Matrix metalloproteinase (MMP-2, -9) and tissue inhibitor (TIMP-1, -2) activity in tear samples of pediatric type 1 diabetic patients

Shensong yangxin, a multi-functional traditional Chinese medicine for arrhythmia: A review of components, pharmacological mechanisms, and clinical applications

As a common cardiovascular disease (CVD), Arrhythmia refers to any abnormality in the origin, frequency, rhythm, conduction velocity, timing, pathway, sequence, or other aspect of cardiac impulses, and it is one of the common cardiovascular diseases in clinical practice. At present, various ion channel blockers are used for treatment of arrhythmia that include Na+ ion channel blockers, K+ ion channel blockers and Ca2+ ion channel blockers. While these drugs offer benefits, they have led to a gradual increase in drug-related adverse reactions across various systems. As a result, the quest for safe and effective antiarrhythmic drugs is pressing. Recent years have seen some advancements in the treatment of ventricular arrhythmias using traditional Chinese medicine(TCM). The theory of Luobing in TCM has proposed a new drug intervention strategy of "fast and slow treatment, integrated regulation" leading to a shift in mindset from "antiarrhythmic" to "rhythm-regulating". Guided by this theory, the development of Shen Song Yang Xin Capsules (SSYX) has involved various Chinese medicinal ingredients that comprehensively regulate the myocardial electrophysiological mechanism, exerting antiarrhythmic effects on multiple ion channels and non-ion channels. Similarly, in clinical studies, evidence-based research has confirmed that SSYX combined with conventional antiarrhythmic drugs can more effectively reduce the occurrence of arrhythmias. Therefore, this article provides a comprehensive review of the composition and mechanisms of action, pharmacological components, network pharmacology analysis, and clinical applications of SSYX guided by the theory of Luobing, aiming to offer valuable insights for improved clinical management of arrhythmias and related research.

Qili Qiangxin (QLQX) capsule as a multi-functional traditional Chinese medicine in treating chronic heart failure (CHF): A review of ingredients, molecular, cellular, and pharmacological mechanisms

Chronic heart failure (CHF) is a key part of cardiovascular continuum. Under the guidance of the theory of vessel-collateral doctrine, the present study proposes therapeutic benefits of Qili Qiangxin (QLQX) capsules, an innovative Chinese medicine, on chronic heart failure. The studies show that multiple targets of the drug on CHF, including enhancing myocardial systole, promoting urine excretion, inhibiting excessive activation of the neuroendocrine system, preventing ventricular remodeling by inhibiting inflammatory response, myocardial fibrosis, apoptosis and autophagy, enhancing myocardial energy metabolism, promoting angiogenesis, and improving endothelial function. Investigation on the effects and mechanism of the drug is beneficial to the treatment of chronic heart failure (CHF) through multiple targets and/or signaling pathways. Meanwhile, it provides new insights to further understand other refractory diseases in the cardiovascular continuum, and it also has an important theoretical and practical significance in enhancing prevention and therapeutic effect of traditional Chinese medicine for these diseases.

Tear function in patients with diabetes mellitus: A systematic review and meta-analysis

PURPOSE

To examine tear function in patients with diabetes mellitus (DM).

DESIGN

Systematic review and meta-analysis.

METHOD

We searched Embase and PubMed from database inception to March 16, 2022. We included observational studies that compared tear function between patients with and without DM. Tear function was measured using invasive tear breakup time (ITBUT) and Schirmer's 1 test. Pooled results are presented as standard mean difference (SMD) with 95% confidence interval (CI) based on random-effects models.

RESULTS

We included 59 studies (7,234 eyes) comparing the tear function between patients with and without DM. This meta-analysis indicated that patients with DM had worse tear function than those without DM (ITBUT: SMD: -0.98, 95% CI: -1.27 to -0.69; Schirmer's 1 test: SMD: -0.45, 95% CI: -0.64 to -0.26), and the results remained consistent in patients with different types of DM (e.g., type 1 DM and type 2 DM) and from different ethnic backgrounds (e.g., Asian vs. non-Asian). Patients with DM under poor glycemic control had worse tear function than those of the non-DM group (ITBUT: SMD: -1.26, 95% CI: -1.86 to -0.66; Schirmer's 1 test: SMD: -0.25, 95% CI: -0.48 to -0.02), whereas there were no significant differences in tear function between patients with DM under optimal glycemic control and non-DM groups.

CONCLUSIONS

We found that patients with type 1 or type 2 DM had significantly reduced tear function. The level of tear function could be determined by glycemic control, and therefore, our findings suggest that glycemic control in patients with DM is critical for maintaining tear function.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero, identifier CRD42021250498.

Potential underlying genetic associations between keratoconus and diabetes mellitus

Background Keratoconus (KC) is the most common ectatic corneal disease, characterized by significantly localized thinning of the corneal stroma. Genetic, environmental, hormonal, and metabolic factors contribute to the pathogenesis of KC. Additionally, multiple comorbidities, such as diabetes mellitus, may affect the risk of KC. Main Body Patients with diabetes mellitus (DM) have been reported to have lower risk of developing KC by way of increased endogenous collagen crosslinking in response to chronic hyperglycemia. However, this remains a debated topic as other studies have suggested either a positive association or no association between DM and KC. To gain further insight into the underlying genetic components of these two diseases, we reviewed candidate genes associated with KC and central corneal thickness in the literature. We then explored how these genes may be regulated similarly or differentially under hyperglycemic conditions and the role they play in the systemic complications associated with DM. Conclusion Our comprehensive review of potential genetic factors underlying KC and DM provides a direction for future studies to further determine the genetic etiology of KC and how it is influenced by systemic diseases such as diabetes.

Human tear fluid analysis for clinical applications: progress and prospects

Introduction: Human blood and saliva are increasingly under investigation for the detection of biomarkers for early diagnosis of non-communicable (e.g.cancers) and communicable diseases like COVID-19. Exploring the potential application of human tears, an easily accessible body fluid, for the diagnosis of various diseases is the need of the hour.Areas covered: This review deals with a comprehensive account of applications of tear analysis using different techniques, their comparison and overall progress achieved till now. The techniques used for tear fluid analysis are HPLC/UPLC/SDS-PAGE, CE, etc., together with ELISA, Mass Spectrometry, etc. But, with advances in instrumentation and data processing methods, it has become easy to couple the various separation methods with highly sensitive optical techniques for the analysis of body fluids.Expert opinion: Tear analysis can provide valuable information about the health condition of the eyes since it contains several molecular constituents, and their relative concentrations may alter under abnormal conditions. Tear analysis has the advantage that it is totally non-invasive. This study recommends tear fluid as a reliable clinical sample to be probed by highly sensitive optical techniques to diagnose different health conditions, with special emphasis on eye diseases.

TGFβ1, MMPs and cytokines profiles in ocular surface: Possible tear biomarkers for pseudoexfoliation

Purpose

Pseudoexfoliation (PXF) is a unique form of glaucoma characterized by accumulation of exfoliative material in the eyes. Changes in tear profile in disease stages may give us insights into molecular mechanisms involved in causing glaucoma in the eye.

Methods

All patients were categorized into three main categories; pseudoexfoliation (PXF), pseudoexfoliation glaucoma (PXG) and cataract, which served as control. Cytokines, transforming growth factor β1 (TGFβ1), matrix metalloproteases (MMPs) and fibronectin (FN1) were assessed with multiplex bead assay, enzyme-linked immunosorbent assay (ELISA), gelatin zymography, and immunohistochemistry (IHC) respectively in different ocular tissues such as tears, tenon’s capsule, aqueous humor (AH) and serum samples of patients with PXF stages.

Results

We found that TGFβ1, MMP-9 and FN1 protein expression were upregulated in tears, tenon’s capsule and AH samples in PXG compared to PXF, though the MMP-9 protein activity was downregulated in PXG compared with control or PXF. We have also found that in PXG tears sample the fold change of TGF-α (Transforming Growth Factor-α), MDC (Macrophage Derived Chemokine), IL-8 (Interleukin-8), VEGF (Vascular Endothelial Growth Factor) were significantly downregulated and the levels of GM-CSF (Granulocyte Macrophage Colony Stimulating Factor), IP-10 (Interferon- γ produced protein-10) were significant upregulated. While in AH; IL-6 (Interleukin-6), IL-8, VEGF, IFN-a2 (Interferon- α2), GRO (Growth regulated alpha protein) levels were found lower and IL1a (Interleukin-1α) level was higher in PXG compared to PXF. And in serum; IFN-a2, Eotaxin, GM-CSF, Fractalkine, IL-10 (Interleukin-10), IL1Ra (Interleukin-1 receptor antagonist), IL-7 (Interleukin-7), IL-8, MIP1β (Macrophage Inflammatory Protein-1β), MCP-1 (Monocyte Chemoattractant Protein-1) levels were significantly upregulated and PDGF-AA (Platelet Derived Growth Factor-AA) level was downregulated in the patients with PXG compared to PXF.

Conclusions

Altered expression of these molecules in tears may therefore be used as a signal for onset of glaucoma or for identifying eyes at risk of developing glaucoma in PXF.

Tear fluid collection methods: Review of current techniques

Tear fluid, composed of lipid, aqueous, and mucin layers, contains electrolytes, water, proteins, peptides, and glycoproteins. Its components may serve as diagnostic indicators of local and systemic diseases. The aim of the study was to conduct literature review in order to identify the current methods of tear collection. The most commonly used method which was relatively easy to perform and allowed to obtain sufficient tear volume for further chemical and physical analysis was selected through PubMed database search for the following keywords: tear sampling, human tears, chemical analysis of tears, physical tear analysis, animal tear sampling. Final criteria of articles selection were: human tears, tear sample collection, chemical and physical analysis of tears. Time of publication of the articles not older than 1995. The analysis of 70 articles revealed that the most common tear fluid collection methods are Schirmer tear strips and capillary tubes. Thus, we recommend the use of Schirmer strips and microcapillary tubes as the cheapest and easiest methods for sampling of tear fluid for further chemical analysis.

Tear Proteases and Protease Inhibitors: Potential Biomarkers and Disease Drivers in Ocular Surface Disease

Tears are highly concentrated in proteins relative to other biofluids, and a notable fraction of tear proteins are proteases and protease inhibitors. These components are present in a delicate equilibrium that maintains ocular surface homeostasis in response to physiological and temporal cues. Dysregulation of the activity of protease and protease inhibitors in tears occurs in ocular surface diseases including dry eye and infection, and ocular surface conditions including wound healing after refractive surgery and contact lens (CL) wear. Measurement of these changes can provide general information regarding ocular surface health and, increasingly, has the potential to give specific clues regarding disease diagnosis and guidance for treatment. Here, we review three major categories of tear proteases (matrix metalloproteinases, cathepsins, and plasminogen activators [PAs]) and their endogenous inhibitors (tissue inhibitors of metalloproteinases, cystatins, and PA inhibitors), and the changes in these factors associated with dry eye, infection and allergy, refractive surgery, and CLs. We highlight suggestions for development of these and other protease/protease inhibitor biomarkers in this promising field.

Intracerebral matrix metalloproteinase 9 in fatal diabetic ketoacidosis

There is increasing awareness that in addition to the metabolic crisis of diabetic ketoacidosis (DKA) caused by severe insulin deficiency, the immune inflammatory response is likely an active multicomponent participant in both the acute and chronic insults of this medical crisis, with strong evidence of activation for both the cytokine and complement system. Recent studies report that the matrix metalloproteinase enzymes and their inhibitors are systemically activated in young Type 1 diabetes mellitus (T1D) patients during DKA and speculate on their involvement in blood-brain barrier (BBB) disruption. Based on our previous studies, we address the question if matrix metalloproteinase 9 (MMP9) is expressed in the brain in the fatal brain edema (BE) of DKA. Our data show significant expression of MMP9 on the cells present in brain intravascular areas. The presence of MMP9 in intravascular cells and that of MMP+ cells seen passing the BBB indicates a possible role in tight junction protein disruption of the BBB, possibly leading to neurological complications including BE. We have also shown that MMP9 is expressed on neurons in the hippocampal areas of both BE/DKA cases investigated, while expression of tissue inhibitor of metalloproteinases 1 (TIMP1) was reduced in the same areas. We can speculate that intraneuronal MMP9 can be a sign of neurodegeneration. Further studies are necessary to determine the role of MMP9 in the pathogenesis of the neurologic catastrophe of the brain edema of DKA. Inhibition of MMP9 expression might be helpful in preserving neuronal function and BBB integrity during DKA.

MMP targeting in the battle for vision: Recent developments and future prospects in the treatment of diabetic retinopathy

Matrix metalloproteinases (MMPs) are enzymes capable of degrading nearly all types of extracellular matrix. They perform a wide range of roles in physiological processes, which is the reason for their strict regulation by numerous mechanisms including natural tissue inhibitors of metalloproteinases (TIMP). Research only started to shed light on more troublesome aspects of MMPs function, like cancer progression, Alzheimer's disease, atherosclerosis, ageing. Moreover, their profound role in diabetes is being carefully investigated including one of its most debilitating complications - diabetic retinopathy (DR), the leading cause of acquired blindness worldwide. Traditional treatment of this condition seems to be only mildly satisfactory, which elicited substantial interest in the field of new therapeutic methods including MMP targeting. So far, significant roles of MMP-2 and MMP-9 in the development of retinopathy have been established, with special attention given to the process of blood-retinal barrier impairment. Further exploration revealed MMP-10 and MMP-14 involvement as well as changes in MMP/TIMP ratio. In this review, we provide insight into MMPs role in diabetic retinopathy with a clarification of various mechanisms regulating MMP activity in the light of the recent studies. We conclude with an overview of novel DR therapies targeting MMPs and point to the need of further examination of their usefulness in clinical setting, with an eye towards future research.

Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine

In the field of predictive, preventive and personalised medicine, researchers are keen to identify novel and reliable ways to predict and diagnose disease, as well as to monitor patient response to therapeutic agents. In the last decade alone, the sensitivity of profiling technologies has undergone huge improvements in detection sensitivity, thus allowing quantification of minute samples, for example body fluids that were previously difficult to assay. As a consequence, there has been a huge increase in tear fluid investigation, predominantly in the field of ocular surface disease. As tears are a more accessible and less complex body fluid (than serum or plasma) and sampling is much less invasive, research is starting to focus on how disease processes affect the proteomic, lipidomic and metabolomic composition of the tear film. By determining compositional changes to tear profiles, crucial pathways in disease progression may be identified, allowing for more predictive and personalised therapy of the individual. This article will provide an overview of the various putative tear fluid biomarkers that have been identified to date, ranging from ocular surface disease and retinopathies to cancer and multiple sclerosis. Putative tear fluid biomarkers of ocular disorders, as well as the more recent field of systemic disease biomarkers, will be shown.

Human tear proteomics and peptidomics in ophthalmology: Toward the translation of proteomic biomarkers into clinical practice

Tears are a complex biological mixture containing electrolytes, metabolites, lipids, mucins, some small organic molecules, and proteins. The tear film has various roles in the lubrication, protection from the external environment, and nutrition of the cornea; it is also involved in the modulation of the optical properties of the eye. Tear composition reflects the physiological condition of the underlying tissues. Therefore, the tear fluid is useful in the evaluation of health and disease states and it is a valuable source of biomarkers for objective analysis of ocular and systemic diseases. The relatively high protein concentration of this fluid and the ease of noninvasive sample collection make it suitable for diagnostic and prognostic purposes. Efforts in proteomics research have positively affected to the field of ophthalmology, and the knowledge on the tear proteome has expanded considerably in the last few years. Nevertheless, despite a large amount of available data and the many biomarkers proposed for several eye and systemic diseases, the extent of translation to well-characterized and clinically useful tools has been largely insufficient. As for most of other biofluids, the road from discovery to clinical application is still long and full of pitfalls. In this review, we discuss the proteomic approaches used in the characterization of tear protein and peptide content, recapitulating the main studies and the progress done. We also present a brief summary of the path from discovery to clinical application of tear protein markers, with some representative examples of translation from the bench to the bedside.

SIGNIFICANCE

In this review we cover the most relevant proteomic approaches used in the characterization of the tear proteome, and for the first time we also focus in advances performed in the nowadays emerging peptide content characterization. In this context, we recapitulate on the main studies and the progresses done in this field. We also present a concise overview of the course that may be happen from discovery to clinical application for tear protein markers. Finally we include some representative examples of translation from the bench to the bedside.

The Role of Matrix Metalloproteinases in Diabetic Wound Healing in relation to Photobiomodulation

The integration of several cellular responses initiates the process of wound healing. Matrix Metalloproteinases (MMPs) play an integral role in wound healing. Their main function is degradation, by removal of damaged extracellular matrix (ECM) during the inflammatory phase, breakdown of the capillary basement membrane for angiogenesis and cell migration during the proliferation phase, and contraction and remodelling of tissue in the remodelling phase. For effective healing to occur, all wounds require a certain amount of these enzymes, which on the contrary could be very damaging at high concentrations causing excessive degradation and impaired wound healing. The imbalance in MMPs may increase the chronicity of a wound, a familiar problem seen in diabetic patients. The association of diabetes with impaired wound healing and other vascular complications is a serious public health issue. These may eventually lead to chronic foot ulcers and amputation. Low intensity laser irradiation (LILI) or photobiomodulation (PBM) is known to stimulate several wound healing processes; however, its role in matrix proteins and diabetic wound healing has not been fully investigated. This review focuses on the role of MMPs in diabetic wound healing and their interaction in PBM.

Stable Incretin Mimetics Counter Rapid Deterioration of Bone Quality in Type 1 Diabetes Mellitus

Type 1 diabetes mellitus is associated with a high risk for bone fractures. Although bone mass is reduced, bone quality is also dramatically altered in this disorder. However, recent evidences suggest a beneficial effect of the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) pathways on bone quality. The aims of the present study were to conduct a comprehensive investigation of bone strength at the organ and tissue level; and to ascertain whether enzyme resistant GIP or GLP-1 mimetic could be beneficial in preventing bone fragility in type 1 diabetes mellitus. Streptozotocin-treated mice were used as a model of type 1 diabetes mellitus. Control and streptozotocin-diabetic animals were treated for 21 days with an enzymatic-resistant GIP peptide ([D-Ala(2) ]GIP) or with liraglutide (each at 25 nmol/kg bw, ip). Bone quality was assessed at the organ and tissue level by microCT, qXRI, 3-point bending, qBEI, nanoindentation, and Fourier-transform infrared microspectroscopy. [D-Ala2]GIP and liraglutide treatment did prevent loss of whole bone strength and cortical microstructure in the STZ-injected mice. However, tissue material properties were significantly improved in STZ-injected animals following treatment with [D-Ala2]GIP or liraglutide. Treatment of STZ-diabetic mice with [D-Ala(2) ]GIP or liraglutide was capable of significantly preventing deterioration of the quality of the bone matrix. Further studies are required to further elucidate the molecular mechanisms involved and to validate whether these findings can be translated to human patients.

Tear and serum vitamin D levels in children with allergic rhinoconjunctivitis

BACKGROUND

Although solid cohort studies confirmed a preventative role for the anti-oxidant vitamin D in allergic asthma, a limited number of studies focused on allergic rhinoconjunctivitis (ARC). Here, we aimed to determine 25-hydroxycholecalciferol levels in tear and serum in young allergic rhinoconjunctivitis patients as compared to their apparently healthy matched controls.

METHODS

In total, 22 children with allergic rhinoconjunctivitis and 31 healthy control subjects underwent serum total IgE and 25-hydroxycholecalciferol measurements. Tear levels of 25-hydroxycholecalciferol were also determined in both groups.

RESULTS

The mean serum total IgE level in the ARC group (143.6±132.8IU/ml) was significantly higher than that in the control group (54.8±44.1IU/ml; p=0.03). Serum 25(OH)D levels were significantly higher in the ARC group (34.1±12.7ng/ml) than in the healthy controls (21.8±11.3ng/ml; p=0.001).

CONCLUSIONS

To our knowledge, this is the first reported study to show an association between serum 25-hydroxycholecalciferol and ARC in a childhood group. Higher levels of serum 25-hydroxycholecalciferol in children with allergic rhinoconjunctivitis may indicate a possible aetiopathogenic mechanism in the development of allergic rhinoconjunctivitis. This is also the first report to examine tear fluid vitamin D levels in paediatric ARC patients.

Alteration of the bone tissue material properties in type 1 diabetes mellitus: A Fourier transform infrared microspectroscopy study

Type 1 diabetes mellitus (T1DM) is a severe disorder characterized by hyperglycemia and hypoinsulinemia. A higher occurrence of bone fractures has been reported in T1DM, and although bone mineral density is reduced in this disorder, it is also thought that bone quality may be altered in this chronic pathology. Vibrational microscopies such as Fourier transform infrared microspectroscopy (FTIRM) represent an interesting approach to study bone quality as they allow investigation of the collagen and mineral compartment of the extracellular matrix in a specific bone location. However, as spectral feature arising from the mineral may overlap with those of the organic component, the demineralization of bone sections should be performed for a full investigation of the organic matrix. The aims of the present study were to (i) develop a new approach, based on the demineralization of thin bone tissue section to allow a better characterization of the bone organic component by FTIRM, (ii) to validate collagen glycation and collagen integrity in bone tissue and (iii) to better understand what alterations of tissue material properties in newly forming bone occur in T1DM. The streptozotocin-injected mouse (150 mg/kg body weight, injected at 8 weeks old) was used as T1DM model. Animals were randomly allocated to control (n = 8) or diabetic (n = 10) groups and were sacrificed 4 weeks post-STZ injection. Bones were collected at necropsy, embedded in polymethylmethacrylate and sectioned prior to examination by FTIRM. FTIRM collagen parameters were collagen maturity (area ratio between 1660 and 1690 cm(-1) subbands), collagen glycation (area ratio between the 1032 cm(-1) subband and amide I) and collagen integrity (area ratio between the 1338 cm(-1) subband and amide II). No significant differences in the mineral compartment of the bone matrix could be observed between controls and STZ-injected animals. On the other hand, as compared with controls, STZ-injected animals presented with significant higher value for collagen maturity (17%, p = 0.0048) and collagen glycation (99%, p = 0.0121), while collagen integrity was significantly lower by 170% (p = 0.0121). This study demonstrated the profound effect of early T1DM on the organic compartment of the bone matrix in newly forming bone. Further studies in humans are required to ascertain whether T1DM also lead to similar effect on the quality of the bone matrix.

Inflammation in childhood type 1 diabetes; influence of glycemic control

OBJECTIVE

Patients with type 1 diabetes have increased mortality from cardiovascular disease, and inflammation is important in the development of atherosclerosis. Our aim was to evaluate the extent of inflammation and the influence of glycemic control in the early phases of atherosclerosis in childhood type 1 diabetes.

MATERIALS AND METHODS

A population based cohort representative of all children with type 1 diabetes in Norway was studied. Diabetes patients (n = 314) were compared to healthy controls (n = 120), aged 8-18 years. Circulating levels of VCAM-1, ICAM-1, E-selectin, P-selectin, TNFα, IL-6, CRP, MCP-1, IL-18, MMP-9 and TIMP-1 were measured by immunoassays.

RESULTS

The diabetes patients had a mean age of 13.7 (SD = 2.8) years, disease duration of 5.5 (SD = 3.4) years and HbA1c of 8.4 (SD = 1.2) % (68 mmol/mol, SD = 13.1). The levels of most of the measured markers were significantly increased in the diabetes group compared to controls. In the diabetes group, all except MCP-1 and MMP-9 were significantly correlated to HbA1c, albeit the relation to VCAM-1 was inverse. There were no significant correlations in the control group. The measured markers were only to a limited degree associated with traditional risk factors. CRP showed the most pronounced difference between diabetes patients and controls and the strongest correlation with HbA1c. The use of oral contraceptives profoundly increased CRP levels, independent of the presence of diabetes.

CONCLUSIONS

Our results indicate that inflammation may play an important role in the accelerated atherosclerosis in early type 1 diabetes, and that this process seems primarily driven by hyperglycemia.

Contributions of ocular surface components to matrix-metalloproteinases (MMP)-2 and MMP-9 in feline tears following corneal epithelial wounding

Purpose

This study investigated ocular surface components that contribute to matrix-metalloproteinase (MMP)-2 and MMP-9 found in tears following corneal epithelial wounding.

Methods

Laboratory short-haired cats underwent corneal epithelial debridement in one randomly chosen eye (n = 18). Eye-flush tears were collected at baseline and during various healing stages. Procedural control eyes (identical experimental protocol as wounded eyes except for wounding, n = 5) served as controls for tear analysis. MMP activity was analyzed in tears using gelatin zymography. MMP staining patterns were evaluated in ocular tissues using immunohistochemistry and used to determine MMP expression sites responsible for tear-derived MMPs.

Results

The proMMP-2 and proMMP-9 activity in tears was highest in wounded and procedural control eyes during epithelial migration (8 to 36 hours post-wounding). Wounded eyes showed significantly higher proMMP-9 in tears only during and after epithelial restratification (day 3 to 4 and day 7 to 28 post-wounding, respectively) as compared to procedural controls (p<0.05). Tears from wounded and procedural control eyes showed no statistical differences for pro-MMP-2 and MMP-9 (p>0.05). Immunohistochemistry showed increased MMP-2 and MMP-9 expression in the cornea during epithelial migration and wound closure. The conjunctival epithelium exhibited highest levels of both MMPs during wound closure, while MMP-9 expression was reduced in conjunctival goblet cells during corneal epithelial migration followed by complete absence of the cells during wound closure. The immunostaining for both MMPs was elevated in the lacrimal gland during corneal healing, with little/no change in the meibomian glands. Conjunctival-associated lymphoid tissue (CALT) showed weak MMP-2 and intense MMP-9 staining.

Conclusions

Following wounding, migrating corneal epithelium contributed little to the observed MMP levels in tears. The major sources assessed in the present study for tear-derived MMP-2 and MMP-9 following corneal wounding are the lacrimal gland and CALT. Other sources included stromal keratocytes and conjunctiva with goblet cells.