Molecular probes for selective detection of cysteine cathepsins

Cysteine cathepsins are proteases critical in physiopathological processes and show potential as targets or biomarkers for diseases and medical conditions. The 11 members of the cathepsin family are redundant in some cases but remarkably independent of others, demanding the development of both pan-cathepsin targeting tools as well as probes that are selective for specific cathepsins with little off-target activity. This review addresses the diverse design strategies that have been employed to accomplish this tailored selectivity among cysteine cathepsin targets and the imaging modalities incorporated. The power of these diverse tools is contextualized by briefly highlighting the nature of a few prominent cysteine cathepsins, their involvement in select diseases, and the application of cathepsin imaging probes in research spanning basic biochemical studies to clinical applications.

Laser capture microdissection in combination with mass spectrometry: Approach to characterization of tissue-specific proteomes of Eudiplozoon nipponicum (Monogenea, Polyopisthocotylea)

Eudiplozoon nipponicum (Goto, 1891) is a hematophagous monogenean ectoparasite which inhabits the gills of the common carp (Cyprinus carpio). Heavy infestation can lead to anemia and in conjunction with secondary bacterial infections cause poor health and eventual death of the host. This study is based on an innovative approach to protein localization which has never been used in parasitology before. Using laser capture microdissection, we dissected particular areas of the parasite body without contaminating the samples by surrounding tissue and in combination with analysis by mass spectrometry obtained tissue-specific proteomes of tegument, intestine, and parenchyma of our model organism, E. nipponicum. We successfully verified the presence of certain functional proteins (e.g. cathepsin L) in tissues where their presence was expected (intestine) and confirmed that there were no traces of these proteins in other tissues (tegument and parenchyma). Additionally, we identified a total of 2,059 proteins, including 72 peptidases and 33 peptidase inhibitors. As expected, the greatest variety was found in the intestine and the lowest variety in the parenchyma. Our results are significant on two levels. Firstly, we demonstrated that one can localize all proteins in one analysis and without using laboratory animals (antibodies for immunolocalization of single proteins). Secondly, this study offers the first complex proteomic data on not only the E. nipponicum but within the whole class of Monogenea, which was from this point of view until recently neglected.

Skeletal Muscle Lysosomal Function via Cathepsin Activity Measurement

Muscle wasting or cachexia is commonly associated with aging and many diseases such as cancer, infection, autoimmune disorders, and trauma. Decrease in muscle mass, or muscle atrophy, is often caused by dysfunction of protein proteolytic systems, such as lysosomes, which regulate protein turnover and homeostasis. Lysosomes contain many hydrolases and proteases and, thus, represent the major organelle that control protein turnover. Recently, lysosomes have emerged as a signaling hub to integrate cellular functions of nutrient sensing and metabolism, autophagy, phagocytosis, and endocytosis, which are all related to tissue homeostasis. In this chapter, we describe the protocol used to measure lysosomal proteinase (cathepsins) activity in the skeletal muscle. A better understanding of lysosomal function in muscle homeostasis is critical in developing new therapeutic approaches to prevent muscle wasting.

Biomarkers of alveolar bone resorption in gingival crevicular fluid: A systematic review

BACKGROUND

Periodontitis is a prevalent oral disease with bone loss being it's hallmark. Clinical parameters used to measure periodontitis are retrospective and do not indicate active inflammation nor prognosis. GCF can be easily collected chairside and bone turnover biomarkers found in GCF can be evaluated to check for active inflammation and disease progression. This systematic review aims to evaluate the literature for association and predictive value of bone turnover biomarkers in GCF during periodontal disease.

MATERIALS AND METHODS

This review was conducted and reported according to the PRISMA guidelines. The online databases Google Scholar and PubMed were used for data search. MeSH terms were used for PubMed search. All original studies from 1990 to 2017 conducted on human subjects in the English language were included in the review. Studies on non-human subjects, reviews and studies conducted in languages other than English were not considered. Reference lists of qualified articles were also searched.

RESULTS

The search generated 2300 results whose titles were screened and 1571 articles were retreived. 23 articles were accepted in the review and full texts were accessed. These included 1 randomized controlled trial, 12 cross-sectional studies, five pre-post interventional studies, 4 longitudinal and 1 in-vitro in-vivo experimental study. The studies were conducted on patients of both genders ranging from 10 to 81 years in age. A total of 37 biomarkers were evalueted in the studies included in this review. Majority of the studies reported interleukin-1β (IL-1β) while receptor activated nuclear factor-kappa B ligand (RANKL) and matrix metalloproteinase-8 (MMP-8) were the other frequently reported biomarkers. Most of the studies evaluated more than two biomarkers. ELISA was the most commonly used biochemical test used for detection.

CONCLUSION

A wide range of biomarkers have been established as indicators of alveolar bone resorption. Few of the biomarkers have also shown positive correlation with disease progression and outcome of periodontal therapies thus underscoring their predictive value in periodontal diagnosis and prognosis. Not one single biomarker has been reported to have a predictive advantage over another and a combination of two or more biomarkers along with clinical evaluation is recommended.

Long-Term Follow-Up Confirms Prognostic Impact of Pai-1 and Cathepsin D and L in Primary Breast Cancer

After long-term follow-up, the prognostic impact of the following proteolytic factors associated with tumor invasion and metastasis was evaluated in 276 primary breast cancer patients: uPA (urokinase-type plasminogen activator), PAI-1 (uPA inhibitor type 1), and cathepsins B, D and L. The median follow-up of patients still alive at the time of analysis was 109 months. To date 119 patients (43%) have relapsed and 117 (42%) have died. Antigen levels of uPA and PAI-1 were determined by ELISA in detergent extracts; cathepsin B, D, and L content was determined in cytosol fractions of the primary tumor: cathepsin D by ELSA and cathepsin B and L by ELISA.

In multivariate analysis (Cox model) for disease-free survival (DFS), lymph node status (p<0.001; RR=3.8), cathepsin L (p<0.001; RR=2.6) and PAI-1 (p=0.027; RR=1.7) were significant factors in all patients. In addition to these factors, grading was significant for overall survival (OS). In another multivariate approach, CART (Classification And Regression Trees) analysis, lymph node status (p<0.001) turned out to be the strongest discriminator for patients at high risk of relapse. In the node-negative patient subset, PAI-1 was the strongest risk group discriminator (p<0.001): in this subset, patients with low levels of both PAI-1 and cathepsin D had a very low relapse rate of only 3.2% compared to 39% in the remaining node-negative patients. In node-positive patients cathepsin L gave the best risk group assessment (p=0.001).

In conclusion, tumor-associated PAI-1 and cathepsins D and L provide significant, statistically independent prognostic information for DFS and OS in primary breast cancer, even after a median follow-up period of almost 10 years.

Cysteine Proteinases and Their Inhibitors in Extracellular Fluids: Markers for Diagnosis and Prognosis in Cancer

Cathepsins B, H and L have been shown to participate in processes of tumor growth, vascularization, invasion and metastasis. Their levels in tumor tissue extracts can provide useful clinical information to predict disease-free and overall survival in breast, lung, colorectal, brain and head and neck cancer patients. Recently we have found that both cysteine cathepsins and their endogenous protein inhibitors stefins and cystatin C can also predict prognosis when measured extracellularly. In melanoma and colorectal cancer patients high serum levels of cathepsins B and H correlated with shorter survival. Similarly, increased extracellular levels of stefins A and B and cystatin C correlated significantly with high risk of adverse outcome in cancer patients. However, the cathepsin B/cystatin C complex was found to be less abundant in sera of patients with malignant tumors than in those with benign diseases or in healthy controls, suggesting an imbalance between the enzyme and its inhibitor in cancer patients.

Effect of technological factors on the activity and losses of cathepsins B, D and L during the marinating of Atlantic and Baltic herrings

BACKGROUND

This study analyzes the effect of salt and acetic acid concentration, time, temperature and fish freezing on the activity and losses of cathepsins during the marinating of Atlantic and Baltic herrings.

RESULTS

The highest contribution to meat general proteolytic activity was found for cathepsin D-like activity. This contribution decreased during the marinating process as a result of, among other things, cathepsin losses to brine. The methods of marinating had a significant impact on cathepsin activity losses. The average ratio of cathepsin D-like activity to L and B in brine accounted for 15:3.5:1.5, respectively. Depending on the method of calculation, cathepsin activity in brine was similar (per gram of tissue/milliliter of brine) or multiply higher (per gram protein in tissue/brine) than in the marinated herring meat. Statistical analysis demonstrated that the extent and structure of cathepsin losses were significantly correlated with the quantitative and qualitative composition of protein hydrolysis products in marinades.

CONCLUSION

The presented results depict new phenomena of cathepsin losses and explain their impact on the process of fish marinating. Results allow better optimization of the process of meat ripening. The high activity of aspartyl and cysteine cathepsins in brine indicates the real feasibility of their application in the food industry for novel food design. © 2016 Society of Chemical Industry.

Cysteine Protease Zymography: Brief Review

Cysteine proteases play multiple roles in basically all aspects of physiology and development. In plants, they are involved in growth and development and in accumulation and mobilization of storage proteins. Furthermore, they are engaged in signalling pathways and in the response to biotic and abiotic stresses. In animals and also in humans, they are responsible for senescence and apoptosis, prohormone processing, and ECM remodelling. When analyzed by zymography, the enzyme must be renaturated after SDS-PAGE. SDS must be washed out and substituted by Triton X-100. Gels are then further incubated under ideal conditions for activity detection. Cysteine proteases require an acidic pH (5.0-6.0) and a reducing agent, usually DTT. When screening biological samples, there is generally no previous clue on what peptidase class will be present, neither optimal proteolysis conditions are known. Hence, it is necessary to assess several parameters, such as incubation time, pH, temperature, influence of ions or reducing agents, and finally evaluate the inhibition profile. For detection of cysteine peptidase activity, the use of specific inhibitors, such as E-64, can be used to prevent the development of cysteine peptidase activity bands and positively confirm its presence. Here four different protocols to assess cysteine protease activity from different sources are presented.

Measuring Cysteine Cathepsin Activity to Detect Lysosomal Membrane Permeabilization

During lysosomal membrane permeabilization (LMP), lysosomal lumenal contents can be released into the cytosol. Small molecules are more likely to be released, and cysteine cathepsins, with mature forms possessing a mass of 25-30 kDa, are among the smallest lumenal lysosomal enzymes. In addition, specific substrates for cysteine cathepsins are available to investigators, and therefore the measurement of the cathepsin activity as a hallmark of LMP works well. Here, we present a protocol for measuring the activity of these enzymes after selective plasma membrane permeabilization with a low concentration of digitonin and after total cell membrane lysis with a high concentration of digitonin. A fluorogenic substrate can be added either directly to the well with lysed cells to show LMP or to the cell-free extract to show that the lysosomal membrane has been sufficiently destabilized to allow the translocation of lysosomal enzymes. Although the content of lysosomal cysteine cathepsins differs between cell lines, this method has general applicability, is sensitive, and has high throughput. The presented protocol shows how to measure cysteine cathepsin activity in the presence of lysed cells and also in cell-free extracts. Depending on the aim of the study, one or both types of measurements can be performed.

[IFN-γ stimulates the release of cathepsin S in mouse mast cells]

OBJECTIVE

To investigate the impact of interferon γ (IFN-γ) on cathepsin S (CTSS) expressed by P815 mouse mast cells and mouse bone marrow-derived mast cells (BMMCs).

METHODS

IFN-γ of 10, 25 and 50 ng/mL were respectively used to stimulate P815 cells and mouse BMMCs. Real-time PCR and ELISA were applied to detect mRNA and protein levels of CTSS in P815 cells and BMMCs. 25 ng/mL IFN-γ was used to treat P815 cells for 6, 12, 18, 24, 48 and 72 hours and mouse BMMCs for 12, 24 and 48 hours; the above mentioned detection steps were then repeated.

RESULTS

IFN-γ induced P815 cells and BMMCs to express CTSS on the mRNA and protein levels in the time- and dose-dependent manners.

CONCLUSION

IFN-γ could stimulate mast cells to release CTSS.

Neuropeptidomics Mass Spectrometry Reveals Signaling Networks Generated by Distinct Protease Pathways in Human Systems

Neuropeptides regulate intercellular signaling as neurotransmitters of the central and peripheral nervous systems, and as peptide hormones in the endocrine system. Diverse neuropeptides of distinct primary sequences of various lengths, often with post-translational modifications, coordinate and integrate regulation of physiological functions. Mass spectrometry-based analysis of the diverse neuropeptide structures in neuropeptidomics research is necessary to define the full complement of neuropeptide signaling molecules. Human neuropeptidomics has notable importance in defining normal and dysfunctional neuropeptide signaling in human health and disease. Neuropeptidomics has great potential for expansion in translational research opportunities for defining neuropeptide mechanisms of human diseases, providing novel neuropeptide drug targets for drug discovery, and monitoring neuropeptides as biomarkers of drug responses. In consideration of the high impact of human neuropeptidomics for health, an observed gap in this discipline is the few published articles in human neuropeptidomics compared with, for example, human proteomics and related mass spectrometry disciplines. Focus on human neuropeptidomics will advance new knowledge of the complex neuropeptide signaling networks participating in the fine control of neuroendocrine systems. This commentary review article discusses several human neuropeptidomics accomplishments that illustrate the rapidly expanding diversity of neuropeptides generated by protease processing of pro-neuropeptide precursors occurring within the secretory vesicle proteome. Of particular interest is the finding that human-specific cathepsin V participates in producing enkephalin and likely other neuropeptides, indicating unique proteolytic mechanisms for generating human neuropeptides. The field of human neuropeptidomics has great promise to solve new mechanisms in disease conditions, leading to new drug targets and therapeutic agents for human diseases. Graphical Abstract ᅟ.

Changes of Proteases, Antiproteases, and Pathogens in Cystic Fibrosis Patients' Upper and Lower Airways after IV-Antibiotic Therapy

BACKGROUND

In cystic fibrosis (CF) the upper (UAW) and lower airways (LAW) are reservoirs for pathogens like Pseudomonas aeruginosa. The consecutive hosts' release of proteolytic enzymes contributes to inflammation and progressive pulmonary destruction. Objectives were to assess dynamics of protease : antiprotease ratios and pathogens in CF-UAW and LAW sampled by nasal lavage (NL) and sputum before and after intravenous- (IV-) antibiotic therapy.

METHODS

From 19 IV-antibiotic courses of 17 CF patients NL (10 mL/nostril) and sputum were collected before and after treatment. Microbiological colonization and concentrations of NE/SLPI/CTSS (ELISA) and MMP-9/TIMP-1 (multiplex bead array) were determined. Additionally, changes of sinonasal symptoms were assessed (SNOT-20).

RESULTS

IV-antibiotic treatment had more pronounced effects on inflammatory markers in LAW, whereas trends to decrease were also found in UAW. Ratios of MMP-9/TIMP-1 were higher in sputum, and ratios of NE/SLPI were higher in NL. Remarkably, NE/SLPI ratio was 10-fold higher in NL compared to healthy controls. SNOT-20 scores decreased significantly during therapy (P = 0.001).

CONCLUSION

For the first time, changes in microbiological patterns in UAW and LAW after IV-antibiotic treatments were assessed, together with changes of protease/antiprotease imbalances. Delayed responses of proteases and antiproteases to IV-antibiotic therapy were found in UAW compared to LAW.

Two-month follow-up of the changes in vitreal constituents after argon laser coagulation of the retina in rabbits

The response of the vitreous after panretinal argon laser photocoagulation was followed over a period of 60 days. Two phases can be discerned. An an immediate reaction to the disturbance of the blood-retinal barrier at the site of the pigment epithelium the total protein content and malate dehydrogenase activity rise sharply within 3 days, 4- to 5-fold above a normal. The more protracted increase of lysosomal enzyme activities which reach their peak heigh after 14 days only, can be attributed to the action and proliferation of phagocytic cells. 2 months after treatment all parameters have returned to their normal levels.

Effects of acid etching and adhesive treatments on host-derived cysteine cathepsin activity in dentin

PURPOSE

To analyze the effects of different processes during bonding on endogenous cysteine cathepsin activity in dentin.

MATERIALS AND METHODS

Dentin powder, prepared from extracted human third molars, was divided into 10 groups. Two lots of dentin powder were used to detect the effects of the procedure of protein extraction on endogenous cathepsin activity. The others were used to study effects of different acid-etching or adhesive treatments on enzyme activity. Concentrations of 37% phosphoric acid or 10% phosphoric acid, two etch-and-rinse adhesive systems, and two self-etching adhesive systems were used as dentin powder treatments. The untreated mineralized dentin powder was set as the control. After treatment, the proteins of each group were extracted. The total cathepsin activity in the extracts of each group was monitored with a fluorescence reader.

RESULTS

In the control group, there were no significant differences in cathepsin activity between the protein extract before EDTA treatment and the protein extract after EDTA treatment (p > 0.05). The cathepsin activities of the three different extracts in the 37% phosphoric acid-treated group were different from each other (p < 0.05). The two acid-etching groups and two etch-and-rinse groups showed significant enzyme activity reduction vs the control group (p < 0.05). There were no significant differences between those four groups (p > 0.05). Treating the dentin powder with any of the two self-etching adhesives resulted in an increase in cathepsin activity (p < 0.05).

CONCLUSIONS

The activity of cysteine cathepsins can be detected in dentin powder. Treatment with EDTA during protein extraction exerted an influence on cathepsin activity. Acid etching or etch-and-rinse adhesive systems may reduce the activity of endogenous cathepsins in dentin. Self-etching adhesive systems may increase the enzyme activity.

In vivo molecular imaging of cathepsin and matrix metalloproteinase activity discriminates between arthritic and osteoarthritic processes in mice

Rheumatoid arthritis (RA) and osteoarthritis (OA) are serologically and clinically distinctive, but at the local level, both diseases have many molecular pathways in common. In vivo molecular imaging can unravel the local pathologic processes involved in both diseases. In this study, we investigated matrix metalloproteinase (MMP) and cathepsin activity during cartilage destruction, in an RA and an OA mouse model, using biophotonic imaging of substrate-based probes. Mice with collagen-induced arthritis (CIA) or destabilization of the medial meniscus (DMM) were imaged using near-infrared fluorescent probes, activated by several cathepsins or MMPs. Fluorescence signal intensity was compared to synovial gene expression, histology, and cartilage staining of a neoepitope of aggrecan cleaved by MMPs with the amino acids DIPEN. Increased cathepsin and MMP activity was seen during CIA, whereas the DMM model only showed increased MMP activity. DIPEN expression was seen only during CIA. A possible explanation can be differences in gene expressions; MMP3 and -13, known to produce DIPEN neoepitopes, were upregulated in the CIA model, whereas MMP12, known to be involved in elastin degradation and chemokine inhibition, was upregulated in the DMM model. Thus, molecular imaging showed no cathepsin activity at the time of cartilage damage in the DMM model, whereas both cathepsins and MMPs are active in the CIA model during disease progression.

Systematic optimization of multiplex zymography protocol to detect active cathepsins K, L, S, and V in healthy and diseased tissue: compromise among limits of detection, reduced time, and resources

Cysteine cathepsins are a family of proteases identified in cancer, atherosclerosis, osteoporosis, arthritis, and a number of other diseases. As this number continues to rise, so does the need for low cost, broad use quantitative assays to detect their activity and can be translated to the clinic in the hospital or in low resource settings. Multiplex cathepsin zymography is one such assay that detects subnanomolar levels of active cathepsins K, L, S, and V in cell or tissue preparations observed as clear bands of proteolytic activity after gelatin substrate SDS-PAGE with conditions optimal for cathepsin renaturing and activity. Densitometric analysis of the zymogram provides quantitative information from this low cost assay. After systematic modifications to optimize cathepsin zymography, we describe reduced electrophoresis time from 2 h to 10 min, incubation assay time from overnight to 4 h, and reduced minimal tissue protein necessary while maintaining sensitive detection limits; an evaluation of the pros and cons of each modification is also included. We further describe image acquisition by Smartphone camera, export to Matlab, and densitometric analysis code to quantify and report cathepsin activity, adding portability and replacing large scale, darkbox imaging equipment that could be cost prohibitive in limited resource settings.

Changes of enzymes activity and protein profiles caused by high-pressure processing in sea bass (Dicentrarchus labrax) fillets

High-pressure processing (HPP) is a technology of growing interest for food preservation, due to its ability to control the activity of degradative enzymes. The effect of three variables (pressure levels of 100, 250, and 400 MPa; pressure holding times of 0, 5, 15, and 30 min; and pressurization rates of 8 and 14 MPa/s) on the activity of the enzymes acid phosphatase, cathepsins (B and D), lipase, and calpains was studied using sea bass fillets as a case study model. Additionally, the effect of HPP on sarcoplasmic proteins was studied by SDS-PAGE and isoelectric focusing electrophoreses. The increase in pressure level and holding time decreased the protein concentration in sarcoplasmic extracts, and also the activity of calpains. As compared to nontreated samples, acid phosphatase activity was lower at 400 MPa, and for cathepsin D lower activities were observed at 100 and 400 MPa. The increase in pressurization rate increased the activity of cathepsin D, lipase, and calpains, although it was not always significant. In contrast, cathepsin B and lipase activities were less affected by HPP treatments. Electrophoresis separation of sarcoplasmic proteins showed that the intensity of many protein bands changed mainly due to pressure level and holding time. The results of this study suggest that HPP causes lysosomes disruption and also denaturation, aggregation, and fragmentation of sarcoplasmic proteins, and this evidence might be related to the decrease in enzymes activity especially at 400 MPa. In conclusion, HPP can be a potential tool to control the activity of degradative enzymes, which might prevent the softening of sea bass muscle due to autolytic reactions.

The peri-islet basement membrane, a barrier to infiltrating leukocytes in type 1 diabetes in mouse and human

We provide the first comprehensive analysis of the extracellular matrix (ECM) composition of peri-islet capsules, composed of the peri-islet basement membrane (BM) and subjacent interstitial matrix (IM), in development of type 1 diabetes in NOD mice and in human type 1 diabetes. Our data demonstrate global loss of peri-islet BM and IM components only at sites of leukocyte infiltration into the islet. Stereological analyses reveal a correlation between incidence of insulitis and the number of islets showing loss of peri-islet BM versus islets with intact BMs, suggesting that leukocyte penetration of the peri-islet BM is a critical step. Protease- and protease inhibitor-specific microarray analyses (CLIP-CHIP) of laser-dissected leukocyte infiltrated and noninfiltrated pancreatic islets and confirmatory quantitative real time PCR and protein analyses identified cathepsin S, W, and C activity at sites of leukocyte penetration of the peri-islet BM in association with a macrophage subpopulation in NOD mice and human type 1 diabetic samples and, hence, potentially a novel therapeutic target specifically acting at the islet penetration stage. Interestingly, the peri-islet BM and underlying IM are reconstituted once inflammation subsides, indicating that the peri-islet BM-producing cells are not lost due to the inflammation, which has important ramifications to islet transplantation studies.

Manipulating substrate and pH in zymography protocols selectively distinguishes cathepsins K, L, S, and V activity in cells and tissues

Cathepsins K, L, S, and V are cysteine proteases that have been implicated in tissue-destructive diseases such as atherosclerosis, tumor metastasis, and osteoporosis. Among these four cathepsins are the most powerful human collagenases and elastases, and they share 60% sequence homology. Proper quantification of mature, active cathepsins has been confounded by inhibitor and reporter substrate cross-reactivity, but is necessary to develop properly dosed therapeutic applications. Here, we detail a method of multiplex cathepsin zymography to detect and distinguish the activity of mature cathepsins K, L, S, and V by exploiting differences in individual cathepsin substrate preferences, pH effects, and electrophoretic mobility under non-reducing conditions. Specific identification of cathepsins K, L, S, and V in one cell/tissue extract was obtained with cathepsin K (37 kDa), V (35 kDa), S (25 kDa), and L (20 kDa) under non-reducing conditions. Cathepsin K activity disappeared and V remained when incubated at pH 4 instead of 6. Application of this antibody free, species independent, and medium-throughput method was demonstrated with primary human monocyte-derived macrophages and osteoclasts, endothelial cells stimulated with inflammatory cytokines, and normal and cancer lung tissues, which identified elevated cathepsin V in lung cancer.

Cystatin A protease inhibitor and cysteine proteases in human cervicovaginal fluid in term pregnancy and labor

OBJECTIVE

The purpose of this study was to investigate the temporal changes in immunoreactive cystatin A and the enzymatic activity of cathepsins B, H, L, and S in human cervicovaginal fluid (CVF) in late pregnancy and spontaneous labor.

STUDY DESIGN

CVF was collected weekly (n = 95 women) from 36 weeks gestation until spontaneous term labor. Cystatin A was quantified using enzyme-linked immunosorbent assay. The enzyme activity of cathepsins B, H, L, and S was measured with fluorometric enzyme assay kits.

RESULTS

Cystatin A significantly decreased towards (P = .016, 2-way analysis of variance) and during labor (P < .001, 2-way analysis of variance). Enzymatic activity of cathepsins B, H, and S did not change with labor onset (P = .452, P = .703, P = .411, respectively, 2-way analysis of variance).

CONCLUSION

In late gestation, CVF-decreased expression of the cysteine protease inhibitor, cystatin A, is associated with labor. Although the role and contribution of cystatin A to increased extracellular matrix remodeling has yet to be elucidated, the data that were obtained are consistent with this hypothesis.