Decreased contraction of glycated collagen lattices coincides with impaired matrix metalloproteinase production

Matrix Metalloproteinases on Skin Photoaging

BACKGROUND

Skin aging is characterized by an imbalance between the generation and degradation of extracellular matrix molecules (ECM). Matrix metalloproteinases (MMPs) are the primary enzymes responsible for ECM breakdown. Intrinsic and extrinsic stimuli can induce different MMPs. However, there is limited literature especially on the summary of skin MMPs and potential inhibitors.

OBJECTIVE

We aim to focus on the upregulation of MMP expression or activity in skin cells following exposure to UV radiation. We also would like to offer valuable insights into potential clinical applications of MMP inhibitors for mitigating skin aging.

METHODS

This article presents the summary of prior research, which involved an extensive literature search across diverse academic databases including Web of Science and PubMed.

RESULTS

Our findings offer a comprehensive insight into the effects of MMPs on skin aging after UV irradiation, including their substrate preferences and distinct roles in this process. Additionally, a comprehensive list of natural plant and animal extracts, proteins, polypeptides, amino acids, as well as natural and synthetic compounds that serve as inhibitors for MMPs is compiled.

CONCLUSION

Skin aging is a complex process influenced by environmental factors and MMPs. Research focuses on UV-induced skin damage and the formation of Advanced Glycosylation End Products (AGEs), leading to wrinkles and impaired functionality. Inhibiting MMPs is crucial for maintaining youthful skin. Natural sources of MMP inhibitor substances, such as extracts from plants and animals, offer a safer approach to obtain inhibitors through dietary supplements. Studying isolated active ingredients can contribute to developing targeted MMP inhibitors.

Challenges and opportunities of medicines for treating tendon inflammation and fibrosis: A comprehensive and mechanistic review

BACKGROUND

Tendinopathy refers to conditions characterized by collagen degeneration within tendon tissue, accompanied by the proliferation of capillaries and arteries, resulting in reduced mechanical function, pain, and swelling. While inflammation in tendinopathy can play a role in preventing infection, uncontrolled inflammation can hinder tissue regeneration and lead to fibrosis and impaired movement.

OBJECTIVES

The inability to regulate inflammation poses a significant limitation in tendinopathy treatment. Therefore, an ideal treatment strategy should involve modulation of the inflammatory process while promoting tissue regeneration.

METHODS

The current review article was prepared by searching PubMed, Scopus, Web of Science, and Google Scholar databases. Several treatment approaches based on biomaterials have been developed.

RESULTS

This review examines various treatment methods utilizing small molecules, biological compounds, herbal medicine-inspired approaches, immunotherapy, gene therapy, cell-based therapy, tissue engineering, nanotechnology, and phototherapy.

CONCLUSION

These treatments work through mechanisms of action involving signaling pathways such as transforming growth factor-beta (TGF-β), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), all of which contribute to the repair of injured tendons.

Preparation of injectable porcine skin-derived collagen and its application in delaying skin aging by promoting the adhesion and chemotaxis of skin fibroblasts

Collagen, as the main component of human skin, plays a vital role in maintaining dermal integrity. Its loss will lead to dermis destruction and collapse, resulting in skin aging. At present, injection of exogenous collagen is an important means to delay skin aging. In this study, high-purity collagen was extracted from porcine skin. Our research revealed that it can effectively promote the adhesion and chemotaxis of HSF cells. It can also reduce the expression of β-galactosidase, decrease ROS levels, and increase the expression of the collagen precursors, p53 and p16 in HSF cells during senescence. After local injection into the aging skin of rats, it was found that the number of cells and type I collagen fibers in the dermis increased significantly, and the arrangement of these fibers became more uniform and orderly. Moreover, the important thing is that it is biocompatible. To sum up, the porcine skin collagen we extracted is an anti-aging biomaterial with application potential.

Association of periodontitis and tooth loss with extent of coronary atherosclerosis in patients with type 2 diabetes mellitus

Aim

The objective was to investigate the association of periodontitis and tooth loss with extent of diabetic coronary atherosclerosis.

Materials and methods

272 patients who were hospitalized at Shanghai East hospital and underwent a coronary artery calcium (CAC) CT scan were enrolled in this study. Individuals were grouped based on their CAC scores into a normal-to-mild coronary atherosclerosis (AS) group (0 ≤ score ≤ 100, n=184) and a moderate-to-severe group (score≥101, n=88). Periodontitis parameters and number of missing teeth were evaluated for every patient. The severity of periodontitis was categorized as mild, moderate, or severe. The taxonomic composition of the microbiota was determined using full-length 16S ribosomal RNA gene sequencing. Salivary inflammatory factors were tested by ELISA.

Results

Clinical attachment loss (CAL) (P =0.05) and the number of teeth lost (P = 0.016) were significantly higher in the moderate-to-severe coronary AS group, with these differences being more obvious in younger patients and patients with short-duration diabetes. Multivariate logistic regression analysis revealed that CAL (OR = 1.231, 95% CI = 1.066-1.214, P = 0.047) and having 10-19 missing teeth (OR = 1.604, 95% CI = 1.393-6.555, P = 0.05) were strongly associated with the presence of moderate-to-severe coronary AS. Salivary IL-6 and TNF-α levels, as well as levels of Porphyromonas gingivalis and Neisseria mucosa, were significantly elevated in the moderate-to-severe coronary AS group.

Conclusion

It was found that both tooth loss and CAL were related to the extent of diabetic coronary AS. Saliva inflammatory factors and oral bacteremia may be new biomarkers for moderate-to-severe coronary AS.

Genome-wide association study identifies novel loci associated with skin autofluorescence in individuals without diabetes

BACKGROUND

Skin autofluorescence (SAF) is a non-invasive measure reflecting accumulation of advanced glycation endproducts (AGEs) in the skin. Higher SAF levels are associated with an increased risk of developing type 2 diabetes and cardiovascular disease. An earlier genome-wide association study (GWAS) revealed a strong association between NAT2 variants and SAF. The aim of this study was to calculate SAF heritability and to identify additional genetic variants associated with SAF through genome-wide association studies (GWAS).

RESULTS

In 27,534 participants without diabetes the heritability estimate of lnSAF was 33% ± 2.0% (SE) in a model adjusted for covariates. In meta-GWAS for lnSAF five SNPs, on chromosomes 8, 11, 15 and 16 were associated with lnSAF (P < 5 × 10^-8): 1. rs2846707 (Chr11:102,576,358,C > T), which results in a Met30Val missense variant in MMP27 exon 1 (NM_022122.3); 2. rs2470893 (Chr15:75,019,449,C > T), in intergenic region between CYP1A1 and CYP1A2; with attenuation of the SNP-effect when coffee consumption was included as a covariate; 3. rs12931267 (Chr16:89,818,732,C > G) in intron 30 of FANCA and near MC1R; and following conditional analysis 4. rs3764257 (Chr16:89,800,887,C > G) an intronic variant in ZNF276, 17.8 kb upstream from rs12931267; finally, 30 kb downstream from NAT2 5. rs576201050 (Chr8:18,288,053,G > A).

CONCLUSIONS

This large meta-GWAS revealed five SNPs at four loci associated with SAF in the non-diabetes population. Further unravelling of the genetic architecture of SAF will help in improving its utility as a tool for screening and early detection of diseases and disease complications.

Skin Structure-Function Relationships and the Wound Healing Response to Intrinsic Aging

Significance: Chronic wounds, such as diabetic foot ulcers, venous stasis ulcers, and pressure ulcers affect millions of Americans each year, and disproportionately afflict our increasingly older population. Older individuals are predisposed to wound infection, repeated trauma, and the development of chronic wounds. However, a complete understanding of how the attributes of aging skin affect the wound healing process has remained elusive. Recent Advances: A variety of studies have demonstrated that the dermal matrix becomes thinner, increasingly crosslinked, and fragmented with advanced age. These structural changes, as well as an increase in cell senescence, result in altered collagen fiber remodeling and increased stiffness. Studies combining mechanical testing with advanced imaging techniques are providing new insights into the relationships between these age-related changes. Emerging research into the mechanobiology of aging and the wound healing process indicate that the altered mechanical environment of aged skin may have a significant effect on age-related delays in healing. Critical Issues: The interpretation and synthesis of clinical studies is confounded by the effects of common comorbidities that also contribute to the development of chronic wounds. A lack of quantitative biomarkers of wound healing and age-related changes makes understanding structure-function relationships during the wound healing process challenging. Future Directions: Additional work is needed to establish quantitative and mechanistic relationships among age-related changes in the skin microstructure, mechanical function, and the cellular responses to wound healing.

Study of the Biomechanical and Histological Properties of the Abdominal Aorta of Diabetic Rats Exposed to Cigarette Smoke

INTRODUCTION

In spite of the great relevance of abdominal aortic aneurysm, its etiopathogenesis is not fully understood. The biomechanical and histological study of the aortic wall may contribute to this elucidation.

METHODS

Seventy-five male Wistar rats were divided into 4 groups: control (CG), smoker (SG), diabetic (DG), and diabetic + smoker (DSG). The SG and DSG rats were exposed to cigarette smoke for 30 min/day, 5 days a week. Diabetes was induced by the intravenous injection of streptozotocin. After 16 weeks, the abdominal aorta was collected for biomechanical, histological, and matrix metalloproteinase 2 (MMP-2) activity analyses.

RESULTS

The valid biomechanical tests of 52 specimens were analyzed: 11 in the CG, 10 in the DG, 16 in the SG, and 15 in the DSG. The biomechanical analysis of the fragments showed no differences between the control, DG, SG, and DSG. Collagen deposition also did not present a significant difference between the studied groups. The total count of elastic fibers was higher in diabetic rats (DG and DSG) than in the SG. The inflammatory response observed in all experimental groups was significantly more intense than in the CG. Compared to the DSG, MMP-2 activity showed a significant decrease in the DG.

CONCLUSIONS

Resistance and elasticity did not present a difference between the CG and the DG, SG, and DSG. Compared to the CG, the total count of elastic fibers, fragmentation of the elastic lamina, pericellular matrix deposition, and cell loss/substitution in the tunica media showed significant alterations in the aortic walls of the DG, SG, and DSG. MMP-2 activity was lower in the DG aorta than in the DSG aorta.

Acellular and cellular approaches to improve diabetic wound healing

Chronic diabetic wounds represent a huge socioeconomic burden for both affected individuals and the entire healthcare system. Although the number of available treatment options as well as our understanding of wound healing mechanisms associated with diabetes has vastly improved over the past decades, there still remains a great need for additional therapeutic options. Tissue engineering and regenerative medicine approaches provide great advantages over conventional treatment options, which are mainly aimed at wound closure rather than addressing the underlying pathophysiology of diabetic wounds. Recent advances in biomaterials and stem cell research presented in this review provide novel ways to tackle different molecular and cellular culprits responsible for chronic and nonhealing wounds by delivering therapeutic agents in direct or indirect ways. Careful integration of different approaches presented in the current article could lead to the development of new therapeutic platforms that can address multiple pathophysiologic abnormalities and facilitate wound healing in patients with diabetes.

[Antidiabetic role of high density lipoproteins]

Disturbance in lipid metabolism can be both a cause and a consequence of the development of diabetes mellitus (DM). One of the most informative indicator of lipid metabolism is the ratio of atherogenic and antiatherogenic fractions of lipoproteins and their protein components. The review summarizes literature data and own results indicating the important role of high-density lipoprotein (HDL) and their main protein component, apolipoprotein A-I (apoA-I), in the pathogenesis of type 2 DM. On the one hand, HDL are involved in the regulation of insulin secretion by b-cells and insulin-independent absorption of glucose. On the other hand, insulin resistance and hyperglycemia lead to a decrease in HDL levels and cause modification of their protein component. In addition, HDL, possessing anti-inflammatory and mitogenic properties, provide anti-diabetic protection through systemic mechanisms. Thus, maintaining a high concentration of HDL and apoA-I in blood plasma and preventing their modification are important issues in the context of prevention and treatment of diabetes.

Mesenchymal Stem Cells from Adipose Tissue in Clinical Applications for Dermatological Indications and Skin Aging

Operating at multiple levels of control, mesenchymal stem cells from adipose tissue (ADSCs) communicate with organ systems to adjust immune response, provide signals for differentiation, migration, enzymatic reactions, and to equilibrate the regenerative demands of balanced tissue homeostasis. The identification of the mechanisms by which ADSCs accomplish these functions for dermatological rejuvenation and wound healing has great potential to identify novel targets for the treatment of disorders and combat aging. Herein, we review new insights into the role of adipose-derived stem cells in the maintenance of dermal and epidermal homeostasis, and recent advances in clinical applications of ADSCs related to dermatology.

Type I Collagen Purification from Rat Tail Tendons

Type I collagen, or collagen I, is the most abundant protein in the human body and provides strength and resiliency to tissues such as bone, tendons, ligaments, and skin. Collagen I forms macromolecular networks in which resident mesenchymal cells are embedded. Cell-extracellular matrix interactions are critical not only for maintenance of tissue properties but also for guiding and orienting the phenotype of resident cells. Cues from the extracellular matrix have been shown to be critical in pathophysiologies such as fibrosis, aging, and cancer. Hence, the details of these interactions are being scrutinized to better understand the mechanisms of such diseases and conditions. Many in vitro assays, such as cell-embedded collagen lattices, preparation of hydrogels, adhesion assays, etc., have been developed to study various aspects of cell-extracellular matrix interactions. All these in vitro models rely on utilizing high-quality purified collagen I. Here, we provide state-of-the-art collagen I extraction protocol and useful tips to produce high-quality purified collagen I solutions. We also provide a detailed protocol for pepsin digestion of collagen I, for a highly reliable collagen concentration assay, and guidelines for conducting quality controls to validate purified collagen solutions. Collagen I prepared with these procedures is highly suitable for many in vitro applications.

Matrix Metalloproteinase-3 Differences in Oral and Skin Fibroblasts

While skin wounds heal by scarring, wounds of oral mucosa show privileged healing with minimal scar formation. Our hypothesis was that phenotypic differences between oral and skin fibroblasts underlie these differences in healing. The aims of this study were to compare MMP-3 expression by oral and skin fibroblasts and investigate a role for MMP-3 in mediating collagen gel contraction. Oral fibroblasts induced significantly greater gel contraction than did paired skin cells. Inhibition of MMP activity significantly inhibited gel contraction by both cell types. Specific inhibition of MMP-3 activity reduced gel contraction by oral, but not skin, fibroblasts. Oral fibroblasts produced significantly higher levels of MMP-3 than did skin fibroblasts at all levels studied. TGF-β1 and -β3 isoforms stimulated MMP-3 expression at mRNA, protein, and activity levels by both fibroblast populations. Results suggest that increased MMP-3 production by oral fibroblasts may underlie the differences in wound-healing outcome seen in skin and oral mucosa.

Hyperglycemia-Induced Modulation of the Physiognomy and Angiogenic Potential of Fibroblasts Mediated by Matrix Metalloproteinase-2: Implications for Venous Stenosis Formation Associated with Hemodialysis Vascular Access in Diabetic Milieu

Purpose:

It is hypothesized that venous stenosis formation associated with hemodialysis vascular-access failure is caused by hypoxia-mediated fibroblast-to-myofibroblast differentiation accompanied by proliferation and migration, and that diabetic patients have worse clinical outcomes. The aim of this study was to determine the functional and gene expression outcomes of matrix metalloproteinase-2 (Mmp-2) silencing in fibroblasts cultured under hyperglycemia and euglycemia with hypoxic and normoxic stimuli.

Materials and Methods:

AKR-2B fibroblasts were stably transduced using lentivirus-mediated shRNA-Mmp-2 or scrambled controls and subjected to hypoxia or normoxia under hyperglycemic or euglycemic conditions for 24 and 72 h. Gene expression of vascular endothelial growth factor-A (Vegf-A), Vegfr-1, Mmp-2, Mmp-9 and tissue inhibitors of matrix metalloproteinases (Timps) were determined by RT-PCR. Collagen I and IV secretion and cellular proliferation and migration were determined.

Results:

Under hyperglycemic conditions, there is a significant reduction in the average gene expression of Vegf-A and Mmp-9, with an increase in Timp-1 at 24 h of hypoxia (p < 0.05) in Mmp-2-silenced fibroblasts when compared to controls. In addition, there is a decrease in collagen I and IV secretion and cellular migration. The euglycemic cells were able to reverse these findings.

Conclusion:

These findings demonstrate the rationale for using anti-Mmp-2 therapy in dialysis patients with hemodialysis vascular access in helping to reduce stenosis formation.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Natural and sun-induced aging of human skin

With worldwide expansion of the aging population, research on age-related pathologies is receiving growing interest. In this review, we discuss current knowledge regarding the decline of skin structure and function induced by the passage of time (chronological aging) and chronic exposure to solar UV irradiation (photoaging). Nearly every aspect of skin biology is affected by aging. The self-renewing capability of the epidermis, which provides vital barrier function, is diminished with age. Vital thermoregulation function of eccrine sweat glands is also altered with age. The dermal collagenous extracellular matrix, which comprises the bulk of skin and confers strength and resiliency, undergoes gradual fragmentation, which deleteriously impacts skin mechanical properties and dermal cell functions. Aging also affects wound repair, pigmentation, innervation, immunity, vasculature, and subcutaneous fat homeostasis. Altogether, age-related alterations of skin lead to age-related skin fragility and diseases.

Matrix metalloproteinase-2 is downregulated in sciatic nerve by streptozotocin induced diabetes and/or treatment with minocycline: Implications for nerve regeneration

Minocycline is an inhibitor of matrix metalloproteinases (MMPs) and has been shown to have analgesic effects. Whilst increased expression of MMPs is associated with neuropathic pain, MMPs also play crucial roles in Wallerian degeneration and nerve regeneration. In this study we examined the expression of MMP-2, MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1/-2 in the sciatic nerve of control and streptozotocin-induced diabetic rats treated with either vehicle or minocycline by quantitative PCR and gelatin zymography. We assessed the effects of minocycline on nerve conduction velocity and intraepidermal nerve fibre (IENF) deficits in diabetic neuropathy and investigated the effects of minocycline or MMP-2 on neurite outgrowth from primary cultures of dissociated adult rat sensory neurons.

We show that MMP-2 is expressed constitutively in the sciatic nerve in vivo and treatment with minocycline or diabetes leads to downregulation of MMP-2 expression and activity. The functional consequence of this is IENF deficits in minocycline-treated nondiabetic rats and an unsupportive microenvironment for regeneration in diabetes. Minocycline reduces levels of MMP-2 mRNA and nerve growth factor-induced neurite outgrowth. Furthermore, in vivo minocycline treatment reduces preconditioning-induced in vitro neurite outgrowth following a sciatic nerve crush. In contrast, the addition of active MMP-2 facilitates neurite outgrowth in the absence of neurotrophic support and pre-treatment of diabetic sciatic nerve substrata with active MMP-2 promotes a permissive environment for neurite outgrowth. In conclusion we suggest that MMP-2 downregulation may contribute to the regenerative deficits in diabetes. Minocycline treatment also downregulates MMP-2 activity and is associated with inhibitory effects on sensory neurons. Thus, caution should be exhibited with its use as the balance between beneficial and detrimental outcomes may be critical in assessing the benefits of using minocycline to treat diabetic neuropathy.

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MMP-2, but not MMP-9, is constitutively expressed in the adult rat sciatic nerve.

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Levels of cleaved active MMP-2 are reduced in sciatic nerve of diabetic rats.

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Active MMP-2 potentiates neurite outgrowth from sensory neurons.

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Minocycline reduces levels of MMP-2 mRNA and impairs NGF-induced neurite growth.

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Minocycline did not prevent nerve dysfunction in experimental diabetic neuropathy.

Glycated Collagen Decreased Endothelial Cell Fibronectin Alignment in Response to Cyclic Stretch Via Interruption of Actin Alignment

Hyperglycemia is a defining characteristic of diabetes, and uncontrolled blood glucose in diabetes is associated with accelerated cardiovascular disease. Chronic hyperglycemia glycates extracellular matrix (ECM) collagen, which can lead to endothelial cell dysfunction. In healthy conditions, endothelial cells respond to mechanical stimuli such as cyclic stretch (CS) by aligning their actin cytoskeleton. Other cell types, specifically fibroblasts, align their ECM in response to CS. We previously demonstrated that glycated collagen inhibits endothelial cell actin alignment in response to CS. The aim of this study was to determine the effect of glycated collagen on ECM remodeling and protein alignment in response to stretch. Porcine aortic endothelial cells (PAEC) seeded on native or glycated collagen coated elastic substrates were exposed to 10% CS. Cells on native collagen aligned subcellular fibronectin fibers in response to stretch, whereas cells on glycated collagen did not. The loss of fibronectin alignment was due to inhibited actin alignment in response to CS, since fibronectin alignment did not occur in cells on native collagen when actin alignment was inhibited with cytochalasin. Further, while ECM protein content did not change in cells on native or glycated collagen in response to CS, degradation activity decreased in cells on glycated collagen. Matrix metalloproteinase 2 (MMP-2) and membrane-associated type 1 matrix metalloproteinase (MT1-MMP) protein levels decreased, and therefore MMP-2 activity also decreased. These MMP changes may relate to c-Jun N-terminal kinase (Jnk) phosphorylation inhibition with CS, which has previously been linked to focal adhesion kinase (FAK). These data demonstrate the importance of endothelial cell actin tension in remodeling and aligning matrix proteins in response to mechanical stimuli, which is critical to vascular remodeling in health and disease.

Periodontitis and diabetes associations with measures of atherosclerosis and CHD

OBJECTIVE

Diabetes has been linked with more severe periodontal disease and with coronary heart disease (CHD). The purpose of this study was to determine if periodontal infection was a significant modifier in the risk that diabetes poses for increased carotid artery intimal-medial wall thickness (IMT) and more advanced atheroma lesions as reflected in atherosclerotic plaque calcification measured by acoustic shadowing.

METHODS AND RESULTS

Comparisons for analyses of cardiovascular outcomes were performed based upon periodontitis and diabetes status. Periodontitis was measured using pocket depth and attachment loss at six sites per tooth. Cross-sectional data on 6048 persons aged 52-74 years were obtained from the Dental Atherosclerosis Risk in Communities Study. Participants without diabetes (n=5257) were compared to those with diabetes (n=791). Dependent variables were thick IMT (>1 mm), presence of acoustic shadowing, and prevalent CHD. All models were adjusted for the following covariates: gender, age, race/center, LDL and HDL cholesterol, BMI, triglycerides, hypertension, smoking, income and education. For multivariate model building, all non-normally distributed variables were transformed and multivariable logistic regression analyses were performed to evaluate the relationship between periodontal infection, diabetes, and cardiovascular outcomes. Individuals with diabetes and with severe periodontitis were found to be significantly more likely to have IMT>1 mm [OR=2.2, (1.4-3.5)], acoustic shadowing [OR=2.5, (1.3-4.6)], and CHD [OR=2.6, (1.6-4.2)] compared to those without diabetes or periodontal disease.

CONCLUSION

Results from this study suggest that among people with diabetes, periodontal disease may increase the likelihood of subclinical atherosclerotic heart disease and CHD.

Impaired biomechanical properties of diabetic skin implications in pathogenesis of diabetic wound complications

Diabetic skin is known to have deficient wound healing properties, but little is known of its intrinsic biomechanical properties. We hypothesize that diabetic skin possesses inferior biomechanical properties at baseline, rendering it more prone to injury. Skin from diabetic and nondiabetic mice and humans underwent biomechanical testing. Real-time PCR was performed for genes integral to collagen synthesis and degradation. MMP-2 and MMP-9, and TIMP-1 protein levels were assessed by ELISA and zymography. Collagen I and III content was assessed using Western blot analysis. At baseline, both murine and human diabetic skin was biomechanically inferior compared to nondiabetic skin, with decreased maximum stress and decreased modulus (P < 0.001 and < 0.05, respectively). Surprisingly, the expression of genes involved in collagen synthesis were significantly up-regulated, and genes involved in collagen degradation were significantly down-regulated in murine diabetic skin (P < 0.01). In addition, MMP-2 and MMP-9/TIMP-1 protein ratios were significantly lower in murine diabetic skin (P < 0.05). Collagen I levels and I:III ratios were lower in diabetic skin (P < 0.05). These findings suggest that the predisposition of diabetics to wounds may be the result of impaired tissue integrity at baseline, and are due, in part, to a defect in the regulation of collagen protein synthesis at the post-transcriptional level.

‘Young’ Oral Fibroblasts Are Geno/Phenotypically Distinct

Wound healing within the oral mucosa results in minimal scar formation compared with wounds within the skin. We have recently demonstrated distinct differences in the aging profiles of cells (oral mucosal and patient-matched skin fibroblasts) isolated from these tissues. We hypothesized that the increased replicative potential of oral mucosal fibroblasts may confer upon them preferential wound-healing capacities. Passage-matched early cultures of oral mucosal fibroblasts and skin fibroblasts demonstrated distinct gene expression profiles, with several genes linked to wound healing/tissue repair. This was related to an increased ability of the ‘replicatively younger’ oral mucosal fibroblasts to repopulate a wound space and reorganize their surrounding extracellular matrix environment, key activities during the wound-healing process. We conclude that oral mucosal fibroblasts exhibit a preferential healing response in vivo, due to their ‘replicatively younger’ phenotype when compared with that of patient-matched skin fibroblasts.

Processing of type I collagen gels using nonenzymatic glycation

This study focuses on the development of a novel method of nonenzymatic glycation of fibrillar collagen gels. In contrast to previous studies in which type I collagen gels were glycated in the solid state, this study presents a method for glycation in solution. The type I collagen in solution or gels was exposed to a range of ribose concentrations from 0 to 250 mM. The binding of ribose to collagen was documented using Fourier transform infrared (FTIR) spectroscopy. formation of advanced glycation end products (AGEs) was quantified by fluorescence measurement. The bulk compressive modulus and viscoelastic time constant of processed gels were determined in stress relaxation studies. Both methods of glycation enhanced ribose addition and AGE formation in a dose-dependent manner, with glycation in the gel state being more efficient. Both methods enhanced mechanical properties similarly, with 250 mM ribose treatment resulting in a 10-fold increase in bulk modulus.

The bladder extracellular matrix. Part I: architecture, development and disease

From the earliest studies with epithelial cells implanted into detrusor muscle to later experiments on smooth muscle in defined collagen gels, cell niche and extracellular matrix (ECM) have been clearly shown to orchestrate cellular behavior and fate whether quiescent, migratory, or proliferative. Normal matrix can revert transformed cells to quiescence, and damaged matrix can trigger malignancy or dedifferentiation. ECM influence in disease, development, healing and regeneration has been demonstrated in many other fields of study, but a thorough examination of the roles of ECM in bladder cell activity has not yet been undertaken. Structural ECM proteins, in concert with adhesive proteins, provide crucial structural support to the bladder. Both structural and nonstructural components of the bladder have major effects on smooth muscle function, through effects on matrix rigidity and signaling through ECM receptors. While many ECM components and receptors identified in the bladder have specific known functions in the vascular smooth musculature, their function in the bladder is often less well defined. In cancer and obstructive disease, the ECM has a critical role in pathogenesis. The challenge in these settings will be to find therapies that prevent hyperproliferation and encourage proper differentiation, through an understanding of matrix effects on cell biology and susceptibility to therapeutics.

Collagen glycation alters neovascularization in vitro and in vivo

Microvascular network formation is required for the success of many therapies in regenerative medicine. The process of vessel assembly is fundamentally altered, however, in many people within the potential patient population, including the elderly and people with diabetes. Significant research has been performed to determine how cellular dysfunction contributes to this inadequate neovascularization, but alterations in the extracellular matrix (ECM) may also influence this process. Glycation of ECM proteins, specifically type I collagen, increases as people age and is accelerated due to uncontrolled diabetes. This glycation results in increased ECM stiffness and resistance to degradation. The goal of this research is to determine whether collagen glycation consistent with changes in aged (defined as people older than 80 years old) and diabetic individuals influences neovascularization. Collagen gels that were incubated in glucose-6-phopshate (G6P) for varying times exhibited cross-linking (26.2+/-8.1% and 31.3+/-5.6% for incubation in 375 mM G6P for 5 and 8 days, respectively), autofluorescence, and advanced glycation end product levels (666+/-481 and 2122+/-501 pmol/mg protein for 5 and 8 days of 375 mM G6P, respectively) consistent with aged and diabetic populations. Three-dimensional culture models showed that sprouting angiogenesis was delayed in collagen gels with high levels of glycation. When implanted in vivo, glycated gels were degraded (44.4+/-4.2% and 49.5+/-11.7% nondegraded gel remaining for gels incubated for 5 and 8 days in 375 mM G6P, respectively) and vascularized (75.5+/-32.0 and 73.7+/-23.6 vessels/mm(2)) more slowly than controls (22.3+/-9.9% gel remaining and 133.3+/-31.0 vessels/mm(2)). These results suggest that glycation of collagen can alter neovascularization and may contribute to alterations in vessel assembly observed as people age and due to diabetes.

Effects of extracellular matrix glycosylation on proliferation and apoptosis of human dermal fibroblasts via the receptor for advanced glycosylated end products

The balance between proliferation and apoptosis of skin cells is responsible for skin turnover and the success of the wound healing process. Recent reports have shown that advanced glycosylation end product (AGE) formation participates in dermatologic problems in diabetes. However, the effect on proliferation and apoptosis of dermal fibroblasts remains unclear. The aim of this study was to investigate the effects of dermal microenvironment glycosylation on the balance of cellular proliferation and apoptosis. Histology and immunohistochemical staining were performed on type II diabetic and nondiabetic skin tissue specimens to determine the distributions of proliferating cell nuclear antigen, apoptotic cells, AGEs, and receptors for AGEs (RAGEs). Matrix secreted by cultured human fibroblasts was glycosylated by 0.5 M D-ribose. RAGE-blocking antibodies were applied to inhibit the interaction of RAGE and AGEs in this system and then cell viability, cell cycle phase distribution, and apoptosis were measured. Diabetic skin has degenerative, loosely arranged collagen and increased apoptotic cells compared with normal skin. Expression of AGE and RAGE in diabetic skin tissue increased. Glycosylated matrix induced cell cycle arrest and apoptosis of cultured dermal fibroblasts, whereas application of RAGE-blocking antibodies redressed these changes. The accumulation of glycosylated extracellular matrix in diabetic skin tissue is a critical mediator of cellular function. Mediation of RAGE affects the balance of cellular proliferation and apoptosis, which confirms that diabetic wounds possess atypical origin in the repair process.

Looking older: fibroblast collapse and therapeutic implications

Skin appearance is a primary indicator of age. During the last decade, substantial progress has been made toward understanding underlying mechanisms of human skin aging. This understanding provides the basis for current use and new development of antiaging treatments. Our objective is to review present state-of-the-art knowledge pertaining to mechanisms involved in skin aging, with specific focus on the dermal collagen matrix. A major feature of aged skin is fragmentation of the dermal collagen matrix. Fragmentation results from actions of specific enzymes (matrix metalloproteinases) and impairs the structural integrity of the dermis. Fibroblasts that produce and organize the collagen matrix cannot attach to fragmented collagen. Loss of attachment prevents fibroblasts from receiving mechanical information from their support, and they collapse. Stretch is critical for normal balanced production of collagen and collagen-degrading enzymes. In aged skin, collapsed fibroblasts produce low levels of collagen and high levels of collagen-degrading enzymes. This imbalance advances the aging process in a self-perpetuating, never-ending deleterious cycle. Clinically proven antiaging treatments such as topical retinoic acid, carbon dioxide laser resurfacing, and intradermal injection of cross-linked hyaluronic acid stimulate production of new, undamaged collagen. Attachment of fibroblasts to this new collagen allows stretch, which in turn balances collagen production and degradation and thereby slows the aging process. Collagen fragmentation is responsible for loss of structural integrity and impairment of fibroblast function in aged human skin. Treatments that stimulate production of new, nonfragmented collagen should provide substantial improvement to the appearance and health of aged skin.

Reconstructed skin modified by glycation of the dermal equivalent as a model for skin aging and its potential use to evaluate anti-glycation molecules

Glycation is a slow chemical reaction which takes place between amino residues in protein and a reducing sugar. In skin this reaction creates new residues or induces the formation of cross-links (advanced glycation end products or AGEs) in the extracellular matrix of the dermis. Formation of such cross-links between macromolecules may be responsible for loss of elasticity or modification of other properties of the dermis observed during aging. We had previously developed a reconstructed skin model which enabled us to study the consequences of matrix alteration by preglycation of the collagen and have reported several modifications of interest induced by glycation in the dermal and epidermal compartments of reconstructed skin as well as at the level of the dermal-epidermal junction. For example we showed that collagen IV and laminin were increased in the basement membrane zone and that alpha6 and beta1 integrins in epidermis were expanded to suprabasal layers. The aim of this new study was to look at the biological effects of glycation inhibitors like aminoguanidine in the skin model. Aminoguanidine was mixed with collagen in the presence of ribose as reducing sugar, and immunostaining was used to visualize its effects on AGE Products and biological markers. After aminoguanidine treatment, we found a low amount of AGE products and a possible return to the normal pattern of distribution of markers in skin constructs as compared to those treated with ribose only. Interestingly similar results were also obtained, although to a lesser extent, with a blueberry extract. In conclusion the glycation inhibitory effect has been functionally demonstrated in the reconstructed skin model and it is shown that this model can be used to assess anti-glycation agents.

Reduced MMP-2 activity contributes to cardiac fibrosis in experimental diabetic cardiomyopathy

OBJECTIVE

To evaluate the regulation of matrix metalloproteinase (MMP)-2 in diabetic cardiomyopathy.

METHODS

Left ventricle (LV) function was determined by a micro-tip catheter in streptozotocin (STZ)-induced diabetic rats, 2 or 6 weeks (w) after STZ-application. LV total collagen, collagen type I and III content were immunohistologically analyzed and quantified by digital image analysis. LV collagen type I, III and MMP-2 mRNA expression was quantified by real-time RT-PCR. LV pro- and active MMP-2 levels were analyzed by zymography; Smad 7, membrane type (MT)1-MMP and tissue inhibitor metalloproteinase (TIMP)-2 protein levels by Western Blot.

RESULTS

STZ-induced diabetes was associated with a time-dependent impairment of LV diastolic and systolic function. This was paralleled by a time-dependent increase in LV total collagen content, despite reduced LV collagen type I and III mRNA levels, indicating a role of post-transcriptional/post-translational changes of extracellular matrix regulation. Six weeks (w) after STZ-injection, MMP-2 mRNA expression and pro-MMP-2 levels were 2.7-fold (P < 0.005) and 1.3-fold (P < 0.05) reduced versus controls, respectively, whereas active MMP-2 was decreased to undetectable levels 6 w post-STZ. Concomitantly, Smad 7 and TIMP-2 protein levels were 1.3-fold (P < 0.05) and 10-fold (P < 0.005) increased in diabetics versus controls, respectively, whereas the 45 kDa form of MT1-MMP was undetectable in diabetics.

CONCLUSION

Under STZ-diabetic conditions, cardiac fibrosis is associated with a dysregulation in extracellular matrix degradation. This condition is featured by reduced MMP-2 activity, concomitant with increased Smad 7 and TIMP-2 and decreased MT1-MMP protein expression, which differs from mechanisms involved in dilated and ischemic heart disease.

Negative Association between Infra-renal Aortic Diameter and Glycaemia: The Health In Men Study

OBJECTIVE

There is evidence of a negative association between diabetes and abdominal aortic aneurysm (AAA). The aim of this study was to assess whether there is a similar relationship between both diabetes and glucose level, and infra-renal aortic diameter throughout its range.

DESIGN AND METHODS

Infra-renal aortic diameter was measured using ultrasound in 12,203 men aged 65-83 years as part of a trial of screening for AAA. A range of cardiovascular risk factors were also assessed. In a follow-up study, fasting serum glucose was measured in 2,859 non-diabetic men. Aortic diameter was logarithmically transformed and treated as both a continuous and categorical variable in stepwise multivariate linear and logistic models.

RESULTS

The median aortic diameter was slightly smaller in the diabetic men (21.3+/-3.9 vs 21.6+/-3.8, P<0.0001). There was an independent negative association between diabetes and AAA (OR 0.79, 95% CI: 0.63,0.98), and an inverse correlation (Coefficient: -0.0064, p=0.0024) between fasting glucose and aortic diameter in non-diabetic men.

CONCLUSIONS

Diabetes is inversely associated with both AAA and aortic diameter in men over 65 years. This association is independent of other risk factors for AAA. Aortic diameter also has an inverse relationship with fasting glucose concentrations in men without diabetes.

Carbamylation differentially alters type I collagen sensitivity to various collagenases

Carbamylation is a post-translational modification due to nonenzymatic binding of cyanate, a by-product of urea, on free amino groups of proteins. Post-translational modifications are known to induce alterations in structural and functional properties of proteins, thus disturbing protein-protein or cell-protein interactions. We report the impact of carbamylation on type I collagen sensitivity to enzymatic proteolysis. Type I collagen was extracted from rat tail tendons and carbamylated by incubation with 0.1 M potassium cyanate at 37 degrees C for 2, 6 or 24 h. Degradation assays revealed that carbamylated collagen exhibited a greater resistance to collagenases (i.e. bacterial collagenase, matrix metalloproteinase(MMP)-1, MMP-8 and MMP-13), together with an increased sensitivity to MMP-2. Evaluation of collagen triple helix conformation by polarimetry indicated that local destabilizations of triple helix structure related to carbamylation could be responsible for the observed differences in sensitivity. These results confirm the crucial role of triple helix integrity in the degradation of type I collagen by MMPs, and support the deleterious impact of post-translational modifications in vivo by altering the balanced remodeling of collagen within connective tissue.

Phagocytosis and remodeling of collagen matrices

The biodegradation of collagen and the deposition of new collagen-based extracellular matrices are of central importance in tissue remodeling and function. Similarly, for collagen-based biomaterials used in tissue engineering, the degradation of collagen scaffolds with accompanying cellular infiltration and generation of new extracellular matrix is critical for the integration of in vitro grown tissues in vivo. In earlier studies we observed significant impact of collagen structure on primary lung fibroblast behavior in vitro in terms of collagen uptake and matrix remodeling. Therefore, in the present work, the response of human fibroblasts (IMR-90) to the structural state of collagen was studied with respect to phagocytosis in the presence and absence of inhibitors. Protein content and transcript levels for collagen I (Col-1), matrix metalloproteinase 1 (MMP-1), matrix metalloproteinase 2 (MMP-2), tissue inhibitor of matrix metalloproteinase 1 (TIMP-1), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2), and heat shock protein 70 (HSP-70) were characterized as a function of collagen matrix concentration, structure and cell culture time to assess effects on cellular collagen matrix remodeling processes. Phagocytosis of collagen was assessed quantitatively by the uptake of collagen-coated fluorescent beads incorporated into the collagen matrices. Significantly higher levels of collagen phagocytosis were observed for the cells grown on the denatured collagen versus native collagen matrices. Significant reduction in collagen phagocytosis was observed by blocking several phagocytosis pathways when the cells were grown on denatured collagen versus non-denatured collagen. Collagen phagocytosis inhibition effects were significantly greater for PDL57 IMR-90 cells versus PDL48 cells, reflecting a reduced number of collagen processing pathways available to the older cells. Transcript levels related to the deposition of new extracellular matrix proteins varied as a function of the structure of the collagen matrix presented to the cells. A four-fold increase in transcript level of Col-1 and a higher level of collagen matrix incorporation were observed for cells grown on denatured collagen versus cells grown on non-denatured collagen. The data suggest that biomaterial matrices incorporating denatured collagen may promote more active remodeling toward new extracellular matrices in comparison to cells grown on non-denatured collagen. A similar effect of cellular action toward denatured (wound-related) collagen in the remodeling of tissues in vivo may have significant impact on tissue regeneration as well as the progression of collagen-related diseases.

Matrix biology of abdominal aortic aneurysms in diabetes: mechanisms underlying the negative association

Several case-control studies have shown a significant negative association between diabetes and abdominal aortic aneurysm (AAA). This interaction has the potential to further our understanding of these two diseases but has attracted little research. The changes seen in the walls of aneurysmal aortas include inflammation and the activation of proteolytic pathways resulting in loss of elastin and other structural proteins. In contrast, diabetes is associated with increased synthesis and reduced degradation of matrix. The deposition of advanced glycation end products also renders vascular matrix resistant to proteolysis in diabetic patients. The aim of our present minireview is to compare the changes in matrix biology seen in diabetes and AAA and to explore molecular mechanisms that may explain the negative association and identify possible therapeutic implications.

The molecular biology of chronic wounds and delayed healing in diabetes

Wound healing is a complicated and integrated process. Although there is some tolerance in terms of redundancy and interrelated control mechanisms, pushing beyond such limits may contribute to delayed wound healing, and in extreme cases lead to chronic wounds/ulcers and thus potentially to lower extremity amputation. Diabetes is associated with such disruption in wound healing. Research in humans and in animal models has identified a large number of changes associated with diabetes at the molecular level in delayed wound healing and to a lesser extent in chronic diabetic ulcers. Better overall understanding of these changes and how they are interrelated would allow for specifically targeted treatment, thus ensuring improved quality of life for patients and providing savings to the high costs that are associated with all aspects of chronic diabetic ulcers. This review examines the work done at the molecular level on chronic diabetic ulcers, as well as considering changes seen in diabetes in general, both in humans and animal models, that may in turn contribute to ulcer formation.

Anin VitroApproach to the Chronological Aging of Skin by Glycation of the Collagen: The Biological Effect of Glycation on the Reconstructed Skin Model

Glycation is a slow, nonenzymatic reaction that takes place between free amino groups in proteins primarily from lysine and a reducing sugar such as glucose or ribose. In skin, this reaction creates new residues or formations of cross-links (advanced glycation end products, AGEs) in the extracellular matrix of the dermis. The formation of these bridges between dermal molecules is supposed to be responsible for loss of elasticity or other properties of the dermis observed during aging. Glycation may therefore play an important role in chronologic aging. In order to examine this hypothesis, we have developed a reconstructed skin model made of a modified dermal compartment that is a fibroblast-contracted collagen lattice prepared with preglycated collagen. The presence of AGEs (glycoxidation products) in the skin equivalents was evidenced using specific antibodies against carboxymethyllysine (CML). Several changes were observed after collagen glycation: (1) fibroblast shape and distribution (vimentin staining) were modified; (2) extracellular matrix molecules and the dermal-epidermal junction zone seemed to be enhanced (procollagen I and III, collagen IV and VII stainings); (3) stainings for beta1 and alpha6 integrins were also increased in the epidermal cell layer; and (4) collagenase activity was increased. To verify the biological effect of glycation, we used the well-known glycation inhibitor aminoguanidine. After aminoguanidine treatment, we found a low CML amount and decreased distribution of markers previously overexpressed in glycated skin constructs. These in vitro findings were at least in part related to aging in vivo and demonstrate an actual effect of glycation in skin aging.

What role do extracellular matrix changes contribute to the cardiovascular disease burden of diabetes mellitus?

Matrix metalloproteinases (MMP) and their inhibitors (TIMP) are central factors in the control of extracellular matrix turnover. They are important in normal physiology and also during a range of pathological states. In this review, we have systematically identified clinical articles relevant to cardiovascular disease in diabetes from the last 10 years. Our aim was to outline the structure, function and regulation of metalloproteinases and their key roles in cardiomyopathy and vasculopathy in diabetes. We also explore the effects of drug intervention on both human subjects with diabetes and experimental animal models. The modulation of MMP and TIMP activity using drugs that affect the expression and function of these proteins may provide us with new ways to treat this serious and disabling disease, and we explore potential mechanisms and treatments.

A mechanical model for collagen fibril load sharing in peripheral nerve of diabetic and nondiabetic rats

Peripheral neuropathy affects approximately 50% of the 15 million Americans with diabetes. It has been suggested that mechanical effects related to collagen glycation are related to the permanence of neuropathy. In the present paper, we develop a model for load transfer in a whole nerve, using a simple pressure vessel approximation, in order to assess the significant of stiffening of the collagenous nerve sheath on endoneurial fluid pressure. We also develop a fibril-scale mechanics model for the nerve, to model the straightening of wavy fibrils, producing the toe region observed in nerve tissue, and also to interrogate the effects of interfibrillar crosslinks on the overall properties of the tissue. Such collagen crosslinking has been implicated in complications in diabetic tissues. Our fibril-scale model uses a two-parameter Weibull model for fibril strength, in combination with statistical parameters describing fibril modulus, angle, wave-amplitude, and volume fraction to capture both toe region and failure region behavior of whole rat sciatic nerve. The extrema of equal and local load-sharing assumptions are used to map potential differences in diabetic and nondiabetic tissues. This work may ultimately be useful in differentiating between the responses of normal and heavily crosslinked tissue.

Changes in mechanical properties and cellularity during long-term culture of collagen fiber ACL reconstruction scaffolds

Resorbable scaffolds for anterior cruciate ligament (ACL) reconstruction should provide temporary mechanical function then gradually breakdown while promoting matrix synthesis by local cells. Crosslinking influences collagen's mechanical properties, degradation rate, and interactions with cells. Our objective was to compare the effects of different crosslinkers on cellularity and mechanical properties during long-term (8 week) culture of collagen fiber scaffolds. Fibers were fabricated from an acid-insoluble dispersion of bovine dermal collagen and crosslinked with either ultraviolet irradiation (UV; a physical crosslinker) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC; a chemical crosslinker). Scaffolds consisted of 50 fibers bundled in parallel. Initial attachment of fibroblasts was similar on both scaffolds; however, from 1 to 8 weeks in culture, UV-crosslinked scaffolds had significantly more cells attached than EDC-crosslinked scaffolds. The initial breaking load (3.50 N) and stiffness (2.23 N/mm) of EDC-crosslinked scaffolds were significantly greater than those of UV-crosslinked scaffolds (2.32 N; 1.21 N/mm) and were unaffected by long-term fibroblast culture. In contrast, the load-bearing capacity of fibroblast-seeded UV-crosslinked scaffolds decreased 60% to 0.91 N after 8 weeks in culture. EDC-crosslinked scaffolds maintained strength and moderate cellularity; UV-crosslinked scaffolds, in contrast, were highly cellular, but had poor mechanical properties that decreased during culture. These in vitro results suggest that collagen fiber scaffolds crosslinked with EDC may be more suitable for ACL reconstruction than those crosslinked with UV.

In vitro effects of oxytetracycline on matrix metalloproteinase-1 mRNA expression and on collagen gel contraction by cultured myofibroblasts obtained from the accessory ligament of foals

OBJECTIVE

To determine the effects of oxytetracycline on matrix metalloproteinase-1 (MMP-1) mRNA expression and collagen gel contraction by equine myofibroblasts in an effort to explain the mechanistic basis for the pharmacologic treatment of flexural deformities in foals.

SAMPLE POPULATION

Cultured myofibroblasts from the accessory ligament (distal check ligament) of 6 foals.

PROCEDURE

Collagen gel scaffolds seeded with equine myofibroblasts were cultured in individual culture dishes containing complete media (Dulbecco's modified Eagle medium with 10% fetal bovine serum) and oxytetracycline (0, 12.5, 25, or 75 microg/mL) for 48 hours. After 24 hours, the gels were released from the bottom of the culture plate and allowed to contract. Photographs were taken at 0, 1, 2, 4, 6, 8, and 24 hours after release to assess the degree of collagen gel contraction. Additional gels were harvested at 2 hours after release for RNA isolation and reverse transcriptase-polymerase chain reaction assessment of the degree of MMP-1 mRNA expression.

RESULTS

Oxytetracycline induced a dose-dependent inhibition of collagen gel contraction by equine myofibroblasts. Oxytetracycline also induced a dose-dependent decrease in MMP-1 mRNA expression by equine myofibroblasts.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study indicate that oxytetracycline inhibits tractional structuring of collagen fibrils by equine myofibroblasts through an MMP-1 mediated mechanism. In young foals, oxytetracycline administration may make the developing ligaments and tendons more susceptible to elongation during normal weight-bearing. Inhibition of normal collagen organization may provide the mechanistic explanation for the results seen following the pharmacologic treatment of flexural deformities in foals by oxytetracycline administration.

Enhanced activation of and increased production of matrix metalloproteinase-9 by human blood monocytes upon adhering to carbamylated collagen

Carbamylation refers to chemical modification of protein side chains by cyanate derived e.g. from urea. It alters their structural and functional properties. We have studied the influence of the carbamylation of type I collagen in vitro on its interactions with elutriated human monocytes, and its potential role in atherosclerosis. Adhesion of monocytes onto carbamylated collagen was significantly enhanced compared to native collagen. There was no change in superoxide anion production. On the other hand, there was an increase in the production and the activation of matrix metalloproteinase-9. No effect was found on tissue inhibitor of metalloproteinase-1 production. Thus, the presence of carbamylated collagen may stimulate the remodelling of extracellular matrix mediated by activated monocytes. Such alterations may contribute to enhanced atherosclerosis in renal insufficiency, a pathological condition associated with elevated levels of carbamylation.

Prolonged spinal loading induces matrix metalloproteinase-2 activation in intervertebral discs

STUDY DESIGN

An established in vivo mouse model of compression-induced disc degeneration was used to investigate the effects of load on matrix catabolism.

OBJECTIVES

To determine whether matrix metalloproteinase-2 expression in discs is modulated by mechanical load and to characterize the regulation of matrix metalloproteinase-2 activity.

SUMMARY OF BACKGROUND DATA

We have previously shown that static compression of discs elicits changes in tissue architecture consistent with those seen with degeneration. Evidence in the literature demonstrates the existence of matrix metalloproteinases in both healthy and pathologic discs and suggests that mechanical load may influence matrix metalloproteinase expression and activity.

METHODS

Static compression was applied to mouse coccygeal discs in vivo for 1, 4, or 7 days, with adjacent discs serving as sham control. An activity assay was used to measure concentrations of active and total matrix metalloproteinase-2, and changes in matrix metalloproteinase-2 gene expression relative to beta-actin were assessed by reverse transcriptase-polymerase chain reaction.

RESULTS

Although no change was seen relative to sham after 1 day of load, the proportion of total matrix metalloproteinase-2 that was active increased after 4 days. This elevation was sustained through 7 days of compression, with no significant differences in total matrix metalloproteinase-2 concentrations among discs throughout the range of time points examined. Semiquantitative reverse transcriptase-polymerase chain reaction demonstrated no significant changes in matrix metalloproteinase-2 gene expression at 1 day or 4 days.

CONCLUSIONS

In this model, regulation of matrix metalloproteinase-2 activity occurs primarily through enhanced molecular activation of the proenzyme rather than through elevated gene expression or translation. Our results suggest that matrix metalloproteinase-2 may have a role in load-induced changes in disc architecture.

Effects of mesangium glycation on matrix metalloproteinase activities: possible role in diabetic nephropathy

High glucose concentrations can decrease degradation of mesangium by reducing the activities of matrix metalloproteinases (MMPs). The aim of this study was to investigate the effects of glycation of mesangium matrix on MMP-2, the principal MMP secreted by mesangial cells to degrade type IV collagen. Also examined were membrane type 1 MMP (MT1-MMP), tissue inhibitors of MMPs (TIMP)-1 and -2, and transforming growth factor-beta (TGF-beta), which together regulate MMP-2 activities in an interacting manner. Human fetal mesangial cells were grown on mesangium matrix glycated by incubation in 500 mmol/l ribose, with or without aminoguanidine. The activities and gene expression of the abovementioned enzymes/inhibitors were measured by degradation of radiolabeled mesangium matrix, RT-PCR, and zymography. Glycation of mesangium matrix resulted in a threefold increase in advance glycation end products and reduced by 45% the matrix-degrading activity of MMPs secreted by mesangial cells. Analogous to the direct effects of high glucose concentrations, glycation of matrix increased the gene expression of MMP-2 and TIMP-1 (control 100 +/- 16.9 vs. glycated 197.3 +/- 30.6% and control 100 +/- 5.3 vs. glycated 152.1 +/- 20.1%, respectively; P < 0.05) and decreased MT1-MMP (control 100 +/- 1.17 vs. glycated 54.1 +/- 15.2%; P < 0.05). However, unlike high glucose concentrations, glycation was not associated with decreased activation of MMP-2. Similarly, glycation but not high glucose increased expression of TIMP-2 (control 100 +/- 5.9 vs. glycated 168.2 +/- 31.4%; P < 0.05), and the effects of glycation on degradation can be abolished by anti-TIMP-2 antibody. Glycation of matrix decreased TGF-beta mRNA by 38.2% and total and active TGF-beta by 35.5 and 21.5%, respectively, opposite the effects of high glucose concentrations. Our results indicate that glycation of matrix affects the balance between MMP-2 and its activator and inhibitors, but this phenomenon is not due to TGF-beta. The process of glycation may impart to the mesangium matrix a memory effect that contributes to the long-term toxicity of hyperglycemia.

Photosensitized growth inhibition of cultured human skin cells: mechanism and suppression of oxidative stress from solar irradiation of glycated proteins

Chronic exposure to sunlight plays a role in skin aging and carcinogenesis. The molecular mechanisms of photodamage by ultraviolet A, the sunlight's major ultraviolet constituent, are poorly understood. Here we provide evidence that advanced glycation end products on proteins are sensitizers of photo-oxidative stress in skin cells. Glycation is a process of protein damage by reducing sugars and other reactive carbonyl species leading to the formation of advanced glycation end products, which accumulate on long-lived proteins such as dermal elastin and collagen during skin aging. Growth inhibition as a result of advanced glycation end product photosensitization of ultraviolet A and solar-simulated light was demonstrated in human keratinocytes and fibroblasts. Using advanced glycation end product bovine serum albumin and advanced glycation end product collagen as model photosensitizers, ultraviolet A-induced formation of H2O2 was identified as the key mediator of skin cell growth inhibition as evidenced by complete protection by catalase treatment and equivalent growth inhibition of unirradiated cells treated with pre-irradiated advanced glycation end product protein. D-penicillamine protected against advanced glycation end product-photosensitized growth inhibition even when added following irradiation, suggesting the feasibility of therapeutic approaches for protection against skin ultraviolet A damage. Photosensitized growth inhibition increased with the degree of advanced glycation end product modification paralleled by the amount of H2O2 formed upon solar-simulated light irradiation of the protein. Photosensitization was not observed using bovine serum albumin modified with the major advanced glycation end product, Nepsilon-carboxymethyl-L-lysine, ruling out effects of cellular advanced glycation end product receptor (RAGE) stimulation. In contrast to bovine serum albumin, unglycated collagen showed photosensitization in CF3 fibroblasts and generation of H2O2 upon solar-simulated light irradiation. This study supports the hypothesis that advanced glycation end product-modified proteins are endogenous sensitizers of photo-oxidative cell damage in human skin by ultraviolet A-induced generation of reactive oxygen species contributing to photoaging and photocarcinogenesis.

Matrix-directed regulation of pericellular proteolysis and tumor progression

The microenvironment of cancer cells, composed of extracellular matrix (ECM) macromolecules, plays a pivotal function in tumor progression. ECM preexisting modules or cryptic sites revealed by partial enzymatic hydrolysis positively or negatively regulate matrix metalloproteinase (MMP) expression and activation, further influencing matrix invasion by cancer cells. Pericellular activation of gelatinase A (MMP-2) proceeds via the formation of a complex involving its inhibitor, TIMP-2, its activator(s), MT-MMPs and alphavbeta3 integrin forming a docking system. This proteinase has been invariably linked to cancer cell invasive potential and is often predictive of a poor survival. MMP-2 degrades most ECM macromolecules and appears to act as a main 'decryptase'. ECM modulation of MMP-2 activation pathway thus influences angiogenesis and tumor growth. For instance the noncollagenous domain of alpha3 chain of type IV collagen, through alphavbeta3 integrin binding, inhibits both MT1-MMP and alphavbeta3 integrin expression from melanoma cells and empedes cell migration and proliferation. At the opposite, a particular module in elastin (VGVAPG) with type VIII beta turn conformation stimulates MT1-MMP and proMMP-2 activation through binding to S-gal elastin receptor, and increases the matrix invasive capacity of several cancer cell lines and endothelial cells. Endocytosis emerges as a main mechanism controlling MMP-2, and also other MMPs; it proceeds via the formation of a MMP-thrombospondin(s) complex further recognized by the LRP scavenger receptor. ECM undergoes conspicuous variations with aging linked to alterations of tissue organization and post-translational modifications of matrix constituents that modify cell-matrix interactions and MMP-2 activation pathway.

Malondialdehyde binding to proteins dramatically alters fibroblast functions

The regulation of cell metabolism by the surrounding environment is deeply altered by the posttranslational nonenzymatic modifications of extracellular proteins that occur throughout lifespan in vivo and modify their structural and functional properties. Among them are protein adducts formed by components generated from oxidative processes, such as malondialdehyde (MDA). We have investigated here the effects of MDA-binding to proteins on cultured fibroblast functions. Type I collagen and/or serum proteins were incubated with 0-100 mM MDA for 3 h before use in fibroblast cultures. In tridimensional lattice cultures, MDA-treated collagen inhibited the contracting activity of fibroblasts. A similar inhibition of lattice contraction was reproduced by the addition of MDA-treated serum to the culture medium. In monolayer cultures, the addition of MDA-modified serum proteins completely inhibited fibroblast multiplication without effect on initial adhesion steps. MDA-modified proteins decreased the proliferative capacities of cells, strongly altered cell cycle progression by blocking passage to G2/M phases, and induced apoptotic features in fibroblasts. Our results show, for the first time, that MDA-modified proteins are potentially as deleterious as free MDA, and could be involved in aging as well as in degenerative complications of diseases with increased oxidative stress such as diabetes mellitus or atherosclerosis.

Modulation of collagen metabolism by the nucleolar protein fibrillarin

Metabolic functions of fibroblasts are tightly regulated by the extracellular environment. When cultivated in tridimensional collagen lattices, fibroblasts exhibit a lowered activity of protein synthesis, especially concerning extracellular matrix proteins. We have previously shown that extracellular collagen impaired the processing of ribosomal RNA (rRNA) in nucleoli by generating changes in the expression of nucleolar proteins and a premature degradation of neosynthesized rRNA. In this study, we have investigated whether inhibiting the synthesis of fibrillarin, a major nucleolar protein with decreased expression in collagen lattices, could mimic the effects of extracellular matrix. Monolayer-cultured fibroblasts were transfected with anti-fibrillarin antisense oligodeoxynucleotides, which significantly decreased fibrillarin content. Downregulation of fibrillarin expression inhibited procollagen secretion into the extracellular medium, without altering total collagen production. No changes of pro1(I)collagen mRNA expression or proline hydroxylation were found. A concomitant intracellular retention of collagen and its chaperone protein HSP47 was found, but no effect on the production of other extracellular matrix macromolecules or remodelling enzymes was observed. These data show that collagen processing depends on unknown mechanisms, involving proteins primarily located in the nucleolar compartment with other demonstrated functions, and suggest specific links between nucleolar machinery and extracellular matrix.

Accumulation of advanced glycation end products decreases collagen turnover by bovine chondrocytes

The integrity of the collagen network is essential for articular cartilage to fulfill its function in load support and distribution. Damage to the collagen network is one of the first characteristics of osteoarthritis. Since extensive collagen damage is considered irreversible, it is crucial that chondrocytes maintain a functional collagen network. We investigated the effects of advanced glycation end products (AGEs) on the turnover of collagen by articular cartilage chondrocytes. Increased AGE levels (by culturing in the presence of ribose) resulted in decreased collagen synthesis (P < 0.05) and decreased MMP-mediated collagen degradation (P < 0.02). The latter could be attributed to increased resistance of the collagen network to MMPs (P < 0.05) as well as the decreased production of MMPs by chondrocytes (P < 0.02). Turnover of a protein is determined by its synthesis and degradation rates and therefore these data indicate that collagen turnover is decreased at enhanced AGE levels. Since AGE levels in human cartilage increase approximately 50 fold between age 20 and 80, cartilage collagen turnover likely decreases with increasing age. Impaired collagen turnover adversely affects the capacity of chondrocytes to remodel and/or repair its extracellular matrix. Consequently, age-related accumulation of AGE (via decreased collagen turnover) may contribute to the development of cartilage damage in osteoarthritis.