Covalent crosslinking between molecules of type I and type III collagen. The involvement of the N-terminal, nonhelical regions of the alpha 1 (I) and alpha 1 (III) chains in the formation of intermolecular crosslinks

Gelatin/heparin coated bio-inspired polyurethane composite fibers to construct small-caliber artificial blood vessel grafts

Long-term patency and ability for revascularization remain challenges for small-caliber blood vessel grafts to treat cardiovascular diseases clinically. Here, a gelatin/heparin coated bio-inspired polyurethane composite fibers-based artificial blood vessel with continuous release of NO and biopeptides to regulate vascular tissue repair and maintain long-term patency is fabricated. A biodegradable polyurethane elastomer that can catalyze S-nitrosothiols in the blood to release NO is synthesized (NPU). Then, the NPU core-shell structured nanofiber grafts with requisite mechanical properties and biopeptide release for inflammation manipulation are fabricated by electrospinning and lyophilization. Finally, the surface of tubular NPU nanofiber grafts is coated with heparin/gelatin and crosslinked with glutaraldehyde to obtain small-caliber artificial blood vessels (ABVs) with the ability of vascular revascularization. We demonstrate that artificial blood vessel grafts promote the growth of endothelial cells but inhibit the growth of smooth muscle cells by the continuous release of NO; vascular grafts can regulate inflammatory balance for vascular tissue remodel without excessive collagen deposition through the release of biological peptides. Vascular grafts prevent thrombus and vascular stenosis to obtain long-term patency. Hence, our work paves a new way to develop small-caliber artificial blood vessel grafts that can maintain long-term patency in vivo and remodel vascular tissue successfully.

Role of Collagen in the Etiology of Inguinal Hernia Patients: A Case-Control Study

Introduction Technical faults are no longer accepted as the sole reason for recurrence following inguinal hernia (InH) repairs. Medical literature has been studied to find any contributing factors and collagen has emerged as a promising marker. Owing to their long half-lives, it has been found to best reflect the process of scarring, which is central to ensuring the formation of a proper fibrous tissue that incorporates the mesh with the abdominal wall. Methods Sixty participants were divided into two groups. The case group were patients diagnosed with InH and the control group had patients undergoing abdominal surgeries for indications other than abdominal wall hernias. A 0.5x0.5cm specimen of skin and transversalis fascia were biopsied and subsequently stained to determine the amount of collagen I and III. Results Collagen I, collagen III and the ratio of collagen I to III was measured. Collagen I was normal in the skin of both groups but decreased in transversalis fascia of cases. Collagen III was found to be normal in transversalis fascia of both cases and controls, but increased in the skin of cases. Ratio of collagen I to III was decreased in both skin and transversalis fascia of cases. Statistical analysis was carried out using an unpaired t-test, non-parametric Mann-Whitney test, ANOVA and chi-square test. Conclusions Our study has reported that in patients with inguinal hernia, collagen III or immature collagen is increased in skin and collagen I or mature collagen is decreased in the transversalis fascia. The ratio of collagen I/III is decreased in both skin and transversalis fascia.

SVCT2-GLUT1-mediated ascorbic acid transport pathway in rat dental pulp and its effects during wound healing

Ascorbic acid (AA; vitamin C) plays a crucial role in the biosynthesis and secretion of collagen to produce the organic matrix of hard tissues. Nevertheless, the detailed mechanism by which AA induces reparative dentinogenesis is still unknown. This study aimed to investigate the pathway and function of AA during wound healing in a rat pulpotomy model. Sodium-dependent vitamin C transporter (SVCT) 2 and glucose transporter (GLUT) 1 were detected in odontoblasts, endothelial cells, and nerve fibers in normal pulp tissues. SVCT2 and GLUT1 were also expressed in odontoblast-like cells in pulpotomized tissues of Wistar rats, and immunopositive cells of SVCT2 were significantly increased at 5 days after pulpotomy (p < 0.05). By contrast, osteogenic disorder Shionogi (ODS) rats, which cannot generate AA, also expressed SVCT2 and GLUT1 in normal and wound healing conditions. However, in ODS rats, when compared with the AA-addition group, the formation of dentin bridges in the AA-loss group was not evident, a layer of osteopontin was significantly increased beneath the wound surface (p < 0.05), and alpha smooth muscle actin at the odontoblast-like cells observed along this layer was significantly increased (p < 0.05), but not Nestin. Moreover, the amounts of type 1 collagen generated in the reparative dentin and beneath the wound healing site were significantly diminished (p < 0.05). Macrophages expressing CD68 and CD206 increased beneath the wound site. Hence, AA may be involved in odontoblast-like cell differentiation and anti-inflammatory response during dental pulp wound healing. Our results provide new insights into the function of AA through SVCT2 and GLUT1 in reparative dentinogenesis and may help in developing new therapeutic targets for dental pulpal disease.

Age-related changes in the ratio of Type I/III collagen and fibril diameter in mouse skin

The content of type I collagen (COL-I) and type III collagen (COL-III) and the ratio between them not only affect the skin elasticity and mechanical strength, but also determine the fibril diameter. In this research, we investigated the age-related changes in COL-I/COL-III ratio with their formed fibril diameter. The experimental result was obtained from high performance liquid chromatography-mass spectrometer, hydroxyproline determination, picrosirius red staining and transmission electron microscopes (TEM), respectively. The result indicated that the COL-I/COL-III ratio in mouse skin increased with aging. From the 0th to 9th week, the COL-I/COLIII ratio increased from 1.3:1 to 4.5:1. From the 9th to the 18th week, it remained between 4.5:1 and 4.9:1. The total content of COL-I and COL-III firstly increased and then decreased with aging. The TEM result showed that the fibril diameter increased with aging. From the 0th to 9th week, the average fibril diameter increased from 40 to 112 nm; From the 9th to 18th weeks, it increased from 112 to 140 nm. After the 9th week. The fibril diameter showed obvious uneven distribution. Thus, the COL-I/COLIII ratio was proportional to the fibril diameter, but inversely proportional to the uniformity of fibril diameter.

Advancements in Extracellular Matrix-Based Biomaterials and Biofabrication of 3D Organotypic Skin Models

Over the last decades, three-dimensional (3D) organotypic skin models have received enormous attention as alternative models to in vivo animal models and in vitro two-dimensional assays. To date, most organotypic skin models have an epidermal layer of keratinocytes and a dermal layer of fibroblasts embedded in an extracellular matrix (ECM)-based biomaterial. The ECM provides mechanical support and biochemical signals to the cells. Without advancements in ECM-based biomaterials and biofabrication technologies, it would have been impossible to create organotypic skin models that mimic native human skin. In this review, the use of ECM-based biomaterials in the reconstruction of skin models, as well as the study of complete ECM-based biomaterials, such as fibroblasts-derived ECM and decellularized ECM as a better biomaterial, will be highlighted. We also discuss the benefits and drawbacks of several biofabrication processes used in the fabrication of ECM-based biomaterials, such as conventional static culture, electrospinning, 3D bioprinting, and skin-on-a-chip. Advancements and future possibilities in modifying ECM-based biomaterials to recreate disease-like skin models will also be highlighted, given the importance of organotypic skin models in disease modeling. Overall, this review provides an overview of the present variety of ECM-based biomaterials and biofabrication technologies available. An enhanced organotypic skin model is expected to be produced in the near future by combining knowledge from previous experiences and current research.

Tendon Extracellular Matrix Assembly, Maintenance and Dysregulation Throughout Life

In his Lissner Award medal lecture in 2000, Stephen Cowin asked the question: "How is a tissue built?" It is not a new question, but it remains as relevant today as it did when it was asked 20 years ago. In fact, research on the organization and development of tissue structure has been a primary focus of tendon and ligament research for over two centuries. The tendon extracellular matrix (ECM) is critical to overall tissue function; it gives the tissue its unique mechanical properties, exhibiting complex non-linear responses, viscoelasticity and flow mechanisms, excellent energy storage and fatigue resistance. This matrix also creates a unique microenvironment for resident cells, allowing cells to maintain their phenotype and translate mechanical and chemical signals into biological responses. Importantly, this architecture is constantly remodeled by local cell populations in response to changing biochemical (systemic and local disease or injury) and mechanical (exercise, disuse, and overuse) stimuli. Here, we review the current understanding of matrix remodeling throughout life, focusing on formation and assembly during the postnatal period, maintenance and homeostasis during adulthood, and changes to homeostasis in natural aging. We also discuss advances in model systems and novel tools for studying collagen and non-collagenous matrix remodeling throughout life, and finally conclude by identifying key questions that have yet to be answered.

Distinct phenotypes of cancer cells on tissue matrix gel

BACKGROUND

Breast cancer cells invading the connective tissues outside the mammary lobule or duct immerse in a reservoir of extracellular matrix (ECM) that is structurally and biochemically distinct from that of their site of origin. The ECM is a spatial network of matrix proteins, which not only provide physical support but also serve as bioactive ligands to the cells. It becomes evident that the dimensional, mechanical, structural, and biochemical properties of ECM are all essential mediators of many cellular functions. To better understand breast cancer development and cancer cell biology in native tissue environment, various tissue-mimicking culture models such as hydrogel have been developed. Collagen I (Col I) and Matrigel are the most common hydrogels used in cancer research and have opened opportunities for addressing biological questions beyond the two-dimensional (2D) cell cultures. Yet, it remains unclear whether these broadly used hydrogels can recapitulate the environmental properties of tissue ECM, and whether breast cancer cells grown on CoI I or Matrigel display similar phenotypes as they would on their native ECM.

METHODS

We investigated mammary epithelial cell phenotypes and metabolic profiles on animal breast ECM-derived tissue matrix gel (TMG), Col I, and Matrigel. Atomic force microscopy (AFM), fluorescence microscopy, acini formation assay, differentiation experiments, spatial migration/invasion assays, proliferation assay, and nuclear magnetic resonance (NMR) spectroscopy were used to examine biological phenotypes and metabolic changes. Student's t test was applied for statistical analyses.

RESULTS

Our data showed that under a similar physiological stiffness, the three types of hydrogels exhibited distinct microstructures. Breast cancer cells grown on TMG displayed quite different morphologies, surface receptor expression, differentiation status, migration and invasion, and metabolic profiles compared to those cultured on Col I and Matrigel. Depleting lactate produced by glycolytic metabolism of cancer cells abolished the cell proliferation promoted by the non-tissue-specific hydrogel.

CONCLUSION

The full ECM protein-based hydrogel system may serve as a biologically relevant model system to study tissue- and disease-specific pathological questions. This work provides insights into tissue matrix regulation of cancer cell biomarker expression and identification of novel therapeutic targets for the treatment of human cancers based on tissue-specific disease modeling.

Collagen turnover profiles in chronic kidney disease

Renal fibrosis is a hallmark of chronic kidney disease (CKD) caused by an imbalance between formation and degradation of extracellular matrix proteins. We investigated the collagen turnover profile of 81 non-dialysis CKD stage 2-5 patients by measuring peptides reflecting formation and degradation of collagen type (COL) I, III, IV, and VI. Based on the collagen turnover profile, we identified four clusters of patients. Cluster 1 contained one patient with prostate cancer, who had a distinct collagen turnover. The other clusters generally had severe (Cluster 2), moderate (Cluster 4), or mild CKD (Cluster 3). Cluster 4 patients were characterized by higher levels of COL III, COL IV, and COL VI (all p < 0.001) degradation fragments in plasma, while patients in Clusters 2 and 4 had higher levels of COL VI formation (p < 0.05). COL IV fragments in plasma were lower in Cluster 2 (p < 0.01). Urinary COL III fragments decreased from Cluster 3 to 4, and from Cluster 4 to 2 (both p < 0.001). We show that patients with similar kidney function have a different collagen remodeling profile, suggesting that different phenotypes exist with different disease activity and potentially disease progression. Biomarkers of collagen remodeling could provide additional information to traditional markers of renal function.

Type III collagen is a key regulator of the collagen fibrillar structure and biomechanics of articular cartilage and meniscus

Despite the fact that type III collagen is the second most abundant collagen type in the body, its contribution to the physiologic maintenance and repair of skeletal tissues remains poorly understood. This study queried the role of type III collagen in the structure and biomechanical functions of two structurally distinctive tissues in the knee joint, type II collagen-rich articular cartilage and type I collagen-dominated meniscus. Integrating outcomes from atomic force microscopy-based nanomechanical tests, collagen fibril nanostructural analysis, collagen cross-link analysis and histology, we elucidated the impact of type III collagen haplodeficiency on the morphology, nanostructure and biomechanical properties of articular cartilage and meniscus in Col3a1^+/- mice. Reduction of type III collagen leads to increased heterogeneity and mean thickness of collagen fibril diameter, as well as reduced modulus in both tissues, and these effects became more pronounced with skeletal maturation. These data suggest a crucial role of type III collagen in mediating fibril assembly and biomechanical functions of both articular cartilage and meniscus during post-natal growth. In articular cartilage, type III collagen has a marked contribution to the micromechanics of the pericellular matrix, indicating a potential role in mediating the early stage of type II collagen fibrillogenesis and chondrocyte mechanotransduction. In both tissues, reduction of type III collagen leads to decrease in tissue modulus despite the increase in collagen cross-linking. This suggests that the disruption of matrix structure due to type III collagen deficiency outweighs the stiffening of collagen fibrils by increased cross-linking, leading to a net negative impact on tissue modulus. Collectively, this study is the first to highlight the crucial structural role of type III collagen in both articular cartilage and meniscus extracellular matrices. We expect these results to expand our understanding of type III collagen across various tissue types, and to uncover critical molecular components of the microniche for regenerative strategies targeting articular cartilage and meniscus repair.

Differential Effect of Cobalt and Chromium Ions as Well as CoCr Particles on the Expression of Osteogenic Markers and Osteoblast Function

The balance of bone formation and resorption is the result of a regulated crosstalk between osteoblasts, osteoclasts, and osteocytes. Inflammation, mechanical load, and external stimuli modulate this system. Exposure of bone cells to metal ions or wear particles are thought to cause osteolysis via activation of osteoclasts and inhibition of osteoblast activity. Co²⁺ ions have been shown to impair osteoblast function and the expression of the three transforming growth factor (TGF)-β isoforms. The current study was performed to analyze how Co²⁺ and Cr³⁺ influence the expression, proliferation, and migration profile of osteoblast-like cells. The influence of Co²⁺, Cr³⁺, and CoCr particles on gene expression was analyzed using an osteogenesis PCR Array. The expression of different members of the TGF-β signaling cascade were down-regulated by Co²⁺, as well as several TGF-β regulated collagens, however, Cr³⁺ had no effect. CoCr particles partially affected similar genes as the Co²⁺treatment. Total collagen production of Co²⁺ treated osteoblasts was reduced, which can be explained by the reduced expression levels of various collagens. While proliferation of MG63 cells appears unaffected by Co²⁺, the migration capacity was impaired. Our data may improve the knowledge of changes in gene expression patterns, and the proliferation and migration effects caused by artificial materials.

Induction of human umbilical cord mesenchymal stem cells into tissue-forming cells in a murine model: implications for pelvic floor reconstruction

HUMSCs were isolated, differentiated and characterized in vitro. Both HUMSCs and smooth muscle cells differentiated from HUMSCs were used to fabricate tissue-engineered fascia equivalents. Forty-eight mature female Sprague Dawley rats were randomly assigned to four groups: group A (GynemeshTMPS, n = 12), group B (GynemeshTMPS + HUMSCs; n = 12), group C (GynemeshTMPS + smooth muscle cells differentiated from HUMSCs; n = 12) and group D (GynemeshTMPS + HUMSCs + smooth muscle cells differentiated from HUMSCs; n = 12). The posterior vaginal wall was incised from the introitus and the mesh was then implanted. Three implants of each type were tested at 1, 4, 8 and 12 weeks. Fibrotic remodeling, inflammation, vascularization and tissue regeneration were histologically assessed. The levels of type I and type III collagen were determined. There was no difference in fibrotic remodeling between cell-seeded and unseeded meshes at any time (p > 0.05). At 12 weeks, there did not appear to be fewer inflammatory cells around the filament bundles in the mesh with cells compared with the mesh alone (P > 0.05). Group D showed a trend toward better vascularization at 12 weeks compared with group A (P < 0.05). Twelve weeks after implantation, a thin layer of new tissue growth covered the unseeded scaffold and a thicker layer covered the cell-seeded scaffold (P < 0.05). No significant difference in the ratio of collagen type I/III could be detected among the different groups after 12 weeks (P > 0.05). HUMSCs with differentiated smooth muscle cells might have a potential role in fascia tissue engineering to repair POP in the future.

Etiology of Inguinal Hernias: A Comprehensive Review

Background

The etiology of inguinal hernias remains uncertain even though the lifetime risk of developing an inguinal hernia is 27% for men and 3% for women. The aim was to summarize the evidence on hernia etiology, with focus on differences between lateral and medial hernias.

Results

Lateral and medial hernias seem to have common as well as different etiologies. A patent processus vaginalis and increased cumulative mechanical exposure are risk factors for lateral hernias. Patients with medial hernias seem to have a more profoundly altered connective tissue architecture and homeostasis compared with patients with lateral hernias. However, connective tissue alteration may play a role in development of both subtypes. Inguinal hernias have a hereditary component with a complex inheritance pattern, and inguinal hernia susceptible genes have been identified that also are involved in connective tissue homeostasis.

Conclusion

The etiology of lateral and medial hernias are at least partly different, but the final explanations are still lacking on certain areas. Further investigations of inguinal hernia genes may explain the altered connective tissue observed in patients with inguinal hernias. The precise mechanisms why processus vaginalis fails to obliterate in certain patients should also be clarified. Not all patients with a patent processus vaginalis develop a lateral hernia, but increased intraabdominal pressure appears to be a contributing factor.

The collαgen III fibril has a "flexi-rod" structure of flexible sequences interspersed with rigid bioactive domains including two with hemostatic roles

Collagen III is critical to the integrity of blood vessels and distensible organs, and in hemostasis. Examination of the human collagen III interactome reveals a nearly identical structural arrangement and charge distribution pattern as for collagen I, with cell interaction domains, fibrillogenesis and enzyme cleavage domains, several major ligand-binding regions, and intermolecular crosslink sites at the same sites. These similarities allow heterotypic fibril formation with, and substitution by, collagen I in embryonic development and wound healing. The collagen III fibril assumes a "flexi-rod" structure with flexible zones interspersed with rod-like domains, which is consistent with the molecule's prominence in young, pliable tissues and distensible organs. Collagen III has two major hemostasis domains, with binding motifs for von Willebrand factor, α2β1 integrin, platelet binding octapeptide and glycoprotein VI, consistent with the bleeding tendency observed with COL3A1 disease-causing sequence variants.

Vesicoureteral reflux and the extracellular matrix connection

Primary vesicoureteral reflux (VUR) is a common pediatric condition due to a developmental defect in the ureterovesical junction. The prevalence of VUR among individuals with connective tissue disorders, as well as the importance of the ureter and bladder wall musculature for the anti-reflux mechanism, suggest that defects in the extracellular matrix (ECM) within the ureterovesical junction may result in VUR. This review will discuss the function of the smooth muscle and its supporting ECM microenvironment with respect to VUR, and explore the association of VUR with mutations in ECM-related genes.

Rapid and Accurate Identification of Animal Species in Natural Leather Goods by Liquid Chromatography/Mass Spectrometry

The demand for leather goods has grown globally in recent years. Industry revenue is forecast to reach $91.2 billion by 2018. There is an ongoing labelling problem in the leather items market, in that it is currently impossible to identify the species that a given piece of leather is derived from. To address this issue, we developed a rapid and simple method for the specific identification of leather derived from cattle, horses, pigs, sheep, goats, and deer by analysing peptides produced by the trypsin-digestion of proteins contained in leather goods using liquid chromatography/mass spectrometry. We determined species-specific amino acid sequences by liquid chromatography/tandem mass spectrometry analysis using the Mascot software program and demonstrated that collagen α-1(I), collagen α-2(I), and collagen α-1(III) from the dermal layer of the skin are particularly useful in species identification.

Identifying distinct nanoscopic features of native collagen fibrils towards early diagnosis of pelvic organ prolapse

Pelvic organ prolapse (POP) is characterized by weakening of the connective tissues and loss of support for the pelvic organs. Collagen is the predominant, load-bearing protein within pelvic floor connective tissues. In this study, we examined the nanoscopic structures and biomechanics of native collagen fibrils in surgical, vaginal wall connective tissues from healthy women and POP patients. Compared to controls, collagen fibrils in POP samples were bulkier, more uneven in width and stiffer with aberrant D-period. Additionally, the ratio of collagen I (COLI) and collagen III (COLIII) is doubled in POP with a concomitant reduction of the amount of total collagen. Thus, POP is characterized by abnormal biochemical composition and biophysical characteristics of collagen fibrils that form a loose and fragile fiber network accountable for the weak load-bearing capability. The study identifies nanoscale alterations in collagen as diagnostic markers that could enable pre-symptomatic or early diagnosis of POP.

FROM THE CLINICAL EDITOR

Pelvic organ prolapse (POP) occurs due to abnormalities of the supporting connective tissues. The underlying alterations of collagen fibers in the connective tissues have not been studied extensively. In this article, the authors showed that collagen fibrils in POP patients were much different from normal controls. The findings may provide a framework for the diagnosis of other connective diseases.

Assessment of Myocardial Remodeling Using an Elastin/Tropoelastin Specific Agent with High Field Magnetic Resonance Imaging (MRI)

Background

Well-defined inflammation, proliferation, and maturation phases orchestrate the remodeling of the injured myocardium after myocardial infarction (MI) by controlling the formation of new extracellular matrix. The extracellular matrix consists mainly of collagen but also fractions of elastin. It is thought that elastin is responsible for maintaining elastic properties of the myocardium, thus reducing the risk of premature rupture. An elastin/tropoelastin–specific contrast agent (Gd-ESMA) was used to image tropoelastin and mature elastin fibers for in vivo assessment of extracellular matrix remodeling post-MI.

Methods and Results

Gd-ESMA enhancement was studied in a mouse model of myocardial infarction using a 7 T MRI scanner and results were compared to those achieved after injection of a nonspecific control contrast agent, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the infarcted tissue, Gd-ESMA uptake (measured as R1 relaxation rate) steadily increased from day 3 to day 21 as a result of the synthesis of elastin/tropoelastin. R1 values were in good agreement with histological findings. A similar R1 behavior was observed in the remote myocardium. No mature cross-linked elastin was found at any time point. In contrast, Gd-DTPA uptake was only observed in the infarct with no changes in R1 values between 3 and 21 days post-MI.

Conclusions

We demonstrate the feasibility of in vivo imaging of extracellular matrix remodeling post-MI using a tropoelastin/elastin binding MR contrast agent, Gd-ESMA. We found that tropoelastin is the main contributor to the increased MRI signal at late stages of MI where its augmentation in areas of infarction was in good agreement with the R1 increase.

Applications of second-harmonic generation imaging microscopy in ovarian and breast cancer

In this perspective, we discuss how the nonlinear optical technique of second-harmonic generation (SHG) microscopy has been used to greatly enhance our understanding of the tumor microenvironment (TME) of breast and ovarian cancer. Striking changes in collagen architecture are associated with these epithelial cancers, and SHG can image these changes with great sensitivity and specificity with submicrometer resolution. This information has not historically been exploited by pathologists but has the potential to enhance diagnostic and prognostic capabilities. We summarize the utility of image processing tools that analyze fiber morphology in SHG images of breast and ovarian cancer in human tissues and animal models. We also describe methods that exploit the SHG physical underpinnings that are effective in delineating normal and malignant tissues. First we describe the use of polarization-resolved SHG that yields metrics related to macromolecular and supramolecular structures. The coherence and corresponding phase-matching process of SHG results in emission directionality (forward to backward), which is related to sub-resolution fibrillar assembly. These analyses are more general and more broadly applicable than purely morphology-based analyses; however, they are more computationally intensive. Intravital imaging techniques are also emerging that incorporate all of these quantitative analyses. Now, all these techniques can be coupled with rapidly advancing miniaturization of imaging systems to afford their use in clinical situations including enhancing pathology analysis and also in assisting in real-time surgical determination of tumor margins.

Differentiation of Col I and Col III isoforms in stromal models of ovarian cancer by analysis of second harmonic generation polarization and emission directionality

A profound remodeling of the extracellular matrix occurs in many epithelial cancers. In ovarian cancer, the minor collagen isoform of Col III becomes upregulated in invasive disease. Here we use second harmonic generation (SHG) imaging microscopy to probe structural differences in fibrillar models of the ovarian stroma comprised of mixtures of Col I and III. The SHG intensity and forward-backward ratios decrease with increasing Col III content, consistent with decreased phasematching due to more randomized structures. We further probe the net collagen α-helix pitch angle within the gel mixtures using what is believed to be a new pixel-based polarization-resolved approach that combines and extends previous analyses. The extracted pitch angles are consistent with those of peptide models and the method has sufficient sensitivity to differentiate Col I from the Col I/Col III mixtures. We further developed the pixel-based approach to extract the SHG signal polarization anisotropy from the same polarization-resolved image matrix. Using this approach, we found that increased Col III results in decreased alignment of the dipole moments within the focal volume. Collectively, the SHG measurements and analysis all indicate that incorporation of Col III results in decreased organization across several levels of collagen organization. Furthermore, the findings suggest that the collagen isoforms comingle within the same fibrils, in good agreement with ultrastructural data. The pixel-based polarization analyses (both excitation and emission) afford determination of structural properties without the previous requirement of having well-aligned fibers, and the approaches should be generally applicable in tissue.

The extracellular matrix contributes to mechanotransduction in uterine fibroids

The role of the extracellular matrix (ECM) and mechanotransduction as an important signaling factor in the human uterus is just beginning to be appreciated. The ECM is not only the substance that surrounds cells, but ECM stiffness will either compress cells or stretch them resulting in signals converted into chemical changes within the cell, depending on the amount of collagen, cross-linking, and hydration, as well as other ECM components. In this review we present evidence that the stiffness of fibroid tissue has a direct effect on the growth of the tumor through the induction of fibrosis. Fibrosis has two characteristics: (1) resistance to apoptosis leading to the persistence of cells and (2) secretion of collagen and other components of the ECM such a proteoglycans by those cells leading to abundant disposition of highly cross-linked, disoriented, and often widely dispersed collagen fibrils. Fibrosis affects cell growth by mechanotransduction, the dynamic signaling system whereby mechanical forces initiate chemical signaling in cells. Data indicate that the structurally disordered and abnormally formed ECM of uterine fibroids contributes to fibroid formation and growth. An appreciation of the critical role of ECM stiffness to fibroid growth may lead to new strategies for treatment of this common disease.

Type III collagen regulates osteoblastogenesis and the quantity of trabecular bone

Type III collagen (Col3), a fibril-forming collagen, is a major extracellular matrix component in a variety of internal organs and skin. It is also expressed at high levels during embryonic skeletal development and is expressed by osteoblasts in mature bone. Loss of function mutations in the gene encoding Col3 (Col3a1) are associated with vascular Ehlers-Danlos syndrome (EDS). Although the most significant clinical consequences of this syndrome are associated with catastrophic failure and impaired healing of soft tissues, several studies have documented skeletal abnormalities in vascular EDS patients. However, there are no reports of the role of Col3 deficiency on the murine skeleton. We compared craniofacial and skeletal phenotypes in young (6-8 weeks) and middle-aged (>1 year) control (Col3(+/+)) and haploinsufficient (Col3(+/-)) mice, as well as young null (Col3(-/-)) mice by microcomputed tomography (μCT). Although Col3(+/-) mice did not have significant craniofacial abnormalities based upon cranial morphometrics, μCT analysis of distal femur trabecular bone demonstrated significant reductions in bone volume (BV), bone volume fraction (BV/TV), connectivity density, structure model index and trabecular thickness in young adult female Col3(+/-) mice relative to wild-type littermates. The reduction in BV/TV persisted in female mice at 1 year of age. Next, we evaluated the role of Col3 in vitro. Osteogenesis assays revealed that cultures of mesenchymal progenitors collected from Col3(-/-) embryos display decreased alkaline phosphatase activity and reduced capacity to undergo mineralization. Consistent with this data, a reduction in expression of osteogenic markers (type I collagen, osteocalcin and bone sialoprotein) correlates with reduced bone Col3 expression in Col3(+/-) mice and with age in vivo. A small but significant reduction in osteoclast numbers was found in Col3(+/-) compared to Col3(+/+) bones. Taken together, these findings indicate that Col3 plays a role in development of trabecular bone through its effects on osteoblast differentiation.

Effects of collagen deposition on passive and active mechanical properties of large pulmonary arteries in hypoxic pulmonary hypertension

Proximal pulmonary artery (PA) stiffening is a strong predictor of mortality in pulmonary hypertension. Collagen accumulation is mainly responsible for PA stiffening in hypoxia-induced pulmonary hypertension (HPH) in mouse models. We hypothesized that collagen cross-linking and the type I isoform are the main determinants of large PA mechanical changes during HPH, which we tested by exposing mice that resist type I collagen degradation (Col1a1[Formula: see text] and littermate controls (Col1a1[Formula: see text] to hypoxia for 10 days with or without [Formula: see text]-aminopropionitrile (BAPN) treatment to prevent cross-link formation. Static and dynamic mechanical tests were performed on isolated PAs with smooth muscle cells (SMC) in passive and active states. Percentages of type I and III collagen were quantified by histology; total collagen content and cross-linking were measured biochemically. In the SMC passive state, for both genotypes, hypoxia tended to increase PA stiffness and damping capacity, and BAPN treatment limited these increases. These changes were correlated with collagen cross-linking ([Formula: see text]). In the SMC active state, hypoxia increased PA dynamic stiffness and BAPN had no effect in Col1a1[Formula: see text] mice ([Formula: see text]). PA stiffness did not change in Col1a1[Formula: see text] mice. Similarly, damping capacity did not change for either genotype. Type I collagen accumulated more in Col1a1[Formula: see text] mice, whereas type III collagen increased more in Col1a1[Formula: see text] mice during HPH. In summary, PA passive mechanical properties (both static and dynamic) are related to collagen cross-linking. Type I collagen turnover is critical to large PA remodeling during HPH when collagen metabolism is not mutated and type III collagen may serve as a reserve.

Chemical consequences of cutaneous photoageing

Human skin, in common with other organs, ages as a consequence of the passage of time, but in areas exposed to solar ultraviolet radiation, the effects of this intrinsic ageing process are exacerbated. In particular, both the severity and speed of onset of age-related changes, such as wrinkle formation and loss of elasticity, are enhanced in photoaged (also termed extrinsically aged) as compared with aged, photoprotected, skin. The anatomy of skin is characterised by two major layers: an outer, avascular, yet highly cellular and dynamic epidermis and an underlying vascularised, comparatively static and cell-poor, dermis. The structural consequences of photoageing are mainly evident in the extracellular matrix-rich but cell-poor dermis where key extracellular matrix proteins are particularly susceptible to photodamage. Most investigations to date have concentrated on the cell as both a target for and mediator of, ultraviolet radiation-induced photoageing. As the main effectors of dermal remodelling produced by cells (extracellular proteases) generally have low substrate specificity, we recently suggested that the differential susceptibility of key extracellular matrix proteins to the processes of photoageing may be due to direct, as opposed to cell-mediated, photodamage.

In this review, we discuss the experimental evidence for ultraviolet radiation (and related reactive oxygen species)-mediated differential degradation of normally long lived dermal proteins including the fibrillar collagens, elastic fibre components, glycoproteins and proteoglycans. Whilst these components exhibit highly diverse primary and hence macro- and supra-molecular structures, we present evidence that amino acid composition alone may be a useful predictor of age-related protein degradation in both photoexposed and, as a consequence of differential oxidation sensitivity, photoprotected, tissues.

Bidirectional encroachment of collagen into the tunica media in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

Arteries in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) are susceptible to smooth muscle loss and fibrosis, but the molecular components underlying these dramatic vascular changes are not well characterized. The purpose of this study was to investigate the distribution of collagen isoforms in the cerebral vessels of North American CADASIL patients with classical NOTCH3 mutations. Expression of types I-VI collagen in brains obtained at autopsy from six CADASIL patients with cysteine-altering mutations in NOTCH3 was compared to control brain expression. We identified a consistent increase of types I, III, IV, and VI collagen in CADASIL brains. Strong accumulation of types I, III, IV and VI collagen was noted in all calibers of vessels, including small and medium-sized leptomeningeal arteries, small penetrating white matter arteries, and capillaries. Within leptomeningeal arteries, where we could define the three tunicae of each vessel, we found distinct collagen subtype distribution patterns in CADASIL. Types I and III collagen were largely found in either adventitial/medial or transmural locations. Type IV collagen was strictly intimal/medial. Type VI collagen was adventitial or adventitial/medial. Within the thickened penetrating arteries of CADASIL patients, all four collagens extended through most of the arterial wall. We observed increased staining of capillaries in CADASIL for types I, IV, and VI collagen. In conclusion, brain vascular collagen subtypes are increased in CADASIL in multiple layers of all sizes of arteries, with disease-specific changes most prominent in the tunica media and thickened small penetrating vessels. In diseased arteries, types I, III, and VI collagen spreads from an external location (adventitia) into the vascular media, while type IV collagen accumulates in an internal pattern (intima and media). These observations are consistent with a pathological role for collagen accumulation in the vascular media in CADASIL.

Type III collagen, a fibril network modifier in articular cartilage

The collagen framework of hyaline cartilages, including articular cartilage, consists largely of type II collagen that matures from a cross-linked heteropolymeric fibril template of types II, IX, and XI collagens. In the articular cartilages of adult joints, type III collagen makes an appearance in varying amounts superimposed on the original collagen fibril network. In a study to understand better the structural role of type III collagen in cartilage, we find that type III collagen molecules with unprocessed N-propeptides are present in the extracellular matrix of adult human and bovine articular cartilages as covalently cross-linked polymers extensively cross-linked to type II collagen. Cross-link analyses revealed that telopeptides from both N and C termini of type III collagen were linked in the tissue to helical cross-linking sites in type II collagen. Reciprocally, telopeptides from type II collagen were recovered cross-linked to helical sites in type III collagen. Cross-linked peptides were also identified in which a trifunctional pyridinoline linked both an alpha1(II) and an alpha1(III) telopeptide to the alpha1(III) helix. This can only have arisen from a cross-link between three different collagen molecules, types II and III in register staggered by 4D from another type III molecule. Type III collagen is known to be prominent at sites of healing and repair in skin and other tissues. The present findings emphasize the role of type III collagen, which is synthesized in mature articular cartilage, as a covalent modifier that may add cohesion to a weakened, existing collagen type II fibril network as part of a chondrocyte healing response to matrix damage.

Supramolecular interactions in the dermo-epidermal junction zone: anchoring fibril-collagen VII tightly binds to banded collagen fibrils

The dermis and the epidermis of normal human skin are functionally separated by a basement membrane but, together, form a stable structural continuum. Anchoring fibrils reinforce this connection by insertion into the basement membrane and by intercalation with banded collagen fibrils of the papillary dermis. Structural abnormalities in collagen VII, the major molecular constituent of anchoring fibrils, lead to a congenital skin fragility condition, dystrophic epidermolysis bullosa, associated with skin blistering. Here, we characterized the molecular basis of the interactions between anchoring fibrils and banded collagen fibrils. Suprastructural fragments of the dermo-epidermal junction zone were generated by mechanical disruption and by separation with magnetic Immunobeads. Anchoring fibrils were tightly attached to banded collagen fibrils. In vitro binding studies demonstrated that a von Willebrand factor A-like motif in collagen VII was essential for binding of anchoring fibrils to reconstituted collagen I fibrils. Since collagen I and VII molecules reportedly undergo only weak interactions, the attachment of anchoring fibrils to collagen fibrils depends on supramolecular organization of their constituents. This complex is stabilized in situ and resists dissociation by strong denaturants.

Intermolecular cross-linking in fibrotic collagen

The extent, nature and location of the cross-links involved in the stabilization of collagen in fibrotic lesions are crucial to its subsequent removal, naturally or induced by treatment. Stabilization is achieved initially by divalent aldimine and keto-imine intermolecular cross-links located at the end-overlap region in the quarter-stagger alignment of the molecules in the fibre. Elucidation of the location of the cross-links also provides chemical evidence for the organization of the collagen molecule in the fibre. All the fibrous collagens are stabilized by these cross-links, the more stable keto-imine cross-link predominating in the types I and II collagens present in the initial stages of fibrosis. Further stabilization of the lesion usually follows, increasing the resistance to degradative enzymes, thus rendering the fibrosis irreversible. This maturation process, which also occurs in normal ageing, involves the formation of multivalent cross-links derived from the initial aldimine and keto-imine cross-links to form a three-dimensional network through a polymeric peptide (poly-alpha 1CB6 in type I collagen). The nature of these cross-links has not yet been elucidated. The so-called mature cross-link, 3-hydroxypyridinoline, could not be identified in this polymeric network. A secondary process involving non-enzymic glycosylation of lysine residues and subsequent intermolecular cross-linking has also been demonstrated, although the nature and extent of this type of cross-link remain to be determined.

The structure of collagen

A knowledge of the structure of collagen fibrils is important for any rational discussion of the occurrence and treatment of fibrosis. The different genetic types of collagen, and the structure of the triple-helical molecule as refined from X-ray fibre diffraction data, are described. The problem of determining molecular arrangement in native tissues is discussed. The various models proposed for the molecular arrangement of type I collagen are compared and an account is given of the quasi-hexagonal model. A detailed analysis of the X-ray diffraction patterns from native type I collagen fibres is used to provide a quantitative description of the quasi-hexagonal model. Parameters such as molecular positions, azimuthal orientation and axial shift can be estimated from the diffraction patterns. These parameters refer to the helix main-chain. Side-chain conformations can then be built in by molecular graphics and the predicted X-ray pattern for the complete model compared with the observed pattern.

Different crimp patterns in collagen fibrils relate to the subfibrillar arrangement

Collagen fibril ultrastructure and course were examined in different connective tissues by PLM, SEM, TEM, and AFM. In tendons, collagen fibrils were large and heterogeneous with a straight subfibrillar arrangement. They ran densely packed, parallel, and straight changing their direction only in periodic crimps where fibrils showed a local deformation (fibrillar crimps). Other tissues such as aponeurosis, fascia communis, skin, aortic wall, and tendon and nerve sheaths showed thinner uniform fibrils with a helical subfibrillar arrangement. These fibrils appeared in parallel or helical arrangement following a wavy, undulating course. Ligaments showed large fibrils as in tendon, with fibrillar crimps but less packed. Thinner uniform-sized fibrils also were observed. Fibrillar crimps seem to be related to the subfibrillar arrangement being present only in large fibrils with a straight subfibrillar arrangement. These stiffer fibrils respond mainly to unidirectional tensional forces, whereas the flexible thinner fibrils with helical subfibrils can accommodate extreme curvatures without harm, thus responding to multidirectional loadings.

Abnormal Primary Tissue Collagen Composition in the Skin of Recurrent Incisional Hernia Patients

Recurrence of incisional hernia may be as high as 50 per cent. Abnormal collagen I/III ratios have been observed within scar tissue of patients with recurrent incisional hernias. We sought to determine whether collagen composition in primary, nonscarred tissue was similarly affected in these patients. In this prospective, case–control study, nonscarred, primary abdominal wall skin and fascia biopsies were obtained in 12 patients with a history of recurrent incisional hernias and 11 control subjects without any history of hernia while undergoing abdominal laparoscopic surgery. Tissue protein expression of collagen I and III was assessed by immunohistochemistry followed by densitometry analysis. The collagen I/III ratio in skin biopsies from the recurrent hernia group was significantly less compared with control subjects (0.88 ± 0.01 versus 0.98 ± 0.04, respectively, P < 0.05). Fascia biopsies from patients with recurrent hernias was not significantly decreased in collagen I/III ratio compared with control subjects (0.90 ± 0.04 versus 0.94 ± 0.03, respectively, P = 0.17). Decreased collagen I/III ratios within the skin of patients with recurrent hernias not involved with scar or healing tissue suggest an underlying collagen composition defect. Such a primary collagen defect, in addition to abnormal scar formation, likely plays a significant role in the pathogenesis of recurrent incisional hernias.

Modification of collagen formation using supplemented mesh materials

BACKGROUND

Formation of recurrent inguinal and incisional hernia shows an underlying defect in the wound healing process. Even following mesh repair an altered collagen formation and insufficient mesh integration has been found as main reason for recurrences. Therefore the development of bioactive mesh materials to achieve a local modification of the scar formation to improve patients outcome is advisable.

METHODS

Thirty-six male Wistar rats were used within this study. A Mersilene (R) mesh sample was implanted after midline skin incision and subcutaneous preparation. Before implantation mesh samples were incubated for 30 minutes with either one of the following agents: doxycycline, TGF-beta 3, zinc-hydrogeneaspartate, ascorbic acid, hyaluronic acid. Incubation with a physiologic 0.9 % NaCl solution served as control. Seven and 90 days after mesh implantation 3 animals from each group (n = 6) were sacrificed for morphological observations. Collagen quantity and quality was analyzed measuring the collagen/protein as well as the collagen type I/III ratio.

RESULTS

Following an implantation interval of 90 days supplementation with doxycycline (39.3 +/- 7.0 microg/mg) and hyaluronic acid (34.4 +/- 5.8 microg/mg) were found to have a significantly increased collagen/protein ratio compared to implantation of the pure Mersilene (R) mesh samples (28.3 +/- 1.9 microg/mg). Furthermore, an overall increase of the collagen type I/III ratio was found in all groups indicating scar maturation over time. However, no significant differences were found after 7 and 90 days of implantation comparing collagen type I/III ratio of supplemented mesh samples and control group.

CONCLUSIONS

In summary, we found an influence of supplemented mesh materials on collagen deposition. However, the investigated bioactive agents with reported influence on wound healing were not associated with an improved quality in scar formation.

Collagen Changes in the Ureteropelvic Junction after Failed Antegrade Endopyelotomy

PURPOSE

We evaluated the collagen content and differentiation of the ureteropelvic junction (UPJ) of patients who underwent Anderson-Hynes dismembered pyeloplasty after failure of antegrade endopyelotomy.

MATERIALS AND METHODS

A total of 12 UPJ obstructions were examined more than 12 months after endopyelotomy with both histochemical staining to analyze total collagen content and immunohistochemical staining to analyze collagen types I and III. The specimens were compared with 12 primary UPJ obstructions and 6 normal UPJs. Statistical analysis was performed using Fisher's test and Wilcoxon matched-pairs signed-rank test.

RESULTS

Immunohistochemical staining revealed that collagen type I was located in the interfascicular space and collagen type III in the intrafascicular space in all UPJs. We found more collagen in obstructed than in normal UPJs. Collagen type III was more abundant in secondary than in primary UPJ obstructions (P < 0.01). In obstruction after endopyelotomy, the staining intensity of collagen type III was greater than the intensity of collagen type I (P < 0.01).

CONCLUSION

Our results suggest that the success of antegrade endopyelotomy was impaired by an inflammatory process. This condition determined a shift of collagen differentiation toward type III, which is more fibrous than type I.

Effects of soluble fiber on matrix metalloproteinase-2 activity and healing of colon anastomosis in rats given radiotherapy

BACKGROUND AND AIMS

Soluble fiber is fermented by colonic microflora yielding short-chain fatty acids (SCFAs) in the colon. We aimed to investigate the effect of oral administration of soluble fiber on healing of anastomosis and matrix metalloproteinase-2 activity in radiotherapy received colonic anastomosis.

METHOD

Eighty-four Wistar rats were divided into six groups. All rats were performed a left colonic resection with end-to-end anastomosis. Group I received rat cow. Group II received soluble fiber orally for five consecutive days preoperatively as well as 3rd and 6th days postoperatively. Group III received SCFAs via rectum for five consecutive days preoperatively. Group IV received irradiation to the pelvis at a total dose of 24 Gy on the 10th and 5th days before the operation. Group V was exposed to irradiation like the rats in Group IV and oral treatment like the rats in Group II. Group VI received irradiation like the rats in Group IV and transrectal treatment like the rats in Group III. On the 3rd and 7th postoperative days, all the rats were anesthetized to evaluate the anastomosis healing clinically, histologically and biochemically.

RESULTS

Third and 7th day bursting pressures of the rats that were fed with a normal diet and exposed to radiotherapy were significantly decreased (P<0.001). Bursting pressures of Groups V and VI on the 7th day were significantly higher than the control group's bursting pressures (P<0.05). Hydroxyproline levels of Group IV were significantly decreased (P<0.001). Following oral soluble fiber and transrectal administration of SCFAs, these low levels reached to the levels of control radiotherapy group. Matrix metalloproteinase-2 activity of all the rats that were exposed to radiotherapy was higher than the control group (P<0.001). Matrix metalloproteinase-2 enzyme levels in the Groups V and VI were lower than the ones in the Group IV (P<0.001). The histologic parameters of anastomotic healing such as epithelial regeneration, exudate, necrosis, and fibroblast levels were significantly improved by the use of oral soluble fiber and transrectal SCFAs treatment.

CONCLUSION

Undesirable effects of preoperative radiotherapy on mechanical, histological and biochemical parameters can be overcome by oral soluble fiber. Oral soluble fiber administration has similar positive effects like the transrectal administration of the SCFA's.

Different patterns of extracellular matrix protein expression in the convexity and the concavity of the dilated aorta with bicuspid aortic valve: preliminary results

OBJECTIVE

This study aimed to assess extracellular matrix protein expression patterns at the convexity (right anterolateral wall) and the concavity of the dilated ascending aorta in patients with bicuspid aortic valve disease.

METHODS

Aortic wall specimens were retrieved from the convexity and the concavity in 27 bicuspid aortic valve patients (12 with stenosis and 15 with regurgitation) and 6 heart donors (controls). Morphometry, immunohistochemistry, Western blot, and polymerase chain reaction were performed, focusing on matrix proteins involved in vascular remodeling.

RESULTS

Type I and III collagens were significantly decreased in bicuspid-associated dilated aortas versus controls (P < .001), particularly at the convexity (P < .05 vs concavity). Expression of messenger RNA for collagens was lower than normal only in the regurgitant subgroup. At immunohistochemistry, proteins whose overproduction has been demonstrated in response to abnormal wall stress, such as tenascin and fibronectin, were more expressed in the convexity than in the concavity, especially in the stenosis subgroup. Tenascin, which is produced by smooth muscle cells in the synthetic phenotype, was nearly undetectable in controls. Fewer smooth muscle cells (stenosis, P = .017; regurgitation, P = .008) and more severe elastic fiber fragmentation (P = .029 and P < .001) were observed in the convexity versus the concavity.

CONCLUSIONS

In bicuspid-associated aortic dilations, an asymmetric pattern of matrix protein expression was found that was consistent with the asymmetry in wall-stress distribution reported previously. Differences exist between patients with stenosis and those with regurgitation in terms of protein expression and content in the aortic wall. Further studies could clarify the relations between these findings and the pathogenesis of aortic dilatation in bicuspid aortic valve patients.

Reduced expression of collagen type I and increased expression of matrix metalloproteinases 1 in patients with Crohn's disease

Crohn's disease (CD) is a chronic inflammatory bowel disease of still unknown etiology. The aim of our study was to find out whether there are any changes in the colonic wall of CD patients that could give hints for a predisposing disorder concerning the extracellular matrix, especially the collagen metabolism. Eight samples of colonic tissue from patients with Crohn's disease were compared to 14 specimens from patients without Crohn's disease. We performed a sirius red test for the overall collagen content and immunohistochemical studies examining differentiation between" collagen type I and type III and the expression of MMP-1 and MMP-13. In the bowel sections of patients with Crohn's disease, decreased levels of mature collagen type I with a resulting lower ratio of collagen I/III compared to patients without Crohn's disease were found (1.12 +/- 0.29 vs. 1.59 i 0.31). The expression of MMP-1 was significantly increased in the CD group (9.21 i 6.02 vs.6.02 i 1.98), whereas expression of MMP-13 showed no difference in both groups. Our study gives the first indication that preexisting changes of the extracellular matrix in the colonic wall may play a role in the pathogenesis of CD. Further studies have to be done to elucidate these interesting aspect of the pathogenesis in Crohn's disease.

Changes of the extracellular matrix as a risk factor for anastomotic leakage after large bowel surgery

BACKGROUND

Despite improved surgical techniques, anastomotic leakage remains as a serious complication in colorectal surgery, producing increased morbidity and mortality. This prospective study was initiated to test the hypothesis that preexisting disorders in the extracellular matrix (ECM) may be a factor influencing the onset of anastomotic wound healing complications.

METHODS

In this prospective study of 119 patients with colorectal anastomoses, 30 clinical parameters with possible influence on anastomotic complications were evaluated. From all patients, samples of macroscopically intact colonic tissue were obtained at the index operation. Crosspolarization microscopy was performed to analyze the collagen type I/III ratio, and immunohistochemical studies were done to determine the expression of matrix metalloproteinase (MMP) 1, 2, 9, and 13. The patients with uncomplicated postoperative healing were compared with those developing anastomotic leakage.

RESULTS

Patients with impaired anastomotic healing exhibited a significantly lower collagen type I/III ratio compared with the controls. Significantly higher expression of MMP-1 and MMP-2 in the mucosal layers and of MMP-2 and MMP-9 in the submucosal layers was found in the normal bowel wall of the leakage group. These findings were statistically independent from the clinical parameters.

CONCLUSION

The present study confirms the hypothesis that disturbances of the ECM play a role in the pathogenesis of anastomotic leakage after large bowel surgery.

Collagen fibril form and function

The majority of collagen in the extracellular matrix is found in a fibrillar form, with long slender filaments each displaying a characteristic approximately 67?nm D-repeat. Here they provide the stiff resilient part of many tissues, where the inherent strength of the collagen triple helix is translated through a number of hierarchical levels to endow that tissue with its specific mechanical properties. A number of collagen types have important structural roles, either comprising the core of the fibril or decorating the fibril surface to give enhanced functionality. The architecture of subfibrillar and suprafibrillar structures (such as microfibrils), lateral crystalline and liquid crystal ordering, interfibrillar interactions, and fibril bundles is described. The fibril surface is recognized as an area that contains a number of intimate interactions between different collagen types and other molecular species, especially the proteoglycans. The interplay between molecular forms at the fibril surface is discussed in terms of their contribution to the regulation of fibril diameter and their role in interfibrillar interactions.

Do alterations in collagen synthesis play an etiologic role in childhood inguinoscrotal pathologies: an immunohistochemical study

BACKGROUND/PURPOSE

Previous findings have suggested that the development of adult inguinal hernias could be related to alterations in fibrillar collagen synthesis in the hernial sac as a decrease in the ratio of the relative amounts of type I/III collagen. The aim of this study was to investigate whether an alteration in type I and type III collagen synthesis was associated with the development of childhood inguinoscrotal pathologies.

METHODS

The authors analyzed sacs from patients with inguinal hernia (n = 20), hydrocele (n = 10) and undescended testis (n = 10) immunohistochemically using monoclonal antibodies against alpha-smooth muscle actin, collagen type I and III. Peritoneal samples (n = 10) obtained from age-matched patients served as controls. Immunostaining was evaluated by semiquantitative scoring and chi2 test.

RESULTS

The expression pattern of type I and III collagen did not differ among sacs obtained from patients with inguinal hernia, hydrocele, and undescended testis when compared with that of controls. However, strong expression of type III collagen was observed in the hernial sacs of right-sided male inguinal hernia compared with left side.

CONCLUSIONS

Although altered collagen synthesis was reported to play an important role in the development of adult inguinal hernias, our results indicate that a pivotal role in childhood inguinoscrotal pathologies is not likely.

Enxerto peritoneal autógeno e fibroplasia: estudo experimental

OBJETIVO: Avaliar se o enxerto autógeno de peritônio permanece vivo e que tipo de tecido conjuntivo predomina no local. MÉTODO: Foram utilizados 30 ratos machos para o enxerto de um fragmento de peritônio parietal do segmento ântero-superior do abdome, no interior do canal inguinal, fixado com monofilamento. Após 20 dias os animais foram sacrificados, a área doadora reparada e a área do enxerto foram retiradas para estudo histológico á microscopia óptica de luz. Em cinco animais a parede abdominal e o canal inguinal contralateral, sem enxerto, foram utilizados para o estudo de sua anatomia microscópica. RESULTADOS: Houve um predomínio de fibroblastos (células jovens) no enxerto, em relação ao receptor e de colágeno denso não modelado em toda a área da intervenção, predominando no receptor, com índice de significância p < 0,01. CONCLUSÕES: O enxerto permanece vivo. O padrão histológico do tecido conjuntivo predominante no local é o tecido conjuntivo denso não modelado.

Decreased collagen type I/III ratio in patients with recurring hernia after implantation of alloplastic prostheses

BACKGROUND

Abnormal collagen metabolism is suspected to play an important role in the pathogenesis of recurring inguinal and incisional hernias. Whereas alloplastic prostheses are nowadays routinely used, the quantity and quality of collagen formation after repair in humans has not been analysed in a large cohort.

METHOD

Seventy-eight prostheses (Prolene, Atrium, Marlex, Vypro, Mersilene, Gore-Tex) implanted for inguinal and incisional hernia repair were explanted because of recurrence, chronic pain or infection. The mean implantation period was 17.9+/-11.2 (range 0.5-48) months. Collagen formation was investigated quantitatively (collagen-protein ratio) and qualitatively (collagen type I/III ratio). Results were related to clinical data that included gender, age, implantation period, indication for implantation/explantation, type and location of prosthesis.

RESULTS

Mean collagen-protein ratio was 45.3+/-8.5 microg/mg, with significant differences between male (43.8+/-9.1 microg/mg) and female tissue samples (48.1+/-6.8 microg/mg, P=0.033). The mean collagen type I/III ratio of all samples investigated was 2.1+/-1.4. Samples explanted for recurring hernias exhibited a significantly decreased ratio (1.3+/-0.7, P<0.05) compared to samples explanted because of pain (3.4+/-1.2) or infection (2.9+/-1.6). Multivariate analysis excluded independent effects of age, gender, indication for implantation of prostheses, location and implantation period on collagen type I/III ratio.

CONCLUSION

The present study confirms the importance of a biological approach, next to technical aspects, to the understanding of the pathogenesis of recurrent hernia formation and underscores the presence of a disturbed scarring process. The composition of scar tissue with a lowered collagen type I/III ratio and, therefore, reduced tensile strength may be a major contribution to hernia recurrence.

Macromolecular specificity of collagen fibrillogenesis: fibrils of collagens I and XI contain a heterotypic alloyed core and a collagen I sheath

Suprastructures of the extracellular matrix, such as banded collagen fibrils, microfibrils, filaments, or networks, are composites comprising more than one type of macromolecule. The suprastructural diversity reflects tissue-specific requirements and is achieved by formation of macromolecular composites that often share their main molecular components alloyed with minor components. Both, the mechanisms of formation and the final macromolecular organizations depend on the identity of the components and their quantitative contribution. Collagen I is the predominant matrix constituent in many tissues and aggregates with other collagens and/or fibril-associated macromolecules into distinct types of banded fibrils. Here, we studied co-assembly of collagens I and XI, which co-exist in fibrils of several normal and pathologically altered tissues, including fibrous cartilage and bone, or osteoarthritic joints. Immediately upon initiation of fibrillogenesis, the proteins co-assembled into alloy-like stubby aggregates that represented efficient nucleation sites for the formation of composite fibrils. Propagation of fibrillogenesis occurred by exclusive accretion of collagen I to yield composite fibrils of highly variable diameters. Therefore, collagen I/XI fibrils strikingly differed from the homogeneous fibrillar alloy generated by collagens II and XI, although the constituent polypeptides of collagens I and II are highly homologous. Thus, the mode of aggregation of collagens into vastly diverse fibrillar composites is finely tuned by subtle differences in molecular structures through formation of macromolecular alloys.

Vascular collagens: spotlight on the role of type VIII collagen in atherogenesis

Collagens play a central role in maintaining the integrity and stability of the undiseased as well as of the atherosclerotic vessel wall. An imbalanced metabolism may lead to uncontrolled collagen accumulation reducing vessel wall velocity, frequently resulting in arterial occlusion or thrombosis. A reduced production of collagen and its uncontrolled degradation may affect the stability of the vessel wall and especially of the atherosclerotic plaques by making them prone to rupture and aneurysm. This review presents an overview on the four groups of vascular collagens and on their role in atherogenesis. The major focus was to highlight the extraordinary role and importance of the short chain network forming type VIII collagen in the extracellular matrix of undiseased arteries and of atherosclerotic plaques. The molecular structure of type VIII collagen, its cellular origin, its implication in atherogenesis, its temporal and spatial expression patterns in human and experimental models of atherogenesis, the factors modulating its expression, and--not at least--its potential function is discussed.