ESTIMATION OF HYDROXYPROLINE BY THE AUTOANALYSER

Characterization of Type I and Type III Collagen in the Intramuscular Connective Tissue of Wuzhumuqin Sheep

Intramuscular connective tissue (IMCT) collagen is an important factor in meat quality. This study analyzed the characteristics of type I and III collagen in the IMCT of the semitendinosus (SD) and longissimus dorsi (LD) of Wuzhumuqin sheep at different growth stages (6, 9, 12, and 18 months). Utilizing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR), collagen types I and III were successfully isolated and shown to contain an intact triple helix structure. Immunofluorescence revealed that these collagens were located in the endomysium and perimysium. Collagen-related genes were significantly expressed in sheep aged 9 and 12 months. The amino acid content increased with age in type I collagen whereas it decreased in type III collagen. Furthermore, type III collagen contained more hydroxyproline (Hyd) than type I collagen. Differential scanning calorimetry (DSC) revealed that the thermal stability of collagen increased with age, accompanied by a decrease in solubility. Semitendinosus muscle had more collagen cross-linkages than LD muscle due to the high pyridinoline (Pyr) content in the endomysium. Finally, a correlation analysis highlighted the multiple correlations between characteristics in different types of collagen during sheep growth. In summary, the collagen characteristics in the IMCT of sheep were impacted by collagen type, muscle type, and age. Furthermore, the various correlations between these characteristics may play an important role in the development of IMCT.

Engineered Tissue-Stent Biocomposites as Tracheal Replacements

Here we report the creation of a novel tracheal construct in the form of an engineered, acellular tissue-stent biocomposite trachea (TSBT). Allogeneic or xenogeneic smooth muscle cells are cultured on polyglycolic acid polymer-metal stent scaffold leading to the formation of a tissue comprising cells, their deposited collagenous matrix, and the stent material. Thorough decellularization then produces a final acellular tubular construct. Engineered TSBTs were tested as end-to-end tracheal replacements in 11 rats and 3 nonhuman primates. Over a period of 8 weeks, no instances of airway perforation, infection, stent migration, or erosion were observed. Histological analyses reveal that the patent implants remodel adaptively with native host cells, including formation of connective tissue in the tracheal wall and formation of a confluent, columnar epithelium in the graft lumen, although some instances of airway stenosis were observed. Overall, TSBTs resisted collapse and compression that often limit the function of other decellularized tracheal replacements, and additionally do not require any cells from the intended recipient. Such engineered TSBTs represent a model for future efforts in tracheal regeneration.

The Effect of Early Postoperative Physical Activity on Tissue Oxygen and Wound Healing

Background. Supplemented postoperative activity was compared to standard activity for effects on wound healing, subcutaneous tissue perfusion, and oxygen (PscO2 ) following hip replacement (THR).

Methods. 58 patients were randomized to standard post-THR activity (N = 27) or supplemental activity (N = 31) (arm and leg exercises, walking protocol). PscO2 was measured with a microelectrode/tonometer system and perfusion determined by oxygen response. Healing was evaluated by (1) tissue cellularity, (2) mRNA for pro collagen, (3) hydroxyproline, and (4) DNA content obtained from a subcutaneous implant removed on the 7th postoperative day.

Results. Activity significantly increased DNA levels, but did not increase PscO2 , perfusion, cellularity, or collagen measures.

Conclusions. Healing measures were not improved with increased activity levels. However, activity did not reduce PscO2 or wound healing. The majority of patients adhered to additional activity and tolerated the protocol well. Increased activity was associated with earlier discharge, suggesting other recovery-related benefits.

Genipin crosslinking reduced the immunogenicity of xenogeneic decellularized porcine whole-liver matrices through regulation of immune cell proliferation and polarization

Decellularized xenogeneic whole-liver matrices are plausible biomedical materials for the bioengineering of liver transplantation. A common method to reduce the inflammatory potential of xenogeneic matrices is crosslinking. Nevertheless, a comprehensive analysis of the immunogenic features of cross-linked decellularized tissue is still lacking. We aimed to reduce the immunogenicity of decellularized porcine whole-liver matrix through crosslinking with glutaraldehyde or genipin, a new natural agent, and investigated the mechanism of the immune-mediated responses. The histologic assessment of the host's immune reaction activated in response to these scaffolds, as well as the M1/M2 phenotypic polarization profile of macrophages, was studied in vivo. The genipin-fixed scaffold elicited a predominantly M2 phenotype response, while the glutaraldehyde-fixed scaffold resulted in disrupted host tissue remodeling and a mixed macrophage polarization profile. The specific subsets of immune cells involved in the responses to the scaffolds were identified in vitro. Crosslinking alleviated the host response by reducing the proliferation of lymphocytes and their subsets, accompanied by a decreased release of both Th1 and Th2 cytokines. Therefore, we conclude that the natural genipin crosslinking could lower the immunogenic potential of xenogeneic decellularized whole-liver scaffolds.

Optimizing perfusion-decellularization methods of porcine livers for clinical-scale whole-organ bioengineering

Aim. To refine the decellularization protocol of whole porcine liver, which holds great promise for liver tissue engineering. Methods. Three decellularization methods for porcine livers (1% sodium dodecyl sulfate (SDS), 1% Triton X-100 + 1% sodium dodecyl sulfate, and 1% sodium deoxycholate + 1% sodium dodecyl sulfate) were studied. The obtained liver scaffolds were processed for histology, residual cellular content analysis, and extracellular matrix (ECM) components evaluation to investigate decellularization efficiency and ECM preservation. Rat primary hepatocytes were seeded into three kinds of scaffold to detect the biocompatibility. Results. The whole liver decellularization was successfully achieved following all three kinds of treatment. SDS combined with Triton had a high efficacy of cellular removal and caused minimal disruption of essential ECM components; it was also the most biocompatible procedure for primary hepatocytes. Conclusion. We have refined a novel, standardized, time-efficient, and reproducible protocol for the decellularization of whole liver which can be further adapted to liver tissue engineering.

Method for perfusion decellularization of porcine whole liver and kidney for use as a scaffold for clinical-scale bioengineering engrafts

BACKGROUND

Whole-organ engineering provides a new alternative source of donor organs for xenotransplantation. Utilization of decellularized whole-organ scaffolds, which can be created by detergent perfusion, is a strategy for tissue engineering. In this article, our aim is to scale up the decellularization process to human-sized liver and kidney to generate a decellularized matrix with optimal and stable characteristics on a clinically relevant scale.

METHODS

Whole porcine liver and kidney were decellularized by perfusion using different detergents (1% SDS, 1% Triton X-100, 1% peracetic acid (PAA), and 1% NaDOC) via the portal vein and renal artery of the liver and kidney, respectively. After rinsing with PBS to remove the detergents, the obtained liver and kidney extracellular matrix (ECM) were processed for histology, residual cellular content analysis, and ECM components evaluation to investigate decellularization efficiency, xenoantigens removal, and ECM preservation.

RESULTS

The resulting liver and kidney scaffolds in the SDS-treated group showed the most efficient clearance of cellular components and xenoantigens, including DNA and protein, and preservation of the extracellular matrix composition. In comparison, cell debris was observed in the other decellularized groups that were generated using Triton X-100, PAA, and NaDOC. Special staining and immunochemistry of the porcine liver and kidney ECMs further confirmed the disrupted three-dimension ultrastructure of the ECM in the Triton X-100 and NaDOC groups. Additionally, Triton X-100 effectively eliminated the residual SDS in the SDS-treated group, which ensured the scaffolds were not cytotoxic to cells. Thus, we have developed an optimal method that can be scaled up for use with other solid whole organs.

CONCLUSIONS

Our SDS-perfusion protocol can be used for porcine liver and kidney decellularization to obtain organ scaffolds cleared of cellular material, xenoimmunogens, and preserved vital ECM components.

Influence of pH on extracellular matrix preservation during lung decellularization

The creation of decellularized organs for use in regenerative medicine requires the preservation of the organ extracellular matrix (ECM) as a means to provide critical cues for differentiation and migration of cells that are seeded onto the organ scaffold. The purpose of this study was to assess the influence of varying pH levels on the preservation of key ECM components during the decellularization of rat lungs. Herein, we show that the pH of the 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS)-based decellularization solution influences ECM retention, cell removal, and also the potential for host response upon implantation of acellular lung tissue. The preservation of ECM components, including elastin, fibronectin, and laminin, were better retained in the lower pH conditions that were tested (pH ranges tested: 8, 10, 12); glycosaminoglycans were preserved to a higher extent in the lower pH groups as well. The DNA content following decellularization of the rat lung was inversely correlated with the pH of the decellularization solution. Despite detectible levels of cyotoskeletal proteins and significant residual DNA, tissues decellularized at pH 8 demonstrated the greatest tissue architecture maintenance and the least induction of host response of all acellular conditions. These results highlight the effect of pH on the results obtained by organ decellularization and suggest that altering the pH of the solutions used for decellularization may influence the ability of cells to properly differentiate and home to appropriate locations within the scaffold, based on the preservation of key ECM components and implantation results.

Systematic test of neurotoxin dose and volume on muscle function in a rat model

INTRODUCTION

Onabotulinum toxin serotype A (BT-A) is used for a variety of motor and sensory disorders related to abnormal muscle activity.

METHODS

We developed a high-resolution rodent model to allow precise determination of the effect of BT-A dose (measured in units) and injectate volume (measured in μl) on the efficacy of the injection and systemic side effects. Dorsiflexion is the best indicator of injected and contralateral muscle function.

RESULTS

One month after injection, dorsiflexion torque of BT-A-injected limbs was decreased significantly in all experimental groups compared with saline controls (P < 0.05). Torque was also compared among the BT-A groups, which demonstrated a significant effect of dose (P < 0.001), but no effect of volume (P > 0.2) and no dose × volume interaction (P > 0.3). Similar results were observed for other parameters measured.

CONCLUSIONS

These data demonstrate that injection dose and not volume or concentration is the primary determinant of neurotoxin efficacy in a rodent model.

Cellular mechanisms of tissue fibrosis. 4. Structural and functional consequences of skeletal muscle fibrosis

Skeletal muscle fibrosis can be a devastating clinical problem that arises from many causes, including primary skeletal muscle tissue diseases, as seen in the muscular dystrophies, or it can be secondary to events that include trauma to muscle or brain injury. The cellular source of activated fibroblasts (myofibroblasts) may include resident fibroblasts, adult muscle stem cells, or inflammatory or perivascular cells, depending on the model studied. Even though it is likely that there is no single source for all myofibroblasts, a common mechanism for the production of fibrosis is via the transforming growth factor-β/phosphorylated Smad3 pathway. This pathway and its downstream targets thus provide loci for antifibrotic therapies, as do methods for blocking the transdifferentiation of progenitors into activated fibroblasts. A structural model for the extracellular collagen network of skeletal muscle is needed so that measurements of collagen content, morphology, and gene expression can be related to mechanical properties. Approaches used to study fibrosis in tissues, such as lung, kidney, and liver, need to be applied to studies of skeletal muscle to identify ways to prevent or even cure the devastating maladies of skeletal muscle.

Evaluation of two decellularization methods in the development of a whole-organ decellularized rat liver scaffold

AIM

Hepatic tissue engineering is considered as a possible alternative to liver transplantation for end-stage liver disease. Several methods of decellularization of xenogeneic liver are available to produce three-dimensional organ scaffolds for engineering liver tissues. However, rare studies have examined and compared the effectiveness of different methods on the structure and composition of intact decellularized liver extracellular matrix.

METHODS

Two decellularization methods were adopted herein. Their effects on collagen, elastin, glycosaminoglycans (GAGs), hepatocyte growth factor (HGF) content and influence to the function of hepatocytes cultured in scaffolds were examined and compared.

RESULTS

The complete tissue decellularization was successfully achieved after treatment with sodium dodecyl sulphate (SDS) and Triton X-100. The total absence of nuclear structures and removal of viable cells were confirmed by haematoxylin-eosin staining and scanning electron microscopy. Collagen was preserved after both treatments. However, the elastin content decreased to about 20% and 60%, the GAGs content decreased to about 10% and 50% and the HGF content decreased to about 20% and 60% of the native liver level after SDS and Triton X-100 treatment respectively. The Triton X-100-treated scaffolds were much superior than SDS-treated scaffolds in supporting liver-specific function, including albumin secretion (P = 0.001), urea synthesis (P = 0.002), ammonia elimination (P = 0.007) and mRNA expression levels of drug metabolism enzymes.

CONCLUSION

This study suggested that liver extracellular matrix scaffolds constructed using perfusion of Triton X-100 as described herein might provide a more effective and ideal material for the usage in tissue engineering and regenerative medicine approaches.

Cell proliferation on three-dimensional chitosan-agarose-gelatin cryogel scaffolds for tissue engineering applications

Tissue engineering is a potential approach for the repair of damaged tissues or organs like skin, cartilage, bone etc. Approach utilizes the scaffolds constructed from natural or synthetic polymers fabricated by the available fabrication technologies. This study focuses on the fabrication of the scaffolds using a novel technology called cryogelation, which synthesizes the scaffolds at sub-zero temperature. We have synthesized a novel scaffold from natural polymers like chitosan, agarose and gelatin in optimized ratio using the cryogelation technology. The elasticity of the scaffold was confirmed by rheological studies which supports the utility of the scaffolds for skin and cardiac tissue engineering. Proliferation of different cell types like fibroblast and cardiac cells was analysed by scanning electron microscopy (SEM) and fluorescent microscopy. Biocompatibility of the scaffolds was tested by MTT assay with specific cell type, which showed higher proliferation of the cells on the scaffolds when compared to the two dimensional culture system. Cell proliferation of C(2)C(12) and Cos 7 cells on these scaffolds was further analysed biochemically by alamar blue test and Hoechst test. Biochemical and microscopic analysis of the different cell types on these scaffolds gives an initial insight of these scaffolds towards their utility in skin and cardiac tissue engineering.

Skeletal muscle fibrosis develops in response to desmin deletion

Skeletal muscle is a dynamic composite of proteins that responds to both internal and external cues to facilitate muscle adaptation. In cases of disease or altered use, these messages can be distorted resulting in myopathic conditions such as fibrosis. In this work, we describe a mild and progressive fibrotic adaptation in skeletal muscle lacking the cytoskeletal intermediate filament protein desmin. Muscles lacking desmin become progressively stiffer, accumulate increased collagen, and increase expression of genes involved in extracellular matrix turnover. Additionally, in the absence of desmin, skeletal muscle is in an increased state of inflammation and regeneration as indicated by increased centrally nucleated fibers, elevated inflammation and regeneration related gene expression, and increased numbers of inflammatory cells. These data suggest a potential link between increased cellular damage and the development of fibrosis in muscles lacking the cytoskeletal support of the desmin filament network.

Matrix composition and mechanics of decellularized lung scaffolds

The utility of decellularized native tissues for tissue engineering has been widely demonstrated. Here, we examine the production of decellularized lung scaffolds from native rodent lung using two different techniques, principally defined by use of either the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) or sodium dodecyl sulfate (SDS). All viable cellular material is removed, including at least 99% of DNA. Histochemical staining and mechanical testing indicate that collagen and elastin are retained in the decellularized matrices with CHAPS-based decellularization, while SDS-based decellularization leads to loss of collagen and decline in mechanical strength. Quantitative assays confirm that most collagen is retained with CHAPS treatment but that about 80% of collagen is lost with SDS treatment. In contrast, for both detergent methods, at least 60% of elastin content is lost along with about 95% of native proteoglycan content. Mechanical testing of the decellularized scaffolds indicates that they are mechanically similar to native lung using CHAPS decellularization, including retained tensile strength and elastic behavior, demonstrating the importance of collagen and elastin in lung mechanics. With SDS decellularization, the mechanical integrity of scaffolds is significantly diminished with some loss of elastic function as well. Finally, a simple theoretical model of peripheral lung matrix mechanics is consonant with our experimental findings. This work demonstrates the feasibility of producing a decellularized lung scaffold that can be used to study lung matrix biology and mechanics, independent of the effects of cellular components.

Utility of telomerase-pot1 fusion protein in vascular tissue engineering

While advances in regenerative medicine and vascular tissue engineering have been substantial in recent years, important stumbling blocks remain. In particular, the limited life span of differentiated cells that are harvested from elderly human donors is an important limitation in many areas of regenerative medicine. Recently, a mutant of the human telomerase reverse transcriptase enzyme (TERT) was described, which is highly processive and elongates telomeres more rapidly than conventional telomerase. This mutant, called pot1-TERT, is a chimeric fusion between the DNA binding protein pot1 and TERT. Because pot1-TERT is highly processive, it is possible that transient delivery of this transgene to cells that are utilized in regenerative medicine applications may elongate telomeres and extend cellular life span while avoiding risks that are associated with retroviral or lentiviral vectors. In the present study, adenoviral delivery of pot1-TERT resulted in transient reconstitution of telomerase activity in human smooth muscle cells, as demonstrated by telomeric repeat amplification protocol (TRAP). In addition, human engineered vessels that were cultured using pot1-TERT-expressing cells had greater collagen content and somewhat better performance in vivo than control grafts. Hence, transient delivery of pot1-TERT to elderly human cells may be useful for increasing cellular life span and improving the functional characteristics of resultant tissue-engineered constructs.

quantitative determination of collagen cross-links

The primary functional role of collagen is as a supporting tissue and it is now established that the aggregated forms of the collagen monomers are stabilised to provide mechanical strength by a series of intermolecular cross-links. In order to understand the mechanical properties of collagen, it is necessary to identify and quantitatively determine the concentration of the cross-links during their changes with maturation, ageing and disease. These cross-links are formed by oxidative deamination of the epsilon-amino group of the single lysine or hydroxylysine in the amino and carboxy telopeptides of collagen by lysyl oxidase, the aldehyde formed reacting with a specific lysine or hydroxylysine in the triple helix. The divalent Schiff base and keto-amine bonds so formed link the molecules head to tail and spontaneously convert during maturation to trivalent cross-links, a histidine derivative and cyclic pyridinolines and pyrroles, respectively. These latter bonds are believed to be transverse inter-fibrillar cross-links, and are tissue rather than species specific. We describe the determination of these cross-links in detail.Elastin is also stabilised by cross-linking based on oxidative deamination of most of its lysine residues to yield tetravalent cross-links, desmosine and iso-desmosine, the determination of which is also described.A second cross-linking pathway occurs during ageing (and to a greater extent in diabetes mellitus) involving reaction with tissue glucose. The initial product glucitol-lysine can be determined as furosine and pyridosine, and determination of advanced glycation end-products believed to be cross-links, such as pentosidine, are also described.

Effect of inhibition of matrix metalloproteinases on cartilage loss in vitro and in a guinea pig model of osteoarthritis

OBJECTIVE

To study the effects of a matrix metalloproteinase (MMP) inhibitor (S-34219) on osteoarthritis (OA) cartilage cultures and in the meniscectomized guinea pig model of OA.

METHODS

The inhibitory activity of S-34219 on MMPs and aggrecanase was studied by fluorimetry and immunoassay, respectively. The effects of S-34219 on proteoglycan and collagen degradation were studied in cultures of rabbit and human cartilage. Medial meniscectomy was performed on 29 Hartley male guinea pigs, and these animals were randomly allocated to 1 of 3 groups: a control meniscectomized group (MNXc) receiving the vehicle, or a meniscectomized group receiving either 10 mg/kg or 20 mg/kg S-34219, administered twice per day by oral gavage for 12 weeks from day 1 after surgery. An additional group comprised sham-operated animals. Tibial cartilage from the operated left knee was processed for histologic assessment of OA lesions.

RESULTS

The 50% inhibitory concentration (IC(50)) of S-34219 on MMPs 1, 2, 3, 8, 9, and 13 was 55, 0.1, 0.5, 0.1, 0.03, and 0.2 nM, respectively; the IC(50) on aggrecanase 1 was 190 nM. In cultured rabbit cartilage, 100 nM S-34219 strongly inhibited MMP-dependent degradation of collagen and proteoglycans. A concentration 100 times higher was needed to inhibit aggrecanase-dependent degradation. In cultures of human OA cartilage, 100 nM S-34219 inhibited spontaneous type II collagen degradation by 66% and proteoglycan degradation by only 22%. For in vivo studies, treated groups were compared with the MNXc group and the results, expressed as the percentage variation versus MNXc, were as follows: in the 10 and 20 mg/kg groups, a significant decrease (P < 0.05) in global histologic score (-12% and -14%, respectively) was observed, and this was associated with a significant increase (P < 0.05) in cartilage thickness (+19% and +18%, respectively). Neither dose level changed the proteoglycan content.

CONCLUSION

In both treated animal groups, S-34219 significantly prevented the loss of cartilage thickness, probably by inhibiting collagen breakdown that normally leads to the erosion of fibrillated superficial areas. The absence of a protective effect on glycosaminoglycan loss, both in vitro and in vivo, suggests that aggrecanases may have an important role in cartilage loss. This study reinforces the relevance of these models for testing chondroprotective drugs, and the potential role of dual inhibitors of collagenase and aggrecanase as disease-modifying drugs in the management of OA.

Lactate and oxygen constitute a fundamental regulatory mechanism in wound healing

For many years, lactate has been known to accelerate collagen deposition in cultured fibroblasts and, without detailed explanation, has been presumed to stimulate angiogenesis. Similarly, hypoxia has been linked to angiogenic effects and collagen deposition from cultured cells. Paradoxically, however, wound angiogenesis and collagen deposition are increased by breathing oxygen and decreased by hypoxia. Lactate accumulates to 4-12 mM in wounds for several reasons, only one of which is the result of hypoxia. Oxygen in wounds is usually low but can be increased by breathing oxygen (without change in lactate). We have reported that lactate elicits vascular endothelial growth factor (VECF) from macrophages, as well as collagen, some heat shock proteins, and VECF from endothelial cells, and collagen from fibroblasts, even in the presence of normal amounts of oxygen. Hypoxia exerts many of these same effects in cultured cells. In this study, we elevated extracellular lactate in wounds by implanting purified solid-state, hydrolysable polyglycolide. A steady-state 2-3 mM additional elevation of lactate resulted. With it, there was a significant short-term elevation of interleukin-1beta, a long-term elevation of VECF (2x) and transforming growth factor-beta1 (2-3x), a 50% elevation in collagen deposition, and a large reduction of insulin-like growth factor-1 (- 90%). We propose that lactate induces a biochemical "perception" of hypoxia and instigates several signals that activate growth factor/cytokine signals while the continued presence of molecular oxygen allows endothelial cells and fibroblasts to reproduce and deposit collagen. The data are consistent with ADP-ribosylation effects and oxidant signaling. (WOUND REP REG 2003;11:504-509)

The role of the alpha2 chain in the stabilization of the collagen type I heterotrimer: a study of the type I homotrimer in oim mouse tissues

We have previously reported that the fragility of skin, tendon and bone from the oim mouse is related to a significant reduction in the intermolecular cross-linking. The oim mutation is unlikely to affect the efficacy of the lysyl oxidase, suggesting that the defect is in the molecule and fibre. We have therefore investigated the integrity of both the oim collagen molecules and the fibre by differential scanning calorimetry. The denaturation temperature of the oim molecule in solution and the fibre from tail tendon were found to be higher than the wild-type by 2.6deg.C and 1.9deg.C, respectively. With the loss of the alpha2 chain, the hydroxyproline content of the homotrimer is higher than the heterotrimer, which may account for the increase. There is a small decrease in the enthalpy of the oim fibres but it is not significant, suggesting that the amount of disorder of the triple-helical molecules and of the fibres is small and involves only a small part of the total bond energy holding the helical structure together. The difference in denaturation temperature of the skin collagen molecules (t(m)) and fibres (t(d)) is significantly lower for the oim tissues, 19.9deg.C against 23.1deg.C, indicating reduced molecular interactions and hence packing of the molecules in the fibre. Computation of the volume fraction of the water revealed that the interaxial separation of the oim fibres was indeed greater, increasing from 19.6A to 21.0A. This difference of 1.4A, equivalent to a C-C bond, would certainly decrease the ability of the telopeptide aldehyde to interact with the epsilon -amino group from an adjacent molecule and form a cross-link. We suggest, therefore, that the reduction of the cross-linking is due to increased water content of the fibre rather than a distortion of the molecular structure. The higher hydrophobicity of the alpha2 chain appears to play a role in the stabilisation of heterotrimeric type I collagen, possibly by increasing the hydrophobic interactions between the heterotrimeric molecules, thereby reducing the water content and increasing the binding of the molecules in the fibre.

Phenotypic expression of osteoblast collagen in osteoarthritic bone: production of type I homotrimer

The metabolism and total amount of the collagen of subchondral bone are increased several fold in osteoathritic femurs compared with controls. We now report for the first time that the quality of the collagen is modified by the formation of type I homotrimer. The homotrimer fibre has been reported to possess a reduced mechanical strength and mineralisation in bone. The presence of the latter therefore accounts for narrower disorganised collagen fibres and decreased mineralisation, and a reduction in mechanical stability of the osteoarthritic femoral head. These changes in the subchondral bone are likely to be of considerable importance in the pathogenesis of osteoarthritis.

Identification of an intermediate state in the helix-coil degradation of collagen by ultraviolet light

Differential scanning calorimetry has revealed the presence of a new denaturation endotherm at 32 degrees C following UV irradiation of collagen, compared with 39 degrees C for the native triple helix. Kinetic analyses showed that the new peak was a previously unknown intermediate state in the collagen helix-coil transition induced by UV light, and at least 80% of the total collagen was transformed to random chains via this state. Its rate of formation was increased by hydrogen peroxide and inhibited by free radical scavengers. SDS-polyacrylamide gels showed evidence of competing reactions of cross-linking and random primary chain scission. The cross-linking was evident from initial gelling of the collagen solution, but there was no evidence for a dityrosine cross-link. Primary chain scission was confirmed by end group analysis using fluorescamine. Electron microscopy showed that the segment long spacing crystallites formed from the intermediate state were identical to the native molecules. Clearly, collagen can undergo quite extensive damage by cleavage of peptide bonds without disorganizing the triple helical structure. This leads to the formation of a damaged intermediate state prior to degradation of the molecules to short random chains.

Isinglass/collagen: denaturation and functionality

Isinglass is widely used commercially to clarify alcoholic beverages by aggregation of the yeast and other insoluble particles. It is derived from swim bladders of tropical fish by solubilisation in organic acids and consists predominantly of the protein collagen. The low content of intermolecular cross-links allows ready dissolution of swim bladder compared to bovine hide which is cross-linked by a high proportion of stable bonds and requires enzymic digestion to solubilise. Isinglass is no longer effective as a clarifying agent if thermally denatured hence the collagenous triple helical structure must be maintained. Thermal denaturation of isinglass occurs at 29 degrees C, compared to 40-41 degrees C for mammalian collagens, primarily due to the lower hydroxyproline content. The hydroxyproline is essential for the formation of H-bonded water-bridges through the hydroxyl group and the peptide chain thereby stabilising the triple helix. Based on the lower enthalpy determined by differential scanning calorimetry we have calculated that the thermally labile domain of the isinglass molecule was 41 residues compared to 66 for mammalian collagen. The fining efficiency was unaffected by pH, chelating agents, detergents and removal of surface proteins from yeast cells. Studies on the mechanism of action of isinglass have shown that higher molecular weight aggregates that increase the length of the collagen molecules (trimers, tetramers, etc.) increase efficiency and that their surface charge are important in the clarification process. By chemical modification, we have shown that blocking positively charged groups had no effect on the fining process, whilst negative charges are clearly essential and that increasing the negative charge by succinylation increases its efficacy. Solutions of bovine hide collagen were shown to be equally effective in refining beers and standard yeast preparations. The higher thermal denaturation temperature, ready availability and reproducibility of bovine collagen preparations gives it considerable advantages over isinglass.

Effects of partial bladder outlet obstruction and its relief on types I and III collagen and detrusor contractility in the rat

Bladder outlet obstruction induces a rapid hypertrophy characterized by increased bladder mass and collagen deposition. An increase in collagen is likely to reduce the contractility and compliance of bladder wall. This study was undertaken to investigate the effects of partial bladder outlet obstruction and its relief on types I and III collagen, and the relationship between detrusor contractility and collagen types. A total of 40 female rats was used for experiment and divided into one control, one obstruction, and three recovery groups. The contractility to field stimulation was recorded; total collagen and collagen concentration were quantified. The localization of types I and III collagen and the expression of pro-alpha1(I) and alpha1(III) collagen mRNA were determined by immunohistochemical staining and Northern blot hybridization, respectively. Contractile response to field stimulation was reduced after obstruction and recovered following relief. The total amount of collagen increased after obstruction and decreased after relief; however, collagen concentration decreased after obstruction and increased following relief. Contractility correlated negatively with total collagen but positively with collagen concentration. The protein deposition of types I and III collagen was localized in lamina propria and muscle bundles in all groups. The expression of types I and III collagen gene was up regulated after obstruction, but down regulated after relief. Negative correlation between contractility and gene expressions of collagen types was significant. These data suggest that the change in localization and quantity of collagen types leads to morphologic changes of bladder and can have an impact on the contractility of detrusor. Neurourol. Urodynam. 19:29-42, 2000.

Collagen remodeling in the anterior cruciate ligament associated with developing spontaneous murine osteoarthritis

The initiating factors in primary, idiopathic osteoarthritis are unknown, the characteristic bone and cartilage changes being late features of the disease. We have proposed that biochemical cruciate ligament alteration may be important in early osteoarthritis by mediating loading consequences on the bone and cartilage. Using the widely accepted STR/ORT mouse model of spontaneous osteoarthritis we have found biochemical evidence that, before radiological signs of osteoarthritis develop, cruciate ligament collagen metabolism is upregulated in the STR/ORT mouse when compared to controls. Also, importantly, at this time the anterior cruciate ligament is weaker in STR/ORT mice than in controls. This is the first biochemical evidence to show that alterations in cruciate ligament metabolism occur early in the etiopathogenesis of idiopathic, primary osteoarthritis.

Long-term fructose consumption accelerates glycation and several age-related variables in male rats

Fructose intake has increased steadily during the past two decades. Fructose, like other reducing sugars, can react with proteins through the Maillard reaction (glycation), which may account for several complications of diabetes mellitus and accelerating aging. In this study, we evaluated the effect of fructose intake on some age-related variables. Rats were fed for 1 y a commercial nonpurified diet, and had free access to water or 250 g/L solutions of fructose, glucose or sucrose. Early glycation products were evaluated by blood glycated hemoglobin and fructosamine concentrations. Lipid peroxidation was estimated by urine thiobarbituric reactive substances. Skin collagen crosslinking was evaluated by solubilization in natural salt or diluted acetic acid solutions, and by the ratio between beta- and alpha-collagen chains. Advanced glycation end products were evaluated by collagen-linked fluorescence in bones. The ratio between type-III and type-I collagens served as an aging variable and was measured in denatured skin collagen. The tested sugars had no effect on plasma glucose concentrations. Blood fructose, cholesterol, fructosamine and glycated hemoglobin levels, and urine lipid peroxidation products were significantly higher in fructose-fed rats compared with the other sugar-fed and control rats. Acid-soluble collagen and the type-III to type-I ratio were significantly lower, whereas insoluble collagen, the beta to alpha ratio and collagen-bound fluorescence at 335/385 nm (excitation/emission) were significantly higher in fructose-fed rats than in the other groups. The data suggest that long-term fructose consumption induces adverse effects on aging; further studies are required to clarify the precise role of fructose in the aging process.

Differences between the thermal stabilities of the three triple-helical domains of type IX collagen

Fibre-forming collagens in dilute solution show highly co-operative helix-coil transitions at temperatures that are remarkably close to the body temperature of the animal from which the collagen was extracted. This close correlation holds across animal Phyla and the transition temperatures, which range from 5 degrees C to 40 degrees C, are adjusted to suit by changing the primary structure, especially the concentration of the water-bridge-enhancing hydroxyproline residue. Fibril-forming collagens are thermally stabilised by fibrillogenesis, which causes a loss of random coil configurational entropy by intermolecular and intramolecular cross-linking and by spacial confinement of the molecule within the lattice of the fibre. But this mechanism cannot apply to the full length of the type IX collagen molecule, since its COL3 arm, according to current models, projects out from the stabilising influence of the type II fibre. In this paper we examine the thermal stability of the type IX collagen molecule and its three triple-helical domains, thereby demonstrating that the COL3 arm is much more stable than the rest of the molecule. At a scanning rate of 60 deg. C/h COL3 exhibited an unfolding endotherm with a tmax at 49.0 degrees C, well above body temperature. Corresponding peak maxima for COL1 and COL2 were seen at 40.6 degrees C and 39.6 degrees C, respectively. The sizes of the thermally labile units of COL1, COL2 and COL3, calculated from the measured activation enthalpies, were 24, 28 and 28 residues, respectively, much smaller than type I (65 residues) because of the relatively short lengths of triple helix to be unfolded. However, unlike type I collagen, no regions of the required size were found completely devoid of hydroxyproline. Consequently, the intrinsic stabilities of these thermally labile units were higher than that of type I with DeltaH updownarrow DeltaS updownarrow for COL1, COL2 and COL3 being, respectively, 385 K, 371 K and 384 K, contrasting with the much lower 349 K of type I collagen. We therefore speculate that the increased thermal stability of the thermally labile units was caused by the presence of the water-bridge-enhancing residue, hydroxyproline. Finally the stabilisation of type IX collagen tissue is considered and an alternative structural organisation of the type IX molecule on the type II fibre is proposed.

Mice lacking the thrombin receptor, PAR1, have normal skin wound healing

Thrombin's actions on platelets, macrophages, fibroblasts, and endothelial cells have prompted the hypothesis that thrombin may be important for inflammatory and fibroproliferative processes in wound healing. Protease-activated receptor 1 (PAR1) is a G-protein-coupled receptor that mediates many of the cellular activities of thrombin. To test the role of this receptor in vivo, we generated PAR1-deficient mice. Despite the observation that fibroblasts cultured from these mice lacked responsiveness to thrombin in vitro, we now report that there was no difference detected between wild-type and PAR1-deficient mice in skin wound healing assays including time to closure of open wounds, tensile strength of healed incisional wounds, wound histology, and hydroxyproline/DNA content of wound implants. We conclude that PAR1 is not necessary for normal skin wound healing in mice.

Collagen content is significantly lower in restenotic versus nonrestenotic vessels after balloon angioplasty in the atherosclerotic rabbit model

BACKGROUND

It is recognized that restenosis is primarily due to alterations in geometric remodeling of the extracellular matrix rather than intimal hyperplasia. Prior studies have shown that angioplasty stimulates an increase in both synthesis and degradation of collagen in the atherosclerotic vessel. However, differences in collagen content and metabolism between restenotic and nonrestenotic vessels have not been examined.

METHODS AND RESULTS

Four weeks after angioplasty in an atherosclerotic rabbit model, collagen content in restenotic and nonrestenotic vessels was measured both biochemically by hydroxyproline quantitation and histologically by a digital subtraction method with the use of circularly polarized images of picrosirius red-stained sections. Collagenase and gelatinase activity also were measured in the same restenotic and nonrestenotic vessels by use of a radiosubstrate assay. Collagen content was found to be significantly lower in restenotic vessels than in nonrestenotic vessels both biochemically (127.0 +/- 32.6 versus 212.6 +/- 84.3 micrograms/mg tissue; n = 11 vessels; P < .05) and histologically (67.3 +/- 7.9% versus 76.3 +/- 11.8% area fraction; n = 20 sections from 6 vessels; P = .05). There was a significant inverse correlation between biochemically determined collagen content and gelatinase activity (P = .02) and a significant correlation between histologically determined lumen are and percent collagen content (P = .0071).

CONCLUSIONS

Collagen content is significantly decreased in restenotic versus nonrestenotic vessels after angioplasty in the atherosclerotic rabbit model. The increased collagen content in nonrestenotic vessels was associated with preserved lumen area and may play a role in geometric remodeling after angioplasty.

Does the thickness of the vertebral subchondral bone reflect the composition of the intervertebral disc?

Degeneration of the intervertebral disc, seen radiologically as loss of disc height, is often associated with apparent remodelling in the adjacent vertebral body. In contrast, maintenance or apparent increase in disc height is a common finding in osteoporosis, suggesting the properties of the intervertebral disc may be dependent on those of the vertebral body or vice versa. We have investigated this relationship by measuring the radiological thickness of the subchondral bone and comparing it to the chemical composition of the adjacent disc. Sagittal slabs were sampled from lumbar spines obtained at autopsy and X-rayed microfocally. The thickness of the subchondral bone was measured and correlated with the composition of the adjacent intervertebral disc. Eighty-three cadaveric endplates were studied from individuals aged 17-85 years. There was regional variation in thickness of the subchondral bone, being greater adjacent to the annulus than the nucleus, and the endplates cranial to the disc were thicker than those caudal. There was a positive correlation between the thickness of the subchondral bone and the proteoglycan content of the adjacent disc, particularly in the region of the nucleus. A weaker correlation was seen here between water content and thickness, whilst there was no significant correlation at the annulus or between the bone thickness and collagen content. The positive relationship between the radiographic thickness of vertebral subchondral bone and the proteoglycan content of the adjacent disc seen in human cadaveric material could be due to the bone responding to a greater hydrostatic pressure being exerted by discs with higher proteoglycan content than by those with less proteoglycan present. It is suggested that while this is true in "normal" specimens, the relationship becomes altered in disease states, possibly because of changes to the nutritional pathway of the disc, with resultant endplate-bone remodelling affecting the flow of solutes to and from the intervertebral disc.

Transport properties of the human cartilage endplate in relation to its composition and calcification

STUDY DESIGN

The transport properties of solutes of different sizes and conformations were studied in cartilage endplates.

OBJECTIVES

The results were correlated with the composition of the cartilage matrix to determine if a relationship existed between this and the movement of molecules within it.

SUMMARY OF BACKGROUND DATA

Solute transport through the hyaline cartilage endplate is important not only for the physiologic and metabolic processes of that tissue, but also for those of the adjacent intervertebral disc. Movement of solutes depends on solute size, shape or charges, and the composition of the matrix itself. Changes in composition of the cartilage endplate, such as those that occur in degeneration or scoliosis, may affect transport.

METHODS

Partition and diffusion coefficients of solutes ranging in molecular weight from 115 to 70,000 d have been measured on cores of cartilage endplate. Transport properties were assessed in relation to core composition.

RESULTS

The shape and size of the solutes were found to affect their transport through cartilage matrix, with larger molecules being more highly excluded and diffusing more slowly. Long-chain polymers were able to penetrate the matrix less readily than the more globular molecules. The more hydrated the matrix, the higher the degree of penetration and the more easily solutes could move, in contrast to the inverse relationship between the other components of the matrix and solute transport. With increased proteoglycan, collagen, or calcification in the tissue, there was greater restriction of solute movement.

CONCLUSIONS

The proteoglycans normally found in the endplate regulate movement of solutes into and out of the disc. It has been shown previously that removal of proteoglycans from the endplate accelerates the loss of proteoglycans from the nucleus. Hence, a major function of the cartilage endplate may be to prevent fragments of osmotically active proteoglycans from leaving the disc.

Pulmonary toxicity of nickel subsulfide in F344/N rats exposed for 1-22 days

Repeated inhalation of nickel subsulfide (Ni3S2) by F344/N rats for 3 months results in chronic active inflammation in the lung and atrophy of the olfactory epithelium. The primary purpose of this study was to determine early responses of the respiratory tract to inhaled Ni3S2 in rats and to track the course of development of such lesions in rats exposed for up to 22 days. A secondary purpose was to obtain an improved estimate of the half-time for clearance of Ni from Ni3S2-exposed lungs. Groups of F344/N rats were exposed to 0, 0.6 or 2.5 mg Ni3S2/m3, 6 h/day for 1-22 days. Histopathological changes in nose and lung, as well as biochemical and cytological changes in lung, as measured in bronchoalveolar lavage fluid (BALF) and lung tissue, alveolar macrophage (AM) viability and Ni concentration in lung were evaluated. Inflammatory lung lesions in rats exposed to 2.5 mg Ni3S2/m3 peaked in intensity after 4 days of exposure. Minimal degeneration of the olfactory epithelium was noted in the 2.5 mg Ni3S2/m3-exposed rats after day 4 of exposure, with atrophy of the olfactory epithelium occurring in rats killed at 22 days. Lactate dehydrogenase, beta-glucuronidase and total protein in BALF were significantly elevated within 7 days of exposure while alkaline phosphatase activity was significantly depressed. AM viability was significantly reduced after 2 days of exposure. Concentrations of Ni in lung increased rapidly during the first 7 days of exposure, but more slowly thereafter. Lung burden data from this and a previous study suggest a clearance half-time for Ni of 3.5-8 days. Results indicate that Ni3S2 is relatively soluble in lung and inhalation of concentrations near the current Threshold Limit Value of 1 mg Ni/m3 can produce detrimental changes in the respiratory tract of rats after only a few days of exposure.

Transforming growth factor-beta 1 and mannose 6-phosphate/insulin-like growth factor-II receptor expression during intrahepatic bile duct hyperplasia and biliary fibrosis in the rat

These studies investigate the role of transforming growth factor-beta 1, a potent inhibitor of epithelial cell proliferation and stimulator of extracellular matrix biosynthesis, during intrahepatic bile duct hyperplasia and biliary fibrosis. These pathogenic responses were induced in rats by common bile duct ligation. Bile duct cell replication, measured by the bromodeoxyuridine labeling index, was significantly increased 24 hr after common bile duct ligation. This response diminished to baseline by 1 wk. Liver collagen content, determined by quantification of hydroxyproline, was increased significantly after 1 wk of common bile duct ligation, and by 4 wk was increased by a factor of 4. Immunohistochemistry revealed low levels of TGF-beta 1 in normal intrahepatic bile duct epithelium. In contrast, the bile duct epithelium in bile duct-ligated rats stained strongly positive for transforming growth factor-beta 1 at 1 and 4 wk after ligation. These results suggest that transforming growth factor-beta 1 may play a role in both the termination of the bile duct epithelial cell proliferative response and the induction of fibrogenesis after common bile duct ligation. In addition, the mannose 6-phosphate/insulin-like growth factor II receptor was up-regulated in hyperplastic bile duct epithelium 1 and 4 wk after ligation. Because the mannose 6-phosphate/insulin-like growth factor-II receptor has been shown to facilitate the proteolytic activation of transforming growth factor-beta 1, these results suggest that the bile duct epithelium may also be involved in the activation of transforming growth factor-beta 1.

Changes in markers of bone formation and resorption in a bed rest model of weightlessness

To study the mechanism of bone loss in physical unloading, we examined indices of bone formation and bone resorption in the serum and urine of eight healthy men during a 7 day -6 degrees head-down tilt bed rest. Prompt increases in markers of resorption--pyridinoline (PD), deoxypyridinoline (DPD), and hydroxyproline (Hyp)/g creatinine--during the first few days of inactivity were paralleled by tartrate-resistant acid phosphatase (TRAP) with significant increases in all these markers by day 4 of bed rest. An index of formation, skeletal alkaline phosphatase (SALP), did not change during bed rest and showed a moderate 15% increase 1 week after reambulation. In contrast to SALP, serum osteocalcin (OC) began increasing the day preceding the increase in Hyp, remained elevated for the duration of the bed rest, and returned to pre-bed rest values within 5 days of reambulation. Similarly, DPD increased significantly at the onset of bed rest, remained elevated for the duration of bed rest, and returned to pre-bed rest levels upon reambulation. On the other hand, the other three indices of resorption, Hyp, PD, and TRAP, remained elevated for 2 weeks after reambulation. The most sensitive indices of the levels of physical activity proved to be the noncollagenous protein, OC, and the collagen crosslinker, DPD. The bed rest values of both these markers were significantly elevated compared to both the pre-bed rest values and the post-bed rest values. The sequence of changes in the circulating markers of bone metabolism indicated that increases in serum OC are the earliest responses of bone to head-down tilt bed rest.

The effects of phonophoresis with corticosteroids: a controlled pilot study

Although physical therapists and physicians often treat patients with local musculoskeletal inflammation using topically applied steroids enhanced with ultrasound, there is a paucity of research confirming that phonophoresis significantly enhances drug diffusion. The purpose of this study was to determine if ultrasound enhances the diffusion of transdermally applied corticosteroids. Diffusion was measured secondarily in terms of collagen deposition [estimated by levels of hydroxyproline in polytetrafluroethylene (ePTFE) tubing] and cellular activity (measured by levels of DNA). Sixteen pieces of ePTFE tubing were subcutaneously implanted on the dorsum of five mini Yucatan pigs. Pairs of tubing were randomly assigned to sham control or treatment groups. Over the paired ePTFE tubes in the treatment groups, a single transdermal application of hydrocortisone acetate (HC) or dexamethasone (DX) was applied to the skin by rubbing, sonating with the drug mixed in the acoustic gel (1.5 W/cm2, 1 MHz, 5 minutes), or injecting the drug into the tubing. Four additional ePTFE tubes were threaded in the extremities, two submuscularly and two subtendinously, with random assignment to a sham control or a DX sonation treatment group. At the end of a week, the mean hydroxyproline levels in the swine were lower than expected (mean = 9.3 micrograms/cm compared to an expected mean = 22.2 micrograms/cm). Comparing the control and skin-applied groups with the injected and sonated treatment groups, the hydroxyproline was found to be 50% lower in the DX-injected, DX-sonated, and HC-injected sites. However, statistically there were no significant differences in DNA or hydroxyproline levels between the HC subcutaneous control and treatment groups or the DX submuscular and subtendinous groups. There was a significant main effect of group on hydroxyproline levels in the group of DX-treated, subcutaneously implanted ePTFE tubes (p = 0.001). Post hoc testing revealed a significant difference between the skin-rubbed and control groups together compared to the DX-injected and DX-sonated groups together (p = 0.001). These findings indicate that the effects of phonophoresed DX can be measured in terms of reduced collagen deposition as far down as the subcutaneous tissue but not in the submuscular or subtendinous tissue. However, a single application may not have a measurable effect on cellular activity after 7 days of healing. The unusually low level of hydroxyproline across all groups suggests that phonophoresis with steroids may have had a systemic as well as a local effect.

The cartilage end-plate and intervertebral disc in scoliosis: calcification and other sequelae

The morphology and composition of the intervertebral disc and also of the cartilage end-plate were studied in patients with idiopathic or congenital scoliosis. The cartilage end-plate was investigated because of its function as an epiphyseal plate in humans and the association between growth and progression of the scoliotic curve. The proteoglycan and water contents were reduced in both structures in specimens from scoliotic patients, particularly toward the concavity of the curve, compared with autopsy material. The distribution of some collagen types differed in tissue from scoliotic patients and autopsy tissue. Calcification of the cartilage end-plate, and sometimes of the adjacent disc, occurred in all but three scoliotic patients, whereas there was minimal calcification in the autopsy specimens. We suggest that, although these changes are probably a secondary response to altered loading in the scoliotic patients, they may be highly significant to the progression of the scoliotic curve.

Tamoxifen reduces bone turnover and prevents lumbar spine and proximal femoral bone loss in early postmenopausal women

Although widely used for its anti-estrogen properties tamoxifen has estrogen like effects on a number of tissues including bone and liver. Previous studies suggest a preservation of lumbar spine density in postmenopausal women but the effect on the hip had not been addressed. To determine whether tamoxifen prevents bone loss in the early postmenopausal period bone mineral density at the lumbar spine and femoral neck was measured using dual energy X-ray absorptiometry at presentation and 6 monthly thereafter for 1 year in a prospective controlled study. Also indices of bone turnover, serum osteocalcin and urinary hydroxyproline excretion, were assessed. Fifteen early postmenopausal women with Stage I or II breast cancer treated with tamoxifen and 21 normal postmenopausal women were studied. Sex hormone binding globulin and antithrombin III levels in serum were also measured as indices of the hepatic estrogenic activity. Tamoxifen (20 mg daily) prevented bone loss at the femoral neck and lumbar spine. Median rates of change in bone mineral density (%/year) for the tamoxifen group were +0.09%/year in the lumbar spine and 1.4%/year in the femoral neck compared with -2.3%/year and -1.8%/year for the control group (P = 0.04 and 0.03, respectively). Tamoxifen resulted in a significant decrease in both serum osteocalcin and urinary hydroxyproline by 6 months of treatment and this effect persisted for the 12 months of observation. An increase in sex hormone binding globulin and a decline in antithrombin III levels was also observed. These data indicate that, in recently, postmenopausal women tamoxifen prevented bone loss at both the lumbar spine and femur and reduced bone turnover.

Collagen crosslinks and mineral crystallinity in bone of patients with osteogenesis imperfecta

In cortical bone samples from patients with osteogenesis imperfecta (OI), the concentrations of hydroxypyridinium cross-linking amino acids in collagen were measured by reversed-phase HPLC and the x-axis crystallinity of the apatite mineral phase was determined by x-ray diffraction. Bone samples from three patients with type I, nine patients with type III, and eight patients with type IV OI were analyzed and compared with human bone from nine controls. The concentration of the two chemical forms of the mature collagen crosslinking amino acids, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), and the ratio HP/LP were found to be alike in bone collagen of OI patients and healthy controls. However, the c-axis crystallinity of the apatite was found to be reduced in the type III and IV OI patients compared with controls. Regression analysis of crosslink concentrations and c-axis crystallinity in OI bones did not show any correlation. Therefore, collagen molecules deposited in the extracellular matrix of OI bone appear to fulfill the structural requirements for the action of the enzyme lysyl oxidase, such that a normal concentration of intermolecular crosslinks is formed compared with healthy bone. Consequently, crosslink formation and apatite crystal growth seem to be regulated independently in OI bone.

Ovariectomy selectively reduces the concentration of transforming growth factor beta in rat bone: implications for estrogen deficiency-associated bone loss

Previous work showed that production of transforming growth factor beta (TGF-beta) by osteoblast-like rat UMR 106 cells was increased by 17 beta-estradiol at physiological concentrations. To determine whether ovariectomy alters the concentration of TGF-beta in rat long bones, female Sprague-Dawley rats were either sham-operated (n = 19) or ovariectomized (n = 19), pair-fed a semisynthetic diet for 6 weeks, and sacrificed. Tibial and femoral diaphyses were removed and extracted by demineralization. Ovariectomy lowered serum estrogen; did not alter body weight, serum magnesium, or serum 1,25-dihydroxyvitamin D; and produced only modest differences in serum calcium and phosphate concentrations. Hydroxyproline was higher and extractable protein was lower in bones from ovariectomized rats than in bones from sham-operated rats; calcium content did not differ between the two groups of animals. Ovariectomy lowered the concentration of TGF-beta in bone but did not change the concentration of insulin-like growth factors I or II compared with values in bone from control animals. The reduction of bone TGF-beta was evident 6 weeks after surgery but not at 3 weeks. Treatment of ovariectomized rats with estrogen eliminated the TGF-beta deficit. To determine whether 17 beta-estradiol increased TGF-beta production by normal bone cells, mouse osteoblasts were treated for 2 days with 17 beta-estradiol. The production of TGF-beta was increased almost 2-fold by 1 nM 17 beta-estradiol, and short-term treatment stimulated the intracellular accumulation of TGF-beta 1 mRNA. We conclude that ovariectomy reduces deposition of TGF-beta in rat bone and that diminished skeletal TGF-beta could play a role in the pathogenesis of bone loss, fractures, and microfractures that occur in estrogen-deficient states. Our results support the possibility that estrogen and bone TGF-beta may be necessary for normal maintenance of the skeleton in female rats.

Biologic effect of 1,24(R)(OH)2D3 versus 1,25(OH)2D3 administration in chronic renal failure

1,24(R)(OH)2D3 is a synthetic analogue of 1,25(OH)2D3 which binds to the same receptors as the physiologic metabolite with a lower affinity. The aim of the present study was to compare the activity of 1,24(R)(OH)2D3 and 1,25(OH)2D3 on several target organs in patients with chronic renal failure. Treatment with 1,24(R)(OH)2D3 at doses of either 1 or 2 micrograms daily was carried out in two groups of 9 patients, with serum creatinine of 4.61 +/- 1.59 and 4.66 +/- 1.46 mg/dl, respectively. Doses of 1,25(OH)2D3 were 0.5 and 1 microgram daily and were administered to 9 and 13 patients, serum creatinine of 4.52 +/- 1.67 and 4.3 +/- 1.16 mg/dl, respectively. Treatment periods were of 2 weeks. Administration of 1,25(OH)2D3, 1 microgram, induced significant increments of intestinal calcium absorption (ICA), ionized calcium, osteocalcin, serum creatinine, urine Ca/GFR, and a decrease in iPTH. 1,25(OH)2D3, 0.5 microgram, induced a significant increase in ICA and osteocalcin and a decrease in iPTH. Similarly 1,24(OH)2D3, 2 micrograms daily, significantly stimulated ICA and raised serum levels of osteocalcin and creatinine while lowering serum iPTH. In addition, 1,24(R)(OH)2D3 administration induced a significant fall of serum 1,25(OH)2D3. Following 1 microgram, only osteocalcin increased. Therefore, the dose of 2 micrograms of 1,24(R)(OH)2D3 has biologic activity similar to 0.5 microgram 1,25(OH)2D3 (4:1). However the activity ratio on osteocalcin production appears to be 2:1. In addition, 1,24(R)(OH)2D3 is able to inhibit renal tubular 1 alpha-hydroxylase. In conclusion 1,24(R)(OH)2D3 may prove to be useful in the treatment of metabolic bone disease.

Healing of ischemic colonic anastomosis: fibrin sealant does not improve wound healing

Fibrin adhesives have been advocated as a protective sealant in high-risk colonic anastomoses to prevent leakage. To assess the effect of fibrin glue sealing on the healing ischemic anastomosis, we compared the healing of sutured colonic anastomoses in the rat, with and without fibrin adhesive (Groups IA and IB), and ischemic anastomoses with and without fibrin adhesive (Groups IIA and IIB). On days two, four, and seven, 10 animals in each group were sacrificed. Adhesion formation was scored, and the in situ bursting pressure was measured. The collagen concentration and degradation were estimated by measuring hydroxyproline. Adhesion formation was more prominent in Groups IB, IIA, and IIB on day four only; abscesses were noted in the ischemic group in four rats. Anastomotic bursting pressure was significantly lower in sealed (IB) and ischemic anastomoses (IIA) than in normal anastomoses (IA) on day four. Sealing of ischemic anastomoses did not change bursting pressures on days two, four, and seven. The relative decrease of collagen in the sealed anastomoses is significantly higher on day four only. It is concluded that sealing of normal colonic anastomoses in the rat has a negative effect on wound healing. Ischemia at the anastomotic site results in weaker anastomotic strength on day four postoperatively. Also in ischemic anastomoses, fibrin sealant does not improve wound healing during the first seven days. Adhesion formation on ischemic intestinal anastomoses was not prevented by fibrin sealing.

Effect of antibiotics in fibrin sealant on healing colonic anastomoses in the rat

In 90 rats a colonic anastomosis was constructed with 12 interrupted 7/0 polypropylene sutures. Group 1 (n = 30) served as a control group. In group 2 (n = 30) the anastomosis was sealed with fibrin adhesive and in group 3 (n = 30) a mixture of fibrin, clindamycin and cefotaxime was used. On days 2, 4 and 7, ten animals in each group were killed. Adhesion formation was significantly increased in groups 2 and 3 compared with the control group. On day 2 the anastomosis was significantly stronger after sealing with antibiotic-fibrin mixture. On day 4 the bursting pressure in group 2 was significantly lower than in groups 1 and 3. At the same time the concentration of hydroxyproline was significantly reduced in group 2, but not in group 3. The addition of antibiotics prevents the negative effect of fibrin adhesive on the healing colonic anastomosis and contributes to a stronger anastomosis on day 2 after operation.

Short term effects of SHD 386L and levonorgestrel on bone and mineral metabolism in the postmenopause: a double-blind randomised placebo-controlled trial

Forty-five healthy postmenopausal women participated in a study designed to examine the effects on bone and mineral metabolism of SHD 386L, a new hormone replacement therapy (HRT) regime. This oral preparation delivers 2 mg estradiol valerate daily and 75 micrograms of levonorgestrel from days 17-28 inclusive of a 28-day cycle. The study was double-blind, randomized and placebo controlled. Patients who received SHD 386L exhibited significant falls in plasma calcium, ionised calcium, phosphate and total alkaline phosphatase. No alteration, however, was observed in plasma osteocalcin. No significant changes in mineral metabolism were observed in a parallel group receiving levonorgestrel alone. The results indicate that SHD 386L is likely to be protective to the skeleton through inhibition of bone resorption and that such actions are attributable to the estrogen component. The preparation was well tolerated, compliance was satisfactory and serious adverse affects were not seen. The above biochemical evidence for skeletal protection will require to be supplemented by prospective biophysical evidence of the effect of SHD 386L on bone mineral density.