Collagen and mineral deposition in rabbit cortical bone during maturation and growth: Effects on tissue properties

Abstract

ABSTRACT:We characterized the composition and mechanical properties of cortical bone during maturation and growth and in adult life in the rabbit. We hypothesized that the collagen network develops earlier than the mineralized matrix. Growth was monitored, and the rabbits were euthanized at birth (newborn), and at 1, 3, 6, 9, and 18 months of age. The collagen network was assessed biochemically (collagen content, enzymatic and non-enzymatic cross-links) in specimens from the mid-diaphysis of the tibia and femur and biomechanically (tensile testing) from decalcified whole tibia specimens. The mineralized matrix was analyzed using pQCT and 3-point bend tests from intact femur specimens. The collagen content and the Young's modulus of the collagen matrix increased significantly until the rabbits were 3 months old, and thereafter remained stable. The amount of HP and LP collagen cross-links increased continuously from newborn to 18 months of age, whereas PEN cross-links increased after 6 months of age. Bone mineral density and the Young's modulus of the mineralized bone increased until the rabbits were at least 6 months old. We concluded that substantial changes take place during the normal process of development in both the biochemical and biomechanical properties of rabbit cortical bone. In cortical bone, the collagen network reaches its mature composition and mechanical strength prior to the mineralized matrix. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J. Orthop. Res. 28: 1626Res. 28: -1633Res. 28: , 2010 Keywords: maturation; growth; aging; rabbit; bone; mechanical properties; composition Collagen is the principal structural component of bone matrix, accounting for about 1/3 of mineralized bone tissues. 1 During development, bone formation and growth rates are regulated by genetic and hormonal factors, and by external factors such as mechanical loading that interact to determine the final anatomy and strength of the skeleton. 1-3 During this period, bone also changes in its composition, structure, and function. The organic matrix changes its composition and structural organization, and mechanical stiffness increases with increased bone mineral density (BMD). 3,4 The majority (>80%) of the mineral can be found within the collagen fibril network, 5 but limited information is available about the factors that determine the normal deposition of mineral, for example, the timing and how this can determine the properties of the adult tissue.The structure and function of maturing and growing bone were studied in several animal models. 4,6,7 Most studies focused on bone development and growth in rabbits, investigating the development of the primary and secondary ossification centers or evaluating bone growth at the growth plate. [8][9][10] Other studies showed that BMD increases and biomechanical properties change concurrently during maturation and growth. 4,6 However, the development of the collagen framework has been less extensively studied. During development, at least in the equine, ...

Age‐related changes in organization and content of the collagen matrix in rabbit cortical bone

“…4 In the present study FTIR and PLM measurements were conducted on samples from animals used in the earlier study. 4 In the current study, BA from the earlier study were included for comparison with the new FTIR and PLM analyses.…”

“…Thereafter, the mid-diaphysis and adjacent parts of the bone were decalcified using EDTA. 4 The middle part of the bone, containing the fractured site, was cut and prepared for BA. The adjacent 5 mm-long fragment was embedded in paraffin, and used for FTIR and PLM measurements.…”

“…The complete methods and results were presented in our earlier study. 4 In the present study, those results were used only for comparison. Briefly, the middiaphyses adjacent to the breaking points were decalcified using EDTA.…”

“…[1][2][3] The molecular compositions of the organic and inorganic matrices in bone are known to alter during maturation, especially until the animal is skeletally mature. 4 In this study we distinguish between animal age and collagen age: Animal age is the time elapsed since birth, whereas collagen age relates to the time elapsed since osteonal bone formation. Since bone constantly remodels, the skeleton of mature animals contains both mature and immature bone.…”

Relative Fixation Strength of Rabbit Subscapularis Repair Is Comparable to Human Supraspinatus Repair at Time 0

“…The shoulders of 21 fresh-frozen cadaveric New Zealand White rabbits carcasses obtained from Western Oregon Rabbit Co (Philomoth, OR, USA) were used. The rabbits were approximately 6 months of age and were males ranging in size from 3.4 to 3.8 kg [26]. The shoulder was dissected free of all muscular, ligamentous, and tendinous structures other than those of the rotator cuff.…”