highly-sensitive C-reactive protein levels in predictive models.

RESULTS

At baseline, higher plasma MMP-9 levels were cross-sectionally associated with lower FEV1 (p=0.03), FVC (p<0.001), carbon monoxide transfer factor (p=0.03), resting oxygen saturation (p=0.02), and ISWT distance walked (p=0.02) but were not associated with radiographic lung density or total lung capacity (TLC). In longitudinal analyses, MMP-9 predicted a further decline in transfer factor (p=0.04) and oxygen saturation (p<0.001). MMP-9 also predicted worsening lung density (p=0.003), increasing TLC (p=0.02), and more frequent COPD exacerbations over follow-up (p=0.003). Controlling additionally for hs-CRP levels did not substantively change the longitudinal associations between MMP-9 and these outcomes.

CONCLUSIONS

Increased plasma MMP-9 levels generally predicted pulmonary status declines, including worsening transfer factor and lung density as well as greater COPD exacerbations in AATD-associated emphysema.

Whole blood assay for elastase, chymotrypsin, matrix metalloproteinase-2, and matrix metalloproteinase-9 activity

The ability to measure protease activity in the blood is important for the development of future diagnostics and for biomedical research. Presently, protease assays require sample preparation, making them time-consuming, costly, less accurate, and unsuitable for point-of-care (POC) diagnostics. Recently, we demonstrated a unique method for measuring clinically relevant levels of trypsin activity in only a few microliters of whole blood. This assay utilizes a charge-changing fluorescent peptide substrate that produces a positively charged fluorescent product fragment upon cleavage by the target protease. Using a simple electrophoretic format, the fragments could be rapidly separated, concentrated, and detected directly from a whole blood sample. We now report on the development of new protease substrates for the measurement of elastase, chymotrypsin, matrix metalloproteinase (MMP)-2, and MMP-9 activity in whole blood. In these studies, detection limits ranging from 1 to 40 pg in 6 μL of 1× phosphate-buffered saline (PBS) (0.2-6 ng/mL) were achieved after a only 1 h reaction of enzyme and substrate. In subsequent experiments measuring spiked protease in whole blood (with endogenous protease present), detection limits ranging from 100 to 200 ng/mL were achieved after a 1 h reaction. Thus, these new substrates demonstrate broad applicability toward clinically relevant detection of important disease-relevant proteases.

A phase II trial of bevacizumab with dacarbazine and daily low-dose interferon-alpha2a as first line treatment in metastatic melanoma

Metastatic melanomas are hypervascular tumours with poor prognosis. We hypothesized that treatment of metastatic melanoma with a combination of bevacizumab, a monoclonal antibody against vascular endothelial growth factor, dacarbazine (DTIC) and low-dose interferon alpha-2a (IFN-alpha2a) might lead to a synergistic inhibition of angiogenesis and regression of tumours. Patients with metastatic melanoma were treated with bevacizumab (5 mg/kg every 2 weeks), DTIC (200 mg/m days 1-5 every 4 weeks) and IFN-alpha2a (three MIU subcutaneously daily from day 15 onwards). Patients exhibiting response or stable disease after 6 months were treated with bevacizumab+/-IFN-alpha2a until disease progression. The primary study objectives were progression-free survival (PFS), overall survival and safety. Twenty-six patients were accrued. Response rate was 23% (two complete responses, four partial responses), and six patients showed stable disease. The median PFS for all patients was 2.3 months and for responders 8.1 months. The median overall survival for all patients was 11.5 months. Four life-threatening adverse events were seen: two pulmonary thromboembolisms, an intracerebral haemorrhage, and one grade 4 hypertension. One of the pulmonary emboli and the intracerebral haemorrhage were observed > or =3 months after the last bevacizumab-DTIC dose. Serum matrix metalloproteinase-9 and vascular endothelial growth factor levels changed during therapy. There was a trend towards favourable PFS among patients with only minimal or moderate change in these marker expression levels. The present regimen was active in this patient group but was also associated with remarkable vascular events.

Metalloproteinases and their inhibitors-diagnostic and therapeutic opportunities in orthopedics

Matrix metalloproteinases (MMPs) and related enzymes (ADAMs, ADAMTS) and their inhibitors control matrix turnover and function. Recent advances in our understanding of musculoskeletal conditions such as tendinopathy, arthritis, Dupuytren's disease, degenerative disc disease, and bone and soft tissue healing suggest that MMPs have prominant roles. Importantly, MMPs are amenable to inhibition by cheap, safe, and widely available drugs such as the tetracycline antibiotics and the bisphosphonates. This indicates that these MMP inhibitors, if proven effective for any novel indication, may be quickly brought into clinical practice.

Translating molecular medicine into clinical tools: doomed to fail by neglecting basic preanalytical principles

This commentary discusses a study on measurements of matrix metalloproteinase 9 (MMP-9) in serum of pseudoxanthoma elasticum patients recently published in Journal of Molecular Medicine. This study can be considered the typical "obstacle" to effective translational medicine as previously documented in JTM journal. Although serum has been frequently proven as inappropriate sample for determining numerous circulating MMPs, among them MMP-9, there are over and over again studies, as in this case, that measure MMP-9 in serum. Comparative measurements in serum and plasma samples demonstrated higher concentrations for MMP-9 in serum due to the additional release from leukocytes and platelets following the coagulation/fibrinolysis process. From this example it can be concluded that translating basic research discoveries into clinical tools needs a more intensive exchange between basic biomedical research and clinical scientists already in an early stage. Otherwise a lost of translation, as discussed in JTM journal, seems to be inevitable.

Impact of blood collection devices on clinical chemistry assays

Blood collection devices interact with blood to alter blood composition, serum, or plasma fractions and in some cases adversely affect laboratory tests. Vascular access devices may release coating substances and exert shear forces that lyse cells. Blood-dissolving tube additives can affect blood constituent stability and analytical systems. Blood tube stoppers, stopper lubricants, tube walls, surfactants, clot activators, and separator gels may add materials, adsorb blood components, or interact with protein and cellular components. Thus, collection devices can be a major source of preanalytical error in laboratory testing. Device manufacturers, laboratory test vendors, and clinical laboratory personnel must understand these interactions as potential sources of error during preanalytical laboratory testing. Although the effects of endogenous blood substances have received attention, the effects of exogenous substances on assay results have not been well described. This review will identify sources of exogenous substances in blood specimens and propose methods to minimize their impact on clinical chemistry assays.

Matrix Metalloproteinase-9 (MMP9)-A Mediating Enzyme in Cardiovascular Disease, Cancer, and Neuropsychiatric Disorders

Matrix metalloproteinase-9 (MMP9) has been implicated in numerous somatic illnesses, including cardiovascular disorders and cancer. Recently, MMP9 has been shown to be increasingly important in several aspects of central nervous system activity. Furthermore, a pathogenic role for this enzyme has been suggested in such neuropsychiatric disorders as schizophrenia, bipolar illness, and multiple sclerosis. In this paper, the results of biochemical and molecular-genetic studies on MMP9 that have been performed in these pathological conditions will be summarized. Furthermore, I hypothesize that the MMP9 gene, as shown by functional −1562 C/T polymorphism studies, may be mediating the relationship of neuropsychiatric illnesses (schizophrenia, bipolar mood disorder, multiple sclerosis) that are comorbid with cardiovascular disease and cancer.

Cardiovascular therapeutic uses of targeted ultrasound contrast agents

The therapeutic use of ultrasound contrast agents (UCAs) is an emerging methodology with high potential for enhanced directed therapeutic gene, bioactive gas, drug, and stem cell delivery. Ultrasound-targeted microbubble destruction has already demonstrated feasibility for plasmid DNA delivery. Similarly, therapeutic ultrasound for thrombolysis treatment has been taken into the clinical setting, and the addition of UCAs for therapeutic delivery or enhanced effect through cavitation is a natural progression to this investigation. However, as with any new technique, safety needs to be first demonstrated before translation into clinical practice. This review article will focus on the development of UCAs for cardiac and vascular therapeutics as well as the limitations/concerns for the use of therapeutic ultrasound in clinical medicine in order to lay a foundation for investigators planning to enter this exciting field or for those who want to broaden their understanding.

In vivo characterization of activatable cell penetrating peptides for targeting protease activity in cancer

Activatable cell penetrating peptides (ACPPs) are novel in vivo targeting agents comprised of a polycationic cell penetrating peptide (CPP) connected via a cleavable linker to a neutralizing polyanion (). Adsorption and uptake into cells are inhibited until the linker is proteolyzed. An ACPP cleavable by matrix metalloproteinase-2 (MMP-2) in vitro was the first one demonstrated to work in a tumor model in vivo, but only HT-1080 xenografts and resected human squamous cell carcinomas were tested. Generality to other cancer types, in vivo selectivity of ACPPs for MMPs, and spatial resolution require further characterization. We now show that ACPPs can target many xenograft tumor models from different cancer sites, as well as a thoroughly studied transgenic model of spontaneous breast cancer (mouse mammary tumor virus promoter driving polyoma middle T antigen, MMTV-PyMT). Pharmacological inhibitors and genetic knockouts indicate that current ACPPs are selective for MMP-2 and MMP-9 in the above in vivo models. In accord with the known local distribution of MMP activity, accumulation is strongest at the tumor-stromal interface in primary tumors and associated metastases, indicating better spatial resolution (<50 mum) than other currently available MMP-cleavable probes. We also find that background uptake of ACPPs into normal tissues such as cartilage can be decreased by appending inert macromolecules of 30-50 KDa to the polyanionic inhibitory domain. Our results validate an approach that should generally deliver imaging agents and chemotherapeutics to sites of invasion, tumor-promoting inflammation, and metastasis.

Heparin affects matrix metalloproteinases and tissue inhibitors of metalloproteinases circulating in peripheral blood

OBJECTIVES

Blood sampling/handling alters matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) expression. The aim of this study is to evaluate the effects of high molecular weight heparin on MMP and TIMP expression in blood.

DESIGN AND METHODS

We analyzed by gelatin zymography and ELISA assays the effects of different heparin salts, dose- and time-dependence of MMP and TIMP concentrations in plasma and sera collected with and without clot-accelerator in plastic tubes from 50 healthy donors.

RESULTS

The levels and zymography of MMP-2 did not show significant changes among all samples, and during time- and dose-dependent heparin treatments. MMP-9 and TIMP-2 expression were strongly affected by heparin, with significant increase of their content and gelatinolytic activity both in time- and in dose-dependent fashion. Addition of heparin allowed also the displacement of MMP-2 prodomain, favouring zymogen activation.

CONCLUSIONS

Heparin has direct and indirect effects, altering MMP/TIMP complexes circulating in blood, and increasing the release of TIMP-2. To avoid misinterpretations due to MMP/TIMP complex alteration and MMP prodomain displacement, heparin should be cautiously used in blood collection procedures.