histidinohydroxylysinonorleucine and pyridinoline

To determine the effects of percutaneous estradiol (E2) implants on the collagen composition and maturity in the bone and skin of osteoporotic postmenopausal women.. Sixteen postmenopausal women with low bone mineral density were treated for 1 year with 75-mg E2 implants. Iliac crest bone and skin biopsies were analyzed for collagen content and collagen cross-links before treatment and at 1 year. Dual energy x-ray absorptiometry of the lumbar spine and proximal femur was also performed before and after 1 year of therapy.. The cortical bone showed a significant increase in the mature cross-links of both hydroxylysylpyridinoline (P < .01) and lysylpyridinoline (P < .01), with a significant reduction in the percentage of collagen (P < .001). The pattern was similar in trabecular bone, with lysylpyridinoline increasing significantly (P < .05). The skin exhibited a significant reduction in the immature cross-link hydroxylysinonorleucine (P < .01), but no significant change in the percentage of collagen content or the mature cross-link histidinohydroxylysinonorleucine. The median increases in bone density were 11.5% at the spine and 4.34% at the total hip. The median post-treatment serum E2 level was 639 pmol/L.. Bone mineral density increased at all the sites measured in the spine and proximal hip. The quality of the collagen within the transiliac biopsies had matured in that the concentration of the mature collagen cross-links had increased. These findings support a reduction in the turnover of bone collagen following estrogen replacement therapy. More important, the formation of a more mature collagen fiber should help to reduce the risk of future bone fracture.

Topics: Absorptiometry, Photon; Administration, Cutaneous; Aged; Amino Acids; Bone and Bones; Bone Density; Collagen; Dipeptides; Estradiol; Estrogen Replacement Therapy; Female; Histidine; Humans; Osteoporosis, Postmenopausal; Skin; Time Factors

While it is well established that the composition and organisation of articular cartilage dramatically change during skeletal maturation, relatively little is known about how this impacts the mechanical properties of the tissue. In this study, digital image correlation was first used to quantify spatial deformation within mechanically compressed skeletally immature (4 and 8 week old) and mature (1 and 3 year old) porcine articular cartilage. The compressive modulus of the immature tissue was relatively homogeneous, while the stiffness of mature articular cartilage dramatically increased with depth from the articular surface. Other, well documented, biomechanical characteristics of the tissue also emerged with skeletal maturity, such as strain-softening and a depth-dependent Poisson's ratio. The most significant changes that occurred with age were in the deep zone of the tissue, where an order of magnitude increase in compressive modulus (from 0.97 MPa to 9.4 MPa for low applied strains) was observed from 4 weeks postnatal to skeletal maturity. These temporal increases in compressive stiffness occurred despite a decrease in tissue sulphated glycosaminoglycan content, but were accompanied by increases in tissue collagen content. Furthermore, helium ion microscopy revealed dramatic changes in collagen fibril alignment through the depth of the tissue with skeletal maturity, as well as a fivefold increase in fibril diameter with age. Finally, computational modelling was used to demonstrate how both collagen network reorganisation and collagen stiffening play a key role in determining the final compressive mechanical properties of the tissue. Together these findings provide a unique insight into evolving structure-function relations in articular cartilage.

Topics: Age Factors; Algorithms; Amino Acids; Animals; Biomechanical Phenomena; Cartilage, Articular; Collagen; Compressive Strength; Cross-Linking Reagents; Dipeptides; Elastic Modulus; Glycosaminoglycans; Helium; Histidine; Microscopy; Microscopy, Polarization; Models, Biological; Swine; Time Factors

In an attempt to identify potential staging markers of effective healing, changes in connective tissue properties were measured in a human skin excisional wound healing model in which tissue was re-excised at intervals up to 6 months after injury. The proportion of collagen III relative to collagen I increased significantly (p<0.001) up to 6 weeks after initial injury and remained elevated up to 6 months, at which time the proportion of collagen III was 70% above baseline values. Extractability of biopsy tissue collagen by pepsin increased significantly throughout the study (baseline, 32.8+/-6.8%; 6 months, 89.1+/-8.9%), with inverse changes in the mature skin cross-link, histidinohydroxylysinonorleucine (baseline, 1.18+/-0.11 mol/mol collagen; 6 months, 0.27+/-0.09 mol/mol collagen). Pyridinoline content increased over the period of the study, although remaining at relatively low concentrations (baseline, 0.037+/-0.011; 6 months, 0.063+/-0.014 mol/mol collagen), and the pyridinoline/deoxypyridinoline ratio was significantly higher (baseline, 3.5+/-0.6; 6 months, 10.3+/-2.2). Elastin content, measured as desmosine cross-links, decreased significantly in the first 3 weeks and continued to decline over the period of study. Overall, the data suggest that remodeling of the wound tissue continues at least up to 6 months after injury. The close inverse correlation between histidinohydroxylysinonorleucine concentrations and extractability by pepsin (r2=0.89, p<0.0001) suggests a causal relationship, consistent with the likely effects of a substantial network of mature, inter-helical bonds in collagen.

Topics: Adult; Amino Acids; Collagen; Collagen Type I; Collagen Type III; Dipeptides; Elastin; Histidine; Humans; Male; Skin; Time Factors; Wound Healing; Wounds, Penetrating

Keloid is a tissue with an excessive accumulation of collagen. In this study, we have partially characterized post-translational modifications of type I collagen in human keloid in order to pursue their potential involvement in this pathology. The levels of lysyl hydroxylation of the helical portions of alpha 1 and alpha 2 chains of type I collagen in keloid were significantly higher than those of normal, while the levels of prolyl hydroxylation were identical between these two groups. The contents of the major reducible cross-links in dermal collagen, dehydro-hydroxylysinonorleucine and dehydro-histidinohydroxymero-desmosine, were both significantly higher in keloids (up to sixfold) than those of normal. In addition, significant amounts of hydroxylysine-aldehyde derived cross-links that are characteristic of skeletal tissue collagens, dehydro-dihydroxylysinonorleucine (about 0.3 mole/mole of collagen) and pyridinoline (about 0.1 mole/mole of collagen), were found in keloids. These results indicate that keloid-forming cells are phenotypically different from those in normal dermis and that the collagen produced is highly cross-linked. The increased cross-linking provides the fibrils with more stability that may result in an accumulation of collagen.

Topics: Adult; Amino Acids; Collagen; Cross-Linking Reagents; Desmosine; Dipeptides; Histidine; Humans; Hydroxylation; Hydroxylysine; Hydroxyproline; Keloid; Middle Aged; Protein Processing, Post-Translational; Protein Structure, Secondary; Skin

A high-performance liquid chromatographic-fluorescence detection method of reducible (immature) and nonreducible (mature and senescent) cross-links of collagen was established without the use of a radioisotope and preliminary fractionation step. This method used a gradient elution procedure of sodium citrate buffer containing 7% ethanol. The reducible cross-links (dihydroxylysinonorleucine, hydroxylysinonorleucine, and lysinonorleucine) and nonreducible cross-link (histidinohydroxylysinonorleucine) were detected by O-phthalaldehyde derivatization with the postcolumn method, whereas other nonreducible cross-links (pyridinoline, deoxypyridinoline, and pentosidine) were detected by natural fluorescence. The linear ranges of contents of the O-phthalaldehyde derivative cross-links and the natural fluorescent nonreducible cross-links were 20-600, 5-500 (pyridinoline, deoxypyridinoline), and 0.2-20 pmol (pentosidine), respectively. Tissue containing 1-2 mg dry wt of collagen was adequate for duplicate analyses of the reducible and nonreducible cross-links. An equivalent of 0.25 mg of hydrolyzed collagen could be analyzed by this HPLC system. Using this system, age-related changes in the cross-links of collagen from human connective tissues were also investigated.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Amino Acids; Arginine; Cartilage, Articular; Child; Child, Preschool; Chromatography, High Pressure Liquid; Collagen; Cross-Linking Reagents; Diaphyses; Dipeptides; Femur; Histidine; Humans; Indicators and Reagents; Infant; Lysine; Male; Middle Aged; Sensitivity and Specificity; Skin; Spectrometry, Fluorescence