Repetitive interactions observed in the crystal structure of a collagen-model peptide, [(Pro-Pro-Gly)9]3.

The crystal structure of a collagen-model peptide [(Pro-Pro-Gly)(9)](3) has been determined at 1.33 A resolution. Diffraction data were collected at 100 K using synchrotron radiation, which led to the first structural study of [(Pro-Pro-Gly)(n)](3) under cryogenic conditions. The crystals belong to the P2(1) space group with cell parameters of a = 25.95, b = 26.56, c = 80.14 Angstroms and beta = 90.0 degrees. The overall molecular conformation was consistent with the left-handed 7/2-helical model with an axial repeat of 20 A for native collagen. A total of 332 water molecules were found in an asymmetric unit. Proline residues in adjacent triple-helices exhibited three types of hydrophobic interactions. Furthermore, three types of hydrogen-bonding networks mediated by water molecules were observed between adjacent triple-helices. These hydrophobic interactions and hydrogen-bonding networks occurred at intervals of 20 Angstroms along the c-axis based on the previous sub-cell structures [(Pro-Pro-Gly)(n)](3) (n = 9, 10), which were also seen in the full-cell structure of [(Pro-Pro-Gly)(10)](3). Five proline residues at the Y position in the X-Y-Gly triplet were found in a down-puckering conformation, this being inconsistent with the recently proposed propensity-based hypothesis. These proline residues were forced to adopt opposing puckering because of the prevailing hydrophobic interaction between triple-helices compared with the Pro:Pro stacking interaction within a triple-helix.

Collagen-like triple helix formation of synthetic (Pro-Pro-Gly)10 analogues: (4(S)-hydroxyprolyl-4(R)-hydroxyprolyl-Gly)10, (4(R)-hydroxyprolyl-4(R)-hydroxyprolyl-Gly)10 and (4(S)-fluoroprolyl-4(R)-fluoroprolyl-Gly)10.

For the rational design of a stable collagen triple helix according to the conventional rule that the pyrrolidine puckerings of Pro, 4-hydroxyproline (Hyp) and 4-fluoroproline (fPro) should be down at the X-position and up at the Y-position in the X-Y-Gly repeated sequence for enhancing the triple helix propensities of collagen model peptides, a series of peptides were prepared in which X- and Y-positions were altogether occupied by Hyp(R), Hyp(S), fPro(R) or fPro(S). Contrary to our presumption that inducing the X-Y residues to adopt a down-up conformation would result in an increase in the thermal stability of peptides, the triple helices of (Hyp(S)-Hyp(R)-Gly)(10) and (fPro(S)-fPro(R)-Gly)(10) were less stable than those of (Pro-Hyp(R)-Gly)(10) and (Pro-fPro(R)-Gly)(10), respectively. As reported by Bächinger's and Zagari's groups, (Hyp(R)-Hyp(R)-Gly)(10) which could have an up-up conformation unfavorable for the triple helix, formed a triple helix that has a high thermal stability close to that of (Pro-Hyp(R)-Gly)(10). These results clearly show that the empirical rule based on the conformational preference of pyrrolidine ring at each of X and Y residues should not be regarded as still valid, at least for predicting the stability of collagen models in which both X and Y residues have electronegative groups at the 4-position.

Long-term outcome of the endoscopic correction of vesico-ureteric reflux: a comparison of injected substances.

OBJECTIVE: To summarize the long-term outcome of endoscopic surgery to correct vesico-ureteric reflux (VUR) using different injected substances, i.e. autologous blood, hyaluronan/dextranomer copolymer (HDC), PTFE and glutaraldehyde cross-linked bovine dermal (GAX) collagen. PATIENTS AND METHODS: Treatment results on 270 ureters of 185 patients followed for >5 years (mean 8.5) were summarized according to the injected substances. The substances were injected into the 6 o'clock position of the ureteric orifice endoscopically. "Success" was defined as the absence of VUR for >5 years after a single injection. RESULTS: The treatment was successful in two of 24 patients (8%) with autologous blood, 17 of 32 (53%) with HDC, 108 of 171 (63%) with PTFE and 24 of 43 (56%) with GAX collagen. The success rate was lower in patients with higher grades of VUR. CONCLUSIONS: Autologous blood is unsuitable for clinical application because of its poor durability. We will no longer use PTFE because its safety is not well established. The overall success rates of endoscopic surgery with GAX collagen and HDC were insufficient compared with surgical reimplantation, but it is advantageous that this procedure is less invasive and can be repeated. The cure rate could be improved by excluding high-grade VUR from the indications for endoscopic surgery.

Evaluation of collagen and methylated collagen as gene carriers.

This study explores the potential of DNA complexes prepared with methylated collagen (MC) and unmodified native collagen (NC) to deliver genes into cells. The physicochemical properties and transfection abilities of these two types of complexes are studied in parallel. MC was prepared by methylation of the carboxyl groups of collagen, rendering the collagen net positively charged at neutral pH. NC/DNA complexes were prepared at pH approximately 3, but aggregated rapidly at neutral pH. These complexes did not confer significant protection to DNA due to its poor stability in serum. MC carried a positive charge at neutral pH and formed complexes with DNA in PBS; therefore MC improved DNA binding ability and the stability of the complexes at physiological conditions. MC/DNA complexes were smaller and more stable than NC/DNA complexes in PBS, and sustained released of DNA from MC/DNA complexes was observed for up to 3 weeks in PBS at 37 degrees C. In contrast, NC/DNA complexes released almost all the DNA within 6h under the same condition. In vitro gene transfection experiments revealed that MC mediated a higher gene expression than NC, although the level of gene expression was still much lower than that achieved with polyethyleneimine/DNA complexes. In contrast to in vitro results, NC/DNA complexes yielded a 3.8-fold higher gene expression than naked DNA and MC/DNA complexes (P < 0.05) at week 2 following intramuscular injection at a DNA dose of 3 microg per muscle and a weight ratio of 1. Higher weight ratios resulted in significant decrease of transfection efficiency, particularly for MC/DNA complexes. The results suggested that gene delivery via the intramuscular route followed a different mechanism that demands a different set of physiochemical properties of the carrier from other parental routes. The potential of these collagen-based gene carriers for other administration routes remain to be further investigated.

[Development of new biologically active dressings and methodology of their use]. / Razrabotka novykh biologicheski aktivnykh pereviazochnykh sredstv i metodologiia ikh primeneniia.

Results of development of new biologically active dressings and up-to-date methodology of local treatment of wounds (based on their differential application according to phase and features of wound process) are demonstrated. Data about main properties and specific activity of new biologically active dressings based on natural and synthetic polymers with immobilized drugs are presented. Future trends and efficacy of their appliance in complex treatment of purulent and necrotic wounds are demonstrated.

CosmoDerm/CosmoPlast (human bioengineered collagen) for the aging face.

Type 1 collagen loss in the dermis is one of the primary causes of wrinkles seen in aged skin. Dermal fillers using type 1 collagen derived from bioengineered skin are now being used to treat facial wrinkles. These fillers, known by the trade names of CosmoDerm and CosmoPlast, can be used alone or in combination with hyaluronic acid fillers. The benefit of collagen-based dermal fillers is decreased downtime, decreased bruising, decreased pain on injection, and the ability to return lost structural components to aged skin. Many aesthetic physicians are beginning to use collagen- and hyaluronic-containing fillers in combination to replace both of these natural components of the skin that are lost during the aging process.

Retinoic acid inhibits chondrogenesis of mesenchymal cells by sustaining expression of N-cadherin and its associated proteins.

Retinoic acid (RA) is a well-known regulator of chondrocyte phenotype. RA inhibits chondrogenic differentiation of mesenchymal cells and also causes loss of differentiated chondrocyte phenotype. The present study investigated the mechanisms underlying RA regulation of chondrogenesis. RA treatment in chondrifying mesenchymal cells did not affect precartilage condensation, but blocked progression from precartilage condensation to cartilage nodule formation. This inhibitory effect of RA was independent of protein kinase C and extracellular signal-regulated protein kinase, which are positive and negative regulators of cartilage nodule formation, respectively. The progression from precartilage condensation to cartilage nodule requires downregulation of N-cadherin expression. However, RA treatment caused sustained expression of N-cadherin and its associated proteins including alpha- and beta-catenin suggesting that modulation of expression of these molecules is associated with RA-induced inhibition of chondrogenesis. This hypothesis was supported by the observation that disruption of the actin cytoskeleton by cytochalasin D (CD) blocks RA-induced sustained expression of cell adhesion molecules and overcomes RA-induced inhibition of chondrogenesis. Taken together, our results suggest RA inhibits chondrogenesis by stabilizing cell-to-cell interactions at the post-precartilage condensation stage.

Molecular stability of chemically modified collagen triple helices.

Ionic residues influence the stability of collagen triple helices and play a relevant role in the spontaneous aggregation of fibrillar collagens. Collagen types I and II and some of their CNBr peptides were chemically modified in mild conditions with two different protocols. Primary amino groups of Lys and Hyl were N-methylated by formaldehyde in reducing conditions or N-acetylated by sulfosuccinimidyl acetate. The positive charge of amino groups at physiological pH was maintained after the former modification, whereas it was lost after the latter. These chemical derivatizations did not significantly alter the stability of the triple helical conformation of peptide trimeric species. Also the enthalpic change on denaturation was largely unaffected by derivatizations. This implies that no significant variation of weak bonds, either in number or overall strength, and of entropy occur on modification. These properties can probably be explained by the fact that chemically modified groups maintain the ability to form hydrogen bonds.

Glycated collagen cross-linking alters cardiac mechanics in volume-overload hypertrophy.

Alteration of hemodynamic loading induces remodeling that includes changes in myocardial properties and extracellular matrix structure. We investigated the hypothesis that cardiac hypertrophy due to volume overload produces changes in myocardial diastolic mechanics and stiffness that are in part due to alterations in advanced glycation end-product (AGE) collagen cross-linking. Rats developed volume overload induced by arteriovenous fistula (AVF). To assess the dependence of AGE cross-linking on mechanics, we prevented AGE formation by administering the drug aminoguanidine (AG) to one group of AVF rats (AG+AVF). Volume overload did not modify collagen concentration. Right ventricular AGE cross-links were modestly elevated in AVF hearts but were significantly reduced by AG. AVF rats exhibited significantly increased septal AGE cross-links that were inhibited in the AG+AVF group. AVF-induced increases in left ventricular longitudinal stiffness and septal circumferential stiffness were prevented in AG+AVF hearts. Volume overload appears to regionally modify AGE collagen cross-linking and stiffness, and AG treatment prevented these increases, demonstrating that AGE cross-linking plays a role in mediating diastolic compliance in volume-overload hypertrophy.

In vitro reconstruction of human dermal equivalent enriched with endothelial cells.

Experiences coming from many cell-culture studies has brought about the concept that tissue and organ reconstruction should be performed in a three-dimensional environment as it normally occurs in vivo. As far as endothelial cell culture is concerned, it has been shown that angiogenesis can be successfully achieved only when cells are cultured in the presence of collagen-based matrices or basal membrane substrates. The aim of the present investigation is to demonstrate that human umbilical vein endothelial cells (HUVEC) can be grown and differentiated on an artificial dermis obtained by fibroblasts cultured on hyaluronic acid-based scaffolds. For this purpose, we have cultured HUVEC, retrieved by collagenase digestion of perfused human umbilical vein either alone and with fibroblast at 1/1 ratio into HYAFF-11 non-woven mesh. Cultures were maintained for up to 3 weeks. Samples were taken at different time points within this period for the MTT proliferation test and for immunohistochemical analysis. Our results demonstrate that hyaluronan-based biomaterials (HYAFF-11 NW mesh) represent a suitable substrate for HUVEC adhesion, proliferation and reorganization in microcapillary network.

Estudo da interação entre células endoteliais humanas e biomateriais utilizados em cirurgia buco-maxilo-facial / Interaction of human endothelial cells with biomaterials applied on maxillo-facial surgery

Neste estudo procuramos analisar a interação entre células endoteliais humanas e biomateriais utilizados em cirurgia oral, através de análises histológicas e ensaios imunocitoquímicos. Culturas primárias foram isoladas de veias de cordões umbilicais humanos. As células foram semeadas, em densidade determinada, sobre secções circulares de membrana colágena, placas de titânio e controles; foram mantidas por 1, 7 ou 14 dias. As células proliferaram, atingiram confluência e após 14 dias formaram camada plana e uniforme. Os resultados demonstraram que os materiais estudados permitem a proliferação e a adesão das células endoteliais. Esta adesão é mediada pela interação de integrinas e proteínas.With the present investigation, we examined the behavior of endothelial cells on two different biomaterials, using histological and immunocitochemical methods. The endothelial cells were isolated from umbilical cord veins. Cells, after two passages, were seeded in a standard density on a collagen membrane, on commercially pure titanium in the form of plates and on control surfaces. Then these were maintained for 1, 7 or 14 days. After 14 days, we could observe a confluent monolayer of cells. Our results showed that both studied materials support endothelial cells growth and attachment and this is most related to the binding through integrins and proteins...

Collagen stability: insights from NMR spectroscopic and hybrid density functional computational investigations of the effect of electronegative substituents on prolyl ring conformations.

Collagen-like peptides of the type (Pro-Pro-Gly)(10) fold into stable triple helices. An electron-withdrawing substituent at the H(gamma)(3) ring position of the second proline residue stabilizes these triple helices. The aim of this study was to reveal the structural and energetic origins of this effect. The approach was to obtain experimental NMR data on model systems and to use these results to validate computational chemical analyses of these systems. The most striking effects of an electron-withdrawing substituent are on the ring pucker of the substituted proline (Pro(i)) and on the trans/cis ratio of the Xaa(i-1)-Pro(i) peptide bond. NMR experiments demonstrated that N-acetylproline methyl ester (AcProOMe) exists in both the C(gamma)-endo and C(gamma)-exo conformations (with the endo conformation slightly preferred), N-acetyl-4(R)-fluoroproline methyl ester (Ac-4R-FlpOMe) exists almost exclusively in the C(gamma)-exo conformation, and N-acetyl-4(S)-fluoroproline methyl ester (Ac-4S-FlpOMe) exists almost exclusively in the C(gamma)-endo conformation. In dioxane, the K(trans/cis) values for AcProOMe, Ac-4R-FlpOMe, and Ac-4S-FlpOMe are 3.0, 4.0, and 1.2, respectively. Density functional theory (DFT) calculations with the (hybrid) B3LYP method were in good agreement with the experimental data. Computational analysis with the natural bond orbital (NBO) paradigm shows that the pucker preference of the substituted prolyl ring is due to the gauche effect. The backbone torsional angles, phi and psi, were shown to correlate with ring pucker, which in turn correlates with the known phi and psi angles in collagen-like peptides. The difference in K(trans/cis) between AcProOMe and Ac-4R-FlpOMe is due to an n-->pi interaction associated with the Bürg-Dunitz trajectory. The decrease in K(trans/cis) for Ac-4S-FlpOMe can be explained by destabilization of the trans isomer because of unfavorable electronic and steric interactions. Analysis of the results herein along with the structures of collagen-like peptides has led to a theory that links collagen stability to the interplay between the pyrrolidine ring pucker, phi and psi torsional angles, and peptide bond trans/cis ratio of substituted proline residues.

Delayed branching of endothelial capillary-like cords in glycated collagen I is mediated by early induction of PAI-1.

Development of micro- and macrovascular disease in diabetes mellitus (DM) warrants a thorough investigation into the repertoire of endothelial cell (EC) responses to diabetic environmental cues. Using human umbilical vein EC (HUVEC) cultured in three-dimensional (3-D) native collagen I (NC) or glycated collagen I (GC), we observed capillary cord formation that showed a significant reduction in branching when cells were cultured in GC. To gain insight into the molecular determinants of this phenomenon, HUVEC subjected to GC vs. NC were studied using a PCR-selected subtraction approach. Nine different genes were identified as up- or downregulated in response to GC; among those, plasminogen activator inhibitor-1 (PAI-1) mRNA was found to be upregulated by GC. Western blot analysis of HUVEC cultured on GC showed an increase in PAI-1 expression. The addition of a neutralizing anti-PAI-1 antibody to HUVEC cultured in GC restored the branching pattern of formed capillary cords. In contrast, supplementation of culture medium with the constitutively active PAI-1 reproduced defective branching patterns in HUVEC cultured in NC. Ex vivo capillary sprouting in GC was unaffected in PAI-1 knockout mice but was inhibited in wild-type mice. This difference persisted in diabetic mice. In conclusion, the PCR-selected subtraction technique identified PAI-1 as one of the genes characterizing an early response of HUVEC to the diabetic-like interstitial environment modeled by GC and responsible for the defective branching of endothelial cells. We propose that an upregulation of PAI-1 is causatively linked to the defective formation of capillary networks during wound healing and eventual vascular dropout characteristic of diabetic nephropathy.

Effects of dexamethasone on proliferation, chemotaxis, collagen I, and fibronectin-metabolism of human fetal lung fibroblasts.

Premature infants at risk for bronchopulmonary dysplasia (BPD) are often treated with dexamethasone (Dex), which has been shown to suppress inflammatory processes in the lung. To elucidate a possible direct influence on the fibroproliferative component of the disease, we studied the effects of Dex in therapeutic and supratherapeutic dosages (5-50 nmol/L) on proliferation, chemotaxis, procollagen I, and fibronectin metabolism of human fetal lung fibroblasts in vitro. Proliferation was inhibited by Dex in a dose-dependent manner. Chemotactic activity in response to conditioned medium of human fetal fibroblasts also showed a dose-dependent inhibition after pretreatment with Dex. The amount of procollagen I C-terminal propeptide and fibronectin per cell in the cell culture supernatant was increased in the presence of Dex. Our results show that Dex does not uniformly suppress the fibroproliferative activity of human fetal lung fibroblasts, which may explain in part the unsatisfactory long-term effects of Dex treatment in BPD.

[Experimental study of antiseptic (tauroline, taurolidine) and antibiotic (sulmycin implant) drugs in vascular prosthesis infections in a standardized infection model]. / Experimentelle Untersuchung antiseptischer (Taurolin, Taurolidin) und antibiotischer (Sulmycin -Implant) Substanzen bei Gefässprotheseninfektionen im standardisierten Infektionsmodell.

UNLABELLED: It was the aim to examine whether local application of antiseptic and antibiotic substances is an effective treatment of vascular graft infection. MATERIAL AND METHODS: 19 pigs with a bodyweight between 20 and 30 kg were assigned to three different groups. Group I: control (6), group II: local treatment with Sulmycin implant, group (6) III: local treatment with Taurolin (Taurolidine) (7). An unprotected vascular graft was inserted in the right femoral artery of all pigs. After finishing the proximal and distal anastomosis and prior to closure of the incision, the vascular grafts were contaminated locally with 2 x 10(7) CFU/ml Staphylococcus aureus ATCC 29213. Seven days later all animals received another unprotected vascular prosthesis with or without additional treatment according to groups I, II, III. 28 days after primary operation the animals were euthanized and the grafts harvested. The specimens were examined for signs of infection by histology and microbiology. RESULTS: After the primary operation all animals presented with infected vascular prosthesis. At termination of the trial on day 28 all grafts of group I were contaminated, 5 out of 6 grafts in group II, and 5 out of 7 in group III presented with infected grafts. There was no significant statistical difference between the groups. Infection could not be prevented by the antimicrobial agents used. The primary infecting organism Staphylococcus aureus, however, was eliminated in all cases. CONCLUSIONS: Both antimicrobial substances examined were not effective in the treatment of vascular graft infection, but might be used as adjuvant therapy of vascular graft infection, whereby Sulmycin implant seems to be more effective regarding the incorporation of the prosthesis.

Current status of injectable agents for female stress urinary incontinence.

The purpose of this review is to summarize the results of reports of injectable agents for the treatment of female urinary stress incontinence. Five agents were reviewed: collagen, Teflon, autologous fat, silicone microparticles, and silicone microballoons. Collagen was the most frequently reported agent and yielded short-term cure and improved rates of 74%-100%. This deteriorated to approximately 57% with longer term follow-up. Teflon has similarly lower longer term than short-term success rates, at 33%-76%. The reported local complications and the potential for particle migration have resulted in its lack of widespread acceptance. Autologous fat has yielded the lowest success rate. Longer term success in a small number of silicone microparticle articles was similar to the other injectables at approximately 60%. Early success with silicone microballoons was 70%. The technique is generally free of major morbidity. The indication for injectables is intrinsic sphincter deficiency but hypermobility is not a contraindication. Long-term durability, cost effectiveness, and some safety issues still have to be addressed by further clinical trials.

Comparative analysis of different collagen-based biomaterials as scaffolds for long-term culture of human fibroblasts.

Biodegradable scaffolds, along with cells, are important components of most tissue-engineered constructs. In the study, there is a comparison of the behaviour of human fibroblasts cultured for up to six weeks in four different collagen-based three-dimensional matrices, in the form of sponges composed of pure native type I collagen (control), of collagen-GAG-chitosan (CGC) and of collagen cross-linked by two concentrations of diphenylphosphorylazide (DPPA-2 and DPPA-3). Variations in size and weight of the sponges, as well as fibroblast growth and migration, and total protein and collagen synthesis, are determined with time in culture. Owing to their low thermal stability, the partial denaturation and dissolution of the control sponges after incubation at 37 degrees C lead to considerable contraction and low cell proliferation. CGC sponges, stabilised by ionic interactions between the different components, show, after six weeks, limited contraction (20%) and weight increase (10% when seeded) and high cell growth (threefold increase). Similar results are obtained with weakly, cross-linked (DPPA-2) collagen sponges. Highly cross-linked (DPPA-3) sponges do not contract, whereas weight gain and cell proliferation are no different from those found with CGC and DPPA-2 sponges. Similar levels of total protein and collagen synthesis are shown for fibroblasts seeded in different matrices, with a slight general decrease (twofold) after three weeks, a much lower value than that observed with fibroblasts in culture within a contracted collagen gel (sixfold). Furthermore, the fraction of neo-synthesised collagen deposited in the sponges after six weeks represents more than 60% of the total, compared with only 10% obtained with fibroblasts in monolayer culture or 30% within a collagen gel. These results indicate that the matrices, particularly the CGC and DPPA-2 sponges, provide excellent supports for fibroblast growth and the formation of dermal and skin equivalents.

Collagen-based biomaterials as 3D scaffold for cell cultures: applications for tissue engineering and gene therapy.

Many substances are used in the production of biomaterials: metals (titanium), ceramics (alumina), synthetic polymers (polyurethanes, silicones, polyglycolic acid (PGA), polylactic acid (PLA), copolymers of lactic and glycolic acids (PLGA), polyanhydrides, polyorthoesters) and natural polymers (chitosan, glycosaminoglycans, collagen). With the rapid development in tissue engineering, these different biomaterials have been used as three-dimensional scaffolds and cell transplant devices. The principal biochemical and biological characteristics of the collagen-based biomaterials are presented, including their interactions with cells (fibroblasts), distinct from those of synthetic polymers, and their potential use in gene therapy through the formation of neo-organs or organoids.

Human-derived and new synthetic injectable materials for soft-tissue augmentation: current status and role in cosmetic surgery.

The recent development of human-derived and new synthetic filling agents heralds a new era in soft-tissue augmentation. Many of the disadvantages of xenogenic and prior exogenous materials have been overcome with the advent of these autologous, allogeneic, and inert synthetic alternatives. Early reports using human-derived and inert exogenous filling agents have demonstrated good results and prolonged correction. It is too early, however, to assess the long-term efficacy of these agents. Future investigations should include histologic examination after facial implantation to document long-term safety and efficacy.

Use of collagen for the treatment of stress urinary incontinence: an update.

This article provides a comprehensive and updated overview of the current role of collagen injections in the management of genuine stress incontinence. The clinical indications for collagen injection are described, and relevant technical advances are discussed. Finally, we review the latest outcome data on the use of collagen injection, as well as the factors that affect outcome.