Effects of collagen unwinding and cleavage on the mechanical integrity of the collagen network in bone

Wang, X.<sup>1</sup>; Li, X.<sup>2</sup>; Bank, R. A.<sup>3</sup>; Agrawal, C. M.<sup>2</sup>

Affiliations

¹Mechanical Engineering and Biomechanics, The University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, Texas 78249, USA

²Department of Orthopaedics, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78249, USA

³Division of Vascular and Connective Tissue Research, TNO Prevention and Health, Leiden, The Netherlands, The Netherlands

Abstract and keywords

The objective of this study was to investigate how molecular level changes in the collagen network affect its mechanical integrity. Our hypothesis is that the cleavage and unwinding of triple helices of collagen molecules signi®cantly reduce the mechanical integrity of the collagen network in bone, whereas collagen crosslinks play a major role in sustaining the structural integrity of the collagen network. To test this hypothe- sis, the collagen molecular structure was altered in demineralized human cadaveric bone samples in the following two ways: heat induced unwinding and pan- creas elastase induced cleavage of collagen molecules. Along with control specimens, the treated specimens were mechanically tested in tension to determine their strength, elastic modulus, toughness, and strain to fail- ure. Also, the percentage of denatured collagen mole- cules and amounts of two major collagen crosslinks (hydroxylysylpyridinoline and lysylpyridinoline) were determined using high-performance liquid chromato- graphy techniques. It was found that unwinding of collagen molecules may cause more reduction in stiffness (E) but less strain to failure (ef) than cleavage. Both collagen denaturation types cause similar changes in the strength (rs) and work to fracture (Wf) of the collagen network with no signi®cant changes in hydroxylysyl- pyridinoline and lysylpyridinoline crosslinks. The results of this study indicate that the integrity of collagen molecules signi®cantly affect the mechanical properties of the collagen network in bone, and that collagen crosslinks may play an important role in maintaining the mechanical integrity of the collagen network after collagen denaturation occurs.

Keywords: Bone; Collagen; Denaturation; Tensile properties; Demineralized bone

Links

DOI: 10.1007/s00223-001-1082-2

PubMed: 12200651

WoS: 000177792100014

History

Received: 2001-07-17

Accepted: 2002-01-28

Online: 2002-08-01

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